Distinguishing Harmonic Behavior Of Longitudinal Resonant Combustion In A Variable Geometry Model Rocket Combustor

Throughout the study of high frequency combustion instability in a single element Continuously Variable Resonance Combustor (CVRC), the excitation of the fundamental longitudinal mode is closely followed by the excitation of higher harmonic modes. In an attempt to establish a heuristic relationship between the appearances of the fundamental mode and its harmonics, several unstable fixed geometry and variable geometry tests from the CVRC are analyzed through traditional Fourier-based methods and alternative signal processing methods such as wavelet analysis and Instantaneous Frequency (IF) Analysis from PC Signal Analysis. Early results led to the conclusion that traditional Fourier-based analysis provides believable and consistent results for the first three modes. However, Fourier analysis is sensitive to effects from non-sinusoidal waveforms. Further work using manufactured signals with both sinusoidal and steepfronted waveforms established that it is unclear which parts of the calculated harmonic signals are data artifacts and which are true signal. Supplementary assessment of IF Analysis and the traditional Fourier-based analysis explored the applicability of each method, the inherent data artifacts, and distinguishing behavior between the experimental data and those data artifacts. The results obtained from the IF Analysis provide good agreement with the traditional Fourier-based analysis, though one uses FIR filters and the other uses IIR filters. The validity of the results is sensitive to the settings chosen for these filters. It is shown that harmonic modal content exists in the CVRC, but it is also shown that the current results include indistinguishable Fourier artifacts. Both methods are sensitive to the sinusoidal assumption and cannot correctly interpret steep-fronted waveforms. This supplementary assessment has shown that IF Analysis is no worse than traditional Fourier-based analysis, but it fails to provide additional useful information. Qualitative modal behavior is distinguishable from the experimental data, including the sequential excitation of modes and the increasing growth rate with increasing mode number. However, quantitative results such as the growth rate or modal amplitude have been shown to be unreliable. The acoustic wave assumption is supported by the standing wave behavior observed in CVRC, specifically the decreasing amplitude of a mode near its equivalent pressure node location and the relative phase between modal signals on either side of its equivalent pressure node. However, the shock-like wave assumption has not been completely disproved. Additional work needs to be done with wavelet analysis using steep-fronted wavelet shapes to assess the potential steep-fronted waveform

IDENTIFYING AND PREDICTING INTENTION TO QUIT USING JUUL AMONG EMERGING ADULTS

Objectives: (1) Describe intention to quit, (2) identify relationships between sociodemographic factors or social influences and intention to quit, (3) explore if Theory of Planned Behavior-informed constructs can predict intention to quit as well as identify which construct best predicts, and (4) discover if descriptive norms strengthen a predictive model of intention to quit among emerging adults currently using Juul. Participants: Full-time, first-year students currently using Juul, an e-cigarette product, at a large university in the southeastern United States (N = 182). Methods: A November 2018 online survey assessed sociodemographic characteristics, social influences, patterns of use, quit intention, and attitudes, norms, and perceived behavioral control toward Juul. Results: A quarter of participants reported current use, with nearly half intending to quit within six months. Recent quit attempts was the only factor related to intention. Two models were created that successfully predicted intention to quit, but only perceived behavioral control was individually significant as a predictor. Conclusions: Cessation-focused campaigns and interventions are needed on college campuses and could be less tailored than prevention to save time and money

Proper Motions of PSRs B1757-24 and B1951+32: Implications for Ages and Associations

Over the last decade, considerable effort has been made to measure the proper motions of the pulsars B1757-24 and B1951+32 in order to establish or refute associations with nearby supernova remnants and to understand better the complicated geometries of their surrounding nebulae. We present proper motion measurements of both pulsars with the Very Large Array, increasing the time baselines of the measurements from 3.9 yr to 6.5 yr and from 12.0 yr to 14.5 yr, respectively, compared to previous observations. We confirm the non-detection of proper motion of PSR B1757-24, and our measurement of (mu_a, mu_d) = (-11 +/- 9, -1 +/- 15) mas yr^{-1} confirms that the association of PSR B1757-24 with SNR G5.4-1.2 is unlikely for the pulsar characteristic age of 15.5 kyr, although an association can not be excluded for a significantly larger age. For PSR B1951+32, we measure a proper motion of (mu_a, mu_d) = (-28.8 +/- 0.9, -14.7 +/- 0.9) mas yr^{-1}, reducing the uncertainty in the proper motion by a factor of two compared to previous results. After correcting to the local standard of rest, the proper motion indicates a kinetic age of ~51 kyr for the pulsar, assuming it was born near the geometric center of the supernova remnant. The radio-bright arc of emission along the pulsar proper motion vector shows time-variable structure, but moves with the pulsar at an approximately constant separation ~2.5", lending weight to its interpretation as a shock structure driven by the pulsar.Comment: LaTeX file uses emulateapj.cls; 7 pages, 4 figures, to be published ApJ February 10, 2008, v674 p271-278. Revision reflects journal formatting; there are no substantial revision

The Role of Seed Bank and Germination Dynamics in the Restoration of a Tidal Freshwater Marsh in the Sacramento–San Joaquin Delta

