bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of growth temperature on the epitaxy strain relaxation and the
tilt of In
x
Al1−x

As graded layer grown by solid-source molecular beam epitaxy
Authors: Loke Wan Khai , Tan Kian Hua , Wicaksono Satrio , Yoon Soon Fatt , Owen Man Hon Samuel , Yeo Yee-Chia 
Published: November 2012

Abstract
In this study, we investigate the effect of the molecular beam epitaxial growth
temperature on the epilayer tilt and the strain relaxation in the InAlAs
M-buffer layer when the In composition is varied linearly from 6 to 57%
followed by an inverse grading to 52% where InAlAs is lattice-matched to
InP. The samples grown at 420 and 500 °C have final epilayer tilts of
0.66–0.68° about the

axis towards

, whereas the sample grown at 370 °C has a smaller
tilt of 0.15° about the

axis but towards [1 1 0]. Cross-sectional
transmission electron microscopy micrographs showed that the sample grown at
420 °C has the lowest dislocation density
(6 × 106 cm−2) compared
with those grown at 370 and 500 °C. The inversely graded layer in all
samples was shown to be effective in reducing the strain that was accumulated
during the forward graded layer. This resulted in close to fully relaxed
epilayers (92–99%), which are necessary for the prevention of
further occurrence of dislocation nucleation (an important criterion for
subsequent device structure growth).
Repetitive switching behaviour of a memristor for passive crossbar applications
Authors: Yan Z B , Zhu X C , Liu M , Jiang X M , Jiang X F , Liu J-M 
Published: November 2012

Abstract
The evolution of resistance switching behaviour of an Ag/DyMnO3/Ag/DyMnO3/Pt memristor structure under repetitive voltage sweeping is investigated. It is observed that the current–voltage (I–V) characteristic evolves from simple bipolar switching behaviour to a complicated switching sequence, which is applicable in passive crossbar arrays. It is suggested that the filament morphology can be modulated by accumulation and release of the Joule heating and Ag ions/atoms residing inside the DyMnO3 layer during continuous switching. The filament growth/dissolution near the upper surface of the middle Ag layer plays a key role in the consequent I–V characteristics.
Unusual behaviour of current–voltage relations in an unbalanced grid-assisted magnetron sputtering system
Authors: Sagás J C , Duarte D A , Fontana L C 
Published: November 2012

Abstract
Current–voltage relations were measured in an unbalanced grid-assisted magnetron sputtering system at different inter-electrode distances and magnetic field configurations. The intensity and configuration of the magnetic field were adjusted through an electromagnetic coil placed at the magnetron centre. This scheme allows observation of the current–voltage relations under conditions of weak and strong plasma confinement. Surprisingly, for some inter-electrode distances, a decreasing discharge current with increased magnetic field was observed. This unusual behaviour in grid-assisted magnetron discharges can be useful for a better understanding of abnormal glow discharges assisted by a magnetic field.
Cooperative effect of electronic and nuclear stopping on ion irradiation damage in silica
Authors: Backman M , Djurabekova F , Pakarinen O H , Nordlund K , Zhang Y , Toulemonde M , Weber W J 
Published: November 2012

Abstract
Radiation damage by ions is conventionally believed to be produced either by displacement cascades or electronic energy deposition acting separately. There is, however, a range of ion energies where both processes are significant and can contribute to irradiation damage. The combination of two computational methods, namely binary collision approximation and molecular dynamics, the latter with input from the inelastic thermal spike model, makes it possible to examine the simultaneous contribution of both energy deposition mechanisms on the structural damage in the irradiated structure. We study the effect in amorphous SiO2 irradiated by Au ions with energies ranging between 0.6 and 76.5 MeV. We find that in the intermediate energy regime, the local heating due to electronic excitations gives a significant contribution to the displacement cascade damage.
Investigations on irreversible- and reversible-type gas sensing for ZnO and Mg0.5Zn0.5Fe2O4 chemi-resistive sensors
Authors: Mukherjee K , Gaur A P S , Majumder S B 
Published: November 2012

