Search

Animals often rely on the presence of multiple, spatially segregated cover types to satisfy their ecological needs; the juxtaposition of these cover types is called landscape complementation. In ecosystems that have been homogenized because of human land use, such as fire‐suppressed forests, management activities have the potential to increase the heterogeneity of cover types and, therefore, landscape complementation. We modeled changes to California spotted owl (Strix occidentalis occidentalis) nesting/roosting habitat, foraging habitat and habitat co‐occurrence (i.e. landscape complementation) within a 971 245‐ha forest landscape restoration project area, the Tahoe‐Central Sierra Initiative (TCSI) landscape, through mid‐century as a function of fuels reduction, fire and climate change. Compared to a minimal management scenario, accelerated management within the TCSI landscape was predicted to increase the number of potential 400‐ha spotted owl territories containing a high degree of landscape complementation (defined as containing >20% nest/roost habitat and >20% foraging habitat) at lower elevations (<5000 ft.) by an average of 90 to 118 territories by 2050, depending on the climate scenario examined. At higher elevations (>5000 ft.), potential benefits of treatments to spotted owl nesting/roosting and foraging habitat were less evident, but accelerated management did not result in habitat loss. Our results suggest that accelerated fuels reduction and forest restoration treatments within this large landscape are expected to benefit spotted owls by improving the spatial juxtaposition of nesting/roosting and foraging cover types by 2050 compared to a minimal management scenario. Fuels reduction and forest restoration in this landscape thus can both increase the resilience of forest ecosystems to disturbances as well as benefit the habitat of a sensitive old‐forest species. [ABSTRACT FROM AUTHOR]

Climate change and a long legacy of fire suppression are leading to an increased prevalence of 'mega‐disturbances' such as drought and wildfire in terrestrial ecosystems. Evidence for the immediate effects of these novel disturbances on wildlife is accumulating, but little information exists on longer term impacts to species and ecosystems. We studied the occurrence dynamics of an iconic old‐forest species, the spotted owl (Strix occidentalis), on a long‐term study area in the Sierra Nevada, CA, USA from 1989 to 2020 to evaluate their multi‐scale population response following a 2014 megafire (the 'King' Fire) that affected a portion of our study area. We found that extensive severe fire within spotted owl sites resulted in both immediate site abandonment and prolonged lack of re‐colonization by owls six years post‐fire. Sites that experienced high pyrodiversity – a mosaic of burn severities – were more likely to persist after the fire, but this effect was only apparent at finer spatial scales. A potentially confounding factor, post‐fire salvage logging, did not explain variability in the probability of either owls persisting at sites or sites becoming re‐colonized; effects could be attributed only to severe fire extent and pyrodiversity. Our study demonstrates the prolonged effects of severe fire on the occupancy of this forest‐dependent species, suggesting that forest restoration that reduces megafires could benefit spotted owls. Our work emphasizes that long‐term monitoring can offer surprising learning opportunities and provide unparalleled value for understanding and addressing emerging environmental concerns. [ABSTRACT FROM AUTHOR]

A significant increase in treatment pace and scale is needed to restore dry western US forest resilience owing to increasingly frequent and severe wildfire and drought. We propose a pyrosilviculture approach to directly increase large-scale fire use and modify current thinning treatments to optimize future fire incorporation. Recommendations include leveraging wildfire's "treatment" in areas burned at low and moderate severity with subsequent pyrosilviculture management, identifying managed wildfire zones, and facilitating and financing prescribed fire with "anchor," "ecosystem asset," and "revenue" focused thinning treatments. Pyrosilviculture would also expand prescribed-burn and managed-wildfire objectives to include reducing stand density, increasing forest heterogeneity, and selecting for tree species and phenotypes better adapted to changing climate and disturbance regimes. The potential benefits and limitations of this approach are discussed. Fire is inevitable in dry western US forests and pyrosilviculture focuses on proactively shifting more of that fire into managed large-scale burns needed to restore ecosystem resilience. [ABSTRACT FROM AUTHOR]

