11 research outputs found
Comprehensive platform for distribution transactiveenergy markets
Reducing the cost of distributed energy resources (DERs) such as renewables, storage,electric vehicles and smart loads is driving their increased connection to distributionsystems. Extracting maximum benefits from DERs require liberalising distribution sys-tems by allowing: (1) a distribution transactive energy market (DTEM) operated by alocal distribution operator (LDO) and (2) peer-to-peer (P2P), peer-to-LDO (P2LDO) andTransmission-to-LDO (T2LDO) type transactions. A DTEM will bring several benefitssuch as: (1) enhanced economic opportunity for DERs, making them more profitable and(2) increased social welfare benefiting both buyers and sellers. To achieve this objective, wedevelop a comprehensive three-phase DTEM platform that provides maximum economicopportunities for DERs and maximises social welfare that benefits all market participants,while considering P2P, P2LDO and T2LDO transactions, for both energy and ancillaryservices. Interaction between bulk electricity market independent system operator (ISO)and LDO controlled DTEM is presented. The DTEM model is implemented as a practi-cal mixed-integer linear programming formulation that includes a network reconfigurationfeature. The DTEM model is studied on three-phase 5-bus and 34-bus systems, demon-strating its effectiveness to settle energy and ancillary service transactions, while obtainingdistribution locational marginal prices. Results show that P2P transactions, when allowed,increase social welfare and increases profitability of DER
Capacity Market for Distribution System Operator – with Reliability Transactions – Considering Critical Loads and Microgrids
Conventional distribution system (DS) asset planning methods consider energy only from transmission
systems (TS) and not from distributed energy resources (DER), leading to expensive plans. Newer transactive energy DS (TEDS) asset planning models, built on capacity market mechanisms, consider energy from both TS and DERs, leading to lower-cost plans and maximizing social welfare.
However, in both methods the cost of higher reliability requirements for some users are socialized across all users, leading to lower social welfare. In this paper, a novel transactive energy capacity market (TECM) model is proposed for DS asset planning. It builds on TEDS incremental capacity auction models by provisioning for critical loads to bid and receive superior reliability as a service. The TECM model considers these reliability transactions, in addition, to selling energy transactions from
TS and DERs, buying energy transactions from loads, and asset upgrade transactions from the network operator. The TECM model allows for islanded microgrids and network reconfiguration to maximize social welfare. The TECM model is assessed on several case studies, demonstrating that
it achieves higher social welfare and a lower plan cost
Antibacterial Strategies from the Sea: Polymer-Bound Cl-Catechols for Prevention of Biofilm Formation
Inspired by the amino acid 2-chloro-4,5-dihydroxyphenylalanine (Cl-DOPA), present in the composition of the proteinaceous glue of the sandcastle worm Phragmatopoma californica, a simple strategy is presented to confer antifouling properties to polymer surfaces using (but not releasing) a bioinspired biocide. Cl-Dopamine is used to functionalize polymer materials and hydrogel films easily, to prevent biofilm formation on themThe authors thank Uwe Rietzler from the Max-Planck-Institut für Polymerforschung for the SFM-based thickness measurements
Redox Active Polymer Brushes with Phenothiazine Moieties
We have investigated two different
concepts to synthesize redox active polymer brushes using surface
initiated atomic transfer radical polymerization (SI-ATRP). This polymerization
technique allows the synthesis of well-defined grafted polymer brushes.
In the initial step the surface was functionalized with a self-assembling
monolayer of the SI-ATRP starter. Then, polymer brushes carrying phenothiazine
moieties were grafted from the surface via SI-ATRP. The first concept
consists of polymerizing monomers with phenothiazine pendant moieties
to directly incorporate the redox functionality as side group in the
growing polymer brush. The second concept consists of using grafted
activated ester brushes which are functionalized with phenothiazine
redox moieties in a successive reaction step. The electrochemical
properties of the grafted redox active brushes were examined by cyclic
voltammetry. Furthermore, the surface morphology and the chemical
composition of the polymer brushes were characterized using scanning
force microscopy (SFM), X-ray techniques, and UV/vis spectroscopy.
