Mass Measurement Using Energy Spectra in Three-body Decays

In previous works we have demonstrated how the energy distribution of massless decay products in two body decays can be used to measure the mass of decaying particles. In this work we show how such results can be generalized to the case of multi-body decays. The key ideas that allow us to deal with multi-body final states are an extension of our previous results to the case of massive decay products and the factorization of the multi-body phase space. The mass measurement strategy that we propose is distinct from alternative methods because it does not require an accurate reconstruction of the entire event, as it does not involve, for instance, the missing transverse momentum, but rather requires measuring only the visible decay products of the decay of interest. To demonstrate the general strategy, we study a supersymmetric model wherein pair-produced gluinos each decay to a stable neutralino and a bottom quark-antiquark pair via an off-shell bottom squark. The combinatorial background stemming from the indistinguishable visible final states on both decay sides can be treated by an "event mixing" technique, the performance of which is discussed in detail. Taking into account dominant backgrounds, we are able to show that the mass of the gluino and, in favorable cases, that of the neutralino can be determined by this mass measurement strategy.Comment: 42 pages, 12 figures, Journal-submitted versio

Effects of thinking-aloud pair problem solving on the troubleshooting performance of undergraduate students in a power technology course

A randomized post-test-only experimental design with a counter-balanced internal replication was used to determine the effects of thinking-aloud pair problem solving (TAPPS) on the troubleshooting performance of college students in a power technology course. The experimental results were stable across two troubleshooting tasks. Students who participated in the pair problem solving groups were significantly more successful (p ≤ .05) at troubleshooting engine faults than were students in the control groups. Among students who successfully completed the troubleshooting tasks across both groups, there were no significant differences in time required for completion. These findings indicate that the use of pair problem solving may be an important step in the development of metacognitive skills among students in technological troubleshootin

PTO performance and NOx emissions with D2, B20, and B100 fuels in a John Deere 3203 compact tractor

Tests were conducted in fall 2006 on a John Deere 3203 diesel tractor to determine differences in specific fuel consumption, power take-off (PTO) torque, PTO power, thermal efficiency, and oxides of nitrogen (NOx) emissions between No. 2 diesel (D2), 20% biodiesel (B20), and 100% biodiesel (B100). Four 1-hour tests were conducted on each fuel. The results indicated no statistically significant differences (p≤.05) between D2 or B20 on any variable of interest. However, B100 resulted in significantly (p≤.05) increased, specific fuel consumption and thermal efficiency and decreased PTO torque and PTO power over both D2 and B20. These data suggest that farmers could switch from D2 to B20 without any performance losses, but a switch to B100 would result in the use of more fuel and a loss of power and torque

EVLA observations of a proto-cluster of molecular gas rich galaxies at z = 4.05

We present observations of the molecular gas in the GN20 proto-cluster of galaxies at $z =4.05$ using the Expanded Very Large Array (EVLA). This group of galaxies is the ideal laboratory for studying the formation of massive galaxies via luminous, gas-rich starbursts within 1.6 Gyr of the Big Bang. We detect three galaxies in the proto-cluster in CO 2-1 emission, with gas masses (H$_2$) between $10^{10}$ and $10^{11} \times (\alpha/0.8)$ M$_\odot$. The emission from the brightest source, GN20, is resolved with a size $\sim 2"$, and has a clear north-south velocity gradient, possibly indicating ordered rotation. The gas mass in GN20 is comparable to the stellar mass ($1.3\times 10^{11} \times (\alpha/0.8)$ M$_\odot$ and $2.3\times 10^{11}$ M$_\odot$, respectively), and the sum of gas plus stellar mass is comparable to the dynamical mass of the system ($\sim 3.4\times 10^{11} [sin(i)/sin(45^o)]^{-2}$ M$_\odot$), within a 5kpc radius. There is also evidence for a tidal tail extending another $2"$ north of the galaxy with a narrow velocity dispersion. GN20 may be a massive, gas rich disk that is gravitationally disturbed, but not completely disrupted. There is one Lyman-break galaxy (BD29079) in the GN20 proto-cluster with an optical spectroscopic redshift within our search volume, and we set a 3$\sigma$ limit to the molecular gas mass of this galaxy of $1.1\times 10^{10} \times (\alpha/0.8)$ M$_\odot$.Comment: AAStex format, 4 figures; prepared for the ApJ Letters EVLA special issu

