966 research outputs found
Evolution of mating system and inbreeding depression in the Mimulus moschatus (Scrophulariaceae) alliance
Thesis (Ph.D.) University of Alaska Fairbanks, 2002The transition from cross- to self-fertilization is considered a major pattern in the evolution of angiosperms. Yet, evolutionists continue to struggle to explain the evolutionary processes involved in maintaining both self- and cross-fertilization, which often occur within the same species. The diversity of mating systems suggests that selective pressures are also diverse, sometimes promoting selfing and other times promoting outcrossing. Inbreeding depression is commonly invoked as the primary selective force balancing the advantages of selfing or promoting outcrossing. The interaction between levels of inbreeding depression and mating system evolution has been fertile ground for both theoretical and empirical studies; however, a long-term patterns and processes remain ambiguous. I examined the relationship of inbreeding depression and outbreeding depression to mating system in a group of closely related Mimulus taxa, specifically incorporating information on their evolutionary relationships. I posed the following questions: Do selfing populations have low inbreeding depression and outcrossing populations have high outbreeding depression? Is selfing an evolutionary 'dead-end'? Are morphological traits correlated with molecular estimates of mating system? How evolutionary labile is mating system and inbreeding depression? Is inbreeding depression negatively correlated with outbreeding depression? Results from this study largely supported theoretical expectations. Inbreeding depression was lowest in the most selfing species and highest in the most outcrossing species. Outbreeding depression was not observed. Many populations actually experienced positive fitness consequences of between-population crosses. The question of selfing species being evolutionary dead-ends remained equivocal. Flower morphology was strongly related to molecular estimates of mating system as expected. Contrary to expectations, inbreeding depression appears to evolve much more quickly than does mating system. I conclude that in the Mimulus moschatus alliance, inbreeding depression is not as strong a selective force as often implied in the evolution of mating system. Although generally low, inbreeding depression can be high in some populations of rare taxa. Outbreeding depression was minimal. Last, inbreeding depression was positively correlated with outbreeding depression, suggesting that mediating the negative effects of inbreeding depression cannot occur by the introduction of foreign genes for many populations
Kikuchi-Fujimoto Disease in a 30-Year-Old Caucasian Female
Kikuchi-Fujimoto disease is a rare, self-limited, histiocytic, necrotizing lymphadenitis first described in Japan in 1972. Necrosis of lymph node tissue is caused by apoptosis and may be virally induced. It commonly presents with cervical lymphadenitis and fever. Despite its low incidence, Kikuchi-Fujimoto disease should be considered in patients with persistent lymphadenopathy. Originally thought to occur only in young Asian women, it is now recognized in other geographic regions. We report a 30-year-old white woman with Kikuchi-Fujimoto disease. We discuss the clinical features, differential diagnosis, radiography, pathology, and outcome
Universal quantum computation using the discrete time quantum walk
A proof that continuous time quantum walks are universal for quantum
computation, using unweighted graphs of low degree, has recently been presented
by Childs [PRL 102 180501 (2009)]. We present a version based instead on the
discrete time quantum walk. We show the discrete time quantum walk is able to
implement the same universal gate set and thus both discrete and continuous
time quantum walks are computational primitives. Additionally we give a set of
components on which the discrete time quantum walk provides perfect state
transfer.Comment: 9 pages, 10 figures. Updated after referee comments - Section V
expanded and minor changes to other parts of the tex
Transcriptome Analysis of a Petal Anthocyanin Polymorphism in the Arctic Mustard, Parrya nudicaulis
Angiosperms are renown for their diversity of flower colors. Often considered adaptations to pollinators, the most common underlying pigments, anthocyanins, are also involved in plants’ stress response. Although the anthocyanin biosynthetic pathway is well characterized across many angiosperms and is composed of a few candidate genes, the consequences of blocking this pathway and producing white flowers has not been investigated at the transcriptome scale. We take a transcriptome-wide approach to compare expression differences between purple and white petal buds in the arctic mustard, Parrya nudicaulis, to determine which genes’ expression are consistently correlated with flower color. Using mRNASeq and de novo transcriptome assembly, we assembled an average of 722 bp per gene (49.81% coding sequence based on the A. thaliana homolog) for 12,795 genes from the petal buds of a pair of purple and white samples. Our results correlate strongly with qRT-PCR analysis of nine candidate genes in the anthocyanin biosynthetic pathway where chalcone synthase has the greatest difference in expression between color morphs (P/W =,76). Among the most consistently differentially expressed genes between purple and white samples, we found 36more genes with higher expression in white petals than in purple petals. These include four unknown genes, two drought-response genes (CDSP32, ERD5), a cold-response gene (GR-RBP2), and a pathogen defense gene (DND1). Gene ontology analysis of the top 2% of genes with greater expression in white relative to purple petals revealed enrichment in genes associated with stress responses including cold, drought and pathogen defense. Unlike the uniform downregulation of chalcone synthase that may be directly involved in the loss of petal anthocyanins, the variable expression of several genes with greater expression in white petals suggest that the physiological and ecological consequences of having white petals may be microenvironment-dependent
