bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphatidylcholine hydroperoxide levels in human plasma are lower than previously reported
Authors: Adachi Junko , Yoshioka Naoki , Funae Rika , Nagasaki Yasushi , Naito Takaeki , Ueno Yasuhiro
Published: November 2006

The quantification of PC hydroperoxide (PCOOH) in human plasma was studied by HPLC with chemiluminescence detection (HPLC‐CL). We identified for the first time the monohydroperoxide of 1‐palmitoyl‐2‐linoleoyl‐PC hydroperoxide (PC 16∶0/18∶2‐OOH) in plasma by LC‐MS and HPLC‐CL. The standard compound, PC 16∶0/18∶2‐OOH (synthetic PCOOH), as well as PCOOH from egg yolk, was used. Comparison of the PCOOH concentration in each participant's plasma as determined by use of a Finepak SIL NH2 column with 2‐propanol/methanol/water as the mobile phase (system A, the conventional method) gave a higher concentration than did an LC‐18‐DB column with methanol containing 0.01% triethylamine (system B). The mean PCOOH concentration for the 43 healthy volunteers was 55.1±30.4 pmol/mL (mean±SD) for system A and 16.3±9.9 pmol/mL for system B. Moreover, the main peak of the plasma extract appeared at a different time from that of synthetic PCOOH or egg yolk PCOOH in system A, whereas in system B plasma sample retention time practically corresponded to that of standard PCOOH. These findings confirm that the PCOOH plasma concentration is not so high as previously reported.
Umbelliferone aminoalkyl derivatives as inhibitors of oxidosqualene cyclases from Saccharomyces cerevisiae, Tripanosoma cruzi, and Pneumocystis carinii
Authors: Oliaro‐Bosso Simonetta , Viola Franca , Matsuda Seiichi , Cravotto Giancarlo , Tagliapietra Silvia , Balliano Gianni
Published: November 2006

A series of umbelliferone aminoalkyl derivatives, previously studied as inhibitors of squalene‐hopene cyclase, were tested as inhibitors of yeast (Saccharomyces cerevisiae) oxidosqualene cyclase (OSC) and OSC from Trypanosoma cruzi and Pneumocystis carinii expressed in yeast. Enzymes from these pathogens were included in this study to provide a preliminary screening for antiparasitic activity. Tests were carried out both on cell homogenates incubated with radiolabeled oxidosqualene and on spheroplasts incubated with radiolabeled acetate. Derivatives bearing a methylallylamino group were the most effective on all of the three enzymes. The P. carinii enzyme was the most susceptible to the action of the inhibitors, with IC50 values for almost all of them ranging from 0.1 to 1μM. The T. cruzi enzyme was appreciably inhibited (IC50 4–5 μM) only by derivatives bearing a methylallylaminoalkyl flexible chain. Results identify a particularly promising new family of OSC inhibitors, for the development of novel antiparasitic agents.
A new glucoceramide from the watermelon begonia, Pellionia repens
Authors: Luo Yinggang , Liu Yan , Qi Huayi , Zhang Guolin
Published: November 2006

A new glucoceramide named pellioniareside (1) was isolated from the aqueous ethanolic extract of whole plants of Pellionia repens, together with lupeol (2), uracil (3), (22E,20S,24R)‐5α,8α‐epidioxyergosta‐6,22‐dien‐3‐β‐ol (4), and daucosterol (5). The structure and relative configurations of pellioniareside were identified as (2S,3S,4R,6E,8E)‐1‐O‐β‐d‐glucopyranosyl‐2‐[(2R)‐2‐hydroxytetracosanoylamino]‐1,3,4‐octadecanetriol‐6,8‐diene by analysis of spectral data and by chemical evidence.
Immunomodulation by polyunsaturated fatty acids: Impact on T‐cell signaling
Authors: Stulnig Thomas M. , Zeyda Maximilian
Published: November 2006

In recent years the potential application of the immunomodulatory effects of polyunsaturated FA (PUFA), particularly those of the n−3 series, in a variety of inflammatory disorders has been of considerable interest. However, the mechanisms underlying inhibition of T‐cell activation have so far been unclear. In this short review we summarize possible mechanisms for the modulation of immune responses by PUFA. Effects of PUFA on T‐cell signal transduction pathways and underlying molecular mechanisms are described in detail. These recent results add considerably to the understanding of mechanisms of PUFA actions, but their relevance in the in vivo situation must still be elucidated.
KLF6 degradation after apoptotic DNA damage
Authors: Banck Michaela S. , Beaven Simon W. , Narla Goutham , Walsh Martin J. , Friedman Scott L. , Beutler Andreas S.
Published: November 2006

Krüppel‐like factor 6 (KLF6) is a cancer gene (www.sanger.ac.uk/genetics/CGP/Census/). Here, we demonstrate that KLF6 protein is rapidly degraded when apoptosis is induced via the intrinsic pathway by cisplatin, adriamycin, or UVB irradiation in multiple cell lines (HCT116, SW40, HepG2, PC3‐M, Skov3, NIH‐3T3, 293T, GM09706, and MEF, IMR‐90). KLF6 degradation occurred in the presence or absence of p53, was associated with ubiquitination, mediated by the proteasome (half‐life 16 min, unstimulated), and independent of caspases and calpain. KLF6 was unchanged by apoptosis via the extrinsic/death‐receptor pathway. Deregulation of KLF6 stability may alter its tumor suppressor function and/or the response of tumors to chemotherapeutics.
COMBATING TRANSNATIONAL CRIME IN AFRICA: PROBLEMS AND PERSPECTIVES
Authors: HATCHARD JOHN
Published: November 2006

