2,463 research outputs found
A comparison of community structure in regulated and unregulated reaches in the Upper Eel River, California
Flow regulation of rivers by impoundments and diversions can reduce hydrological variability. As a result, densities of algae and benthic macroinvertebrates often increase, but many sensitive taxa are lost, causing shifts across the food web. In Northern California, dams that reduce winter peak floods can result in the primary consumer community becoming dominated by grazers that are relatively invulnerable to predation, which can reduce the amount of energy transferred up the trophic levels. The steeper slope of the spring hydrograph recession limb downstream of a dam can also greatly impact instream diversity of periphyton, invertebrates and fish. The dam and diversion system on the upper Mainstem Eel River in Northern California has direct impacts on endangered salmon populations, but the effects of the dams on the greater ecosystem are not well understood. This study compared the seasonal algal and benthic macroinvertebrate communities from the Mainstem Eel River below Cape Horn Dam to that of the unregulated Middle Fork Eel River. The 2017 water year had above average rainfall, with several bankfull flows observed in the winter as well as elevated base flows in the summer in both rivers. Despite the wet water year in 2017, the regulation of flows by the dams still likely produced a shorter spring recession limb and, more importantly, a delay in peak summer temperatures in the Mainstem relative to the Middle Fork. Although the abundance and diversity of invertebrates were not notably different between the regulated and unregulated rivers, there did appear to be a variation in the food webs. By mid-summer, the unregulated Middle Fork developed into an ecosystem predominated by Cladophora and its epiphytes with numerous invertebrate grazers. Yet the Mainstem, especially immediately below the dam with the encroachment of vegetation, had less growth of the filamentous green algae (t(20)=4.61, p=0.0002) with lower mid-summer algal richness ((20)=2.53, p= 0.020), resulting in an invertebrate community more reliant on filtering fine organic matter with far fewer grazers (pCladophoraas well as the abundance and development of some key macroinvertebrate taxa, such as midges and small minnow mayflies relative to an unregulated reach. As the Middle Fork is an inherently warmer system, future studies are needed across a longitudinal gradient of the Mainstem over multiple water years to capture interannual variation and to ultimately determine the influence of the dams on riverine ecosystems
Drivers and Dynamics of Phytoplankton Communities and Harmful Algal Blooms in Mountain Lakes
Harmful cyanobacterial blooms (cyanoHABs) are a complex and widespread disturbance in freshwater water bodies, impacting water quality for wildlife and human populations. While cyanobacteria often bloom in warm lakes impacted by human development like agriculture, blooms are increasingly reported in cooler waters with limited development in the surrounding watershed. As much of cyanoHAB research has focused on lakes in highly developed watersheds, the understanding of factors leading to cyanobacteria dominance and blooms in the absence of major development remains limited. Mountain lakes can serve as ideal systems to study bloom-forming cyanobacteria in watersheds with minimal development. In addition, mountain lakes span natural gradients of productivity and climate due to the varied elevation and topography. Mountain lakes are also highly valued for recreation and habitat for sensitive species due to perceived pristine conditions, but are vulnerable to multiple stressors such as climate warming and increased atmospheric deposition of nutrients, which limit cyanobacteria growth. Therefore, the potential for cyanoHABs in mountain lakes is likely to rise in the near future, making it crucial to understand the drivers of cyanobacteria dominance and blooms in these sensitive lakes.
The goal of this dissertation is to improve the understanding of drivers and dynamics of bloom-forming cyanobacteria in mountain lakes, including factors across lake to watershed scales, to temporal and spatial patterns in planktonic communities. I conducted field surveys to examine the physical and chemical conditions as well as the phytoplankton and other key biological communities in a set of Cascade Mountain lakes located in Oregon, USA. In Chapter 2, I used survey data and existing geospatial data to identify food web, lake, and watershed drivers, as well as interactions among drivers across scales on nitrogen (N)-fixing cyanobacteria, the common cyanoHAB taxa in the region. In Chapter 3, I examined the intra- and inter-annual variation in cyanoHABs and cyanotoxins relative to meteorological conditions and the bacterioplankton communities. Based on genetic sequencing and time integrated toxin monitoring, I determined possible temporal relationships and biological indicators of blooms and bloom toxicity. In Chapter 4, I used survey data as along with existing and interpolated trait data to assess how the top-down and bottom-up effects of grazing zooplankton and nutrients could have shaped phytoplankton communities functionally. I discuss the resulting implications for bloom-forming cyanobacteria dominance over other phytoplankton.