Probing the role of excited states in ionization of acetylene

Ionization of acetylene by linearly-polarized, vacuum ultraviolet (VUV) laser pulses is modelled using time-dependent density functional theory. Several laser wavelengths are considered including one that produces direct ionization to the first excited cationic state while another excites the molecules to a Rydberg series incorporating an autoionizing state. We show that for the wavelengths and intensities considered, ionization is greatest whenever the molecule is aligned along the laser polarization direction. By considering high harmonic generation we show that populating excited states can lead to a large enhancement in the harmonic yield. Lastly, angularly-resolved photoelectron spectra are calculated which show how the energy profile of the emitted electrons significantly changes in the presence of these excited states

Main Body Aerodynamics

Our senior design project entails designing, analyzing the front upper aerodynamic nose for the Formula SAE at VCU’s race team. Currently there are no provisions on the chassis to provide relief for parasitic loss of speed & efficiency due to drag. Since Formula SAE is focused on building a engineered, safe, and efficient vehicle our aerodynamic design will help with handling, downforce, and fuel economy all while reducing drag. Our Aerodynamic design will play a key role not only in how the Formula car is perceived aesthetically, but our calculations will be a large determining factor in the cars overall final performance. Our group started the project by initially consulting texts to better grasp knowledge on aerodynamic systems and their role in contributing to an efficient vehicle. With our research we were able to come up with numerous design considerations and gained more insight into how aerodynamics systems are analyzed. Once we conducted our background research we made some rough sketches of what we wanted the aero to look like. With these 2-D drawings we gathered equations necessary to calculate the drag coefficient and conducted a theoretical analysis of our 2D version to compare to our 3D calculations that will be solved using ANSYS. Our research showed us that the tear drop is generally thought to be the best shape so we based our drawings off of that consideration. Once we had a rough sketch, we started modeling the aero using an existing drawing of the chassis in Solidworks. At this stage we created a few different types of models so that in the future we would be able to quickly differentiate the aspects of our drawings that reduced the coefficient of drag. Moving forward with the project we expect to encounter many other problems associated with our design and analysis. However our aim is to narrow down our 3D designs and consider the aspects that reduced drag. This will allow us to come up with a further refined result. Once our data is analyzed we can conduct a comparison of our initial designs versus our final product and gain understanding as to what is needed to quickly and efficiently design aero in the future. This project will entail engineering through hand calculations, designing for real world problems using surface models in solidworks, and performing an analysis using the finite element method & computational fluid dynamics.https://scholarscompass.vcu.edu/capstone/1066/thumbnail.jp

Effect of exercise-induced muscle damage on vascular function and skeletal muscle microvascular deoxygenation

