Velocity-Based Training: Current Concepts and Future Directions

Topics in Exercise Science and Kinesiology 3(1): Article 1, 2022. Velocity-based training (VBT) is a current approach to resistance training that relies on measured bar, implement, and/or athlete speed to formulate and adjust training for both long-term programming and daily training sessions. Relying on a number of available tools of varying levels of accuracy, VBT can help the strength and conditioning specialist and/or the rehabilitation professional to not only better predict strength and power over time, but also to adjust training loads in order to maximize training response in a given session. While the appeal and price points of available technology in the marketplace have made VBT more accessible than ever, a real need exists to establish the efficacy of the approach in practical settings

Seasonal budgets of reactive nitrogen species and ozone over the United States, and export fluxes to the global atmosphere

A three-dimensional, continental-scale photochemical model is used to investigate seasonal budgets of O3 and NOy species (including NOx and its oxidation products) in the boundary layer over the United States and to estimate the export of these species from the U.S. boundary layer to the global atmosphere. Model results are evaluated with year-round observations for O3, CO, and NOy species at nonurban sites. A seasonal transition from NOx to hydrocarbon-limited conditions for O3 production over the eastern United States is found to take place in the fall, with the reverse transition taking place in the spring. The mean NOx/NOy molar ratio in the U.S. boundary layer in the model ranges from 0.2 in summer to 0.6 in winter, in accord with observations, and reflecting largely the seasonal variation in the chemical lifetime of NOx. Formation of hydroxy organic nitrates during oxidation of isoprene, followed by decomposition of these nitrates to HNO3, is estimated to account for 30% of the chemical sink of NOx in the U.S. boundary layer in summer. Model results indicate that peroxyacylnitrates (PANs) are most abundant in the U.S. boundary layer in spring (25% of total NOy.), reflecting a combination of active photochemistry and low temperatures. About 20% of the NOx emitted from fossil fuel combustion in the United States in the model is exported out of the U.S. boundary layer as NOx or PANs (15% in summer, 25% in winter). This export responds less than proportionally to changes in NOx emissions in summer, but more than proportionally in winter. The annual mean export of NOx and PANs from the U.S. boundary layer is estimated to be 1.4 Tg N yr−1, representing an important source of NOx on the scale of the northern hemisphere troposphere. The eventual O3 production in the global troposphere due to the exported NOx and PANs is estimated to be twice as large, on an annual basis, as the direct export of O3 pollution from the U.S. boundary layer. Fossil fuel combustion in the United States is estimated to account for about 10% of the total source of O3 in the northern hemisphere troposphere on an annual basis

Seasonal variation of the ozone production efficiency per unit NOx at Harvard Forest, Massachusetts

Weekly values of the net O3 production efficiency (OPE), defined as the net number of O3 molecules produced per molecule of NOx (NO + NO2) consumed, are estimated from a 1990–1994 record of O3, NOx, NOy, CO, and C2H2 concentrations at Harvard Forest, Massachusetts. The OPE is inferred from the slope ΔO3/Δ(NOy − NOx) of the linear regression between O3 and NOy-NOx concentrations (NOy is the sum of NOx and its oxidation products); and alternatively from the slopes ΔO3/ΔCO and ΔO3/ΔC2H2 multiplied by regional estimates of the CO/NOx and C2H2/NOx emission ratios. The mean OPE values inferred from ΔO3/Δ(NOy − NOx) are 3–5 times higher than those inferred from ΔO3/ΔCO or ΔO3/ΔC2H2; the discrepancy may be due to the effects of HNO3 and O3 deposition and also to uncertainties in the CO/NOx and C2H2/NOx emission ratios. The relative seasonal trends of the OPE derived from ΔO3/Δ(NOy − NOx), ΔO3/ΔCO, and ΔO3/ΔC2H2 are, however, similar. Thus ΔO3/Δ(NOy − NOx) increases from about 4 mol/mol in May to 8 mol/mol in June–July, and gradually decreases back to 4 mol/mol by early October. The sharp rise of the OPE from May to June is attributed to onset of emission of the biogenic hydrocarbon isoprene. The decline from July to October is attributed to decreases in isoprene emission and in solar radiation. The O3 background at Harvard Forest, defined by the y intercept of the O3 versus NOy-NOx regression line, decreases from 40 ppbv in May to 25 ppbv in September, consistent with observations at remote sites in northern midlatitudes. The seasonal trend in the background explains why mean O3 concentrations at Harvard Forest peak in May–June even though the OPE peaks in June–July.Engineering and Applied Science

Seasonal transition from NO x - to hydrocarbon-limited conditions for ozone production over the eastern United States in September

Concentrations of O3, CO, NO, total reactive nitrogen oxides (NOy), H2O2, and HCHO were measured from September 4 to October 1, 1990, at a mountain ridge site in Shenandoah National Park, Virginia. The data show evidence for a transition from NOx-limited to hydrocarbon-limited conditions for O3 production over the course of September. The transition is diagnosed by large decreases of the H2O2/(NOy-NOx) and HCHO/NOy concentration ratios, weakening of the correlation between O3 and NOy- NOx concentrations, and decrease of the slope ΔO3/Δ(NOy-NOx). A high-O3 episode occurring in late September was associated with only 0.34 ppbv H2O2, indicative of hydrocarbon-limited conditions. A seasonal transition in photochemical regime over the eastern United States in September would be expected from theory; the production rate of odd hydrogen radicals decreases by a factor of 2 over the course of the month, due to decreasing UV radiation and humidity, allowing HNO3 production to become the dominant sink for odd hydrogen in the boundary layer and resulting in hydrocarbon-limited conditions for O3 production. Seasonal decline of isoprene emission can greatly accentuate the transition.Engineering and Applied Science

