bluuebunny/crossref_metadata_2025 huggingface dataset:
Embryonic Stem Cells with GFP Knocked into the Dopamine Transporter Yield Purified Dopamine Neurons In Vitro and from Knock-In Mice
Authors: Zhou Wenbo , Lee Young Mook , Guy Vanessa C. , Freed Curt R.
Published: September 2009

Parkinson's disease (PD) is characterized by the selective loss of midbrain dopamine neurons. Neural transplantation with fetal dopamine neurons can be an effective therapy for patients with PD, but recovery of human fetal cells is difficult. Scarcity of tissue has limited clinical application to a small number of research subjects worldwide. Selective differentiation of embryonic stem cells (ESCs) to dopamine neurons could lead to an unlimited supply of cells for expanded clinical transplantation. To facilitate the differentiation and purification of dopamine neurons, the green fluorescent protein (GFP) gene was inserted into the dopamine transporter (DAT) locus in mouse ESCs using homologous recombination. From these DAT-GFP ESCs, dopamine neurons expressing GFP were successfully produced by in vitro differentiation. The DAT-GFP ESCs were used to generate DAT-GFP knock-in mice. We have found that GFP was colocalized with DAT, Pitx3, Engrailed-1, and tyrosine hydroxylase-positive cells in midbrain, hypothalamus, and olfactory bulb but not in noradrenergic cell regions or other ectopic sites. The GFP-positive dopamine neurons could be isolated from embryonic day-15 ventral midbrain by fluorescence activated cell sorting. These purified dopamine neurons survived reculture and expressed tyrosine hydroxylase and DAT when cocultured with mouse astrocytes or striatal cells. Animals homozygous for DAT-GFP were hyperactive because they had no functional DAT protein. These DAT-GFP knock-in ESCs and mice provide unique tools for purifying dopamine neurons to study their physiology, pharmacology, and genetic profiles.

Disclosure of potential conflicts of interest is found at the end of this article.
Architectural Growth of Cu Nanoparticles Through Electrodeposition
Authors: Ko Wen-Yin , Chen Wei-Hung , Cheng Ching-Yuan , Lin Kaun-Jiuh
Published: September 2009

Cu particles with different architectures such as pyramid, cube, and multipod have been successfully fabricated on the surface of Au films, which is the polycrystalline Au substrate with (111) domains, using the electrodeposition technique in the presence of the surface-capping reagents of dodecylbenzene sulfonic acid and poly(vinylpyrrolidone). Further, the growth evolution of pyramidal Cu nanoparticles was observed for the first time. We believe that our method might open new possibilities for fabricating nanomaterials of non-noble transition metals with various novel architectures, which can then potentially be utilized in applications such as biosensors, catalysis, photovoltaic cells, and electronic nanodevices.
Novel Two‐Phase Catalysis with Organometallic Compounds for Epoxidation of Vegetable Oils by Hydrogen Peroxide
Authors: Jiang Pingping , Chen Min , Dong Yuming , Lu Yun , Ye Xia , Zhang Weijie
Published: September 2009

A series of new organometallic catalysts for epoxidized vegetable oils using H2O2 in a biphasic system were investigated. The effect of reaction parameters such as the amount of hydrogen peroxide, reaction time and temperature in the epoxidation of soybean oil are discussed in detail. A selectivity of 83.8% was obtained in 4 h at 60 °C, when [(C18H37)2N(CH3)2]3{PO4[WO(O2)2]4} was used as the catalyst. When methyltrioxorhenium (MTO), imidazole and CH3CN were used as the catalyst, adduct, and solvent respectively, a selectivity of 99.90% was achieved in 4 h at 20 °C. The catalytic system was used for the epoxidation of other oils, whose results showed it was active in the epoxidation of long‐chain unsaturated compounds. Furthermore, the reaction of H2O2 with methyltrioxorhenium was studied by UV–Vis spectroscopy, which revealed the active peroxorhenium complexes formed during the reaction. Epoxidation of these oils with organometallic compounds occurred through the interactions between the oils unsaturated sites HOMO π(C–C) and the unoccupied peroxo σ*(O–O) orbital.
Percutaneous hemi-epiphysiodesis using transphyseal cannulated screws for genu valgum in adolescents
Authors: Mesa Pedro Antonio Sánchez , Yamhure Fernando Helo
Published: September 2009

Purpose

The purpose of this study was to assess percutaneous femoral distal hemi-epiphysiodesis using transphyseal cannulated screws in order to correct valgus angular deformities of the knee in pediatric and adolescent patients.

Methods

This is a prospective longitudinal study in which our experience with 52 patients is described.

Results

We evaluated 100 knees surgically managed for pathologic genu valgum over a 68-month period. The average age at surgery for boys and girls was 14 years and 7 months (range 12.7–15.1 years) and 13 years and 6 months (range 12.9–14.8 years), respectively. The pre-surgical tibiofemoral (T–F) angle was measured at between 14.17° and 35.3°, and the postoperative T–F was measured at between 6.2° and 15.8° (7.2° ± 0.65°, mean ± standard deviation), for an average correction of 0.73° ± 0.45° per month). The mean follow-up after surgery was 3.2 years (range 2.3–5.3 years).

