An intra-laboratory investigation of on-wafer measurement reproducibility at millimeter-wave frequencies

Understanding the relative contribution of contact repeatability and overall reproducibility for on-wafer measurements provides useful insight into the significance of measurement comparisons. We report on an intra-laboratory investigation into contact repeatability and the variation that may be anticipated when measurements are reproduced in different laboratories using different equipment. We pay particular attention to the dispersion in measurement results arising from the use of on-wafer and off-wafer calibration. Experimental results are reported for measurements in the frequency range 140 GHz to 220 GHz, together with preliminary estimates of the repeatability limits for this type of measurement

Development of a Reference Wafer for On-Wafer Testing of Extreme Impedance Devices

This paper describes the design, fabrication, and testing of an on-wafer substrate that has been developed specifically for measuring extreme impedance devices using an on-wafer probe station. Such devices include carbon nano-tubes (CNTs) and structures based on graphene which possess impedances in the κ Ω range and are generally realised on the nano-scale rather than the micro-scale that is used for conventional on-wafer measurement. These impedances are far removed from the conventional 50- reference impedance of the test equipment. The on-wafer substrate includes methods for transforming from the micro-scale towards the nano-scale and reference standards to enable calibrations for extreme impedance devices. The paper includes typical results obtained from the designed wafer

National child measurement programme: detailed analysis of the 2007/08 national dataset

This report presents detailed secondary analyses to further our understanding of the epidemiology of child height, weight and Body Mass Index (BMI) across England. It attempts to explain some of the findings presented in the NHS Information Centre for Health and Social Care 2007/08 NCMP report. The report provides analysis of PCT participation levels and investigates data quality issues in the collection of the 2007/08 NCMP dataset. Data on prevalence of underweight, healthy weight, overweight and obesity are analysed, comparing the 2007/08 data to the 2006/07, and the 1990 baseline. Analyses by deprivation and ethnic group are also included. The report further examines how the distribution of BMI differs by age and sex of the child sample population, and investigates changes since the 1990 baseline. It looks at the association between obesity prevalence and characteristics of the individual children and the PCTs in which they were measured using regression analysis

Strategies for Traceable Submillimeter-Wave Vector Network Analyzer

This paper presents a strategy for achieving metrological traceability using vector network analyzers (VNAs) at submillimeter-wave frequencies (300-3000 GHz). The strategy includes the use of traceable calibration techniques designed for operation at these frequencies. Slight, but significant, physical differences between the waveguide line standards, used during calibration, are accommodated by applying a weighting technique to combine results using different calibration lines. Measurement uncertainty is assessed by analyzing replicate measurement data, to take account of the different waveguide interface interactions that occur when the line standards are connected to the VNA. The strategy is illustrated using measurements made in the WM-250 (750-1100 GHz) waveguide band

Ethane steam reforming over a platinum/alumina catalyst: effect of sulphur poisoning

In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane. Adsorption of hydrogen sulfide was measured at 293 and 873 K. At 873 K the adsorbed state of hydrogen sulfide in the presence of hydrogen was SH rather than S, even though the Pt:S ratio was unity. The effect of 11.2 ppm hydrogen sulfide or methanethiol on the steam reforming of ethane was studied at 873 K and 20 barg. Both poisons deactivated the catalyst over a number of hours, but methanethiol was found to be more deleterious, reducing the conversion by almost an order of magnitude, possibly due to the co-deposition of sulfur and carbon. Changes in the selectivity revealed that the effect of sulfur was not uniform on the reactions occurring, with the production of methane reduced proportionally more than the other products, due to the surface sensitivity of the hydrogenolysis and methanation reactions. The water-gas shift reaction was affected to a lesser extent. No regeneration was observed when hydrogen sulfide was removed from the feedstream in agreement with adsorption studies. A slight regeneration was observed when methanethiol was removed from the feed, but this was believed to be due to the removal of carbon rather than sulfur. The overall effect of sulfur poisoning was to reduce activity and enhance hydrogen selectivity

Beta bursting in the retrosplenial cortex is a neurophysiological correlate of environmental novelty which is disrupted in a mouse model of Alzheimer's disease