Abstract
Semiconducting metal oxides are attractive material candidates for combustible gas sensors. Little or marginal base resistance drift of these metal oxide sensors is desirable during repeated response and recovery cycles. However, due to the partial recovery, often a significant drift in base resistance is observed. The gas sensing is termed irreversible when there is a partial recovery of base resistance, whereas for reversible sensing the base resistance is fully recovered. For reducing gas (hydrogen and carbon monoxide) sensing we have reported reversible and irreversible resistance transients for magnesium zinc ferrite and zinc oxide sensing elements, respectively. For a wide range of gas concentrations and operating temperatures, the response transients for these sensing elements are modelled using the Langmuir–Hinshelwood reaction mechanism. It is revealed that for irreversible-type sensing, the response time is reduced with the increase in test gas concentration. On the other hand, for reversible-type sensing, the response time is found to be independent of the gas concentration. Based on the estimation of pore size, pore size distribution and specific surface area of the calcined powder together with the analyses of the surface morphology of the sensing elements we have argued that due to the porous morphology of the magnesium zinc ferrite sensing element the oxidized product can easily desorb from the sensor during recovery. Therefore, irrespective of the test gas concentration, the base resistance of the magnesium zinc ferrite sensor recovers fully during the recovery process.
Decreased incidence of severe ovarian hyperstimulation syndrome in high risk in-vitro fertilization patients receiving intravenous albumin: a prospective study
Authors: Shalev E. , Giladi Y. , Matilsky M. , Ben-Ami M. 
Published: November 2012

Abstract
The administration of human serum albumin has been reported to prevent severe ovarian hyperstimulation syndrome (OHSS) in patients considered at risk of developing OHSS while undergoing ovarian stimulation protocols for in-vitro fertilization (IVF). This prospective, randomized study investigated the effectiveness of a single dose of human serum albumin (20 g) administered i.v. immediately after oocyte retrieval. Women enrolled in the IVF programme were treated with the long gonadotrophin-releasing hormone agonist, triptorelin, and an individually-adjusted human menopausal gonadotrophin protocol. The criteria for inclusion in the study were young age, nonobesity, oestradiol concentration &gt;9200 pmol/l on the day of human chorionic gonadotrophin administration and &gt;20 follicles &gt;14 mm diameter as observed by transvaginal sonography. The treatment group (n = 22) received albumin while the control group (n = 18) did not. Patients were followed-up using ultrasound every 3 days. There was a significantly higher number of severe OHSS cases in the control group (n = 4) than in the treatment group (n = 0) (P = 0.035). Where the data base was restricted to patients with an oestradiol concentration &gt;15 000 pmol/l, the difference between control and treatment groups was highly significant (P = 0.008). These findings support the use of i.v. albumin in preventing severe OHSS during IVF treatment.
Influenza Surveillance Among Children With Pneumonia Admitted to a District Hospital in Coastal Kenya, 2007–2010
Authors: Onyango Clayton O. , Njeru Regina , Kazungu Sidi , Achilla Rachel , Bulimo Wallace , Welch Stephen R. , Cane Patricia A. , Gunson Rory N. , Hammitt Laura L. , Scott J. Anthony G. , Berkley James A. , Nokes D. James 
Published: November 2012

Abstract

Background
Influenza data gaps in sub-Saharan Africa include incidence, case fatality, seasonal patterns, and associations with prevalent disorders.

Methods
Nasopharyngeal samples from children aged &lt;12 years who were admitted to Kilifi District Hospital during 2007–2010 with severe or very severe pneumonia and resided in the local demographic surveillance system were screened for influenza A, B, and C viruses by molecular methods. Outpatient children provided comparative data.

Results
Of 2002 admissions, influenza A virus infection was diagnosed in 3.5% (71), influenza B virus infection, in 0.9% (19); and influenza C virus infection, in 0.8% (11 of 1404 tested). Four patients with influenza died. Among outpatients, 13 of 331 (3.9%) with acute respiratory infection and 1 of 196 without acute respiratory infection were influenza positive. The annual incidence of severe or very severe pneumonia, of influenza (any type), and of influenza A, was 1321, 60, and 43 cases per 100 000 &lt;5 years of age, respectively. Peak occurrence was in quarters 3–4 each year, and approximately 50% of cases involved infants: temporal association with bacteremia was absent. Hypoxia was more frequent among pneumonia cases involving influenza (odds ratio, 1.78; 95% confidence interval, 1.04–1.96). Influenza A virus subtypes were seasonal H3N2 (57%), seasonal H1N1 (12%), and 2009 pandemic H1N1 (7%).

