Lambda Coefficient Research Articles

Identification of the Problem in Controlling the Air–Fuel Mixture Ratio (Lambda Coefficient λ) in Small Spark-Ignition Engines for Positive Pressure Ventilators

The air–fuel ratio is a crucial parameter in internal combustion engines that affects optimal engine performance, emissions, fuel efficiency, engine durability, power, and efficiency. Positive pressure ventilators (PPVs) create specific operating conditions for drive units, characterized by a reduced ambient pressure compared to standard atmospheric pressure, which is used to control carburetor-based fuel supply systems. The impact of these conditions was investigated for four commonly used PPVs (with internal combustion engines) in fire services across the European Union (EU), using a lambda (λ), carbon dioxide (CO2), carbon monoxide (CO), and hydrogen carbon (HC) analyser for exhaust gases. All four ventilators were found to operate with lean and very lean mixtures, with their lambda coefficients ranging from 1.6 to 2.2. The conducted tests of the CO2, CO, and HC concentrations in the exhaust gases of all four fans show dependencies consistent with theoretical analyses of the impact of the fuel–air mixture on emissions. It can be observed that as the amount of burned air decreases, the values of CO and HC decrease, while the concentration of CO2 increases with the increase in engine load. Such an operation can accelerate engine wear, increase the emission of harmful exhaust gases, and reduce the effective performance of the device. This condition is attributed to an inadequate design process, where drive units are typically designed to operate within atmospheric pressure conditions, as is common for these engines. However, when operating with a PPV, the fan’s rotor induces significant air movement, leading to a reduction in ambient pressure on the intake side where the engine is located, thereby disrupting its proper operation.

Evaluation of job satisfaction and related factors in wood extraction workers in Gilan province

Introduction: occupational accidents are caused by ignorance of occupational health and safety recommendations, due to the high rate of accidents in the industry of cutting and extracting wood from the forest, this study is necessary to evaluate job satisfaction. Materials and Methods: In this research, job satisfaction was used as a dependent variable and independent variables included age, educational and employment status, type of work, and duration of employment. To determine the conditions of excessive fatigue among forest workers, the index of symptoms of excessive fatigue was used. The number of 100 workers was investigated by a questionnaire, the comparison of independent variables affecting the satisfaction or dissatisfaction of workers with work using discriminant analysis and the Wilks Lambda coefficient, and the comparison of the average opinions of people from different work groups regarding the work situation using Friedman's test was performed. Results: The four variables of duration of employment, age status of workers, employment status, and type of work are suitable for separating two groups satisfied with work and dissatisfied with work. The assessment of complaint rate showed that questions I take care of my family, I am very worried about my health and I am dissatisfied with many things with the highest rates of 84.66%, 70.66%, and 61.33% respectively. They took the complaint to themselves. The results showed that the highest amount of fatigue accumulation index is related to two groups chronic fatigue and general fatigue. The results of the present study show that 47% of forest workers are illiterate in their educational status, which requires a training course for workers to work with cutting tools and machines. The results showed that 41 percent of the people studied liked their jobs. Conclusion: Personal protective equipment is considered a work tool without which it is impossible to do the desired job. Training classes should be held periodically by the safety department for workers and supervisors when needed.

The effect of root orientation on inferior alveolar nerve injury after extraction of impacted mandibular third molars based on propensity score-matched analysis: a retrospective cohort study