Conclusions

We demonstrate a simple, fast and reproducible surgical technique for percutaneous epiphysiodesis with low morbidity, rapid rehabilitation and a rapid return to school and sports activities. We experienced no complications, such as overcorrection, undercorrection, postoperative hematoma or infection. We conclude that percutaneous screw epiphysiodesis is an excellent option for the treatment of genu valgum in adolescents.
Dynamic Monitoring of Cellular Remodeling Induced by the Transforming Growth Factor-β1
Authors: Staršíchová Andrea , Kubala Lukáš , Lincová Eva , Pernicová Zuzana , Kozubík Alois , Souček Karel
Published: September 2009

The plasticity of differentiated adult cells could have a great therapeutic potential, but at the same time, it is characteristic of progression of serious pathological states such as cancer and fibrosis. In this study, we report on the application of a real-time noninvasive system for dynamic monitoring of cellular plasticity. Analysis of the cell impedance profile recorded as cell index using a real-time cell analyzer revealed its significant increase after the treatment of prostate epithelial cells with the transforming growth factor-β1. Changes in the cell index profile were paralleled with cytoskeleton rebuilding and induction of epithelial–mesenchymal transition and negatively correlated with cell proliferation. This novel application of such approach demonstrated a great potential of the impedance-based system for noninvasive and real-time monitoring of cellular fate.
N‐Nitrosopiperidine and N‐Nitrosodibutylamine induce apoptosis in HepG2 cells via the caspase dependent pathway
Authors: García Almudena , Morales Paloma , Rafter Joseph , Haza Ana I.
Published: September 2009

The human hepatoma cell line (HepG2) exhibited a dose and time‐dependent apoptotic response following treatment with N‐Nitrosopiperidine (NPIP) and N‐Nitrosodibutylamine (NDBA), two recognized human carcinogens. Our results showed a significant apoptotic cell death (95%) after 24 h treatment with NDBA (3.5 mM), whereas it was necessary to use high doses of NPIP (45 mM) to obtain a similar percentage of apoptotic cells (86%). In addition, both extrinsic (caspase‐8) and intrinsic pathway (caspase‐9) could be implicated in the N‐Nitrosamines‐induced apoptosis. This study also addresses the role of reactive oxygen species (ROS) as intermediates for apoptosis signaling. A significant increase in ROS levels was observed after NPIP treatment, whereas NDBA did not induce ROS. However, N‐acetylcysteine (NAC) did not block NPIP‐induced apoptosis. All these findings suggest that NPIP and NDBA induce apoptosis in HepG2 cells via a pathway that involves caspases but not ROS.
The cytosolic subunit p67phox of the NADPH‐oxidase complex does not bind NADPH
Authors: Baciou Laura , Erard Marie , Dagher Marie-Claire , Bizouarn Tania
Published: September 2009

The NADPH‐oxidase of phagocytic cells is a multicomponent enzyme that generates superoxide. It comprises a membrane flavocytochrome b
558 and four cytosolic proteins; p67phox, p47phox, p40phox and Rac. The NADPH‐binding site of this complex was shown to be located on the flavocytochrome b
558. However, a number of studies have suggested the presence of another site on the p67phox subunit which is the key activating component. Using several approaches like tryptophan quenching fluorescence measurement, inhibition by 2′,3′‐dialdehyde NADPH, and free/bound NADPH concentration measurements, we demonstrate that no NADPH binds on p67phox, thus definitively solving the controversy on the number and location of the NADPH‐binding sites on this complex.
Time‐dependent regulation of muscle caveolin activation and insulin signalling in response to high‐fat diet
Authors: Gómez-Ruiz Ana , de Miguel Carlos , Campión Javier , Martínez J. Alfredo , Milagro Fermín I.
Published: September 2009

We studied the effect of high‐fat diet on the expression and activation of the three caveolins in rat skeletal muscle and their association with the insulin signalling cascade. Initial response was characterized by increased signalling through Cav‐1 and Cav‐3 phosphorylation, suggesting that both participate in an initial acute response to the calorie surplus. Afterwards, Cav‐1 signalling was slightly reduced, whereas Cav‐3 remained active. Late chronic phase signalling through both proteins was impaired inducing a prediabetic state. Summarizing, caveolins seem to mediate a time‐dependent regulation of insulin cascade in response to high‐fat diet in muscle.
Diacylglycerol kinase α enhances protein kinase Cζ‐dependent phosphorylation at Ser311 of p65/RelA subunit of nuclear factor‐κB
Authors: Kai Masahiro , Yasuda Satoshi , Imai Shin-ichi , Toyota Minoru , Kanoh Hideo , Sakane Fumio
Published: September 2009

We recently reported that diacylglycerol kinase (DGK) α enhanced tumor necrosis factor‐α (TNF‐α)‐induced activation of nuclear factor‐κB (NF‐κB). However, the signaling pathway between DGKα and NF‐κB remains unclear. Here, we found that small interfering RNA‐mediated knockdown of DGKα strongly attenuated protein kinase C (PKC) ζ‐dependent phosphorylation of a large subunit of NF‐κB, p65/RelA, at Ser311 but not PKCζ‐independent phosphorylation at Ser468 or Ser536. Moreover, knockdown and overexpression of PKCζ suppressed and synergistically enhanced DGKα‐mediated NF‐κB activation, respectively. These results strongly suggest that DGKα positively regulates TNF‐α‐dependent NF‐κB activation via the PKCζ‐mediated Ser311 phosphorylation of p65/RelA.
Comparison of four perioperative misoprostol regimens for surgical termination of first‐trimester pregnancy
Authors: Chambers Dennis G. , Mulligan Ea C. , Laver Anthony R. , Weller Bronwen K. , Baird Jane K. , Herbert Wye Y.
Published: September 2009

Objective

To compare the outcomes of 4 different perioperative misoprostol regimens for surgical termination of first‐trimester pregnancy.

