Hasil untuk "Systems engineering"

D. Sculley, Gary Holt, D. Golovin et al.

Xiaolei Yin, Benjamin E. Mead, Helia Safaee et al.

J. Zurada

R. Dorf, Naresh K. Sinha

Scott Fogler

P. Checkland

D. Hutmacher, M. Sittinger, M. Risbud

S. Brinkkemper

G. Tchobanoglous, F. L. Burton

J. Nocedal, Stephen J. Wright

R. Billinton, R. Allan

R. D. Lemos, H. Giese, H. Müller et al.

Yuko T. Sato, Kaori Umezaki, S. Sawada et al.

Exosomes are a valuable biomaterial for the development of novel nanocarriers as functionally advanced drug delivery systems. To control and modify the performance of exosomal nanocarriers, we developed hybrid exosomes by fusing their membranes with liposomes using the freeze–thaw method. Exosomes embedded with a specific membrane protein isolated from genetically modified cells were fused with various liposomes, confirming that membrane engineering methods can be combined with genetic modification techniques. Cellular uptake studies performed using the hybrid exosomes revealed that the interactions between the developed exosomes and cells could be modified by changing the lipid composition or the properties of the exogenous lipids. These results suggest that the membrane-engineering approach reported here offers a new strategy for developing rationally designed exosomes as hybrid nanocarriers for use in advanced drug delivery systems.

Jeong Wook Lee, D. Na, J. Park et al.

B. Knott, E. Erickson, Mark D. Allen et al.

Significance Deconstruction of recalcitrant polymers, such as cellulose or chitin, is accomplished in nature by synergistic enzyme cocktails that evolved over millions of years. In these systems, soluble dimeric or oligomeric intermediates are typically released via interfacial biocatalysis, and additional enzymes often process the soluble intermediates into monomers for microbial uptake. The recent discovery of a two-enzyme system for polyethylene terephthalate (PET) deconstruction, which employs one enzyme to convert the polymer into soluble intermediates and another enzyme to produce the constituent PET monomers (MHETase), suggests that nature may be evolving similar deconstruction strategies for synthetic plastics. This study on the characterization of the MHETase enzyme and synergy of the two-enzyme PET depolymerization system may inform enzyme cocktail-based strategies for plastics upcycling. Plastics pollution represents a global environmental crisis. In response, microbes are evolving the capacity to utilize synthetic polymers as carbon and energy sources. Recently, Ideonella sakaiensis was reported to secrete a two-enzyme system to deconstruct polyethylene terephthalate (PET) to its constituent monomers. Specifically, the I. sakaiensis PETase depolymerizes PET, liberating soluble products, including mono(2-hydroxyethyl) terephthalate (MHET), which is cleaved to terephthalic acid and ethylene glycol by MHETase. Here, we report a 1.6 Å resolution MHETase structure, illustrating that the MHETase core domain is similar to PETase, capped by a lid domain. Simulations of the catalytic itinerary predict that MHETase follows the canonical two-step serine hydrolase mechanism. Bioinformatics analysis suggests that MHETase evolved from ferulic acid esterases, and two homologous enzymes are shown to exhibit MHET turnover. Analysis of the two homologous enzymes and the MHETase S131G mutant demonstrates the importance of this residue for accommodation of MHET in the active site. We also demonstrate that the MHETase lid is crucial for hydrolysis of MHET and, furthermore, that MHETase does not turnover mono(2-hydroxyethyl)-furanoate or mono(2-hydroxyethyl)-isophthalate. A highly synergistic relationship between PETase and MHETase was observed for the conversion of amorphous PET film to monomers across all nonzero MHETase concentrations tested. Finally, we compare the performance of MHETase:PETase chimeric proteins of varying linker lengths, which all exhibit improved PET and MHET turnover relative to the free enzymes. Together, these results offer insights into the two-enzyme PET depolymerization system and will inform future efforts in the biological deconstruction and upcycling of mixed plastics.

Jeryang Park, T. Seager, P. Rao et al.

Rashidah Kasauli, E. Knauss, J. Horkoff et al.

Abstract Context: Agile methods have become mainstream even in large-scale systems engineering companies that need to accommodate different development cycles of hardware and software. For such companies, requirements engineering is an essential activity that involves upfront and detailed analysis which can be at odds with agile development methods. Objective: This paper presents a multiple case study with seven large-scale systems companies, reporting their challenges, together with best practices from industry. We also analyze literature about two popular large-scale agile frameworks, SAFe® and LeSS, to derive potential solutions for the challenges. Methods: Our results are based on 20 qualitative interviews, five focus groups, and eight cross-company workshops which we used to both collect and validate our results. Results: We found 24 challenges which we grouped in six themes, then mapped to solutions from SAFe®, LeSS, and our companies, when available. Conclusion: In this way, we contribute a comprehensive overview of RE challenges in relation to large-scale agile system development, evaluate the degree to which they have been addressed, and outline research gaps. We expect these results to be useful for practitioners who are responsible for designing processes, methods, or tools for large scale agile development as well as guidance for researchers.

