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Arbuscular mycorrhizal fungi (AMF) can increase plant nutrient uptake and chemical defense production, both of which can improve plants’ ability to resist insect herbivory. Cover crops—non-commercial species planted in between cash crops in a crop rotation—can naturally alter both soil nutrients and AMF. We tested whether different cover crop species alter AMF colonization, plant nutrient status and plant–insect interactions in a subsequent maize crop. Cover crop species were either non-mycorrhizal, non-leguminous (canola, forage radish), mycorrhizal non-leguminous (cereal rye, oats), mycorrhizal leguminous (clover, pea) or absent (fallow). We measured the cascading consequences of cover crop treatment on maize root AMF colonization, maize growth and performance of an herbivorous insect (European corn borer) feeding on the maize. Maize AMF colonization was greater in plots previously planted with mycorrhizal (rye, oats) than non-mycorrhizal (canola, radish) cover crops or no cover crop (fallow). AMF colonization was linked to increased plant phosphorous and nitrogen, and maize growth increased with low plant N:P. Induced jasmonic acid pathway plant defenses increased with increasing maize growth and AMF colonization. European corn borer survivorship decreased with lower plant N:P, and insect development rate decreased with increased induced plant defenses. Our data describe a cascade in which cover crop species selection can increase or decrease mycorrhizal colonization of subsequent maize crop roots, which in turn impacts phosphorus uptake and may affect herbivory resistance in the maize. These results suggest that farmers could select cover crop species to manage nutrient uptake and pest resistance, in order to amend or limit fertilizer and pesticide use.
The transition from state socialism toward market capitalism has led to an almost endless supply of new laws and legal institutions. Industrial enterprises need to adapt to this new institutional regime. In-house lawyers are well placed to be agents of change in facilitating this adjustment. Using survey data from 328 Russian enterprises, the article examines the role of company lawyers, asking whether they have fulfilled this potential. Legal expertise is not in short supply, but lawyers are marginalized within the enterprise. They focus on established, routine tasks, such as handling labor relations or drafting form contracts, rather than on shaping enterprise strategies in the newer areas created by the transition, such as corporate governance or securities law. The failure of in-house lawyers to emerge as agents of change in Russia reflects a continuation of their low status during the Soviet era and the lack of professional identity among these company lawyers.
An experimental investigation into the mechanical behaviour of polycrystalline ice in triaxial compression has been conducted using conditions generally favourable to brittle fracture and microcracking. Under triaxial stresses at high strain rate, ice failure occurs by abrupt shear fracturing, generally inclined at about 45° to the maximum principal stress. At −20°C, such failure is suppressed by the imposition of a small confining pressure, allowing a transition to ductile-type flow accompanied by distributed microcracking, but at —40°C shear fracture persists under confinement of up to at least 50 MPa. For low confining pressures (< 10 MPa), brittle strength is strongly pressure-dependent; above this it is pressure-independent. Evidence is presented that suggests this may reflect a change from a fracture process influenced by friction to fracture initiated by localized yielding. Ductile yield strength is found to be little influenced by confining pressure despite the inhibition of cracking that leads to greatly contrasting observed crack densities. Flow conforms to the well-known power law for ice with Q = 69 J mol−1 and n = 4.2 over the temperature range −20° to −4-5° C Under these conditions, microcracking in ice appears to remain remarkably stable and non-interacting.
An experimental study of the fracture mechanics and rheology of ice from the Ronne Ice Shelf, Antarctica, is currently being undertaken. The apparent critical stress-intensity factor (or apparent fracture toughness, KQ) for crack propagation has been measured using a three-point bend method for inducing crack growth perpendicular to the axis of cylindrical ice-core specimens. Tensile crack nucleation under applied uniaxial compressive stress has also been evaluated. Both methods have allowed a profile of ice elastic and fracture properties with depth through the ice shelf to be constructed. Preliminary results indicate that the measured elastic modulus increases with depth through the firn and upper meteoric ice before reaching a constant value in the deeper, dense meteoric and basal marine ice. The resistance to fracture, as measured by changes in apparent fracture toughness and crack-nucleation stress, increases with depth right through the firn and meteoric ice layers. A simple fracture mechanics model applied to the Ronne Ice Shelf indicates that crevasses form from small surface cracks, less than 40 cm deep, which quickly grow to depths of 40–60m and then remain stable.
The subject of Surrender Values is a wide one and it will be impossible in the course of these remarks to give more than an outline of a few of the points which arise. I shall, therefore, deal in the main with broad general principles and leave the lesser details untouched.
The scales of surrender values actually allowed by offices in this country differ widely, and an examination of the figures indicates that some offices still retain the view that a policyholder who surrenders his assurance should be fined heavily. It is difficult to reconcile this view with present-day ideas, for if a policyholder is so unfortunate as to be unable to continue his premiums owing to financial or other reasons, it is surely harsh treatment on the part of the company to impose a heavy fine, the whole, or practically the whole, of which merely goes to swell the bonuses allotted to those more fortunate individuals who are able to continue and who could well dispense with this additional benefit.