Transnational crime is a major problem for African states with corruption, trafficking of persons, drugs trafficking, environmental crime and the like posing a major threat to development and stability. This article examines three challenges that states must tackle in order to combat transnational crime effectively. The first is how to deal with criminals who operate outside the jurisdiction. The second concerns the investigation of crimes with a transnational element. The third challenge involves tracing and then recovering the proceeds of crime that have been moved out of the country where the crime occurred. Here the need for Western states to cooperate with those in Africa is highlighted. Drawing on examples from Lesotho and Nigeria in particular, it is argued that some progress is being made in meeting these challenges. However, the article notes that developing the political will to tackle transnational crime is fundamental to any lasting improvement.
(MIS)USING BANK SHARE CAPITAL AS A REGULATORY TOOL TO FORCE BANK CONSOLIDATIONS IN NIGERIA
Authors: OGOWEWO TUNDE I. , UCHE CHIBUIKE
Published: November 2006

This paper is a critique of the policy-making process and the particular policy choice made by the Central Bank of Nigeria with respect to the recent increase in the minimum share capital requirement for Nigerian banks. The article questions the apparent prioritization by the Central Bank of banking supervision – important though it is – over macro-economic stability. It also draws attention to serious public law issues (breach of monetary law and abuse of power) and the private law implications (conflicts of interests, scheme of arrangement defects, and negligent valuations) of this policy-making episode and policy choice.
The effects, in sheep, of dietary plant species and animal live weight on the faecal recovery rates of alkanes and the accuracy of intake and diet composition estimates obtained using alkanes as faecal markers
Authors: LIN L.-J , LUO H.-L. , ZHANG Y.-J. , SHU B.
Published: November 2006

Alkanes can be used as natural markers for estimating diet composition, but a factor should be used to correct for incomplete recovery in faeces. Faecal alkane recovery rates may be influenced by diet and animal factors. However, little research has been conducted to evaluate the effects of herbage species and live weight of animals on faecal alkane recoveries. In the current study, faecal recoveries of alkanes were determined in sheep in four different live weight groups (from 20 to 40 kg) fed three plant species (Elymus sibiricum, Leymus chinensis and L. dasystachys). In a second experiment, the accuracy of intake and diet composition estimates, using alkanes as faecal markers, was assessed by feeding known amounts of the same plant species as a three-component mixture. The results showed that faecal alkane recoveries were influenced significantly by herbage species (P<0·01), but no effect of live weight of animals was observed. Total dry matter intake was estimated correctly based on either C31:C32 or C29:C32 alkane pairs. With respect to estimators of E. sibiricum intake, reasonable results could only be obtained if the faecal alkane concentration was corrected based on diet-specific faecal recovery. More accurate estimations were obtained only if the alkanes found in relatively higher concentrations were used in diet composition estimates instead of using all available alkanes. Due to lower alkane concentrations or similar alkane patterns of L. chinensis and L. dasystachys in the diet, estimates of diet composition of these two herbage species were significantly different from the actual ones (P<0·05), implying that other markers need to be used for accurate estimation.
Myringoplasty: a comparison of bismuth iodoform paraffin paste gauze pack and tri-adcortyl ointment ear dressing
Authors: Nakhla V , Takwoingi Y M , Sinha A
Published: November 2006

Objectives: To assess the myringoplasty graft take rate, comparing two methods of post-operative ear packing: bismuth iodoform paraffin paste (BIPP) gauze versus tri-adcortyl ointment (TAO).

Methods: A retrospective study of patients who had undergone myringoplasty at our department within a three-year period was undertaken. Data, including age, site and size of perforation, grade of surgeon, surgical approach, use of post-operative ear dressings, complications, and audiometric outcome, were collected from the patient notes and analysed. The overall success rate of the operation (with success being defined as an intact tympanic membrane at six months) was noted.

Results: One hundred and seventy myringoplasties were performed over the study period, but data were complete on 154 patients and these constituted the study population. Age ranged from nine to 71 years (mean age 34 years) and the mean follow-up period was seven months. Consultants performed 62 per cent of the operations, with an 85 per cent success rate, whereas trainees performed the remaining 38 per cent, with a success rate of 73 per cent (p=0.059). The overall success rate was 80 per cent; 79 per cent for BIPP and 83 per cent for TAO (p=0.55), and 87 per cent for small perforations and 75 per cent for subtotal perforations (p=0.22). There was audiometric improvement in 74 per cent of cases.

Conclusion: We found no significant difference in outcome between patients packed with TAO and BIPP. Packing with TAO is therefore a suitable alternative to BIPP gauze ear dressing following myringoplasty.
Quantified vegetation change over 42 years at Cape Hallett, East Antarctica
Authors: Brabyn L. , Beard C. , Seppelt R.D. , Rudolph E.D. , Türk R. , Green T.G.A.
Published: November 2006

This paper reports on the remapping of a carefully documented vegetation plot at Cape Hallett (72°19′S 170°16′E) to provide an assessment of the rates of vegetation change over decadal time scales. E.D. Rudolph, in 1962, mapped in detail the vegetation of a site approximately 28 m by 120 m at Cape Hallett, Victoria Land, Antarctica. This site was relocated and remapped in January 2004 and changes were assessed using GIS techniques. This appears to be the longest available time period for assessing vegetation change in Antarctica. The analysis indicated that considerable change had occurred in moss and algae distribution patterns and this seems to have been caused by increased water supply, particularly in wetter areas. There was also evidence of some change in lichen distribution. The extent of the change indicates that vegetation cover can be used for monitoring change in areas as extreme as the Ross Sea region. For this analysis to be successful it was important that the mapping techniques used were totally explicit and could easily be replicated. Fortunately, Rudolph had defined his cover classes and the site was also clearly marked. The application of GIS mapping techniques allows the mapping to be more explicitly defined and easily replicated.
The meroplankton community of the northern Ross Sea: a preliminary comparison with the McMurdo Sound region
Authors: Sewell Mary A.
Published: November 2006

