Introduction to total- and partial-pressure measurements in vacuum systems

An introduction to the fundamentals of total and partial pressure measurement in the vacuum regime (760 x 10 to the -16th power Torr) is presented. The instrument most often used in scientific fields requiring vacuum measurement are discussed with special emphasis on ionization type gauges and quadrupole mass spectrometers. Some attention is also given to potential errors in measurement as well as calibration techniques

The importance of a device specific calibration for smartphone colorimetry

In order for a smartphone-based colorimetry system to be generalizable, it must be possible to account for results from multiple phones. A move from device-specific space to a device independent space such as XYZ space allows results to be compared, and means that the link between XYZ values and the physical parameter of interest needs only be determined once. We compare mapping approaches based on calibration data provided in image metadata, including the widely used open-source software dcraw, to a separate calibration carried out using a colorcard. The current version of dcraw is found to behave suboptimally with smartphones and should be used with care for mapping to XYZ. Other metadata approaches perform better, however the colorcard approach provides the best results. Several phones of the same model are compared and using an xy distance metric it is found that a device-specific calibration is required to maintain the desired precision

Minimising ambient illumination via ambient subtraction: Smartphone assessment of jaundice in liver patients via sclera images

Using smartphone images to quantify color presents a noninvasive way to assess jaundice and other color-related biomarkers of the human body. Here we focus on assessing jaundice through accurate bilirubin measurement in adult liver patients, the first time optical imaging has been applied to this cohort. These patients can suffer from very high levels of bilirubin, indicating their severity of liver disease. A smartphone assessment technique for jaundice based around the color of the sclera (white of the eye) extracted from images is being developed, as smartphone imaging enables cheap, non-invasive and quantitative readings. Variations in ambient light cause large changes to recorded pixel values so must be accounted for to ensure that any changes detected are due to changes in jaundice level. Here we suggest the use of an ambient subtraction approach to minimise the effects of ambient light. Pairs of flash/no-flash images are captured and the extracted values subtracted to yield data as though under a pure flash illumination. We present data demonstrating the technique with a group of healthy adult volunteers. We also present data from a patient study involving adults with liver disease. Images were captured and the bilirubin (jaundice) level predicted from these images before and after subtraction was compared to the ground truth value obtained via blood test. The linear correlation coefficient increased from 0.47 to 0.85 (p<0.001 in both cases) upon application of subtraction, demonstrating the effectiveness of the technique

Smartphone screening for neonatal jaundice via ambient-subtracted sclera chromaticity

Jaundice is a major cause of mortality and morbidity in the newborn. Globally, early identification and home monitoring are significant challenges in reducing the incidence of jaundice-related neurological damage. Smartphone cameras are promising as colour-based screening tools as they are low-cost, objective and ubiquitous. We propose a novel smartphone method to screen for neonatal jaundice by imaging the sclera. It does not rely on colour calibration cards or accessories, which may facilitate its adoption at scale and in less economically developed regions. Our approach is to explicitly address three confounding factors in relating colour to jaundice: (1) skin pigmentation, (2) ambient light, and (3) camera spectral response. (1) The variation in skin pigmentation is avoided by imaging the sclera. (2) With the smartphone screen acting as an illuminating flash, a flash/ no-flash image pair is captured using the front-facing camera. The contribution of ambient light is subtracted. (3) In principle, this permits a device- and ambient-independent measure of sclera chromaticity following a one-time calibration. We introduce the concept of Scleral-Conjunctival Bilirubin (SCB), in analogy with Transcutaneous Bilirubin (TcB). The scleral chromaticity is mapped to an SCB value. A pilot study was conducted in the UCL Hospital Neonatal Care Unit (n = 37). Neonates were imaged using a specially developed app concurrently with having a blood test for total serum bilirubin (TSB). The better of two models for SCB based on ambient-subtracted sclera chromaticity achieved r = 0.75 (p250μmol/L (area under receiver operating characteristic curve, AUROC, 0.86), and 92% (specificity 67%) in identifying newborns with TSB>205μmol/L (AUROC 0.85). These results are comparable to modern transcutaneous bilirubinometers

Smartphone colorimetry using ambient subtraction: Application to neonatal jaundice screening in Ghana

A smartphone app to screen for neonatal jaundice has a large potential impact in reducing neonatal death and disability. Our app, neoSCB, uses a colour measurement of the sclera to make a screening decision. Although there are numerous benefits of a smartphone-based approach, smartphone colour measurement that is accurate and repeatable is a challenge. Using data from a clinical setting in Ghana, we compare sclera colour measurement using an ambient subtraction method to sclera colour measurement using a standard colour card method, and find they are comparable provided the subtracted signal-to-noise ratio (SSNR) is sufficient. Calculating a screening decision metric via the colour card method gave 100% sensitivity and 69% specificity (n=87), while applying the ambient subtraction method gave 100% sensitivity and 78% specificity (SSNR>3.5; n=50)

