3D printed waveguides: A revolution in low volume manufacturing for the 21st century

3D printing is a disruptive technology, offering the inherent capabilities for creating truly arbitrary 3D structures, with low manufacturing costs associated with low volume production runs. This paper provides an overv iew of the current progress in 3D printing of metal - pipe rectangular waveguide (MPRWG) components, from 10 GHz to 1 THz, at Imperial College London. First, measurements performed at the UK National Physical Laboratory demonstrate that 3D printed MPRWG perf ormance is comparable to standard commercial waveguides at X - band and W - band. Then, a fully 3D printed X - band dielectric flap tuneable phase shifter and W - band 6th - order inductive iris bandpass filter are demonstrated experimentally. Finally, an optically - controlled 500 GHz IQ vector modulator will also be presented; packaged laser diodes and high resistivity silicon implants are integrated within a hybrid 3D printed split - block module, representing a paradigm shift in additive manufacturing for realizing t uneable THz applications

Microwave characterization of low-loss FDM 3-D printed ABS with dielectric-filled metal-pipe rectangular waveguide spectroscopy

Over time the accuracy and speed by which a material can be characterized should improve. Today, the Nicolson-Ross-Weir (NRW) methodology represents a well-established method for extracting complex dielectric properties at microwave frequencies, with the use of a modern vector network analyzer. However, as will be seen, this approach suffers from three fundamental limitations to accuracy. Challenging NRW methods requires a methodical and robust investigation. To this end, using a dielectric-filled metal-pipe rectangular waveguide, five independent approaches are employed to accurately characterize the sample at the Fabry-Pérot resonance frequency (non-frequency dispersive modeling). In addition, manual Graphical and automated Renormalization spectroscopic approaches are introduced for the first time in waveguide. The results from these various modeling strategies are then compared and contrasted to NRW approaches. As a timely exemplar, 3-D printed acrylonitrile-butadiene-styrene (ABS) samples are characterized and the results compared with existing data available in the open literature. It is found that the various Fabry-Pérot resonance model results all agree with one another and validate the two new spectroscopic approaches; in so doing, exposing three limitations of the NRW methods. It is also shown that extracted dielectric properties for ABS differ from previously reported results and reasons for this are discussed. From measurement noise resilience analysis, a methodology is presented for determining the upper-bound signal-to-noise ratio for the vector network analyzer (not normally associated with such instrumentation). Finally, fused deposition modeling (FDM) 3-D printing results in a non-homogeneous sample that excites open-box mode resonances. This phenomenon is investigated for the first time, analytically and with various modeling strategies

Control of Brucella melitensis in endemic settings: a simulation study in the Nile Delta, Egypt

Small ruminant brucellosis remains endemic in many low and middle‐income countries (LMICs), where it poses a major economic and public health burden. Lack of resources to support long‐term vaccination, inherent characteristics of small ruminant production systems such as mixing of different flocks for grazing and limitations of the vaccines currently available, which can induce abortion in pregnant animals, have all hindered the effectiveness of control programs. In the current study, the likely effect of different control scenarios on the seroprevalence of brucellosis among the small ruminant population in a hypothetical area of an endemic region was simulated using compartmental models. The model accounts for variability in transmission rates between villages and also simulates control scenarios that target villages with high seroprevalence. Our results show that vaccination of young replacement animals only can effectively reduce the prevalence of small ruminant brucellosis in endemic settings if a high vaccination coverage is achieved. On the other hand, test and slaughter alone is not a promising strategy for control of small ruminant brucellosis under husbandry practices typical of endemic low‐resources settings. Furthermore, results show the potential success of some strategies requiring a relatively low overall vaccination coverage such as the vaccination of 50% of young replacements and 25% of adult animals each year. Control strategies selectively targeting high initial seroprevalence villages (p>10%) did not decrease the overall seroprevalence to acceptable levels in most of the examined scenarios. Scenario analysis showed that the efficacy of the simulated control strategies can be improved mostly by decreasing the proportion of between‐village trade and also by improving the performance of the used serological tests and increasing vaccine efficacy

