车辆导航定位系统GPS接收机的原理与研制

分析了OEM板和GPS技术原理，介绍了基于OEM板的GPS接收机开发方法，重点阐述了车辆导航定位系统GPS接收机的软、硬件体系结构及研制过程，详细说明了单片机C语言串行通讯原理与程序编制。     

苹果糖度在线检测降低杂散光影响研究

基于光谱学原理设计了智能苹果糖度在线分级设备,研究了上置式检测器在线检测中的杂散光问题,通过光路图分析了富士苹果3种摆放方式对杂散光的影响,并提出了遮光降噪方案。利用偏最小二乘(PLS)回归分别建立了3种摆放方式的富士苹果可溶性固形物含量(SSC)在线预测模型。研究结果表明,对于上置式检测器而言,摆放方式和遮光处理尤为重要。其中果柄朝上遮光为最佳降噪措施,所建立的模型校正集均方差(RMSEC)为0.60,校正集相关系数(RC)为0.94,预测集均方差(RMSEP)为0.67,预测集相关系数(RP)为0.87,可以满足实际生产中的在线分级要求。     

Comparative diagnostic test characteristics of oscillometric and Doppler ultrasonographic methods in the detection of systolic hypertension in dogs

Comparison of test characteristics allows a clinician to choose the optimal diagnostic test method for an individual patient. This study assessed the comparative test characteristics of noninvasive (NI) blood pressure measurement methods (oscillometric and Doppler) and used this information to develop optimal cutoff values for diagnosis of systolic hypertension in dogs by these NI methods. Simultaneous NI (oscillometric or Doppler methods) and invasive (arterial puncture [AP]) systolic blood pressure (SBP) measurements were obtained prospectively from normal dogs and dogs suspected of having systemic hypertension based on clinical signs. Oscillometric SBP readings were obtained from the distal hind limb (Osc-L, n = 54) or the proximal tail (T. n = 27). Doppler BP measurements were obtained using a forelimb cuff (n = 57). AP-SBP was categorized as hypertensive if > or = 160 mmHg, and sensitivity (Se). specificity (Sp), and likelihood ratios (LR) were calculated for diagnostic cutoff values ranging from 130 to 220 mmHg. Receiver operator characteristic (ROC) curves were analyzed to determine optimal cutoff values for diagnosis of AP-SBP > or = 160 mmHg. Optimal NI SBP cutoff values considered to reflect AP values > or = 160 mmHg were: Osc-L = 160 mmHg (Se: 65%, Sp: 85%. LR = 4.33: 1), Osc-T = 150 mmHg (Se: 84%, Sp: 75%, LR = 3.36: 1), and Doppler = 160 mmHg (Se: 71%,     

Accuracy of serum beta-hydroxybutyrate measurements for the diagnosis of diabetic ketoacidosis in 116 dogs

The aim of this study was to evaluate the accuracy of serum beta-hydroxybutyrate (beta-OHB) measurements for the diagnosis of diabetic ketoacidosis (DKA) in dogs. One hundred sixteen diabetic dogs were prospectively enrolled in the study: 18 insulin-treated (IT) diabetic dogs that had a positive urine ketone test and 88 untreated, newly diagnosed diabetic dogs. Venous blood gas tensions and pH, serum glucose and urea nitrogen (SUN), and electrolyte (Na+, Cl-, and K+) and urine acetoacetate (AA) concentrations were measured concurrently with serum beta-OHB concentrations. On the basis of laboratory findings, the patients were assigned to I of 3 groups: diabetic ketoacidosis (n = 43); diabetic ketosis (DK, n = 41); and nonketotic diabetes (NDK, n = 31). Serum beta-OHB concentrations differed significantly (P < .001) among the study groups. Although marked differences in beta-OHB concentrations were found, a considerable overlap exists between the distributions of dogs with DK and those with DKA. The overall accuracy of beta-OHB determination as a diagnostic test for DKA, determined by the area under the receiver operating characteristic (ROC) curve, was 0.92. In the 1.9- to 4.8-mmol/L range, serum beta-OHB determination sensitivity varied from 100 to 35.7%, whereas specificity varied from 39 to 100%. The cutoff value of 3.8 mmol/L showed the best equilibrium between specificity (95%), sensitivity (72%), and likelihood ratio (14.8). We concluded that the quantitative measurement of serum beta-OHB may be a potential tool for diagnosing and monitoring ketosis and ketoacidosis in diabetic dogs.     

