A Schottky/2-DEG varactor diode for millimeter and submillimeter wave multiplier applications

A new Schottky diode is investigated for use as a multiplier element in the millimeter and submillimeter wavelength regions. The new diode is based on the Schottky contact at the edge of a 2-dimensional electron gas (2-DEG). As a negative voltage is applied to the Schottky contact, the depletion layer between the Schottky contact and the 2-DEG expands and the junction capacitance decreases, resulting in a nonlinear capacitance-voltage characteristic. In this paper, we outline the theory, design, fabrication, and evaluation of the new device. Recent results include devices having cutoff frequencies of 1 THz and above. Preliminary multiplier results are also presented

The effectiveness of three types of practice in word recognition in grades II and III

Thesis (Ed.M.)--Boston Universit

Electron-impact ionization of atomic hydrogen at 2 eV above threshold

The convergent close-coupling method is applied to the calculation of fully differential cross sections for ionization of atomic hydrogen by 15.6 eV electrons. We find that even at this low energy the method is able to yield predictive results with small uncertainty. As a consequence we suspect that the experimental normalization at this energy is approximately a factor of two too high.Comment: 10 page

Exploring the impact of Osteogenesis Imperfecta on families: A mixed-methods systematic review

Background: Osteogenesis Imperfecta (OI) is a rare genetic condition whose key characteristic is increased bone fragility. OI has the potential to impact upon all family members, making it important to consider the challenges families face, how they cope and their support needs as the affected individual moves from childhood through to adult life. / Objective: To conduct a mixed-methods systematic review investigating the experiences of families when a family member is affected with OI. / Methods: A systematic search of seven electronic databases, relevant patient organisation websites and reference lists was conducted. Data extraction was performed for all studies that met the eligibility and quality criteria. Results were synthesised following the principles of thematic analysis. / Results: One mixed-method, six qualitative and six quantitative studies were included in the review. Three overarching themes were identified through thematic analysis: Impact of OI on the psychosocial wellbeing of families, impact on family life and evolving roles and relationships. Fear of fractures and the uncertainty of when the next fracture will occur are key issues that permeate all areas of family life and impact upon all family members. / Conclusion: The experiences, coping strategies and support needs of families affected by OI were highly variable and changed over time. Future research should address the need for adaptive health and education interventions that support all family members

Forehead reflectance photoplethysmography to monitor heart rate: preliminary results from neonatal patients

Around 5%–10% of newborn babies require some form of resuscitation at birth and heart rate (HR) is the best guide of efficacy. We report the development and first trial of a device that continuously monitors neonatal HR, with a view to deployment in the delivery room to guide newborn resuscitation. The device uses forehead reflectance photoplethysmography (PPG) with modulated light and lock-in detection. Forehead fixation has numerous advantages including ease of sensor placement, whilst perfusion at the forehead is better maintained in comparison to the extremities. Green light (525 nm) was used, in preference to the more usual red or infrared wavelengths, to optimize the amplitude of the pulsatile signal. Experimental results are presented showing simultaneous PPG and electrocardiogram (ECG) HRs from babies (n = 77), gestational age 26–42 weeks, on a neonatal intensive care unit. In babies ≥32 weeks gestation, the median reliability was 97.7% at ±10 bpm and the limits of agreement (LOA) between PPG and ECG were +8.39 bpm and −8.39 bpm. In babies <32 weeks gestation, the median reliability was 94.8% at ±10 bpm and the LOA were +11.53 bpm and −12.01 bpm. Clinical evaluation during newborn deliveries is now underway

Cassiopeia A: dust factory revealed via submillimetre polarimetry

If Type-II supernovae - the evolutionary end points of short-lived, massive stars - produce a significant quantity of dust (>0.1 M_sun) then they can explain the rest-frame far-infrared emission seen in galaxies and quasars in the first Gyr of the Universe. Submillimetre observations of the Galactic supernova remnant, Cas A, provided the first observational evidence for the formation of significant quantities of dust in Type-II supernovae. In this paper we present new data which show that the submm emission from Cas A is polarised at a level significantly higher than that of its synchrotron emission. The orientation is consistent with that of the magnetic field in Cas A, implying that the polarised submm emission is associated with the remnant. No known mechanism would vary the synchrotron polarisation in this way and so we attribute the excess polarised submm flux to cold dust within the remnant, providing fresh evidence that cosmic dust can form rapidly. This is supported by the presence of both polarised and unpolarised dust emission in the north of the remnant, where there is no contamination from foreground molecular clouds. The inferred dust polarisation fraction is unprecedented (f_pol ~ 30%) which, coupled with the brief timescale available for grain alignment (<300 yr), suggests that supernova dust differs from that seen in other Galactic sources (where f_pol=2-7%), or that a highly efficient grain alignment process must operate in the environment of a supernova remnant.Comment: In press at MNRAS, 10 pages, print in colou

Drinking by sea snakes from oceanic freshwater lenses at first rainfall ending seasonal drought