Conclusions
The burden of influenza was small during 2007–2010 in this pediatric hospital in Kenya. Influenza A virus subtype H3N2 predominated, and 2009 pandemic influenza A virus subtype H1N1 had little impact.
Is there another player in the game of Rubisco regulation?
Authors: Keys Alfred J. , Major Lain , Parry Martin A.J. 
Published: November 2012

Abstract
Leaves of French bean plants, whether collected in the dark or in the light, contained a tight-binding inhibitor of ribulose 1,5-bisphosphate carboxylase/ oxygenase (Rubisco). Wheat leaves contained such an inhibitor only in the light. The inhibitor in wheat leaves was not 2-carboxy-D-arabinitol 1-phosphate (CA1P) and not xylulose 1,5-bisphosphate. It was stable in acid conditions, but was destroyed during low pressure anion exchange chromatography and in alkaline conditions, especially during concentration of solutions. Although the kinetics of inhibition suggested tight-binding, the inhibitor did not survive attempts at purification by binding it to purified Rubisco followed by denaturation of the protein. The retention time of the inhibitory component on HPLC anion-exchange columns suggested that the substance was a sugar bisphosphate. Reduction with tritiated sodium borohydride and dephosphorylation produced radioactive sugar alcohols identified by TLC as ribitol and arabinitol. The small amounts of this inhibitor detected do not suggest a major physiological role, but instability during extraction may be obscuring its true importance.
Manipulating photosynthetic metabolism to improve crops: an inversion of ends and means
Authors: Walker David A. 
Published: November 2012

Abstract
The manipulation of photosynthetic carbon metabolism to bring about crop improvement or increased crop productivity is discussed against the background of population increase and an increasing tendency to favour investigations perceived to be of immediate practical advantage rather than supporting research of a more fundamental nature. The feasibility of improving productivity at a rate capable of matching the current daily increase in population of approximately 350 000 is considered and thought is given to the consequences of achieving that goal. Some environmental and intrinsic factors which are known to constrain photosynthesis are examined and it is proposed that, whereas there is no reasonable possibility of increasing quantum efficiency, there are many aspects of photosynthesis which are worthy of investigation in their own right and that these, if subjected to further investigation of a fundamental nature, could result in improvements in ‘efficiency’ in the wider sense of the word. It is concluded, nevertheless, that the greatest limitation on global agriculture is not water, temperature, pests or disease, but the cost and availability of fossil fuels, and that this fact should be kept uppermost when defining priorities in the light of future scenarios in which fossil fuel reserves are bound to dwindle more and more quickly during a period of massive population increase.
Engineering Rubisco to change its catalytic properties
Authors: Bainbridge Graeme , Madgwick Pippa , Parmar Saroj , Mitchell Rowan , Paul Matthew , Pitts Jim , Keys Alfred J. , Parry Martin A.J. 
Published: November 2012

Abstract
The initial steps of carbon assimilation and photorespiration are catalysed by ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39). Natural variation in the kinetic properties of the enzyme suggest that it is possible to alter the enzyme to favour the carboxylation activity relative to oxygenation. Mutagenesis in vitro of the gene encoding the large subunit of the enzyme from Anacystis nidulans has been used to modify catalytic properties. Residues at the C-terminal end of loop 6 of the β/α barrel structure of the large subunit influence specificity towards the gaseous substrates, CO2 and O2. None of the residues altered by mutagenesis appear to interact directly with the transition state analogue and their effect on the reaction of the enediolate intermediate with the gaseous substrates and stabilization of the resulting transition state intermediates by lysine 334 must be indirect. Interactions with other parts of the enzyme must also be important in determining substrate specificity. Backbone carbonyl groups close to lysine 334 interact with lysine 128; mutation of lysine 128 to residues of less positive polarity reduces enzyme activity and favours oxygenation relative to carboxylation. The likely effects on assimilation rates of altering the kinetic properties of Rubisco have been modelled. A leaf with cyanobacterial Rubisco may out-perform a higher plant Rubisco at elevated CO2 and cool temperatures.
Effects of light and atmospheric carbon dioxide enrichment on photosynthesis and carbon partitioning in the leaves of tomato (Lycopersicon esculentum L.) plants over-expressing sucrose phosphate synthase
Authors: Galtier Nathalie , Foyer Christine H. , Murchie Erik , Aired Rhu , Quick Paul , Voelker Toni A. , Thépenier Catherine , Lascève Gerard , Betsche Thomas 
Published: November 2012

