Wind capacity factor calculator

The wind capacity factor calculator is developed to perform two main tasks: to estimate the annual energy production from the wind resource at any location in South Africa, and to compare the two datasets used in its operation with standard error analysis to determine whether both datasets are suitable for use. This paper focuses on how the software was developed and on error analysis between the CSIR PV/ wind aggregation study data and the latest Wind Atlas for South Africa data. The results will indicate the way forward after determining whether the error found between the two datasets is significant enough to replace the former with latter, going forward

Band structure of semimagnetic Hg1-yMnyTe quantum wells

The band structure of semimagnetic Hg_1-yMn_yTe/Hg_1-xCd_xTe type-III quantum wells has been calculated using eight-band kp model in an envelope function approach. Details of the band structure calculations are given for the Mn free case (y=0). A mean field approach is used to take the influence of the sp-d exchange interaction on the band structure of QW's with low Mn concentrations into account. The calculated Landau level fan diagram and the density of states of a Hg_0.98Mn_0.02Te/Hg_0.3Cd_0.7Te QW are in good agreement with recent experimental transport observations. The model can be used to interpret the mutual influence of the two-dimensional confinement and the sp-d exchange interaction on the transport properties of Hg_1-yMn_yTe/Hg_1-xCd_xTe QW's.Comment: 12 pages, 4 figure

Assessing the value of improved variable renewable energy forecasting accuracy in the South African power system

The value associated with an improved variable renewable energy (VRE) forecast has been quantified in this research. The value of improved VRE forecasts can increase with increasing VRE penetration levels as well as the range of this value becoming wider. This value also saturates with high levels of improved VRE forecasts as there is relatively lower impact of improving VRE forecasts further. This paper discusses how the improvement of VRE forecasting could impact the South African power system and representative United States power system jurisdictions. &nbsp

Correlation of the Cd-to-Te ratio on CdTe surfaces with the surface structure

We report here that reconstruction on (100), (1lIlA, and (1l1lB CdTe surfaces is either C(2X2), (2X2), and (l X I) or (2X I), (l X I), and (l X I) when they are Cd or Te stabilized, respectively. There is a mixed region between Cd and Te stabilization in which the reflected high-energy electron-diffraction (RHEED) patterns contain characteristics of both Cd- and Te-stabilized surfaces. We have also found that the Cd-to-Te ratio of the x-ray photoelectron intensities of their 3d$_{3/ 2}$ core levels is about 20% larger for a Cd-stabilized (1lIlA, (1lIlB, or (100) CdTe surface than for a Te-stabilized one. According to a simple model calculation, which was normalized by means of the photoelectron intensity ratio of a Cd-stabilized (lll)A and aTe-stabilized (1l1lB CdTe surface, the experimental data for CdTe surfaces can be explained by a linear dependence of the photoelectron-intensity ratio on the fraction of Cd in the uppermost monatomic layer. This surface composition can be correlated with the surface structure, i.e., the corresponding RHEED patterns. This correlation can in turn be employed to determine Te and Cd evaporation rates. The Te reevaporation rate is increasingly slower for the Te-stabilized (Ill) A, (l1l)B, and (100) surfaces, while the opposite is true for Cd from Cd-stabilized (Ill) A and (Ill)B surfaces. In addition, Te is much more easily evaporated from all the investigated surfaces than is Cd, if the substrate is kept at normal molecular-beam-epitaxy growth temperatures ranging from 2oo·C to 300 ·C

Promoted Thermal Reduction of Copper Oxide Surfaces by N-Heterocyclic Carbenes

The influence of metallic and oxide phases coexisting on surfaces is of fundamental importance in heterogeneous catalysis. Many reactions lead to the reduction of the oxidized areas, but the elucidation of the mechanisms driving these processes is often challenging. In addition, intermediate species or designed organic ligands increase the complexity of the surface. In the present study, we address the thermal reduction of a copper oxide overlayer grown on Cu(111) in the presence of N-heterocyclic carbene (NHC) ligands by means of scanning tunneling microscopy (STM) and density functional theory (DFT). We show that the NHC ligands actively participate in the copper oxide reduction, promoting its removal at temperatures as low as 470 K. The reduction of the oxide was tracked by employing scanning tunneling spectroscopy (STS), providing a chemical identification of metallic and oxide areas at the nanometric scale

Growth of N-Heterocyclic Carbene Assemblies on Cu(100) and Cu(111): from Single Molecules to Magic-Number Islands

N-Heterocyclic carbenes (NHCs) have superior properties as building blocks of self-assembled monolayers (SAMs). Understanding the influence of the substrate in the molecular arrangement is a fundamental step before employing these ligands in technological applications. Herein, we study the molecular arrangement of a model NHC on Cu(100) and Cu(111). While mostly disordered phases appear on Cu(100), on Cu(111) well-defined structures are formed, evolving from magic-number islands to molecular ribbons with coverage. This work presents the first example of magic-number islands formed by NHC assemblies on flat surfaces. Intermolecular interactions, diffusion and commensurability are key factors explaining the observed arrangements. These results shed light on the molecule-substrate interaction and open the possibility of tuning nanopatterned structures based on NHC assemblies

