Cassette Structure Research Articles

Delayed-focus micro-angle measurement optical system based on structural segregation

In this paper, we propose a delayed-focusing type micro-angle measurement optical system based on the Cassegrain structure (cassette structure), analyze the basic cassette structure and the Galilean laser beam expanding system, and determine the primary and secondary mirror structure as a reflective focusless system as a determining module. This focusless system emits and receives parallel light, and the light source and detector separated by the beam splitter are designed as replaceable modules. Additionally, the imaging quality of the system can be optimized, or the effect of meeting different imaging requirements can be achieved, by changing the number and type of corrective mirrors and the parameters of the specific glass elements in the replaceable modules. After the final optimization, the radius of the imaging spot of the combined mirror group can be limited to 6.1 µm; the modulation transfer function is better than 0.6 at 100 lp/mm; the difference between the meridian and the arc-vector curves is less than 0.1; and the theoretical angular accuracy reaches 0.2″. The delayed-focusing system structure is analyzed under different temperature fields to provide guidance for the design of the subsequent structure temperature control. Comparison and analysis with commonly used angle measurement optical systems are also made. It is concluded that the structure meets the requirements for use in the on-orbit environment, completes the reuse of the established structural modules, and further saves the manufacturing cost, which provides a feasible solution to the problem of monitoring the small angular changes in the field of space.

Staphylococcal Resistance Patterns, blaZ and SCCmec Cassette Genes in the Nasopharyngeal Microbiota of Pregnant Women.

Antimicrobial resistance in Staphylococcus spp. colonising the nasopharynx can create risk factors of therapeutic treatment failure or prophylaxis in pregnant women. Resistance is mostly encoded on plasmids (e.g., blaZ gene for penicillinase synthesis) or chromosomes (e.g., mecA and mecC for methicillin resistance). The mecA gene is part of the chromosomal mec gene cassette (SCCmec), which is also located on the plasmid. The disc diffusion method for the selected drugs (beta-lactams, fluoroquinolones, streptogramins, aminoglicosides, macrolides, oxasolidinones, tetracyclines and other groups) was used. PCR for blaZ, mecA and mecC genes and SCCmec cassette detection and typing were performed. S. aureus (54.4%) and S. epidermidis (27.9%) were the most prevalent and showed the highest diversity of resistance profiles. The blaZ, mecA and mecC genes were reported in 95.6%, 20.6% and 1.5% of isolates, respectively. The highest resistance was found to beta-lactams, commonly used during pregnancy. Resistance to a variety of antimicrobials, including benzylpenicillin resistance in blaZ-positive isolates, and the existence of a very high diversity of SCCmec cassette structures in all staphylococci selected from the nasopharyngeal microbiota of pregnant women were observed for the first time. Knowledge of the prevalence of antimicrobial-resistant staphylococci in the nasopharynx of pregnant women may be important for the appropriate treatment or prophylaxis of this group of patients.

High-speed multi-camera 3D DIC measurement of the deformation of cassette structure with large shaking table

Vision-based deformation measurement methods have been proposed to overcome the disadvantages of laborious, time-consuming measurement data that are difficult to accurately obtain using contact sensors in three directions. However, such methods remain a challenge for large-scale applications owing to difficulties in full-field imaging, stereo calibration, and measurement resolution, among other factors. To the best of our knowledge, there are no reports on the three-dimensional (3D) full-field measurement of a large shaking table structure with multiple cameras. In this paper, a multi-camera 3D DIC method using four high-speed cameras to measure the multi-layer structure model in a shaking table is proposed. To calibrate the stereo cameras with a large field of view, a speckle-based calibration method and a coordinate system unification method are proposed. The implementation of the proposed method is illustrated with a shaking table test for a 1/8 scaled 15-story high-rise cassette concrete structure with several different intensity levels of ground motions. The results of displacement, velocity, and acceleration of the structure measured using the proposed method correspond well with those of a laser displacement meter and accelerometer. The experiment results show that this method can guarantee full-field measurements in the range of tens of square meters and realize a sub-millimeter displacement measurement accuracy. They also indicate that the proposed multi-camera 3D DIC method has high potential for understanding the failure mechanism of structures and improving the structural design.