There is little information on the association of the APOEe4 allele and AD risk in African populations. In previous analyses from the Indianapolis-Ibadan dementia project, we have reported that APOE ε4 increased the risk for Alzheimer's disease (AD) in African Americans but not in Yoruba. This study represents a replication of this earlier work using enriched cohorts and extending the analysis to include cognitive decline.
In this longitudinal study of two community dwelling cohorts of elderly Yoruba and African Americans, APOE genotyping was conducted from blood samples taken on or before 2001 (1,871 African Americans & 2,200 Yoruba). Mean follow up time was 8.5 years for African Americans and 8.8 years for Yoruba. The effects of heterozygosity or homozygosity of ε4 and of the possession of e4 on time to incident AD and on cognitive decline were determined using Cox's proportional hazards regression and mixed effects models.
After adjusting for covariates, one or two copies of the APOE ε4 allele were significant risk factors for incident AD (p < 0.0001) and cognitive decline in the African-American population (p < 0001). In the Yoruba, only homozygosity for APOE ε4 was a significant risk factor for AD (p = 0.0002) but not for cognitive decline (p = 0.2346), however, possession of an e4 allele was significant for both incident AD (p = 0.0489) and cognitive decline (p = 0.0425).
In this large longitudinal comparative study, APOE ε4 had a significant, but weaker, effect on incident AD and on cognitive decline in Yoruba than in African Americans. The reasons for these differences remain unclear.
High levels of homocysteine have been associated with increased risk for dementia although results have been inconsistent. There are no reported studies from the developing world including Africa.
In this longitudinal study of two community-dwelling cohorts of elderly Yoruba and African Americans, levels of homocysteine, vitamin B12 and folate were measured from blood samples taken in 2001. These levels were compared in two groups, participants who developed incident dementia in the follow-up until 2009 (59 Yoruba and 101 African Americans) and participants who were diagnosed as cognitively normal or in the good performance category at their last follow-up (760 Yoruba and 811 African Americans). Homocysteine levels were divided into quartiles for each site.
After adjusting for age, education, possession of ApoE, smoking, and time of enrollment the higher quartiles of homocysteine were associated with a non-significant increase in dementia risk in the Yoruba (homocysteine quartile 4 vs. 1 OR: 2.19, 95% CI 0.95–5.07, p = 0.066). For the African Americans, there was a similar but non-significant relationship between higher homocysteine levels and dementia risk. There were no significant relationships between levels of vitamin B12 and folate and incident dementia in either site although folate levels were lower and vitamin B12 levers were higher in the Yoruba than in the African Americans.
Increased homocysteine levels were associated with a similar but non-significant increase in dementia risk for both Yoruba and African Americans despite significant differences in folate levels between the two sites.
The aim of this review paper is to consider how the principles of clinical audit could be applied to the development of an audit of nutritional care in hospitals and care homes, based on criteria derived from the Essence of Care: Food and Drink. A literature review identified fifteen key papers that included guidance or standards for nutritional care in hospitals or care homes. These were used to supplement the ten factors suggested by the Essence of Care to develop a set of potential audit criteria covering all aspects of the nutritional care pathway including the identification of risk of malnutrition, implementation of nutritional care plans, referral to healthcare professionals for further nutritional assessment and nutritional support strategies. A series of audit tools have been developed, including an organisational level audit tool, a staff questionnaire, a patients' and residents' records audit tool and a patients' and residents' experiences questionnaire. Further issues to consider in designing a national nutritional audit include the potential role of direct observation of care, the use of trained auditors and the scope for including the results of pre-existing local audits. In conclusion, a national audit would need to encompass a very large number of health and care organisations of widely varying sizes and types and a diverse range of people.
Boron is the most important p-type dopant in Si and it is essential that, especially for low energy implantation, both as-implanted B distributions and those produced by annealing should be characterized in very great detail to obtain the required process control for advanced device applications. While secondary ion mass spectrometry (SIMS) is ordinarily employed for this purpose, in the present studies implant concentration profiles have been determined by direct B imaging with approximately nanometer depth and lateral resolution using energy-filtered imaging in the transmission electron microscopy. The as-implanted B impurity profile is correlated with theoretical expectations: differences with respect to the results of SIMS measurements are discussed. Changes in the B distribution and clustering that occur after annealing of the implanted layers are also described.
Boron is the most important p-type dopant in Si and it is essential that,
especially for low energy implantation, both as-implanted B distributions
and those produced by annealing should be characterized in very great detail
to obtain the required process control for advanced device applications.
While secondary ion mass spectrometry (SIMS) is ordinarily employed for this
purpose, in the present studies implant concentration profiles have been
determined by direct B imaging with approximately nanometer depth and
lateral resolution using energy-filtered imaging in the transmission
electron microscopy. The as-implanted B impurity profile is correlated with
theoretical expectations: differences with respect to the results of SIMS
measurements are discussed. Changes in the B distribution and clustering
that occur after annealing of the implanted layers are also described.
