Sandia Senior Design Collaboration: Vacuum Sensor Design

Sandia National Laboratories has requested a fully mechanical device to close a circuit after launch has occurred and the device enters a vacuum. Intended for applications in rockets and missiles, the device must fit in a 36 degree wedge with a 6.8 inch radius that is 6 inches in height and be ready to bolt onto a rocket. The pressure switch must be prevented from actuating until a launch acceleration ranging from 20 to 27g is detected. The pressure switch must close the circuit after a pressure of 10-1 Torr is reached and before a pressure of 10-6 Torr is reached. The switch must remain closed after the switch is actuated. The pressure switch is required to close a circuit carrying 30 VDC with a 15 ohm load for up to 15 seconds. The switch itself is allowed to have a maximum resistance of 0.2 ohms. The switch must be resettable for Sandia to conduct multiple test runs. Our contact at Sandia expressed interest in 3D printed components. This design detects the launch acceleration by separating a calibrated mass from a magnet. Before the acceleration sensor is tripped, it prevents the pressure switch from actuating. The pressure switch contains a substance which is a liquid at the temperatures and pressures experienced before the vacuum environment is reached and vaporizes in the vacuum environment. The phase change causes an expansion of the fluid container, which is used to move the actuator magnet near a reed switch and close the circuit. Thus, this project applies thermodynamics, system dynamics, numerical methods, material selection, and mechanical component design. A prototype of the design will be built and sent alongside a report to Sandia National Laboratories. Sandia will test the device on a sounding rocket. This project will provide Sandia with one of ten prototype devices to test. The switch provided will be used to detect when the rocket has left the atmosphere and has activated safety measures

Recent Decisions

Comments on recent decisions by Richard M. Di Valerio, James A. Uhl, Donald J. Prebenda, Wilbur L. Pollard, William N. Antonis, Richard E. Shipman, Richard D. Heman, Thomas P. Meaney, Jr., John A. Pietrykowski, and Richard F. Welter

IPM measurements in the Tevatron

Two Ionization Profile Monitors (IPMs) were installed in the Tevatron in 2006. The detectors are capable of resolving single bunches turn-by-turn. This paper presents recent improvements to the system hardware and its use for beam monitoring. In particular, the correction of beam size oscillations observed at injection is discussed

Near-field photocurrent nanoscopy on bare and encapsulated graphene

Opto-electronic devices utilizing graphene have already demonstrated unique capabilities, which are much more difficult to realize with conventional technologies. However, the requirements in terms of material quality and uniformity are very demanding. A major roadblock towards high-performance devices are the nanoscale variations of graphene properties, which strongly impact the macroscopic device behaviour. Here, we present and apply opto-electronic nanoscopy to measure locally both the optical and electronic properties of graphene devices. This is achieved by combining scanning near-field infrared nanoscopy with electrical device read-out, allowing infrared photocurrent mapping at length scales of tens of nanometers. We apply this technique to study the impact of edges and grain boundaries on spatial carrier density profiles and local thermoelectric properties. Moreover, we show that the technique can also be applied to encapsulated graphene/hexagonal boron nitride (h-BN) devices, where we observe strong charge build-up near the edges, and also address a device solution to this problem. The technique enables nanoscale characterization for a broad range of common graphene devices without the need of special device architectures or invasive graphene treatment

The effectiveness of psychological support interventions for those exposed to mass infectious disease outbreaks: a systematic review