As part of the Latitudinal Gradient Project (LGP) the coastal meroplankton community is being studied along the coast of Victoria Land, in the Ross Sea, Antarctica. In this preliminary analysis the meroplankton community from Cape Hallett (72°S) is compared to that from two previously sampled sites in the south-western Ross Sea; at Cape Roberts and in McMurdo Sound (c. 77°S). Non-metric multi-dimensional scaling (MDS), a hierarchical cluster analysis and permutational MANOVA in combination show that the meroplankton composition differs significantly between the three sites. Although this preliminary analysis includes only one northern Ross Sea site, the results suggest that there are differences in meroplankton composition along the Victoria Land coast. Several larval types, including annelid trochophores, unidentified annelid larva, echinospira, barnacle nauplius, asteroid, echinoid, and ophiuroid larvae were absent or rare in the south-western Ross Sea but found abundantly at Cape Hallett. Detailed analysis of the meroplankton community at Cape Hallett and further examination of changes in the meroplankton community along the Victoria Land coast will continue in future years of the LGP.
The ~3.4 billion-year-old Strelley Pool Sandstone: a new window into early life on Earth
Authors: Wacey David , McLoughlin Nicola , R. Green Owen , Parnell John , Stoakes Crispin A. , Brasier Martin D.
Published: November 2006

The recognition and understanding of the early fossil record on Earth is vital to the success of missions searching for life on other planets. Despite this, the evidence for life on Earth before ~3.0 Ga remains controversial. The discovery of new windows of preservation in the rock record more than 3.0 Ga would therefore be helpful to enhance our understanding of the context for the earliest life on Earth. Here we report one such discovery, a ~3.4 Ga sandstone at the base of the Strelley Pool Formation from the Pilbara of Western Australia, in which micrometre-sized tubular structures preserve putative evidence of biogenicity. Detailed geological mapping and petrography reveals the depositional and early diagenetic history of the host sandstone. We demonstrate that the depositional environment was conducive to life and that sandstone clasts containing putative biological structures can be protected from later metamorphic events, preserving earlier biological signals. We conclude from this that sandstones have an exciting taphonomic potential both on early Earth and beyond.
Effects of Composition, Solvent, and Salt Particles on the Physicochemical Properties of Polyglycolide/Poly(lactide‐co‐glycolide) Scaffolds
Authors: Kuo Yung‐Chih , Leou Sho‐Noen
Published: November 2006

Polyglycolide (PGA)/poly(lactide‐co‐glycolide) (PLGA) scaffolds were fabricated by a solvent casting/particulate leaching method using hexafluoroisopropanol (HFIP) or acetone for material dissolution and NaCl particles as porogen. The results revealed that the mechanical strength increased as the PGA percentage in a HFIP‐processed scaffold increased. Chemical ingredients did not substantially affect the mechanical strength of acetone‐processed scaffolds. Large NaCl particles led to weak mechanical strength, low porosity, and small specific surface area. For a fixed composition, PGA crystals in a HFIP‐processed scaffold were smaller than those in an acetone‐processed scaffold. High PGA fractions yielded partly fused PGA/PLGA scaffolds. A faster degradation rate of a scaffold could result from a higher PGA percentage, smaller NaCl particles, or the existence of chondrocytes. The combination of PGA and PLGA, which compensated each other for bioactivity, would be beneficial to cartilage regeneration.
Kinetic and Thermodynamic Investigation on Ascorbate Oxidase Activity and Stability of a Cucurbita maxima Extract
Authors: Porto Tatiana S. , Porto Camila S. , Cavalcanti Maria T. H. , Filho José L. Lima , Perego Patrizia , Porto Ana L. F. , Converti Attilio , Pessoa Adalberto
Published: November 2006

The kinetic and thermodynamic properties of ascorbate oxidase (AO) activity and stability of a Cucurbita maxima extract were investigated. Activity tests performed at 25 °C using initial ascorbic acid concentration in the range 50–750 μM allowed estimating the Michaelis constant for this substrate (Km = 126 μM) and the maximum initial rate of ascorbic acid oxidation (A0,max = 1.57 mM min−1). The main thermodynamic parameters of the enzyme reaction (ΔH* = 10.3 kJ mol−1; ΔG* = 87.2 kJ mol−1; ΔS* = –258 J mol−1 K−1) were estimated through activity tests performed at 25–48 °C. Within such a temperature range, no decrease in the initial reaction rate was detected. The long‐term thermostability of the raw extract was then investigated by means of residual activity tests carried out at 10–70 °C, which allowed estimating the thermodynamic parameters of the irreversible enzyme inactivation as well (ΔH*D = 51.7 kJ mol−1; ΔG*D = 103 kJ mol−1; ΔS*D = –160 J mol−1 K−1). Taking into account the specific rate of AO inactivation determined at different temperatures, we also estimated the enzyme half‐life (1047 min at 10 °C and 21.2 min at 70 °C) and predicted the integral activity of a continuous system using this enzyme preparation. This work should be considered as a preliminary attempt to characterize the AO activity of a C. maxima extract before its concentration by liquid‐liquid extraction techniques.
Marine crenarchaeotal membrane lipids in decapods: Implications for the TEX86 paleothermometer
Authors: Huguet Carme , Cartes Joan E. , Sinninghe Damsté Jaap S. , Schouten Stefan
Published: November 2006

