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Effect of unidirectional airflow ventilation on surgical site infection in cardiac surgery: environmental impact as a factor in the choice for turbulent mixed air flow
No full textBackground: Surgical site infection (SSI) in the form of postoperative deep sternal wound infection (DSWI) after cardiac surgery is a rare, but potentially fatal, complication. In addressing this, the focus is on preventive measures, as most risk factors for SSI are not controllable. Therefore, operating rooms are equipped with heating, ventilation and air conditioning (HVAC) systems to prevent airborne contamination of the wound, either through turbulent mixed air flow (TMA) or unidirectional air flow (UDAF). Aim: To investigate if the risk for SSI after cardiac surgery was decreased after changing from TMA to UDAF. Methods: This observational retrospective single-centre cohort study collected data from 1288 patients who underwent open heart surgery over 2 years. During the two study periods, institutional SSI preventive measures remained the same, with the exception of the type of HVAC system that was used. Findings: Using multi-variable logistic regression analysis that considered confounding factors (diabetes, obesity, duration of surgery, and re-operation), the hypothesis that TMA is an independent risk factor for SSI was rejected (odds ratio 0.9, 95% confidence interval 0.4–1.8; P>0.05). It was not possible to demonstrate the preventive effect of UDAF on the incidence of SSI in patients undergoing open heart surgery when compared with TMA. Conclusion: Based on these results, the use of UDAF in open heart surgery should be weighed against its low cost-effectiveness and negative environmental impact due to high electricity consumption. Reducing energy overuse by utilizing TMA for cardiac surgery can diminish the carbon footprint of operating rooms, and their contribution to climate-related health hazards.Medical Instruments & Bio-Inspired Technolog
Performance and microbial community composition of full-scale high-rate cascade sludge digestion system via pie-shaped reactor configuration
No full textA full-scale high-rate cascade anaerobic digestion (CAD) system was evaluated for its ability to enhance enzymatic sludge hydrolysis. The system included a newly built digester, innovatively divided into three pie-shaped compartments (500 m3 each), followed by an existing, larger digester (1500 m3). The system treated a mixture of waste activated sludge and primary sludge, achieving a stable total chemical oxygen demand reduction efficiency (56.1 ± 6.8 %), and enhanced sludge hydrolytic enzyme activities at a 14.5-day total solids retention time (SRT). High-throughput sequencing data revealed a consistent microbial community across reactors, dominated by consortia that govern hydrolysis and acidogenesis. Despite relatively short SRTs in the initial reactors of the CAD system, acetoclastic methanogens belonging to Methanosaeta became the most abundant archaea. This study proves that the CAD system achieves stable sludge reduction, accelerates enzymatic hydrolysis at full-scale, and paves the way for its industrialization in municipal waste sewage sludge treatment.Sanitary EngineeringWater Managemen
Community Participation in Urban Land and Housing Delivery: Evidence from Kerala (India) and Dar es Salaam (Tanzania)
No full textCurrent approaches to the provision of shelter, largely driven by national governments and/or the commercial private sector, continue to fall short of what is needed to reduce housing deficits. The number of people without access to adequate housing continues to grow, especially in cities of the Global South. Increasing attention is being paid to alternative models for organizing land and housing delivery, such as those led by, or at least including, civil society. In this paper, we consider two national land and housing programs—the 20,000 Plots Project in Tanzania, and Basic Services for the Urban Poor (BSUP) in India—alongside community-led housing initiatives from each country. We explore the extent to which community participation in housing delivery can have social and environmental advantages when compared to ‘business as usual’ methods and find that, given appropriate state support, community-based, and civil society actors (including organizations of the urban poor) have significant potential to contribute to acquiring land, building homes and improving the quality of life of vulnerable segments of the population. This paper echoes calls for community-led housing to become a recognized part of formal housing policy whilst emphasizing the need for theoretical refinement of the process so as to prevent it from being captured by prevailing market-led narratives.Urban Development Managemen
The Leaky Cauldron: An experimental study of the icy plumes of Enceladus
