Multiloop Superstring Amplitudes from Non-Minimal Pure Spinor Formalism

Using the non-minimal version of the pure spinor formalism, manifestly super-Poincare covariant superstring scattering amplitudes can be computed as in topological string theory without the need of picture-changing operators. The only subtlety comes from regularizing the functional integral over the pure spinor ghosts. In this paper, it is shown how to regularize this functional integral in a BRST-invariant manner, allowing the computation of arbitrary multiloop amplitudes. The regularization method simplifies for scattering amplitudes which contribute to ten-dimensional F-terms, i.e. terms in the ten-dimensional superspace action which do not involve integration over the maximum number of $\theta$'s.Comment: 23 pages harvmac, added acknowledgemen

Synthesis of Nanoporous Type A and X Zeolite Mixtures from Biomass Combustion Fly Ash for Post-Combustion Carbon Capture

In this study, improved nanoporous zeolites for use in post-combustion carbon capture have been synthesised from industrial-grade biomass combustion fly ash generated in one of the largest biomass combustion power plants in the UK. The method of nanoporous zeolite synthesis follows an alkaline fusion-assisted hydrothermal procedure. The nanoporous zeolites have been characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The presence of two crystalline structures, Faujasite and Linde Type A has been confirmed by the characterisation results. The CO 2 adsorption investigations were conducted via thermogravimetric analysis (TGA) to estimate the uptake capacity of the prepared adsorbents. TGA studies suggest that the improved nanoporous adsorbent, evaluated under 100 mol % CO 2 at atmospheric pressure, has an equilibrium capacity of over 1.6 mmolCO 2 /g at 50°C, a two-fold increase from our previous study with a crystalline structure confirmed by XRD.10.13039/501100000266-Engineering and Physical Sciences Research Council (EPSRC), UK; 10.13039/100008475-Brunel University London, UK

A heterotic sigma model with novel target geometry

We construct a (1,2) heterotic sigma model whose target space geometry consists of a transitive Lie algebroid with complex structure on a Kaehler manifold. We show that, under certain geometrical and topological conditions, there are two distinguished topological half--twists of the heterotic sigma model leading to A and B type half--topological models. Each of these models is characterized by the usual topological BRST operator, stemming from the heterotic (0,2) supersymmetry, and a second BRST operator anticommuting with the former, originating from the (1,0) supersymmetry. These BRST operators combined in a certain way provide each half--topological model with two inequivalent BRST structures and, correspondingly, two distinct perturbative chiral algebras and chiral rings. The latter are studied in detail and characterized geometrically in terms of Lie algebroid cohomology in the quasiclassical limit.Comment: 83 pages, no figures, 2 references adde

Two-Dimensional Twisted Sigma Models, the Mirror Chiral de Rham Complex, and Twisted Generalised Mirror Symmetry

In this paper, we study the perturbative aspects of a "B-twisted" two-dimensional $(0,2)$ heterotic sigma model on a holomorphic gauge bundle $\mathcal E$ over a complex, hermitian manifold $X$. We show that the model can be naturally described in terms of the mathematical theory of ``Chiral Differential Operators". In particular, the physical anomalies of the sigma model can be reinterpreted as an obstruction to a global definition of the associated sheaf of vertex superalgebras derived from the free conformal field theory describing the model locally on $X$. In addition, one can also obtain a novel understanding of the sigma model one-loop beta function solely in terms of holomorphic data. At the $(2,2)$ locus, one can describe the resulting half-twisted variant of the topological B-model in terms of a $\it{mirror}$ "Chiral de Rham complex" (or CDR) defined by Malikov et al. in \cite{GMS1}. Via mirror symmetry, one can also derive various conjectural expressions relating the sheaf cohomology of the mirror CDR to that of the original CDR on pairs of Calabi-Yau mirror manifolds. An analysis of the half-twisted model on a non-K\"ahler group manifold with torsion also allows one to draw conclusions about the corresponding sheaves of CDR (and its mirror) that are consistent with mathematically established results by Ben-Bassat in \cite{ben} on the mirror symmetry of generalised complex manifolds. These conclusions therefore suggest an interesting relevance of the sheaf of CDR in the recent study of generalised mirror symmetry.Comment: 97 pages. Companion paper to hep-th/0604179. Published versio

Biomass Combustion Fly Ash-Derived Nanoporous Zeolites for Post-Combustion Carbon Capture

Engineering and Physical Sciences Research Council (EPSRC), UK (EP/P026214/1) UK Carbon Capture and Storage Research Centre 2017 (UKCCSRC 2017) - UKRI Energy Programme “Biomass Combustion Ash in Carbon Capture”; Brunel Research Initiative and Enterprise Fund (BRIEF)

To DoE or not to DoE? A Technical Review on & Roadmap for Optimisation of Carbonaceous Adsorbents and Adsorption Processes

