Development of Latent Fingermarks on Surfaces of Food‐A More Realistic Approach

Latent fingermark developing methods from food (mandarin, egg, banana, apple, potato, carrot, eggplant, onion, bell pepper, and tomato) surface has been studied by 10 methods, including powdering method, small particle reagent method, and cyanoacrylate fuming method. The foods were stored under two conditions (room temperature and refrigerator) before fingermark deposition and aged for 2, 24, 48, and 72 h before fingermark development. In most of the food surfaces used in this study, cyanoacrylate fuming with 80% relative humidity was superior to the powder or small particle reagent methods. The quality of the fingermarks varied depending on the storage conditions before the fingermark deposition (in the refrigerator or at ambient temperature) and the time elapsed since the fingermark deposition. However, the storage conditions before the fingermark deposition and the time elapsed since the fingermark deposition did not show any correlation with the quality of the fingermark.     

Willingness to Pay for Solar Lanterns: Does the Trial Period Play a Role?

Where electricity access is limited, solar lanterns are a viable and relatively inexpensive source of basic lighting for households. However, the creation of commercially viable business models for solar lanterns is difficult because the customers are poor and make decisions under tight liquidity constraints. To understand the economics of technology adoption in the case of solar lanterns, we conduct a field experiment on willingness to pay (WTP) for solar lanterns in rural Uttar Pradesh. Applying the Becker–DeGroot–Marschak method of eliciting WTP, we evaluate the ability of a trial period and postponed payment to increase sales. We find no evidence for the effectiveness of the trial period and only weak evidence for the positive effect of postponed payment. Overall, WTP for the product among the customers is low. There is no clear evidence for concerns about the uncertain quality of the product, liquidity constraints, or present‐bias. In this context, policies to subsidize very small solar lanterns would not correct a market failure, as people appear to have only a limited interest in the product.