Energy resolved actinometry for simultaneous measurement of atomic oxygen densities and local mean electron energies in radio-frequency driven plasmas

A diagnostic method for the simultaneous determination of atomic oxygen densities and mean electron energies is demonstrated for an atmospheric pressure radio-frequency plasma jet. The proposed method is based on phase resolved optical emission measurements of the direct and dissociative electron-impact excitation dynamics of three distinct emission lines, namely, Ar 750.4 nm, O 777.4 nm, and O 844.6 nm. The energy dependence of these lines serves as basis for analysis by taking into account two line ratios. In this frame, the method is highly adaptable with regard to pressure and gas composition. Results are benchmarked against independent numerical simulations and two-photon absorption laser-induced fluorescence experiments

Conveying Science through Art Professional Development Experience : Participant Takeaways and Recommendations for the Future

The STEM Research Center at Oregon State University was invited by Guerilla Science and Pratt Institute to evaluate the professional development experiences for two cohorts of science and art professionals. Each professional development experience consisted of a three-day workshop and field experience in August and September 2019. We used workshop observation, workshop post-surveys, field experience post surveys, and a six month follow-up survey to provide feedback about: 1) the quality and usefulness of the professional development experience for participants, and 2) effectiveness of the professional development experience for achieving the key participant outcomes of increased dispositions to and increased self-efficacy in three areas: • Creating experiences that live in the intersection of science and theatre • Creating experiences that connect to the emotions and interests of the audience • Creating experiences that communicate science in non-science settings

Evaluation of Students’ Response to Field Trips to HJ Andrews Experimental Forest

The Andrews Forest Long-Term Ecological Research (LTER) site has a long-term partnership with the University of Oregon Environmental Leadership Program (ELP), providing service-learning opportunities for undergraduate students to facilitate field trips for middle school students to the Andrews LTER site. Undergraduate students develop field trip lessons based on Andrews Forest research and creative inquiry with support of Schoolyard LTER coordinator and Andrews LTER scientist Schulze. In Middle school students hiking in the Andrews LTER 2023, six classes and 156 students total engaged in day-long field trips at the Andrews LTER site that involved forest ecology and tree identification, time to reflect on and connect with the iconic old-growth ecosystems, and discussions about environmental stewardship ideas that the students could implement both at the Andrews LTER site and in their homes. The students came from three different schools, two of them rural schools with low socio-economic status in the Lane County Educational Service District and the other a Montessori school in the Eugene area. This report shares the results from an evaluation project led by Dr. Matt Nyman and Dr. Kari O’Connell that assessed the impact of the field trips on the middle school students. The evaluation was designed to also support the middle school students’ own reflection and learning at the same time as gathering data about the impact of the experience

Authentic Research through Collaborative Learning (ARC-Learn): Undergraduate Research Experiences in Data Rich Arctic Science

This report serves the formative evaluation of ARC-Learn. The goal of this document is to support the use of evidence to inform programmatic changes and improvements for year two of the program, during which time Cohort One will complete its second year and Cohort Two will complete its first year of activities

Taking Stock of Oregon STEM Hubs: Accomplishments and Challenges

The main research goal for this study was to describe how investment into the Hubs has influenced local STEM communities; that is, how STEM Hubs have begun to create opportunities for partnerships, collaboration, connected programing, improved program development or delivery, or improved communication within and outside the STEM teaching and learning community. Based on these findings, the report provides recommendations for improvements and future investments. Ultimately, the study is aiming at establishing whether and to what degree STEM Hubs are helping to improve opportunities for effective teaching and learning for all Oregon children

The formation of atomic oxygen and hydrogen in atmospheric pressure plasmas containing humidity : picosecond two-photon absorption laser induced fluorescence and numerical simulations

Atmospheric pressure plasmas are effective sources for reactive species, making them applicable for industrial and biomedical applications. We quantify ground-state densities of key species, atomic oxygen (O) and hydrogen (H), produced from admixtures of water vapour (up to 0.5%) to the helium feed gas in a radio-frequency-driven plasma at atmospheric pressure. Absolute density measurements, using two-photon absorption laser induced fluorescence, require accurate effective excited state lifetimes. For atmospheric pressure plasmas, picosecond resolution is needed due to the rapid collisional de-excitation of excited states. These absolute O and H density measurements, at the nozzle of the plasma jet, are used to benchmark a plug-flow, 0D chemical kinetics model, for varying humidity content, to further investigate the main formation pathways of O and H. It is found that impurities can play a crucial role for the production of O at small molecular admixtures. Hence, for controllable reactive species production, purposely admixed molecules to the feed gas is recommended, as opposed to relying on ambient molecules. The controlled humidity content was also identified as an effective tailoring mechanism for the O/H ratio

