Spin-transfer switching and low-field precession in exchange-biased spin valve nano-pillars

Using a three-dimensional focused-ion beam lithography process we have fabricated nanopillar devices which show spin transfer torque switching at zero external magnetic fields. Under a small in-plane external bias field, a field-dependent peak in the differential resistance versus current is observed similar to that reported in asymmetrical nanopillar devices. This is interpreted as evidence for the low-field excitation of spin waves which in our case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange bias layer coupled to a relatively thin CoFe fixed layer.Comment: 11 pages, 4 figures. To appear in APL, April 200

Spin-orbit coupled j=1/2 iridium moments on the geometrically frustrated fcc lattice

Motivated by experiments on the double perovskites La2ZnIrO6 and La2MgIrO6, we study the magnetism of spin-orbit coupled j=1/2 iridium moments on the three-dimensional, geometrically frustrated, face-centered cubic lattice. The symmetry-allowed nearest-neighbor interaction includes Heisenberg, Kitaev, and symmetric off-diagonal exchange. A Luttinger-Tisza analysis shows a rich variety of orders, including collinear A-type antiferromagnetism, stripe order with moments along the [111]-direction, and incommensurate non-coplanar spirals, and we use Monte Carlo simulations to determine their magnetic ordering temperatures. We argue that existing thermodynamic data on these iridates underscores the presence of a dominant Kitaev exchange, and also suggest a resolution to the puzzle of why La2ZnIrO6 exhibits `weak' ferromagnetism, but La2MgIrO6 does not.Comment: 5 pages, 5 figs, significantly revised to address referee comments, to appear in PRB Rapid Com

Combining cellular and gene therapy approaches for treatment of intracranial tumors.

New treatments are needed for brain metastasis, which is associated with high morbidity and mortality. Two novel cellular and gene therapy modalities were evaluated in xenograft models for human breast cancer. The individual and especially the combined treatments with alloreactive cytotoxic T lymphocytes and replicating retroviral vectors coding for prodrug activating enzymes followed later with nontoxic prodrug demonstrated efficacy without off-target effects

Development of a new splanchnic perfusion sensor

the continuous monitoring of splanchnic organ oxygen saturation (SpO2) would make the early detection of inadequate tissue oxygenation feasible, reducing the risk of hypoperfusion, severe ischemia, multiple organ failure, and, ultimately, death. In an attempt to create a splanchnic SpO2 sensor that can be used intra-operatively, pre-operatively and post-operatively this paper describes the design and technical evaluation of fiber optic based reflectance pulse oximeter sensor and processing system. In a detailed investigation to determine the optimal source-emitter spacing it was found that the optimum separation distance was between 3mm and 6mm. In vivo thermal testing showed that the rise in temperature at the tip of the fiber at both wavelengths was insignificant and therefore should have no effect in the splanchnic tissue

Development of a Reflectance Fibre-Optic Pulse Oximetry Probe for Use in Abdominal Organs

The early detection of inadequate splanchnic tissue oxygenation would reduce the risk of hypoperfusion, severe ischaemia, and multiple organ failure [1]. None of the currently available methods provide continuous monitoring of splanchnic perfusion pre-operatively, operatively and post-operatively. In an attempt to overcome these limitations, a new fibre-optic probe utilizing the principle of reflectance pulse oximetry was developed. The separation distance between the source and detector fibres of the probe has a direct impact on the quality of the photoplethysmographic (PPG) signal and the accurate estimation of blood oxygen saturation (SpO2) [2]. Prior to finalising the probe design, an investigation was conducted to establish the optimum source-detector separation

Fibre-optic sensor for monitoring splanchnic perfusion

There is a need for reliable monitoring of abdominal organ oxygen saturation (SpO2). Preliminary pilot studies using an electro-optical sensor have shown that good quality photoplethysmographic (PPG) signals can be detected from various human abdominal organs during open labarotomy. In an attempt to develop a splanchnic perfusion sensor that can be used pre-operatively, operatively and post-operatively, a new fibre optic sensor and processing system utilising the principle of reflectance pulse oximetry has been developed. To determine the optimal configuration (source/detector separation) of the optical fibres, an experimental procedure was carried out to examine the effect of separation distance on the acquired PPG signals, and to ultimately select a source-detector separation distance for the final design of the fibre-optic probe. PPG signals were obtained from the finger for all separation distances. The optimum range for source-detector separation was found to be between 3mm and 6mm. At closer separation, PPG signals were too erratic and unstable, while at larger separation the amplitudes of PPG signals were very small. The development of the fibre-optic probe as well as the experimental set-up and the results of the investigations are presented