Abstract
Photosynthetic carbon assimilation, carbon partitioning and foliar carbon budgets were measured in the leaves of transformed tomato plants expressing a maize sucrose-phosphate synthase (SPS) gene in addition to the native enzyme, and in untransformed controls. The maize SPS gene was expressed under control of either the promoter of the small subunit of ribulose 1,5-bisphosphate carboxylase (rbcS promoter; lines 2, 9 and 18) or the 35S promoter from cauliflower mosaic virus (CaMV promoter; line 13). The rate of sucrose synthesis was increased relative to that of starch and sucrose/starch ratios were higher throughout the photoperiod in the leaves of all plants expressing high SPS activity. The leaf carbon budget over the day/night cycle in air at low irradiance (180μmol photon m−2 s−1) was similar in all plants. Net photosynthesis measured in air and at elevated CO2 (800–1500 μl l−1) on whole plants grown in air at 400μmol m−2 s−1 irradiance was significantly increased in the high SPS expressors compared to the untransformed controls and was highest where SPS activity was greatest. At high CO2 the stimulation of photosynthesis was more pronounced. We conclude that SPS activity is a major point of control of photosynthesis particularly under saturating light and CO2.
The isolation and characterization of mutants of the C4 photosynthetic pathway
Authors: Dever L.V. , Blackwell R.D. , Fullwood N.J. , Lacuesta M. , Leegood R.C. , Onek L.A. , Pearson M. , Lea P.J. 
Published: November 2012

Abstract
Three novel classes of the C4 plant Amaranthus edulis are described. (1) A mutant that contains less than 10% of the normal activity and protein of phosphoenol-pyruvate carboxylase. (2) A mutant that is deficient in NAD-malic enzyme activity, but contains the normal two subunits of the enzyme protein. (3) Four mutant plants that accumulate high concentrations of glycine following exposure to air. A common characteristic of all the mutant plants is that they grow poorly in air and exhibit very low rates of photosynthetic CO2 assimilation.
The characteristics of the mutant lines are discussed with reference to our current knowledge of the regulation of the C4 photosynthesis pathway. The possibility that C4 plants undergo photorespiratory nitrogen and carbon metabolism when grown in air is considered in detail.
Functioning of the tonoplast in vacuolar C-storage and remobilization in crassulacean acid metabolism
Authors: Lüttge Ulrich , Fischer-Schliebs Elke , Ratajczak Rafael , Kramer Detlef , Berndt Ekkehart , Kluge Manfred 
Published: November 2012

Abstract
Nocturnal fixation of CO2 and storage of carbon in the form of malic acid in vacuoles of photosynthetically active cells are key processes of crassulacean acid metabolism (CAM). A prerequisite for malate transport into the vacuole is the concerted action of primary-active H+ -pumps, i.e. the tonoplast V0V1-H+-ATPase and H+ -PPiase, and a secondary-active carboxylate transporter. During the transition from C3-photosynthesis to CAM the H+ -ATPase of the C3/CAM-inter-mediate plant Mesembryanthemum crystallinum undergoes particular structural changes indicating an adaptation of the enzyme to the requirements for an increased capacity of tonoplast transport systems. The role of the H+-PPiase in energization of carbon transport in CAM remains unclear. While in Kalanchoë blossfeldiana cv. Tom Thumb, where CAM is induced by shortening of daylength, there is a higher expression of the H+-PPiase in the CAM state as compared to the C3-state, the enzyme disappears in M. crystallinum when CAM is induced by salt stress. However, the H+-PPiase could also be involved in the regulation of the H+-ATPase as shown by the PPistimulated ATP-dependent H+-transport activity found in K. daigremontiana and K. blossfeldiana cv. Tom Thumb. Although the tonoplast carboxylate transporter has not yet been identified, the kinetic parameters of the enzyme were characterized after partial purification and functional reconstitution into proteo-liposomes. While the influx of malate into the vacuole is mediated by the co-operation of different enzymes, the regulation of the passive efflux of malic acid from the tonoplast during the day may depend on biophysical membrane properties, i.e. the degree of order of the vacuolar membrane, which seems to be modulated by Ca2+.
The regulation and control of photorespiration
Authors: Leegood Richard C. , Lea Peter J. , Adcock Michael D. , Häusler Rainer E. 
Published: November 2012