No full textThe discovery of vast subsurface oceans hidden under kilometers of ices on icy moons in our Solar System has sparked worldwide interests in ascertaining their potential habitability. In the case of Saturn’s moon Enceladus, supersonic plumes of water vapour and icy grains have been observed by the Cassini mission spewing from the surface, giving us indirect knowledge of the composition of this subsurface ocean. The exact mechanisms of the plumes however, and their effect on the composition of the ejected matter has yet to be clearly understood. The focus of this study is to experimentally investigate physical characteristics of the plumes located at the South Polar Terrain (SPT) of Enceladus. Using facilities at TU Delft faculty, we simulate experimentally the topology of the ice crevasses and the subsurface ocean with a narrow channel mounted atop a liquid water reservoir placed inside a vacuum chamber. We inquire upon the dependence of the channel walls temperature on the plume’s exhaust velocity. Using a straight channel, our results show that colder wall temperatures enable a saturated water vapour flow with a minima 1.5-3 % solid fraction and vent velocities reaching around 400-500 m/s. The data ranges for velocities and solid fraction extrapolated from the Cassini data (550-2000 m/s and 7-70 %) thus cannot be explained by straight channel models. Using a channel with an expansion ratio of 1.73 however, the measured supersonic plume velocity becomes comparable to some of the in situ Mach number determined at Enceladus. Using a method based on the energy conservation law, it is possible to extrapolate from our experimental data some plausible geometries of the ice crevasses of Enceladus. This work lays the ground work for a coming comprehensive parametric study of the channel geometry and its effect on exhaust Mach number, temperature and solid fraction.Planetary ExplorationAerodynamic
Impact of Model Selection and Conformational Effects on the Descriptors for In Silico Screening Campaigns: A Case Study of Rh-Catalyzed Acrylate Hydrogenation
No full textData-driven catalyst design is a promising approach for addressing the challenges in identifying suitable catalysts for synthetic transformations. Models with descriptor calculations relying solely on the precatalyst structure are potentially generalizable but may overlook catalyst-substrate interactions. This study explores substrate-specific interactions in the context of Rh-catalyzed asymmetric hydrogenation to elucidate the impact of substrate inclusion on the catalyst structure and on the descriptors derived from it. We compare a catalyst-substrate complex with methyl 2-acetamidoacrylate as a model substrate with the generic precatalyst structure involving a placeholder substrate, norbornadiene, across 11 Rh-based catalysts with bidentate bisphosphine ligands. For these systems, a full conformer ensemble analysis reveals an intriguing finding: the rigid substrate induces conformational freedom in the ligand. This flexibility gives rise to a more diverse conformer landscape, showing a previously overlooked aspect of catalyst-substrate dynamics. Electronic descriptor variations particularly highlight differences between substrate-specific and precatalyst structures. This study suggests that generic precatalyst-like models may lack crucial insights into the conformational freedom of the catalyst. We speculate that such conformational freedom may be a more general phenomenon that can influence the development of generalizable predictive models of computational TM-based catalysis.ChemE/Inorganic Systems Engineerin
Registration of apartments and office spaces in 3D land administration: A case study in Croatia
No full textDue to the needs of modern society, cadastral systems should be designed to support three dimensional (3D) spatial data. One of many possible approaches for implementing a 3D cadastre, in countries such as Croatia, is to establish a Building Register as a transitional register between 2D and 3D cadastres, where data about buildings and infrastructure would be collected, gradually adapted to the data model of 3D cadastre, and finally migrated to the 3D cadastre database. Sources for establishing the Building Register can be based on the records of state surveys, the register of administrative units, the land book, data managed by local and regional self-government units, data from construction documentation according to special regulations in the field of spatial planning, data managed by the building and infrastructure managers, as well as from other sources. A significant element of the 3D cadastre would be the inclusion of representations of buildings and units of use, as well as public utility infrastructure and complex spatial real-life entities (e.g., bridges, tunnels, overpasses, underpasses, overlapping of constructed objects with natural facilities, large shopping malls with more underground and overhead floors etc.). This paper presents a conceptual model of a 3D cadastre in Croatia by establishing the Building Register with focus on unit of use of real properties, namely apartments and office spaces. The paper also summarizes the current situation regarding the Croatian Land Administration System (LAS) and proposes a conceptual model for modelling unit of use of real properties. Additionally, a proposal is made herein to assign unique identifiers to buildings and their parts in a logical manner which would be intuitive and clear to citizens of Croatia, citizens of European Union and citizens of Croatia neighboring countries. The proposed methodology of determining unique identifiers could provide the means for easier navigation in 3D space and better understanding of spatial information by lay citizens, by institutions or emergency services.Digital Technologie
Binary Deep Learning: Binary Weights and Semantic Binary Data Compression
