Vibrational fingerprint of the absorption properties of UiO-type MOF materials

The absorption properties of UiO-type metal-organic frameworks are computed using TD-DFT simulations on the organic linkers. A set of nine isoreticular structures, including the UiO-66 and UiO-67 materials and functionalized variants, are examined. The excitation energies from a static geometry optimization are compared with dynamic averages obtained from sampling the ground-state potential energy surface using molecular dynamics. The vibrational modes that impact the excitation energy are identified. This analysis is done using a recently proposed tool based on power spectra of the velocities and the excitation energies. The applied procedure allows including important factors influencing the absorption spectra, such as the periodic framework, linker variation and dynamical effects including harmonic and anharmonic nuclear motions. This methodology allows investigating in detail the vibrational fingerprint of the excitation energy of advanced materials such as MOFs and gives perspectives to tailor materials toward new light-based applications

Superior removal of arsenic from water with zirconium metal-organic framework UiO-66

10.1038/srep16613Scientific Reports51661

Real Exchange Rate Misalignment: An Application of Behavioral Equilibrium Exchange Rate (BEER) to Nigeria

Abstract This paper seeks to estimate the long run behavioral equilibrium exchange rate in Nigeria. The empirical analysis builds on quarterly data from 1986Q1 to 2006Q4 and derives a Behavioral Equilibrium Exchange Rate (BEER) and a Permanent Equilibrium Exchange Rate (PEER). The econometric analysis starts by analyzing the stochastic properties of the data and found all the variables stationary at first level of differencing. Accordingly, the paper proceeds by estimating vector-error correction models. Regression results show that most of the long-run behavior of the real exchange rate could be explained by real net foreign assets, terms of trade, index of crude oil volatility, index of monetary policy performance and government fiscal stance. On the basis of these fundamentals, four episodes each of overvaluation and undervaluation were identified and the antecedents characterizing the episodes were equally traced to the archive of exchange rate management in the country within the review period. Among others for instance, large inflow of oil revenues into the country and stable macroeconomic performance were discovered to account for undervaluation of the real exchange rate between 2001Q1 and 2006Q4 in Nigeria. The results further suggest that deviations from the equilibrium path are eliminated within one to two years. The paper recommends the pursuance of sound monetary policy as an instrument for achieving real exchange rate cum macroeconomic stability in Nigeria.Keywords: real exchange rate equilibrium, stationarity, cointegration, Hodrick-Prescott decomposition, BEER and PEER

Methods for heat transfer and temperature field analysis of the insulated diesel

Work done during phase 1 of a three-year program aimed at developing a comprehensive heat transfer and thermal analysis methodology oriented specifically to the design requirements of insulated diesel engines is reported. The technology developed in this program makes possible a quantitative analysis of the low heat rejection concept. The program is comprehensive in that it addresses all the heat transfer issues that are critical to the successful development of the low heat rejection diesel engine: (1) in-cylinder convective and radiative heat transfer; (2) cyclic transient heat transfer in thin solid layers at component surfaces adjacent to the combustion chamber; and (3) steady-state heat conduction in the overall engine structure. The Integral Technologies, Inc. (ITI) program is comprised of a set of integrated analytical and experimental tasks. A detailed review of the ITI program approach is provided, including the technical issues which underlie it and a summay of the methods that were developed

Designing of Organic Bridging Linkers of Metal-Organic Frameworks for Enhanced Carbon Dioxide Adsorption

The global rate of anthropogenic CO2 emission is rising, which urges the development of efficient carbon capture and storage (CCS) technologies. Among the various CO2 capture methods, adsorption by the linkers of the Metal-Organic Frameworks (MOFs) materials has received more interest as excellent CO2 adsorbents because of their important role in understanding the interaction mechanism for CO2 adsorption. Here, we investigate the adsorption of CO2 molecules at the center and side positions of several MOF-linkers using molecular cluster models. The interaction between CO2 and the linkers is approximated by computing the binding enthalpy ({\Delta}H) through the first principles-based Density Functional Theory with Grimmes dispersion correction (i.e., B3LYP-D3) and second-order Moller Plesset Theory (MP2). The computed values of {\Delta}H indicate the weak nature of CO2 adsorption on the pristine linkers, hence the strategy of lithium decoration is used to see its impact on the binding strength. Among the various linkers tested, CO2 adsorbing at the side position of the DFBDC-2 linker has strong adsorption with {\Delta}H value of about -35.32 kJ/mol computed by the B3LYP-D3 method. The Energy Decomposition Analysis (EDA) study reveals that among all the energy terms, the contribution of electrostatic and polarization energy terms to the {\Delta}H value are the most dominant one. Furthermore, the results of Frontier Molecular Orbital Analysis (FMO) revealed that all the linkers remained stable even after Li-decoration. The results of our investigations will direct towards the development and synthesis of novel adsorbents with enhanced CO2 adsorption.Comment: 24 pages, 9 figure