Citation: Caldwell, J. T., Wardlow, G. C., Branch, P. A., Ramos, M., Black, C. D., & Ade, C. J. (2016). Effect of exercise-induced muscle damage on vascular function and skeletal muscle microvascular deoxygenation. Physiological Reports, 4(22), 12. doi:10.14814/phy2.13032This paper investigated the effects of unaccustomed eccentric exercise-induced muscle damage (EIMD) on macro-and microvascular function. We tested the hypotheses that resting local and systemic endothelial-dependent flow-mediated dilation (FMD) and microvascular reactivity would decrease, (V) over dotO(2max) would be altered, and that during ramp exercise, peripheral O-2 extraction, evaluated via near-infrared-derived spectroscopy (NIRS) derived deoxygenated hemoglobin + myoglobin ([HHb]), would be distorted following EIMD. In 13 participants, measurements were performed prior to (Pre) and 48 h after a bout of knee extensor eccentric exercise designed to elicit localized muscle damage (Post). Flow-mediated dilation and postocclusive reactive hyperemic responses measured in the superficial femoral artery served as a measurement of local vascular function relative to the damaged tissue, while the brachial artery served as an index of nonlocal, systemic, vascular function. During ramp-incremental exercise on a cycle ergometer, [HHb] and tissue saturation (TSI%) in the m. vastus lateralis were measured. Superficial femoral artery FMD significantly decreased following EIMD (pre 6.75 +/- 3.89%; post 4.01 +/- 2.90%; P 0.05). At each progressive increase in workload (i.e., 0-100% peak), the [HHb] and TOI% responses were similar pre-and 48 h post-EIMD (P > 0.05). Additionally, (V) over dotO(2max) was similar at pre-(3.0 +/- 0.67 L min(-1)) to 48 h post (2.96 +/- 0.60 L min(-1))-EIMD (P > 0.05). Results suggest that moderate eccentric muscle damage leads to impaired local, but not systemic, macrovascular dysfunction

HerMES: A Statistical Measurement of the Redshift Distribution of Herschel-SPIRE Sources Using the Cross-correlation Technique

The wide-area imaging surveys with the Herschel Space Observatory at submillimeter (sub-mm) wavelengths have now resulted in catalogs of the order of one-hundred-thousand dusty, starburst galaxies. These galaxies capture an important phase of galaxy formation and evolution, but, unfortunately, the redshift distribution of these galaxies, N(z), is still mostly uncertain due to limitations associated with counterpart identification at optical wavelengths and spectroscopic follow-up. We make a statistical estimate of N(z) using a clustering analysis of sub-mm galaxies detected at each of 250, 350 and 500 μm from the Herschel Multi-tiered Extragalactic Survey centered on the Boötes field. We cross-correlate Herschel galaxies against galaxy samples at optical and near-IR wavelengths from the Sloan Digital Sky Survey, the NOAO Deep Wide Field Survey, and the Spitzer Deep Wide Field Survey. We create optical and near-IR galaxy samples based on their photometric or spectroscopic redshift distributions and test the accuracy of those redshift distributions with similar galaxy samples defined with catalogs from the Cosmological Evolution Survey (COSMOS), which has superior spectroscopic coverage. We model the clustering auto- and cross-correlations of Herschel and optical/IR galaxy samples to estimate N(z) and clustering bias factors. The S_(350) > 20 mJy galaxies have a bias factor varying with redshift as b(z) = 1.0^(+1.0)_(–0.5)(1 + z)^1.2^(+0.3)_(–0.7). This bias and the redshift dependence is broadly in agreement with galaxies that occupy dark matter halos of mass in the range of 1012 to 10^(13) M_☉. We find that galaxy selections in all three Spectral and Photometric Imaging Receiver (SPIRE) bands share a similar average redshift, with = 1.8 ± 0.2 for 250 μm selected samples, and = 1.9 ± 0.2 for both 350 and 500 μm samples, while their distributions behave differently. For 250 μm selected galaxies we find the a larger number of sources with z ≤ 1 when compared with the subsequent two SPIRE bands, with 350 and 500 μm selected SPIRE samples having peaks in N(z) at progressively higher redshifts. We compare our clustering-based N(z) results to sub-mm galaxy model predictions in the literature, and with an estimate of N(z) using a stacking analysis of COSMOS 24 μm detections

Using MODIS to detect cropping frequency variation in mechanized agriculture in Amazonia.

Policy makers concerned with managing rapidly developing agriculture on the Amazon frontier currently have no Basin-wide spatial and temporal information on exactly when and how soubean and other mechanized annual cropping have developed in the region. To address this, we present a reliminary evaluation of the use of moderate resolution Imaging Spectroradiometer (MODIS) 250 m vegetation index (VI) time-series data to detect croppping frequency in two municipalities, Vilhena, Rondônia, and Santarém, Pará