Ka-band Ga-As FET noise receiver/device development

The development of technology for a 30 GHz low noise receiver utilizing GaAs FET devices exclusively is discussed. This program required single and dual-gate FET devices, low noise FET amplifiers, dual-gate FET mixers, and FET oscillators operating at Ka-band frequencies. A 0.25 micrometer gate FET device, developed with a minimum noise figure of 3.3 dB at 29 GHz and an associated gain of 7.4 dB, was used to fabricate a 3-stage amplifier with a minimum noise figure and associated gain of 4.4 dB and 17 dB, respectively. The 1-dB gain bandwidth of this amplifier extended from below 26.5 GHz to 30.5 GHz. A dual-gate mixer with a 2 dB conversion loss and a minimum noise figure of 10 dB at 29 GHz as well as a dielectric resonator stabilized FET oscillator at 25 GHz for the receiver L0. From these components, a hybrid microwave integrated circuit receiver was constructed which demonstrates a minimum single-side band noise figure of 4.6 dB at 29 GHz with a conversion gain of 17 dB. The output power at the 1-dB gain compression point was -5 dBm

Effects of impingement of rocket exhaust gases and solid particles on a spacecraft Interim report, Mar. 18 - Oct. 25, 1966

Impingement damage to spacecraft from rocket exhaust gases and micron sized metal particle

Machine learning with the hierarchy‐of‐hypotheses (HoH) approach discovers novel pattern in studies on biological invasions

Research synthesis on simple yet general hypotheses and ideas is challenging in scientific disciplines studying highly context‐dependent systems such as medical, social, and biological sciences. This study shows that machine learning, equation‐free statistical modeling of artificial intelligence, is a promising synthesis tool for discovering novel patterns and the source of controversy in a general hypothesis. We apply a decision tree algorithm, assuming that evidence from various contexts can be adequately integrated in a hierarchically nested structure. As a case study, we analyzed 163 articles that studied a prominent hypothesis in invasion biology, the enemy release hypothesis. We explored if any of the nine attributes that classify each study can differentiate conclusions as classification problem. Results corroborated that machine learning can be useful for research synthesis, as the algorithm could detect patterns that had been already focused in previous narrative reviews. Compared with the previous synthesis study that assessed the same evidence collection based on experts' judgement, the algorithm has newly proposed that the studies focusing on Asian regions mostly supported the hypothesis, suggesting that more detailed investigations in these regions can enhance our understanding of the hypothesis. We suggest that machine learning algorithms can be a promising synthesis tool especially where studies (a) reformulate a general hypothesis from different perspectives, (b) use different methods or variables, or (c) report insufficient information for conducting meta‐analyses

The fate of hypoechoic cleft

Background: Hypoechoic clefts are small defects found on ultrasonographs in the intact rotator cuff tendon after rotator cuff repair. Little is known about the fate of these hypoechoic clefts, as to whether they will heal, persist, or develop into a retear. Methods: This prospective study involved 24 patients who underwent arthroscopic rotator cuff repair surgery and were found to have a hypoechoic cleft at the 6-month postoperative ultrasonograph. A subsequent ultrasonography follow-up was performed at 9 months or later by the same ultrasonographer and the repair re-examined. Results: At an average postoperative follow-up of 21 months, 14 of the 25 hypoechoic clefts (56%) had healed; 5 (20%) had persistent clefts whereas 6 (24%) had progressed to a full-thickness rotator cuff retear. Patients with a hypoechoic cleft ≥36 mm2 were 5 times more likely to have a retear than patients with hypoechoic cleft <36 mm2 (relative risk = 5.1; P < .05). Patients with hypoechoic clefts ≥36 mm2 had a higher frequency of pain during activity and sleep and a lower level of satisfaction at the 21-month follow-up compared to those with small hypoechoic clefts (P = .05). Conclusion: This is the first study to evaluate the natural history of a hypoechoic cleft found at ultrasonography following rotator cuff repair. The study showed that clefts less than 36 mm2 are likely to heal, while those greater than 36 mm2 are at high risk of progressing to full-thickness retears

Particle Topology, Braids, and Braided Belts

Recent work suggests that topological features of certain quantum gravity theories can be interpreted as particles, matching the known fermions and bosons of the first generation in the Standard Model. This is achieved by identifying topological structures with elements of the framed Artin braid group on three strands, and demonstrating a correspondence between the invariants used to characterise these braids (a braid is a set of non-intersecting curves, that connect one set of $N$ points with another set of $N$ points), and quantities like electric charge, colour charge, and so on. In this paper we show how to manipulate a modified form of framed braids to yield an invariant standard form for sets of isomorphic braids, characterised by a vector of real numbers. This will serve as a basis for more complete discussions of quantum numbers in future work.Comment: 21 pages, 16 figure

Transcriptome analysis reveals nuclear-encoded proteins for the maintenance of temporary plastids in the dinoflagellate Dinophysis acuminata

<p>Abstract</p> <p>Background</p> <p><it>Dinophysis </it>is exceptional among dinoflagellates, possessing plastids derived from cryptophyte algae. Although <it>Dinophysis </it>can be maintained in pure culture for several months, the genus is mixotrophic and needs to feed either to acquire plastids (a process known as kleptoplastidy) or obtain growth factors necessary for plastid maintenance. <it>Dinophysis </it>does not feed directly on cryptophyte algae, but rather on a ciliate (<it>Myrionecta rubra</it>) that has consumed the cryptophytes and retained their plastids. Despite the apparent absence of cryptophyte nuclear genes required for plastid function, <it>Dinophysis </it>can retain cryptophyte plastids for months without feeding.</p> <p>Results</p> <p>To determine if this dinoflagellate has nuclear-encoded genes for plastid function, we sequenced cDNA from <it>Dinophysis acuminata</it>, its ciliate prey <it>M. rubra</it>, and the cryptophyte source of the plastid <it>Geminigera cryophila</it>. We identified five proteins complete with plastid-targeting peptides encoded in the nuclear genome of <it>D. acuminata </it>that function in photosystem stabilization and metabolite transport. Phylogenetic analyses show that the genes are derived from multiple algal sources indicating some were acquired through horizontal gene transfer.</p> <p>Conclusions</p> <p>These findings suggest that <it>D. acuminata </it>has some functional control of its plastid, and may be able to extend the useful life of the plastid by replacing damaged transporters and protecting components of the photosystem from stress. However, the dearth of plastid-related genes compared to other fully phototrophic algae suggests that <it>D. acuminata </it>does not have the nuclear repertoire necessary to maintain the plastid permanently.</p

Historiographical review: dreams or designs, cults or constructions? The study of images of monarchs

This historiographical review surveys studies by cultural historians of images of monarchs, including Elizabeth I, Mary Queen of Scots, Charles I, and Victoria. These are not biographies, but analyses of the diverse and often contradictory representations of monarchs in their own times and afterwards. The review considers the variety of approaches in the field, from iconographical decoding to political history to the application of psychoanalysis to a national culture. It discusses the extent to which queens tend to be conflated to an enduring model of idealized femininity; how seriously we should take representations of monarchs as sacred; and the incorporation of sexuality in the royal image. It considers resistance as well as assent to the royal image, and how far the royal image as art object can become detached from the ideology which produced it. It concludes by observing our mixed motivations for interest in past ‘cults’ of monarchs, seeking in them at once the exotic difference of the past and comparisons with public figures of our own time