Instantons and Holomorphic Couplings in Intersecting D-brane Models

We clarify certain aspects and discuss extensions of the recently introduced string D-instanton calculus (hep-th/0609191). The one-loop determinants are related to one-loop open string threshold corrections in intersecting D6-brane models. Utilising a non-renormalisation theorem for the holomorphic Wilsonian gauge kinetic functions, we derive a number of constraints for the moduli dependence of the matter field Kaehler potentials of intersecting D6-brane models on the torus. Moreover, we compute string one-loop corrections to the Fayet-Iliopoulos terms on the D6-branes finding that they are proportional to the gauge threshold corrections. Employing these results, we discuss the issue of holomorphy for E2-instanton corrections to the superpotential. Eventually, we discuss E2-instanton corrections to the gauge kinetic functions and the FI-terms.Comment: 28 pages, 5 figure

NSAIDs and Their Interactions with Bacterial Growth

Non-steroidal anti-inflammatory drugs (NSAIDs) are common medications that are frequently used to suppress symptoms of viral and bacterial infections. The increase in concern of antibiotic resistance has led researchers to study the effects of NSAIDs on bacterial growth or on common antibiotics. This study aims to determine whether commonly used NSAIDs, ibuprofen and acetaminophen, have any antibacterial properties that might help suppress bacterial growth. In conjunction, this study also looks to see whether the combination of NSAIDs and an antibiotic can further reduce bacterial growth than if an antibiotic is used alone. Our procedure consisted of lab-grown Escherichia coli (E. coli) that was mixed with ibuprofen (8ug/ml), acetaminophen (15ug/ml), or ampicillin at either 8 or 15ug/ml. These concentrations are based on typical blood serum levels of each respective drug. UV spectrophotometer was used to determine bacterial growth through absorbance values (600nm). The results show larger absorbance values (meaning greater bacterial growth) when ibuprofen and acetaminophen are present. Data also shows that when NSAIDs are used in combination with ampicillin, absorbance values would be greater than if ampicillin was used alone. Possible mechanisms leading to these results could include horizontal gene transfer in E. coli or inhibiting the antibiotic effects of ampicillin. Future research should focus on determining the primary mechanism NSAIDs use to promote bacterial growth or inhibit antibiotics

A Survey on Blockchain for Information Systems Management and Security

© 2020 Elsevier Ltd Blockchain technologies have grown in prominence in recent years, with many experts citing the potential applications of the technology in regard to different aspects of any industry, market, agency, or governmental organizations. In the brief history of blockchain, an incredible number of achievements have been made regarding how blockchain can be utilized and the impacts it might have on several industries. The sheer number and complexity of these aspects can make it difficult to address blockchain potentials and complexities, especially when trying to address its purpose and fitness for a specific task. In this survey, we provide a comprehensive review of applying blockchain as a service for applications within today\u27s information systems. The survey gives the reader a deeper perspective on how blockchain helps to secure and manage today information systems. The survey contains a comprehensive reporting on different instances of blockchain studies and applications proposed by the research community and their respective impacts on blockchain and its use across other applications or scenarios. Some of the most important findings this survey highlights include the fact that blockchain\u27s structure and modern cloud- and edge-computing paradigms are crucial in enabling a widespread adaption and development of blockchain technologies for new players in today unprecedented vibrant global market. Ensuring that blockchain is widely available through public and open-source code libraries and tools will help to ensure that the full potential of the technology is reached and that further developments can be made concerning the long-term goals of blockchain enthusiasts

Biochars from chlorine-rich feedstock are low in polychlorinated dioxins, furans and biphenyls

