Evaluating the quality of remote sensing products for agricultural index insurance.

Agricultural index insurance contracts increasingly use remote sensing data to estimate losses and determine indemnity payouts. Index insurance contracts inevitably make errors, failing to detect losses that occur and issuing payments when no losses occur. The quality of these contracts and the indices on which they are based, need to be evaluated to assess their fitness as insurance, and to provide a guide to choosing the index that best protects the insured. In the remote sensing literature, indices are often evaluated with generic model evaluation statistics such as R2 or Root Mean Square Error that do not directly consider the effect of errors on the quality of the insurance contract. Economic analysis suggests using measures that capture the impact of insurance on the expected economic well-being of the insured. To bridge the gap between the remote sensing and economic perspectives, we adopt a standard economic measure of expected well-being and transform it into a Relative Insurance Benefit (RIB) metric. RIB expresses the welfare benefits derived from an index insurance contract relative to a hypothetical contract that perfectly measures losses. RIB takes on its maximal value of one when the index contract offers the same economic benefits as the perfect contract. When it achieves none of the benefits of insurance it takes on a value of zero, and becomes negative if the contract leaves the insured worse off than having no insurance. Part of our contribution is to decompose this economic well-being measure into an asymmetric loss function. We also argue that the expected well-being measure we use has advantages over other economic measures for the normative purpose of insurance quality ascertainment. Finally, we illustrate the use of the RIB measure with a case study of potential livestock insurance contracts in Northern Kenya. We compared 24 indices that were made with 4 different statistical models and 3 remote sensing data sources. RIB for these indices ranged from 0.09 to 0.5, and R2 ranged from 0.2 to 0.51. While RIB and R2 were correlated, the model with the highest RIB did not have the highest R2. Our findings suggest that, when designing and evaluating an index insurance program, it is useful to separately consider the quality of a remote sensing-based index with a metric like the RIB instead of a generic goodness-of-fit metric.

Osmoreceptors do not exhibit a sex-dependent modulation of forearm skin blood flow and sweating.

Studies show that increases in plasma osmolality result in a delayed onset threshold of thermoeffector responses. However, it remains unclear if there are sex-related differences in the osmotically induced changes in both sweating and cutaneous vascular conductance (CVC). Nine young men and nine young women were passively heated (water-perfused suit) to 1.5°C above baseline esophageal temperature while in an isosmotic (0.9% NaCl saline infusion) (ISO) and hyperosmotic (3% NaCl saline infusion) (HYP) state. Forearm sweat rate (ventilated capsule), skin blood flow (laser-Doppler), esophageal temperature and skin temperature were continuously recorded. Sweat gland output (SGO) on the forearm was calculated from the number of heat activated sweat glands (modified iodine-paper technique) at the end of heating. The onset threshold and thermosensitivity of sweating and CVC were determined using the linear portion of each response plotted against mean body temperature and analyzed using segmented regression analysis. We show that the osmotically induced delay in the onset threshold of sweating and CVC is similar between males and females. Although the thermosensitivity of CVC was similar between sexes (P = 0.601), the thermosensitivity of sweating was consistently lower in females compared to males (P = 0.018). The lower thermosensitivity in sudomotor response of females was accompanied by a lower SGO (P = 0.003), albeit similar sweat gland activation to males (P = 0.644). We conclude that sex-related differences in thermoeffector activity are independent of osmoreceptor activation. Therefore, osmoreceptors do not exhibit sex-related differences in the modulation of CVC and sweating responses during heat stress.

Is whole-body thermoregulatory function impaired in type 1 diabetes mellitus?

UNLABELLED: During periods of extreme heat individuals with diabetes have greater rates of heat-related morbidity and mortality compared to their non-diabetic counterparts. The reason for this discrepancy is currently unknown. Furthermore, there is a lack of information about whether or not individuals with type 1 diabetes are at a thermoregulatory disadvantage during strenuous physical activity especially when performed in the heat. PURPOSE: This review discusses the current literature pertaining to thermoregulatory responses in individuals with type 1 diabetes. METHODS: We included 14 reviews and 95 original research articles identified by searches of PubMed and Google Scholar and deemed relevant to our subject by three independent readers. RESULTS: Individuals with poorly controlled type 1 diabetes may have impaired heat sensation, and a reduced capacity to dissipate heat due to lower skin blood flow and sweating responses and a greater tendency towards dehydration compared to individuals without diabetes. Impairments may be attenuated or absent in those with good blood glucose control. We found no published studies examining thermoregulatory responses to physical activity in the heat in individuals with type 1 diabetes. CONCLUSIONS: Type 1 diabetes may cause impairments in heat loss resulting in a greater level of thermal strain. Advancement in our understanding about the effects of type 1 diabetes on the heat stress response, especially during different challenges to human heat balance associated with changes in both environmental heat load and metabolic heat production (physical activity), will help us to determine where the risk of heat-illness/injury actually exists.