Growth of N-Heterocyclic Carbene Assemblies on Cu(100) and Cu(111): from Single Molecules to Magic-Number Islands

N-Heterocyclic carbenes (NHCs) have superior properties as building blocks of self-assembled monolayers (SAMs). Understanding the influence of the substrate in the molecular arrangement is a fundamental step before employing these ligands in technological applications. Herein, we study the molecular arrangement of a model NHC on Cu(100) and Cu(111). While mostly disordered phases appear on Cu(100), on Cu(111) well-defined structures are formed, evolving from magic-number islands to molecular ribbons with coverage. This work presents the first example of magic-number islands formed by NHC assemblies on flat surfaces. Intermolecular interactions, diffusion and commensurability are key factors explaining the observed arrangements. These results shed light on the molecule-substrate interaction and open the possibility of tuning nanopatterned structures based on NHC assemblies

Covalent Adsorption of N-Heterocyclic Carbenes on a Copper Oxide Surface

Tuning the properties of oxide surfaces through the adsorption of designed ligands is highly desirable for several applications, such as catalysis. N-Heterocyclic carbenes (NHCs) have been successfully employed as ligands for the modification of metallic surfaces. On the other hand, their potential as modifiers of ubiquitous oxide surfaces still needs to be developed. Here we show that a model NHC binds covalently to a copper oxide surface under UHV conditions. In particular, we report the first example of a covalent bond between NHCs and oxygen atoms from the oxide layer. This study demonstrates that NHC can also act as a strong anchor on oxide surfaces

Identifying new potential biomarkers in adrenocortical tumors based on mrna expression data using machine learning

Adrenocortical carcinoma (ACC) is a rare disease, associated with poor survival. Several “multiple-omics” studies characterizing ACC on a molecular level identified two different clusters correlating with patient survival (C1A and C1B). We here used the publicly available transcriptome data from the TCGA-ACC dataset (n = 79), applying machine learning (ML) methods to classify the ACC based on expression pattern in an unbiased manner. UMAP (uniform manifold approximation and projection)-based clustering resulted in two distinct groups, ACC-UMAP1 and ACC-UMAP2, that largely overlap with clusters C1B and C1A, respectively. However, subsequent use of random-forest-based learning revealed a set of new possible marker genes showing significant differential expression in the described clusters (e.g., SOAT1, EIF2A1). For validation purposes, we used a secondary dataset based on a previous study from our group, consisting of 4 normal adrenal glands and 52 benign and 7 malignant tumor samples. The results largely confirmed those obtained for the TCGA-ACC cohort. In addition, the ENSAT dataset showed a correlation between benign adrenocortical tumors and the good prognosis ACC cluster ACC-UMAP1/C1B. In conclusion, the use of ML approaches re-identified and redefined known prognostic ACC subgroups. On the other hand, the subsequent use of random-forest-based learning identified new possible prognostic marker genes for ACC

Sources, Occurrence and Characteristics of Fluorescent Biological Aerosol Particles Measured Over the Pristine Southern Ocean.

In this study, we investigate the occurrence of primary biological aerosol particles (PBAP) over all sectors of the Southern Ocean (SO) based on a 90-day data set collected during the Antarctic Circumnavigation Expedition (ACE) in austral summer 2016-2017. Super-micrometer PBAP (1-16 µm diameter) were measured by a wide band integrated bioaerosol sensor (WIBS-4). Low (3σ) and high (9σ) fluorescence thresholds are used to obtain statistics on fluorescent and hyper-fluorescent PBAP, respectively. Our focus is on data obtained over the pristine ocean, that is, more than 200 km away from land. The results indicate that (hyper-)fluorescent PBAP are correlated to atmospheric variables associated with sea spray aerosol (SSA) particles (wind speed, total super-micrometer aerosol number concentration, chloride and sodium concentrations). This suggests that a main source of PBAP over the SO is SSA. The median percentage contribution of fluorescent and hyper-fluorescent PBAP to super-micrometer SSA was 1.6% and 0.13%, respectively. We demonstrate that the fraction of (hyper-)fluorescent PBAP to total super-micrometer particles positively correlates with concentrations of bacteria and several taxa of pythoplankton measured in seawater, indicating that marine biota concentrations modulate the PBAP source flux. We investigate the fluorescent properties of (hyper-)fluorescent PBAP for several events that occurred near land masses. We find that the fluorescence signal characteristics of particles near land is much more variable than over the pristine ocean. We conclude that the source and concentration of fluorescent PBAP over the open ocean is similar across all sampled sectors of the SO