BackgroundThe injury of the inferior alveolar nerve (IAN) is one of the most serious complications of impacted mandibular third molars (IMTMs) extraction. The influence of the root orientation of IMTMs on IAN injury is still controversial. A deeper understanding of the risk factors of IAN injury conduces to better prevention of IAN injury. This study aims to explore whether root orientation is an independent risk factor of IAN injury during IMTMs extraction using the statistical strategy of propensity score matching (PSM).MethodsThis retrospective cohort study included 379 patients with 539 cases of high-risk IMTMs screened by panoramic radiography and cone beam computed tomography. The IAN injury incidence after extraction of different groups of IMTMs was analyzed using the chi-square test or Fisher’s exact test. The correlation between third molar root orientation and impaction depth/contact degree with IAN was evaluated by the Lambda coefficient. Based on PSM for balancing confounding factors including age, sex, impaction depth, and contact degree, the effect of root orientation on the incidence of IAN injury was further analyzed using Fisher’s exact test.ResultsThere were significant group differences in IAN injury incidence in impaction depth, root orientation, and contact degree of root-IAC before PSM. Root orientation was correlated with impaction depth and contact degree of root-IAC. After PSM, there were 9 cases with IAN injury and 257 cases without IAN injury. There were significant group differences between the buccal and non-buccal groups after PSM, and the risk of IAN injury was higher when the root was located on the buccal side of IAC (OR = 8.448, RR = 8).ConclusionsRoot orientation is an independent risk factor of IAN injury, and the risk is higher when the root is located on the buccal side of IAC. These findings could help better evaluate the risk of inferior alveolar nerve injury before the extraction of IMTMs.

Characterization of Complex Concentrated Alloys and Their Potential in Car Brake Manufacturing.

The paper studies new materials for brake disks used in car manufacturing. The materials used in the manufacturing of the brake disc must adapt and correlate with the challenges of current society. There is a tremendous interest in the development of a material that has high strength, good heat transfer, corrosion resistance and low density, in order to withstand high-breaking forces, high heat and various adverse environment. Low-density materials improve fuel efficiency and environmental impact. Complex concentrated alloys (CCA) are metallic element mixtures with multi-principal elements, which can respond promisingly to this challenge with their variety of properties. Several compositions were studied through thermodynamic criteria calculations (entropy of mixing, enthalpy of mixing, lambda coefficient, etc.) and CALPHAD modeling, in order to determine appropriate structures. The selected compositions were obtained in an induction furnace with a protective atmosphere and then subjected to an annealing process. Alloy samples presented uniform phase distribution, a high-melting temperature (over 1000 °C), high hardness (1000-1400 HV), good corrosion resistance in 3.5 wt.% NaCl solution (under 0.2 mm/year) and a low density (under 6 g/cm3).

Anxiety level and functional dyspepsia incidence during COVID-19 pandemic

The adaptation process of the learning system, the hospital environment, and the high risk of COVID-19 infection can be stressors for anxiety in clinical clerkship. Through the brain-gut–axis, the interaction of psychological factors, such as anxiety, can trigger symptoms related to functional dyspepsia. This study aimed to determine the relationship between anxiety levels and functional dyspepsia during the COVID-19 pandemic among clinical clerkship students. This research was conducted on clinical clerkship students/young doctors in 2021. This was an observational analytic study with a cross-sectional approach and involved 131 respondents. The hamilton anxiety rating scale (HARS) questionnaire was utilized to quantify the level of anxiety, while functional dyspepsia was measured based on Rome IV criteria. The data were analyzed by the Lambda (λ) coefficient of correlation test. This study revealed a significant relationship between anxiety level and functional dyspepsia during the COVID-19 pandemic.

Comparison of thermal conductivity of foamed geopolymers containing phase change materials

The aim of this work was to investigate the effect of Phase Change Materials on the insulation properties - thermal conductivity coefficient [λ], of fabricated foamed geopolymer panels. Phase Change Materials have been widely reported in the public literature, making them increasingly popular in recent times. PCMs have the ability to accumulate heat, which they can absorb or release due to thermal transformation, which contributes to energy efficiency. This paper presents the results of research on geopolymers based on fly ash with the addition of microencapsulated and macroencapsulated phase change materials (PCMs). Geopolymer composites were prepared by adding 0%, 5%, 10% and 15% PCM and the curing process was carried out at 60°C. Three different phase change materials with melting points of 28°C (MicroCapsPCM28 (Slovenia)) and 25°C and 42°C (PX25 and GR42 (Germany), respectively) were used. All the phase change materials used belong to the paraffin group. The obtained composite sheets were subjected to thermal conductivity tests in 3 temperature ranges (0-20°C; 20-40°C; 30-50°C). The paper also presents the density results of the foamed composites investigated, as well as the visual evaluation and the morphology of the porous structure using scanning electron microscopy. As a result of the study, it was found that foamed geopolymer composites without PCM addition have lambda coefficient values of 0.06 - 0.07 [W/m*K], while with the addition of phase change materials 0.07 - 0.085 [W/m*K]. The obtained test results give the potential to use these materials in construction as insulating materials. The use of these substances in building partitions results in the decrease of daily temperature amplitudes inside the building, as well as in the phase shift of the time of release of stored heat.