Pelagic Crenarchaeota produce glycerol dibiphytanyl glycerol tetraethers (GDGTs) as membrane lipids, and the GDGT composition changes according to growth temperature. This forms the basis of the TEX86 paleotemperature proxy. This ratio correlates with sea surface temperature (SST) despite the fact that Crenarchaeota are distributed through the water column. Therefore there must be mechanisms that transport the surface signal to sediments such as repackaging in fecal pellets, marine snow, mass falls after phytoplankton blooms, or daily migration. To study GDGT transport, we analyzed stomachs and intestines of Atlantic and Mediterranean decapods as they are one of the major megafaunal groups, are easy to sample, and occur in both pelagic and benthic environments. GDGTs were found in most decapods' guts. GDGT abundances are significantly lower in intestines, but TEX86‐derived temperatures are not significantly different between stomachs and intestines (<1°C), suggesting that TEX86 values are not altered during gut transit. Atlantic decapods show no difference in TEX86 values between benthic detritivors and pelagic predators. However, Mediterranean decapods show a substantial difference between macroplankton feeders and bentho‐pelagic predators. This is probably related to the freshness of the material consumed. TEX86‐derived temperatures in Atlantic decapods are close to the SST around the time of sampling, in agreement with stomach content analysis that shows fresh organic matter being ingested. For Mediterranean decapods, TEX86 temperatures are significantly higher than SST around the time of sampling. This can be partly attributed to the large variability between decapod specimens and the low amounts of fresh material found in their stomachs.
Ovine plasma prion protein levels show genotypic variation detected by C-terminal epitopes not exposed in cell-surface PrPC
Authors: Thackray Alana M. , Fitzmaurice Tim J. , Hopkins Lee , Bujdoso Raymond
Published: November 2006

Ovine PBMCs (peripheral blood mononuclear cells) express PrPC [cellular PrP (prion-related protein)] and have the potential to harbour and release disease-associated forms of PrP during scrapie in sheep. Cell-surface PrPC expression by PBMCs, together with plasma PrPC levels, may contribute to the regulatory mechanisms that determine susceptibility and resistance to natural scrapie in sheep. Here, we have correlated cell-surface PrPC expression on normal ovine PBMCs by FACS with the presence of PrPC in plasma measured by capture–detector immunoassay. FACS showed similar levels of cell-surface PrPC on homozygous ARR (Ala136-Arg154-Arg171), ARQ (Ala136-Arg154-Gln171) and VRQ (Val136-Arg154-Gln171) PBMCs. Cell-surface ovine PrPC showed modulation of N-terminal epitopes, which was more evident on homozygous ARR cells. Ovine plasma PrPC levels showed genotypic variation and the protein displayed C-terminal epitopes not available in cell-surface PrPC. Homozygous VRQ sheep showed the highest plasma PrPC level and homozygous ARR animals the lowest. For comparison, similar analyses were performed on normal bovine PBMCs and plasma. PrPC levels in bovine plasma were approx. 4-fold higher than ovine homozygous ARQ plasma despite similar levels of PBMC cell-surface PrPC expression. Immunoassays using C-terminal-specific anti-PrP monoclonal antibodies as capture and detector reagents revealed the highest level of PrPC in both ovine and bovine plasma, whilst lower levels were detected using N-terminal-specific monoclonal antibody FH11 as the capture reagent. This suggested that a proportion of plasma PrPC was N-terminally truncated. Our results indicate that the increased susceptibility to natural scrapie displayed by homozygous VRQ sheep correlates with a higher level of plasma PrPC.
Trypanothione-dependent glyoxalase I in Trypanosoma cruzi
Authors: Greig Neil , Wyllie Susan , Vickers Tim J. , Fairlamb Alan H.
Published: November 2006

The glyoxalase system, comprizing glyoxalase I and glyoxalase II, is a ubiquitous pathway that detoxifies highly reactive aldehydes, such as methylglyoxal, using glutathione as a cofactor. Recent studies of Leishmania major glyoxalase I and Trypanosoma brucei glyoxalase II have revealed a unique dependence upon the trypanosomatid thiol trypanothione as a cofactor. This difference suggests that the trypanothione-dependent glyoxalase system may be an attractive target for rational drug design against the trypanosomatid parasites. Here we describe the cloning, expression and kinetic characterization of glyoxalase I from Trypanosoma cruzi. Like L. major glyoxalase I, recombinant T. cruzi glyoxalase I showed a preference for nickel as its metal cofactor. In contrast with the L. major enzyme, T. cruzi glyoxalase I was far less fast-idious in its choice of metal cofactor efficiently utilizing cobalt, manganese and zinc. T. cruzi glyoxalase I isomerized hemithio-acetal adducts of trypanothione more than 2400 times more efficiently than glutathione adducts, with the methylglyoxal adducts 2–3-fold better substrates than the equivalent phenylglyoxal adducts. However, glutathionylspermidine hemithioacetal adducts were most efficiently isomerized and the glutathionylspermidine-based inhibitor S-4-bromobenzylglutathionylspermidine was found to be a potent linear competitive inhibitor of the T. cruzi enzyme with a Ki of 5.4±0.6 μM. Prediction algorithms, combined with subcellular fractionation, suggest that T. cruzi glyoxalase I localizes not only to the cytosol but also the mitochondria of T. cruzi epimastigotes. The contrasting substrate specificities of human and trypanosomatid glyoxalase enzymes, confirmed in the present study, suggest that the glyoxalase system may be an attractive target for anti-trypanosomal chemotherapy.
Propagating torsion in the Einstein frame
Authors: Popławski Nikodem J.
Published: November 2006