This is the author accepted manuscript. The final version is available from the Society for Neuroscience via the DOI in this recordThe retrosplenial cortex (RSC) plays a significant role in spatial learning and memory and is functionally disrupted in the early stages of Alzheimer's disease. In order to investigate neurophysiological correlates of spatial learning and memory in this region we employed in vivo electrophysiology in awake and freely moving male mice, comparing neural activity between wild-type and J20 mice, a transgenic model of Alzheimer's disease-associated amyloidopathy. To determine the response of the RSC to environmental novelty local field potentials were recorded while mice explored novel and familiar recording arenas. In familiar environments we detected short, phasic bursts of beta (20-30 Hz) oscillations (beta bursts) which arose at a low but steady rate. Exposure to a novel environment rapidly initiated a dramatic increase in the rate, size and duration of beta bursts. Additionally, theta-alpha/beta cross-frequency coupling was significantly higher during novelty, and spiking of neurons in the RSC was significantly enhanced during beta bursts. Finally, excessive beta bursting was seen in J20 mice, including increased beta bursting during novelty and familiarity, yet a loss of coupling between beta bursts and spiking activity. These findings support the concept that beta bursting may be responsible for the activation and reactivation of neuronal ensembles underpinning the formation and maintenance of cortical representations, and that disruptions to this activity in J20 mice may underlie cognitive impairments seen in these animals.SIGNIFICANCE STATEMENTThe retrosplenial cortex is thought to be involved in the formation, recall and consolidation of contextual memory. The discovery of bursts of beta oscillations in this region, which are associated with increased neuronal spiking and strongly upregulated while mice explore novel environments, provides a potential mechanism for the activation of neuronal ensembles, which may underlie the formation of cortical representations of context. Excessive beta bursting in the retrosplenial cortex of J20 mice, a mouse model of Alzheimer's disease, alongside the disassociation of beta bursting from neuronal spiking, may underlie spatial memory impairments previously shown in these mice. These findings introduce a novel neurophysiological correlate of spatial learning and memory, and a potentially new form of Alzheimer's disease related cortical dysfunction.University of ExeterJanssen PharmaceuticaAlzheimer’s Research U

Low temperature decreases bone mass in mice: Implications for humans

ObjectivesHumans exhibit significant ecogeographic variation in bone size and shape. However, it is unclear how significantly environmental temperature influences cortical and trabecular bone, making it difficult to recognize adaptation versus acclimatization in past populations. There is some evidence that cold‐induced bone loss results from sympathetic nervous system activation and can be reduced by nonshivering thermogenesis (NST) via uncoupling protein (UCP1) in brown adipose tissue (BAT). Here we test two hypotheses: (1) low temperature induces impaired cortical and trabecular bone acquisition and (2) UCP1, a marker of NST in BAT, increases in proportion to degree of low‐temperature exposure.MethodsWe housed wildtype C57BL/6J male mice in pairs at 26 °C (thermoneutrality), 22 °C (standard), and 20 °C (cool) from 3 weeks to 6 or 12 weeks of age with access to food and water ad libitum (N = 8/group).ResultsCool housed mice ate more but had lower body fat at 20 °C versus 26 °C. Mice at 20 °C had markedly lower distal femur trabecular bone volume fraction, thickness, and connectivity density and lower midshaft femur cortical bone area fraction versus mice at 26 °C (p < .05 for all). UCP1 expression in BAT was inversely related to temperature.DiscussionThese results support the hypothesis that low temperature was detrimental to bone mass acquisition. Nonshivering thermogenesis in brown adipose tissue increased in proportion to low‐temperature exposure but was insufficient to prevent bone loss. These data show that chronic exposure to low temperature impairs bone architecture, suggesting climate may contribute to phenotypic variation in humans and other hominins.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146428/1/ajpa23684.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146428/2/ajpa23684_am.pd

Domino-like transient dynamics at seizure onset in epilepsy

This is the final version. Available on open access from Public Library of Science via the DOI in this recordData Availability: We have made publicly available the 15 epochs of human EEG data containing generalized paroxysms classified as focal onset, and all 15 epochs containing seizures from one individual used in the manuscript, 1252 EEG epochs containing seizures classified as generalized onset and the 6 mouse mEC recordings. All data and the code used for the data analysis and model simulations they can be accessed via DOI 10.17605/OSF.IO/G2EXK.The International League Against Epilepsy (ILAE) groups seizures into “focal”, “generalized” and “unknown” based on whether the seizure onset is confined to a brain region in one hemisphere, arises in several brain region simultaneously, or is not known, respectively. This separation fails to account for the rich diversity of clinically and experimentally observed spatiotemporal patterns of seizure onset and even less so for the properties of the brain networks generating them. We consider three different patterns of domino-like seizure onset in Idiopathic Generalized Epilepsy (IGE) and present a novel approach to classification of seizures. To understand how these patterns are generated on networks requires understanding of the relationship between intrinsic node dynamics and coupling between nodes in the presence of noise, which currently is unknown. We investigate this interplay here in the framework of domino-like recruitment across a network. In particular, we use a phenomenological model of seizure onset with heterogeneous coupling and node properties, and show that in combination they generate a range of domino-like onset patterns observed in the IGE seizures. We further explore the individual contribution of heterogeneous node dynamics and coupling by interpreting in-vitro experimental data in which the speed of onset can be chemically modulated. This work contributes to a better understanding of possible drivers for the spatiotemporal patterns observed at seizure onset and may ultimately contribute to a more personalized approach to classification of seizure types in clinical practice.Engineering and Physical Sciences Research Council (EPSRC)Medical Research Council (MRC