Nitrogen retention in the riparian zone of watersheds underlain by discontinuous permafrost

Thesis (M.S.) University of Alaska Fairbanks, 2005Riparian zones function as important ecotones for reducing nitrate concentration in groundwater and inputs into streams. In the boreal forest of interior Alaska, permafrost confines subsurface flow through the riparian zone to shallow organic horizons, where plant uptake of nitrate and denitrification are typically high. Two research questions were addressed in this study: 1) how does riparian zone nitrogen retention vary in watersheds underlain by discontinuous permafrost, and 2) what is the contribution of denitrification to riparian zone nitrogen retention? To estimate the contribution of the riparian zone to watershed nitrogen retention, I analyzed groundwater chemistry using an end-member mixing model. To assess the importance of denitrification as a mechanism of nitrogen retention, I conducted field denitrification assays using the acetylene block technique. Over the summer, nitrogen retention averaged 0.75 and 0.22 mmol N m⁻² d⁻¹ in low and high permafrost watersheds, respectively. Compared with the fluvial export of nitrogen, the retention rate of nitrogen in the riparian zone is 10 - 15% of the loss rate in stream flow. Denitrification accounted for a small proportion (3%) of total nitrogen retention in the riparian zone. Variation in nitrogen retention between watersheds did not account for differences in stream nitrate concentration between watersheds.Introduction -- Factors controlling denitrification -- Riparian zones as nutrient filters -- Models of riparian zone function -- Permafrost and hydrology -- Caribou Poker Creeks Research Watershed (CPCRW) -- References -- Nitrogen retention in the riparian zone of watersheds underlain by discontinuous permafrost -- Conclusions -- References

A framework for FPGA functional units in high performance computing

FPGAs make it practical to speed up a program by defining hardware functional units that perform calculations faster than can be achieved in software. Specialised digital circuits avoid the overhead of executing sequences of instructions, and they make available the massive parallelism of the components. The FPGA operates as a coprocessor controlled by a conventional computer. An application that combines software with hardware in this way needs an interface between a communications port to the processor and the signals connected to the functional units. We present a framework that supports the design of such systems. The framework consists of a generic controller circuit defined in VHDL that can be configured by the user according to the needs of the functional units and the I/O channel. The controller contains a register file and a pipelined programmable register transfer machine, and it supports the design of both stateless and stateful functional units. Two examples are described: the implementation of a set of basic stateless arithmetic functional units, and the implementation of a stateful algorithm that exploits circuit parallelism

The role of primary care in adult weight management: qualitative interviews with key stakeholders in weight management services

Background: Primary care has a key role to play in the prevention and management of obesity, but there remain barriers to engagement in weight management by primary care practitioners. The aim of this study was to explore the views of key stakeholders in adult weight management services on the role of primary care in adult weight management. Methods: Qualitative study involving semi-structured interviews with nine senior dietitians involved in NHS weight management from seven Scottish health boards. Transcripts were analysed using an inductive thematic approach. Results: A range of tensions were apparent within three key themes: weight management service issues, the role of primary care, and communication with primary care. For weight management services, these tensions were around funding, the management model of obesity, and how to configure access to services. For primary care, they were around what primary care should be doing, who should be doing it, and where this activity should fit within wider weight management policy. With regard to communication between weight management services and primary care, there were tensions related to the approach taken (locally adapted versus centralised), the message being communicated (weight loss versus wellbeing), and the response from practitioners (engagement versus resistance). Conclusions: Primary care can do more to support adult weight management, but this requires better engagement and communication with weight management services, to overcome the tensions highlighted in this study. This, in turn, requires more secure, sustained funding. The example of smoking cessation in the UK, where there is a network of well-resourced NHS Stop Smoking Services, accessible via different means, could be a model to follow

An Investigation of Production Risk, Risk Preferences and Technical Efficiency: Evidence From Rainfed Lowland Rice Farms in the Philippines

