General visualization tools typically require manual specification of views: analysts must select data variables and then choose which transformations and visual encodings to apply. These decisions ...often involve both domain and visualization design expertise, and may impose a tedious specification process that impedes exploration. In this paper, we seek to complement manual chart construction with interactive navigation of a gallery of automatically-generated visualizations. We contribute Voyager, a mixed-initiative system that supports faceted browsing of recommended charts chosen according to statistical and perceptual measures. We describe Voyager's architecture, motivating design principles, and methods for generating and interacting with visualization recommendations. In a study comparing Voyager to a manual visualization specification tool, we find that Voyager facilitates exploration of previously unseen data and leads to increased data variable coverage. We then distill design implications for visualization tools, in particular the need to balance rapid exploration and targeted question-answering.
There exists a gap between visualization design guidelines and their application in visualization tools. While empirical studies can provide design guidance, we lack a formal framework for ...representing design knowledge, integrating results across studies, and applying this knowledge in automated design tools that promote effective encodings and facilitate visual exploration. We propose modeling visualization design knowledge as a collection of constraints, in conjunction with a method to learn weights for soft constraints from experimental data. Using constraints, we can take theoretical design knowledge and express it in a concrete, extensible, and testable form: the resulting models can recommend visualization designs and can easily be augmented with additional constraints or updated weights. We implement our approach in Draco, a constraint-based system based on Answer Set Programming (ASP). We demonstrate how to construct increasingly sophisticated automated visualization design systems, including systems based on weights learned directly from the results of graphical perception experiments.
Modulators are widely used in the synthesis of metal‐organic frameworks (MOFs) for improving the porosity and morphology. For aluminum MOFs modulation has been seldom reported and as is shown here ...for the example of the aluminum furandicarboxylate MOF MIL‐160 the positive effects of modulators are small and disadvantageous effects will be more likely. Formic acid as modulator can slightly increase the BET surface area and pore volume of MIL‐160 up to a modulator:linker ratio of 1.25 : 1. Acetic acid only shows some increase in both surface area and pore volume at the smallest tested ratio of 0.125 : 1. The stronger acids oxalic acid and hydrochloric acid with the also more aluminum‐coordinating anions have no positive porosity effect and decrease surface area and pore volume already at small amounts. At a 1 : 1 modulator:linker ratio for oxalic acid and at 0.75 : 1 for hydrochloric acid no porous MOF is formed anymore from the analysis by powder X‐ray diffraction and nitrogen sorption. Further, thermogravimetric analysis and scanning electron microscopy suggests that none of the tested modulators has any noticeable positive effect on the introduction of linker defects or the improvement of crystallinity or crystal size.
Metal oxide‐based photoelectrodes for solar water splitting often utilize nanostructures to increase the solid‐liquid interface area. This reduces charge transport distances and increases the ...photocurrent for materials with short minority charge carrier diffusion lengths. While the merits of nanostructuring are well established, the effect of surface order on the photocurrent and carrier recombination has not yet received much attention in the literature. To evaluate the impact of pore ordering on the photoelectrochemical properties, mesoporous CuFe2O4 (CFO) thin film photoanodes were prepared by dip‐coating and soft‐templating. Here, the pore order and geometry can be controlled by addition of copolymer surfactants poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (Pluronic® F‐127), polyisobutylene‐block‐poly(ethylene oxide) (PIB‐PEO) and poly(ethylene‐co‐butylene)‐block‐poly(ethylene oxide) (Kraton liquid™‐PEO, KLE). The non‐ordered CFO showed the highest photocurrent density of 0.2 mA/cm2 at 1.3 V vs. RHE for sulfite oxidation, but the least photocurrent density for water oxidation. Conversely, the ordered CFO presented the best photoelectrochemical water oxidation performance. These differences can be understood on the basis of the high surface area, which promotes hole transfer to sulfite (a fast hole acceptor), but retards oxidation of water (a slow hole acceptor) due to electron‐hole recombination at the defective surface. This interpretation is confirmed by intensity‐modulated photocurrent (IMPS) and vibrating Kelvin probe surface photovoltage spectroscopy (VKP‐SPS). The lowest surface recombination rate was observed for the ordered KLE‐based mesoporous CFO, which retains spherical pore shapes at the surface resulting in fewer surface defects. Overall, this work shows that the photoelectrochemical energy conversion efficiency of copper ferrite thin films is not just controlled by the surface area, but also by surface order.
A systematic comparison of distinct surface morphologies of sol‐gel‐derived CuFe2O4 for solar water splitting shows that high‐surface‐area photoelectrodes are preferred for driving thermodynamically favorable reactions, such as sulfite oxidation, while lower surface area photoabsorbers are beneficial for driving thermodynamically uphill processes like the water oxidation reaction.