We propose and demonstrate an enhancement-mode AlxGa1-xAs/GaAs single heterojunction field-effect transistor, in which the gate dielectric consists of an epitaxial AlxGa1-xAs layer and spin-on benzocyclobutene. The as-grown sample is undoped and, as a result, nonconductive at 4.2 K. However, under a positive gate bias, high mobility two-dimensional electrons at the heterointerface are induced, as evidenced by magnetotransport characteristics. Numerical simulations of a model structure provide insight into applications in mesoscopic devices. [ABSTRACT FROM AUTHOR]

Arid and semi-arid environments are characterized by extreme fluctuations in temperature and low rainfall, which present significant challenges to the animals inhabiting these areas. However, the presence of burrows may allow animals to avoid climatic extremes and predators and may act as valuable foraging sites. We assessed the microhabitat conditions (maximum and minimum temperature, relative humidity and seed abundance) of aardvark (Orycteropus afer) burrows in relation to paired non-burrow areas at three sites in South Africa. We also describe the extent to which they are used as resources by other vertebrates. Maximum temperatures were significantly lower and minimum temperatures and relative humidity values were significantly higher inside the burrows than outside. The concentration of seeds inside the burrows and at the paired non-burrow sites was similar. Twenty-seven vertebrate species (21 mammals, two birds, three reptiles and one amphibian) were recorded making use of the burrows and it is likely that these species accrue benefits (e.g. a buffered microclimate) from burrow use. However, our sampling was biased towards mammals and nocturnal species. Consequently, we recommend further work to establish the overall reliance of vertebrate taxa on aardvark burrows in arid and semi-arid environments. [ABSTRACT FROM AUTHOR]

In this paper we discuss a case study investigating how the academic and personal development of first year students on an undergraduate sports education degree can be supported and enhanced with mobile SMS communication. SMS-based technologies were introduced in response to students' particular needs (in transition to Higher Education) and characteristics ('digital natives'). Despite being unaccustomed to using their mobile phones for academic study, students willingly participated in SMS communication with their tutor via a texting management service. Drawing on evidence from two student surveys, focus groups and a tutor's journal, we illustrate the potential that mobile SMS communication has to link and establish continuity between face to face teaching sessions and online learning activities in the Virtual Learning Environment (VLE). Many students perceived the SMS communication to have had a positive impact on their management of study time. We link our findings with the existing literature and argue that mobile text based communication has the potential to support the development of time management skills, an important component of self regulatory learning, a skill which has been shown to be key in making a successful transition. [ABSTRACT FROM AUTHOR]

Bushclumps are scattered islands of thicket-like vegetation within a matrix of more open vegetation. We investigated the role of bushclumps as refugia for small mammals, and examined the effect of a limited number of abiotic and biotic factors on their richness, diversity and abundance. Small mammals were surveyed using Sherman small mammal traps at two sites in the Eastern Cape Province, South Africa (Mountain Zebra National Park and Kwandwe Private Game Reserve). Soil hardness and seed abundance, inside and outside bushclumps, were determined. Trap success was significantly higher inside bushclumps than in areas outside, and species diversity and the abundance of small mammals were greater within bushclumps compared to outside. Bushclumps also had significantly softer soil and a higher concentration of seeds. We conclude that bushclumps provide a concentrated source of food and protection from predators for small mammals, and are thus used significantly more than adjacent open areas. The conservation of bushclumps is therefore important for the overall maintenance of ecosystem functioning. [ABSTRACT FROM AUTHOR]

This paper estimates the financial incentive to control paratuberculosis on dairy farms by establishing the level of expenditure that would minimise the total cost of the disease (output losses plus control expenditure). Given the late onset of the clinical signs and the lack of treatments, control was focused on minimising the financial impact of paratuberculosis by adjusting the dairy cow replacement policy. The optimum replacement policies for disease-free herds and infected herds were compared by using dynamic programming. At the standard settings, the disease justified adjusting the culling policy; under constant bioeconomic assumptions, it reduced the expected annuity from milk production under the optimal replacement policy by about 10 per cent (£27 per cow annually), a considerably lower figure than for other major endemic diseases that affect dairy cows in the UK. The effect was even less at lower milk prices, suggesting that there is at present little incentive for dairy farmers to put more resources into controlling the disease. However, the incentive could be increased if more information were available about how best to manage the disease under specific farm circumstances. Any effect that paratuberculosis may have on the future demand for milk and hence on milk prices would also be an important consideration. [ABSTRACT FROM AUTHOR]