Relationship of Nutritional Status with Tuberculosis Lungs of Children Aged 0-5 Years in Surabaya

Background: Tuberculosis or TB is an infectious disease caused by Mycobacterium Tuberculosis, the tenth leading cause of mortality worldwide affecting both children and adults. Indonesia is the third country with the highest case of TB after China and India. Risk factors of this disease such as host immunity, nutritional status, hygiene, humidity, and population density. Objective: To analyze the correlation between nutritional status and the incidence of pulmonary tuberculosis at RSUD Dr. Soetomo Surabaya. Methods: This study is a retrospective analytical observational design with a case-control design. Sampling was taken using purposive sampling and then analyzed using the lambda coefficient contingency test. Results: A total sample of 130 patients was taken then analyzed. The result showed there is a correlation between a child with underweight (p=0,019) and standard (p=0,015) nutritional status and TB incidence. However, there is no correlation between overweight (p=0,259) and obesity (p=0,153) nutritional status and TB incidence. Conclusion: TB is correlated with underweight and standard nutritional status among children under five years.

The Fire Resistance and Heat Conductivity of Natural Construction Material Based on Straw and Numerical Simulation of Building Energy Demand

The motivation for research to help address climate change is a continuous process of searching for eco-friendly materials in the building industry, which will allow minimizing the negative impact of this sector on the environment. The main objective of the paper is to assess the properties of a natural resource such as straw as an eco-friendly material in various variants for use in low-energy demand construction. The research results will fill the knowledge gap in the field of numerical analyses of the energy demand of straw material buildings based on the results of the conducted laboratory tests. A test of a heat transfer coefficient was conducted with different orientation of straw stalks. Then, samples were subject to a fire resistance test to determine material behavior at 1000 °C. During the fire resistance test, the clay-based plaster was ‘burnt out’, which hardened its structure, effectively preventing flames from reaching the insulation layers in the form of straw stalks. As a result of shrinkage (no plaster mesh), the plaster cracked and turned brick-red in color. The insulation layer of straw under the plaster was charred to a depth of 3.0 mm due to the high temperature. However, when the torch was turned off, no fire spread was observed in any layer of the sample. The 3D models of the buildings were created for different eco-friendly materials applied to make external walls. The results of numerical simulation allowed determining the amount of final energy needed to heat the designed building at the level of 26.38 (kWh/m2·year). Conclusions of the above-mentioned tests indicate very good thermal insulating properties determined using the lambda coefficient of 0.069 (W/m·K) and the possible application of straw bales as an alternative for conventional construction. Research has proven that it is possible to construct a building with low energy requirements using natural, easily available waste and completely biodegradable material.

Developing and Evaluating the Psychometric Properties of the Persian Version of Post-traumatic Growth Inventory in Patients With Cancer

