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Estimates of riverine N2O emission contain great uncertainty because of the lack of quantitative knowledge concerning riverine N2O sources and fates. Using a 3.5-year record of monthly N2O measurements from the Yongan River network of eastern China, we developed a mass-balance model to address the riverine N2O source and sink processes. We achieved reasonable model efficacies (R2= 0.44–0.84, Nash–Sutcliffe coefficients = 0.40–0.80) across three tributaries and the entire river system. Estimated riverine N2O loads originated from groundwater (38–88%), surface runoff (3–26%), and in-stream production (4–48%). Estimated in-stream losses via atmospheric release + complete denitrification accounted for 76, 95, 25, and 89% of riverine N2O fate for the agricultural, residential, forest, and entire river system, respectively. Considering limited complete denitrification, the model estimated an upper-bound riverine N2O emission rate of 2.65 ton N2O–N km–2year–1for the entire river system. Riverine N2O emission estimates were of comparable magnitude to those estimated with a power-law scaling model. Riverine N2O emissions using the IPCC default emission factor (0.26%) overestimated emissions by 3–15 times, whereas the dissolved N2O concentration-based emission factor overestimated or underestimated emissions. This study highlights the importance of combining comprehensive information on N2O sources and fates to achieve accurate riverine N2O emission estimates.

ABSTRACTMost of the current industrial processes for L-leucine production are based on fermentation, usually in fed-batch operation mode. Although the culture technology has advanced in recent decades, the process still has significant drawbacks. To solve these problems, we investigated the effects of chemostat culture conditions on the production of L-leucine by Corynebacterium glutamicumCP. The dilution rate, the nitrogen source, and the carbon–nitrogen ratio of the medium were optimized. With the addition of ammonium acetate to the chemostat medium, the initial C/N ratio was adjusted to 57.6, and the L-leucine titer reached the highest level at the optimal dilution rate of 0.04 h−1. Compared with fed-batch culture, the L-leucine titer was reduced (from 53.0 to 24.8 g L−1), but the yield from glucose was increased by 10.0% (from 0.30 to 0.33 mol mol−1) and productivity was increased by 58.3% (from 1.2 to 1.9 g L−1h−1). Moreover, the titer of the by-product L-alanine was significantly reduced (from 8.9 to 0.8 g L−1). In addition, gene expression levels and activity of key enzymes in the synthesis of L-leucine and L-alanine were analyzed to explain the difference of production performance between chemostat culture and fed-batch culture. The results indicate that chemostat culture has great potential to increase the industrial production of L-leucine compared to current fed-batch approaches.

ABSTRACTVarious process intensification methods were proposed to improve the yield, quality, and safety of fermented products. Here, we report the enhancement of L-leucine production by Corynebacterium glutamicumCP using ultrasound-assisted fed-batch fermentation. Response surface methodology was employed to optimize the sonication conditions. At an ultrasonic power density of 94 W/L, frequency of 25 kHz, interval of 31 min, and duration of 37 s, C. glutamicumCP produced 52.89 g/L of L-leucine in 44 h, representing a 21.6% increase compared with the control. The production performance of L-leucine was also improved under ultrasonic treatment. Moreover, the effects of ultrasound treatment on the fermentation performance of L-leucine were studied in terms of cell morphology, cell membrane permeability, and enzyme activity. The results indicate that ultrasonication is an efficient method for the intensification of L-leucine production by C. glutamicumCP.

