4,273 research outputs found
Technical support for creating an artificial intelligence system for feature extraction and experimental design
Techniques for classifying objects into groups or clases go under many different names including, most commonly, cluster analysis. Mathematically, the general problem is to find a best mapping of objects into an index set consisting of class identifiers. When an a priori grouping of objects exists, the process of deriving the classification rules from samples of classified objects is known as discrimination. When such rules are applied to objects of unknown class, the process is denoted classification. The specific problem addressed involves the group classification of a set of objects that are each associated with a series of measurements (ratio, interval, ordinal, or nominal levels of measurement). Each measurement produces one variable in a multidimensional variable space. Cluster analysis techniques are reviewed and methods for incuding geographic location, distance measures, and spatial pattern (distribution) as parameters in clustering are examined. For the case of patterning, measures of spatial autocorrelation are discussed in terms of the kind of data (nominal, ordinal, or interval scaled) to which they may be applied
The Impact of Tenure on Chief Executive Officer Role Perceptions and Time Spent in Roles
This paper presents research on the impact of Chief Executive Officer (CEO) tenure, or time worked as a CEO, on the CEO’s perception of their role. For purposes of this paper tenure refers to the amount of time the CEO has spent working as a CEO. Tenure was broken into four major categories: 0 to 10 years; 11 to 20 years; 21 to 30 years; and over 31 years spent as a CEO. In terms of role agreement results indicate a statistically significant difference in agreement with the strategic role category for CEOs with over 31 years of tenure. These CEOs do not agree as strongly with their counterparts that this is a CEO’s role. In terms of time spent in the role categories there are statistically significant differences in CEOs with over 31 years of tenure and their counterparts in how they estimate they spend their time. Further research is necessary to understand the reasons behind these quantitative results
The Development of an Instrument for Measuring Role Perceptions of U.S. Chief Executive Officers
This paper presents the development and initial validation of an instrument intended to measure ChiefExecutive Officers’ (CEOs) perceptions about their roles. Additionally, the instrument was used togather data about how much time CEOs spent in six categories of roles. This research describesinstrument development using preliminary validity assessments with Exploratory Factor Analysis (EFA).Constant comparative analysis was also utilized to group 31 roles of CEOs into six categories of rolesfor purposes of requesting time estimates. It is concluded there is good preliminary evidence foremerging factor structures however more data needs to be collected from CEOs in locations other thanthe United States to support further development of a predictable instrument
Recent developments in the study of plant microbiomes
To date, an understanding of how plant growth-promoting bacteria facilitate plant growth has been primarily based on studies of individual bacteria interacting with plants under different conditions. More recently, it has become clear that specific soil microorganisms interact with one another in consortia with the collective being responsible for the positive effects on plant growth. Different plants attract different cross-sections of the bacteria and fungi in the soil, initially based on the composition of the unique root exudates from each plant. Thus, plants mostly attract those microorganisms that are beneficial to plants and exclude those that are potentially pathogenic. Beneficial bacterial consortia not only help to promote plant growth, these consortia also protect plants from a wide range of direct and indirect environmental stresses. Moreover, it is currently possible to engineer plant seeds to contain desired bacterial strains and thereby benefit the next generation of plants. In this way, it may no longer be necessary to deliver beneficial microbiota to each individual growing plant. As we develop a better understanding of beneficial bacterial microbiomes, it may become possible to develop synthetic microbiomes where compatible bacteria work together to facilitate plant growth under a wide range of natural conditions
The use of plant growth-promoting bacteria to prevent nematode damage to plants
Plant-parasitic nematodes have been estimated to annually cause around US $173 billion in damage to plant crops worldwide. Moreover, with global climate change, it has been suggested that the damage to crops from nematodes is likely to increase in the future. Currently, a variety of potentially dangerous and toxic chemical agents are used to limit the damage to crops by plant-parasitic nematodes. As an alternative to chemicals and a more environmentally friendly means of decreasing nematode damage to plants, researchers have begun to examine the possible use of various soil bacteria, including plant growth-promoting bacteria (PGPB). Here, the current literature on some of the major mechanisms employed by these soil bacteria is examined. It is expected that within the next 5\u201310 years, as scientists continue to elaborate the mechanisms used by these bacteria, biocontrol soil bacteria will gradually replace the use of chemicals as nematicides
Heterogeneous microbial community associated with Bursaphelenchus xylophilus
