Hydrobiology of Colombo (Beira) Lake, 1. Diurnal variations in temperature, hydrochemical factors and zooplankton

An extensive study of the hydrobiology of the Colombo Lake was initiated by the authors in May 1969 as a contribution to the International Biological Program (Productivity of freshwater communities) by the Department of Zoology, Vidyalankara University of Ceylon, Kelaniya. The Colombo Lake often referred to as the Beira Lake covers an area of approximately 160 acres. The water is usually very turbid with a greenish blue appearance due to the presence of large quantities of blue green algae.

The fishing centres of Lake Niassa (Mozambique): results of a frame survey made in June 1983

Results of the first frame survey of the fishing centres on the Mozambican coast of Lake Niassa, held in June 1983, are presented. A total of 41 fishing centres were detected in the area and visited. Through direct enquiries in each centre, an estimated number of 3,380 fishermen and 1,230 fishing boats (of which 25 motorized) was established. The results also provided information on the types and quantities of fishing gear used. A first estimation of the approximate total annual catch in the area gave a figure in the order of 9,100 tons., of which approximately equals 90% is landed during the rainy season. The survey is a part of a research programme on the fishing resources of Lake Niassa and of a project for the collection and organization of fisheries statistics from the artisanal fisheries of the Mozambican side of Lake Niassa.

National Agricultural Research Organisation. Fisheries Resources Research Institute Annual Report 2002/2003

One of the avenues through which the Government objective of poverty eradication in Uganda can be achieved is Fisheries development and management. Up to 20% of Uganda’s surface area is covered by aquatic systems i.e. lakes, rivers, streams and swamps and to a large extent, all these are interconnected. The large lakes: Victoria, Albert, Kyoga, George and Edward are sites of the more important commercial fisheries, but even the smaller water bodies, rivers (e.g. the Rivers Nile and Kagera) and the surrounding swamps provide sources of livelihood to rural areas. Fish is an important source of high quality food, employment revenue and is currently the second most important export commodity next to coffee generating approximately US $ 80 million annually. Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh is rich in proteins, which are superior to those of beef and poultry. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans

National Agricultural Research Organisation. Fisheries Resources Research Institute Annual Report 2003/2004

About 18% of Uganda’s surface area is covered with water from which 300,000 metric tonnes of fish are produced. Fish are currently the second most important export commodity generating approximately US$100 million. Fish provides 50% of protein diet for the 20 million people translating into per capita consumption of 12 kg. Close to the production system, this figure rises to 50 – 100 kg. It is estimated that fishery-related activities employ at least one million people countrywide (i.e. 5% of the population). Fish is an important source of high quality food, employment, and revenue and it is currently the second most important export commodity next to coffee generating approximately US $ 80 million annually. Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh is rich in proteins, which are superior to those of beef and poultry. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans.

National Agricultural Research Organisation. Fisheries Resources Research Institute Annual Report 2004/2005

About 18% of Uganda’s surface area is covered with water from which about 300,000 metric tonnes of fish are produced. Fish are currently the second most important export commodity generating approximately US$100 million annually. Fish provides 50% of protein diet for the 20 million people translating into per capita consumption of 12 kg. Close to the production system, this figure rises to 50 – 100 kg. It is estimated that fishery-related activities employ at least one million people countrywide (i.e. 5% of the population). Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans

Notes on the induced maturation and spawning in four-month-old Penaeus monodon Fabricius by eyestalk ablation

The ablation technique consisted of making an incision across the eyeball to allow free flow of fluids while holding the prawn under water, squeezing the eyeball contents outwards, and pinching hard the eyestalk tissue. The cut area heals completely in about a week; no application of antibiotics is necessary. Spent spawners were tagged with thin brass rings (Rodriguez, 1976) around the unablated eyestalk for a separate experiment on rematuration. Two spawning yielding approximately 277,000 eggs were obtained three weeks after ablation, followed four days later by two more spawnings with 160,000 eggs; all four spawners weighed more than 100 g. With a hatching rate of 98% and 78% for the first and second batch, respectively, the spawnings produced viable nauplii. Water temperatures as low as 23 degree C due to a delayed cold spell in March depressed molting; weakened larvae had to be discharged at the mysis stage. Although ovarian development continued, no further spawnings were obtained due mainly to the onset of bacterial and fungal disease. Infection is initiated in injured portions of the exoskeleton, sometimes penetrating right through the muscles to the ovarian tissues. The non-flowthrough conditions and mussel meat feeding led to fouling of the culture water resulting in consecutive mortalities caused by disease. Female P.monodon held in maturation pens were ablated at the age of 15 months (Santiago, et al., 1976); they averaged only 16 g body weight after four months growth in ponds. In another experiment, pond-reared P.monodon females ranging from 50 to 80 g were ablated at approximately seven months (Aquacop, 1977). The present results show a minimum age of four months from postlarve that P.monodon is capable of ovarian development and spawning upon ablation. However, maturation is probably affected by size as well as age - the four-month old females weighed an average of 100 g in contrast to the smaller animals in the earlier experiments.