Land-use change reduces habitat suitability for supporting managed honey bee colonies in the Northern Great Plains
Human reliance on insect pollination services continues to increase even as pollinator populations exhibit global declines. Increased commodity crop prices and federal subsidies for biofuel crops, such as corn and soybeans, have contributed to rapid land-use change in the US Northern Great Plains (NGP), changes that may jeopardize habitat for honey bees in a part of the country that supports \u3e40% of the US colony stock. We investigated changes in biofuel crop production and grassland land covers surrounding ~18,000 registered commercial apiaries in North and South Dakota from 2006 to 2014. We then developed habitat selection models to identify remotely sensed land-cover and land-use features that influence apiary site selection by Dakota beekeepers. Our study demonstrates a continual increase in biofuel crops, totaling 1.2 Mha, around registered apiary locations in North and South Dakota. Such crops were avoided by commercial beekeepers when selecting apiary sites in this region. Furthermore, our analysis reveals how grasslands that beekeepers target when selecting commercial apiary locations are becoming less common in eastern North and South Dakota, changes that may have lasting impact on pollinator conservation efforts. Our study highlights how land-use change in the NGP is altering the landscape in ways that are seemingly less conducive to beekeeping. Our models can be used to guide future conservation efforts highlighted in the US national pollinator health strategy by identifying areas that support high densities of commercial apiaries and that have exhibited significant land-use changes
Land-use change reduces habitat suitability for supporting managed honey bee colonies in the Northern Great Plains
Human reliance on insect pollination services continues to increase even as pollinator populations exhibit global declines. Increased commodity crop prices and federal subsidies for biofuel crops, such as corn and soybeans, have contributed to rapid land-use change in the US Northern Great Plains (NGP), changes that may jeopardize habitat for honey bees in a part of the country that supports \u3e40% of the US colony stock. We investigated changes in biofuel crop production and grassland land covers surrounding ~18,000 registered commercial apiaries in North and South Dakota from 2006 to 2014. We then developed habitat selection models to identify remotely sensed land-cover and land-use features that influence apiary site selection by Dakota beekeepers. Our study demonstrates a continual increase in biofuel crops, totaling 1.2 Mha, around registered apiary locations in North and South Dakota. Such crops were avoided by commercial beekeepers when selecting apiary sites in this region. Furthermore, our analysis reveals how grasslands that beekeepers target when selecting commercial apiary locations are becoming less common in eastern North and South Dakota, changes that may have lasting impact on pollinator conservation efforts. Our study highlights how land-use change in the NGP is altering the landscape in ways that are seemingly less conducive to beekeeping. Our models can be used to guide future conservation efforts highlighted in the US national pollinator health strategy by identifying areas that support high densities of commercial apiaries and that have exhibited significant land-use changes
The influence of spatiotemporally decoupled land use on honey bee colony health and pollination service delivery
Societal dependence on insects for pollination of agricultural crops has risen amidst concerns over pollinator declines. Habitat loss and lack of forage have been implicated in the decline of both managed and native pollinators. Land use changes in the Northern Great Plains of the US, a region supporting over 1 million honey bee colonies annually, have shifted away from historical grassland ecosystems bees rely on for forage toward landscapes dominated by corn, soybeans, and other row crops. We investigated how land use impacts honey bee colony population size during the growing season and subsequent colony population size for almond pollination in central California the following February.We provide estimates of how land use affects beekeeper economics by linking summer habitat with pollination service payments and later production of new colonies. Our results demonstrate that a greater presence of non-bee foraged agricultural crops surrounding apiaries in the summer results in smaller colonies by the end of the growing season. Apiaries with colonies exhibiting smaller population size in the autumn were also smaller during almond pollination the following spring; impacting the beekeeper with a reduced per-colony rental fee for pollination services and reduced potential for creating new spring colonies, based on prior growing season land use. This study highlights the downstream effects of factors driving land use decisions on the ability of beekeepers to provide robust honey bee colonies to support the pollination industry on a national scale. It also demonstrates the direct linkages between habitat in the Northern Great Plains, bee health, and pollination services rendered elsewhere in the US
Land-use change reduces habitat suitability for supporting managed honey bee colonies in the Northern Great Plains