Background: Traumatic events could be accompanied by positive personal and psychological changes. However, no scale is available to measure these aspects in patients with cancer. Accordingly, this study aimed at designing and evaluating the psychometric properties of the Persian version of the Post-Traumatic Growth Inventory (P-TGI) in patients with cancer. Methods: According to the quantitative findings of our previous study, 9 items were added to the 21 items of P-TGI. After calculating the Content Validity Index (CVI) and Content Validity Ratio (CVR) coefficients, P-PTGI was finalized with 24 items. A total of 272 eligible patients with cancer who were referred to Shahid Ghazi Hospital in East Azerbaijan Province, Iran for follow-up treatment completed the P-PTGI. The instrument was assessed to determine its construct validity using various indices of Confirmatory Factor Analysis (CFA) and standardized lambda (λ) coefficient, followed by further assessment of the discriminant and convergent validities using the Structural Equation Modeling (SEM). LISREL and SPSS were used for data analysis. Results: According to the results of goodness-of-fit indicators, the 5-dimensional, 24-item P-PTGI model was acceptable. Considering that the values of average variance extracted (AVE=0.53-0.75) were greater than the square of correlation coefficients between the 5 dimensions of P-PTGI, discriminant validity was approved. The convergent validity of the tool was confirmed according to the high lambda standard coefficients (0.50-0.93) between items and their related factors. Additionally, alpha coefficients for 5 dimensions of P-PTGI ranged from 0.84 to 0.93 which confirmed the consistency of the tool. Conclusion: This study revealed that P-PTGI, with 24 items and 5 dimensions, is a valid and reliable tool for assessing PTG in Iranian patients with cancer.

SPALANIE MIESZANINY BENZYNY I ETANOLU

Thanks to the pressure of the Environmental Society, the priority of engine manufacturers is to reduce emissions of harmful substances into the atmosphere and reduce fuel consumption while constantly increasing engine performance. One way to overcome the aforementioned technical and social problems is to use alcohols, natural or synthetic, such as ethanol to power engines. The objectives of manufacturers of alternative fuels is to provide consumers with the opportunity to use their product without changing the parameters of the main units in their vehicles, therefore the stoichiometry of the combustion of fuel mixtures is important, since this parameter can affect the amount of fuel burned, the quality of exhaust gases and the power of the internal combustion engine. Combustion in a car engine is exothermic, which means that a side effect of this chemical reaction is heat released into the environment. The condition for starting the combustion process is the thermal coefficient – for spark ignition engines – a spark, and for diesel engines – heat during compression of the fuel-air mixture. From the above it follows that after the oxidation reaction in the exhaust gases there should be no residual fuel particles, which in turn is an image of stoichiometric combustion. Since the stoichiometric mixture is very difficult to achieve outside laboratory conditions, a distinction is made between a non-greasy mixture (too much oxidizing agent) and a saturated mixture (too little oxidizing agent), but always strive to reach λ = 1, which corresponds to a stoichiometric mixture. The heavy weight when working with ethanol fuel is the one that affects the operation of the engine and its components. Therefore, it is important to compare the physicochemical data of gasoline and ethanol, as well as mixed fuel – E85. The article deals with the stoichiometry of combustion of an alternative fuel - a mixture of gasoline and ethanol. The economic and environmental conditions that initiated the production of this type of fuel were taken into account, the fuel mixtures were divided according to the content of fuel and oxidants in the combustion chamber. Attention is drawn to the determination of the stoichiometric mixture, as well as to the lambda coefficient (λ), which helps to determine the type of mixture. The properties of gasoline (in the form of iso-octane) and ethanol are described in separate sections and each is compared. One chapter is devoted to the description of the E85 mixture used in Flexi Fuel Vehicles engines, the requirements for this fuel are determined by the Minister of Economy on the requirements for the quality of biofuels, and attention is also paid to the effect of the mixture on the operation of the engine and the content of chemical compounds in the exhaust using E85 biofuel. It has been established that ethanol fuel (in particular E100) is undoubtedly a step forward in terms of ecology, transport economics and the development of alternative fuels. However, its physicochemical properties cause many problems in engine operation. Despite the improvement in the net power generated by the engine, it should be remembered that for the current mechanical parts and their materials, this is a “problem” mixture that requires frequent and accurate diagnostics and calibration. KEY WORDS: STOICHIOMETRIC MIXTURE, COMBUSTION, MIXTURE OF GASOLINE AND ETHANOL, ALTERNATIVE FUEL, IMPROVEMENT OF THE PHYSICAL AND CHEMICAL PROCESSES OF THE ENGINE.