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

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

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

Quantum Metrology: Towards an alternative definition for the meter

The motivation for this article came from an attempt to give an alternative definition for the meter, the SI unit for measuring length. As a starting point towards this goal, in this piece of work we present the underlying theory behind our approach which uses ideas from quantum field theory and noncommutative geometry, in particular the notion of an odd K-cycle which is based on the Dirac operator (and its inverse, the Dirac propagator). Using (the perhaps more familiar) physics terminology, the key point in our strategy is this: instead of measuring length directly in space-time we measure the "algebraic (spectral) length" in the space of the corresponding quantum states of some particle (fermion) acted upon by the Dirac propagator. This approach shares the spirit of the unanimus vote of the 24th General Conference of Standards and Measures (21st October 2011) in Serves, France for the redefinition of the fundamental units using Planck's constant.Comment: Extended version of an invited talk during the 4th Tactical Conference on Metrology, 3-4 February 2012, National Technical University of Athens, Athens Greec

An Intermittent Live Cell Imaging Screen for siRNA Enhancers and Suppressors of a Kinesin-5 Inhibitor

Kinesin-5 (also known as Eg5, KSP and Kif11) is required for assembly of a bipolar mitotic spindle. Small molecule inhibitors of Kinesin-5, developed as potential anti-cancer drugs, arrest cell in mitosis and promote apoptosis of cancer cells. We performed a genome-wide siRNA screen for enhancers and suppressors of a Kinesin-5 inhibitor in human cells to elucidate cellular responses, and thus identify factors that might predict drug sensitivity in cancers. Because the drug's actions play out over several days, we developed an intermittent imaging screen. Live HeLa cells expressing GFP-tagged histone H2B were imaged at 0, 24 and 48 hours after drug addition, and images were analyzed using open-source software that incorporates machine learning. This screen effectively identified siRNAs that caused increased mitotic arrest at low drug concentrations (enhancers), and vice versa (suppressors), and we report siRNAs that caused both effects. We then classified the effect of siRNAs for 15 genes where 3 or 4 out of 4 siRNA oligos tested were suppressors as assessed by time lapse imaging, and by testing for suppression of mitotic arrest in taxol and nocodazole. This identified 4 phenotypic classes of drug suppressors, which included known and novel genes. Our methodology should be applicable to other screens, and the suppressor and enhancer genes we identified may open new lines of research into mitosis and checkpoint biology

UNDERSTANDING HOW FARMERS LEARN

SUMMARY Changing the behaviour of people is challenging; changing farmer behaviour is possibly even more so. The evidence presented here suggests that a number of widely-used farmer communication methods are poorly thought of by farmers. Information received by farmers from other farmers was regarded as useful, and this information was regarded as being more useful than that from a number of rural professionals. Those wishing to change farmer behaviour need to: invest time to gain trust; involve farmers in the process of learning; use multiple methods to teach and encourage farmers to talk with each other and scientists in a learning community. INTRODUCTION The current New Zealand Government expects the New Zealand scientific community to improve the rate of uptake of new knowledge by businesses and thereby improve the New Zealand economy. Similarly, Centres of Research Excellence funded by the Tertiary Education Commission are expected to show how they will translate new knowledge into improved community benefit, and the recent Primary Growth Partnership granted to Beef + Lamb New Zealand (the farmer-owned industry organisation representing New Zealand&apos;s sheep and beef farmers) aims to improve access to information by farmers. However, the rate at which behaviour change by business owners is driven through the provision of new scientific evidence is variable and this is particularly so in the agricultural sector. Indeed, This paper reports on a pilot farmer learning project and a survey of New Zealand sheep farmer opinion with the intent to show how farmers go about learning new technologies, including how they like to receive information and who farmers perceive as providing useful information