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Search Results: 1 - 10 of 1059 matches for " Heloise Pham "
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Learning lessons from field surveys in humanitarian contexts: a case study of field surveys conducted in North Kivu, DRC 2006-2008
Rebecca F Grais, Francisco J Luquero, Emmanuel Grellety, Heloise Pham, Benjamin Coghlan, Pierre Salignon
Conflict and Health , 2009, DOI: 10.1186/1752-1505-3-8
Abstract: In media and agency reports on complex emergencies, an estimate of the number of people who have died, the prevalence of childhood malnutrition and other key health indicators are often quoted. Although a discriminating reader may understand that these are estimates, we rarely question how or from where these numbers come. In most cases, estimates are obtained by means of field surveys which are subject to a number of limitations. In the past, the application of standard survey methods by various humanitarian actors has been criticised [1]. Currently, different methods of conducting field surveys are the subject of debate among epidemiologists and their strengths and weakness have been described in the literature [2-6]. Beyond the technical arguments, decision makers may find it difficult to conceptualize what the estimates actually mean. For instance, what makes this particular situation an emergency? And how should the operational response - humanitarian, political, even military - be adapted accordingly [7,8]? This brings into question not only the quality of the survey methodology, but also the difficulties epidemiologists face in interpreting results and selecting the most important information to guide operations.As a case study, we reviewed publicly available field surveys of a current acute-on-chronic humanitarian crisis - North Kivu, Democratic Republic of Congo (DRC) - to examine the methodologies employed, the findings presented, the interpretation of the results and the recommendations made. The eastern DRC Province of North Kivu has been the scene of conflict that has erupted sporadically for over a decade (Figure 1). The most recent renewal of violence has forced some 250,000 people to flee their homes since August 2008 [9].We searched PubMed/Medline for articles published from January 1, 2006 to January 1, 2009, in English, French, German, and Spanish using the key words ["mortality" (major topic) OR "nutrition" (major topic)] AND ["Congo" (text word)
Forestry Alters Foraging Efficiency and Crop Contents of Aphid-Tending Red Wood Ants, Formica aquilonia
Therese Johansson, Heloise Gibb
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032817
Abstract: Forest management alters species behaviours, distributions and interactions. To evaluate forestry effects on ant foraging performance, we compared the quality and quantity of honeydew harvested by ants among clear-cuts, middle-aged and mature spruce-dominated stands in boreal forests in Sweden. Honeydew quality was examined using honeydew collected by squeezing the gasters of laden Formica aquilonia workers. We used fifteen laden individuals at each study site (four replicates of each stand age) and analysed honeydew chemical composition with gas chromatography-mass spectroscopy. To compare the quantity of honeydew collected by individual ants, we collected and weighed five ants moving up and five ants moving down each of ten trees at the twelve sites (totally 1200 ants). The concentration of trehalose in honeydew was lower in clear-cuts compared with middle aged and mature stands, and similar trends were shown for sucrose, raffinose and melezitose, indicating poorer honeydew quality on clear cuts. Concentrations of the amino acid serine were higher on clear-cuts. The same trend occurred for glutamine, suggesting that increased N-uptake by the trees after clear cutting is reflected in the honeydew of aphids. Ants in mature stands had larger heads and carried proportionally more honeydew and may therefore be more efficient foragers. Human alternation of habitats through clear-cutting thus affects food quality and worker condition in F. aquilonia. This is the first study to show that honeydew quality is affected by anthropogenic disturbances, likely contributing to the reduction in size and abundance of F. aquilonia workers and mounds after clear cutting.
Competing Valence Bond States of Spin-3/2 Fermions on a Strongly Coupled Ladder
Edina Szirmai,Heloise Nonne
Physics , 2014, DOI: 10.1103/PhysRevB.90.245135
Abstract: We study the possible ground state configurations of two strongly coupled chains of charge neutral spin-3/2 fermionic atoms interacting via short range van der Waals interaction. The coupling between the two chains is realized by relatively large hopping amplitude. Exploiting that such a ladder configuration can be mapped to an effective one-band model we analyze the emerging ground states of the system. We show that various spatially inhomogeneous states, valence bond states, plaquette states compete depending on the filling and the ratio of the interaction strengths in the singlet and quintet scattering channel. We find that a Luttinger liquid state is the ground state of the strongly coupled ladder in an extended region of the parameter space, and we also show that a topologically nontrivial charge Haldane state can emerge in the strongly coupled ladder at quarter and three-quarter fillings.
Comparisons of VAR Model and Models Created by Genetic Programming in Consumer Price Index Prediction in Vietnam  [PDF]
Pham Van Khanh
Open Journal of Statistics (OJS) , 2012, DOI: 10.4236/ojs.2012.23029
Abstract: In this paper, we present an application of Genetic Programming (GP) to Vietnamese CPI in?ation one-step prediction problem. This is a new approach in building a good forecasting model, and then applying inflation forecasts in Vietnam in current stage. The study introduces the within-sample and the out-of-samples one-step-ahead forecast errors which have positive correlation and approximate to a linear function with positive slope in prediction models by GP. We also build Vector Autoregression (VAR) model to forecast CPI in quaterly data and compare with the models created by GP. The experimental results show that the Genetic Programming can produce the prediction models having better accuracy than Vector Autoregression models. We have no relavant variables (m2, ex) of monthly data in the VAR model, so no prediction results exist to compare with models created by GP and we just forecast CPI basing on models of GP with previous data of CPI.
Optimal Stopping Time for Holding an Asset  [PDF]
Pham Van Khanh
American Journal of Operations Research (AJOR) , 2012, DOI: 10.4236/ajor.2012.24062
Abstract: In this paper, we consider the problem to determine the optimal time to sell an asset that its price conforms to the Black-Schole model but its drift is a discrete random variable taking one of two given values and this probability distribution behavior changes chronologically. The result of finding the optimal strategy to sell the asset is the first time asset price falling into deterministic time-dependent boundary. Moreover, the boundary is represented by an increasing and continuous monotone function satisfying a nonlinear integral equation. We also conduct to find the empirical optimization boundary and simulate the asset price process.
Clinical Implementation of a 3D Dosimeter for Accurate IMRT and VMAT Patient Specific QA  [PDF]
Thuc Pham, Jianjie Luo
Open Journal of Biophysics (OJBIPHY) , 2013, DOI: 10.4236/ojbiphy.2013.31A013

