Income and distance elasticities of values of travel time savings: New Swiss results

This paper presents the findings of a study looking into the valuation of travel time savings (VTTS) in Switzerland, across modes as well as across purpose groups. The study makes several departures from the usual practice in VTTS studies, with the main one being a direct representation of the income and distance elasticity of the VTTS measures. Here, important gains in model performance and significantly different results are obtained through this approach. Additionally, the analysis shows that the estimation of robust coefficients for congested car travel time is hampered by the low share of congested time in the overall travel time, and the use of an additional rate-of-congestion coefficient, in addition to a generic car travel time coefficient, is preferable. Finally, the analysis demonstrates that the population mean of the indicators calculated is quite different from the sample means and presents methods to calculate those, along with the associated variances. These variances are of great interest as they allow the generation of confidence intervals, which can be extremely useful in cost-benefit analyses

Investigation of Photoplethysmography and Near Infrared Spectroscopy for the Assessment of Tissue Blood Perfusion

Pulse Oximetry (PO) and Near Infrared Spectroscopy (NIRS) are among the most widely adopted optical techniques for the assessment of tissue perfusion. PO estimates arterial oxygen saturation (SpO2) by exploiting light attenuations due to pulsatile arterial blood (AC) and constant absorbers (DC) at two different wavelengths. NIRS processes the attenuations of at least two wavelengths to calculate concentrations of Deoxygenated ([HHb]), Oxygenated ([HbO2]), Total Haemoglobin ([tHb]) and Tissue Oxygenation Index (TOI). In this work we present the development and evaluation of a reflectance PPG probe and processing system for the assessment of tissue perfusion. The system adopts both Pulse Oximetry and NIRS principles to calculate SpO2, [HHb], and [HbO2] and [tHb]. The system has been evaluated on the forearm of 10 healthy volunteers during cuff-induced vascular occlusions. The presented system was able to estimate SpO2, [HHb], [HbO2] and [tHb], showing good agreement with state-of-the-art NIRS and conventional PO

Accuracy of reflectance photoplethysmography on detecting cuff-induced vascular occlusions

Photoplethysmography (PPG) is a noninvasive optical technique, which can also be used to derive important parameters other than arterial oxygen saturation (SpO2). In this work, the accuracy of the technique on detecting changes in blood perfusion during different levels of vascular occlusions has been explored. A dual-wavelength, reflectance PPG probe was applied on the left forearm of 10 healthy volunteers and raw PPG signals were acquired by a research PPG processing system. The raw PPG signals were separated into pulsatile AC and continuous DC PPG components. The signals were used to estimate SpO2 and changes in concentration of oxygenated, deoxygenated, and total haemoglobin. Different levels of occlusions, from 20 mmHg to total occlusion were induced by a pressure-cuff on the left arm. The system was able to indicate all the occlusions. In particular, the haemoglobin concentration changes estimated from PPG were in high agreement with Near Infrared Spectroscopy measurements

Reflectance Photoplethysmography as Non-Invasive Monitoring of Tissue Blood Perfusion.

In the last decades Photoplethysmography (PPG) has been used as noninvasive technique for monitoring arterial oxygen saturation by Pulse Oximetry (PO), whereas Near Infrared Spectroscopy (NIRS) has been employed for monitoring tissue blood perfusion. While NIRS offers more parameters to evaluate oxygen delivery and consumption in deep tissues, PO only assesses the state of oxygen delivery. For a broader assessment of blood perfusion, this paper explores the utilization of dual-wavelength PPG by using the pulsatile (AC) and continuous (DC) PPG for the estimation of arterial oxygen saturation (SpO2) by conventional PO. Additionally, the Beer-Lambert law is applied to the DC components only for the estimation of changes in deoxy-hemoglobin (HHb), oxy-hemoglobin (HbO2) and total hemoglobin (tHb) as in NIRS. The system was evaluated on the forearm of 21 healthy volunteers during induction of venous occlusion (VO) and total occlusion (TO). A reflectance PPG probe and NIRS sensor were applied above the brachioradialis, PO sensors were applied on the fingers, and all the signals were acquired simultaneously. While NIRS and forearm SpO2 indicated VO, SpO2 from the finger did not exhibit any significant drop from baseline. During TO all the indexes indicated the change in blood perfusion. HHb, HbO2 and tHb changes estimated by PPG presented high correlation with the same parameters obtained by NIRS during VO (r2=0.960, r2=0.821 and r2 =0.974 respectively) and during TO (r2=0.988, r2=0.940 and r2=0.938 respectively). The system demonstrated the ability to extract valuable information from PPG signals for a broader assessment of tissue blood perfusion

Measuring on Farm Diversity and Determinants of Barley Diversity in Tigray, Northern Ethiopia