Probabilistic Seismic Capacity Analysis of a Novel Mid-rise Large-span Cassette Structure Using Multidirectional Pushover Method

ABSTRACT This paper investigates a novel mid-rise large-span cassette structure. The unique limit state divisions of the cassette structure are studied by following the probabilistic seismic capacity analysis (PSCA) method. A numerical model is established and verified through the use of shake table test results. Multidirectional pushover analyses is performed, and the directional effect of the 3D cassette structure is considered. The uncertainty present in fourteen major structural parameters is also considered in the modelling by using Latin hypercube sampling (LHS). The probability density function (PDF), cumulative distribution function (CDF), coefficient of variability (COV) and PSCA curves are obtained. The probabilistic distributions of the PSCA curves suggest that the threshold values of the maximum storey drift ratios of the large-span cassette are 1/550, 1/200, 1/60, and 1/25 for the slight damage (SD), moderate damage (MD), extensive damage (ED) and complete damage (CD) limit states, respectively. Furthermore, the average median values and logarithmic standard deviations are also given for the further probabilistic seismic fragility analysis and structural assessment performed. Finally, sensitivity analyses are conducted to examine the effects of critical structural parameters on structural damage measures. The results show that the structural performance is more sensitive to material parameters than load parameters.

Probabilistic seismic demand and fragility analysis of a novel mid-rise large-span cassette structure

Probabilistic seismic demand and fragility analysis of a novel mid-rise large-span cassette structure

Shaking table test and evaluation of a novel high-rise large span concrete cassette structure

This paper discusses the seismic performance of a novel high-rise large span concrete cassette structure based on shaking table tests and finite element models (FEMs). A 1/8 scaled 15-story high-rise concrete cassette model structure was established, and a shaking table test was conducted. Seven different intensity levels of ground motions were used based on the design spectra, and the overall performance of the structure, including the story drift ratio, roof displacement, acceleration-amplification coefficient and failure mode, was studied. During the test, the cassette structure showed a good seismic performance, and the structural integrity was maintained even under the ultimate large ground motion. After the test, the structure was free from collapse, and obvious damages could be found only in three stories. Afterwards, a comparison study was conducted between the cassette structure and a frame structure through the FEM, and based on the test and simulation results, the cassette structure exhibited better seismic performance and architectural function. Finally, design recommendations were proposed based on the test and simulation results.

Desulfurization of Automotive Fuels by the Adsorption Method Using Adsorbents of Natural Origin

The article presents the results of an experimental study of the application of the adsorption method for removing sulfur and sulfur-containing components from automobile fuels using sorbents of natural origin, assembled in the form of a cassette structure.

Superhydrophobic Copper Foam Modified with n-Dodecyl Mercaptan-CeO2 Nanosheets for Efficient Oil/Water Separation and Oil Spill Cleanup

Efficient separation of oil/water with a simple and low-cost method is of great importance for the treatment of oily wastewater. In the current study, a facile one-step electrodeposition method was used to fabricate highly dense CeO₂ nanostructures on copper foam at a constant current density of 1.5 mA·cm–² for 20 min, which exhibited excellent superhydrophobicity and superlipophilicity after surface modification with n-dodecyl mercaptan (NDM). The electrodeposition current density and time were systematically investigated to uncover influencing factors of the growth process of CeO₂ nanostructures on the copper foam. The as-fabricated superhydrophobic foams could not only be used to efficiently separate oil/water mixtures with a separation efficiency greater than 97.4% but also presented robustness and high stability against 3.5 wt % NaCl solution and 600-grit sandpaper abrasion. Furthermore, the as-prepared sample still maintains a high separation efficiency at circa 97.5% after more than 25 times of recovery for kerosene/water mixture separation. In addition, the as-prepared three-dimensional cassette structure made of superhydrophobic copper foam could float freely on the water surface for fast in situ collection of oil from the water surface, indicating application potential in offshore oil spill treatment and cleanup.