In all, 143 human embryos obtained 3 days (day 3) after insemination or intracytoplasmic sperm injection (ICSI) were biopsied and a single nucleated cell removed for identification of aneuploidy by fluorescent in-situ hybridization (FISH) for chromosomes X, Y, 13, 16, 18 and 21. Fifty-one per cent of embryos were aneuploid and significantly more aneuploid embryos blocked in further development to morulae and blastocysts than euploid embryos (59 versus 34%; P < 0.001). Chromosomal analysis of the generated blastocysts revealed 40% were aneuploid (16 of 40 generated blastocysts). Re-examination of cells by FISH for the same chromosome probes of the inner cell mass (ICM) of expanded and hatching blastocysts derived from the aneuploid embryos revealed a high incidence of mosaicism of ICM cell lineages that were usually predictable from observations of day 3 single-cell biopsies. These data would not support the hypothesis of a preferential allocation of euploid cells to the ICM and aneuploid cells to the trophectoderm. A high concordance between day 3 aneuploidy diagnosis and ICM cell lineages was observed with trisomies (97%), and multiple complex chromosome numerical abnormalities (100%). A reduced concordance was observed with monosomies (65%) and haploidy (18%). Concomitantly, the proportion of ICM cell lineages was increased in blastocysts whose chromosomal condition was diagnosed as haploid (21%) or with complex numerical abnormalities (50%). [ABSTRACT FROM AUTHOR]

The response of murine, bovine and human oocytes to pure recombinant preparations of human follicle stimulating hormone (rFSH) and luteinizing hormone (rLH) for meiotic maturation and subsequent developmental competence in vitro were examined in the present experiments. Maturation of immature bovine oocytes to the metaphase II stage was significantly increased by the addition of 1 IU/ml of rFSH in combination with either 1 IU/ml rLH or 10 IU/ml rLH. Similarly, embryonic development to the blastocyst stage was improved in bovine oocytes treated with a 1:10 combination of rFSH:rLH. However, no significant difference was observed in the number of inner cell mass or trophectoderm cells of the resulting blastocysts. Although the increased maturation to metaphase II was not significant, human embryonic developmental competence was improved by maturing oocytes in the presence of a 1:10 ratio of rFSH:rLH as only those oocytes exposed to a 1:10 ratio of rFSH: rLH during maturation showed normal cleavage patterns beyond day 2. In addition, 1 IU/ml rFSH and 1 IU/ml rLH increased the expression of oocyte proteins in human oocytes. The inclusion of recombinant gonadotrophins, either singly or in combination, had no significant effect on the maturation, fertilization or embryonic development of in-vitro matured mouse oocytes. These data provide support for the responsiveness of human and bovine oocytes to gonadotrophins in vitro and the need to consider variations in the relative concentrations for optimization of oocyte developmental competence. [ABSTRACT FROM AUTHOR]

Primary oocytes recovered from small and growing follicles of > or = 3 mm in the ovaries of untreated women, can be matured in vitro, will fertilize and develop in vitro, and when transferred to the patient, develop to term. However, the implantation rate of cleaved embryos has been disappointingly low and when embryos are allowed to develop beyond the 4-cell in vitro, retardation of development and blockage is frequently observed, with relatively few embryos developing to blastocysts. We have devised new culture systems for human embryos to enable high rates of development of in-vivo matured oocytes to blastocysts within 5-6 days of culture, and high implantation rates of these blastocysts when they are transferred to the patients' uterus. These culture systems are now being used for in-vitro matured oocytes. In order to determine whether embryo developmental competence could be improved, a number of factors were examined. Treatment of patients with pure follicle stimulating hormone (FSH) early in the follicular phase, or treatment with oestrogen prior to oocyte recovery, had no apparent effect on any parameters of oocyte developmental competence. There was no indication that a medium made specifically for human oocyte maturation improved oocyte developmental competence. Nuclear and cytoplasmic changes in oocytes matured in vitro appear to be similar to that in vivo, although some lack of synchronization in completing maturation is evident. It is possible that follicles of < 10 mm diameter in the human contain developmentally-incompetent oocytes. However, the development to term and birth of normal babies from germinal vesicle stage oocytes recovered from small follicles and matured in vitro, suggests that further research will identify the factors necessary to improve embryo developmental competence. The application of immature oocyte collection (IOC) and in vitro maturation (IVM) as an alternative to ovulation stimulation with high doses of gonadotrophins for in-vitro fertilization (IVF), remains a priority for research in human medicine. [ABSTRACT FROM AUTHOR]