Methods

Retrospective analysis of the records of 4000 women (4 cohorts of 1000 each) who underwent surgical termination of pregnancy. The 4 cohorts received: no misoprostol; 200 μg of oral misoprostol 30 minutes preoperatively; 200 μg of sublingual misoprostol 30 minutes preoperatively; or 200 μg of oral misoprostol 3 hours preoperatively plus 200 μg of vaginal misoprostol postoperatively. Adverse effects of the last regimen were surveyed in 1000 women.

Results

In the cohorts that received misoprostol, the difficulty of cervical dilatation was reduced (P < 0.001) compared with the cohort of women that did not receive misoprostol. The frequency with which women made postoperative contacts with the clinic was also reduced in the cohorts that received misoprostol (P < 0.05). Adverse effects were minimal.

Conclusions

This retrospective study showed an association between perioperative administration of misoprostol, reduced difficulty for operators, and reduced demand for postoperative care. The regimen associated with the greatest reduction in difficult cervical dilatations and postoperative consultations was 200 μg of oral misoprostol 3 hours preoperatively plus 200 μg of misoprostol vaginally at the end of the surgical procedure.
Commentary on “Alzheimer's disease drug development and the problem of the blood‐brain barrier”
Authors: Simpkins James W.
Published: September 2009

The perspective by Dr. William Pardridge entitled “Alzheimer's Disease Drug Discovery and the Problem of the Blood‐Brain Barrier” makes a strong case for the imbalance in resource distribution to the drug‐discovery and brain drug delivery processes, where the latter received less than 1% of the investment of the former. My own calculations are consistent with this striking imbalance. Dr. Pardridge predicts that current trials of passive immunity against β‐amyloid peptide will likely fail, whereas past trials of active immunization exhibited trial‐ending side effects, in part because of disruption of the integrity of the blood‐brain barrier. To bring an assessment of the physiology of the blood‐brain barrier and the brain delivery of drugs to the fore, several changes are needed in the way we perceive the problem, train our young scientists, organize research efforts, and incentivize reaching our common goals of effective drug therapy for Alzheimer's disease.
Deliberation in the face of power: Stakeholder planning in Egypt
Authors: Connelly Stephen
Published: September 2009

This paper explores how the expansion of processes of public engagement underpinned by the increasingly globalised principles of deliberative democracy depends on the presence and conscious exercise of discursive and institutional power. Using a case study of participatory planning programmes in the rural villages and smaller cities of Egypt – a context in which participation is an unfamiliar activity and governance is only nominally democratic – I address how the promotion of deliberation intersects with existing modes of governance and their underpinning institutional structures and cultural assumptions. This leads to a discussion of the potential for deliberation to contribute to broader democratisation processes, and of the nature of ‘deliberative democracy’, in politically hostile contexts. I conclude that designers of deliberative processes need to embrace the power-laden nature of all governance, and consciously ‘design in’ democratising institutional structures and discourses.
Some regional indicators of the Tertiary–Quaternary geodynamics in the paleocoastal part of the Bengal basin (India)
Authors: Dey S. , Ghosh S. , Debbarma C. , Sarkar P.
Published: September 2009

Sedimentary processes in the paleocoastal part of the Bengal basin that occured in the Tertiary and Quaternary have been addressed. Three indicators were used: sedimentary bedding forms, microstructure of the sediment, and trace fossils. Various forms of sedimentary structures developed under the influence of dynamic geomorphic processes in the study area in the Quaternary. The microstructure analysis of the sedimentary materials was made by two methods: microphotography and Digital Color Analysis (DCA). The microstructure analysis shows that the geomorphic process remained very dynamic in the Quaternary, influencing the form, thickness, and mineral composition of the sediment strata. The enrichment of the sediments in heavy minerals evidences either oscillating or combined flow sedimentation, while under stable conditions light-mineral deposition took place. The digital data of microfabric study by the DCA method also show that larger particles deposited in the oscillating or high-flow environment and evidence a greater amount of heavy minerals like ferruginous materials. Trace fossils found in the sediments of this area also strongly support the concept that the environment remained dynamic during the Tertiary and Quaternary. The Late Tertiary deposition shows that, during these periods, the sediments were transported from tide-dominated marine coast with low flow energy, which is typical of hot and humid conditions. From Late Tertiary to Early Quaternary, the macrotidal coast became mesotidal (wave-dominated). The second phase is the Middle Pleistocene, when the environment was stable, favoring the continuous deposition of finer particles under low- to medium-flow energy conditions. The third phase, the Recent, is marked by the shoreline shift and modification of the environment. In the Early–Middle Holocene, the shoreline started to shift, which modified the geomorphic conditions of this place from coastal to estuarine and, finally, inland fluvial.
Assignment of igneous rocks to lamproite: major- and trace-element criteria and implications for the history of the Tomtor pluton (northwestern Yakutia)
Authors: Bagdasarov Yu.A.
Published: September 2009