Self-organized superlattices along the [001] growth direction in In0.52Al0.48As layers grown on nominally (001) InP substrates by molecular beam epitaxy

Horizontal self-organized superlattice structures consisting of alternating In-rich and Al-rich layers formed naturally during solid-source molecular beam epitaxy (MBE) growth of In0.52Al0.48As on exactly (001) InP substrates, with In and At fluxes unchanged. The growth temperatures were changed from 490 to 510 degrees C, the most commonly used growth temperature for In0.52Al0.48As alloy. No self-organized superlattices (SLs) were observed at the growth temperature 490 degrees C, and self-organized SLs were observed in InAlAs layers at growth temperatures ranging from 498 to 510 degrees C. The results show that the period of the SLs is very highly regular, with the value of similar to 6 nm, and the composition of In or Al varies approximately sinusoidally along the [001] growth direction. The theoretical simulation results confirm that the In composition modulation amplitude is less than 0.02 relative the In composition of the In0.52Al0.48As lattice matched with the InP substrate. The influence of InAs self-organized quantum wires on the spontaneously formed InxAl1-xAs/InyAl1-yAs SLs was also studied and the formation of self-organized InxAl1-xAs/InyAl1-yAs SLs was attributed to the strain-mediated surface segregation process during MBE growth of In0.52Al0.48As alloy. (C) 2005 Published by Elsevier Ltd.