Liberty Island, California, is a historical freshwater tidal wetland that was converted to agricultural fields in the early 1900s. Liberty Island functioned as farmland until an accidental levee break flooded the area in 1997, inadvertently restoring tidal marsh hydrology. Since then, wetland vegetation has naturally recolonized part of the site. We conducted a seed bank assay at the site and found that despite a lack of germination or seedling recruitment at the site, the seed bank contained a diverse plant community, indicating that the site’s continuous flooding was likely suppressing germination. Additionally, the frequency of germinating seeds in the seed bank did not represent the dominant adult plant community. We conducted a cold stratification study to determine if this observed disparity could be explained by seed germination dynamics, and whether germination could be enhanced using a pre-germination cold exposure, particularly for species of concern for wetland restoration. The cold stratification study showed that longer durations of pre-germination cold enhanced germination in Schoenoplectus acutus, but reduced germination in Schoenoplectus californicus, and had no effect on Typha latifolia. Overall, germination of S. californicus and S. acutus was much lower than T. latifolia. Our findings suggest that seeding may not be an effective restoration technique for Schoenoplectus spp., and, to improve restoration techniques, further study is needed to more comprehensively understand the reproduction ecology of important marsh species

Orthogonal signed-distance coordinates and vector calculus near evolving curves and surfaces

We provide an elementary derivation of an orthogonal coordinate system for boundary layers around evolving smooth surfaces and curves based on the signed-distance function. We go beyond previous works on the signed-distance function and collate useful vector calculus identities for these coordinates. These results and provided code enable consistent accounting of geometric effects in the derivation of boundary layer asymptotics for a wide range of physical systems.Comment: 24 pages, 3 figures, Mathematica code available at https://github.com/ericwhester/signed-distance-cod

Quantitation of intracellular NAD(P)H can monitor an imbalance of DNA single strand break repair in base excision repair deficient cells in real time

DNA single strand breaks (SSBs) are one of the most frequent DNA lesions in genomic DNA generated either by oxidative stress or during the base excision repair pathways. Here we established a new real-time assay to assess an imbalance of DNA SSB repair by indirectly measuring PARP-1 activation through the depletion of intracellular NAD(P)H. A water-soluble tetrazolium salt is used to monitor the amount of NAD(P)H in living cells through its reduction to a yellow colored water-soluble formazan dye. While this assay is not a direct method, it does not require DNA extraction or alkaline treatment, both of which could potentially cause an artifactual induction of SSBs. In addition, it takes only 4 h and requires less than a half million cells to perform this measurement. Using this assay, we demonstrated that the dose- and time-dependent depletion of NAD(P)H in XRCC1-deficient CHO cells exposed to methyl methanesulfonate. This decrease was almost completely blocked by a PARP inhibitor. Furthermore, methyl methanesulfonate reduced NAD(P)H in PARP-1+/+cells, whereas PARP-1¿/¿ cells were more resistant to the decrease in NAD(P)H. These results indicate that the analysis of intracellular NAD(P)H level using water-soluble tetrazolium salt can assess an imbalance of SSB repair in living cells in real time

Same-day Discharge After Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Series of 808 Cases

BACKGROUND: The versatility of transforaminal lumbar interbody fusion (TLIF) allows fusion at any level along with any necessary canal decompression. Unilateral TLIF with a single interbody device and unilateral pedicle fixation has proven effective, and minimally invasive techniques have shortened hospital stays. Reasonable questions have been raised, though, about whether same-day discharge is feasible and safe after TLIF surgery. QUESTIONS/PURPOSES: We determined, in a high-volume spine practice, what proportion of patients having one- or two-level minimally invasive unilateral TLIF go home on the day of surgery or stay longer and compared the two groups in terms of outcome scores (VAS scores for back and leg pain, Waddell-Main Disability Index), complications, and hospital readmissions. METHODS: We retrospectively studied all 1005 patients who underwent 1114 minimally invasive unilateral TLIF procedures by one surgeon between March 18, 2003, and April 12, 2013. For the first 43 months, Medicare patients (65 years or older) were not offered same-day discharge. All other patients were offered the chance to be discharged home on the same day if they felt well enough. Followup data were for 3 months. VAS scores for back and leg pain and Waddell-Main Disability Index were recorded in a prospectively maintained database and readmissions were ascertained by chart review. Data were available on 100% of discharges, 95% of preoperative outcome scores, and 81% of outcome scores out to 3 months. RESULTS: Of the 1114 procedures, 808 went home the day of surgery, resulting in a 73% same-day discharge rate. Mean differences in outcome scores from preoperatively to 3 months were similar between groups, except for a difference in VAS lower leg pain in hospital stay patients, which was of borderline statistical and unlikely clinical significance (3.3 versus 2.7, p = 0.05). The only important differences between groups were slightly more medical complications and readmissions for patients 65 years and older who stayed in hospital overnight (3.9% versus 0%, p < 0.01); however, some self-selection bias toward staying overnight among patients with higher self-rated disability and pain scores likely accounted for this difference. CONCLUSIONS: Surgeons experienced in minimally invasive spine surgery can consider same-day discharge for patients having minimally invasive unilateral TLIF procedures. LEVEL OF EVIDENCE: Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence

Student Voice: The Beacon in Our Journey to School Improvement

Is it possible to reduce the achievement gap simply by implementing effective instructional practices? Francis Scott Key Middle School in Montgomery County Maryland learned that building the cultural proficiency of teachers had to move beyond strategies. Francis Scott Key’s Student Voice Project helped both teachers and students transform their thinking about instruction, communication, and school improvement