Chlorinated aromatic hydrocarbons like polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) and polychlorinated biphenyls (PCB) are omnipresent in the environment due to historic production, use, and (unintended) release. Nowadays, their emission and maximum concentration in environmental compartments is strictly regulated. During biochar production, PCDD/F and PCB may be formed and retained on the solid pyrolysis product. Industrial biochars certified, e.g., under the European Biochar Certificate (EBC), exhibit concentrations that were always well below threshold values for soil application and even animal feed. However, this has not been sufficiently tested for chlorine (Cl) rich organic material such as marine biomass or polyvinyl chloride (PVC) contaminated feedstock. Here, we analyzed PCDD/F and PCB contamination in biochars produced at different temperatures from different biomasses with comparatively high Cl contents in the range from 0.2 % to 3.8 % (w/w, seagrass, two types of saltwater macroalgae, tobacco stalks, and PVC contaminated wood). All of the biochars produced showed PCDD/F and PCB contents well below the applicable threshold values given by the EBC (< 20 ng TEQ kg−1 for PCDD/F and < 2×105 ng kg−1 for PCB). The EBC thresholds were undershot by a minimum of factor 1.5 for PCDD/F (mostly factor 20) and by a minimum of factor 90 for PCB. Between 1 and 27 ppb of feedstock Cl were transformed to Cl bound in PCDD/F and PCB in the biochars. No consistent correlation between biomass Cl contents and contents of PCDD/F and PCB were found but higher Cl contents in the feedstock led to a more diverse PCDD/F congener pattern in the biochars. Pyrolysis of PVC-amended wood resulted in consistently higher contamination of PCDD/F and PCB in the biochars compared to pyrolysis of the other biomasses, potentially due to differences in Cl speciation in the feedstocks i.e., Cl in PVC is already covalently bound to an organic carbon backbone. A high contamination in PCDD/F and PCB in biochar was intentionally triggered by separation of pyrogas and biochar in the reactor at < 300 °C to promote condensation of contaminants on the solid product. Between 20 % and 80 % of feedstock Cl was released via the pyrogas, i.e., neutralization of HCl in burnt pyrogas might be necessary when pyrolyzing Cl-rich feedstock in industrial biochar production. Our results indicate that biochars produced from Cl-rich feedstocks with proper biochar production process control are conform with European certification guidelines for PCDD/F and PCB contamination. The results open the opportunity to exploit and valorize so far non-used marine or otherwise Cl enriched biomasses for the production of biochar and carbon sinks

Quantifying soil organic carbon after biochar application: how to avoid (the risk of) counting CDR twice?

Pyrogenic carbon capture and storage (PyCCS), which comprises the production of biomass, its pyrolysis, and the non-oxidative use of the biochar to create carbon sinks, has been identified as a promising negative emission technology with co-benefits by improving soil properties. Using biochar as a soil additive becomes increasingly common as farmers seek methods for soil improvement and climate change adaptation. Concurrently, there is growing interest in quantifying soil organic carbon (SOC) at the level of individual plots to remunerate farmers for their good agricultural practices and the resulting (temporary) carbon dioxide removal (CDR). However, methods currently applied in routine analysis quantify SOC, irrespective of its speciation or origin, and do not allow to distinguish biochar-C from SOC. As certification of PyCCS-derived CDR is already established using another quantification method (i.e., analysis of biochar-C content, tracking and registration of its application, and offsetting of carbon expenditures caused by the PyCCS process), the analysis of biochar-C as part of SOC may result in double counting of CDR. Hence, the objectives of this review are (1) to compare the physicochemical properties and the quantities of biochar and SOC fractions on a global and field/site-specific scale, (2) to evaluate the established methods of SOC and pyrogenic carbon (PyC) quantification with regard to their suitability in routine analysis, and (3) to assess whether double counting of SOC and biochar C-sinks can be avoided via analytical techniques. The methods that were found to have the potential to distinguish between non-pyrogenic and PyC in soil are either not fit for routine analysis or require calibration for different soil types, which is extremely laborious and yet to be established at a commercial scale. Moreover, the omnipresence of non-biochar PyC in soils (i.e., from forest fires or soot) that is indistinguishable from biochar-C is an additional challenge that can hardly be solved analytically. This review highlights the risks and limits of only result-based schemes for SOC certification relying on soil sampling and analysis. Carbon sink registers that unite the (spatial) data of biochar application and other forms of land-based CDR are suggested to track biochar applications and to effectively avoid double counting

Thresholds for Intersecting D-branes Revisited

Gauge threshold corrections for intersecting D6-brane string models on toroidal orbifold backgrounds are reconsidered. Both by dimensionally regularising the appearing open string one-loop diagrams in tree-channel as well as by zeta-function regularisation of the corresponding loop-channel one-loop diagrams, we arrive at a result which takes into account the infrared divergence from the contribution of the massless states in the running of the gauge coupling constant as well as the contribution of states, which become light in certain regions of the moduli space.Comment: 14 page

Optimization of low-NOx partially premixed hydrogen burners using numerical simulation and flame diagnostics

