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Search Results: 1 - 10 of 229094 matches for " Joseph C. Gile "
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Improved Bone Morphogenetic Protein-2 Retention in an Injectable Collagen Matrix Using Bifunctional Peptides
Paul T. Hamilton, Michelle S. Jansen, Sathya Ganesan, R. Edward Benson, Robin Hyde-DeRuyscher, Wayne F. Beyer, Joseph C. Gile, Shrikumar A. Nair, Jonathan A. Hodges, Hanne Gr?n
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070715
Abstract: To promote healing of many orthopedic injuries, tissue engineering approaches are being developed that combine growth factors such as Bone Morphogenetic Proteins (BMP) with biomaterial carriers. Although these technologies have shown great promise, they still face limitations. We describe a generalized approach to create target-specific modular peptides that bind growth factors to implantable biomaterials. These bifunctional peptide coatings provide a novel way to modulate biology on the surface of an implant. Using phage display techniques, we have identified peptides that bind with high affinity to BMP-2. The peptides that bind to BMP-2 fall into two different sequence clusters. The first cluster of peptide sequences contains the motif W-X-X-F-X-X-L (where X can be any amino acid) and the second cluster contains the motif F-P-L-K-G. We have synthesized bifunctional peptide linkers that contain BMP-2 and collagen-binding domains. Using a rat ectopic bone formation model, we have injected rhBMP-2 into a collagen matrix with or without a bifunctional BMP-2: collagen peptide (BC-1). The presence of BC-1 significantly increased osteogenic cellular activity, the area of bone formed, and bone maturity at the site of injection. Our results suggest that bifunctional peptides that can simultaneously bind to a growth factor and an implantable biomaterial can be used to control the delivery and release of growth factors at the site of implantation.
Enriching Stakeholder Theory: Student Identity of Higher Education  [PDF]
Joseph W. C. Lau
American Journal of Industrial and Business Management (AJIBM) , 2014, DOI: 10.4236/ajibm.2014.412082
Abstract: While students commonly assume the identity of being key stakeholders of higher education, the present article explores the possible complications stemmed from such key identity. Stakeholder theory has its strengths attributed by its conceptual breath and versatility; the limits of the theory arise for the same merit. Making reference to the theory with no restrains leads reasonably to the conclusion that the educational institute is unwilling to take measure closely to the long term effect, tangible or intangible, of such approach. Providing multiple perspectives on the identity of students are observed, an enrichment of stakeholder theory catering student identity is necessary.
Improved Inference for Respondent-Driven Sampling Data with Application to HIV Prevalence Estimation
Krista J. Gile
Statistics , 2010,
Abstract: Respondent-driven sampling is a form of link-tracing network sampling, which is widely used to study hard-to-reach populations, often to estimate population proportions. Previous treatments of this process have used a with-replacement approximation, which we show induces bias in estimates for large sample fractions and differential network connectedness by characteristic of interest. We present a treatment of respondent-driven sampling as a successive sampling process. Unlike existing representations, our approach respects the essential without-replacement feature of the process, while converging to an existing with-replacement representation for small sample fractions, and to the sample mean for a full-population sample. We present a successive-sampling based estimator for population means based on respondent-driven sampling data, and demonstrate its superior performance when the size of the hidden population is known. We present sensitivity analyses for unknown population sizes. In addition, we note that like other existing estimators, our new estimator is subject to bias induced by the selection of the initial sample. Using data collected among three populations in two countries, we illustrate the application of this approach to populations with varying characteristics. We conclude that the successive sampling estimator improves on existing estimators, and can also be used as a diagnostic tool when population size is not known.
The Effect of Differential Recruitment, Non-response and Non-recruitment on Estimators for Respondent-Driven Sampling
Amber Tomas,Krista J. Gile
Statistics , 2010,
Abstract: Respondent-driven sampling is a widely-used network sampling technique, designed to sample from hard-to-reach populations. Estimation from the resulting samples is an area of active research, with software available to compute at least four estimators of a population proportion. Each estimator is claimed to address deficiencies in previous estimators, however those claims are often unsubstantiated. In this study we provide a simulation-based comparison of five existing estimators, focussing on sampling conditions which a recent estimator is designed to address. We find no estimator consistently out-performs all others, and highlight sampling conditions in which each is to be preferred.
Rapid Increase in Log Populations in Drought-Stressed Mixed-Conifer and Ponderosa Pine Forests in Northern Arizona  [PDF]
Joseph L. Ganey, Scott C. Vojta
Open Journal of Forestry (OJF) , 2012, DOI: 10.4236/ojf.2012.22008
Abstract: Down logs provide important ecosystem services in forests and affect surface fuel loads and fire behavior. Amounts and kinds of logs are influenced by factors such as forest type, disturbance regime, forest management, and climate. To quantify potential short-term changes in log populations during a recent global- climate-change type drought, we sampled logs in mixed-conifer and ponderosa pine (Pinus ponderosa) forests in northern Arizona in 2004 and 2009 (n = 53 and 60 1-ha plots in mixed-conifer and ponderosa pine forests, respectively). Over this short time interval, density of logs, log volume, area covered by logs, and total length of logs increased significantly in both forest types. Increases in all log parameters were greater in mixed-conifer than in ponderosa pine forest, and spatial variability was pronounced in both forest types. These results document rapid increases in log populations in mixed-conifer forest, with smaller changes observed in ponderosa pine forest. These increases were driven by climate-mediated tree mortality which created a pulse in log input, rather than by active forest management. The observed increases will affect wildlife habitat, surface fuel loads, and other ecosystem processes. These changes are likely to continue if climate change results in increased warmth and aridity as predicted, and may require shifts in management emphasis.
