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Found in: ključnih besedah
Keywords: Heterogeneous ice nucleation, Bacterial INP, Cloud ice, Precipitation, Global solar radiation, Numerical weather prediction model
Published: 04.01.2021; Views: 1279; Downloads: 0
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Abstract: The COVID-19 pandemic has become a major threat to the whole world. Analysis of this disease requires major attention by the government in all countries to take necessary steps in reducing the effect of this global pandemic. In this study, outbreak of this disease has been analysed and trained for Indian region till 10th May, 2020, and testing has been done for the number of cases for the next three weeks. Machine learning models such as SEIR model and Regression model have been used for predictions based on the data collected from the official portal of the Government of India in the time period of 30th January, 2020, to 10th May, 2020. The performance of the models was evaluated using RMSLE and achieved 1.52 for SEIR model and 1.75 for the regression model. The RMSLE error rate between SEIR model and Regression model was found to be 2.01. Also, the value of R0, which is the spread of the disease, was calculated to be 2.84. Expected cases are predicted around 175K--200K in the three-week time period of test data, which is very close to the actual numbers. This study will help the government and doctors in preparing their plans for the future.
Found in: ključnih besedah
Summary of found: ...for the next three weeks. Machine learning models such as SEIR model and Regression model...
Keywords: COVID-19, India, spread exposed infected recovered model, regression model, machine learning, predictions, forecasting
Published: 01.04.2021; Views: 833; Downloads: 50
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Abstract: Aerosol properties are transformed by atmospheric processes during long-range transport and play a key role in the Earth’s radiative balance. To understand the molecular and physical characteristics of free tropospheric aerosol, we studied samples collected at the Pico Mountain Observatory in the North Atlantic. The observatory is located in the marine free troposphere at 2225m above sea level, on Pico Island in the Azores archipelago. The site is ideal for the study of long-range-transported free tropospheric aerosol with minimal local influence. Three aerosol samples with elevated organic carbon concentrations were selected for detailed analysis. FLEXPART retroplumes indicated that two of the samples were influenced by North American wildfire emissions transported in the free troposphere and one by North American outflow mainly transported within the marine boundary layer. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry was used to determine the detailed molecular composition of the samples. Thousands of molecular formulas were assigned to each of the individual samples. On average ~60% of the molecular formulas contained only carbon, hydrogen, and oxygen atoms (CHO), ~ 30% contained nitrogen (CHNO), and ~ 10% contained sulfur (CHOS). The molecular formula compositions of the two wildfire-influenced aerosol samples transported mainly in the free troposphere had relatively low average O=C ratios (0:48 ± 0:13 and 0:45 ± 0:11) despite the 7–10 days of transport time according to FLEXPART. In contrast, the molecular composition of the North American outflow transported mainly in the boundary layer had a higher average O=C ratio (0:57 ± 0:17) with 3 days of transport time. To better understand the difference between free tropospheric transport and boundary layer transport, the meteorological conditions along the FLEXPART simulated transport pathways were extracted from the Global Forecast System analysis for the model grids. We used the extracted meteorological conditions and the observed molecular chemistry to predict the relative-humidity-dependent glass transition temperatures (Tg) of the aerosol components. Comparisons of the Tg to the ambient temperature indicated that a majority of the organic aerosol components transported in the free troposphere were more viscous and therefore less susceptible to oxidation than the organic aerosol components transported in the boundary layer. Although the number of observations is limited, the results suggest that biomass burning organic aerosol injected into the free troposphere is more persistent than organic aerosol in the boundary layer having broader implications for aerosol aging.
Found in: ključnih besedah
Summary of found: ...from the Global Forecast System analysis for the model grids. We used the extracted meteorological conditions and...
Keywords: secondary organic aerosols, brown carbon, particle dispersion model, ultrahigh-resolution FT-ICR MS, Pico Mountain Observatory
Published: 10.04.2021; Views: 725; Downloads: 0
Fulltext (5,35 MB)

Abstract: Studies of biopolymer conformations essentially rely on theoretical models that are routinely used to process and analyze experimental data. While modern experiments allow study of single molecules in vivo, corresponding theories date back to the early 1950s and require an essential update to include the recent significant progress in the description of water. The Hamiltonian formulation of the Zimm-Bragg model we propose includes a simplified, yet explicit model of water-polypeptide interactions that transforms into the equivalent implicit description after performing the summation of solvent degrees of freedom in the partition function. Here we show that our model fits very well to the circular dichroism experimental data for both heat and cold denaturation and provides the energies of inter- and intra- molecular H-bonds, unavailable with other processing methods. The revealed delicate balance between these energies determines the conditions for the existence of cold dena- turation and thus clarifies its absence in some proteins.
Found in: ključnih besedah
Keywords: protein folding, cold denaturation, water, Zimm-Bragg model
Published: 06.05.2021; Views: 859; Downloads: 3
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Abstract: The present diploma seminar work has been dedicated first to the implementation of a procedure to calculate the vibrational density of states of two structural models of vitreous SiO 2 (v- SiO 2 ) and amorphous Al 2 O 3 (am-Al 2 O 3 ) models, and next to tune a parametric model for the calculation of the infrared (IR) spectra of am-Al 2 O 3 , in particular of the imaginary part of the dielectric function. The ground state of both structural models is obtained by relaxing the atomic structure by using the conjugate gradient method as implemented in the LAMMPS code. Vibrational frequencies and modes are obtained, in the harmonic approximation, by diagonalizing the dynamical matrices calculated for the given v-SiO 2 and am-Al 2 O 3 structural models. Dynamical matrices are obtained through a finite differences approach and vibrational density of states are plotted by applying Gaussian broadening. The calculation of the dielectric function requires the knowledge of the vibrational frequencies as well as the knowledge of the dynamical (or Born) charge tensors related to the atoms of the am-Al 2 O 3 structural model. For the latter model, a parametrization of the ab-initio Born charge tensors has been carried out with the purpose to allow for the fast calculation of the IR spectrum of any other am- Al 2 O 3 model without the need to calculate for it the Born charge tensors using expensive ab- initio methods. The parametrization of Born charge tensors takes into account, for aluminium atoms, only of the isotropic charge which depends on coordination number and average Al- O bond length of aluminium atoms, while for oxygen atoms coordinated to three Al atoms (75%), dynamical charges are parametrized also by the area bounded by aluminium atoms nearest neighbours of the 3-coordinated oxygen atom. Moreover for analyzing the dynamical charge tensors of 3-coordinated oxygen atoms a decomposition in terms of the representations of the spatial rotations was used. The IR spectrum obtained by means of the above described parametrization provides a good approximation to the IR spectrum obtained by using the ab- initio calculated dynamical charges, as it differs from it, on average, by around 5.1% which is much better (12%) than using a average isotropic charge model (i.e. diagonal Born charge tensors where each diagonal element is one third of the average isotropic charge).
Found in: ključnih besedah
Keywords: Vibrational spectra, am-Al 2 O 3, parametric model
Published: 15.09.2021; Views: 649; Downloads: 0
Fulltext (859,22 KB)