来自易变山羊草抗禾谷孢囊线虫基因的克隆与序列分析

禾谷孢囊线虫（Heterodera avenae）是严重危害禾谷类作物的病原线虫之一,它广泛分布于澳大利亚、欧洲、北美、印度和中国等世界主要小麦产区,使作物严重减产,造成巨大的经济损失。目前最有效的防治措施之一是将外源抗性基因导入栽培小麦(Triticum aestivum L.)，培育抗禾谷孢囊线虫的新品种。但迄今为止抗禾谷孢囊线虫基因克隆研究的相关报道却很少。 本实验根据此前从抗禾谷孢囊线虫材料E-10扩增得到的与来自节节麦（Aegilops tauschii）的抗禾谷孢囊线虫基因Cre3高度同源的序列Rccn4,设计出三条嵌套引物,采用SON-PCR(single oligonucleotide nested PCR)方法,从E-10基因组DNA中得到一个长为1264 bp的扩增产物(命名为Rccn-L),测序比对结果显示,这一序列将Rccn4的3’端延伸了1209 bp,与抗禾谷孢囊线虫Cre3基因核苷酸同源性为86﹪，核苷酸编码区长1026 bp，含一个不完整的开放阅读框,一个终止密码子，没有起始密码子和内含子结构,编码一个342个氨基酸残基的蛋白质。该蛋白质等电点为5.19，分子量为38112.6Da。从序列的第113位开始到第332位是NBS-LRR类抗病性基因LRR区,呈现XXLXXLXXL重复。LRR编码区内亮氨酸残基的含量达17﹪，与抗禾谷孢囊线虫Cre3基因LRR编码区的核苷酸和氨基酸同源性分别为89﹪和78﹪。本实验首次将SON-PCR成功地运用于植物基因克隆，为植物基因克隆提供了又一有效方法。 此外,还根据Cre3基因及其他的NBS-LRR类植物抗性基因的NBS和LRR区保守序列设计了两对特异性引物，从禾谷孢囊线虫抗性材料易变山羊草基因组DNA中扩增到两个相应的目标条带。测序分析结果表明，它们的长度分别为532bp和1175bp，构成了一个有32bp的共同序列的NBS-LRR编码区。其序列总长为1675bp（命名为RCCN），含有一个不完整的开放阅读框，没有起始密码子、终止密码子和内含子结构。其中编码序列为1673bp，可编码一个557个氨基酸的蛋白质，等电点（pI）为5.39，分子量为63537.5Da。与Cre3的核苷酸和氨基酸同源性分别为87.8﹪和77﹪。RCCN氨基酸序列中含有已知抗病基因NBS区域的几个保守模体：kinase2区的ILDD、kinase3的（ⅰ）ESKILVTTRSK，（ⅱ）KGSPLAARTVGG，（ⅲ）RRCFAYCS及EGF。RCCN NBS区与Cre3 NBS区的核苷酸和氨基酸的同源性分别为96.4﹪和94﹪。从氨基酸序列的274位到548位为LRR保守区，呈现不规则的aXXLXXLXXL（其中a代表I，V，L，F或M）重复，其中亮氨酸的含量为15.6﹪。该区域与Cre3的LRR区的核苷酸和氨基酸同源性分别为80.8﹪和74﹪。推测该序列可能为一个抗禾谷孢囊线虫的新基因。 本文对抗禾谷孢囊线虫基因的克隆研究，为进一步克隆基因全序列，探索其结构与功能，和研究该基因表达与调控提供了关键信息。同时也为通过基因工程途径将抗性基因向优良小麦品种高效、定向转移，最终培育出小麦抗禾谷孢囊线虫新品种奠定了基础。 Cereal cyst nematode (CCN) is a damaging pathogen of broad acre cereal crops in Australia, Europe, North America, India and China. It affects wheat, barley, oat and triticale and causes yield loss of up to 80%. At present, Transferring resistance genes against CCN into wheat cultivars and breeding varieties are considered one of the most effective methods for controlling the CCN. However, there are very limited reports concerning the cloning studies of resistance genes against the cereal cyst nematode. According to the sequence of Rccn4 which had high similarity to the nucleotide binding site (NBS) coding region of cereal cyst nematode resistance gene, Cre3， We designed three 3’ nested primers. Using single oligonucleotide nested PCR (SON-PCR) we successfully amplified one band, Rccn-L, of 1264bp from E-10 which is the wheat-Ae.variabilis translocation line containing the cereal cyst nematode resistance gene of Ae.variabilis. We found that this band of interesting is the 3’ flanking sequence of 1209bp in size of Rccn4. The coding region was 1026bp, which contained an incomplete open reading frame and a terminator codon, without initiation codon and intron, encoding a peptide of 342 amino acid residues, and shared 86﹪nucleotide sequence identity with Cre3. This peptide had a conserved LRR domain, containing the imperfect repeats,XXLXXLXXL, which contains 17﹪ leucine residues and shares, respectively, 89﹪ nucleotide sequence and 78﹪ amino acid sequence identity with the LRR sequence of Cre3 locus. This research firstly used SON-PCR in the research of plant genome successfully, which indicated that SON-PCR is another method of cloning plant gene. At the same time, According to the conversed motif of NBS and LRR region of cereal cyst nematode resistance gene Cre3 from wild wheat (Triticum tauschlii L.) and the known NBS-LRR group resistance genes, we designed two pairs of specific primers for NBS and LRR region respectively. One band of approximately 530bp was amplified using the specific primers for conversed NBS region and one band of approximately 1200bp was amplified with the specific primers for conversed LRR region. After sequencing, we found that these two sequences included 32bp common nucleotide sequence and have 1675 bp in total, which was registered as RCCN in the Genbank. RCCN contained a NBS-LRR domain and an incomplete open reading frame without initiation codon, terminator codon and inxon. Its exon encodes a peptide of 557 amino acid residues. The molecular weight of the protein from the amino acid was 63.537 KDa. The amino acid sequence of RCCN contained conserved motif: ILDD, ESKILVTTRSK, KGSPLAARTVGG, RRCFAYCS, EGF，LRR. RCCN shares 87.8﹪ nucleotide sequence and 77﹪ amino acid sequence identity with cereal cyst nematode gene Cre3. It might be a novel cereal cyst nematode resistance gene. These research results of cloning the resistance genes against cereal cyst nematode bring a great promise for transferring resistance genes into wheat cultivars and breeding new wheat varieties against cereal cyst nematode by gene engineering. And these results also lay the hard foundation for the expressing researches of these genes.