The Einstein–Cartan–Saa theory of torsion modifies the spacetime volume element so that it is compatible with the connection. The condition of connection compatibility gives constraints on torsion, which are also necessary for the consistence of torsion, minimal coupling, and electromagnetic gauge invariance. To solve the problem of positivity of energy associated with the torsionic scalar, we reformulate this theory in the Einstein conformal frame. In the presence of the electromagnetic field, we obtain the Hojman–Rosenbaum–Ryan–Shepley theory of propagating torsion with a different factor in the torsionic kinetic term.
Photoconductance and photoresponse of layer compound photodetectors in the UV-visible region
Authors: Ho Ching-Hwa , Hsieh Ming-Hung , Wu Ching-Cherng
Published: November 2006

In this study, a number of photoconductive photodetectors made from GaSe1−xSx (0⩽x⩽1) series layered semiconductors are presented, which are suitable for the detection of energies in the range of visible to ultraviolet (UV). Each photodetector consists of a gallium chalcogenide photoconductor and an electronic amplifier, forming an optical sensor unit covering the energy spectrum range from red (2eV) to UV (∼5eV). Spectral photoconductances of the GaSe1−xSx series layers with x=0, 0.1, 0.2, 0.3, 0.4, and 1 are characterized using photoconductivity measurements in the energy range of 2–4eV, and the results of these measurements are analyzed. Photoluminescence and piezoreflectance measurements are carried out to identify the band-edge transitions of the layered GaSe1−xSx (0⩽x⩽1) compounds. From experimental analysis the transition origins of the band-edge transitions are clarified. The functional performance of three selective sensor units of GaSe, GaS, and two-color GaS∕GaSe is tested using the spectral measurements of a xenon arc lamp. The emission line features from the xenon arc lamp are clearly resolved in the detection spectra of the sensor units. The results show a good functional performance of these layer compound photodetectors.
Femtosecond time-resolved fluorescence up-conversion spectrometer corrected for wavelength-dependent conversion efficiency using continuous white light
Authors: Murakami Hiroshi
Published: November 2006

We have developed a fluorescence up-conversion spectrometer which allows us to observe femtosecond time-resolved fluorescence spectra directly and correctly. The spectral response of the spectrometer including wavelength-dependent up-conversion efficiency is acquired through up-conversion of a spectrally calibrated continuous white light. On the other hand, wavelength-dependent mismatch of the time origin is determined as wavelength-dependent change of the peak position of the temporal instrumental response function derived from deconvolution with the wavelength-resolved fluorescence decay curve of a sample. Comparison between the time-resolved fluorescence spectrum thus obtained for the sample and that reconstructed from the fluorescence decay curves measured at a set of wavelengths at the same delay time has been made in order to confirm the validity of the correction procedures.
Role of the Si∕SiO2 interface during dopant diffusion in thin silicon on insulator layers
Authors: Mannino Giovanni , La Magna Antonino , Privitera Vittorio , Giubertoni Damiano , Bersani Massimo
Published: November 2006

We found that As and B diffusion in 90nm thick Si on SiO2, silicon on insulator, samples is reduced, by ∼20%, with respect to that of bulk Si for thermal processing in a lamp-based system. In contrast, when annealing is performed in a hot-wall furnace system and sample heating is determined by conduction diffusion length in Si–SiO2–Si samples is very similar to that occurring in bulk-Si reference samples. We demonstrate that diffusion in Si–SiO2–Si multilayer structures is primarily determined by an increased sample reflectivity, generated by the presence of the buried Si∕SiO2 interface that reduces the amount of heat absorbed by the sample, rather than by the enhanced recombination of point defects at this interface. The latter phenomenon is not ruled out but plays a less relevant role in determining the measured reduction of diffusion.
Mechanism analysis of periodicity and weakening surge of GaAs photoconductive semiconductor switches
Authors: Shi Wei , Tian Liqiang
Published: November 2006

The authors analyze the periodicity and weakening surge of semi-insulating GaAs photoconductive semiconductor switches. It is shown that the periodicity and weakening surge of the output current wave form is caused by the self-excitation of the circuit. The electric field threshold ET and the sustaining electric field Es (the minimum electric field required to support the domain) are modulated by the ac electric field; the output wave form becomes two main modes of transelectron oscillator, namely, delayed domain mode and quenched domain mode.
An improved collision efficiency model for particle aggregation
Authors: Olsen Aaron , Franks George , Biggs Simon , Jameson Graeme J.
Published: November 2006

A generalized geometric model is presented which describes the collision efficiency factor of aggregation (the probability of a binary particle or aggregate collision resulting in adhesion) for systems comprised of two oppositely charged species. Application of the general model to specific systems requires calculation of the area of each species available for collision with a second species. This is in contrast to previous models developed for polymer-particle flocculation that are based on the fractional surface coverage of adsorbed polymer. The difference between these approaches is suggested as an explanation for previously observed discrepancies between theory and observation. In the current work the specific case of oppositely charged nondeformable spherical particles (heteroaggregation) is quantitatively addressed. The optimum concentration of oppositely charged particles for rapid aggregation (maximum collision efficiency) as a function of relative particle size is calculated and an excellent correlation is found with data taken from literature.
Dissociative ionization of ethanol by 400nm femtosecond laser pulses
Authors: Yazawa H. , Shioyama T. , Suda Y. , Kannari F. , Itakura R. , Yamanouchi K.
Published: November 2006