Background: Mass outbreaks such as pandemics are associated with mental health problems requiring effective psychological interventions. Although several forms of psychological interventions may be advocated or used, some may lack strong evidence of efficacy and some may not have been evaluated in mass infectious disease outbreaks. This paper reports a systematic review of published studies (PROSPERO CRD:42020182094. Registered: 24.04.2020) examining the types and effectiveness of psychological support interventions for the general population and healthcare workers exposed to mass infectious disease outbreaks. Methods: A systematic review was conducted. Randomised Controlled Trials (RCT) were identified through searches of electronic databases: Medline (Ovid), Embase (Ovid), PsycINFO (EBSCO) and the Cochrane Library Database from inception to 06.05.2021 using an agreed search strategy. Studies were included if they assessed the effectiveness of interventions providing psychological support to the general population and / or healthcare workers exposed to mass infectious disease outbreaks. Studies were excluded if they focused on man-made or natural disasters or if they included armed forces, police, fire-fighters or coastguards. Results: Twenty-two RCTs were included after screening. Various psychological interventions have been used: therapist-guided therapy (n=1); online counselling (n=1); `Emotional Freedom Techniques’ (n=1); mobile phone apps (n=2); brief crisis intervention (n=1); psychological-behavioural intervention (n=1); Cognitive Behavioural Therapy (n=3); progressive muscle relaxation (n=2); emotional-based directed drawing (n=1); psycho-educational debriefing (n=1); guided imagery (n=1); Eye Movement Desensitization and Reprocessing (EMDR) (n=1); expressive writing (n=2); tailored intervention for patients with a chronic medical conditions (n=1); community health workers (n=1); self-guided psychological intervention (n=1), and a digital behaviour change intervention (n=1). Meta-analyses showed that psychological interventions had a statistically significant benefit in managing depression (Standardised Mean Difference [SMD]: -0.40; 95% Confidence Interval [CI]: -0.76 to -0.03), and anxiety (SMD: -0.72; 95% CI: -1.03 to -0.40). The effect on stress was equivocal (SMD: 0.16; 95% CI: -0.19 to 0.51). The heterogeneity of studies, studies’ high risk of bias, and the lack of available evidence means uncertainty remains. Conclusions: Further RCTs and intervention studies involving representative study populations are needed to inform the development of targeted and tailored psychological interventions for those exposed to mass infectious disease outbreaks

Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

Heterochromatin Protein 1 (HP1a) Positively Regulates Euchromatic Gene Expression through RNA Transcript Association and Interaction with hnRNPs in Drosophila

Heterochromatin Protein 1 (HP1a) is a well-known conserved protein involved in heterochromatin formation and gene silencing in different species including humans. A general model has been proposed for heterochromatin formation and epigenetic gene silencing in different species that implies an essential role for HP1a. According to the model, histone methyltransferase enzymes (HMTases) methylate the histone H3 at lysine 9 (H3K9me), creating selective binding sites for itself and the chromodomain of HP1a. This complex is thought to form a higher order chromatin state that represses gene activity. It has also been found that HP1a plays a role in telomere capping. Surprisingly, recent studies have shown that HP1a is present at many euchromatic sites along polytene chromosomes of Drosophila melanogaster, including the developmental and heat-shock-induced puffs, and that this protein can be removed from these sites by in vivo RNase treatment, thus suggesting an association of HP1a with the transcripts of many active genes. To test this suggestion, we performed an extensive screening by RIP-chip assay (RNA–immunoprecipitation on microarrays), and we found that HP1a is associated with transcripts of more than one hundred euchromatic genes. An expression analysis in HP1a mutants shows that HP1a is required for positive regulation of these genes. Cytogenetic and molecular assays show that HP1a also interacts with the well known proteins DDP1, HRB87F, and PEP, which belong to different classes of heterogeneous nuclear ribonucleoproteins (hnRNPs) involved in RNA processing. Surprisingly, we found that all these hnRNP proteins also bind heterochromatin and are dominant suppressors of position effect variegation. Together, our data show novel and unexpected functions for HP1a and hnRNPs proteins. All these proteins are in fact involved both in RNA transcript processing and in heterochromatin formation. This suggests that, in general, similar epigenetic mechanisms have a significant role on both RNA and heterochromatin metabolisms

Atmospheric isoprene measurements reveal larger-than-expected Southern Ocean emissions

Isoprene is a key trace component of the atmosphere emitted by vegetation and other organisms. It is highly reactive and can impact atmospheric composition and climate by affecting the greenhouse gases ozone and methane and secondary organic aerosol formation. Marine fluxes are poorly constrained due to the paucity of long-term measurements; this in turn limits our understanding of isoprene cycling in the ocean. Here we present the analysis of isoprene concentrations in the atmosphere measured across the Southern Ocean over 4 months in the summertime. Some of the highest concentrations ( >500 ppt) originated from the marginal ice zone in the Ross and Amundsen seas, indicating the marginal ice zone is a significant source of isoprene at high latitudes. Using the United Kingdom Earth System Model we show that current estimates of sea-to-air isoprene fluxes underestimate observed isoprene by a factor >20. A daytime source of isoprene is required to reconcile models with observations. The model presented here suggests such an increase in isoprene emissions would lead to >8% decrease in the hydroxyl radical in regions of the Southern Ocean, with implications for our understanding of atmospheric oxidation and composition in remote environments, often used as proxies for the pre-industrial atmosphere.V.F. and N.R.P.H. were supported in the analysis of the data by UKRI NERC project Southern Ocean Clouds (NE/T006366/1)

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio