Acoustic wave studies during fast ion beam interactions with solds

Ion beam material modification is currently being used for several important technological applications such as semiconductor doping [1], surface modification of metals [2], cold etching [1], micro machining [1] and material analysis [3]. Ion beam processing has many advantages [4]. The speed, homogeneity and reproducibility of the doping process are easily controlled. Tight control of the number of doping atoms is possible. Low purity dopants can be used. The target can be kept at low temperatures allowing for low melting temperature materials to be modified. Simple masking methods can be employed and doping can be performed through passive films. Low penetration depths can be achieved and multiple implantations can produce varied doping profiles. Devices with small dimensions can be manufactured due to the small size of the ion beam. Since ion implantation is not an equilibrium process, equilibrium solubility limits of the ion species in the target material can be exceeded. There are some disadvantages of this type of doping process. Damage is caused to the crystal structure creating defects. Implantation is limited to near-surface regions and theoretical profiles can be difficult to obtain due to effects of channeling and diffusion [5]

Rank-Ordering Statistics of Extreme Events: Application to the Distribution of Large Earthquakes

Rank-ordering statistics provides a perspective on the rare, largest elements of a population, whereas the statistics of cumulative distributions are dominated by the more numerous small events. The exponent of a power law distribution can be determined with good accuracy by rank-ordering statistics from the observation of only a few tens of the largest events. Using analytical results and synthetic tests, we quantify the systematic and the random errors. We also study the case of a distribution defined by two branches, each having a power law distribution, one defined for the largest events and the other for smaller events, with application to the World-Wide (Harvard) and Southern California earthquake catalogs. In the case of the Harvard moment catalog, we make more precise earlier claims of the existence of a transition of the earthquake magnitude distribution between small and large earthquakes; the $b$-values are $b_2 = 2.3 \pm 0.3$ for large shallow earthquakes and $b_1 = 1.00 \pm 0.02$ for smaller shallow earthquakes. However, the cross-over magnitude between the two distributions is ill-defined. The data available at present do not provide a strong constraint on the cross-over which has a $50\%$ probability of being between magnitudes $7.1$ and $7.6$ for shallow earthquakes; this interval may be too conservatively estimated. Thus, any influence of a universal geometry of rupture on the distribution of earthquakes world-wide is ill-defined at best. We caution that there is no direct evidence to confirm the hypothesis that the large-moment branch is indeed a power law. In fact, a gamma distribution fits the entire suite of earthquake moments from the smallest to the largest satisfactorily. There is no evidence that the earthquakes of the Southern California catalog have a distribution with tw

Advanced Glycation End Product Interventions Reduce Diabetes-Accelerated Atherosclerosis

Advanced glycation end product (AGE) formation may contribute to the progression of atherosclerosis, particularly in diabetes. The present study explored atherosclerosis in streptozotocin-induced diabetic apolipoprotein E–deficient (apoE�/�) mice that were randomized (n � 20) to receive for 20 weeks no treatment, the AGE cross-link breaker ALT-711, or the inhibitor of AGE formation aminoguanidine (AG). A sixfold increase in plaque area with diabetes was attenuated by 30 % with ALT-711 and by 40 % in AG-treated mice. Regional distribution of plaque demonstrated no reduction in plaque area or complexity within the aortic arch with treatment, in contrast to the thoracic and abdominal aortas, where significant attenuation was seen. Diabetes-associated accumulation of AGEs in aorta

Acceptability of Telerehabilitation for Magnification Devices for the Visually Impaired Using Various Approaches to Facilitate Accessibility