A cell-free culture system was designed for human embryo development to the blastocyst stage by testing a range of culture conditions in a series of protocols. The culture system that was evolved has a brief 1 h exposure to spermatozoa and then culture of the pronucleate zygote for 2 days in IVF-50 medium. Two or three embryos were cultured together in 20 μl microdrops of medium under oil. Embryos were then regrouped and two or three at a similar stage were cultured together in 50 μl microdrops of Gardner's G2 medium under oil from days 3 to 5. Embryos were transferred to fresh G2 medium on day 5 and cultured for a further 1 or 2 days (day 6 or 7). No serum was used in any of the cultures. The embryo transfer medium and G2 medium were supplemented with human serum albumin. The zonae of all blastocysts to be transferred to patients were completely removed enzymatically. Using this protocol, 52% of zygotes developed to blastocysts and 34 out of 35 patients treated received 82 blastocysts and 11 morulae on day 5 or 6. Twenty-one fetal sacs with positive heartbeats (23% implantation rate) were detected in 13 ongoing pregnancies (38% pregnancy rate/transfer or 37%/patient treated). We anticipate that further improvements in embryo development and the selection of viable embryos can be achieved using this simple and effective culture system. [ABSTRACT FROM PUBLISHER]

The authors demonstrate a silicon-based single-electron transistor (SET) in the few-electron regime. Our structure is similar to a metal-oxide-semiconductor field-effect transistor. The substrate, however, is undoped and could be isotope enriched so that any nonuniformity and spin decoherence due to impurity and nuclear spins can be minimized. A bilayer-gated configuration provides flexibility in manipulating single electrons. The stability chart measured at 4.2 K shows diamondlike domains with a charging energy of 18 meV, indicating a quantum dot of 20 nm in diameter. The benefits of using this enhancement-mode SET in silicon and its potential application for scalable quantum computing are discussed. [ABSTRACT FROM AUTHOR]

We demonstrate experimentally single-electron quantum dots using a single-top-gate transistor configuration on a composite quantum well. The data indicate a 15 meV Coulomb charging energy and a 20 meV orbital energy spacing, which imply a quantum dot of 20 nm in diameter. Combining with the inherent advantage of a large electron g* factor in InAs, our demonstration is significant for a solid state implementation of a scalable quantum computing. [ABSTRACT FROM AUTHOR]

We report experimental results on gated Y-branch switches made from InAs ballistic electron waveguides. We demonstrate that gating modifies the electron wave functions as well as their interference pattern, resulting in anticorrelated oscillatory transconductances. Our data provide evidence of steering the electron wave function in a multichannel transistor structure. [ABSTRACT FROM AUTHOR]

This paper describes current and ongoing activities associated with a COST initiative in the field of urban underground infrastructure. Part of this initiative is focused in the area of water distribution systems. The initiative is one of several COST Actions in the field ofurban civil engineering. Urban infrastructure associated with water distribution represents a significant part of a municipality's real capital. The maintenance of this capital will be given increasing emphasis in the future because of several factors; The magnitude of the capital asset and its strategic importance; The need to target investment in rehabilitation with asset deterioration. Increasingly stringent requirements for reliability and performance in the context of regulation and public expectations. This paper summarises the key findings and activities associated with the COST Action in a form which is relevant in the context of wider international cooperation. [ABSTRACT FROM AUTHOR]