Determination of ultra-trace concentrations of elements in high purity tellurium by inductively coupled plasma mass spectrometry after Fe(OH)(3) coprecipitation

In this work, a method was established for the determination of impurities in high purity tellurium by inductively coupled plasma mass spectrometry (ICP-MS) after Fe(OH)(3) coprecipitation. After comparison of coprecipitation ability and separation efficiency between Fe(OH), and Al(OH)(3), Fe(OH)(3) was chosen as the precipitate. A separation factor of 160 for 200 mg tellurium was obtained under conditions of pH 9 and 2 mg of Fe3(+). The 13 elements, such as Bi, Sn, Pb, In, Tl, Cd, Cu, Co, Ni, Zn, Ti, Be and Zr, could be almost completely coprecipitated under these conditions. In addition, Te memory effect imposed on the ICP-MS instrument was assessed, as well as Te matrix effect that caused the low recovery of Ga, As, Sb and V in real sample was discussed. Finally, the method was evaluated through recovery test and was applied to practical sample analysis, with detection limits of most of the elements being below 0.15 mug g(-1) and R.S.D. below or at approximately 10%, which indicated that this method could fully satisfy the requirements for analysis of 99.999% similar to 99.9999% high purity Te.

Hábitos de Sono em estudantes universitários

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências Farmacêuticas

Monte Carlo Analysis and Physics Characterization of a Novel Nanoparticle Detector for Medical and Micro-dosimetry Applications

The outcomes for both (i) radiation therapy and (ii) preclinical small animal radio- biology studies are dependent on the delivery of a known quantity of radiation to a specific and intentional location. Adverse effects can result from these procedures if the dose to the target is too high or low, and can also result from an incorrect spatial distribution in which nearby normal healthy tissue can be undesirably damaged by poor radiation delivery techniques. Thus, in mice and humans alike, the spatial dose distributions from radiation sources should be well characterized in terms of the absolute dose quantity, and with pin-point accuracy. When dealing with the steep spatial dose gradients consequential to either (i) high dose rate (HDR) brachytherapy or (ii) within the small organs and tissue inhomogeneities of mice, obtaining accurate and highly precise dose results can be very challenging, considering commercially available radiation detection tools, such as ion chambers, are often too large for in-vivo use.

In this dissertation two tools are developed and applied for both clinical and preclinical radiation measurement. The first tool is a novel radiation detector for acquiring physical measurements, fabricated from an inorganic nano-crystalline scintillator that has been fixed on an optical fiber terminus. This dosimeter allows for the measurement of point doses to sub-millimeter resolution, and has the ability to be placed in-vivo in humans and small animals. Real-time data is displayed to the user to provide instant quality assurance and dose-rate information. The second tool utilizes an open source Monte Carlo particle transport code, and was applied for small animal dosimetry studies to calculate organ doses and recommend new techniques of dose prescription in mice, as well as to characterize dose to the murine bone marrow compartment with micron-scale resolution.

Hardware design changes were implemented to reduce the overall fiber diameter to <0.9 mm for the nano-crystalline scintillator based fiber optic detector (NanoFOD) system. Lower limits of device sensitivity were found to be approximately 0.05 cGy/s. Herein, this detector was demonstrated to perform quality assurance of clinical 192Ir HDR brachytherapy procedures, providing comparable dose measurements as thermo-luminescent dosimeters and accuracy within 20% of the treatment planning software (TPS) for 27 treatments conducted, with an inter-quartile range ratio to the TPS dose value of (1.02-0.94=0.08). After removing contaminant signals (Cerenkov and diode background), calibration of the detector enabled accurate dose measurements for vaginal applicator brachytherapy procedures. For 192Ir use, energy response changed by a factor of 2.25 over the SDD values of 3 to 9 cm; however a cap made of 0.2 mm thickness silver reduced energy dependence to a factor of 1.25 over the same SDD range, but had the consequence of reducing overall sensitivity by 33%.