Seismic and economic performance of a mid-rise cassette structure

In this article, a new structure called cassette structure is presented. A comparative analysis of seismic and economic performance of a cassette structure and a frame structure is conducted. An existing frame office building is selected and redesigned as a cassette structure to compare the performance of the two kinds of structures. Three-dimensional finite element models are built for the two prototype structures, where fiber elements are used to simulate plastic behavior. To assess the advantages fully, seismic analysis and economic analysis are performed. Eighteen Federal Emergency Management Agency recommended seismic records are used, and the roof displacement, story drift ratio, plastic hinges development, and Park–Ang damage index are compared. Furthermore, the material, template, transportation, and assembling costs are calculated based on Chinese quotas, and the overall economic impact is evaluated. In this case, all indexes show that the cassette structure has an obvious advantage over conventional frame structure.

Seismic Performance and Design Process Majorization of a Reinforced Concrete Grid Frame Wall

ABSTRACT This paper presents a new structure, called a cassette structure, and the modified design method of its core vertical elements, called a grid frame wall, is proposed. The advantages, mechanical properties and performances of the original grid frame wall are introduced, and its weaknesses are discussed based on practical engineering buildings and cycling load tests. To improve the structural performance, the modified design method considering the relative rotation and shear effect in beam-column joints is proposed and then verified through a theoretical analysis and numerical study. The detailed design process is given, and the adjusting coefficient αc and assessing coefficient ω are used. Furthermore, a practical engineering building is used to exam the effectiveness of the newly designed method, where time history analyses are used under the design basis earthquake (DBE) and maximum considered earthquake (MCE) levels. Finally, the IDA and a fragility analysis are conducted to give a full analysis of the newly designed grid frame wall. The newly designed grid frame wall performed well in all the above-mentioned studies.

Application and Analyzation of the Vision‐Based Structure Model Displacement Measuring Method in Cassette Structure Shaking Table Experiment

In the shaking table test of large cassette structure, story drift is an essential set of experimental data. The traditional method of displacement measurement is limited to problems such as necessary full contact with the structure model for installation of sensors, large work of installation, and easily interfered by environment. The noncontact displacement measurement method, such as optical measuring technology, can solve the above problems and serve as an effective supplementary method for traditional displacement measuring in the shaking table test. This paper proposed a vison‐based displacement measuring method. Predesigned artificial targets which act as sensors are installed on each floor of the cassette structure model. A high‐speed industrial camera is used to acquire the series of the images of the artificial targets on the structure model during the shaking table test. A Python‐OpenCV‐based structural calculation program combining computer vision and machine vision is developed to extract and calculate the displacement of the artificial targets from the series of the images acquired. The proposed method is applied in a shaking table test of a reduced‐scale fifteen‐floor reinforced concrete cassette structure model, in which the laser displacement meter and the seismic geophone are also applied as a comparison. The experimental results acquired by the proposed method are compared with the results acquired by the laser displacement meter and the seismic geophone. The average error of the story drift obtained by the proposed vision‐based measurement method is within 5% and is in good agreement with the laser displacement meter and the seismic geophone, which confirms the effectiveness of the proposed method.

Consistent Production of Mice with Conditional Knockout Alleles by CRISPR/Cas9-Mediated Genome Editing Using Two Guides/Two Oligos Approach