An acoustic view of ocean mixing

Knowledge of the parameter K (turbulent diffusivity/"mixing intensity") is a key to understand transport processes of matter and energy in the ocean. Especially the almost vertical component of K across the ocean stratification (diapycnal diffusivity) is vital for research on biogeochemical cycles or greenhouse gas budgets. Recent boost in precision of water velocity data that can be obtained from vessel-mounted acoustic instruments (vmADCP) allows identifying ocean regions of elevated diapycnal diffusivity during research cruises - in high horizontal resolution and without extra ship time needed. This contribution relates acoustic data from two cruises in the Tropical North East Atlantic Oxygen Minimum Zone to simultaneous field observations of diapycnal diffusivity: pointwise measurements by a microstructure profiler as well as one integrative value from a large scale Tracer Release Experiment

The detailed velocity structure and distribution of 13CO emission in the Galactic plane

Studying the detailed velocity structure of molecular gas in our Galaxy is of fundamental importance for understanding structure formation in the interstellar medium. Knowledge about the detailed gas kinematics is moreover essential to map the distribution and dynamics of the molecular gas in the Milky Way. In this thesis I use the method of spectral decomposition to analyse the 13CO (1-0) observations of the Galactic Ring Survey (GRS). I developed the GaussPy+ package, specifically designed for the fully automated decomposition of large Galactic plane surveys, to fit the ~2.3 million spectra of this large emission line data set. After extensive validation of the algorithm using synthetic spectra and a GRS test field, I use GaussPy+ to fit the entire data set of the GRS, resulting in ~4.6 million Gaussian fit components. These decomposition results provide a new way to analyse the dynamics of the molecular gas over a wide extent of the Galactic plane and study how its velocity structure looks like and varies at Galactic to sub-cloud scales. I find that the velocity dispersion of the gas is increased in the midplane and towards the inner Galaxy, and establish that the integrated emission of the velocity components correlates well with the complexity of the gas emission and the amount of dust emission along the line of sight. Moreover, I uncover qualitatively similar fluctuations in the centroid velocities of the gas components throughout the entire GRS data set, and demonstrate how the fitted linewidths enable the separation of blended gas emission features that originate from nearby regions and far distances. Finally, I use a Bayesian approach to obtain the current best assessment of the Galactic distribution of 13CO. As prior information, I use the presently most precise knowledge about the structure and kinematics of the Milky Way and an extensive compilation of distances from literature. I perform two different distance calculations that either include or exclude a prior for a model of Galactic features, which allows me to characterise possible biases of the distance estimates and establish more reliable limits on the 13CO distribution. I establish that the majority (76% to 84%) of the 13CO emission is associated with spiral arm features. However, I do not find significant differences between the gas emission properties associated with spiral arm and interarm features. I conclude that the decomposition results provide a wealth of data enabling new and unexplored ways to interpret the detailed gas velocity structure of large Galactic plane surveys. The methodology and results presented in this thesis allowed for a homogeneous study of the dynamics and distribution of the molecular gas over a large fraction of the Galactic disk. As demonstrated in this work, the information extracted from the detailed gas kinematics and its combination with complementary tracers of the interstellar medium has enormous potential to further our knowledge about the physical processes and mechanisms shaping the interstellar medium

Deep-Inelastic Inclusive ep Scattering at Low x and a Determination of alpha_s

A precise measurement of the inclusive deep-inelastic e^+p scattering cross section is reported in the kinematic range 1.5<= Q^2 <=150 GeV^2 and 3*10^(-5)<= x <=0.2. The data were recorded with the H1 detector at HERA in 1996 and 1997, and correspond to an integrated luminosity of 20 pb^(-1). The double differential cross section, from which the proton structure function F_2(x,Q^2) and the longitudinal structure function F_L(x,Q^2) are extracted, is measured with typically 1% statistical and 3% systematic uncertainties. The measured partial derivative (dF_2(x,Q^2)/dln Q^2)_x is observed to rise continuously towards small x for fixed Q^2. The cross section data are combined with published H1 measurements at high Q^2 for a next-to-leading order DGLAP QCD analysis.The H1 data determine the gluon momentum distribution in the range 3*10^(-4)<= x <=0.1 to within an experimental accuracy of about 3% for Q^2 =20 GeV^2. A fit of the H1 measurements and the mu p data of the BCDMS collaboration allows the strong coupling constant alpha_s and the gluon distribution to be simultaneously determined. A value of alpha _s(M_Z^2)=0.1150+-0.0017 (exp) +0.0009-0.0005 (model) is obtained in NLO, with an additional theoretical uncertainty of about +-0.005, mainly due to the uncertainty of the renormalisation scale.Comment: 68 pages, 24 figures and 18 table