Apart from their redox behavior, the synthesized brushes revealed
increased mechanical stability on the nanoscale
Adsorption, Aggregation, and Desorption of Proteins on Smectite Particles
We report on adsorption of lysozyme
(LYS), ovalbumin (OVA), or
ovotransferrin (OVT) on particles of a synthetic smectite (synthetic
layered aluminosilicate). In our approach we used atomic force microscopy
(AFM) and quartz crystal microbalance (QCM) to study the protein–smectite
systems in water solutions at pH ranging from 4 to 9. The AFM provided
insights into the adhesion forces of protein molecules to the smectite
particles, while the QCM measurements yielded information about the
amounts of the adsorbed proteins, changes in their structure, and
conditions of desorption. The binding of the proteins to the smectite
surface was driven mainly by electrostatic interactions, and hence
properties of the adsorbed layers were controlled by pH. At high pH
values a change in orientation of the adsorbed LYS molecules and a
collapse or desorption of OVA layer were observed. Lowering pH to
the value ≤4 caused LYS to desorb and swelling the adsorbed
OVA. The stability of OVT–smectite complexes was found the
lowest. OVT revealed a tendency to desorb from the smectite surface
at all investigated pH. The minimum desorption rate was observed at
pH close to the isoelectric point of the protein, which suggests that
nonspecific interactions between OVT and smectite particles significantly
contribute to the stability of these complexes
Stress–Structure Correlation in PS–PMMA Mixed Polymer Brushes
The ability to alter surface properties such as morphology
and
surface energy upon external stimuli makes switchable polymer surfaces
a promising field of research. Mixed polymer brushes consisting of
two different homopolymers covalently attached to a surface are one
system in which surface properties can be switched. In this work the
correlation between the change in structure and the resulting surface
stress in thin poly(methyl methacrylate)–polystyrene mixed
polymer brush film upon exposure to selective solvents is investigated.
By measuring the forces acting inside the film, we are able to achieve
a deeper understanding of the observed structural changes. To obtain
a thorough understanding of the film’s morphology, the structure
is analyzed by scanning probe microscopy, X-ray reflectivity, and
grazing incidence small-angle X-ray scattering (GISAXS). Upon exposure
to acetic acid, a selective solvent for PMMA, the film showed a dimple-like
structure. This is linked to collapsed domains of polystyrene covered
by PMMA chains. Bending experiments resulted in tensile stress, pointing
to attractive forces acting inside the polymer film. After exposure
to dichloromethane, a good solvent for both polymers, bending experiments
revealed a decreased but still high tensile stress, indicating that
the microdomains are still present. The results of the experiments
enable us to further explain the domain memory effect typically found
in these kinds of mixed polymer brush systems
BJS commission on surgery and perioperative care post-COVID-19
Background: Coronavirus disease 2019 (COVID-19) was declared a pandemic by the WHO on 11 March 2020 and global surgical practice was compromised. This Commission aimed to document and reflect on the changes seen in the surgical environment during the pandemic, by reviewing colleagues experiences and published evidence. Methods: In late 2020, BJS contacted colleagues across the global surgical community and asked them to describe how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had affected their practice. In addition to this, the Commission undertook a literature review on the impact of COVID-19 on surgery and perioperative care. A thematic analysis was performed to identify the issues most frequently encountered by the correspondents, as well as the solutions and ideas suggested to address them. Results: BJS received communications for this Commission from leading clinicians and academics across a variety of surgical specialties in every inhabited continent. The responses from all over the world provided insights into multiple facets of surgical practice from a governmental level to individual clinical practice and training. Conclusion: The COVID-19 pandemic has uncovered a variety of problems in healthcare systems, including negative impacts on surgical practice. Global surgical multidisciplinary teams are working collaboratively to address research questions about the future of surgery in the post-COVID-19 era. The COVID-19 pandemic is severely damaging surgical training. The establishment of a multidisciplinary ethics committee should be encouraged at all surgical oncology centres. Innovative leadership and collaboration is vital in the post-COVID-19 era
BJS commission on surgery and perioperative care post-COVID-19
Coronavirus disease 2019 (COVID-19) was declared a pandemic by the WHO on 11 March 2020 and global surgical practice was compromised. This Commission aimed to document and reflect on the changes seen in the surgical environment during the pandemic, by reviewing colleagues' experiences and published evidence