Abstract
The photorespiratory pathway is described, together with the mutants which have been isolated for this metabolic pathway. Some of the key regulatory properties of the photorespiratory cycle are reviewed together with the regulatory interactions that might occur between photorespiration and other processes, such as the Benson-Calvin cycle and anaplerotic carbon flow into organic acids. These are discussed in relation to recent studies of the regulation and control of photorespiratory carbon and nitrogen metabolism in photorespiratory mutants, including possible mechanisms for the control of photosynthetic and photorespiratory carbon and nitrogen metabolism and of the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase in heterozygous barley mutants with reduced activities of glutamine synthetase or glutamate synthase.
Decarboxylation of primary and end products of photosynthesis at different oxygen concentrations
Authors: Pärnik Tiit , Keerberg Olav 
Published: November 2012

Abstract
A radiogasometric method for the determination of the rates of intracellular decarboxylation of primary and end products of steady-state photosynthesis in the light has been worked out. On the basis of oxygen dependence of the CO2 evolution, two types of decarboxylation, oxygenase (photorespiration) and oxidase (dark respiration), have been distinguished. Oxygenase decarboxylation is linearly dependent on O2 concentration in the range from 0 to 210 mmol mol−1, which is characteristic of the oxygenation of RuBP, the ratelimiting reaction of the glycolate cycle. Oxidase decarboxylation is saturated at relatively low O2 concentration (of about 15 mmol mol−1), similar to the oxidative reactions associated with glycolysis and the Krebs cycle. In the C3 plants (tobacco, wheat, barley) we have studied, primary products were decarb-oxylated predominantly via the oxygenase mechanism; the oxidase component was 3–15% of the total rate of the decarboxylation of primary photosynthates in the light. The oxygenase mechanism was also involved in the decarboxylation of end products of photosynthesis. The rate of this component exceeded by 3 to 5 times the rate of oxidase decarboxylation of end products in the light. It has been suggested that compounds derived from the degradation of end products of photosynthesis are incorporated into the reductive pentose phosphate cycle and, via the cycle, into the glycolate cycle where they are decarboxylated. In this way, four components of plant leaf respiration in the light may be distinguished according to the substrates and mechanisms of decarboxylation. In the dark, only one of them, oxidase decarboxylation of end products, is functioning. The rate of this component has been shown to be partially suppressed by light.
Metabolic Engineering of Tomato Fruit Organic Acid Content Guided by Biochemical Analysis of an Introgression Line
Authors: Morgan Megan J. , Osorio Sonia , Gehl Bernadette , Baxter Charles J. , Kruger Nicholas J. , Ratcliffe R. George , Fernie Alisdair R. , Sweetlove Lee J. 
Published: November 2012

Abstract
Organic acid content is regarded as one of the most important quality traits of fresh tomato (Solanum lycopersicum). However, the complexity of carboxylic acid metabolism and storage means that it is difficult to predict the best way to engineer altered carboxylic acid levels. Here, we used a biochemical analysis of a tomato introgression line with increased levels of fruit citrate and malate at breaker stage to identify a metabolic engineering target that was subsequently tested in transgenic plants. Increased carboxylic acid levels in introgression line 2-5 were not accompanied by changes in the pattern of carbohydrate oxidation by pericarp discs or the catalytic capacity of tricarboxylic acid cycle enzymes measured in isolated mitochondria. However, there was a significant decrease in the maximum catalytic activity of aconitase in total tissue extracts, suggesting that a cytosolic isoform of aconitase was affected. To test the role of cytosolic aconitase in controlling fruit citrate levels, we analyzed fruit of transgenic lines expressing an antisense construct against SlAco3b, one of the two tomato genes encoding aconitase. A green fluorescent protein fusion of SlAco3b was dual targeted to cytosol and mitochondria, while the other aconitase, SlAco3a, was exclusively mitochondrial when transiently expressed in tobacco (Nicotiana tabacum) leaves. Both aconitase transcripts were decreased in fruit from transgenic lines, and aconitase activity was reduced by about 30% in the transgenic lines. Other measured enzymes of carboxylic acid metabolism were not significantly altered. Both citrate and malate levels were increased in ripe fruit of the transgenic plants, and as a consequence, total carboxylic acid content was increased by 50% at maturity.