I identified watershed size and hypolimnetic dissolved oxygen as key drivers of N-fixing cyanobacteria biomass likely through the regulation of limiting nutrients such as phosphorus. Temperature and rainfall did not correspond strongly to the blooms and toxins of N-fixing cyanobacteria across lakes, suggesting other meteorological factors as well as lake productivity may be more important. Yet further study is needed with high-frequency sampling and better characterization of meteorological conditions. In terms of the food web, I found grazing cladocerans were a significant factor for N-fixing cyanobacteria, likely via consumption of other phytoplankton. These grazers may be in turn influenced by fish populations. I also found additional biological indicators for cyanobacteria blooms as well as bloom toxicity in heterotrophic bacteria. Finally, I found high grazer abundances favor fast growing and small unicellular phytoplankton at relatively low nutrients, while increasing phosphorus favors colonial cyanobacteria capable of toxin production, such as N-fixing taxa. At high levels of grazers and phosphorus, toxigenic cyanobacteria likely dominate phytoplankton communities in mountain lakes.
This dissertation sheds light on the key factors and indicators for N-fixing cyanobacteria dominance and cyanoHABs in mountain lakes. My results suggest that lake management agencies must consider how both landscape and within-lake factors may affect the risk for cyanoHABs, and how fish stocking increases risk via their impact on grazing zooplankton biomass and body size. As mountain lake monitoring is limited, my results suggest genetic identification of bacterial communities may provide a more time-integrated way to assess bloom development and toxicity. Determining how abiotic and biotic factors interact is needed to broaden management approaches since strict nutrient reduction programs have had mixed success in reducing cyanoHABs in lakes
Regulating online games in China: policy, practice, innovation, and change
The policy and practice of media regulation in China is quickly evolving to cope with the
regulatory challenges presented by the rapid development and convergence of new media
technology. These challenges include the increasing economic power of international and
private stakeholders within this space, as well as the constantly evolving uses of highly
converged media. Online games are a central part of this evolving dynamic, which is
characterized by strong tensions between producers and operators, government regulators,
and users of online games. This research explores the changing dynamic of online games
regulation in China as it responds to the forces of internationalization and privatization. It also
seeks to identify critical issues for policy development in China that are raised by the new and
innovative ways that this media is being used. It draws from and contributes to scholarship
from a number of disciplines, but primarily approaches the research from a media studies and
area studies perspective.
The thesis is presented in five chapters. Chapter I begins with a discussion of emerging
practice in online games and its wider policy implications. This is followed by a literature review
and an explanation of the methodological approach, which included: case study methodology,
participant observation, and key informant Interviews with policy, legal, and game industry
experts in China. The core research is then presented in three chapters. Chapter II is a detailed
contextual narrative that describes China’s online games policy and places it in historical
perspective. Chapter III is an exploratory analysis of key institutions, stakeholder interests,
and interactions that shape practical regulation of online games in China. Chapter IV presents
a focused analysis and discussion of the gold farming case. The thesis concludes with a
summary and discussion of research contributions in Chapter V. The final discussion highlights
how the thesis contributes to knowledge in three key areas: new media in China, policy studies
of China, and media convergence
Optimal entanglement distribution policies in homogeneous repeater chains with cutoffs
We study the limits of bipartite entanglement distribution using a chain of
quantum repeaters that have quantum memories. To generate end-to-end
entanglement, each node can attempt the generation of an entangled link with a
neighbor, or perform an entanglement swapping measurement. A maximum storage
time, known as cutoff, is enforced on the memories to ensure high-quality
entanglement. Nodes follow a policy that determines when to perform each
operation. Global-knowledge policies take into account all the information
about the entanglement already produced. Here, we find global-knowledge
policies that minimize the expected time to produce end-to-end entanglement.