For preclinical measurements, dose accuracy of the NanoFOD was within 1.3% of MOSFET measured dose values in a cylindrical mouse phantom at 225 kV for x-ray irradiation at angles of 0, 90, 180, and 270˝. The NanoFOD exhibited small changes in angular sensitivity, with a coefficient of variation (COV) of 3.6% at 120 kV and 1% at 225 kV. When the NanoFOD was placed alongside a MOSFET in the liver of a sacrificed mouse and treatment was delivered at 225 kV with 0.3 mm Cu filter, the dose difference was only 1.09% with use of the 4x4 cm collimator, and -0.03% with no collimation. Additionally, the NanoFOD utilized a scintillator of 11 µm thickness to measure small x-ray fields for microbeam radiation therapy (MRT) applications, and achieved 2.7% dose accuracy of the microbeam peak in comparison to radiochromic film. Modest differences between the full-width at half maximum measured lateral dimension of the MRT system were observed between the NanoFOD (420 µm) and radiochromic film (320 µm), but these differences have been explained mostly as an artifact due to the geometry used and volumetric effects in the scintillator material. Characterization of the energy dependence for the yttrium-oxide based scintillator material was performed in the range of 40-320 kV (2 mm Al filtration), and the maximum device sensitivity was achieved at 100 kV. Tissue maximum ratio data measurements were carried out on a small animal x-ray irradiator system at 320 kV and demonstrated an average difference of 0.9% as compared to a MOSFET dosimeter in the range of 2.5 to 33 cm depth in tissue equivalent plastic blocks. Irradiation of the NanoFOD fiber and scintillator material on a 137Cs gamma irradiator to 1600 Gy did not produce any measurable change in light output, suggesting that the NanoFOD system may be re-used without the need for replacement or recalibration over its lifetime.

For small animal irradiator systems, researchers can deliver a given dose to a target organ by controlling exposure time. Currently, researchers calculate this exposure time by dividing the total dose that they wish to deliver by a single provided dose rate value. This method is independent of the target organ. Studies conducted here used Monte Carlo particle transport codes to justify a new method of dose prescription in mice, that considers organ specific doses. Monte Carlo simulations were performed in the Geant4 Application for Tomographic Emission (GATE) toolkit using a MOBY mouse whole-body phantom. The non-homogeneous phantom was comprised of 256x256x800 voxels of size 0.145x0.145x0.145 mm3. Differences of up to 20-30% in dose to soft-tissue target organs was demonstrated, and methods for alleviating these errors were suggested during whole body radiation of mice by utilizing organ specific and x-ray tube filter specific dose rates for all irradiations.

Monte Carlo analysis was used on 1 µm resolution CT images of a mouse femur and a mouse vertebra to calculate the dose gradients within the bone marrow (BM) compartment of mice based on different radiation beam qualities relevant to x-ray and isotope type irradiators. Results and findings indicated that soft x-ray beams (160 kV at 0.62 mm Cu HVL and 320 kV at 1 mm Cu HVL) lead to substantially higher dose to BM within close proximity to mineral bone (within about 60 µm) as compared to hard x-ray beams (320 kV at 4 mm Cu HVL) and isotope based gamma irradiators (137Cs). The average dose increases to the BM in the vertebra for these four aforementioned radiation beam qualities were found to be 31%, 17%, 8%, and 1%, respectively. Both in-vitro and in-vivo experimental studies confirmed these simulation results, demonstrating that the 320 kV, 1 mm Cu HVL beam caused statistically significant increased killing to the BM cells at 6 Gy dose levels in comparison to both the 320 kV, 4 mm Cu HVL and the 662 keV, 137Cs beams.

Effects of the novel (Pro(3))GIP antagonist and exendin(9-39)amide on GIP- and GLP-1-induced cyclic AMP generation, insulin secretion and postprandial insulin release in obese diabetic (ob/ob) mice: evidence that GIP is the major physiological incretin

AIMS/HYPOTHESIS: This study examined the biological effects of the GIP receptor antagonist, (Pro3)GIP and the GLP-1 receptor antagonist, exendin(9-39)amide.

METHODS: Cyclic AMP production was assessed in Chinese hamster lung fibroblasts transfected with human GIP or GLP-1 receptors, respectively. In vitro insulin release studies were assessed in BRIN-BD11 cells while in vivo insulinotropic and glycaemic responses were measured in obese diabetic ( ob/ ob) mice.