Feasibility of smartphone colorimetry of the face as an anaemia screening tool for infants and young children in Ghana

Background Anaemia affects approximately a quarter of the global population. When anaemia occurs during childhood, it can increase susceptibility to infectious diseases and impair cognitive development. This research uses smartphone-based colorimetry to develop a non-invasive technique for screening for anaemia in a previously understudied population of infants and young children in Ghana. Methods We propose a colorimetric algorithm for screening for anaemia which uses a novel combination of three regions of interest: the lower eyelid (palpebral conjunctiva), the sclera, and the mucosal membrane adjacent to the lower lip. These regions are chosen to have minimal skin pigmentation occluding the blood chromaticity. As part of the algorithm development, different methods were compared for (1) accounting for varying ambient lighting, and (2) choosing a chromaticity metric for each region of interest. In comparison to some prior work, no specialist hardware (such as a colour reference card) is required for image acquisition. Results Sixty-two patients under 4 years of age were recruited as a convenience clinical sample in Korle Bu Teaching Hospital, Ghana. Forty-three of these had quality images for all regions of interest. Using a naïve Bayes classifier, this method was capable of screening for anaemia (<11.0g/dL haemoglobin concentration) vs healthy blood haemoglobin concentration (≥11.0g/dL) with a sensitivity of 92.9% (95% CI 66.1% to 99.8%), a specificity of 89.7% (72.7% to 97.8%) when acting on unseen data, using only an affordable smartphone and no additional hardware. Conclusion These results add to the body of evidence suggesting that smartphone colorimetry is likely to be a useful tool for making anaemia screening more widely available. However, there remains no consensus on the optimal method for image preprocessing or feature extraction, especially across diverse patient populations

Screening for neonatal jaundice with a smartphone

A method to screen for jaundice in neonates using a digital image of the sclera is proposed. The RGB pixel values from a raw format image are used to derive an estimate for the total serum bilirubin (TSB). A study at UCH Neonatal Unit found a correlation of r=0.71 (p<0.01) between measured TSB and TSB estimated by this method. The advantages of using a smartphone camera as a mobile screening device are discussed

Jaundice Eye Color Index (JECI): quantifying the yellowness of the sclera in jaundiced neonates with digital photography

The sclera is arguably a better site than the skin to measure jaundice&#x2013;especially in dark-skinned patients&#x2013;since it is free of skin pigment (melanin), a major confounding factor. This work aims to show how the yellowness of the sclera can be quantified by digital photography in color spaces including the native RGB and CIE XYZ. We also introduce a new color metric we call &#x201C;Jaundice Eye Color Index&#x201D; (JECI) which allows the yellowness of jaundiced sclerae to be predicted for a specific total serum bilirubin level in the neonatal population

Representative Farms Economic Outlook for the January 2001 FAPRI/AFPC Baseline

The farm level economic impacts of projected long term prices under the Federal Agriculture Improvement and Reform Act of 1996 (FAIR) on representative crop and livestock operations are projected in this report. For this report the FAIR Act will be referred to as the 1996 Farm Bill. The analysis was conducted over the 1996-2005 planning horizon using FLIPSIM, AFPC’s whole farm simulation model. Data to simulate farming operations in the nation’s major production regions came from two sources: - Producer panel cooperation to develop economic information to describe and simulate representative crop, livestock, and dairy farms. - Projected prices, policy variables, and input inflation rates from the Food and Agricultural Policy Research Institute (FAPRI) January 2001 Baseline. The primary objective of the analysis is to determine the farms’ economic viability by region and commodity throughout the life of the 1996 Farm Bill and beyond.Agribusiness, Agricultural and Food Policy, Crop Production/Industries,

SE 03. Financial projections for the evaluation of technological alternatives in the Mexican dual purpose production system

The overall objective of this work was to perform an economic analysis of technological alternatives for the dual purpose production systems under Mexico’s tropical conditions. This production unit was based on grazing 100 ha of improved species of grass and supplemented with Napier grass and corn silage during the dry season. Two alternative scenarios were analyzed: 1) the use of BST and 2) the purchase of a milk cooling tank. A farm level, income and policy simulation model (FLIPSIM), developed at Texas A&amp;M University was used to analyze the production and financial conditions of the production unit over a six year planning horizon (1995-2000). The results indicate that to pay for the use of BST, on average, the milking herd should increase milk production by 21.38 % for the first year in the planning horizon. As inflation decreases and financial conditions improve over time, smaller increments in milk production would be necessary to pay for the hormone. The initial investment necessary for the purchase and associated facilities for a milk cooling tank and operation costs associated to cooling the milk required the net income to increase to US$12,500 over the baseline during the first year for the farm to break-even. The more dramatic effect is realized in the first year because of the 20$ 4,000 to US$5,700 over the rest of the planning horizon. The effect of this on the unitary BE milk price is a difference of US$ 0.046 /liter of milk in the first year and a range of US$ 0.015 - 0.0213 /liter of milk over the rest of the planning horizon