The dissociative ionization of ethanol in short-pulsed laser fields at ∼400nm is investigated. The yield ratio of the C–O bond breaking with respect to the C–C bond breaking increases sharply as the temporal width increases from 60to400fs, and the yield ratio is two to three times as large as that at 800nm in the entire pulse-width range of 60–580fs. The enhancement of the C–O bond breaking of singly charged ethanol at 400nm and the bond elongation prior to the Coulomb explosion of doubly charged ethanol occurring in the relatively weak light field intensity of 1012–1013W∕cm2 is interpreted by the efficient light-induced coupling among the electronic states at the shorter wavelength of 400nm. From the double pulse experiment, in which ethanol is irradiated with a pair of short pulses (<80fs), the most efficient coupling occurs at Δt=160fs that is much earlier than Δt=250 at 800nm, where Δt denotes the temporal separation of the two pulses, indicating that the nonadiabatic field-induced potential crossings of singly charged ethanol occurs much earlier at 400nm than at 800nm.
Enhanced piezoresistive characteristics of Nb2O5 modified La0.8Sr0.2MnO3 ceramics
Authors: Sharma Vaneet , Hossu Maria R. , Lee Woo Ho , Koymen Ali R. , Priya Shashank
Published: November 2006

This letter reports the giant piezoresistance phenomenon in Nb2O5 modified La0.8Sr0.2MnO3 (LSMO) polycrystalline ceramics. LSMO modified with 2mol% Nb exhibited ∼2% change in resistivity at 19.2MPa pressure as compared to 0.5% for the pure LSMO. A dramatic improvement was obtained for 5mol% Nb-modified LSMO composition, which exhibited a linear change in resistivity with uniaxial stress and the fractional change was of the order of 3% at 19.2MPa stress. The origin of the giant piezoresistance was found to be related to Nb substitution on the Mn sites which distorts the Mn–O bond, lowering the magnitude of stress required for the manganite lattice transformation.
Energy-band alignments at LaAlO3 and Ge interfaces
Authors: Mi Y. Y. , Wang S. J. , Chai J. W. , Pan J. S. , Huan A. C. H. , Ning M. , Ong C. K.
Published: November 2006

The energy-band alignments for LaAlO3 films on p-Ge(001) with and without GeOxNy interfacial layer have been studied using photoemission spectroscopy. The valence-band offsets at LaAlO3∕GeOxNy∕Ge and LaAlO3∕Ge interfaces were measured to be 2.70 and 3.06eV, respectively. The effect of interfacial GeOxNy layer on the band alignments is attributed to the modification of interface dipoles. The conduction-band offsets at LaAlO3∕Si(001) and LaAlO3∕Ge interfaces are found to have the same value of 2.25±0.05eV, where the shift of valence-band top accounts for the difference in the energy-band alignment at two interfaces.
InGaAs quantum dot molecules around self-assembled GaAs nanomound templates
Authors: Lee J. H. , Wang Zh. M. , Strom N. W. , Mazur Yu. I. , Salamo G. J.
Published: November 2006

Several distinctive self-assembled InGaAs quantum dot molecules (QDMs) are studied. The QDMs self-assemble around nanoscale-sized GaAs moundlike templates fabricated by droplet homoepitaxy. Depending on the specific InAs monolayer coverage, the number of QDs per GaAs mound ranges from two to six (bi-QDMs to hexa-QDMs). The Ga contribution from the mounds is analyzed in determining the morphologies of the QDMs, with respect to the InAs coverages ranging between 0.8 and 2.4 ML. Optical characterization shows that the resulting nanostructures are high-quality nanocrystals.
Electrostatic and structural properties of GaN nanorods/nanowires from first principles
Authors: Tsai M.-H. , Jhang Z.-F. , Jiang J.-Y. , Tang Y.-H. , Tu L. W.
Published: November 2006

The first-principles calculation has revealed that the GaN nanorod has a greatly enhanced dipole moment per area relative to that of a film, which in conjunction with the geometry effect suggests that the top surface of the nanorod has a greater electrostatic attraction for gas-phase Ga and N source species than the film surface during epitaxial growth of GaN. The first-principles molecular-dynamics calculation shows that the average Ga–N bond length of the GaN nanowire decreases with the decrease of the diameter of the nanowire, which demonstrates a surface tension effect.
Modern proteomes contain putative imprints of ancient shifts in trace metal geochemistry
Authors: Dupont Christopher L. , Yang Song , Palenik Brian , Bourne Philip E.
Published: November 2006

Because of the rise in atmospheric oxygen 2.3 billion years ago (Gya) and the subsequent changes in oceanic redox state over the last 2.3–1 Gya, trace metal bioavailability in marine environments has changed dramatically. Although theorized to have influenced the biological usage of metals leaving discernable genomic signals, a thorough and quantitative test of this hypothesis has been lacking. Using structural bioinformatics and whole-genome sequences, the Fe-, Zn-, Mn-, and Co-binding metallomes of 23 Archaea, 233 Bacteria, and 57 Eukarya were constructed. These metallomes reveal that the overall abundances of these metal-binding structures scale to proteome size as power laws with a unique set of slopes for each Superkingdom of Life. The differences in the power describing the abundances of Fe-, Mn-, Zn-, and Co-binding proteins in the proteomes of Prokaryotes and Eukaryotes are similar to the theorized changes in the abundances of these metals after the oxygenation of oceanic deep waters. This phenomenon suggests that Prokarya and Eukarya evolved in anoxic and oxic environments, respectively, a hypothesis further supported by structures and functions of Fe-binding proteins in each Superkingdom. Also observed is a proliferation in the diversity of Zn-binding protein structures involved in protein–DNA and protein–protein interactions within Eukarya, an event unlikely to occur in either an anoxic or euxinic environment where Zn concentrations would be vanishingly low. We hypothesize that these conserved trends are proteomic imprints of changes in trace metal bioavailability in the ancient ocean that highlight a major evolutionary shift in biological trace metal usage.
Germ-line epigenetic modification of the murine

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vy

allele by nutritional supplementation
Authors: Cropley Jennifer E. , Suter Catherine M. , Beckman Kenneth B. , Martin David I. K.
Published: November 2006

