Rotational motion and rheotaxis of human sperm do not require functional CatSper channels and transmembrane Ca2+ signaling.

Navigation of sperm in fluid flow, called rheotaxis, provides long-range guidance in the mammalian oviduct. The rotation of sperm around their longitudinal axis (rolling) promotes rheotaxis. Whether sperm rolling and rheotaxis require calcium (Ca2+ ) influx via the sperm-specific Ca2+ channel CatSper, or rather represent passive biomechanical and hydrodynamic processes, has remained controversial. Here, we study the swimming behavior of sperm from healthy donors and from infertile patients that lack functional CatSper channels, using dark-field microscopy, optical tweezers, and microfluidics. We demonstrate that rolling and rheotaxis persist in CatSper-deficient human sperm. Furthermore, human sperm undergo rolling and rheotaxis even when Ca2+ influx is prevented. Finally, we show that rolling and rheotaxis also persist in mouse sperm deficient in both CatSper and flagellar Ca2+ -signaling domains. Our results strongly support the concept that passive biomechanical and hydrodynamic processes enable sperm rolling and rheotaxis, rather than calcium signaling mediated by CatSper or other mechanisms controlling transmembrane Ca2+ flux

Economic Scheduling in Grid Computing

Grid computing is a promising technology for future computing platforms. Here, the task of scheduling computing resources proves difficult as resources are geographically distributed and owned by individuals with different access and cost policies. This paper addresses the idea of applying economic models to the scheduling task. To this end a scheduling infrastructure and a market-economic method is presented. The efficiency of this approach in terms of response- and wait-time minimization as well as utilization is evaluated by simulations with real workload traces. The evaluations show that the presented economic scheduling algorithm provides similar or even better average weighted response-times as common algorithms like backfilling. This is especially promising as the presented economic models have additional advantages as e.g. support for different price models, optimization objectives, access policies or quality of service demands