The constant flow ventricular infusion test: a simple and useful study in the diagnosis of third ventriculostomy failure.

OBJECT: The evaluation of third ventriculostomy function in hydrocephalic patients is challenging. The utility of the constant flow infusion test in predicting response to shunt insertion in normal-pressure hydrocephalus, as well as in identifying shunt malfunction, has been previously demonstrated. The object of this study was to evaluate its usefulness in determining whether a revision CSF diversion procedure was indicated in patients presenting with recurring symptoms and persisting ventriculomegaly after endoscopic third ventriculostomy (ETV). METHODS: The authors conducted a prospective study of all patients who, after undergoing ETV at their institution, presented postoperatively with recurring symptoms and persisting ventriculomegaly. RESULTS: Forty-six patients (mean age 40.7 years, including 11 patients younger than 18 years) underwent 56 constant flow ventricular infusion tests (VITs) at a mean of 24.7 months post-ETV. Thirty-three patients with resistance to CSF outflow (R(out)) less than 13 mm Hg/ml/min underwent follow-up (median 17 months) and experienced resolution of symptoms. In 10 episodes R(out) was greater than 13 mm Hg/ml/min; the patients in these cases underwent revisional CSF diversion. Two patients demonstrated high and frequent B (slow) waves despite a low R(out); these patients also underwent successful revisions. Patients who improved after surgery had increased B wave activity in the plateau phase of the VIT (p = 0.01). Thirty-four patients underwent MR imaging at the same time; 4 had high R(out) despite evidence of flow across the stoma. These 4 patients underwent surgery and experienced resolution of symptoms. Of 9 patients without flow, R(out) was less than 13 mm Hg/ml/min in 4; these patients were successfully treated conservatively. CONCLUSIONS: The VIT is a useful and safe adjunct to clinical and MR imaging evaluation when ETV failure is suspected.

Spontaneous third ventriculostomy: definition by endoscopy and cerebrospinal fluid dynamics.

Chronic obstructive hydrocephalus is known to cause ventricular diverticula and, rarely, spontaneous ventriculostomy. The authors present the case of a patient in whom a spontaneous third ventriculostomy was identified with long-standing hydrocephalus secondary to aqueductal stenosis. To their knowledge, this is the first report in which a spontaneous stoma in the floor of the third ventricle was evaluated using endoscopy and cerebrospinal fluid dynamics studies. Both studies confirmed that the spontaneous stoma is similar in structure and function to surgical third ventriculostomy.

Three sisters with Chiari I malformation with and without associated syringomyelia.

Two daughters of non-consanguineous Ashkenazi Jewish parentage presented with occipital headaches in the second decade of life. Each had a symptomatic Chiari I malformation (CMI) and a large cervicothoracic syrinx. A third sister was diagnosed as having CMI without syrinx after MR screening of first-degree relatives. A fourth (the eldest) sister was asymptomatic and did not have CMI or syrinx. The girls' mother had platybasia on screening MR and a history of cough headaches. All four sisters also had demonstrable platybasic features on MR. The girls' father was asymptomatic and radiologically normal. This family represents the first reported case of three siblings in one family with confirmed CMI with or without syrinx. We discuss the possible genetic and mechanical mechanisms for the development of these abnormalities in this family.

The economic impacts of premature adult mortality: panel data evidence from KwaZulu-Natal, South Africa.

Measuring the household level economic impacts of AIDS-related deaths is of particular salience in South Africa, a country struggling with a legacy of poverty and economic inequality in the midst of an HIV epidemic. Household panel data that span more than a decade permit us to resolve many of the statistical problems that make it difficult to determine these impacts. After allowing for the impact of demographic adjustments and other coping strategies, we found evidence that these impacts are quite different across different types of households, and that the largest and most persistent effects were in the middle ranges of the South African income distribution, that is, households just above the poverty line. Households below that level seem less severely affected, whereas those above it seem to recover more quickly. All these results need to be treated with caution because their statistical precision is weak.