Gene targeting is extensively used to generate designer mouse mutants and to study gene function in vivo. Knockout mice that harbor a null allele in their germline provide appropriate genetic models of inherited diseases and often exhibit embryonic or early postnatal lethality. To study gene function in adult mice and in selected cell types, a refined strategy for conditional gene inactivation has been developed that relies on the DNA recombinase Cre and its recognition (loxP) sites. This process has traditionally relied on the complex process involving genome editing in embryonic stem (ES) cells despite its limitations, including incorrect targeting or cassette structure, and difficulties with germline transmission of the allele from chimeric mice. CRISPR-Cas9 gene editing technology has considerably facilitated the generation of mouse knockout alleles, relieving many of the cumbersome and time-consuming steps of traditional mouse ES cell technology. However, the generation of conditional knockout alleles remains an important challenge. An earlier study reported up to 16% efficiency in generating conditional knockout alleles in mice using 2 single guide RNAs (sgRNA) and 2 single-stranded oligonucleotides (ssODN), which has been questioned by another report combining data from multiple transgenic cores. With the advent of CRISPR/Cas9 as a mouse genome modification tool, we assessed the efficiency of using this method in creating conditional targeted alleles in three genes, phosphatase and actin regulator 1 (Phactr1), apolipoprotein A-I (ApoA1), and actin-related protein T2 (Actrt2). Even though overall success rate was low—about 2.5%—we show that it’s possible to reliably generate conditional knockout alleles using CRISPR/Cas9 on a consistent basis.

Occurrence of intI1-associated VIM-5 carbapenemase and co-existence of all four classes of β-lactamase in carbapenem-resistant clinical Pseudomonas aeruginosa DMC-27b.

Emergence of carbapenem-resistant Pseudomonas aeruginosa is limiting current treatment options. Carbapenemases and their association with integrons can cause rapid dissemination of resistance traits. We report here the co-existence and chromosomal inheritance of all four classes of β-lactamase and the presence of a unique class 1 integron (intI1) harbouring blaVIM-5 within a single isolate of P. aeruginosa, DMC-27b. DMC-27b, isolated from urine, was characterized for carbapenem resistance both phenotypically and genotypically. The orientation of gene cassette structures of class 1 integrons was determined using referenced and designed overlapping primers and complete genome sequence (CGS) data. The antimicrobial resistance profile, porin protein mutations and the presence of active efflux activity were studied from the CGS. P. aeruginosa DMC-27b was resistant to a total of 20 antibiotics, with imipenem and meropenem MIC90s of >512 mg/L. The isolate harboured all four classes of β-lactamase: VEB-1 (class A), VIM-5 (class B), PDC-35 (class C) and OXA-2 and OXA-50 (both class D). Chromosomal harbouring of blaVIM-5 was associated with the intI1 gene cassette as the sole gene, a unique cassette so far reported. A total of 11 mutations, among them some mutations causing extra folds and changes in binding sites, in porin protein OprD might also affect its functionality regarding the transportation of antibiotics. This is one of the earliest reports of its kind on the co-existence of all four β-lactamase classes in P. aeruginosa DMC-27b. Acquisition of multiple resistance determinants is paving the way for the development of MDR. This superbug is a model for rapid dissemination of resistance traits both horizontally and vertically.

Discovery and characterization of the evolution, variation and functions of diversity-generating retroelements using thousands of genomes and metagenomes

BackgroundDiversity-generating retroelements (DGRs) are a unique family of retroelements that generate sequence diversity of DNA to benefit their hosts by introducing variations and accelerating the evolution of target proteins. They exist widely in bacteria, archaea, phage and plasmid. However, our understanding about DGRs in natural environments was still very limited.ResultsWe developed an efficient computational algorithm to identify DGRs, and applied it to characterize DGRs in more than 80,000 sequenced bacterial genomes as well as more than 4,000 human metagenome datasets. In total, we identified 948 non-redundant DGRs, which expanded the number of known DGRs in bacterial genomes and human microbiomes by about 55%, and provided a much more comprehensive reference for the study of DGRs. Phylogenetic analysis was done for identified DGRs. The putative target genes of DGRs were searched, and the functions of these target genes were investigated with a comprehensive alignment against the nr database.ConclusionsDGR system is a powerful and universal mechanism to generate diversity. DGR evolution is closely associated with the living environment and their cassette structures. Furthermore, it may impact a wide range of functional processes in addition to receptor-binding. These results significantly improved our understanding about DGRs.

Antimicrobial Resistance Genes, Cassettes, and Plasmids Present in Salmonella enterica Associated With United States Food Animals.

