AZTEC SURVEY OF THE CENTRAL MOLECULAR ZONE: MODELING DUST SEDS WITH HIERARCHICAL BAYESIAN ANALYSIS

In this dissertation, we present a study based on the AzTEC/Large Millimeter Telescope (LMT) survey of dust continuum at 1.1mm on the central 200 parsecs (The Central Molecular Zone (CMZ)) of our Galaxy. Owing to its unusually high gas density and turbulence, strong magnetic field, and high cosmic ray flux, the CMZ represents an initial condition for star-formation typical of starburst galaxies in the distant universe. In order to understand dust properties in such an extreme environment. We perform a joint SED analysis of existing dust continuum surveys on the CMZ, from a wavelength of 160 μm to 1.1 mm. This analysis follows a Bayesian model incorporating the knowledge of Point Spread Functions (PSFs) in different maps, which enables full utilization of our high resolution (10.5”) map at 1.1 mm and achievement of unprecedented detailed information on the spatial distribution of dusty gas across the CMZ. There is a remarkable trend of increasing dust spectral index, from 2.0 − 2.5, toward dense peaks in the CMZ, indicating a deficiency of large grains or a fundamental change in dust optical properties. The latter scenario leads to an underestimate of dust temperature when using the conventional model. Depending on how the optical properties of dust deviate from the conventional model, dust temperature could be underestimated by 10−50%, and potentially even higher. We further develop new methods to explore the temperature and density structures of the CMZ molecular clouds, based on Hierarchical Bayesian Analysis. We propose a phenomenological model for line-of-sight temperature decomposition and show that the temperature profile of dust evolves with orbital phases, in agreement with previous studies on gas temperature. Finally, we show that at the 0.5-parsec spatial resolution achieved by our study, the Probability Density Function of the Column Densities (N-PDF) provides a robust indicator of the density structure

Probing Outflows in z= 1~2 Galaxies through FeII/FeII* Multiplets

We report on a study of the 2300-2600\AA FeII/FeII* multiplets in the rest-UV spectra of star-forming galaxies at 1.0<z<2.6 as probes of galactic-scale outflows. We extracted a mass-limited sample of 97 galaxies at z~1.0-2.6 from ultra-deep spectra obtained during the GMASS spetroscopic survey in the GOODS South field with the VLT and FORS2. We obtain robust measures of the rest equivalent width of the FeII absorption lines down to a limit of W_r>1.5 \AA and of the FeII* emission lines to W_r>0.5 \AA. Whenever we can measure the systemic redshift of the galaxies from the [OII] emission line, we find that both the FeII and MgII absorption lines are blueshifted, indicative that both species trace gaseous outflows. We also find, however, that the FeII gas has generally lower outflow velocity relative to that of MgII. We investigate the variation of FeII line profiles as a function of the radiative transfer properties of the lines, and find that transitions with higher oscillator strengths are more blueshifted in terms of both line centroids and line wings. We discuss the possibility that FeII lines are suppressed by stellar absorptions. The lower velocities of the FeII lines relative to the MgII doublet, as well as the absence of spatially extended FeII* emission in 2D stacked spectra, suggest that most clouds responsible for the FeII absorption lie close (3~4 kpc) to the disks of galaxies. We show that the FeII/FeII* multiplets offer unique probes of the kinematic structure of galactic outflows.Comment: 53 pages, 22 Figures, accepted for publication in ApJ, revised according to referee comment

An Updated Quantification Method for Liquid Refrigerant Distribution in Microchannel Evaporators Using Infrared Thermography

Refrigerant distribution in the parallel tubes of a microchannel evaporator significantly affects its heat transfer performance, which can further affect the coefficient of performance of the whole air-conditioning or refrigeration system. This paper proposes an easy-to-implement quantification method using infrared thermography for the liquid refrigerant distribution in microchannel evaporators to update the original method developed by Li and Hrnjak (2015). Before the detailed discussion of the new quantification method, the effect of surface emissivity on the infrared thermography is investigated, and the calibration process of the infrared thermography is presented for a microchannel heat exchanger sample. Then, the updated quantification method is introduced in detail. The ε-NTU approach is clarified for the formula derivation. A new mathematical method is introduced for the determination of the transition between the two-phase region and the single-phase region. A facility with pump-driven two-phase refrigerant R134a has been built to demonstrate the updated quantification method for the liquid refrigerant distribution in a microchannel evaporator with vertical parallel tubes. The tests have been run at the conditions of 41.7 g/s refrigerant flow rate and 5 oC evaporation temperature with the evaporator inlet vapor quality of 0.15 and 0.25, respectively. The infrared images and the reduced liquid refrigerant mass flow rate distributions are presented to demonstrate the effectiveness of the updated quantification method

Flow Boiling Heat Transfer And Pressure Drop Characteristics Of R1234yf In A Dimpled Flat Duct