PurposeWe examined different methods to reduce the burden of accessing technology for videoconferencing during telerehabilitation for magnification devices for the visually impaired.MethodsDuring telerehabilitation studies over the past 5 years, vision rehabilitation providers assessed and gave training to visually impaired participants with newly dispensed magnification devices at home who connected to Zoom videoconferencing via loaner tablets or smartphones with assistance from (phase 1; n = 10) investigators by phone, (phase 2; n = 11) local Lions Club volunteers in participants' homes, or (phase 3; n = 24) remote access control software in a randomized controlled trial with 13 usual care controls who received in-office training. All participants completed the same post-telerehabilitation phone survey.ResultsA significantly greater proportion of phase 3 subjects indicated they strongly or mostly agreed that the technology did not interfere with the session (96%) compared to phase 1 (60%; 95% confidence interval [CI], 1.2-12.5; P = 0.03) or phase 2 (55%; 95% CI, 1.8-188; P = 0.01). The majority indicated telerehabilitation was as accurate as in person (68%), they were comfortable with telerehabilitation (91%) and interested in a future session (83%), and their magnifier use improved (79%), with no significant differences in these responses between phases (all P > 0.10), including comparisons of participants randomized to telerehabilitation or in-office training in phase 3 who reported similar overall satisfaction levels (P = 0.84).ConclusionsParticipants across all phases reported high levels of acceptance for telerehabilitation, with least interference from technology using remote access control in phase 3.Translational relevanceWith accommodations for accessibility to videoconferencing technology, telerehabilitation for magnification devices can be a feasible, acceptable, and valuable option in countries with resources to support the technology

Automated nondestructive evaluation method for characterizing ceramic and metallic hot gas filters.

In advanced coal-fired power generation, one technology under development to clean up hot gases before their use as fuel for gas turbines is rigid ceramic candle filters. These porous filters are typically 1.5 m long and 60 mm in diameter and are made of various ceramic materials, including clay-bonded SiC. The high costs of downtime in a large utility demands that nondestructive evaluation/characterization (NDE/C) methods be available. At shutdowns, data from such analysis are needed to decide which filters are still usable and which need to be replaced, and if possible, to estimate the remaining lifetimes. Thus our objective was to develop reliable low-cost NDE technology for these filters. Our approach was to develop NDE/C technology, referred to as acousto-ultrasonics (AU), for application to hot gas filters. Lamb waves generated by the AU method were analyzed to derive a stress wave factor (SWF). This technology was tested by comparing SWF data with the measured strength for a variety of rigid ceramic filters and was shown to work on iron-aluminide filters as well but no strength data have been obtained on the iron-aluminides at this time

Chapter 7: Wetlands

Contains fulltext : 205862.pdf (publisher's version ) (Open Access

Seismic imaging in Long Valley, California, by surface and borehole techniques: An investigation of active tectonics

The search for silicic magma in the upper crust is converging on the Long Valley Caldera of eastern California, where several lines of geophysical evidence show that an active magma chamber exists at mid‐to lower‐crustal depths. There are also other strong indications that magma may be present at depths no greater than about 5 km below the surface. In this paper, we review the history of the search for magma at Long Valley. We also present the preliminary results from a coordinated suite of seismic experiments, conducted by a consortium of institutions in the summer and fall of 1984, that were designed to refine our knowledge of the upper extent of the magma chamber. Major funding for the experiments was provided by the Geothermal Research Program of the U.S. Geological Survey (USGS) and by the Magma Energy Technology Program of the U.S. Department of Energy (DOE), a program to develop the technology necessary to extract energy directly from crustal magma. Additional funding came from DOE's Office of Basic Energy Sciences and the National Science Foundation (NSF). Also, because extensive use was made of a 0.9‐km‐deep well lent to us by Santa Fe Geothermal, Inc., the project was conducted partly under the auspices of the Continental Scientific Drilling Program (CSDP). As an integrated seismic study of the crust within the caldera that involved the close cooperation of a large number of institutions, the project was moreover viewed as a prototype for future scientific experiments to be conducted under the Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL). The experiment thus represented a unique blend of CSDP and PASSCAL methods, and achieved goals consistent with both programs