Acquisition of fresh water (FW) is problematic for FW-dependent animals living in marine environments that are distant from sources of FW associated with land. Knowledge of how marine vertebrates respond to oceanic rainfall, and indeed the drinking responses of vertebrates generally following drought, is extremely scant. The Yellow-bellied Sea Snake (Hydrophis platurus) is the only pelagic species of squamate reptile and ranges across the Indo-Pacific oceans, having one of the largest geographic distributions of any vertebrate species. It requires FW and dehydrates at sea during periods of drought. Here we report drinking behaviors of sea snakes precisely at the transition from dry to wet season when rainfall first impacted the ocean following 6 months of seasonal drought. We show that the percentage of sea snakes that voluntarily drank FW in the laboratory when captured over eight successive days decreased from 80% to 13% before and after rainfall commenced, respectively. The percentage of snakes that drank immediately following capture exhibited a significant linear decline as the earliest rains of the wet season continued. Drinking by snakes indicates thirst related to dehydration, and thus thirsty snakes must have dehydrated during the previous six months of drought. Hence, the progressive decline in percentage of thirsty snakes indicates they were drinking from FW lenses associated with the first rainfall events of the wet season. These data reinforce the importance of accessing oceanic FW from precipitation, with implications for survival and distribution of pelagic populations that might be subjected to intensifying drought related to climate change

Living with Osteogenesis Imperfecta: A qualitative study exploring experiences and psychosocial impact from the perspective of patients, parents and professionals

BACKGROUND: Osteogenesis Imperfecta (OI) is a rare genetic condition characterised by increased bone fragility. Recurrent fractures, pain and fatigue have a considerable impact on many aspects of the life of a person affected with OI and their families. OBJECTIVE: To improve our understanding of the impact of OI on the daily lives of individuals and families and consider how the condition is managed so that support needs can be better addressed. METHODS: Semi-structured qualitative interviews (n = 56) were conducted with adults affected with OI, with (n = 9) and without children (n = 8), parents of children affected with OI (n = 8), health professionals (n = 29) and patient advocates (n = 2). Interviews were digitally recorded, transcribed verbatim and analysed using thematic analysis. RESULTS: Three overarching themes are described: OI is not just a physical condition, parenting and family functioning and managing the condition. Fractures, chronic pain and tiredness impact on daily life and emotional well-being. For parents with OI, pain, tiredness and mobility issues can limit interactions and activities with their children. Specialist paediatric health services for OI were highly valued. The need for more emotional support and improved coordination of adult health services was highlighted. CONCLUSIONS: Our findings allow a better understanding of the day-to-day experiences of individuals and families affected with OI. Supporting emotional well-being needs greater attention from policy makers and researchers. Improvements to the coordination of health services for adults with OI are needed and an in-depth exploration of young people's support needs is warranted with research focused on support through the teenage years

Targeting danger molecules in tendinopathy: the HMGB1/TLR4 axis

Objectives: To seek evidence of the danger molecule, high-mobility group protein B1 (HMGB1) expression in human tendinopathy and thereafter, to explore mechanisms where HMGB1 may regulate inflammatory mediators and matrix regulation in human tendinopathy. Methods: Torn supraspinatus tendon (established pathology) and matched intact subscapularis tendon (representing ‘early pathology’) biopsies were collected from patients undergoing arthroscopic shoulder surgery. Control samples of subscapularis tendon were collected from patients undergoing arthroscopic stabilisation surgery. Markers of inflammation and HMGB1 were quantified by reverse transcriptase PCR (RT-PCR) and immunohistochemistry. Human tendon-derived primary cells were derived from hamstring tendon tissue obtained during hamstring tendon anterior cruciate ligament reconstruction and used through passage 3. In vitro effects of recombinant HMGB1 on tenocyte matrix and inflammatory potential were measured using quantitative RT-PCR, ELISA and immunohistochemistry staining. Results: Tendinopathic tissues demonstrated significantly increased levels of the danger molecule HMGB1 compared with control tissues with early tendinopathy tissue showing the greatest expression. The addition of recombinant human HMGB1 to tenocytes led to significant increase in expression of a number of inflammatory mediators, including interleukin 1 beta (IL-1β), IL-6, IL-33, CCL2 and CXCL12, in vitro. Further analysis demonstrated rhHMGB1 treatment resulted in increased expression of genes involved in matrix remodelling. Significant increases were observed in Col3, Tenascin-C and Decorin. Moreover, blocking HMGB1 signalling via toll-like receptor 4 (TLR4) silencing reversed these key inflammatory and matrix changes. Conclusion: HMGB1 is present in human tendinopathy and can regulate inflammatory cytokines and matrix changes. We propose HMGB1 as a mediator driving the inflammatory/matrix crosstalk and manipulation of the HMGB1/TLR4 axis may offer novel therapeutic approaches targeting inflammatory mechanisms in the management of human tendon disorders