Optimal spacing between transmitting and receiving optical fibres in reflectance pulse oximetry

Splanchnic ischaemia can ultimately lead to cellular hypoxia and necrosis, and may well contribute to the development of multiple organ failures and increased mortality. Therefore, it is of utmost importance to monitor abdominal organ blood oxygen saturation (SpO2). Pulse oximetry has been widely accepted as a reliable method for monitoring oxygen saturation of arterial blood. Animal studies have also shown it to be effective in the monitoring of blood oxygen saturation in the splanchnic region. However, commercially available pulse oximeter probes are not suitable for the continuous assessment of SpO2 in the splanchnic region. Therefore, there is a need for a new sensor technology that will allow the continuous measurement of SpO2 in the splanchnic area pre-operatively, operatively and post-operatively. For this purpose, a new fibre optic sensor and processing system utilising the principle of reflectance pulse oximetry has been developed. The accuracy in the estimation of SpO2 in pulse oximetry depends on the quality and amplitude of the photoplethysmographic (PPG) signal and for this reason an experimental procedure was carried out to examine the effect of the source-detector separation distance on the acquired PPG signals, and to ultimately select an optimal separation for the final design of the fibre-optic probe. PPG signals were obtained from the finger for different separation distances between the emitting and detecting fibres. Good quality PPG signals with large amplitudes and high signal-to-noise ratio were detected in the range of 3mm to 6mm. At separation distances between 1mm and 2mm, PPG signals were erratic with no resemblance to a conventional PPG signal. At separation distances greater than 6mm, the amplitudes of PPG signals were very small and not appropriate for processing. This investigation indicates the suitability of optical fibres as a new pulse oximetry sensor for estimating blood oxygen saturation (SpO2) in the splanchnic region

In the Sweet Bye and Bye

https://digitalcommons.library.umaine.edu/mmb-ps/1668/thumbnail.jp

The effect of genomic information on optimal contribution selection in livestock breeding programs

BACKGROUND: Long-term benefits in animal breeding programs require that increases in genetic merit be balanced with the need to maintain diversity (lost due to inbreeding). This can be achieved by using optimal contribution selection. The availability of high-density DNA marker information enables the incorporation of genomic data into optimal contribution selection but this raises the question about how this information affects the balance between genetic merit and diversity. METHODS: The effect of using genomic information in optimal contribution selection was examined based on simulated and real data on dairy bulls. We compared the genetic merit of selected animals at various levels of co-ancestry restrictions when using estimated breeding values based on parent average, genomic or progeny test information. Furthermore, we estimated the proportion of variation in estimated breeding values that is due to within-family differences. RESULTS: Optimal selection on genomic estimated breeding values increased genetic gain. Genetic merit was further increased using genomic rather than pedigree-based measures of co-ancestry under an inbreeding restriction policy. Using genomic instead of pedigree relationships to restrict inbreeding had a significant effect only when the population consisted of many large full-sib families; with a half-sib family structure, no difference was observed. In real data from dairy bulls, optimal contribution selection based on genomic estimated breeding values allowed for additional improvements in genetic merit at low to moderate inbreeding levels. Genomic estimated breeding values were more accurate and showed more within-family variation than parent average breeding values; for genomic estimated breeding values, 30 to 40% of the variation was due to within-family differences. Finally, there was no difference between constraining inbreeding via pedigree or genomic relationships in the real data. CONCLUSIONS: The use of genomic estimated breeding values increased genetic gain in optimal contribution selection. Genomic estimated breeding values were more accurate and showed more within-family variation, which led to higher genetic gains for the same restriction on inbreeding. Using genomic relationships to restrict inbreeding provided no additional gain, except in the case of very large full-sib families