Evaluation of linear losses in ventilation ducts with a rounded rectangle cross-section

The paper presents a new ventilation system characterized by the cross-section of the channels in the shape of a rounded rectangle. The basic research problem was the determination of local losses in the system components. To achieve this goal, it is necessary to know the linear losses in the ducts. The principle of determining both types of losses was presented. The friction coefficients of linear pressure losses referred to the unit of the straight length of the duct section ζl[m−1] as well as generalized dimensionless friction coefficient of linear pressure losses λ [-] is presented. The main achievement of the paper is the statement that the lambda coefficient λ can replace the coefficients ζl examined duct cross-sections.

Human Capital Spillovers and Human Development Index in Yogyakarta Special Region and Central Java

This study analyzes the spillover of human capital in the Yogyakarta Special Region and Central Java. The research data includes the Human Development Index (HDI), capital, the ratio of college graduate workers, and the number of medical personnel in 2017 published by the Central Bureau of Statistics (BPS). This study uses a Spatial Regression analysis that includes elements of human capital spillover estimated by Geoda software. The results showed that there was a spillover of human capital between regencies/cities in Yogyakarta Special Region and Central Java. Lambda coefficient value, in Spatial Error Model (SEM), amounting to 0.5074 indicates that the Human Development Index (HDI) score of each regency/city will get an influence of 0.5074 multiplied by the HDI value of the neighboring regency/city. The capital variable is significant and exhibits that a rise in the HDI score will follow an increase in the number of capital. However, the ratio of college-educated worker and medical personnel is not significant. Due to the linkages between these provinces, the regency government and the provincial government should synergize each other, especially in the formulation of economic policies.

Investigation of the Exhaust Gas Emissions from Light Vehicles in the Technical Examination Centers in 2016 (Case Study: Hamadan City)

Background: Expanding urbanization and increasing the number of vehicles have led to adverse effects on both the environment and human health. The propose of this study is to evaluate the concentration of CO2, CO, HC, O2, NOX in the exhaust outlet of vehicles tested in technical examination center, and to determine the relationships between their variation and lambda coefficient, type of fuel injection system as well as vehicle type. Methods: This cross-sectional study was conducted on 1000 vehicles tested in technical examination centers in Hamadan city. To do this, the concentrations of CO2, CO, HC, O2, NOX gases emission were obtained, and then the relations between variation of these gases and lambda coefficient, type of fuel injection system and vehicle type were investigated. The statistical analysis that used in this study include one-way ANOVA and independent t-test (SPSS 16). Results: The results of this study showed a significant relationship between the concentration of emitted gases and the lambda coefficient, the vehicle type and the type of fuel injection system (p<0.05). The lambda coefficient equal to 1 was recognized as the best combustion condition because the availability of sufficient oxygen for the reactions lead to reduction of CO and HC emissions. The fuel injection system had a significant effect on reducing the emissions due to the suitable distribution of fuel and increasing combustion efficiency. Conclusion: In the current study, it was observed that personal vehicles due to lower depreciations than the taxis, and the injector systems due to better distribution of the fuel than the carburetor ones, have better conditions in term of pollutants emissions.nn

Evaluating the Factor Structure of the Persian Version of Posttraumatic Growth Inventory in Cancer Patients

PurposeThis study aimed to assess the factor structure of the Persian version of posttraumatic growth inventory (P-PTGI). MethodsParticipants included 272 Iranian people of Azari ethnicity (111 women and 161 men), aged between 21 and 91 years (mean 52.65 years), who were diagnosed with cancer and were referred to the oncology department of the university hospital. The P-PTGI was assessed to determine the construct validity, using various indices of confirmatory factor analysis and standardized lambda coefficient, followed by further assessment of the discriminant and convergent validities by using the structural equation model. LISREL 8.8 for Windows and SPSS were used for data analysis. ResultsThe calculated values of comparative fit index, incremental fit index, normed fit index, and non-normed fit index > .90 and the values of standardized root-mean-square residual < .08 indicate an acceptable fit for the original PTGI. Considering that the values of average variance extracted (.52–.74) were greater than the square of correlation coefficients between the five dimensions of P-PTGI, discriminant validity was approved. Convergent validity was confirmed through a high value of standardized lambda coefficient (.52–.92) between the items and their related factors. ConclusionsThis study revealed that P-PTGI has an acceptable validity and reliability for posttraumatic growth assessment in Iranian cancer patients and its factor structure is similar to that of the original form developed by Tedeschi and Calhoun.