Among various heat transfer enhancement technologies, the dimpled surface, which is inspired by the resistance reduction characteristics of the specific concaves on golf balls, has the potential to improve heat transfer with a relatively low pressure-drop penalty. More and more applications of dimpled surfaces in heat exchangers have shown up in industries. However, the lack of experimental data, especially the heat transfer and pressure drop data for liquidand-vapor two-phase flow, inside the dimpled flow channels prevents the good design of the dimpled heat exchangers. In this study, a facility has been designed and built to investigate the heat transfer and pressure drop of flow-boiling R1234yf in a dimpled flat duct. The details of the facility, especially the test section, are presented. A microscope is used to measure the geometrical dimensions of the dimpled flat tube. The heat loss is tested and the heat balance is -2 -1 checked before the experiments. The experiments are performed at mass flux from 100 to 200 kg m s , heat flux of 5 kW m-2, saturation temperature of 15 oC, and vapor quality from 0.1 to 0.95. The experimental results are presented and discussed in detail

Cystatin C Identifies Patients with Stable Chronic Heart Failure at Increased Risk for Adverse Cardiovascular Events

Background—Renal function is a strong predictor of adverse events in heart failure. Current renal function measures are imperfect, and cystatin C (CysC) is promoted as a better marker of glomerular filtration rate. This study compares the prognostic use of CysC and derived glomerular filtration rate estimates with other measures of renal function in patients with chronic heart failure. Methods and Results—We measured serum CysC levels in 823 patients with heart failure undergoing coronary angiography with follow-up of major adverse cardiovascular events (death, myocardial infarction, stroke). CysC levels strongly correlated with creatinine (r=0.73), blood urea nitrogen (r=0.70), and estimated glomerular filtration rate by the 4-variable modification of diet in renal disease equation (r=−0.62) (all P\u3c0.001). However, the correlation was lower in estimated glomerular filtration rate ≥60 mL/min per 1.73 m2. CysC-based measures significantly improved areas under the receiver operating characteristic curve for the prediction of major adverse cardiovascular events, especially in estimated glomerular filtration rate ≥60 mL/min per 1.73 m2 (P\u3c0.01). Net reclassification improvement was 22.2% (P\u3c0.001) in this group. CysC remained an independent predictor of major adverse cardiovascular events (P\u3c0.001) after adjustment for traditional risk factors and brain natriuretic peptide. Conclusions—CysC is an independent predictor of adverse events in chronic heart failure. It adds prognostic value to creatinine, particularly in patients with preserved renal function

Cystatin C Identifies Patients with Stable Chronic Heart Failure at Increased Risk for Adverse Cardiovascular Events

Background—Renal function is a strong predictor of adverse events in heart failure. Current renal function measures are imperfect, and cystatin C (CysC) is promoted as a better marker of glomerular filtration rate. This study compares the prognostic use of CysC and derived glomerular filtration rate estimates with other measures of renal function in patients with chronic heart failure. Methods and Results—We measured serum CysC levels in 823 patients with heart failure undergoing coronary angiography with follow-up of major adverse cardiovascular events (death, myocardial infarction, stroke). CysC levels strongly correlated with creatinine (r=0.73), blood urea nitrogen (r=0.70), and estimated glomerular filtration rate by the 4-variable modification of diet in renal disease equation (r=−0.62) (all P\u3c0.001). However, the correlation was lower in estimated glomerular filtration rate ≥60 mL/min per 1.73 m2. CysC-based measures significantly improved areas under the receiver operating characteristic curve for the prediction of major adverse cardiovascular events, especially in estimated glomerular filtration rate ≥60 mL/min per 1.73 m2 (P\u3c0.01). Net reclassification improvement was 22.2% (P\u3c0.001) in this group. CysC remained an independent predictor of major adverse cardiovascular events (P\u3c0.001) after adjustment for traditional risk factors and brain natriuretic peptide. Conclusions—CysC is an independent predictor of adverse events in chronic heart failure. It adds prognostic value to creatinine, particularly in patients with preserved renal function

Usefulness of Cardiac Biomarker Score for Risk Stratification in Stable Patients Undergoing Elective Cardiac Evaluation Across Glycemic Status

