To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The interest in the phenomenon of islanding in a range of semiconductor systems is in part due to the fundamental importance of the Stranski-Krastanow transition but also driven by potential device applications of self-organized quantum dot arrays. However, the mechanism underlying the island formation is still to a significant degree unclear. In the present work, we focus on the epitaxial InGaAs / GaAs(001) system, with layer deposition by molecular beam epitaxy. Atomic force microscopy is used to measure the surface topography of nominally 4nm thick InxGa1-xAs films. It is shown that the growth mode switches abruptly from flat layer to island growth if a critical Indium composition of x(In)≍0.25 is reached. The structure of such layers during early stages of growth is examined using energy-filtered transmission electron microscopy. Indium gradients in the islanded layers are measured and the driving force for the islanding transition itself is considered.
Gaia will only achieve its unprecedented measurement accuracy requirements with detailed
calibration and correction for radiation damage. We present our Silvaco 3D engineering
software model of the Gaia CCD pixel and two of its applications for Gaia: (1) physically
interpreting supplementary buried channel (SBC) capacity measurements (pocket-pumping and
first pixel response) in terms of e2v manufacturing doping alignment tolerances; and (2)
deriving electron densities within a charge packet as a function of the number of
constituent electrons and 3D position within the charge packet as input to microscopic
models being developed to simulate radiation damage.
Photocurrent spectroscopy of InAs/GaAs self-assembled quantum dots, studied as a function of applied electric field, is used to probe the nature of the confined electronic states. A field asymmetry of the quantum confined Stark effect is observed, consistent with the dots possessing a permanent dipole moment. The sign of this dipole indicates that for zero field the hole wavefunction lies above that of the electron, in disagreement with the predictions of all recent calculations. Comparison with a theoretical model demonstrates that the experimentally determined alignment of the electron and hole can only be explained if the dots contain a nonzero and non-uniform Ga content. The role of two different carrier escape mechanisms, tunneling and thermal excitation, is studied.
Here we describe preliminary research into the in situ electrokinetic generation of continuous iron-rich precipitates to act as sub-surface barriers for the containment of contaminated sites. This is achieved using sacrificial iron electrodes emplaced either side of a soil/sediment mass to introduce iron into the system, and their dissolution and re-precipitation under the influence of an applied (DC) electric field. Continuous vertical and horizontal iron-rich bands (up to 2 cm thick) have been generated over a timescale of 300—500 h, at voltages of <5 V with an electrode separation of between 15 and 30 cm. The thickness of the iron-rich band increases as the applied voltage is increased. Geotechnical tests in sand indicate that the iron-rich band produced is practically impervious (coefficient of permeability of 10—9 ms—1 or less), and has significant mechanical strength (unconfined compressive strength of 10.8 N mm—2). By monitoring the current, the integrity of the iron-rich band may be assessed, and by continued application of current, the barrier may 'self heal'. The iron-rich barrier is composed of amorphous iron, goethite, lepidocrocite, maghemite and native iron.
As a signatory of the Convention on Biological Diversity, the United Kingdom (UK) Government is obliged to conserve and enhance biodiversity. One step towards addressing this goal is to determine the level of biodiversity conservation already achieved within the current array of protected areas. We used national distribution data for ten taxonomic groups, and location information for three reserve networks, to assess the contribution of nature reserves to biodiversity conservation in Great Britain at the 10 km square (=100 km2) resolution. For several taxonomic groups, 10 km squares containing nature reserves had a significantly greater overlap than random networks with both hotspots (areas of high species richness) and complementary areas (sets of sites within which all species are represented). In addition, more than 94% of species from each taxonomic group have been recorded within the 10 km squares of the three reserve networks. These results provide some encouragement in terms of the UK meeting its commitment to conserve biodiversity.
Patients with chronic obstructive airways disease (COAD) or asthma who have a tracheostomy tube or tracheal stoma have difficulty using metered dose inhalers (MDIs) because of a failure to achieve a good seal between the tracheostomy tube or stoma and the MDI or spacer device mouthpiece. Many such patients therefore utilize nebulizers. MDIs in comparison to nebulizers have the advantages of being more compact, portable, easy to use, less time-consuming, and cheaper. We present the case of a 74-year-old man who underwent a laryngectomy with tracheal stoma formation who had a poor response with nebulizers and required oral steroids. He was subsequently, with the help of a number of attached devices, able to use his MDIs to good effect. We describe a number of devices and adaptors to enable patients with laryngectomy stomas or tracheostomy tubes to utilize MDIs and undergo respiratory function tests. We recommend that all such patients should have the benefit of a consultation with a dedicated respiratory nurse who can provide the appropriate MDIs, devices and adaptors to optimize the treatment of their lower respiratory tract condition.