Measuring association between nominal categorical variables: an alternative to the Goodman–Kruskal lambda

ABSTRACTAs a measure of association between two nominal categorical variables, the lambda coefficient or Goodman–Kruskal's lambda has become a most popular measure. Its popularity is primarily due to its simple and meaningful definition and interpretation in terms of the proportional reduction in error when predicting a random observation's category for one variable given (versus not knowing) its category for the other variable. It is an asymmetric measure, although a symmetric version is available. The lambda coefficient does, however, have a widely recognized limitation: it can equal zero even when there is no independence between the variables and when all other measures take on positive values. In order to mitigate this problem, an alternative lambda coefficient is introduced in this paper as a slight modification of the Goodman–Kruskal lambda. The properties of the new measure are discussed and a symmetric form is introduced. A statistical inference procedure is developed and a numerical example is provided.

DEMYSTIFY ELDERLY: MATERIAL, INSTRUMENTAL, EMOTIONAL AND COGNITIVE ASSISTANT IN AGING

Aging perception seems to be related with dependence, illness, disability and loss of capacity for help others. This perception and the notable increased longevity population implies social and family dynamics that need to be elucidate. Even with aging involves changes like higher prevalence of chronic and degenerative diseases that may affect the independence of elderly population, it appears incoherent to related longevity with disability and dependence. In order to analyze the kinds of help or assistant (material, instrumental, emotional and cognitive) that give and receive elderly people, we recruit data from 2000 in Bogota (Colombia) citizens, taken from Encuesta Salud Bienestar y Envejecimiento SABE. Statistical analyzes were carried out. Lambda coefficient (symmetric) indicate an absence relationship between the different types of help and age, gender, schooling and social status; demonstrating that social concepts about the growing need of aid are wrong.

Rigid Polyurethane Foam Fabrication Using Medium Chain Glycerides of Coconut Oil and Plastics from End-of-Life Vehicles

Polycarbonate and polyurethane scraps from end-of-life vehicles were converted into liquid recycled polyols with hydroxyl number around 300 mgKOH·g–1 by using medium chain glycerides of coconut oil. The obtained polyols were used for preparation of low-density rigid polyurethane foams. It was found that up to 50 wt % of the virgin petrochemical polyol can be replaced by the recycled polyols without any negative effect on the foaming process. The obtained foams exhibited the apparent density of 40–44 kg·m–3, the homogeneous cellular structure with a high content of closed cells (>91 vol %) and the beneficially low value of lambda coefficient (∼23 mW·m–1·K–1). The exceptionally high compressive strength (>350 kPa in parallel to foam rise direction) of the rigid PUR foams with 50 wt % of recycled polyol derived from polycarbonate scrap resulted probably from the unique structure of recycled polyol combining rigid aromatic segments together with flexible coconut oil glyceride units. In conclusion, this approa...

한반도 하록 참나무류의 분포 특이성

The Korean peninsula belongs to the temperate forest biome dominated by many deciduous oaks. We quantitatively and qualitatively studied vertical and horizontal distributions and habitat characteristics on the major oak species such as Quercus mongolica, Q. serrata, Q. variabilis, Q. dentata, Q. aliena and Q. acutissima. A total of 5,278 samples were analyzed with a species coverage and 6 principal environmental variables extracted from public database of nationwide natural environment survey. Correlation analysis was accomplished by the CANOCO using Canonical Correspondence Analysis and the Pearson correlation coefficient using PASW Statistics. The hierarchical distribution tendency of six oaks was finalized using the Goodman-Kruskal lambda coefficient of non-metric multidimensional scaling by SYN-TAX 2000. The utmost factor on the distributional segregation of oak species was the elevation, i.e. temperature. Q. serrata and Q. mongolica show clearly a diametrical distribution patterns with zonal distribution. Q. variabilis was determined as a thermophilic and xerophilous species that is a component of not only natural pseudo-climax forest but also secondary forest. The highest frequency of the dominant forest was found Q. mongolica. Whereas, Q. serrata showed the highest frequency of individual tree but the relatively lower frequency of dominant forest, which is resulted from the original habitat loss. By the benefit of the traditional Soopjeong-E, Q. acutissima dominant forests were remained rather largely. Individuals of Q. dentata occurred horizontally nationwide, but its dominant forest was the poorest. Dominant forest of Q. aliena, which is a natural vegetation, was the most rare due to a limited potential habitat.

