Rolling balls or trapping ions? How students relate models to real-world phenomena in the physics laboratory

The creation and use of models in science is of great importance for knowledge production and communication. For example, toy models are often used as idealized explanatory models in physics education. Models can be a powerful tool for exploring phenomena in ways that facilitate learning. However, careful consideration of instruction and explanations needs to be considered to guide how students relate models to real-world phenomena in subject-correct ways. A design experiment was conducted to investigate how upper secondary school students can use models for learning in the physics laboratory. The intervention used in the study was a laboratory exercise developed over three phases where students worked with a mechanical Paul trap and a simulation to understand the principle behind a real Paul trap. Each phase of the study consisted of three to five laboratory sessions. The data were analyzed using thematic analysis and the learning process was understood using the theoretical framework of variation theory. From the results, it was possible to identify patterns of variation for successful lab groups and critical aspects and features students need to discern to effectively modelize the mechanical Paul trap. The findings also indicate that having students work with models can be a meaningful clarificatory process to develop a deeper understanding of the use and limitations of models in science

Breastfeeding history, pregnancy experience and risk of breast cancer.

Epidemiological evidence suggests that breastfeeding protects against breast cancer. Whether an effect of age at first breastfeeding is independent of an effect of age at first birth is unclear. We hypothesized that nausea and vomiting in pregnancy, which are associated with elevated serum oestradiol levels during pregnancy, may increase risk. Cases were 452 parous, premenopausal women, 40 years or younger, diagnosed with breast cancer in Los Angeles County from July 1983 to December 1988. Control subjects were matched to cases on age, race, parity and neighbourhood. Pregnancy and breastfeeding histories were obtained from in-person interviews. Odds of breast cancer among women who breastfed for at least 16 months relative to those among women who did not breastfeed was 0.66 [95% confidence interval (CI) 0.41-1.05]. Number of children breastfed was not associated with risk. Risk was lower in women who first breastfed at older ages. Having ever been treated for nausea or vomiting during pregnancy was associated with an increased risk, especially in women experiencing recent pregnancies (OR = 2.03, 95% CI 1.05-3.92). These results support a protective role of breastfeeding and an adverse role of nausea or vomiting during pregnancy in the development of premenopausal breast cancer, especially in the years immediately following pregnancy

Design and Overview of the Solar Cruiser Mission

Solar Cruiser is a Small Satellite Technology Demonstration Mission (TDM) of Opportunity to mature solar sail propulsion technology to enable near-term, high-priority breakthrough science missions as defined in the Solar and Space Physics Decadal Survey. Solar Cruiser will demonstrate a “sailcraft” platform with pointing control and attitude stability comparable to traditional platforms, upon which a new class of Heliophysics missions may fly instruments. It will show sailcraft operation (acceleration, navigation, station keeping, inclination change) immediately applicable to near-term missions, and show scalability of sail technologies such as the boom, membrane, deployer, reflectivity control devices for roll momentum management to enable more demanding missions, such as high inclination solar imaging. A team led by the NASA Marshall Space Flight Center is developing the Solar Cruiser with partners Ball Aerospace and Roccor (a Redwire company). Ball is responsible for procuring a Venus class microsat commercial bus from Blue Canyon Technologies, defining all necessary mission-specific modifications, and performing the Integration and Test of the Bus with the Solar Sail System to form the completed sailcraft. Ball will also procure the IRIS radio from Space Dynamics Laboratories and develop the adapter and harnessing that interfaces to the Launch Vehicle. Roccor will integrate the Solar Sail System (SSS), including the sail membrane from their Subcontractor NeXolve, the Triangular, Rollable and Collapsible (TRACTM) Boom, the LISAs (Lightweight Integrated Solar Arrays) and momentum management Reflective Control Devices (RCDs), before providing it to Ball for Integration and Test. Roccor will also build the Active Mass Translator (AMT), which moves the Sail relative to the Bus to control momentum in the pitch/yaw directions, while the RCDs provide roll control. MSFC manages the overall mission and provide the specialized solar sail attitude determination and control system (SSADCS) algorithms and software necessary to fly the sailcraft. The SSADCS software created for this mission will autonomously operate the AMT and RCDs to provide complete momentum control of the sailcraft. Bus-mounted Electric Propulsion thrusters are included to provide auxiliary momentum management, if required. Solar Cruiser will launch as a secondary payload with NASA’s Interstellar Mapping and Acceleration Probe (IMAP)in early 2025. The sailcraft will separate from the launch vehicle on a near-L1 trajectory (Sun-Earth Lagrangian Point 1; sunward of L1 along the Sun-Earth Line) and complete its primary mission in 11 months or less. During this time, Solar Cruiser will complete and fully characterize a large solar sail deployment (1,653 square meters/17,793 square feet), sail operation, station keeping in a sub-L1 halo orbit, inclination changes, and a roll demonstration. This paper provides a mission and sailcraft design overview, including objectives and planned operations of the technology demonstration mission. It presents the latest findings from technology maturation efforts, major program design reviews, and initial launch integration planning