The paper presents objections against assigning picritic and some other igneous rocks to lamproite as suggested by N.V. Vladykin, both in general and in particular for the case of the large Tomtor pluton of alkaline and carbonatite rocks in northwestern Sakha Republic (Yakutia). Classifying the Tomtor picrites (picritic porphyry and its breccia-like varieties) as lamproite appears to be inconsistent with their chemistry, mineralogy, and geology. Discussed are errors and poorly proven postulates in the related publications by Vladykin, which contradict the available field data.
Identifying a lens of frozen ground in a low-conducting layer, from dc resistivity surveys
Authors: Kovbasov K.V. , Epov M.I. , Shurina E.P.
Published: September 2009

We explore the possibility to identify a nonconducting object of a known size and geometry buried in sand-clay conducting sediments lying over frozen ground. The anomaly, which is located on the surface of the low-conducting layer, is detected with a multi-electrode dc array. Its 3D electric field is simulated as a boundary-value problem using specially designed software. The new algorithm is tested with synthetic and field data and the results are used to develop the procedure of object identification and location.
The magnetic relaxation effect on TEM responses of a two-layer earth
Authors: Kozhevnikov N.O. , Antonov E.Yu.
Published: September 2009

We have simulated ungrounded horizontal loop transient responses of a two-layer earth consisting of a magnetically viscous layer above (model 1) or below (model 2) a nonmagnetic layer. The transient responses of a two-layer magnetically viscous earth can be computed using the superposition principle because magnetic relaxation and eddy current responses are independent at electrical conductivities typical of the real subsurface. The transients are presented and analyzed in the form of Y = f(h1) functions, where h1 is the upper layer thickness and Y is the response (at some fixed time) of a two-layer ground normalized to that of a uniform ground with its magnetic viscosity as in the upper (model 1) or lower (model 2) layer. In model 1, the Y function increases as magnetic viscosity grows in the upper layer while the latter is thinner than the loop size, but the magnetic relaxation responses of a thicker upper layer are almost identical to that of a uniform magnetically viscous ground. In model 2, the Y responses are likewise almost identical to that of a uniform magnetically viscous ground (h1 = 0) as far as the thickness of the upper layer remains small, but they decrease, first slowly and then ever more rapidly, after the layer becomes 15–20% thicker than the transmitter size. The effective sounditng depth in a magnetically viscous ground being controlled by the size of the transmitter, it is reasonable to use geometrical sounding to resolve the vertical distribution of magnetic viscosity.
New FTIR spectroscopy data on the composition of the medium of diamond crystallization in metamorphic rocks of the Kokchetav Massif
Authors: Sitnikova E.S. , Shatsky V.S.
Published: September 2009

A representative sample of microdiamonds in calc-silicate and garnet-pyroxene-quartz rocks and gneisses from the cross section of an adit driven at the Kumdy-Kol’ deposit (Northern Kazakhstan) has been analyzed. Microdiamonds from these rocks were studied by Fourier-transform infrared spectroscopy for the first time. It has been established that nitrogen impurity content (300–3000 ppm) and nitrogen aggregation degree (14–75%) vary widely and do not correlate with each other. The variation is probably due to the uneven distribution of nitrogen in crystals and to their specific internal structures.

The results of the study show that in most diamondiferous rocks, diamonds crystallized from a fluid/melt of composition varying between aqueous-carbonate and aqueous-silicate end-members. Spectroscopy studies partly disagree with literature data on individual nanoinclusions in diamonds. The cause of this discrepancy may be the evolution of the fluid/melt during diamond crystallization.
Reconstruction of phosphate formation environments (from data on distribution of lanthanides)
Authors: Shatrov V.A. , Voitsekhovskii G.V.
Published: September 2009

The criteria for the evaluation of the REE composition of phosphorites and sedimentary rocks have been determined. These data are required to reconstruct depositional environments. Literature data on the geochemistry of some phosphorite deposits of Eurasia are considered. The REE patterns of Mesozoic phosphorites of the East European Platform are studied. On the basis of REE contents, the ratios of lanthanides and fields on the La–(Nd + Sm)–(Y + Dy), La–(Ce + Nd + Sm)–(Y + Dy), and LREE–MREE–(HREE×10) diagrams have been determined as indicators of climate and the depth and facies conditions of sedimentation.
Isoferroplatinum mineral assemblage from the Burgastain Gol placer (Western Mongolia)
Authors: Oyunchimeg T. , Izokh A.E. , Vishnevsky A.V. , Kalugin V.M.
Published: September 2009

Platinum group element (PGE) mineral assemblage has been discovered in the gold placers along the Burgastain Gol and Iljgen Gol (Western Mongolia). It includes isoferroplatinum (Pt3Fe) grains with inclusions of cooperite (PtS), laurite-erlichmanite (RuS2-OsS2), cuprorhodsite-malanite (CuRh2S4-CuPt2S4), irarsite-hollingworthite (IrAsS-RhAsS), and bowieite (Rh2S3).