Measuring trail users’ perception of crowding in a peri-urban nature park: A best-worst scaling experiment

This paper evaluates the perception of crowding, its determinants and relationship with trail users’ experience in a peri-urban nature park. Existing crowding surveys rely heavily on a single-item 9-point crowding scale which was originally developed for backcountry areas. Receiver operating characteristic (ROC) analysis was used to test the validity and reliability of this measure in detecting crowding issues and formulating visitor capacity limits. Low validity and reliability raised concerns about the applicability of this scale in similar frontcountry areas. Inability of this simple crowding measure to detect a visitor threshold brings to the fore its another important limitation – ignorance of the complexity of crowding phenomenon. The perception of crowding varies with various social, psychological and situational factors, and a best-worst scaling (BWS) experiment was designed to simultaneously evaluate different aspects of crowding in the Medvednica Nature Park, a peri-urban nature park near Zagreb, Croatia. The findings of BWS experiment revealed that occupancy of mountain huts, number of other hikers on the trail and amount of litter along the trail on average contributed most to the trail users’ sense of crowding. A latent class analysis identified a large heterogeneity in the perception of crowding; while one group of trail users (63%) was more disturbed by the direct social impacts, the others (37%) were more disturbed by the secondary impacts of other visitors, especially by the negative externalities from road traffic in the park. Older visitors had a greater tendency to primarily associate crowding with the environmental conditions. A higher impact of trail use level in the perception of crowding, younger age and more frequent use were associated with a more negative evaluation of crowding. The park management should closely monitor road traffic in the park and visitor activity on highly used trails, especially on those popular among younger trail users.     

Validity of the Enzyme-linked Immunoelectrotransfer Blot (EITB) for naturally acquired porcine cysticercosis

The Enzyme-linked Immunoelectrotransfer Blot (EITB) has been used widely as a screening test for Taenia solium cysticercosis in swine. However, the relation between seropositivity and infection in pig populations from endemic areas has not been well defined. The aim of this study is to relate EITB seropositivity with infection and infection burden, analyse the trade-off between sensitivity and specificity with various cut-off points for the EITB assay, and finally describe the serology changes in a cohort of rural pigs raised under natural conditions. A group of 107 pigs that were used as controls during a vaccination field trial in Peru was our study population. The prevalence of porcine cysticercosis determined by necropsy examination was 16.82% (18/107) in these animals. Using EITB reactivity to ≥1 band as a cut-off point for the assay, the sensitivity was 88.89% (65.29–98.62, 95% CI) and the specificity was 48.31% (37.59–59.16, 95% CI). Comparing other cut-off points, involving up to as many as 7 reactive bands, a reactivity of ≥3 bands provided the best trade-offs in sensitivity and specificity. Using this cut-off point for the assay, the sensitivity was 77.77% (52.36–93.59, 95% CI) and the specificity was 76.40% (66.22–84.76, 95% CI). A significant association was found between cyst counts over 100 cysts and reactivity to ≥3 bands in the EITB assay (Fisher's exact test, p < 0.05). The results of this study suggest that the use of the EITB assay to study porcine cysticercosis may require setting different cut-offs under field and experimental conditions, and depending upon the objective of the screening process.     

Predicting species occurrence using information-theoretic approaches and significance testing: An example of dormouse distribution in Cumbria, UK

Predicting the occurrence of species is an essential part of conservation biology. The range of techniques used to do this has increased in recent years. This has included wider use of information-theoretic approaches; particularly Akaike’s information criteria (AIC). AIC is often used with regression modelling when predicting species distribution. The traditional method of model selection in regression modelling, stepwise significance testing, is also still widely used. This paper compares the two approaches, using the occurrence of the dormouse (Muscardinus avellanarius) in Cumbria, UK as an example. The dormouse is a protected species whose abundance and range have declined nationally. Knowledge of its occurrence in Cumbria is required in order to increase measures for its conservation in the area. The paper uses the habitat features woodland size, altitude, soil type, tree species present, temperature and rainfall as potential predictors. As only presence data was available for dormice in Cumbria, pseudo-absences were generated to allow logistic regression modelling. The use of pseudo-absences was justified using a false record permutation test. Cross-validation allowed the ability of models to predict the data to be assessed. This was judged using ROC plots. The size of the wood, temperature and whether the soil was wet or dry were the best predictors of dormouse incidence in Cumbria. The two approaches produced different models; those from the information-theoretic approach had a better ability to fit the data. The information-theoretic approach also had the advantage of enabling model averaging and provided greater understanding of the system.     