Cyclic physical adsorption and desorption processes on porous materials can be used for the conversion of heat in heat transformation processes, which is the working principle in adsorption heat ...pumps (AHPs). Environmentally benign water with its high enthalpy of evaporation is the working fluid of choice in AHPs. Metal‐organic frameworks, MOFs can adsorb large amounts of water or methanol, up to their own weight. MOFs could be alternative materials to silica gels, zeolites, or aluminum phosphates for low‐temperature heat transformations in AHPs.
Microporous and water‐stable MOFs with high water‐uptake capacity are gaining attention for low‐temperature heat transformation applications in adsorption heat pumps as an alternative to traditional air conditioners or heat pumps operating on electricity. AHPs are based on the evaporation and consecutive adsorption of coolant liquids, preferably water, in a porous material under specific conditions. By using waste heat as the operating energy AHPs can significantly help to minimize primary energy consumption.
Metal oxide-based photoelectrodes for solar water splitting often utilize nanostructures to increase the solid-liquid interface area. This reduces charge transport distances and increases the ...photocurrent for materials with short minority charge carrier diffusion lengths. While the merits of nanostructuring are well established, the effect of surface order on the photocurrent and carrier recombination has not yet received much attention in the literature. To evaluate the impact of pore ordering on the photoelectrochemical properties, mesoporous CuFe
O
(CFO) thin film photoanodes were prepared by dip-coating and soft-templating. Here, the pore order and geometry can be controlled by addition of copolymer surfactants poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic® F-127), polyisobutylene-block-poly(ethylene oxide) (PIB-PEO) and poly(ethylene-co-butylene)-block-poly(ethylene oxide) (Kraton liquid™-PEO, KLE). The non-ordered CFO showed the highest photocurrent density of 0.2 mA/cm
at 1.3 V vs. RHE for sulfite oxidation, but the least photocurrent density for water oxidation. Conversely, the ordered CFO presented the best photoelectrochemical water oxidation performance. These differences can be understood on the basis of the high surface area, which promotes hole transfer to sulfite (a fast hole acceptor), but retards oxidation of water (a slow hole acceptor) due to electron-hole recombination at the defective surface. This interpretation is confirmed by intensity-modulated photocurrent (IMPS) and vibrating Kelvin probe surface photovoltage spectroscopy (VKP-SPS). The lowest surface recombination rate was observed for the ordered KLE-based mesoporous CFO, which retains spherical pore shapes at the surface resulting in fewer surface defects. Overall, this work shows that the photoelectrochemical energy conversion efficiency of copper ferrite thin films is not just controlled by the surface area, but also by surface order.
Genomes computationally inferred from large metagenomic data sets are often incomplete and may be missing functionally important content and strain variation. We introduce an information retrieval ...system for large metagenomic data sets that exploits the sparsity of DNA assembly graphs to efficiently extract subgraphs surrounding an inferred genome. We apply this system to recover missing content from genome bins and show that substantial genomic sequence variation is present in a real metagenome. Our software implementation is available at https://github.com/spacegraphcats/spacegraphcats under the 3-Clause BSD License.
Interfaces are key elements that define electronic properties of the final device. Inevitably, most of the active interfaces of III–V semiconductor devices are buried and it is therefore not ...straightforward to characterize them. The Tapered Cross Section Photoelectron Spectroscopy (TCS‐PES) approach is promising to address such a challenge. That the TCS‐PES can be used to study the relevant heterojunction in epitaxial III–V architectures prepared by metalorganic chemical vapor deposition is demonstrated here. A MULTIPREP polishing system that enables controlling the angle between the sample holder and the polishing plate has been employed to improve the reproducibility of the polishing procedure. With this procedure, that preparing the TCS of III–V semiconductor devices with tapering angles lower than 0.02° is possible is demonstrated. The PES provides then information about the buried interfaces of Ge|GaInP and GaAs|GaInP layer stacks. Both, chemical and electronic properties have been measured by PES. It evidences that the preparation of the TCSs under an uncontrolled atmosphere modifies the pristine properties of the critical buried heterointerfaces. Surface states and reaction layers are created on the TCS surface, which restrict unambiguous conclusions on buried interface energetics.
Tapered Cross Section Photoelectron Spectroscopy (TCS‐PES), a promising method to investigate the chemistry and electronic structure at buried interfaces in semiconductor devices, is for the first time used on III–V architectures. PES yielded insight into the chemistry at the buried interfaces, but polishing induced alterations limit the information on interface energetics.
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