It has been established that the isoferroplatinum assemblage was generated from a volcanoplutonic picrite complex in the Ureg Nuur area, which is widespread in the central part of the Harhiraa accretionary terrane. According to composition, the PGE mineral–Cr-spinel assemblage was referred to as the Ural-Alaskan type.
Hydrogeological conditions of the Pre-Yenisei petroleum subprovince
Authors: Novikov D.A. , Shvartsev S.L.
Published: September 2009

The study presents results of a hydrogeological and hydrogeological research conducted on the Mesozoic–Cenozoic sedimentary cover and Precambrian–Paleozoic platform deposits of the Pre-Yenisei petroleum subprovince. The hydrogeological structure of the study area is found to be of a transition type from the West Siberian to Tunguska artesian basins, with its own set of pertinent parameters, such as groundwater depths, rock permeabilities, water chemistry and gas compositions, gas saturation, vertical zoning, etc. The upper part of the sedimentary section is known to be flushed with the infiltration waters to depths of 2–2.5 km. The deeper intervals contain the older sedimentary waters with the moderate metamorphic grade. The results of the study provide implications for the petroleum potential of the area of interest.
Stress may enhance nicotine effects on periodontal tissues. An in vivo study in rats
Authors: Benatti Bruno Braga , Nogueira‐Filho Getúlio R. , Diniz Marcelo Carvalho , Sallum Enilson Antonio , Sallum Antonio Wilson , Nociti Francisco H.
Published: September 2009

Objectives and background:  Diabetes mellitus and smoking have been described as important risk factors that may affect the initiation and progression of periodontitis. Recent studies have pointed to potentially periodontal risk indicators, which include stress. The present study investigated the effects of stress associated with nicotine administration on periodontal breakdown resulting from ligature‐induced periodontitis in rats.

Methods:  Twenty adult male Wistar rats were used. After anesthesia, both mandibular first molars received a cotton ligature in the dento‐gingival area. The animals were randomly assigned to one of the following experimental groups: A – saline solution, B – 0.73 mg of nicotine/kg/d (intraperitoneal), C – stress (immobilization – 2 h/d/40 d) associated with an intraperitoneal administration of saline solution, and D – stress (immobilization – 2 h/d/40 d) associated with an intraperitoneal injection of 0.73 mg of nicotine/kg/d. Forty days later, the animals were sacrificed and the specimens routinely processed for serial decalcified sections.

Results:  Intergroup analysis (ANOVA) revealed a greater bone loss (P < 0.05) in the animals of group D compared with the animals from groups A, B and C. In addition, the data revealed a significant effect of nicotine (group B) compared with groups A and C (P < 0.05), and no difference between groups A and C (P > 0.05).

Conclusion:  Within the limits of the present study, although stress did not affect periodontitis by itself, it significantly enhanced the effects of nicotine on the periodontal tissues.
The effects of exurbanization on the food and habitat of pileated woodpeckers
Authors: Wilson Marie , Casey Jordan , Haskell David , Hollingshead Nick
Published: September 2009

Background/Question/Methods

Dryocopus pileatus (pileated woodpeckers) are the largest woodpeckers in the United States. They require large trees for roosting, nesting, and feeding and these trees must be dead or dying for ease of excavation and presence of the woodpeckers' main prey of ants and grubs. Because of these habitat requirements, pileated woodpeckers are used as an indicator species for mature forests. However, their status in exurban areas, or places of low-density development beyond the suburban fringe, is poorly known. Because exurbanization covers a large and growing portion of the eastern U.S.A., we examined how pileated woodpeckers and their habitat vary across a gradient of exurbanization. We tested the hypothesis that presence of pileated woodpeckers is positively correlated with forest structure and food availability, in exurban and forested areas. We conducted the study in Sewanee, Tennessee, U.S.A., establishing 30 randomly located sample points evenly divided between exurban and forested areas. At each point we assessed pileated woodpecker presence through visual and vocal surveys; forest structure through measures of downed wood, standing trees, and understory density; and food availability through presence of ants and grubs in soil cores and pitfall traps.

Results/Conclusions

We found no difference between the presence of pileated woodpeckers, amount and rot class of dead wood, and ant and grub abundance between exurban and forested areas. Mean tree diameter was larger in exurban areas most likely because many small trees had been removed by human landscaping. These data suggest that some exurban areas may provide habitat for pileated woodpeckers. However, more studies are needed to examine the breeding success and survival rates of pileated woodpeckers in exurban and forested areas. Because the mature forest characteristics that pileated woodpeckers prefer can be found in exurban areas, it is possible that other species requiring these characteristics could also find usable habitat in exurban areas. This could apply most specifically to those secondary cavity-nesting species that use old pileated woodpecker nesting cavities. More studies should be conducted to further explore the effects of exurbanization on other species that are thought of as indicating mature forests.
Monte Carlo investigation of the critical properties of a three-dimensional frustrated Heisenberg model on a triangular lattice
Authors: Murtazaev A. K. , Ramazanov M. K. , Badiev M. K.
Published: September 2009

The Monte Carlo replica method is used to investigate the critical properties of a three-dimensional frustrated antiferromagnetic Heisenberg model on a triangular lattice. The static magnetic and chiral critical exponents are calculated within the theory of finite-dimensional scaling: specific heat α=0.05(2); magnetization β=0.30(1), βk=0.52(2); susceptibility γ=1.36(2), γk=0.93(3); and, correlation radius ν=0.64(1), νk=0.64(2). The critical Fisher indices η=−0.06(3) and ηk=0.63(4) for this model are calculated for the first time. It is shown that the three-dimensional frustrated Heisenberg model on a triangular lattice forms a new universality class of critical behavior. It is found that the universality class of the antiferromagnetic Heisenberg model on a triangular lattice depends on the type of interlayer exchange interaction.
Nanoparticle size effect on the magnetic and transport properties of (La0.7Sr0.3)0.9Mn1.1O3 manganites
Authors: Dyakonov V. , Ślawska-Waniewska A. , Kazmierczak J. , Piotrowski K. , Iesenchuk O. , Szymczak H. , Zubov E. , Myronova S. , Pashchenko V. , Pashchenko A. , Shemjakov A. , Varyukhin V. , Prilipko S. , Mikhaylov V. , Kravchenko Z. , Szytuła A. , Bazela W.
Published: September 2009

