Abstract-Pulsed-current controlled wall motion in 20 m wide 200 m long 160 nm thick patterned Permalloy strips was studied using magnetic force microscopy. By sequential imaging, the displacement of Bloch walls as far as 200 m along the strip was observed. The direction of motion was in the same direction as the carrier velocity, which reversed with current polarity. The displacement per pulse was dependent upon the sample thickness and current density, which suggests that the mechanism is a combination of s-d exchange and hydromagnetic domain drag forces.
Peptide nucleic acids (PNAs) have gained much interest as molecular recognition tools in biology, medicine and chemistry. This is due to high hybridization efficiency to complimentary oligonucleotides and stability of the duplexes with RNA or DNA. We have synthesized 15/16-mer PNA probes to detect the HER2 mRNA. The performance of these probes to detect the HER2 target was evaluated by fluorescence imaging and fluorescence bead assays. The PNA probes have sufficiently discriminated between the wild type HER2 target and the mutant target with single base mismatches. Furthermore, the probes exhibited excellent linear concentration dependence between 0.4 to 400 fmol for the target gene. The results demonstrate potential application of PNAs as diagnostic probes with high specificity for quantitative measurements of amplifications or over-expressions of oncogenes.
Label-free deoxyribonucleic acid (DNA) hybridization detection using carbon nanotube transistor (CNT) arrays is demonstrated. The present scheme is distinguished from other CNT sensing methods as it uses a gate oxide overlayer on top of the carbon nanotubes, which function solely as charge sensors but are not participants in the chemical binding process. Because it involves DNA probe attachment on the gate oxide rather than on the CNT, this approach allows the use of conventional DNA functionalization and bioassay protocols, and is less prone to false positives. The signal sought is a few tens of millivolts in threshold voltage shift due to the increase of surface charges after target hybridization. The hybridization detection is shown to be highly specific and sensitive to a minimum concentration of about 30 nM of 61-mer DNA. Despite differences in the transistor properties due to the spread in the CNT parameters during fabrication, the yields are very high and the sensing characteristics are uniformly consistent in nearly all transistors.Index Terms-Biosensor, carbon nanotube, label-free deoxyribonucleic acid (DNA) detection, transistor.
This article describes the design, construction, and field-testing of a standalone networked animal-borne monitoring system conceived to study community ecology remotely. The system consists of an assemblage of identical battery-powered sensing devices with wireless communication capabilities that are each collar-mounted on a study animal and together form a mobile ad hoc network. The sensing modalities of each device include high-definition video, inertial accelerometry, and location resolved via a global positioning system module. Our system is conceived to use information exchange across the network to enable the devices to jointly decide without supervision when and how to use each sensing modality. The ultimate goal is to extend battery life while making sure that important events are appropriately documented. This requires judicious use of highly informative but power-hungry sensing modalities, such as video, because battery capacity is constrained by stringent weight and dimension restrictions. We have proposed algorithms to regulate sensing rates, data transmission among devices, and triggering for video recording based on location and animal group movements and configuration. We have also developed the hardware and firmware of our devices to reliably execute these algorithms in the exacting conditions of real-life deployments. We describe validation of the performance and reliability of our system using deployment results for a mission in Gorongosa National Park (Mozambique) to monitor two species in their natural habitat: the waterbuck and the African buffalo. We present movement data and snapshots of animal point-of-view videos collected by 14 fully operational devices collared on 10 waterbucks and 4 buffaloes. K E Y W O R D S environmental monitoring, sensor networks 1 | INTRODUCTION The study of social behavior of animal groups-as in predation, evasion, foraging, and migration-involves establishing hypotheses that explain how and why individuals in animal groups interact, and how the interactions lead to observed group phenomena (Ballerini et al., 2008; Couzin & Krause, 2003; Sumpter, 2006; Vicsek & Zafeiris, 2012). To validate hypotheses, extensive data on animal group behavior need to be collected and analyzed.Logging animal behavioral data by human observers is the most direct method, which requires ample time and effort, and is often hindered by spatiotemporal restrictions. In addition, human presence can influence the studied behavior (Altmann, 1974). Numerous efforts to develop and deploy animal-borne systems that collect behavioral data, over a range of dimensions (Dyo et al.& Martonosi, 2004) sought to overcome these limitations.Notably, there is growing interest in exploiting animal-borne imaging units to obtain animal point-of-view video recordings. In conjunction with geolocation data, they provide valuable information on an animal's interactions with the surrounding environment, other members of its species, and other species. However, because of battery capacity limitations, animal-born...
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