No full textImproving the efficiency in deploying deep neural networks (DNNs) and processing complex high-dimensional data has drawn increasing attention in recent years. Yet, the deployment of large DNN models is challenged by the high computational complexity and energy consumption, making it difficult to run on resource-constrained devices such as mobile phones. Moreover, the exploding amount of high-dimensional data requires large storage and transmission capacities which is infeasible to be processed on mobile devices.To alleviate these limitations, this dissertation focuses on binarization techniques, including model binarization and data binarization, to improve the efficiency in terms of storage, computation and energy.In model binarization, we binarize both the weight and activation of DNN models which can reach up to 32× memory saving and a speed up of 58×. We also develop pruning algorithms to further compress the binarized network while maintaining accuracy. To efficiently train the binarized networks, we discover new optimization methods that has less hyper-parameters and can improve the accuracy.In data binarization, we propose deep hashing algorithms that learn smaller binary data representation. Deep hashing methods have become an effective technique for fast and efficient similarity search and retrieval of high-dimensional data items in large databases.Pattern Recognition and Bioinformatic
Developing a decision support tool for the operation of parallel AS/RS during partial downtime: A case study at Jumbo Supermarkets
No full textThis paper investigates the optimisation of Automated Storage and Retrieval Systems (AS/RS) in warehousing by minimising performance losses during partial downtime. Given the increasing automation in logistics, AS/RS systems play a pivotal role, yet the operation of those systems during partial downtime remains a topic ignored in literature. This research fills this gap by exploring the effects of partial downtime in AS/RS through a reusable Discrete Event Simulation model which was developed in Python. This model incorporates the influence of both upstream and downstream systems, a characteristic notably absent from the limited number of publicly-available AS/RS models. Collaborating with Jumbo Supermarkets, the study utilises their highly automated distribution centre with an Order Consolidation Buffer housing 4 dual-crane AS/RS units as a case study. The study identifies operational policies to mitigate partial downtime effects, developed for scenarios with one or both cranes down within an AS/RS. Results suggest strategic workload distribution adjustments among AS/RS can significantly reduce performance degradation, particularly during high workload periods. After comparing both scenarios, it was concluded that for most scenarios, it is beneficial to keep operating the remaining crane when a crane breaks down, even though this slows down repairs. Overall, this research offers insights into parallel AS/RS dynamics under partial downtime and provides practical guidelines for effective operations.Mechanical Engineering | Multi-Machine Engineerin
A Street View of Groundwater Policymaking and Management in Azraq, Jordan
No full textGroundwater management is a complex task that includes a multitude of actors. It is even more complicated in water scarce countries with less well-established formal water governance structures. In these settings, local government officers have been recognised for their essential role in groundwater management. Often, their role is described as problematic, with officers being under-resourced, under-motivated and, at times, corrupt. In this paper we zoom in on these street-level bureaucrats in Azraq, one of the most depleted groundwater basins in Jordan. Based on inputs from officers, farmers, and sector experts, we collate and analyse information on how the settings in which local officers work influence their day-to-day implementation of policies. We observe that officers in Azraq are heavily influenced by the context in which they operate. This context is characterised by the physical scarcity of groundwater, the formal policy setting, and the presence of the shadow state. The context shapes local officers’ relationships with farmers, their own personal beliefs and subjectivities, and their capacity and resources. As a result, their divergent actions arguably become the groundwater management policy. Based on these findings, we argue that a deeper understanding is needed of the underlying factors and drivers that shape local groundwater management if we are to arrive at better groundwater policy for a more sustainable future.Policy AnalysisWater Managemen
Introducing a Novel Concept for an Integrated Demolition Waste Recycling Center and the Establishment of a Stakeholder Network: A Case Study from Germany
No full textUsing recycled aggregates has many positive environmental impacts because of the conservation of natural resources and minimization of waste. The use of recycled aggregates in downcycling processes is already common in Germany, whereas utilizing them to produce high-quality recycled concrete is rarely applied in practice. The reasons behind this lag have been investigated based on surveys and interviews with stakeholders. Miscommunication and missing information were identified in all stakeholder groups. Therefore, establishing a robust network and facilitating knowledge transfer by specifying the demand for recycled aggregates in the case study region have been considered as prerequisites. Therefore, the paper presents a novel concept of a stakeholder network for an integrated construction and demolition waste center. The conceptualization integrates the recycling companies and construction product manufacturers in one venue with research, service, and educational divisions. The design of the facilities is based on calculations regarding future construction activities and the demand for concrete production. The proposed concept aims to supply the region in the west of Germany with high-quality recycled products while also establishing a robust network that offers benefits in terms of logistical optimization and knowledge transfer.Architectural Technolog