Pine wilt disease (PWD) is a complex disease integrating three major factors: the causal agent, the pinewood nematode Bursaphelenchus xylophilus; the insect-vector Monochamus spp.; and the host pine tree, Pinus sp. Since the early 80’s, the notion that another pathogenic agent involved, namely bacteria, may play a role in PWD has been gaining traction, however the role of bacteria in PWD is still unknown. The present work suggests the intriguing possibility that some B. xylophilus-associated bacteria may play a significant role in the development of this disease. This is inferred as a consequence of: (i) the phenotypic characterization, of a collection of 35 isolates of B. xylophilus-associated bacteria, in different tests broadly used to test plant pathogenic and plant growth promoting bacteria, and (ii) greenhouse experiments that infer pathogenicity of these bacteria in in maritime pine, Pinus pinaster. The results illustrate the presence of a heterogeneous microbial community associated with B. xylophilus and the traits exhibited by at least some of these bacteria appear to be related to PWD symptoms. The inoculation of four specific B. xylophilus-associated bacteria in P. pinaster seedlings resulted in the development of some PWD symptoms suggesting that these bacteria likely play an active role with B. xylophilus in PWD
Evidence for the involvement of ACC deaminase from Pseudomonas putida UW4 in the biocontrol of pine wilt disease caused by Bursaphelenchus xylophilus
Abstract Pine wilt disease, caused by the nematode
Bursaphelenchus xylophilus, is responsible for devastation
of pine forests worldwide. Until now, there are no
effective ways of dealing with this serious threat. The
use of 1-aminocyclopropane-1-carboxylate (ACC)
deaminase (encoded by the acdS gene)-producing plant
growth-promoting bacteria has been shown to be a
useful strategy to reduce the damage due to biotic and
abiotic stresses. Pinus pinaster seedlings inoculated
with the ACC deaminase-producing bacterium Pseudomonas
putida strain UW4 showed an increased root
and shoot development and reduction of B. xylophilus
induced symptoms. In contrast, a P. putida UW4 acdS
mutant was unable to promote pine seedling growth or
to decrease B. xylophilus induced symptoms. This is the
first report on the use of ACC deaminase-producing
bacteria as a potential biological control agent for a tree
disease, thus suggesting that the inoculation of pine
seedlings grown in a tree nursery might constitute a
novel strategy to obtain B. xylophilus resistant pine
trees
Production of bioemulsifier by an unusual isolate of salmon/red melanin containing Rhodotorula glutinis
An unusual isolate of Rhodotorula glutinis was obtained. The yeast produces a spore and a crystalliferous protein per cell. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the parasporal crystals contained polypeptides with a molecular mass of approximately 55, 47, 40, 36 32.5, 30 and 25 kD. The yeast also produces a salmon/red pigment at late stage of exponential growth, which has physical and chemical properties that are consistent with it being a form of melanin. The organism has been used to produce bioemulsifier with emulsion index of 80% when tested against kerosene and crude oil. The bioemulsifier has been shown to be capable of eliminating about 76% of crude oil pollutant. The colonial and mycelia forms of Rhodosporidium toruloides and Rhodosporidium sphaerocarpum have been successfully isolated from the unusual organism.African Journal of Biotechnology Vol. 4 (2), pp. 164-171, 200
Vitamin Deficiencies Among Resettled Refugees in Buffalo, NY
Background
Vitamin deficiency in the developing world is a considerable public health issue that is often overlooked. Refugees are some of the most vulnerable populations, since they rely almost exclusively on the nutrition provided by refugee camps. Buffalo, NY resettles the fourth largest number of refugees per capita among cities in the United States (US).
Objective
We examined the prevalence of vitamin A, B2, B12, and D deficiencies among refugees who had been recently resettled to Buffalo, NY and referred to our practice for assessment. Our exploratory objective was to examine potential differences in the prevalence of vitamin deficiencies among those living in specific refugee camps.
Methods
Study Design: Retrospective chart review. Study Population: Refugees between the ages of 2 and 75 and resettled in Buffalo between December 2012 and March 2014 who were registered patients at our practice (n=250). Independent Variables: Age, gender, country of origin, country of refugee camp refugee, length of time in US prior to medical evaluation, length of time in refugee camp. Dependent Variables: % of deficiencies among vitamin A, B2, B12 and D levels. Data Analysis: Fisher Exact Test; ANOVA.
Results
There was only one reported case of vitamin A deficiency (0.45%, p=0.37) and only 6 cases of vitamin B2 deficiency (3.4%, p=0.87). Conversely, vitamin B12 and D were deficient in 37.2% (p\u3c0.0001) and 58.9% (p\u3c0.0001) of samples, respectively.
Discussion
There are concerning deficiencies noted for vitamin B12 and D levels among refugees resettled in Buffalo, NY. There was also significant variation in the prevalence of vitamin B12 and D deficiency between countries of refuge. These analyses suggest that vitamin B12 and D deficiency is a considerable issue in refugees resettled in NYS and should be addressed by local clinicians involved in the post-resettlement care of these populations
Mycorrhizal-Bacterial Amelioration of Plant Abiotic and Biotic Stress
Soil microbiota plays an important role in the sustainable production of the different types of agrosystems. Among the members of the plant microbiota, mycorrhizal fungi (MF) and plant growth-promoting bacteria (PGPB) interact in rhizospheric environments leading to additive and/or synergistic effects on plant growth and heath. In this manuscript, the main mechanisms used by MF and PGPB to facilitate plant growth are reviewed, including the improvement of nutrient uptake, and the reduction of ethylene levels or biocontrol of potential pathogens, under both normal and stressful conditions due to abiotic or biotic factors. Finally, it is necessary to expand both research and field use of bioinoculants based on these components and take advantage of their beneficial interactions with plants to alleviate plant stress and improve plant growth and production to satisfy the demand for food for an ever-increasing human population
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