The Delta4 3D dose verification device was commissioned in the current work for pre-treatment quality assurance (QA) of Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) plans. The cross calibration and relative array calibration were performed to enable absolute dose comparison. The linearity of response with dose and temperature sensitivity tests were also conducted to investigate dosimetric properties of the Delta4 device. The need to modify the original CT image of the Delta4 phantom for accurate dose calculation and comparison is addressed in this work, applying a CT extension algorithm. A number of test plans varying from simple 4—field conformal to IMRT and VMAT plans were measured to evaluate the accuracy of this device. It was found that the Delta4 device measured dose accurately to within ±1%. In order to maintain this level of accuracy the machine output fluctuations need to be corrected prior to each measurement and the relative array calibration needs to be performed every six months.

The First Order Autoregressive Model with Coefficient Contains Non-Negative Random Elements: Simulation and Esimation  [PDF]
Pham Van Khanh
Open Journal of Statistics (OJS) , 2012, DOI: 10.4236/ojs.2012.25064
Abstract: This paper considered an autoregressive time series where the slope contains random components with non-negative values. The authors determine the stationary condition of the series to estimate its parameters by the quasi-maximum likelihood method. The authors also simulates and estimates the coefficients of the simulation chain. In this paper, we consider modeling and forecasting gold chain on the free market in Hanoi, Vietnam.
Dynamic Relay Selection Method for Distributed MIMO Relay System  [PDF]
Pham Thanh Hiep
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.54036

The research on distributed MIMO relay system has been attracting much attention. In this paper, a decode-and-forward scheme distributed MIMO relay system is examined. For upper bound of channel capacity, the distance between transceivers is optimized when the propagation loss is brought close to actuality. Additionally, the number of relay is optimized whether total antenna element is fixed or not. When the number of relay is assumed to be infinite, the dynamic relay selection method based on the transmission rate is proposed. We represent that with the proposed method, the transmit power and the number of relays are saving.

Combined Carbon Dioxide Laser Lateral Canthotomy and Femtosecond Laser-Assisted Cataract Surgery  [PDF]
Randal Tanh Hoang Pham
Modern Plastic Surgery (MPS) , 2013, DOI: 10.4236/mps.2013.34027

Purpose: The purpose of this study was to evaluate a new procedure aimed at lengthening the palpebral fissure to facilitate femtosecond laser-assisted cataract surgery in patients with small eyes. Method: A quick procedure using the CO2 laser was adapted for patients with small eyes undergoing laser-assisted cataract surgery using the Catalys system. The UniPulse CO2 laser (Nidek) was used for laser lateral canthotomy on patients with small palpebral fissures to allow fitting of the Liquid OpticTM Interface eyepiece. Results: Lateral canthotomies were performed on 19 women and 7 men (ages ranged from 45 to 93 years) with lower eyelid lengths equal to or shorter than 32 mm who then underwent femtosecond laser-assisted cataract surgery. A total of 33 eyelids received laser lateral canthotomy with the CO2 laser; only one eyelid had lateral canthotomy with cold-steel tenotomy scissors. Dockings were completed for all 34 eyes with eyelids receiving lateral canthotomies. The 33 eyes with eyelids that received laser canthotomy with the CO2 laser had successful femtosecond laser-assisted cataract surgery. The one eye with the eyelid that received cold-steel canthotomy could not have femtosecond laser-assisted cataract surgery despite successful docking because of pupillary constriction. The findings were statistically significant; Fisher Exact Test showed a p-value of 0.0294. Conclusion: Laser lateral canthotomy with CO2 laser is a safe and effective method to allow docking and completion of femtosecond laser-assisted cataract surgery.

Influence of Microstructural Changes on Some Macro Physical Properties of Cement Mortar during Accelerated Carbonation  [PDF]
Son Tung Pham
Open Journal of Civil Engineering (OJCE) , 2014, DOI: 10.4236/ojce.2014.42008

The objective of this work was to examine the changes in the microstructure and macro physical properties caused by the carbonation of normalised CEM II mortar. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity and 20% CO2 concentration. On the microstructure scale, the evolutions of the cumulative pore volume, pore size distribution, and specific surface area during carbonation were calculated from the adsorption desorption isotherms of nitrogen. We also examined the evolution of macro physical properties such as the solid phase volume using helium pycnometry, porosity accessible to water, gas permeability, and thermal conductivity. The conflict between nitrogen porosity and water porosity results indicated that the porous domains explored using these two techniques are different and help to complementarily evaluate the effects of carbonation. This is a multi-scale study where results on microstructural changes can help to explain the evolution of macro physical properties.

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