Ionising radiations have been observed to produce significant improvements in thin film adhesion by several experimental groups. We present the results of an exhaustive and conclusive series of experiments on the effect of clean processing and heavy ion irradiation on the adhesion of metal films to substrates of silicon and tantalum. The experiments were performed in a unique research-scale Ultra High Vacuum Cluster tool, to gain control of the all important surface and interface compositions.
Our results show that adhesion is greatest for films deposited on atomically clean surfaces. Such films adhere better than conventionally deposited films subjected to a post deposition irradiation treatment. Clean processed samples show no benefit from subsequent radiation processing. Our results are consistent with the radiation enhanced adhesion phenomenon being due to the radiolysis of interfacial contaminant layers, producing an interface with lower interfacial energy and hence better bonding. Where adhesion enhancement is observed, the process is consistent with a semi-empirical model of the process using an activation energy of some 5 eV per atom.
We have investigated the effect on a silicon surface of both wet chemical and cluster-tool UV/ozone cleaning, prior to UHV processing to fabricate MOS test structures. The physical and chemical condition of the Si surface has been examined by Scanning Tunnelling and Atomic Force Microscopy (STM, AFM) and Medium Energy Ion Scattering (MEIS). After MOS fabrication some of the structures were examined by Cross-sectional Transmission Electron Microscopy (TEM). The electrical performance of the MOS test sets were characterized by breakdown voltage measurements.
We have found correlations between the electrical performance of the MOS devices, the structure of the Si surface prior to oxidation, and the details of the UHV fabrication technique. In particular any MOS device fabricated on a Si surface thermally cleaned in UHV prior to oxidation has a poor breakdown strength. We have found that this is the result of the formation of silicon carbide on the Si surface at high temperature and the subsequent local disruption of the oxidation step of MOS fabrication by the SiC. A UHV cleaning procedure has been developed to avoid this C contamination problem.
The characteristics of the HF-treated Si-surface are investigated as a function of dipping time in dilute HF solutions. It is found that the contact angle is a very sensitive measure for the degree of oxidation of the Si-surface. The importance of obtaining a perfectly passivated surface in order to reduce the particle deposition on the surface is shown. HF-last cleans are found to be beneficial in terms of metallic contamination and gate oxide integrity. The importance of the loading ambient in furnaces is investigated after HF-treatments and RCA-cleans.
Surface spectroscopic techniques have been used to investigate aluminium deposition form tri-methyl aluminium (TMA) on Si(100), and the etching of InP by chlorine. Thermal reactions and processes stimulated by UV lamps and ion beams are examined. The results are interpreted in the light of the adsorption states which are formed and the surface transformations of chemical states which are observed to occur.
The use of Conducting Probe Atomic Force Microscopy to give nm scale electronic characterisation of surfaces is reviewed. Local conductance, Kelvin Probe work function measurements, Fowler-Nordheim tunnelling and local C-V characterisation techniques are outlined. The principle results of these and their applications to the semiconductor surface and thin film characterisation are discussed. We present tunnelling data from silicon through varying oxide thickness using conducting AFM and scanning Kelvin Probe measurements from sub micron MOS capacitors. The F-N tunnelling technique has also been used on epitaxial silicon surfaces with atomically flat topography.
The inherent problems associated with quantitative, reproducible measurements are outlined, and the potential applications of the measurements to surface and thin film technology are discussed.
As the drive towards the production of 100 nm CMOS devices pick up speed, the practical aspect of transistor shallow junction formation, including a large menu of process integration issues, must now be solved in a short order. The most direct path to 50 nm junction depths is through the sub-keV boron implantation and rapid thermal annealing.
The material aspects of the process integration centers on: (1) CMOS devices for shallow, highly-activated and abrupt junctions (involving the choice of ion species [B, BF, B10H14, BSi2, etc.], substrate materials [ Cz, Epi, SOI], anneal conditions [ramp rate, soak time, ambient gas], etc.) and (2) Defect-dopant interactions during annealing (including surface reactions of high concentration species [B, F], diffusion and carrier trapping by background and co-implanted species [C, 0, F, etc.].
Process data for atomic and electrical activity profiles as well as defect and interface structures will be presented to illustrate progress towards understanding these complex process interactions. A particular focus will be the effects of anneal ambient and rapid temperature rise times approaching the “pike” anneal ideal.
The effects of ramp-up rate during rapid thermal processing of ultra-shallow boron implants have been investigated. Ramp-up rates were varied between 25 °C and 200 °C for two types of anneals: soak anneals and spike anneals. It was found that the ramp-up rate had very little influence on junction depth or electrical activation for both types of anneals. Spike anneals did produce shallower profiles than soak anneal for a comparable electrical activation and may be an option for future processes.