The impact of habitat fragmentation on tsetse abundance on the plateau of eastern Zambia

Tsetse-transmitted human or livestock trypanosomiasis is one of the major constraints to rural development in sub-Saharan Africa. The epidemiology of the disease is determined largely by tsetse fly density. A major factor, contributing to tsetse population density is the availability of suitable habitat. In large parts of Africa, encroachment of people and their livestock resulted in a destruction and fragmentation of such suitable habitat. To determine the effect of habitat change on tsetse density a study was initiated in a tsetse-infested zone of eastern Zambia. The study area represents a gradient of habitat change, starting from a zone with high levels of habitat destruction and ending in an area where livestock and people are almost absent. To determine the distribution and density of the fly, tsetse surveys were conducted throughout the study area in the dry and in the rainy season. Landsat ETM+ imagery covering the study area were classified into four land cover classes (munga, miombo, agriculture and settlements) and two auxiliary spectral classes (clouds and shadow) using a Gaussian Maximum Likelihood Classifier. The classes were regrouped into natural vegetation and agricultural zone. The binary images were overlaid with hexagons to obtain the spatial spectrum of spatial pattern. Hexagonal coverage was selected because of its compact and regular form. To identify scale-specific spatial patterns and associated entomological phenomena, the size of the hexagonal coverage was varied (250 and 500m). Per coverage, total class area, mean patch size, number of patches and patch size standard deviation were used as fragmentation indices. Based on the fragmentation index values, the study zone was classified using a Partitioning Around Mediods (PAM) method. The number of classes was determined using the Wilks’ lambda coefficient. To determine the impact of habitat fragmentation on tsetse abundance, the correlation between the fragmentation indices and the index of apparent density of the flies was determined and habitat changes most affecting tsetse abundance was identified. From this it followed that there is a clear relationship between habitat fragmentation and the abundance of tsetse flies. Heavily fragmented areas have lower numbers of tsetse flies, but when the fragmentation of natural vegetation decreases, the number of tsetse flies increases following a sigmoidal-like curve.

Intrarater Reliability in the Ultrasound Diagnosis of Medial and Lateral Orbital Wall Fractures With a Curved Array Transducer

The aims of the study were to document the effectiveness of ultrasound (US) in diagnosing orbital wall fractures when compared with computed tomography (CT) and to measure the intraobserver reliability of US using a curved array transducer. From December 2003 to March 2004, 13 patients with the clinical diagnosis of an orbital trauma were investigated prospectively by CT (reference) and 2 US investigators. Both orbits were investigated. Sensitivity, specificity, accuracy, and positive and negative predictive value were calculated. The statistical difference between the 2 US investigators was calculated by a chi-square test. The interrater reliability was calculated using the lambda coefficient. Values below 0.4 represent poor reliability, between 0.4 and 0.75 represent fair to good reliability, and a score > 0.75 is graded as excellent reliability. The comparison of the results of the 2 US investigators by the chi-square test showed P values of .385 for the medial orbital wall and .638 for the lateral orbital wall, which shows no significant difference. The lambda-value for the investigation of the medial orbital wall reached 0.429, 0.714, and 0.750. The lambda-value for the investigation of the lateral orbital wall yielded 0.647, 0.750, and 0.882. These values show a good and excellent inter-rater reliability. The US investigation does not yet reach the diagnostic quality of CT. US could be a helpful diagnostic imaging tool in cases with clear clinical symptoms. The results of the current study and the previously published results imply that US has the potential to reach the same diagnostic quality as CT in the future, but further studies must be performed to improve the diagnostic quality of the method.