This study presents fundamental numerical and experimental investigations on hydrogen combustion in model burners. The effects of the equivalence ratio, pressure and preheating temperature on the laminar flame speed and combustion temperature are numerically investigated using CANTERA (based on GRI-Mech 3.0 as reaction mechanism). Furthermore, the aspect of nitric oxides (NOx) reduction by lowering the flame temperature was examined more closely. Based on these fundamental studies, a partially premixed single nozzle burner was developed using the 3D-CFD-code (CFD: Computational Fluid Dynamics) STAR-CCM+ (Siemens PLM) to optimize mixture formation and combustion. The overall burner design enables the variation of some important geometrical parameters of the nozzle for mixture preparation during the optimization process. The aim is homogeneous distribution of the fuel-air ratio (equivalence ratio) at the nozzle exit after a short mixing duct. The flame of the manufactured burner was investigated using an IR-camera and exhaust gas analysis. Stable operation of the micro-nozzle burner was found for a global equivalence ratio of 0.40 at 0.3 kW-1.0 kW at low NOx-emissions (below 10 ppmv)

Pyrogenic carbon capture and storage

The growth of biomass is considered the most efficient method currently available to extract carbon dioxide from the atmosphere. However, biomass carbon is easily degraded by microorganisms releasing it in the form of greenhouse gases back to the atmosphere. If biomass is pyrolyzed, the organic carbon is converted into solid (biochar), liquid (bio-oil), and gaseous (permanent pyrogas) carbonaceous products. During the last decade, biochar has been discussed as a promising option to improve soil fertility and sequester carbon, although the carbon efficiency of the thermal conversion of biomass into biochar is in the range of 30%–50% only. So far, the liquid and gaseous pyrolysis products were mainly considered for combustion, though they can equally be processed into recalcitrant forms suitable for carbon sequestration. In this review, we show that pyrolytic carbon capture and storage (PyCCS) can aspire for carbon sequestration efficiencies of >70%, which is shown to be an important threshold to allow PyCCS to become a relevant negative emission technology. Prolonged residence times of pyrogenic carbon can be generated (a) within the terrestrial biosphere including the agricultural use of biochar; (b) within advanced bio-based materials as long as they are not oxidized (biochar, bio-oil); and (c) within suitable geological deposits (bio-oil and CO 2 from permanent pyrogas oxidation). While pathway (c) would need major carbon taxes or similar governmental incentives to become a realistic option, pathways (a) and (b) create added economic value and could at least partly be implemented without other financial incentives. Pyrolysis technology is already well established, biochar sequestration and bio-oil sequestration in soils, respectively biomaterials, do not present ecological hazards, and global scale-up appears feasible within a time frame of 10–30 years. Thus, PyCCS could evolve into a decisive tool for global carbon governance, serving climate change mitigation and the sustainable development goals simultaneously. © 2018 John Wiley & Sons Lt

NIR-Emission Spectroscopy for Local Temperature Measurements in Premixed Hydrogen/Air Flames

Adopting hydrogen fuel for combustion at scale requires a deeper understanding of the flame behavior with respect to the combustion properties of H2 and type of burner used. Non-invasive optical diagnostics have the potential to enhance our understanding of H2 combustion. For instance, near-infrared emission spectroscopy yields path-averaged information that can be employed to characterize the temperature field. In H2 flames, the emission spectrum of water vapor can be used to quantify the temperature field and elucidate the underlying physical processes. In the present study, temperature is determined throughout a premixed turbulent H2/air flame via NIR spectra, accounting for effects of the instrument and experimental configuration

Ultrafast proton-coupled isomerization in the phototransformation of phytochrome

The biological function of phytochromes is triggered by an ultrafast photoisomerization of the tetrapyrrole chromophore biliverdin between two rings denoted C and D. The mechanism by which this process induces extended structural changes of the protein is unclear. Here we report ultrafast proton-coupled photoisomerization upon excitation of the parent state (Pfr) of bacteriophytochrome Agp2. Transient deprotonation of the chromophore’s pyrrole ring D or ring C into a hydrogen-bonded water cluster, revealed by a broad continuum infrared band, is triggered by electronic excitation, coherent oscillations and the sudden electric-field change in the excited state. Subsequently, a dominant fraction of the excited population relaxes back to the Pfr state, while ~35% follows the forward reaction to the photoproduct. A combination of quantum mechanics/molecular mechanics calculations and ultrafast visible and infrared spectroscopies demonstrates how proton-coupled dynamics in the excited state of Pfr leads to a restructured hydrogen-bond environment of early Lumi-F, which is interpreted as a trigger for downstream protein structural changes