Our methods are based on Markov decision processes and value and policy
iteration. We compare optimal policies to a policy in which nodes only use
local information. We find that the advantage in expected delivery time
provided by an optimal global-knowledge policy increases with increasing number
of nodes and decreasing probability of successful swapping. Our work sheds
light on how to distribute entangled pairs in large quantum networks using a
chain of intermediate repeaters with cutoffs.Comment: 9 pages, 8 figures, 15 pages appendix with 10 figure
Análisis crítico y comparado de la regulación de las concentraciones de mercado en el ordenamiento jurídico peruano y sus consecuencias prácticas
Partiendo de la permisibilidad de las concentraciones empresariales en el marco
normativo peruano, la presente investigación se centra en realizar un análisis crítico de
la regulación, histórica y actual, de las concentraciones empresariales y el impacto que
ha tenido en la economía y el ordenamiento jurídico peruano. Sin limitarse al antecedente
regulatorio, la investigación también evalúa el reciente Decreto de Urgencia 013-2019,
Decreto de Urgencia que establece el control previo de operaciones de concentración
empresarial, particularmente desde una perspectiva comparativa, a efectos de hacer
hincapié en las posibles deficiencias regulatorias que existen respecto este tema. Por lo
tanto, el objetivo de la investigación es cuestionar y evaluar la falta de regulación
histórica, en conjunto con la reciente regulación, que han permitido la generación de
concentraciones empresariales a gran escala. En ese sentido, plantea un número de
ejemplos prácticos, tales como la concentración empresarial existente en la industria
cervecera y en el sistema previsional, los cuales analiza a través de indicadores
económicos. La investigación sustenta sus argumentos en diversas fuentes, pero
particularmente en las normativas, ambas nacionales e internacionales, las opiniones
jurídicas y doctrinarias, la jurisprudencia y los indicadores de índole económica. Lo
anterior en tanto la concentración empresarial es un tema complejo que solo puede ser
adecuadamente explicado a través de un enfoque interdisciplinario. Todo lo anterior lleva
a la conclusión de que evidentemente, el mercado peruano ha sido uno históricamente
dotado con libre competencia y sin interferencia administrativa, lo que ha permitido
grandes conglomeraciones empresariales que hoy en día representan porcentajes
elevados de concentración del mercado, al punto de consolidaciones de monopolios y
oligopolios que afectaran, actualmente y a futuro, a los consumidores y el rumbo del
desarrollo económico, sobre todo el crecimiento de las pequeñas y medianas empresas
del país.Given the permissibility of corporate concentrations in the Peruvian legal framework,
this research paper focuses providing a critical analysis of the historical and current
regulation of corporate concentrations and the impact it has had on the Peruvian economy
and legal system. Without limiting itself to analyzing the previous regulations, this
research also delves into the recent Emergency Decree 013-2019, which establishes
previous control of corporate concentration operations, particularly from a comparative
perspective so as to highlight possible regulatory deficiencies in this area. Therefore, the
objective of this research is to question and evaluate the historical lack of regulation,
together with the recent regulation, which has allowed for large-scale corporate
concentrations. In this regard, it raises a number of practical examples, such as the
existing corporate concentrations in the beer industry and the pension system, which it
analyzes through economic indicators. The research bases its arguments on diverse
sources, but particularly on regulations, both national and international, legal and doctrinal
opinions, case-law and economic indicators. The foregoing insofar as corporate
concentrations are a complex issue that can only be adequately explained through an
interdisciplinary approach. All of the above leads to the conclusion that the Peruvian
market has historically had free competition without administrative interference, which
has allowed large corporate conglomerations that represent highly concentrated
percentages of today’s market, to the point of consolidation of monopolies and oligopolies
that will affect, currently and in the future, consumers and the development of the
economy, especially the growth of the country's small and medium businesses
Identidad intercultural en jóvenes hijos de padres provincianos-migrantes : influencia de la comunicación de relatos de vida
En la presente investigación busco conocer la forma en la que en las relaciones
interpersonales familiares (padres - hijos), a través de las distintas formas de relatos,
pueden ir formando la identidad de las futuras generaciones. Esto en tanto los hijos se
comprendan como fruto o no de una interculturalidad a partir de la comunicación de
relatos de vida (en provincia y de migración) de sus padres, más allá de la influencia
diaria y directa de otros factores de su entorno capitalino.
Para ello, me he centrado en un grupo de jóvenes hijos de provincianos - migrantes,
los cuales pertenecen al distrito de Los Olivos y se encuentran entre las edades de 19
y 25 años. Este distrito lo escogí para la investigación, pues la gran mayoría de sus
pobladores son migrantes o hijos de migrantes (MOL, 2012). Cabe mencionar que
también he entrevistado a dos de los padres provincianos-migrantes de los jóvenes
antes mencionados, con el fin de obtener información de soporte para el análisis.Tesi
Policy and Procedure: Clinical Management of Human Trafficking Patients and/or Those at Risk for Exploitation
The Ohio Attorney General’s Office in its fight against human trafficking has created a Human Trafficking Initiative. Part of this initiative is the development of publications to assist providers in the care of and/or recognition of trafficked patients, data collection, and/or standards of service. This healthcare policy template is both evidence based and survivor informed. It will help to assist providers in understanding the basic guidelines of clinical management for human trafficking patients and/or those at risk for exploitation. This resource in addition to others can be found on the Ohio Attorney General’s website and is available to download and adopt as a reference/template for the development of healthcare policy and procedures
- …