1,477 research outputs found

    Gray Assist Bar OPC

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    Assist bar Optical Proximity Correction (OPC) has been demonstrated to increase across pitch performance and depth-of- focus of semi-dense to isolated lines1. As the sub-resolution assist feature (SRAF) or assist bar’s size increases, so does its desired lithographic effect, as well as its undesired printability. In other words, when large assist features are required at isolated pitches, the assist features may print. A frequency-preserving assist bar solution is the most preferred one, but difficult to realize for opaque assist features due to printability. The concept of frequency-preserving Gray Assist Bar OPC has been introduced as a method to extend imaging performance for small features across a wide rage of duty ratios3. In this paper, we will present the experimental validation of this concept. The Gray Assist Bar mask was manufactured using a two-level lithography process, and the optical properties have been characterized using a Woollam VUV VASE system. Additional metrology was performed using an AFM (SNP9000) and CD SEM (KLA8250XR). Exposures on a 0.75NA 193nm scanner clearly show the expected effects. The use of the Gray Assist Bar features reduces the through pitch critical dimension (CD) variations significantly and can hence be regarded as an ‘Optical Proximity Correction’. The isofocal inflection point of aerial images is shifted in cases with Gray Assist Bars, resulting in flatter bossung curves and a larger depth of focus (DOF) for the various features through pitch at their target size. This results in larger overlapping process windows. The Gray Assist Bars has also shown a very low printability, even with aggressive off-axis illumination (OAI) settings

    Aligning ecology and markets in the forest carbon cycle

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    A forest carbon (C) offset is a quantifiable unit of C that is commonly developed at the local or regional project scale and is designed to counterbalance anthropogenic C emissions by sequestering C in trees. In cap-and-trade programs, forest offsets have market value if the sequestered C is additional (more than would have occurred in the absence of the project) and permanent (sequestered within the project boundary for a specified period of time). Local management and ecological context determine the rate of C sequestration, risk of loss, and hence the market value. An understanding of global C dynamics can inform policy but may not be able to effectively price an ecosystem service, such as C sequestration. Appropriate pricing requires the assistance of ecologists to assess C stock abundance and stability over spatial and temporal scales appropriate for the regional market. We use the risk that sequestered C will be emitted as a result of wildfire (reversal risk) to show how ecological context can influence market valuation in offset programs

    Repetitive posterior iliac crest autograft harvest resulting in an unstable pelvic fracture and infected non-union: case report and review of the literature

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    Fractures of the pelvic ring have been well studied, and the biomechanical relationship between the anterior and posterior elements is an important concept to understand these complex injuries. The vast majority of these injuries are due to trauma. However, in rare circumstances, autogenous bone graft harvesting may lead to an unstable pelvic ring. In this case report, we describe a rare complication in a 70-year old female patient who developed an unstable pelvis and an infected non-union secondary to repeated posterior iliac graft harvest. The orthopaedic surgeon should be aware of this detrimental complication associated with extensive or repeated posterior iliac crest graft harvest

    Acute Clopidogrel Use and Outcomes in Patients With Non–ST-Segment Elevation Acute Coronary Syndromes Undergoing Coronary Artery Bypass Surgery