Evaluation of Serum Ferritin as a Tumor Marker for Canine Histiocytic Sarcoma

Background: Canine histiocytic sarcoma (HS) is an aggressive malignancy. Hyperferritinemia has been documented in dogs with HS and could serve as a tumor marker aiding in diagnosis and treatment. In people, hyperferritinemia is found in inflammatory diseases, liver disease, and hemolysis, and thus may occur in dogs with these conditions. Objective: To determine if serum ferritin concentration is a tumor marker for canine HS. Animals: Dogs with HS (18), inflammatory diseases (20), liver disease (24), immune‐mediated hemolytic anemia (IMHA) (15), and lymphoma (23). Methods: Prospective, observational, cohort study: Serum ferritin concentration was measured at initial diagnosis. Parametric methods were used to compare mean log ferritin concentrations among disease categories. Receiver‐operating characteristic curves and likelihood ratios were used to evaluate serum ferritin concentration as a tumor marker. Results: Varying proportions of dogs with IMHA (94%), HS (89%), liver disease (79%), lymphoma (65%), and inflammatory diseases (40%) had hyperferritinemia. Dogs with IMHA had significantly higher mean ferritin concentration than dogs in all other categories. Dogs with HS had significantly higher mean ferritin concentration than those in the inflammatory disease and lymphoma categories. Mean serum ferritin concentration was not significantly different between dogs with HS and those with liver disease. Decision thresholds were determined to distinguish IMHA and HS from the other diseases associated with hyperferritinemia. Conclusion: Hyperferritinemia is common in dogs with HS and, after IMHA is ruled out, the degree of hyperferritinemia may be useful in differentiating dogs with HS from dogs with inflammatory diseases, liver disease, and lymphoma.     

A Bayesian approach to assess the accuracy of a diagnostic test based on plant disease measurement

The proportion of diseased plant organs measured before chemical treatment is often used to make an assessment of the need for crop protection in agricultural plots, but such diagnostic tests are not perfect and sometimes lead to incorrect decisions. The area under the receiver operating characteristic (ROC) curve is a popular index of the overall performance of a test. It can be interpreted as the probability that the test value for a randomly chosen diseased subject will exceed that of a randomly chosen disease-free subject. In this paper, we present a Gaussian/Binomial model to assess the accuracy of diagnostic test based on a measured proportion of diseased plant organs. The model parameters were estimated from a real dataset and the model was used to analyse the accuracy of a diagnostic test based on a measured proportion of oilseed rape flowers contaminated by Sclerotinia sclerotiorum. The results showed that the accuracy of the test depends on the number of collected flowers, but that it is not necessary to collect more than 40 flowers per plot. A simulation study showed that the bias of the estimator of the area under the ROC curve was near zero for all size of dataset and that its mean-square error decreased in function of the number of experimental plots used in the ROC analysis. A major interest of our approach is that it allows one to study the effect of the sample size of the organs on the accuracy of the test. It can also be used to estimate the probability of disease occurrence, and to determine a decision threshold according to the sensitivity and specificity values.     

Enzyme-linked immunosorbent assay, single radial immunodiffusion, and indirect methods for the detection of failure of transfer of passive immunity in dairy calves

BACKGROUND: Confirmatory tests for failure of transfer of passive immunity (FTPI) in dairy calves require direct measurements of the serum immunoglobulin G concentration. Enzyme-linked immunosorbent assay (ELISA) has advantages over single radial immunodiffusion (SRID) in terms of cost and time. OBJECTIVES: To evaluate the agreement between ELISA and SRID, and to compare the diagnostic performance of ELISA with indirect methods, in the detection of FTPI in calves. ANIMALS: One hundred and fifteen dairy calves (aged 0-10 days) from 23 calf-rearing facilities. METHODS: Prospective, observational study. The agreement between SRID and ELISA was determined by the Bland-Altman method. Fixed bias (SRID - ELISA) was calculated. For comparison of the diagnostic performance of ELISA with indirect methods, sensitivity, specificity, and area under the curve (AUC) of receiver operating characteristic (ROC) curves were calculated at cut-off values of 500 and 1,000 mg/dL. RESULTS: The agreement between SRID and ELISA was 94%. Fixed bias (SRID - ELISA) was 140 +/- 364 mg/dL. The AUC and sensitivity of ELISA at the cut-off value of 1,000 mg/dL were higher than those of indirect methods (P<.004). The specificity of ELISA at the cut-off value of 1,000 mg/dL was not higher than that of indirect methods, except for serum total protein concentration assay. CONCLUSION AND CLINICAL IMPORTANCE: ELISA exhibited good diagnostic performance and good agreement with SRID. ELISA is an adequate method for both screening and confirmatory tests for FTPI in dairy calves at the cut-off value of 500 mg/dL.