The ABL due to a Mountain Pass and Coriolis Effect

Idealized airflow over a mountain with a pass is studied using a numerical mesoscale model with a trustful higher-order turbulence parameterization scheme. A uniformly stratified inflow of 8 m/s over mountain, 100km x 20km x 1km, yields Froude number 0.6, while Rossby number along the flow ranges from 7.6 to infinity. A pass drops the mountain top to ~ 400m locally increasing Froude number and modifying the overall wave breaking and the ABL. In the presence of the Earth rotation, f ≠ 0, which already breaks the lee-side flow symmetry, the pass induces additional variations in the ABL extending far from the mountain. Both, the rotation and the pass, alter the low-level jet structure and the specific humidity field. This mesoscale process may stretch to synoptic scale within a reasonable time, say 15-25h, only when the rotation is included. Otherwise, a somewhat similar process with f=0 might take unreasonably long time

Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow

We review modeling of astrocyte ion dynamics with a specific focus on the implications of so-called spatial potassium buffering, where excess potassium in the extracellular space (ECS) is transported away to prevent pathological neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for modeling ion dynamics in astrocytes (and brain tissue in general) is outlined and used to study such spatial buffering. We next describe how the ion dynamics of astrocytes may regulate microscopic liquid flow by osmotic effects and how such microscopic flow can be linked to whole-brain macroscopic flow. We thus include the key elements in a putative multiscale theory with astrocytes linking neural activity on a microscopic scale to macroscopic fluid flow.Comment: 27 pages, 7 figure

Recanalization of chronically occluded aortocoronary saphenous vein bypass grafts by extended infusion of urokinase: Initial results and short-term clinical follow-up

AbstractChronic occlusion of saphenous vein aortocoronary bypass grafts is a common problem. Although percutaneous transluminal angioplasty of a saphenous vein with a stenotic lesion is feasible, angioplasty alone of a totally occluded vein graft yields uniformly poor results. Patients with such occlusion are often subjected to repeat aortocoronary bypass surgery. Experience with a new technique that allows angioplasty to be performed in a totally occluded saphenous vein bypass graft is reported. This technique utilizes infusion of prolonged low dose urokinase directly into the proximal portion of the occluded graft.Forty-six consecutive patients with 47 totally occluded grafts were studied. Patients had undergone end to side saphenous vein bypass grafting 1 to 13 (mean 7) years previously. All patients presented with new or worsening angina pectoris with ST-T changes or non-Q wave acute myocardial infarction and all had a totally occluded saphenous vein bypass graft. The new technique entailed the positioning of an angiographic catheter into the stub of the occluded graft and the advancement of an infusion wire into the graft. Patients were returned to the coronary care unit, where urokinase was delivered at a dose of 100,000 to 250,000 U/h. The total dose of urokinase ranged from 0.7 to 9.8 million U over 7.5 to 77 h (mean 31). After therapy, recanalization was seen in 37 (79%) of the 47 grafts.In 20 successfully treated patients, angiography was performed 1 to 24 (mean 11) months after treatment; 13 (65%) of these grafts were patent. It is concluded that direct, extended, low dose infusion of urokinase in a totally occluded saphenous vein bypass graft offers a promising alternative to repeat bypass surgery