Seasonal budgets of reactive nitrogen species and ozone over the United States, and export fluxes to the global atmosphere

A three-dimensional, continental-scale photochemical model is used to investigate seasonal budgets of O3 and NOy species (including NOx and its oxidation products) in the boundary layer over the United States and to estimate the export of these species from the U.S. boundary layer to the global atmosphere. Model results are evaluated with year-round observations for O3, CO, and NOy species at nonurban sites. A seasonal transition from NOx to hydrocarbon-limited conditions for O3 production over the eastern United States is found to take place in the fall, with the reverse transition taking place in the spring. The mean NOx/NOy molar ratio in the U.S. boundary layer in the model ranges from 0.2 in summer to 0.6 in winter, in accord with observations, and reflecting largely the seasonal variation in the chemical lifetime of NOx. Formation of hydroxy organic nitrates during oxidation of isoprene, followed by decomposition of these nitrates to HNO3, is estimated to account for 30% of the chemical sink of NOx in the U.S. boundary layer in summer. Model results indicate that peroxyacylnitrates (PANs) are most abundant in the U.S. boundary layer in spring (25% of total NOy.), reflecting a combination of active photochemistry and low temperatures. About 20% of the NOx emitted from fossil fuel combustion in the United States in the model is exported out of the U.S. boundary layer as NOx or PANs (15% in summer, 25% in winter). This export responds less than proportionally to changes in NOx emissions in summer, but more than proportionally in winter. The annual mean export of NOx and PANs from the U.S. boundary layer is estimated to be 1.4 Tg N yr−1, representing an important source of NOx on the scale of the northern hemisphere troposphere. The eventual O3 production in the global troposphere due to the exported NOx and PANs is estimated to be twice as large, on an annual basis, as the direct export of O3 pollution from the U.S. boundary layer. Fossil fuel combustion in the United States is estimated to account for about 10% of the total source of O3 in the northern hemisphere troposphere on an annual basis.Engineering and Applied Science

Analysis of genetic copy number changes in cervical disease progression

<p>Abstract</p> <p>Background</p> <p>Cervical dysplasia and tumorigenesis have been linked with numerous chromosomal aberrations. The goal of this study was to evaluate 35 genomic regions associated with cervical disease and to select those which were found to have the highest frequency of aberration for use as probes in fluorescent in-situ hybridization.</p> <p>Methods</p> <p>The frequency of gains and losses using fluorescence in-situ hybridization were assessed in these 35 regions on 30 paraffin-embedded cervical biopsy specimens. Based on this assessment, 6 candidate fluorescently labeled probes (8q24, Xp22, 20q13, 3p14, 3q26, CEP15) were selected for additional testing on a set of 106 cervical biopsy specimens diagnosed as Normal, CIN1, CIN2, CIN3, and SCC. The data were analyzed on the basis of signal mean, % change of signal mean between histological categories, and % positivity.</p> <p>Results</p> <p>The study revealed that the chromosomal regions with the highest frequency of copy number gains and highest combined sensitivity and specificity in high-grade cervical disease were 8q24 and 3q26. The cytological application of these two probes was then evaluated on 118 ThinPrep™ samples diagnosed as Normal, ASCUS, LSIL, HSIL and Cancer to determine utility as a tool for less invasive screening. Using gains of either 8q24 or 3q26 as a positivity criterion yielded specificity (Normal +LSIL+ASCUS) of 81.0% and sensitivity (HSIL+Cancer) of 92.3% based on a threshold of 4 positive cells.</p> <p>Conclusions</p> <p>The application of a FISH assay comprised of chromosomal probes 8q24 and 3q26 to cervical cytology specimens confirms the positive correlation between increasing dysplasia and copy gains and shows promise as a marker in cervical disease progression.</p

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Seasonal budgets of reactive nitrogen species and ozone over the United States, and export fluxes to the global atmosphere

Abstract. A three-dimensional, continental-scale photochemical model is used to investigate seasonal budgets of 03 and NO3. species (including NOx and its oxidation products) in the boundary layer over the United States and to estimate the export of these species from the U.S. boundary layer to the global atmosphere. Model results are evaluated with year-round observations for 03, CO, and NO•, species at nonurban sites. A seasonal transition from NO, • to hydrocarbon-limited conditions for 03 production over the eastern United States is found to take place in the fall, with the reverse transition taking place in the spring. The mean NOx/NOy molar ratio in the U.S. boundary layer in the model ranges from 0.2 in summer to 0.6 in winter, in accord with observations, and reflecting largely the seasonal variation in the chemicalifetime of NOx. Formation of hydroxy organic nitrates during oxidation of isoprene, followed by decomposition of these nitrates to HNO 3, is estimated to account for 30 % of the chemical sink of NOx in the U.S. boundary layer in summer. Model results indicate that peroxyacylnitrates (PANs) are most abundant in the U.S. boundary layer in spring (25 % of total NO3.), reflecting a combination of active photochemistry and low temperatures. About 20 % of the NOx emitted from fossil fuel combustion in the United States in the model is exported out of the U.S. boundary layer as NOx o