Human reliance on insect pollination services continues to increase even as pollinator populations exhibit global declines. Increased commodity crop prices and federal subsidies for biofuel crops, such as corn and soybeans, have contributed to rapid land-use change in the US Northern Great Plains (NGP), changes that may jeopardize habitat for honey bees in a part of the country that supports \u3e40% of the US colony stock. We investigated changes in biofuel crop production and grassland land covers surrounding ~18,000 registered commercial apiaries in North and South Dakota from 2006 to 2014. We then developed habitat selection models to identify remotely sensed land-cover and land-use features that influence apiary site selection by Dakota beekeepers. Our study demonstrates a continual increase in biofuel crops, totaling 1.2 Mha, around registered apiary locations in North and South Dakota. Such crops were avoided by commercial beekeepers when selecting apiary sites in this region. Furthermore, our analysis reveals how grasslands that beekeepers target when selecting commercial apiary locations are becoming less common in eastern North and South Dakota, changes that may have lasting impact on pollinator conservation efforts. Our study highlights how land-use change in the NGP is altering the landscape in ways that are seemingly less conducive to beekeeping. Our models can be used to guide future conservation efforts highlighted in the US national pollinator health strategy by identifying areas that support high densities of commercial apiaries and that have exhibited significant land-use changes
Hygienic practices and diarrheal illness among persons living in at-risk settings in Kabul, Afghanistan: a cross-sectional study
Abstract
Background
Sustained civil and military conflict, resulting in large numbers of internally displaced persons (IDP), in combination with rapid urbanization has strained public health and sanitation within cities in Afghanistan. In order to examine the association between preventive sanitary behaviors and diarrhea within two high risk settings located within Kabul, Afghanistan, this study aimed to evaluate the prevalence of hygienic practices and diarrheal illness in an IDP camp and an urban slum.
Methods
In this cross sectional study, a convenience sample of residents of an IDP camp and an urban slum in Kabul, Afghanistan, was used. Participants were asked to describe their hygienic practices and interviewers independently documented household sanitation. The knowledge and attitudes about and practice of hygienic activities to prevent diarrhea were compared between the two settings.
Results
Two hundred participants, 100 from each setting, were enrolled. Knowledge, attitudes, and practices regarding hygienic activities to prevent diarrhea were greater among the slum dwellers than the IDP. Fewer than half of participants washed their hands with soap before eating or after eating: 31 % of slum dwellers washed before eating compared to 11 % of IDPs (P = 0.0050), and 25 % of slum dwellers washed after defecating compared to 4 % of IDPs (P = 0.0020). The IDPs were more likely to share a latrine (P = 0.0144) and less likely to disinfect their latrine than slum dwellers. Diarrhea in the household within the past 3 months was more common in the IDP camp (54 %) than the slum (20 %) (P = 0.0020).
Conclusions
Even though certain sanitary and hygienic practices were more common among slum dwellers than IDPs, the lack of hygienic activities in both setting indicates that interventions to change behavior, like increasing the availability of soap and encouraging hand washing, are needed. Any initiative will have to be developed in the context of pervasive illiteracy among persons in both of these settings.http://deepblue.lib.umich.edu/bitstream/2027.42/134634/1/12879_2016_Article_1789.pd
Timely measles vaccination in Tianjin, China: a cross-sectional study of immunization records and mothers
Abstract
Background
Measles is a highly infectious disease, and timely administration of two doses of vaccine can ensure adequate protection against measles for all ages in a population. This study aims to estimate the proportion of children aged 8 months to 6 years vaccinated on time with measles-containing vaccines (MCV) and vaccinated during the 2008 and 2010 measles supplementary immunization activities. This study also characterizes differences in mean age at vaccination and vaccination timeliness by demographic characteristics, and describes maternal knowledge of measles vaccination.
Methods
Immunization records were selected from a convenience sample of immunization clinics in Tianjin, China. From the records, overall vaccination coverage and timely vaccination coverage were calculated for different demographic groups. Mothers were also interviewed at these clinics to ascertain their knowledge of measles vaccination.
Results
Within the 329 immunization clinic records, child’s birth year and district of residence were found to be significant predictors of different measures of vaccine timeliness. Children born in 2009 had a lower age at MCV dose 2 administration (17.96 months) than children born in 2005 (22.00 months). Children living in Hebei, a district in the urban center of Tianjin were less likely to be vaccinated late than children living in districts further from the urban core of Tianjin. From the 31 interviews with mothers, most women believed that timely vaccination was very important and more than one dose was very necessary; most did not know whether their child needed another dose.
Conclusions
When reviewing MCV coverage in China, most studies do not consider timeliness. However, this study shows that overall vaccination coverage can greatly overestimate vaccination coverage within certain segments of the population, such as young infants.http://deepblue.lib.umich.edu/bitstream/2027.42/109549/1/12889_2014_Article_6997.pd
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