Magnetic and transport thermal measurements of nanosize (La0.7Sr0.3)0.9Mn1.1O3 manganite are reported. The nanoparticles are synthesized with use of the co-precipitation method at different (800, 900, and 950°C) temperatures. Their crystal structure is determined to be perovskite-like with a rhombohedral distortion (the space group R3¯c). The phase composition and specific surface nanopowders are determined. The average size of synthesized nanoparticles (from 40to100nm) is estimated by both the method of low-temperature adsorption of argon and x-ray diffraction measurements. All the nanosize samples show ferromagnetic-like ordering with close phase transition temperatures. Their magnetization decreases with decreasing particle size. Comparison of experimental and calculated temperature dependences of the spontaneous magnetic moment shows that the spontaneous magnetization both in magnetic field and without field is well described in the framework of the double exchange model. The decrease of the magnetization with decreasing particle size is due to the increasing surface contribution to the magnetization. The magnetic entropy is shown to increase with increasing applied magnetic field and to be smaller for the small particles. The resistivity is found to become higher with decreasing particles size at any temperatures.
The study on the work function of CdZnTe with different surface states by synchrotron radiation photoemission spectroscopy
Authors: Zha Gangqiang , Jie Wanqi , Bai Xuxu , Wang Tao , Fu Li , Zhang Wenhua , Zhu Junfa , Xu Faqiang
Published: September 2009

The work functions of CdZnTe single crystal with different surface states were measured using synchrotron radiation photoemission spectroscopy. The work function of CdZnTe after mechanical and chemical polishing is higher than that of clean and ordered surface. The damage layer deduced by Ar ion sputtering increases the work function. The Te adatoms of the CdZnTe (111)B (2×2) reconstruction form the interface dipole and increase the work function. The effects of H2O adsorption and Au evaporation on the work function of CdZnTe were investigated. The relationships among work function, surface dipole, valence band bending, ionization energy, and electron affinity of CdZnTe with different surface states were discussed.
Collisional depolarization of NO(A) by He and Ar studied by quantum beat spectroscopy
Authors: Brouard M. , Chadwick H. , Chang Y.-P. , Cireasa R. , Eyles C. J. , La Via A. O. , Screen N. , Aoiz F. J. , Kłos J.
Published: September 2009

Zeeman and hyperfine quantum beat spectroscopies have been used to measure the total elastic plus inelastic angular momentum depolarization rate constants at 300 K for NO(A Σ2+) in the presence of He and Ar. In the case of Zeeman quantum beats it is shown how the applied magnetic field can be used to allow measurement of depolarization rates for both angular momentum orientation and alignment. For the systems studied here, collisional loss of alignment is more efficient than loss of orientation. In the case of NO(A) with He, and to a lesser extent NO(A) with Ar, collisional depolarization is found to be a relatively minor process compared to rotational energy transfer, reflecting the very weak long-range forces in these systems. Detailed comparisons are made with quantum mechanical and quasiclassical trajectory calculations performed on recently developed potential energy surfaces. For both systems, the agreement between the calculated depolarization cross sections and the present measurements is found to be very good, suggesting that it is reasonable to consider the NO(A) bond as frozen during these angular momentum transferring collisions. A combination of kinematic effects and differences in the potential energy surfaces are shown to be responsible for the differences observed in depolarization cross section with He and Ar as a collider.
Synthesis of interstellar 1,3,5-heptatriynylidyne, C7H(X Π2), via the neutral-neutral reaction of ground state carbon atom, C(P3), with triacetylene, HC6H (X Σ1g+)
Authors: Sun B. J. , Huang C. H. , Tsai M. F. , Sun H. L. , Gao L. G. , Wang Y. S. , Yeh Y. Y. , Shih Y. H. , Sia Z. F. , Chen P. H. , Kaiser R. I. , Chang A. H. H.
Published: September 2009

The reaction of ground-state carbon atom with a polyyne, triacetylene (HC6H) is investigated theoretically by combining ab initio calculations for predicting reaction paths, RRKM theory to yield rate constant for each path, and a modified Langevin model for estimating capturing cross sections. The isomerization and dissociation channels for each of the five collision complexes are characterized by utilizing the unrestricted B3LYP/6-311G(d,p) level of theory and the CCSD(T)/cc-pVTZ calculations. Navigating with the aid of RRKM rate constants through web of ab initio paths composed of 5 collision complexes, 108 intermediates, and 20 H-dissociated products, the most probable paths, reduced to around ten species at collision energies of 0 and 10 kcal/mol, respectively, are identified and adopted as the reaction mechanisms. The rate equations for the reaction mechanisms are solved numerically such that the evolutions of concentrations with time for all species involved are obtained and their lifetimes deduced. This study predicts that the five collision complexes, c1–c5, would produce a single final product, C7H (p1)+H, via the most stable intermediate, carbon chain HC7H (i1); namely, C+HC6H→HC7H→C7H+H. Our investigation indicates that the title reaction is efficient to form astronomically observed C7H in cold molecular clouds, where a typical translational temperature is 10 K.
Stable two-dimensional ferromagnets made of regular single-layered lattices of single-molecule nanomagnets with perpendicular anisotropy
Authors: Zheng Rui , Liu Bang-Gui
Published: September 2009