Disrupting the spatio-temporal symmetry of the electron dynamics in atmospheric pressure plasmas by voltage waveform tailoring

Single frequency, geometrically symmetric Radio-Frequency (RF) driven atmospheric pressure plasmas exhibit temporally and spatially symmetric patterns of electron heating, and consequently, charged particle densities and fluxes. Using a combination of phase-resolved optical emission spectroscopy and kinetic plasma simulations, we demonstrate that tailored voltage waveforms consisting of multiple RF harmonics induce targeted disruption of these symmetries. This confines the electron heating to small regions of time and space and enables the electron energy distribution function to be tailored

Chemical kinetics and density measurements of OH in an atmospheric pressure He + O2 + H2O radiofrequency plasma

This work presents experiments and modelling of OH densities in a radio-frequency driven atmospheric-pressure plasma in a plane-parallel geometry, operated in helium with small admixtures of oxygen and water vapour (He+O2+H2O). The density of OH is measured under a wide range of conditions by absorption spectroscopy, using an ultra-stable laser-driven broad-band light source. These measurements are compared with 0D plasma chemical kinetics simulations adapted for high levels of O2 (1%). Without O2 admixture, the measured density of OH increases from 1.0×1014 to 4.0×1014 cm-3 for H2O admixtures from 0.05% to 1%. The density of atomic oxygen is about 1×1013 cm-3 and grows with humidity content. With O2 admixture, the OH density stays relatively constant, showing only a small maximum at 0.1% O2. The simulations predict that the atomic oxygen density is strongly increased by O2 addition. It reaches ~1015 cm-3 without humidity, but is limited to ~1014 cm-3 beyond 0.05% water content. The addition of O2 has a weak effect on the OH density because, while atomic oxygen becomes a dominant precursor for the formation of OH, it makes a nearly equal contribution to the loss processes of OH. The small increase in the density of OH with the addition of O2 is instead due to reaction pathways involving increased production of HO2 and O3. The simulations show that the densities of OH, O and O3 can be tailored relatively independently over a wide range of conditions. The densities of O and O3 are strongly affected by the presence of small quantities (0.05%) of water vapour, but further water addition has little effect. Therefore, a greater range and control of the reactive species mix from the plasma can be obtained by the use of well-controlled multiple gas admixtures, instead of relying on ambient air mixing

Tumor location and patient characteristics of colon and rectal adenocarcinomas in relation to survival and TNM classes

<p>Abstract</p> <p>Background</p> <p>Old age at diagnosis is associated with poor survival in colorectal cancer (CRC) for unknown reasons. Recent data show that colonoscopy is efficient in preventing left-sided cancers only. We examine the association of Tumor Node Metastasis (TNM) classes with diagnostic age and patient characteristics.</p> <p>Methods</p> <p>The Swedish Family-Cancer Database has data on TNM classes on 6,105 CRC adenocarcinoma patients. Ordinal logistic regression analysis was performed to model tumor characteristics according to age at diagnosis, tumor localization, gender, socioeconomic status, medical region and family history. The results were compared to results from survival analysis.</p> <p>Results</p> <p>The only parameters systematically associated with TNM classes were age and tumor localization. Young age at diagnosis was a risk factor for aggressive CRC, according to stage, N and M with odds ratios (ORs) ranging from 1.80 to 1.93 for diagnosis before age 50 years compared to diagnosis at 80+ years. All tumor characteristics, particularly T, were worse for colon compared to rectal tumors. Right-sided tumors showed worse characteristics for all classifiers but M. The survival analysis on patients diagnosed since 2000 showed a hazard ratio of 0.55 for diagnosis before age 50 years compared to diagnosis at over 80 years and a modestly better prognosis for left-sided compared to right-sided tumors.</p> <p>Conclusions</p> <p>The results showed systematically more aggressive tumors in young compared to old patients. The poorer survival of old patients in colon cancer was not related to the available tumor characteristics. However, these partially agreed with the limited colonoscopic success with right-sided tumors.</p