Value Stream Management for Lean Office—A Case Study  [PDF]
Joseph C. Chen, Ronald A. Cox
American Journal of Industrial and Business Management (AJIBM) , 2012, DOI: 10.4236/ajibm.2012.22004
Abstract: This paper presents a look at the concept of Lean Manufacturing as applied to the office environment. Lean Manufac- turing, which is often referred to as Lean, is a philosophy of manufacturing process improvement through the elimina- tion of waste. As Lean developed since its origins in the automobile industry, it has been extended to apply to various enterprises and organizations, and has achieved a renowned reputation for reducing waste while adding value to prod- ucts and services. Lean has also been applied in the office environment; however, participants in the implementation of Lean Office face more difficulties because of higher variation in office processes, less foundation information for par- ticipants, and lack of references in literature. This paper addresses these issues by proposing, a systematic proce-dure for conducting Lean Office techniques, along with a case study at a local company. The case study demonstrates a step by step procedure to help more participants in Lean Office understand its benefits and how to get started.
Diurnal and Seasonal Variations of Rain Rate and Rain Attenuation on Ku-Band Satellite Systems in a Tropical Region: A Synthetic Storm Techniques Approach  [PDF]
Joseph S. Ojo, Okeowo C. Rotimi
Journal of Computer and Communications (JCC) , 2015, DOI: 10.4236/jcc.2015.34001
Abstract: In this paper, a time-varying rain characterization and diurnal variation in the Ku-band satellite systems simulated with synthetic storm techniques (SST) over a tropical location in Nigeria have been presented. Three years’ rain rate time-series data measured by a raingauge located inside the Federal University of Technology Akure, Nigeria were utilized for the purpose of this work. The analysis is based on the CDF of one-minute rain rate; time-series simulated annual/seasonal and diurnal rain rate, rain attenuation statistics and fade margins observed over four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00 and 18:00-24:00. In addition, comparison was also made between the synthesized values and rain attenuation statistics, at 12.245 GHz for a hypothetical downlink from EUTELSAT W4/W7 satellite in the area. It could be observed that at 99.99% link availability, the fade margin as high as ~20 dB may be required at Ku band uplink frequency bands in this area. We also observed that the communication downlinks working in the early morning and early to late in the evening hours must be compensated with an appropriate Down-Link Power Control (DLPC) for optimum performances during severe atmospheric influences in the region.
Transcriptomic Analysis Reveals Evidence for a Cryptic Plastid in the Colpodellid Voromonas pontica, a Close Relative of Chromerids and Apicomplexan Parasites
Gillian H. Gile, Claudio H. Slamovits
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0096258
Abstract: Colpodellids are free-living, predatory flagellates, but their close relationship to photosynthetic chromerids and plastid-bearing apicomplexan parasites suggests they were ancestrally photosynthetic. Colpodellids may therefore retain a cryptic plastid, or they may have lost their plastids entirely, like the apicomplexan Cryptosporidium. To find out, we generated transcriptomic data from Voromonas pontica ATCC 50640 and searched for homologs of genes encoding proteins known to function in the apicoplast, the non-photosynthetic plastid of apicomplexans. We found candidate genes from multiple plastid-associated pathways including iron-sulfur cluster assembly, isoprenoid biosynthesis, and tetrapyrrole biosynthesis, along with a plastid-type phosphate transporter gene. Four of these sequences include the 5′ end of the coding region and are predicted to encode a signal peptide and a transit peptide-like region. This is highly suggestive of targeting to a cryptic plastid. We also performed a taxon-rich phylogenetic analysis of small subunit ribosomal RNA sequences from colpodellids and their relatives, which suggests that photosynthesis was lost more than once in colpodellids, and independently in V. pontica and apicomplexans. Colpodellids therefore represent a valuable source of comparative data for understanding the process of plastid reduction in humanity's most deadly parasite.
Respondent-Driven Sampling: An Assessment of Current Methodology
Krista J. Gile,Mark S. Handcock
Statistics , 2009,
Abstract: Respondent-Driven Sampling (RDS) employs a variant of a link-tracing network sampling strategy to collect data from hard-to-reach populations. By tracing the links in the underlying social network, the process exploits the social structure to expand the sample and reduce its dependence on the initial (convenience) sample. The primary goal of RDS is typically to estimate population averages in the hard-to-reach population. The current estimates make strong assumptions in order to treat the data as a probability sample. In particular, we evaluate three critical sensitivities of the estimators: to bias induced by the initial sample, to uncontrollable features of respondent behavior, and to the without-replacement structure of sampling. This paper sounds a cautionary note for the users of RDS. While current RDS methodology is powerful and clever, the favorable statistical properties claimed for the current estimates are shown to be heavily dependent on often unrealistic assumptions.
On the Concept of Snowball Sampling
Mark S. Handcock,Krista J. Gile
Statistics , 2011,
Abstract: This brief comment reflects on the historical and current uses of the term "snowball sampling."
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