We propose that stable two-dimensional (2D) ferromagnets can be made of regular single-layered lattices of single-molecule nanomagnets with enough perpendicular uniaxial magnetic anisotropy on appropriate substrates by controlling the internanomagnet magnetic interaction. Our Monte Carlo simulated results show that such ideal 2D ferromagnets are thermodynamically stable when the anisotropy is strong enough. Magnetization, fourth-order Binder’s cumulant, specific heat, and magnetic susceptibility as functions of temperature are calculated for various anisotropy parameters. If the anisotropy energy equals 80 K, approximately that of the Mn12, the TC varies from 0 to 15 K depending on different internanomagnet coupling constants. Such stable spin systems, experimentally accessible, should be promising for information applications.
Multiparameter admittance spectroscopy for metal-oxide-semiconductor systems
Authors: Piscator J. , Raeissi B. , Engström O.
Published: September 2009

Admittance spectroscopy is extended for measuring capacitance and conductance on metal-oxide-semiconductor (MOS) structures as a function of gate voltage, frequency, and temperature. An automatic setup has been designed for collecting data along these dimensions in one measurement cycle. The theory for admittance spectroscopy has been developed by starting from basic charge carrier statistics. Using numerical integration of energy dependent parameters instead of the commonly used analytical solution, conductance dispersion curves are obtained which do not need to be adjusted by assuming lateral surface potential variations at the oxide-semiconductor interface. Also, we find that interface state densities extracted by using traditional methods are four times lower than those obtained by using our theory. Experimental data presented in three-dimensional plots are compared with theoretical calculations, revealing the possibilities and limitations of the conductance method.
The effect of impurities on hydrogen bonding site and local vibrational frequency in ZnO
Authors: Bang Junhyeok , Choi Eun-Ae , Chang K. J.
Published: September 2009

For isovalent impurities such as Be, Mg, Ca, Sr, and Cd and group-I element such as Na in ZnO, first-principles local-density-functional calculations show that the interstitial position of H depends on the type of impurities, either occupying a bond center (BC) site or an antibonding (AB) site adjacent to the impurity atom. The AB site is more favorable in the vicinity of Na, Ca, Sr, and Cd, while the stable position is the BC site in the case of Be. We find that both electronegativity and atomic size play a role in switching the H interstitial position between the BC and AB sites. Previous studies have suggested that two infrared lines observed at 3611 and 3326 cm−1 result from hydrogen atoms positioned at BC and AB sites, respectively. The results for the H bonding sites and defect concentrations suggest that Ca is the most probable impurity as the origin of the infrared line at 3326 cm−1. However, for impurities around which H is positioned at the AB site, the calculated local vibrational frequencies are found to be similar to within 30 cm−1, making it difficult to determine the specific impurity responsible for the 3326 cm−1 line.
Nanoscale band gap spectroscopy on ZnO and GaN-based compounds with a monochromated electron microscope
Authors: Bosman M. , Tang L. J. , Ye J. D. , Tan S. T. , Zhang Y. , Keast V. J.
Published: September 2009

Monochromated low-loss EELS (electron energy-loss spectroscopy) is explored as an analytical technique for nanoscale mapping of the electronic band gap energy on arsenic-implanted ZnO, CdZnO, and InGaN compounds. Its accuracy is confirmed independently with Raman spectroscopy. From a ternary compound, the relationship between the band gap energy and the chemical composition is determined, a powerful application of low-loss EELS. The effects of electron beam delocalization are discussed using examples from In0.25Ga0.75N quantum wells.
Atoms in boxes: From confined atoms to electron-atom scattering
Authors: van Faassen Meta
Published: September 2009

We show that both confined atoms and electron-atom scattering can be described by a unified basis set method. The central idea behind this method is to place the atom inside a hard potential sphere, enforced by a standard Slater type basis set multiplied by a cutoff factor. For confined atoms, where the wall is placed close to the atomic nucleus, we show how the energy of the highest occupied atomic orbital and the static polarizability of helium and neon atoms evolve with the confinement radius. To our knowledge, these are the first confined atom polarizability calculations that include correlation for many-electron atoms, through the use of time-dependent density-functional theory. By placing the atom in a large spherical box, with a wall outside the electron density, we obtain scattering phase shifts using a recently developed method [M. van Faassen, A. Wasserman, E. Engel, F. Zhang, and K. Burke, Phys. Rev. Lett. 99, 043005 (2007)]. We show that the basis set method gives identical results to previously obtained phase shifts for e-H and e-He+ scattering.
Study of molecular dynamics of pharmaceutically important protic ionic liquid-verapamil hydrochloride. I. Test of thermodynamic scaling
Authors: Wojnarowska Z. , Paluch M. , Grzybowski A. , Adrjanowicz K. , Grzybowska K. , Kaminski K. , Wlodarczyk P. , Pionteck J.
Published: September 2009