Risk plays a vital role in farmers' decisions on input allocations and, therefore, output supply. This paper provides empirical evidence on the estimation of production risk, risk preferences and technical inefficiency. An eight-year panel data set is used for 46 rice farmers from a representative rainfed lowland environment in Central Luzon, Philippines. The heteroskedastic and stochastic frontier frameworks are reconciled and extended to accommodate the risk preferences of farmers in an analysis of production risk. Results show that technical inefficiency is overstated in risky production environments where farmers are risk-averse.production risk, risk preferences, technical efficiency, Productivity Analysis, Risk and Uncertainty,

The transmission of nosocomial pathogens in an intensive care unit: a space–time clustering and structural equation modelling approach

We investigated the incidence of cases of nosocomial pathogens and risk factors in an intensive treatment unit ward to determine if the number of cases is dependent on location of patients and the colonization/infection history of the ward. A clustering approach method was developed to investigate the patterns of spread of cases through time for five microorganisms [methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter spp., Klebsiella spp., Candida spp., and Pseudomonas aeruginosa] using hospital microbiological monitoring data and ward records of patient-bed use. Cases of colonization/infection by MRSA, Candida and Pseudomonas were clustered in beds and through time while cases of Klebsiella and Acinetobacter were not. We used structural equation modelling to analyse interacting risk factors and the potential pathways of transmission in the ward. Prior nurse contact with colonized/infected patients, mediated by the number of patient-bed movements, were important predictors for all cases, except for those of Pseudomonas. General health and invasive surgery were significant predictors of cases of Candida and Klebsiella. We suggest that isolation and bed movement as a strategy to manage MRSA infections is likely to impact upon the incidence of cases of other opportunist pathogen

Optimal Data-Dependent Hashing for Approximate Near Neighbors

We show an optimal data-dependent hashing scheme for the approximate near neighbor problem. For an $n$-point data set in a $d$-dimensional space our data structure achieves query time $O(d n^{\rho+o(1)})$ and space $O(n^{1+\rho+o(1)} + dn)$, where $\rho=\tfrac{1}{2c^2-1}$ for the Euclidean space and approximation $c>1$. For the Hamming space, we obtain an exponent of $\rho=\tfrac{1}{2c-1}$. Our result completes the direction set forth in [AINR14] who gave a proof-of-concept that data-dependent hashing can outperform classical Locality Sensitive Hashing (LSH). In contrast to [AINR14], the new bound is not only optimal, but in fact improves over the best (optimal) LSH data structures [IM98,AI06] for all approximation factors $c>1$. From the technical perspective, we proceed by decomposing an arbitrary dataset into several subsets that are, in a certain sense, pseudo-random.Comment: 36 pages, 5 figures, an extended abstract appeared in the proceedings of the 47th ACM Symposium on Theory of Computing (STOC 2015

Using the PUMA System

This document describes the operation of the Lisp Machine interface to the Unimation Puma 600 Robot Arm. The interface is evolved from a system described in an earlier paper, and much is the same. However, the under-lying interface between the Lisp Machine and the Puma has changed and some enhancements have been made. VAL has been replaced with a PDP-11/23, communicating with the Lisp Machine over the Chaosnet. The purpose of this document is to provide instruction and information in the programming of the Puma arm from the Lisp Machine. The network protocol is not described here, nor are the internals of the implementation. These details are provided in separate documentation. The reader will find in this paper both a tutorial section and a reference section. The tutorial will lead the reader through a sample session using the Puma by directly calling the primitive operations, and will provide an introduction to programming using the primitives. The reference section provides an overview of the network protocol and describes all of the primitive operations provided. Please note that this document corresponds to the version of the Puma system in use on 11 March, 1985. The system is still undergoing development and enhancement, and there may be additional features, if you are running a newer system. The authors welcome reports of errors, inaccuracies, or suggestions for clarification or improvement in either the documentation or the code for the Puma system. Please send electronic mail to [email protected] Artificial Intelligence Laborator