Aquatic Ecosystems are the Largest Source of Methane on Earth

Methane concentrations in the atmosphere have almost tripled since the industrial revolution, contributing 16% of the additional radiative forcing by anthropogenic greenhouse gas emissions. Aquatic ecosystems are an important but poorly constrained source of methane (CH4) to the atmosphere. Here, we present the first global methane emission assessment from all major natural, impacted and human-made aquatic ecosystems including streams and rivers, freshwater lakes and reservoirs, aquaculture ponds, estuaries, coastal vegetated wetlands (mangroves, salt-marshes, seagrasses), tidal flats, continental shelves and the open ocean, in comparison to recent estimates from natural wetlands and rice paddies. We find that aquatic systems are the largest source of methane globally with contributions from small lakes and coastal ocean ecosystems higher than previously estimated. We suggest that increased biogenic methane from aquatic ecosystems due to a combined effect of climate-feedbacks and human disturbance, may contribute more than expected to rising methane concentrations in the atmosphere

Benefit of an electronic head‐mounted low vision aid

Purpose: To evaluate the efficacy of electronic head-mounted low vision aid (e-LVA) SightPlus (GiveVision, UK, givevision.net) and to determine which people with low vision would see themselves likely using an e-LVA like this. Methods: Sixty participants with low vision aged 18 to 93 used SightPlus during an in-clinic study session based on a mixed methods design. Visual acuity (ETDRS), contrast sensitivity (Pelli-Robson) and reading performance (MNREAD) were measured binocularly at baseline (no device), with the device in ‘normal’ mode (zoom only), and with preferred enhanced mode (zoom and one of four digital image enhancements). At the end of the session, a short questionnaire recorded willingness to use an e-LVA like SightPlus, potential use cases, positive/negative comments and adverse effects. Results: Binocular distance visual acuity improved significantly by 0.63 logMAR on average (p < 0.0001) to 0.20 logMAR. Contrast sensitivity improved significantly by 0.22 log units (p < 0.0001) to 1.21 log units with zoom only and by 0.40 log units to 1.37 log units with zoom and preferred image enhancement. Reading performance improved significantly for near visual acuity and critical print size (p < 0.015), although reading speed significantly decreased (p < 0.0001). Nearly half (47%) of the participants indicated they would use an e-LVA like SightPlus, especially for television, reading and entertainment (e.g. theatre). Multivariate logistic regression showed that proportion of lifetime affected by sight loss, baseline contrast sensitivity and use of electronic LVAs explained 41% of the variation in willingness to use. Conclusions: SightPlus improves visual function in people with low vision and would be used in its current form by one half of the people who tried it. Adverse effects were infrequent and resolved when the device was removed. Future work should focus on comparing e-LVAs through repeatable real-world tasks and impact on quality of life

Aquatic Ecosystems are the Most Uncertain but Potentially Largest Source of Methane on Earth

Atmospheric methane is a potent greenhouse gas that has tripled in concentration since pre-industrial times. The causes of rising methane concentrations are poorly understood given its multiple sources and complex biogeochemistry. Natural and human-made aquatic ecosystems, including wetlands, are potentially the largest single source of methane, but their total emissions relative to other sources have not been assessed. Based on a new synthesis of inventory, remote sensing and modeling efforts, we present a bottom-up estimate of methane emissions from streams and rivers, freshwater lakes and reservoirs, estuaries, coastal wetlands (mangroves, seagrasses, salt-marshes), intertidal flats, aquaculture ponds, continental shelves, along with recently published estimates of global methane emissions from freshwater wetlands, rice paddies, the continental slope and open ocean. Our findings emphasize the high variability of aquatic methane fluxes and a possibly skewed distribution of currently available data, making global estimates sensitive to statistical assumptions. Mean emissions make aquatic ecosystems the largest source of methane globally (53% of total global methane emissions). Median emissions are 42% of the total global methane emissions. We argue that these emissions will likely increase due to urbanization, eutrophication and climate change