Several clinically available cardiac biomarkers have established their prognostic value in patients with acute coronary syndromes. However, their relative prognostic significance in stable subjects has not been prospectively validated, either individually or in combination. The aim of this study was to evaluate the extent to which B-type natriuretic peptide, myeloperoxidase, and high-sensitivity C-reactive protein alone or together could be prognostic biomarkers in 3,635 consecutive stable patients without acute coronary syndrome who underwent elective diagnostic coronary angiography. After adjusting for traditional risk factors and renal function, each of the markers monitored was a significant predictor of incident major adverse cardiovascular events (death, nonfatal myocardial infarction, and stroke) over 3 years. A cardiac biomarker score based on the sum total of “positive” biomarkers provided independent prediction of future risk for incident major adverse cardiovascular events at 3 years (hazard ratio [HR] 7.61, 95% confidence interval [CI] 4.98 to 11.65, p \u3c0.001), even after adjusted for traditional risk factors (HR 6.11, 95% CI 3.98 to 9.38, p \u3c0.001). A positive cardiac biomarker score remained a strong and independent predictor of 3-year risk for major adverse cardiovascular events among those with normal glycemic control (HR 4.24, 95% CI 1.96 to 9.18, p \u3c0.001), those with prediabetes (HR 7.62, 95% CI 3.87 to 15.01, p \u3c0.001), and those with diabetes (HR 5.61, 95% CI 2.55 to 12.33, p \u3c0.001), as well as within subjects without significant angiographic evidence of coronary artery disease (HR 10.82, 95% CI 3.82 to 30.6, p \u3c0.001). In conclusion, an integrated assessment of cardiac biomarkers may provide independent prognostic value for long-term adverse clinical events in stable cardiac patients

Plasma Myeloperoxidase Predicts Incident Cardiovascular Risks in Stable Patients Undergoing Medical Management for Coronary Artery Disease

BACKGROUND: Myeloperoxidase (MPO) concentrations predict adverse clinical outcomes in the setting of acute coronary syndromes and heart failure, but the prognostic role of MPO in stable patients with known atherosclerotic burden is unclear. METHODS: We examined plasma MPO concentrations and their relationship with prevalent significant coronary artery disease (defined as \u3e50% stenosis in any coronary vessel) and incident major adverse cardiovascular events (MACEs), including death, myocardial infarction, and stroke, in a 3-year prospective follow-up study of 1895 patients undergoing elective coronary angiography. RESULTS: The median plasma MPO concentration was 101 pmol/L (interquartile range 68–187 pmol/L). Patients with plasma MPO concentrations \u3e322 pmol/L (14.6% of population) had increased risk of developing future MACEs [hazard ratio (HR) 1.78, 95% CI 1.33–2.37, P \u3c 0.001], and MPO as a single variable predictor of MACE showed an area under the ROC curve of 0.67. After adjusting for traditional cardiac risk factors, creatinine clearance, B-type natriuretic peptide, and high-sensitivity C-reactive protein (hsCRP), increased MPO concentrations remained significantly associated with incident MACEs over the ensuing 3-year period (HR 1.71; 95% CI 1.27–2.30, P \u3c 0.001). In patients with increased hsCRP, MPO ≤322 pmol/L was associated with lower event rates than observed with MPO \u3e322 pmol/L. CONCLUSIONS: Plasma MPO concentrations provide independent prognostic value for the prediction of long-term incident MACEs in a stable, medically managed patient population with coronary artery disease. In individuals with increased hsCRP concentrations, we observed lower risk of incident MACEs when concomitant MPO concentrations were low vs when MPO concentrations were high

Plasma Myeloperoxidase Predicts Incident Cardiovascular Risks in Stable Patients Undergoing Medical Management for Coronary Artery Disease

BACKGROUND: Myeloperoxidase (MPO) concentrations predict adverse clinical outcomes in the setting of acute coronary syndromes and heart failure, but the prognostic role of MPO in stable patients with known atherosclerotic burden is unclear. METHODS: We examined plasma MPO concentrations and their relationship with prevalent significant coronary artery disease (defined as \u3e50% stenosis in any coronary vessel) and incident major adverse cardiovascular events (MACEs), including death, myocardial infarction, and stroke, in a 3-year prospective follow-up study of 1895 patients undergoing elective coronary angiography. RESULTS: The median plasma MPO concentration was 101 pmol/L (interquartile range 68–187 pmol/L). Patients with plasma MPO concentrations \u3e322 pmol/L (14.6% of population) had increased risk of developing future MACEs [hazard ratio (HR) 1.78, 95% CI 1.33–2.37, P \u3c 0.001], and MPO as a single variable predictor of MACE showed an area under the ROC curve of 0.67. After adjusting for traditional cardiac risk factors, creatinine clearance, B-type natriuretic peptide, and high-sensitivity C-reactive protein (hsCRP), increased MPO concentrations remained significantly associated with incident MACEs over the ensuing 3-year period (HR 1.71; 95% CI 1.27–2.30, P \u3c 0.001). In patients with increased hsCRP, MPO ≤322 pmol/L was associated with lower event rates than observed with MPO \u3e322 pmol/L. CONCLUSIONS: Plasma MPO concentrations provide independent prognostic value for the prediction of long-term incident MACEs in a stable, medically managed patient population with coronary artery disease. In individuals with increased hsCRP concentrations, we observed lower risk of incident MACEs when concomitant MPO concentrations were low vs when MPO concentrations were high