Relaxation dynamics of verapamil hydrochloride (VH), which is a representative of ionic liquids, was studied under isobaric and isothermal conditions by using dielectric spectroscopy. In addition we also carried out pressure-temperature-volume (PVT) measurements. The obtained data enable us to examine the structural α-relaxation time τα as a function of temperature, pressure, and volume. Since the examined sample is a typical ionically conducting material, we employed the dielectric modulus formalism to gain information about α-relaxation process. It was found that application of pressure changes the shape of the modulus spectrum. The α-peak becomes narrower with compression. Consequently, it was also shown that the stretching parameter βKWW increases with pressure. Based on experimental data both the isobaric fragility (mp) at various pressures and isothermal fragility (mT) at various temperatures were calculated. Analyzing the effect of pressure on the dependences τα(T) as well as on the shape parameter of the α-peak it was found that a phenomenological correlation between mp and βKWW established for glass forming liquids is also valid for VH under condition of high compression. The pressure dependences of glass-transition temperature determined from dielectric and volumetric measurements have been compared. Moreover, PVT data allow us to assess the relative contribution of thermal energy and free volume fluctuation to the dramatic slowing down of the molecular dynamics in the vicinity of Tg. It is established from the ratio of the isochronic and isobaric expansivities that the thermal energy has a stronger effect on the relaxation times than the free volume, although the latter contribution is significant. Finally, we also discuss the validity of thermodynamic scaling in the case of VH and examine the scaling exponent γ at various thermodynamic conditions.
Properties of electron swarms in CF3I
Authors: Hasegawa H. , Date H. , Shimozuma M. , Itoh H.
Published: September 2009

We report the electron swarm parameters, the drift velocity, and the ionization coefficients in CF3I gas for relatively wide ranges of reduced electric fields (E/N). The drift velocity is measured based on the arrival-time spectra of electrons for E/N=200–3000 Td, and the first and second ionization coefficients are determined by the steady-state Townsend method for E/N=400–5000 Td. The results are compared with those of CF4 to show that CF3I has a high reactivity for electron attachment in a low E/N region resulting in a much higher limiting E/N value (440 Td) than that of CF4.
Energy resolved spin dependent tunneling in 1.2 nm dielectrics
Authors: Ryan J. T. , Lenahan P. M. , Krishnan A. T. , Krishnan S.
Published: September 2009

We demonstrate an electron paramagnetic resonance technique which simply links point defect structure and energy levels in a very direct way. The technique’s simplicity and the robust character of the response make it, at least potentially, of widespread utility in the understanding of defects important in solid state electronics. Since the specific defect observed is generated in silicon oxynitride by high electric field stressing, an important device instability problem in present day integrated circuitry, the observations are of considerable importance for microelectronics technology.
Large magnetic-field-induced strains in Ni–Mn–Ga nonmodulated martensite
Authors: Chernenko V. A. , Chmielus M. , Müllner P.
Published: September 2009

Large magnetic field-induced strains of up to 0.17% for a stress-free Ni53.1Mn26.6Ga20.3 single crystal with nonmodulated martensite phase were generated in a rotating magnetic field. This magnetic-field-induced strain, which is ten times larger than values reported so far for nonmodulated martensites, evidences significant magnetic-field-induced twin boundary motion, which so far was thought to be impossible. This result reinforces the interest in nonmodulated martensites, which are formed as a ground state in the Heusler-type ferromagnetic shape memory alloys.
Driven simulations of the dynamic heat capacity
Authors: Brown Jonathan R. , McCoy John D. , Adolf Douglas B.
Published: September 2009

The dynamic heat capacity is calculated from molecular dynamics simulations of a model glass former of simple bead-spring chains. The temperature is directly modulated and the energy tracked. The frequency-dependent heat capacity is found as the complex response function. There is agreement both with molecular dynamics simulations of related glass formers and with an energy-landscape-based, two state model. In particular, at high packing fraction, a low frequency loss peak is seen to split from the main, high frequency peak. This low frequency peak describes the configurational contribution to the heat capacity associated with the glass transition. Although the current application is in the linear response regime, this methodology paves the way for studies of nonlinear response that parallel experiment.
Essential oil variation in Eucalyptus crebra, E. melanophloia (Myrtaceae) and their hybrids
Authors: Brophy Joseph J. , Forster Paul I. , Goldsack Robert J. , Hibbert D. Brynn , Punruckvong Acharaporn
Published: September 2009

The leaf essential oils obtained from Eucalyptus melanophloia F.Muell., E. crebra F.Muell. and their hybrids from four widely separated sites were investigated. The major components that were observed, of the predominantly monoterpenoid oils, were α-pinene (1–58%), 1,8-cineole (0.2–60%) and p-cymene (0.2–21%). Oils tended to be unique to each locality investigated and although the parental species were discrete on their profiles, the oils of the hybrids appeared not to differ from those of their putative parents when commonly used methods of analysis (e.g. principal components analysis, PCA) were applied. Leaf oils are a complex mixture of components and elucidating differences among large datasets such as these can be difficult by traditional methods of analysis. Linear discriminant analysis (LDA) was applied to the oils data and it was found that with a forward stepwise LDA with 13 or 16 components of 70, it was possible to distinguish between the parents and their hybrids at a particular site or where the parents and hybrids originated.