This study is part of our effort to map recombination hotspots in two regions (site A, 18 kb; site B,
40 kb) of the human phosphoglucomutase PGM1 gene. Twenty-two PCR amplified fragments
comprising six groups, covering about 5.2 kb, were screened for single nucleotide polymorphisms
(SNPs) using non-isotopic single stranded conformation polymorphism (SSCP) analysis. Fourteen
fragments were variable and seven of these showed common polymorphism. Our strategy for
screening for polymorphic sites in the PGM1 gene was based on the results of allelic association
analysis between each new marker and the sites of the classical isozyme polymorphism (2/1 in exon
4 and +/− in exon 8). Samples from four populations (Caucasian, Chinese, Vietnamese and New
Guinean) were typed for each of the seven polymorphic markers. Between two and four common
alleles were found in each case, together with a few rare alleles. Co-dominant inheritance patterns
were demonstrated by family studies. The molecular basis of each new marker was determined by
direct sequencing of the PCR products: most were SNPs except two that were small
insertions/deletions. Direct sequence analysis of a 2.1 kb segment in sixteen individuals revealed no
additional nucleotide variation indicating a very high level of efficiency of the SSCP screening
method used in this study. The overall nucleotide diversity (θ) for PGM1 was estimated as 0.9×10−3
based on 33 segregating sites in a sequence of 5187 nt and a sample size of 614 individuals.
Phosphoglucomutase 1 (PGM1) deficiency is a stable characteristic
line, K562, whereas the activity of the isozymes of the other two PGM loci
(PGM2 and PGM3) is
slightly elevated. In this study the molecular basis of PGM1 deficiency
investigated by a
combined approach utilising protein electrophoresis, immunodetection,
cytogenetic techniques, and
DNA and RNA analysis. Isoelectric focusing and activity staining confirmed
that K562 has no
detectable PGM1 activity. Immunoblot analysis of extracts, separated by
isoelectric focusing, starch
gel and SDS gel electrophoresis, using monospecific anti-PGM1 antibodies
showed that K562
contained no detectable immunoreactive material. Karyotype analysis revealed
the presence of two
intact chromosomes 1 and a derivative chromosome 1,
der(1)t(1; 11), each of which carried a copy
of the PGM1 gene as demonstrated by fluorescence in situ
hybridization using a PGM1 cosmid as
probe. Southern blot analysis using a PGM1 cDNA clone as probe
that the PGM1 genes
had not been subject to any gross structural rearrangements. We were also
able to determine that K562 is type PGM1 2+1+
by restriction endonuclease analysis of genomic DNA. Very low levels
of PGM1 mRNA which appeared to be full length transcripts were detected
K562 using a reverse
transcriptase PCR technique. We conclude that the most likely cause of
enzyme deficiency in K562 is abnormal regulation of transcription.
An auto-antibody screen for SLE, which included anti-nuclear antibodies, was performed on 296 patients admitted to acute psychiatric and psychogeriatric wards. Three cases (1% of those screened) of previously undiagnosed SLE were found, and one patient was found to have autoimmune chronic active hepatitis. An auto-antibody screen may be a useful investigation in psychiatric practice.
The effect of covers of controlled volunteer vegetation, Pueraria phaseoloides, and clean weeding on the soil moisture content and on the succulence of sisal leaves was studied. The surface soil tended to dry out further when exposed by clean weeding, but moisture in the profile as a whole was not much depleted. The plant covers dried soils to at least 300 cm. in dry periods. Although sisal leaves had a slightly higher dry matter content in dry weather there was no evidence of competition for water between the plant covers and the sisal.
Sisal was grown in double rows with broad-interrow covers of Pueraria phaseoloides, controlled volunteer vegetation or clean weeding. Clean weeding gave the best yield over one cycle, but Pueraria cover was best in the second cycle. Pueraria was better than volunteer vegetation in all trials, with the greatest margin on soils low in nitrogen, or where there were pernicious weeds. On an exhausted soil, sisal with a Pueraria cover responded to fertilizer nitrogen applied in the early or late part of the cycle. Manuring sisal growing with a volunteer vegetation cover with 50 tons sisal waste/ha. improved growth to the same extent as replacing the cover with one of Pueraria. In the absence of manures, yields declined from cycle to cycle with all the covers. At the level of manuring which maintained yields with a volunteer vegetation cover, yields declined slightly with clean cultivation, and improved considerably with a Pueraria cover.
Experiments in bulbil nurseries and field sisal were carried out in N.E. Tanganyika, 5°S, 39°E, 200 m. above sea level, at a mean annual rainfall of 1160 mm., on deep red loam. The discussion covers the establishment of sisal through a polythene mulch, the control of weed growth, the persistence of polythene of different thicknesses and from different sources, and some effects on growth of the sisal and on soil properties. A mulch of black polythene improved the growth of bulbil nurseries by 30 per cent or more, due to conservation of soil moisture and elimination of weed competition and disturbance associated with the removal of weeds by hoeing. For nurseries 150-gauge material was preferred, but there were important differences in the persistence of material purchased from two sources. Where black polythene is used in a nursery the density can be increased from 80,000 to 110,000 plants per hectare, to help offset the high cost of the material. A mulch of 250-g. black polythene controlled weeds in field sisal but did not improve growth.
Email your librarian or administrator to recommend adding this to your organisation's collection.