Environmental effects on phenotype can be mediated by epigenetic modifications. The epigenetic state of the murine

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vy

allele is highly variable, and determines phenotypic effects that vary in a mosaic spectrum that can be shifted by
in utero
exposure to methyl donor supplementation. We have asked if methyl donor supplementation affects the germ-line epigenetic state of the

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vy

allele. We find that the somatic epigenetic state of

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vy

is affected by
in utero
methyl donor supplementation only when the allele is paternally contributed. Exposure to methyl donor supplementation during midgestation shifts

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vy

phenotypes not only in the mice exposed as fetuses, but in their offspring. This finding indicates that methyl donors can change the epigenetic state of the

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vy

allele in the germ line, and that the altered state is retained through the epigenetic resetting that takes place in gametogenesis and embryogenesis. Thus a mother's diet may have an enduring influence on succeeding generations, independent of later changes in diet. Although other reports have suggested such heritable epigenetic changes, this study demonstrates that a specific mammalian gene can be subjected to germ-line epigenetic change.
Pleiotrophin disrupts calcium-dependent homophilic cell–cell adhesion and initiates an epithelial–mesenchymal transition
Authors: Perez-Pinera P. , Alcantara S. , Dimitrov T. , Vega J. A. , Deuel T. F.
Published: November 2006

Regulation of the levels of tyrosine phosphorylation is essential to maintain the functions of proteins in different signaling pathways and other cellular systems, but how the steady-state levels of tyrosine phosphorylation are coordinated in different cellular systems to initiate complex cellular functions remains a formidable challenge. The receptor protein tyrosine phosphatase (RPTP)β/ζ is a transmembrane tyrosine phosphatase whose substrates include proteins important in intracellular and transmembrane protein-signaling pathways, cytoskeletal structure, cell–cell adhesion, endocytosis, and chromatin remodeling. Pleiotrophin (PTN the protein and
Ptn
the gene) is a ligand for RPTPβ/ζ; PTN inactivates RPTPβ/ζ, leaving unchecked the continued endogenous activity of tyrosine kinases that increase phosphorylation of the substrates of RPTPβ/ζ at sites dephosphorylated by RPTPβ/ζ in cells not stimulated by PTN. Thus, through the regulation of the tyrosine phosphatase activity of RPTPβ/ζ, the PTN/RPTPβ/ζ signaling pathway coordinately regulates the levels of tyrosine phosphorylation of proteins in many cellular systems. We now demonstrate that PTN disrupts cytoskeletal protein complexes, ablates calcium-dependent homophilic cell–cell adhesion, stimulates ubiquitination and degradation of N-cadherin, reorganizes the actin cytoskeleton, and induces a morphological epithelial–mesenchymal transition (EMT) in PTN-stimulated U373 cells. The data suggest that increased tyrosine phosphorylation of the different substrates of RPTPβ/ζ in PTN-stimulated cells alone is sufficient to coordinately stimulate the different functions needed for an EMT; it is possible that PTN initiates an EMT in cells at sites where PTN is expressed in development and in malignant cells that inappropriately express
Ptn
.
Polymeric coatings that inactivate both influenza virus and pathogenic bacteria
Authors: Haldar Jayanta , An Deqiang , Álvarez de Cienfuegos Luis , Chen Jianzhu , Klibanov Alexander M.
Published: November 2006

Painting a glass slide with branched or linear
N
,
N
-dodecyl methyl-polyethylenimines (PEIs) and certain other hydrophobic PEI derivatives enables it to kill influenza virus with essentially a 100% efficiency (at least a 4-log reduction in the viral titer) within minutes, as well as the airborne human pathogenic bacteria
Escherichia coli
and
Staphylococcus aureus
. For most of the coating polyions, this virucidal action is shown to be on contact, i.e., solely by the polymeric chains anchored to the slide surface; for others, a contribution of the polyion leaching from the painted surface cannot be ruled out. A relationship between the structure of the derivatized PEI and the resultant virucidal activity of the painted surface has been elucidated.
Why yeast cells can undergo apoptosis: death in times of peace, love, and war
Authors: Büttner Sabrina , Eisenberg Tobias , Herker Eva , Carmona-Gutierrez Didac , Kroemer Guido , Madeo Frank
Published: November 2006

The purpose of apoptosis in multicellular organisms is obvious: single cells die for the benefit of the whole organism (for example, during tissue development or embryogenesis). Although apoptosis has also been shown in various microorganisms, the reason for this cell death program has remained unexplained. Recently published studies have now described yeast apoptosis during aging, mating, or exposure to killer toxins (Fabrizio, P., L. Battistella, R. Vardavas, C. Gattazzo, L.L. Liou, A. Diaspro, J.W. Dossen, E.B. Gralla, and V.D. Longo. 2004. J. Cell Biol. 166:1055–1067; Herker, E., H. Jungwirth, K.A. Lehmann, C. Maldener, K.U. Frohlich, S. Wissing, S. Buttner, M. Fehr, S. Sigrist, and F. Madeo. 2004. J. Cell Biol. 164:501–507, underscoring the evolutionary benefit of a cell suicide program in yeast and, thus, giving a unicellular organism causes to die for.
Interleukin-17 is a negative regulator of established allergic asthma
Authors: Schnyder-Candrian Silvia , Togbe Dieudonnée , Couillin Isabelle , Mercier Isabelle , Brombacher Frank , Quesniaux Valérie , Fossiez Francois , Ryffel Bernhard , Schnyder Bruno
Published: November 2006