Legacy nutrient accumulation from excess anthropogenic inputs has become a serious environmental issue in many watersheds worldwide. In this review, we provide a systematic overview of sources, legacy nutrient pools, watershed-scale water quality models, and agronomic and environmental implications of legacy nitrogen and phosphorus pools. Hydrological, biogeochemical, and anthropogenic factors exert interacting controls on legacy nutrient dynamics in soils, sediments, and vadose zone/groundwater. Most current watershed models do not effectively incorporate legacy nutrient dynamics, while models that consider legacy effect often have high uncertainty in their treatment of legacy nutrient dynamics. In many intensively managed watersheds, legacy nutrients are a dominant and long-term (>10 years) source of nutrients to receiving waters, as well as a potentially important nutrient source for crop production. Many existing beneficial management measures have limitations for reducing legacy nutrient losses to surface waters due to appreciable differences in legacy nutrient forms, watershed storage locations, and temporal dynamics compared to those of contemporary nutrient inputs. Recognizing the importance of legacy nutrients is necessary for developing sustainable watershed nutrient management plans for future food, bioenergy, and water security. These plans require strategies to maximize use of legacy nutrient resources to minimize their loss to the atmosphere (e.g., N2O emissions) and surface waters. Finally, this synthesis identified future research needs for improving the understanding, utilization, and mitigation of watershed legacy nutrient pools.

The virtual physical examination (VPE) platform is a web–based, multimedia system for medical examination education, distributed and supported by Cerner. The system was built using MySQL, Flash and PHP and developed for creating and conducting physical examinations on virtual patient cases in a simulated environment. VPE allows users to perform physical examinations virtually on patients. A user can create 3D avatars of patients, build medical cases, perform diagnosis and attach associated files including audio, video, image, text and interactive assets. VPE allows for controlled sharing of assets as well as full cases, either within the same organisation or publicly. A video demonstrating VPE can be found at http://digbio.missouri.edu/Cerner/Cerner_VPE_Demo.mp4. VPE has broad educational applications ranging from the basic introduction of medicine to high school students to advanced education for nursing and medical students. The solution is used to both teach and reinforce physical exam concepts. VPE is available at https://vpe.cernerlearningmanager.com.

This article addresses the problem of chip-level thermal profile estimation using runtime temperature sensor readings. We address the challenges of: (a) availability of only a few thermal sensors with constrained locations (sensors cannot be placed just anywhere); (b) random chip power density characteristics due to unpredictable workloads and fabrication variability. Firstly we model the random power density as a probability density function. Given such statistical characteristics and the runtime thermal sensor readings, we exploit the correlation in power dissipation among different chip modules to estimate the expected value of temperature at each chip location. Our methods are optimal if the underlying power density has Gaussian nature. We give a heuristic method to estimate the chip-level thermal profile when the underlying randomness is non-Gaussian. An extension of our method has also been proposed to address the dynamic case. Several speedup strategies are carefully investigated to improve the efficiency of the estimation algorithm. Experimental results indicated that, given only a few thermal sensors, our method can generate highly accurate chip-level thermal profile estimates within a few milliseconds.

Tissue engineering has long been investigated to repair articular cartilage defects. Successful reports have usually involved the seeding of autologous chondrocytes into polymers. Problems arise because of the scarcity of cartilage tissue biopsy material, and because the in vitro expansion of chondrocytes is difficult; to some extent, these problems limit the clinical application of this promising method. Bone marrow-derived mesenchymal stem cells (MSCs) have been proved a potential cell source because of their in vitro proliferation ability and multilineage differentiation capacity. However, in vitro differentiation will lead to high cost and always results in decreased cell viability. In this study we seeded culture-expanded autologous MSCs into bioceramic scaffold–β-tricalcium phosphate (β-TCP) in an attempt to repair articular cartilage defects (8 mm in diameter and 4 mm in depth) in a sheep model. Twenty-four weeks later, the defects were resurfaced with hyaline-like tissue and an ideal interface between the engineered cartilage, the adjacent normal cartilage, and the underlying bone was observed. From 12 to 24 weeks postimplantation, modification of neocartilage was obvious in the rearrangement of surface cartilage and the increase in glycosaminoglycan level. These findings suggest that it is feasible to repair articular cartilage defects with implants generated by seeding autologous MSCs, without in vitro differentiation, into β-TCP. This approach provides great potential for clinical applications.