Maintaining on-farm diversity of crop varieties has received increasing attention as a strategy for mitigating production risk and protecting food security in resource-poor farming systems with few opportunities for insurance or trade. Barley is grown under a wide range of environmental conditions and in marginal areas or seasons where the production of other cereals is limited. Food consumption preferences and variable tolerance to biotic and abiotic stresses influence the mixture and number of varieties to be grown. Phenotypic diversity was determined using Shannon diversity index. An econometric approach has been applied to identify the social and economic factors that influence levels of diversity maintained on-farm. A high phenotypic diversity index (0.79) was recorded from sampled barley varieties. Censored regression indicates that physical characteristics of the farm (land fragmentation index, farm size), agro climatic features of the site (altitude, rainfall, temperature) and household characteristics (only number of children) had a significant and positive impact on diversity and area allocation of barley. The significant negative relation of number of extension contact with barley diversity implies further attention and analysis. Key words: On farm diversity, Determinants of diversity, On farm conservation, Diversity inde

Perfusion Changes at the Forehead Measured by Photoplethysmography during a Head-Down Tilt Protocol

Photoplethysmography (PPG) signals from the forehead can be used in pulse oximetry as they are less affected by vasoconstriction compared to fingers. However, the increase in venous blood caused by the positioning of the patient can deteriorate the signals and cause erroneous estimations of the arterial oxygen saturation. To date, there is no method to measure this venous presence under the PPG sensor. This study investigates the feasibility of using PPG signals from the forehead in an effort to estimate relative changes in haemoglobin concentrations that could reveal these posture-induced changes. Two identical reflectance PPG sensors were placed on two different positions on the forehead (above the eyebrow and on top of a large vein) in 16 healthy volunteers during a head-down tilt protocol. Relative changes in oxygenated (∆HbO2), reduced (∆HHb) and total (∆tHb) haemoglobin were estimated from the PPG signals and the trends were compared with reference Near Infrared Spectroscopy (NIRS) measurements. Also, the signals from the two PPG sensors were analysed in order to reveal any difference due to the positioning of the sensor. ∆HbO2, ∆HHb and ∆tHb estimated from the forehead PPGs trended well with the same parameters from the reference NIRS. However, placing the sensor over a large vasculature reduces trending against NIRS, introduces biases as well as increases the variability of the changes in ∆HHb. Forehead PPG signals can be used to measure perfusion changes to reveal venous pooling induced by the positioning of the subject. Placing the sensor above the eyebrow and away from large vasculature avoids biases and large variability in the measurements

Investigation of photoplethysmography, laser doppler flowmetry and near infrared spectroscopy during induced thermal stress

Continuous assessment of blood flow, blood volume, and blood and tissue oxygenation are of vital importance in critically ill patients. Photoplethysmography (PPG), Pulse Oximetry (PO), Laser Doppler Flowmetry (LDF) and Near Infrared Spectroscopy (NIRS) are amongst the most widely used techniques to monitor such perfusion parameters. In this study, we investigated the feasibility of using dual-wavelength PPG signals on providing comparable information as LDF and NIRS, besides arterial oxygen saturation (SpO2) as measured by pulse oximetry. All three techniques were investigated on six healthy volunteers during whole-body cold exposure. PPG and LDF sensors were attached on the finger and hand respectively, while NIRS was positioned above the left forearm. Measurements at room temperature (24°C) were followed and preceded by a cold exposure (10°C). The results showed that changes in pulsatile PPG amplitudes and hemoglobin concentration estimated from finger PPG signals indicate strong similarities with gold-standard LDF and NIRS measurements

Market chain analysis of red pepper: The case of Bure Woreda, West Gojjam Zone, Amhara National Regional State, Ethiopia

In Bure, West Gojjam zone, Amhara region red pepper is a major cash crop which is mainly produced by smallholder farmers. The basic objective of this study was to analyze profitability of red pepper production, determinants of household’s marketable surplus and the degree of market integration in major regional intermediate markets using primary data collected from households through semi structured questionnaire. The producers’ survey result revealed that all farmers supply the product to the market and 85.3% of red pepper produced by the sampled farmers in the production year was supplied to the market. Farmers in the Woreda do not have any standard measure to identify the quality of pepper. They usually identify quality of red pepper by its color, pest damage, size, shape, odor and foreign matter. In the Woreda, the four largest traders handled 30.2% of the total volume of purchased pepper. Hence the structure of the pepper market in the study area was some what competitive. The profitability analysis also indicates that red pepper production was profitable. The average amount of red pepper supplied to the market by producers was 5.24 quintal with minimum amount of 0.5 quintals and maximum of 19 quintals. The variables that influenced the marketable supply positively were agricultural experience, access to credit, yield, land size, current year and lagged prices. Among the significant variables yield and access to credit were highly significant at less than 1% significant level. The result of market integration analysis also shows that pepper markets in the western part of the region were integrated. The major problems identified are low access to improved inputs, collateral problem to get credit, poor storage facilities and low price of produce. To solve these problems increased access to improved inputs, strengthening credit institutions, strengthening of cooperatives, education and training, price information and establishment of storage and processing facilities are recommended