Copyright © 2022 The Author(s). Design of experiment (DoE) techniques are invaluable tools which readily allow for efficient optimisation of processes via simultaneous evaluation of a combination of input parameters. Such approaches can yield positive outcomes whilst minimising the number of resources and amount of time utilised, hence, achieving a more robust approach. Additionally, when designing the experiment intelligently information about the interaction between the variables could be gathered, therefore, allowing for a more in-depth understanding of the process and identification of the “key players”. This method of conducting an experimental campaign is, unfortunately, underused (or often misused) in academia. This review aims to technically scrutinise the employment of design of experiment techniques in the context of synthesis and deployment of carbonaceous sorbents and the optimisation of the adsorption processes in both gaseous and aqueous media for environmental applications. We have also discussed how the implementation of DoE techniques in interpreting the results and the underlying trends and/or adsorption mechanisms could help with a better understanding of such observations. Additionally, a brief description of the most popular experimental design techniques with an explanation and a simple visualisation is provided. This review aims to facilitate a greater understanding and appreciation of these powerful optimisation tools, and to depict the best practices upon their employment in academic research in the field of chemical and environmental engineering.UK Engineering and Physical Sciences Research Council (EPSRC) under the project titled “Multiphysics and multiscale modelling for safe and feasible CO2 capture and storage - EP/T033940/1”, and via the UK Carbon Capture and Storage Research Centre (EP/P026214/1) through the flexible funded research programme “Techno-economics of Biomass Combustion Products in the Synthesis of Effective Low-cost Adsorbents for Carbon Capture”. The UKCCSRC is supported by the Engineering and Physical Sciences Research Council (EPSRC), UK, as part of the UKRI Energy Programme

Impact of Production Pathway on Nanoporosity of Carbonaceous Sorbents for CO2 Adsorption

Climate change requires immediate action from humanity with Carbon Capture and Storage (CCS) standing out as one of the prominent mitigation techniques. Adsorption CCS using carbonaceous nanoporous sorbents has been shown to be a promising route for industrial decarbonization. Such sorbents are often derived from organic waste, with the production pathway consisting of different steps, namely, carbonization, pelletization (with various binders) and activation. The latter two steps, however, could vary in their order, i.e. activation of the pellet versus the pelletization of the activated powder. Herein, both of these approaches have been conducted and the impact of the production pathway (as well as the presence of the binder itself) on the nano-structure of the material has been examined and compared to the “baseline-case” of the non-activated carbon (both powder and pellet). The samples were analyzed via Proximate Analysis, Fourier-Transform Infrared Spectroscopy and Scanning Electron Microscopy. CO2 adsorption was evaluated via Thermogravimetric Analysis (TGA). Further, the mechanical properties of the nanoporous pellets were studied.10.13039/501100000266-Engineering and Physical Sciences Research Council (EPSRC) UK Carbon Capture and Storage Research Centre (EP/W002841/1) through the flexible funded research programme “Investigation of Environmental and Operational Challenges of Adsorbents Synthesised from Industrial Grade Biomass Combustion Residues”; EPSRC Impact Accelerator Award (2022

Latest advances and challenges in carbon capture using bio-based sorbents: A state-of-the-art review

Copyright © 2022 The Authors. Effective decarbonisation is key to ensuring the temperature rise does not exceed the 2 °C set by the Paris accords. Adsorption is identified as a key technology for post-combustion carbon capture. This rise in prominence of such processes is owed to the fact that application of solid sorbents does not lead to the generation of secondary waste streams. In fact, sorbents can be produced from waste material (e.g. bio-based sorbents). Bio-based sorbents have become an increasingly attractive option; food waste, agricultural and municipal sources can be employed as precursors. These sorbents can be physically and chemically activated and then further modified to produce sorbents that can capture CO2 effectively. The employment of these types of sorbents, however, often entails geological and operational challenges. Understanding how these sorbents can be deployed at scale and the geological challenges associated with bio-based sorbents are key research areas that must be further investigated. Process modelling and machine learning can provide insights into these challenges especially within optimization of adsorption processes and sorbent development. This paper aims to provide a state-of-the-art review of the synthesis of bio-based sorbents and their application within post-combustion carbon capture processes as well as the recent trends of utilizing machine learning for the development of these sorbents, and the design of the corresponding adsorption processes alike.UK's Engineering and Physical Sciences Research Council (EPSRC) under the project titled “Multiphysics and Multiscale Modelling for Safe and Feasible CO2 Capture and Storage - EP/T033940/1″; UK Carbon Capture and Storage Research Centre (EP/W002841/1) through the flexible funded research programme “Investigation of Environmental and Operational Challenges of Adsorbents Synthesised from Industrial Grade Biomass Combustion Residues”

Fully Integrated Glass Microfluidic Device for Performing High-Efficiency Capillary Electrophoresis and Electrospray Ionization Mass Spectrometry

A microfabricated device has been developed in which electrospray ionization is performed directly from the corner of a rectangular glass microchip. The device allows highly efficient electrokinetically driven separations to be coupled directly to a mass spectrometer (MS) without the use of external pressure sources or the insertion of capillary spray tips. An electrokinetic-based hydraulic pump is integrated on the chip that directs eluting materials to the monolithically integrated spray tip. A positively charged surface coating, PolyE-323, is used to prevent surface interactions with peptides and proteins and to reverse the electroosmotic flow in the separation channel. The device has been used to perform microchip CE-MS analysis of peptides and proteins with efficiencies over 200 000 theoretical plates (1 000 000 plates/m). The sensitivity and stability of the microfabricated ESI source were found to be comparable to that of commercial pulled fused-silica capillary nanospray sources