The Hippo signaling pathway is required for salivary gland development and its dysregulation is associated with Sjogren's-like disease

Sjogren's syndrome (SS) is a complex autoimmune disease that primarily affects salivary and lacrimal glands and is associated with high morbidity. Although the prevailing dogma is that immune system pathology drives SS, increasing evidence points to structural defects, including defective E-cadherin adhesion, to be involved in its etiology. We have shown that E-cadherin plays pivotal roles in the development of the mouse salivary submandibular gland (SMG) by organizing apical-basal polarity in acinar and ductal progenitors and by signaling survival for differentiating duct cells. Recently, E-cadherin junctions have been shown to interact with effectors of the Hippo signaling pathway, a core pathway regulating organ size, cell proliferation and differentiation. We now show that Hippo signaling is required for SMG branching morphogenesis and is involved in the pathophysiology of SS. During SMG development, a Hippo pathway effector, TAZ, becomes increasingly phosphorylated and associated with E-cadherin and α-catenin, consistent with the activation of Hippo signaling. Inhibition of Lats2, an upstream kinase that promotes TAZ phosphorylation, results in dysmorphogenesis of the SMG and impaired duct formation. SMGs from NOD mice, a mouse model for SS, phenocopy the Lats2-inhibited SMGs and exhibit a reduction in E-cadherin junctional components, including TAZ. Importantly, labial specimens from human SS patients display mislocalization of TAZ from junctional regions to the nucleus, coincident with accumulation of extracellular matrix components, fibronectin and CTGF, known downstream targets of TAZ. Our studies show that Hippo signaling plays a crucial role in SMG branching morphogenesis and provide evidence that defects in this pathway are associated with SS in humans

Nanoscale temperature measurements using non-equilibrium Brownian dynamics of a levitated nanosphere

Einstein realised that the fluctuations of a Brownian particle can be used to ascertain properties of its environment. A large number of experiments have since exploited the Brownian motion of colloidal particles for studies of dissipative processes, providing insight into soft matter physics, and leading to applications from energy harvesting to medical imaging. Here we use optically levitated nanospheres that are heated to investigate the non-equilibrium properties of the gas surrounding them. Analysing the sphere's Brownian motion allows us to determine the temperature of the centre-of-mass motion of the sphere, its surface temperature and the heated gas temperature in two spatial dimensions. We observe asymmetric heating of the sphere and gas, with temperatures reaching the melting point of the material. This method offers new opportunities for accurate temperature measurements with spatial resolution on the nanoscale, and a new means for testing non-equilibrium thermodynamicsComment: 5 pages, 4 figures, supplementary material available upon reques

Automated inter-rater reliability assessment and electronic data collection in a multi-center breast cancer study

<p>Abstract</p> <p>Background</p> <p>The choice between paper data collection methods and electronic data collection (EDC) methods has become a key question for clinical researchers. There remains a need to examine potential benefits, efficiencies, and innovations associated with an EDC system in a multi-center medical record review study.</p> <p>Methods</p> <p>A computer-based automated menu-driven system with 658 data fields was developed for a cohort study of women aged 65 years or older, diagnosed with invasive histologically confirmed primary breast cancer (N = 1859), at 6 Cancer Research Network sites. Medical record review with direct data entry into the EDC system was implemented. An inter-rater and intra-rater reliability (IRR) system was developed using a modified version of the EDC.</p> <p>Results</p> <p>Automation of EDC accelerated the flow of study information and resulted in an efficient data collection process. Data collection time was reduced by approximately four months compared to the project schedule and funded time available for manuscript preparation increased by 12 months. In addition, an innovative modified version of the EDC permitted an automated evaluation of inter-rater and intra-rater reliability across six data collection sites.</p> <p>Conclusion</p> <p>Automated EDC is a powerful tool for research efficiency and innovation, especially when multiple data collection sites are involved.</p