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    OBJECTIVES We sought to characterize patterns of clopidogrel use before coronary artery bypass grafting (CABG) and examine the drug's impact on risks for postoperative transfusions among patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS). BACKGROUND Adherence in community practice to American College of Cardiology/American Heart Association guidelines for clopidogrel use among NSTE ACS patients has not been previously characterized. METHODS We evaluated 2,858 NSTE ACS patients undergoing CABG at 264 hospitals participating in the CRUSADE (Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes With Early Implementation of the ACC/AHA Guidelines) Initiative. We examined the patterns of acute clopidogrel therapy and its association with bleeding risks among those having early CABG ≤5 days and again among those having late surgery >5 days after catheterization. RESULTS Within 24 h of admission, 852 patients (30%) received clopidogrel. In contrast to national guidelines, 87% of clopidogrel-treated patients underwent CABG ≤5 days after treatment. Among those receiving CABG within ≤5 days of last treatment, the use of clopidogrel was associated with a significant increase in blood transfusions (65.0% vs. 56.9%, adjusted odds ratio [OR] 1.36, 95% confidence interval [CI] 1.10 to 1.68) as well as the need for transfusion of ≥4 U of blood (27.7% vs. 18.4%, OR 1.70, 95% CI 1.32 to 2.19). In contrast, acute clopidogrel therapy was not associated with higher bleeding risks if CABG was delayed >5 days (adjusted OR 1.18, 95% CI 0.54 to 2.58). CONCLUSIONS Despite guideline recommendations, the overwhelming majority of NSTE ACS patients treated with acute clopidogrel needing CABG have their surgery within ≤5 days of treatment. A failure to delay surgery is associated with increased blood transfusion requirements that must be weighed against the potential clinical and economic impacts of such delays

    Stories of people who have attended a lesbian, gay, bisexual and trans support group in a secure intellectual disability service

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    Background This research is about people who have intellectual disabilities and live in a secure hospital. It is about a group of people who meet at a support group. The support group is for people who are lesbian, gay, bisexual or transgender. Methods These people with intellectual disabilities helped with planning, doing, and telling other people about the research. They told their stories about going to the support group. Results Their stories were joined together into a group story. The story said that the group helped people in lots of different ways. For some people going to the group was difficult at first because it was 'coming out'. This means telling other people you are lesbian, gay, bisexual, or transgender. Then it got easier and people started to feel better about themselves. Then they wanted to help others and this was important in their lives. Conclusions This group seemed to help people get better. We have given some ideas for setting up other groups and doing more research

    Science results from sixteen years of MRO SHARAD operations

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    In operation for >16 years to date, the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) sounder has acquired data at its nominal 300–450 m along-track and 3-km cross-track resolution covering >55% of the Martian surface, with nearly 100% overlap in coverage at that scale in the polar regions and in a number of smaller mid-latitude areas. While SHARAD data have opened a new window into understanding the interior structures and properties of Martian ices, volcanics, and sedimentary deposits up to a few kilometers in depth, they have also led to new revelations about the deeper interior and the behavior of the planet’s ionosphere. Here we summarize the data collected by SHARAD over this time period, the methods used in the analysis of that data, and the resulting scientific findings. The polar data are especially rich, revealing complex structures that comprise up to several dozen reflecting interfaces that extend to depths of 3 km, which inform the evolution of Martian climate in the late Amazonian period. SHARAD observations of mid-latitude lobate debris aprons and other glacier-like landforms detect strong basal reflections and low dielectric loss, confirming that they are icerich debris-covered glaciers. In other mid-latitude terrains, SHARAD data demonstrate the presence of widespread ground ices, likely at lower concentrations. SHARAD signals also probe non-icy materials, mapping out stacked lava flows, probing low-density materials thought to be ash-fall deposits, and occasionally penetrating sedimentary deposits, all of which reveal the structures and interior properties diagnostic of emplacement processes. SHARAD signals are impacted by their passage through the Martian ionosphere, revealing variations in time and space of the total electron content linked with the remanent magnetic field. Advanced techniques developed over the course of the mission, which include subband and super-resolution processing, coherent and incoherent summing, and three-dimensional (3D) radar imaging, are enabling new discoveries and extending the utility of the data. For 3D imaging, a cross-track spacing at the nominal 3-km resolution is more than sufficient to achieve good results, but finer spacing of 0.5 km or less significantly improves the spatially interpolated radar images. Recent electromagnetic modeling and a flight test show that SHARAD’s signal-to-noise ratio can be greatly improved with a large (~120◦) roll of the spacecraft to reduce interference with the spacecraft body. Both MRO and SHARAD are in remarkably fine working order, and the teams look forward to many more years in which to pursue improvements in coverage density, temporal variability in the ionosphere, and data quality that promise exciting new discoveries at Mars
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