Abstract: A system for generating mechanical work from the expansion of water as it freezes includes an outer housing, an inner housing, and a chamber between the outer housing and the inner housing. Water may be supplied to the chamber and a coolant may be supplied around the outer housing and inside the inner housing. As the water freezes, its volumetric expansion may force a piston to move, generating useful mechanical work.

Abstract: Disclosed are various embodiments for selecting advertising for presentation to users in association with digital content items. Characteristics of a user are determined based at least in part on historical data that associates the user with one or more items. An advertisement is selected from an inventory of advertisements for presentation in association with a digital content item requested by the user. The advertisement is selected based at least in part on a highest value placed on the characteristics of the user by an advertiser.

Abstract: Disclosed are various embodiments for selecting advertising for presentation to users in association with digital content items. Characteristics of a user are determined based at least in part on historical data that associates the user with one or more items. An advertisement is selected from an inventory of advertisements for presentation in association with a digital content item requested by the user. The advertisement is selected based at least in part on a highest value placed on the characteristics of the user by an advertiser.

Abstract: Disclosed are various embodiments for selecting advertising for presentation to customers in association with digital content items. Characteristics of a customer are determined based at least in part on historical data that associates the customer with one or more items. An advertisement is selected from an inventory of advertisements for presentation in association with a digital content item requested by the customer. The advertisement is selected based at least in part on a highest value placed on the characteristics of the customer by an advertiser for a presentation of the advertisement to the customer.

Abstract: Systems and methods for time based management of digital content used with electronic devices lacking a connection to a common reference time keeping device are provided. Timing calibrations are used that, when applied to times measured by such disconnected electronic devices, allow the devices to calculate modified time measurements that are approximately equal to that of the reference time keeping device. The calibration time and other calibration information for the disconnected electronic devices may be stored by a digital content service and conveyed with digital content transferred from the digital content service to the disconnected electronic devices via portable data storage devices. In this manner, digital content may be consumed by a user on a plurality of disconnected electronic devices without violating license agreements associated with the digital content.

Abstract: Systems and methods for time based management of digital content used with electronic devices lacking a connection to a common reference time keeping device are provided. Timing calibrations are used that, when applied to times measured by such disconnected electronic devices, allow the devices to calculate modified time measurements that are approximately equal to that of the reference time keeping device. The calibration time and other calibration information for the disconnected electronic devices may be stored by a digital content service and conveyed with digital content transferred from the digital content service to the disconnected electronic devices via portable data storage devices. In this manner, digital content may be consumed by a user on a plurality of disconnected electronic devices without violating license agreements associated with the digital content.