Mumtaz Manzoor, Ali B. M. Ali, Ramesh Sharma et al.

Abstract This study presents a comprehensive first-principles investigation of the structural, mechanical, electronic, optical, thermoelectric, and thermodynamic properties of half-Heusler PtTiZ (Z = Ge, Pb) compounds using the full-potential linearized augmented plane-wave (FP-LAPW) method combined with semiclassical Boltzmann transport theory. Exchange–correlation effects were treated within the LDA, PBE-GGA, and Tran–Blaha modified Becke–Johnson (TB-mBJ) schemes to achieve accurate electronic descriptions. Both alloys crystallize in a stable cubic F-43 m structure and exhibit indirect semiconducting behavior with band gaps of 0.66 eV (PtTiGe) and 0.387 eV (PtTiPb). The density-of-states analysis indicates that the valence region is dominated by Ti-3d and Z-p hybridized states, confirming strong p–d interactions. Mechanical stability criteria and positive elastic constants verify that both compounds are mechanically robust, with PtTiGe being stiffer and harder than PtTiPb. Optical results reveal pronounced absorption and high optical conductivity in the ultraviolet region, suggesting potential for optoelectronic applications. Thermoelectric analysis demonstrates p-type character with Seebeck coefficients of 229.21 µV K⁻¹ (PtTiGe) and 236.21 µV K⁻¹ (PtTiPb) at 300 K, and 235.05 µV K⁻¹ and 237.31 µV K⁻¹ at 1200 K, respectively. The corresponding lattice thermal conductivities decrease to 0.45 W m⁻¹ K⁻¹ and 0.32 W m⁻¹ K⁻¹, yielding maximum dimensionless figures of merit (ZT) of 0.68 and 0.70 at 1200 K. Thermodynamic results confirm that the Debye temperature increases with pressure while heat capacity decreases, ensuring stability at elevated conditions. Overall, the synergistic combination of electronic tunability, optical responsiveness, and favorable thermoelectric performance highlights PtTiZ (Z = Ge, Pb) as promising candidates for high-temperature thermoelectric and ultraviolet-optoelectronic applications.

Yuta Shimizu, Hideaki Miyamoto, Patrick Michel

Abstract Asteroids preserve a continuous record of evolutionary processes since the early solar system. They can take various shapes that represent the cumulative results of their evolution. However, for those showing common characteristics, this does not mean that they followed the same evolutionary path. Here, we show that (101955) Bennu and (162173) Ryugu, two near-Earth asteroids with spheroidal shapes, have evolved through distinct pathways despite their similar shapes. Using high-resolution imagery from NASA’s OSIRIS-REx and JAXA’s Hayabusa2 spacecraft, we map ~ 200,000 boulders and find latitudinal particle size sorting on both bodies. This represents opposite directions of surface material movements driven by their different rotation periods (4.3 h for Bennu and 7.6 h for Ryugu): toward the equator on Bennu and toward the poles on Ryugu. Furthermore, the spatial distribution of large boulders on Bennu suggests a prior slower rotation (> 5 h), implying a past shape evolution similar to that of Ryugu. Our findings demonstrate that small variations in rotation period, on the scale of a few hours, can drastically change the gravitational field on an asteroid, sometimes even reversing local gravity direction. This drives complex and diverse evolutionary pathways of asteroids, resulting in top-shaped bodies and binary systems observed today.

Asadullah Shaikh, Wahidur Rahman, Kaniz Roksana et al.

Bangladesh has plentiful water, which is essential to its freshwater fish traditions. Environmental concerns and other causes have reduced the country's water resources, threatening many native freshwater fish species. Thus, the younger generation deficiencies recognition of local freshwater fish and struggles to recognize them. Traditional methods are very insufficient to overcome these issues. To address these research gaps, the research proposes an automatic system for categorizing Bangladesh's freshwater fish. The proposed methodology involves several key steps, including building a comprehensive dataset, extracting features from fish images using pre-trained Convolutional Neural Network (CNN) models, and employing typical ML approaches. Initially comprising eight classes, the dataset undergoes feature extraction using CNN algorithms, followed by the utilization of various feature selection methods such as Support Vector Classifier, Principal Component Analysis, Linear Discriminant Analysis, and optimization models like Particle Swarm Optimization, Bacterial Foraging Optimization, and Cat Swarm Optimization. In the final phase, seven conventional ML techniques are applied to classify the images of local fishes. Empirical measurements are gathered and analyzed to assess the proposed framework's performance. Particularly, the present approach achieves the highest accuracy of 98.71% through the utilization of the ML mechanism Logistic Regression with Resnet50, SVC, and CSO models.