T helper (Th)17 cells producing interleukin (IL)-17 play a role in autoimmune and allergic inflammation. Here, we show that IL-23 induces IL-17 in the lung and IL-17 is required during antigen sensitization to develop allergic asthma, as shown in IL-17R–deficient mice. Since IL-17 expression increased further upon antigen challenge, we addressed its function in the effector phase. Most strikingly, neutralization of IL-17 augmented the allergic response in sensitized mice. Conversely, exogenous IL-17 reduced pulmonary eosinophil recruitment and bronchial hyperreactivity, demonstrating a novel regulatory role of IL-17. Mechanistically, IL-17 down modulated eosinophil-chemokine eotaxin (CCL11) and thymus- and activation-regulated chemokine/CCL17 (TARC) in lungs in vivo and ex vivo upon antigen restimulation. In vitro, IL-17 reduced TARC production in dendritic cells (DCs)—the major source of TARC—and antigen uptake by DCs and IL-5 and IL-13 production in regional lymph nodes. Furthermore, IL-17 is regulated in an IL-4–dependent manner since mice deficient for IL-4Rα signaling showed a marked increase in IL-17 concentration with inhibited eosinophil recruitment. Therefore, endogenous IL-17 is controlled by IL-4 and has a dual role. Although it is essential during antigen sensitization to establish allergic asthma, in sensitized mice IL-17 attenuates the allergic response by inhibiting DCs and chemokine synthesis.
α2A-adrenoceptor stimulation improves prefrontal cortical regulation of behavior through inhibition of cAMP signaling in aging animals
Authors: Ramos Brian P. , Stark David , Verduzco Luis , van Dyck Christopher H. , Arnsten Amy F.T.
Published: November 2006

The working-memory functions of the prefrontal cortex (PFC) are improved by stimulation of postsynaptic, α2A-adrenoceptors, especially in aged animals with PFC cognitive deficits. Thus, the α2A-adrenoceptor agonist, guanfacine, greatly improves working-memory performance in monkeys and rats following systemic administration or intra-PFC infusion. α2A-adrenoceptors are generally coupled to Gi, which can inhibit adenylyl cyclases and reduce the production of cAMP. However, no study has directly examined whether the working-memory enhancement observed with guanfacine or other α2A-adrenoceptor agonists results from cAMP inhibition. The current study confirmed this hypothesis in both rats and monkeys, showing that treatments that increase cAMP-mediated signaling block guanfacine’s beneficial effects. In aged rats, guanfacine was infused directly into the prelimbic PFC and was challenged with co-infusions of the cAMP analog, Sp-cAMPS. In aging monkeys, systemically administered guanfacine was challenged with the phosphodiesterase 4 inhibitor, rolipram, using intramuscular doses known to have no effect on their own. In both studies, agents that mimicked the actions of cAMP (rats) or increased endogenous cAMP (monkeys) completely blocked the enhancing effects of guanfacine on working-memory performance. These results are consistent with α2A-adrenoceptor stimulation enhancing PFC working-memory function via inhibition of cAMP-mediated signaling.
The anatomy of amnesia: Neurohistological analysis of three new cases
Authors: Gold Jeffrey J. , Squire Larry R.
Published: November 2006

The most useful information about the anatomy of human memory comes from cases where there has been extensive neuropsychological testing followed by detailed post-mortem neurohistological analysis. To our knowledge, only eight such cases have been reported (four with medial temporal lobe damage and four with diencephalic damage). Here we present neuropsychological and post-mortem neurohistological findings for one patient (NC) with bilateral damage to the medial temporal lobe and two patients (MG, PN) with diencephalic damage due to bilateral thalamic infarction and Korsakoff’s syndrome, respectively. All three patients exhibited a similar phenotype of amnesia with markedly impaired declarative memory (anterograde and retrograde) but normal performance on tests of nondeclarative memory (e.g., priming and adaptation-level effects) as well as on tests of other cognitive functions. Patient NC had damage to the hippocampus (dentate gyrus and the CA1 and CA3 fields) and layer III of the entorhinal cortex, but with relative sparing of the CA2 field and the subiculum. Patient MG had damage to the internal medullary lamina and mediodorsal thalamic nuclei. Patient PN had damage to the mammillary nuclei, mammillothalamic tracts, and the anterior thalamic nuclei. These findings illuminate several issues regarding the relation between diencephalic and medial temporal lobe amnesia, the status of recognition memory in amnesia, and the neuroanatomy of memory.
ArabidopsisSAMT1 Defines a Plastid Transporter Regulating Plastid Biogenesis and Plant Development
Authors: Bouvier Florence , Linka Nicole , Isner Jean-Charles , Mutterer Jérôme , Weber Andreas P.M. , Camara Bilal
Published: November 2006

S-Adenosylmethionine (SAM) is formed exclusively in the cytosol but plays a major role in plastids; SAM can either act as a methyl donor for the biogenesis of small molecules such as prenyllipids and macromolecules or as a regulator of the synthesis of aspartate-derived amino acids. Because the biosynthesis of SAM is restricted to the cytosol, plastids require a SAM importer. However, this transporter has not yet been identified. Here, we report the molecular and functional characterization of an Arabidopsis thaliana gene designated SAM TRANSPORTER1 (SAMT1), which encodes a plastid metabolite transporter required for the import of SAM from the cytosol. Recombinant SAMT1 produced in yeast cells, when reconstituted into liposomes, mediated the counter-exchange of SAM with SAM and with S-adenosylhomocysteine, the by-product and inhibitor of transmethylation reactions using SAM. Insertional mutation in SAMT1 and virus-induced gene silencing of SAMT1 in Nicotiana benthamiana caused severe growth retardation in mutant plants. Impaired function of SAMT1 led to decreased accumulation of prenyllipids and mainly affected the chlorophyll pathway. Biochemical analysis suggests that the latter effect represents one prominent example of the multiple events triggered by undermethylation, when there is decreased SAM flux into plastids.