RESULTS: In GIP receptor-transfected fibroblasts, (Pro(3))GIP or exendin(9-39)amide inhibited GIP-stimulated cyclic AMP production with maximal inhibition of 70.0+/-3.5% and 73.5+/-3.2% at 10(-6) mol/l, respectively. In GLP-1 receptor-transfected fibroblasts, exendin(9-39)amide inhibited GLP-1-stimulated cyclic AMP production with maximal inhibition of 60+/-0.7% at 10(-6) mol/l, whereas (Pro(3))GIP had no effect. (Pro(3))GIP specifically inhibited GIP-stimulated insulin release (86%; p<0.001) from clonal BRIN-BD11 cells, but had no effect on GLP-1-stimulated insulin release. In contrast, exendin(9-39)amide inhibited both GIP and GLP-1-stimulated insulin release (57% and 44%, respectively; p<0.001). Administration of (Pro(3))GIP, exendin(9-39)amide or a combination of both peptides (25 nmol/kg body weight, i.p.) to fasted (ob/ob) mice decreased the plasma insulin responses by 42%, 54% and 49%, respectively (p<0.01 to p<0.001). The hyperinsulinaemia of non-fasted (ob/ob) mice was decreased by 19%, 27% and 18% (p<0.05 to p<0.01) by injection of (Pro3)GIP, exendin(9-39)amide or combined peptides but accompanying changes of plasma glucose were small.

CONCLUSIONS/INTERPRETATION: These data show that (Pro(3))GIP is a specific GIP receptor antagonist. Furthermore, feeding studies in one commonly used animal model of obesity and diabetes, (ob/ob) mice, suggest that GIP is the major physiological component of the enteroinsular axis, contributing approximately 80% to incretin-induced insulin release.

Delayed failure of a deep cutting in lodgement till

Recent research on the delayed failure of cuttings in clay clearly recognises and predicts progressive delayed failure of deep cuttings. This is due to a combination of strain-softening, weathering, dissipation of negative excess pore water pressure generated at the time of excavation, and frequent occurrence of prolonged periods of wet weather. There have been several slope failures of this kind in Northern Ireland. This paper discusses a case study based on a failure of a deep cutting, excavated at a slope of 1 in 2, on the A1 near Dromore (County Down) in Northern Ireland. The cutting was in lodgement till, a stiff, heavily overconsolidated clay. The failure occurred approximately 30 years after the cutting was excavated, following a prolonged period of heavy rainfall. An analysis of the failure, together with laboratory test data on soil samples taken from the site, confirmed that by using long-term soil strength parameters the factor of safety of this slope was unity. The conclusion of the analysis is that slopes excavated in this soil should be designed (and assessed) on long-term strength parameters.

The purification and properties of phosphonoacetate hydrolase, a novel carbon-phosphorus bond-cleavage enzyme from Pseudomonas fluorescens 23F

A novel, inducible, carbon-phosphorus bond-cleavage enzyme, phosphonoacetate hydrolase, was purified from cells of Pseudomonas fluorescens 23F grown phosphonoacetate. The native enzyme had a molecular mass of approximately 80 kDa and, upon SDS/PAGE, yielded a homogenous protein band with an apparent molecular mass of about 38 kDa. Activity of purified phosphonoacetate hydrolase was Zn2+ dependent and showed pH and temperature optima of approximately 7.8 and 37 degrees C, respectively. The purified enzyme had an apparent K-m of 1.25 mM for its sole substrate phosphonoacetate, and was inhibited by the structural analogues 3-phosphonopropionate and phosphonoformate. The NH2-terminal sequence of the first 19 amino acids displayed no significant similarity to other databank sequences.

The role of Na surface species on oxygen charge transfer in the Pt/YSZ system

The role of sodium surface species in the modification of a platinum (Pt) catalyst film supported on 8 mol% yttria-stabilised-zirconia (YSZ) was investigated under a flow of 20 kPa oxygen at 400 °C. Cyclic and linear sweep voltammetry were used to investigate the kinetics of the oxygen charge transfer reaction. The Pt/YSZ systems of both ‘clean’ and variable-coverage sodium-modified catalyst surfaces were also characterised using SEM, XPS and work function measurements using the Kelvin probe technique.

Samples with sodium coverage from 0.5 to 100% were used. It was found that sodium addition modifies the binding energy of oxygen onto the catalyst surface. Cyclic voltammetry experiments showed that higher overpotentials were required for oxygen reduction with increasing sodium coverage. In addition, sodium was found to modify oxygen storage and/or adsorption and diffusion increasing current densities at higher cathodic overpotential. Ex situ XPS measurements showed the presence of sodium hydroxide, carbonate and/or oxide species on the catalyst surface, while the Kelvin probe technique showed a decrease of approximately 250 meV in the work function of samples with more than 50% sodium coverage (compared to a nominally ‘clean’ sample).