The ability of antimicrobial resistance (AR) to transfer, on mobile genetic elements (MGEs) between bacteria, can cause the rapid establishment of multidrug resistance (MDR) in bacteria from animals, thus creating a foodborne risk to human health. To investigate MDR and its association with plasmids in Salmonella enterica, whole genome sequence (WGS) analysis was performed on 193 S. enterica isolated from sources associated with United States food animals between 1998 and 2011; 119 were resistant to at least one antibiotic tested. Isolates represented 86 serotypes and variants, as well as diverse phenotypic resistance profiles. A total of 923 AR genes and 212 plasmids were identified among the 193 strains. Every isolate contained at least one AR gene. At least one plasmid was detected in 157 isolates. Genes were identified for resistance to aminoglycosides (n = 472), β-lactams (n = 84), tetracyclines (n = 171), sulfonamides (n = 91), phenicols (n = 42), trimethoprim (n = 8), macrolides (n = 5), fosfomycin (n = 48), and rifampicin (n = 2). Plasmid replicon types detected in the isolates were A/C (n = 32), ColE (n = 76), F (n = 43), HI1 (n = 4), HI2 (n = 20), I1 (n = 62), N (n = 4), Q (n = 7), and X (n = 35). Phenotypic resistance correlated with the AR genes identified in 95.4% of cases. Most AR genes were located on plasmids, with many plasmids harboring multiple AR genes. Six antibiotic resistance cassette structures (ARCs) and one pseudo-cassette were identified. ARCs contained between one and five resistance genes (ARC1: sul2, strAB, tetAR; ARC2: aac3-iid; ARC3: aph, sph; ARC4: cmy-2; ARC5: floR; ARC6: tetB; pseudo-ARC: aadA, aac3-VIa, sul1). These ARCs were present in multiple isolates and on plasmids of multiple replicon types. To determine the current distribution and frequency of these ARCs, the public NCBI database was analyzed, including WGS data on isolates collected by the USDA Food Safety and Inspection Service (FSIS) from 2014 to 2018. ARC1, ARC4, and ARC5 were significantly associated with cattle isolates, while ARC6 was significantly associated with chicken isolates. This study revealed that a diverse group of plasmids, carrying AR genes, are responsible for the phenotypic resistance seen in Salmonella isolated from United States food animals. It was also determined that many plasmids carry similar ARCs.

Numerical study of the static and dynamic characteristics of reinforced concrete cassette structures for high‐rise buildings

SummaryHigh‐rise buildings are extensively built in China, and the structure of these buildings is composed of different types of conventional system of which framed structures are more commonly employed. A new cassette structure with advantageous performance properties is proposed. Static and dynamic numerical simulations were applied to investigate the characteristics of this new structure. First, the components and other details are presented. A comparative analysis was conducted between the cassette structure and traditional structures using eight finite models with fiber elements in three different heights. A static pushover analysis and an incremental dynamic analysis were conducted based on 18 near‐ground motion records recommended by the Federal Emergency Management Agency. The seismic characteristics, deformation curve, interstory drift, roof displacement, and fragility curve are investigated. Based on the analysis of the models with three different heights and the variety of seismic records, the economic advantage and application of cassette structures for building industrialization are also discussed.

Progress in the Development of CFC/CuCrZr Components for HL-2M Divertor

The HL-2M divertor consists of a flat-type carbon fiber composite (CFC)/CuCrZr component and a cassette structure. The CFC/CuCrZr component is made of a water-cooled CuCrZr heat sink armored with carbon CFC tiles. The CFC surface was modified by using Cr slurry to improve its wettability to copper. The Cr layer was deposited by a simple screen-printing technique and then sintered at 1300 °C in a vacuum furnace. An oxygen-free copper (OFC) buffer layer was cast on the modified CFC surface in order to mitigate the internal stresses caused by mismatch in the coefficient of thermal expansion of CFC and CuCrZr. The brazing of the cast OFC/CFC tiles to the CuCrZr heat sink was performed by using a silver-free brazing alloy. Microstructural observations and shear strength tests demonstrate high quality of joining for the CFC/CuCrZr joints. The brazed CFC/CuCrZr mock-up experienced cyclic loading tests of 7 MW/m2 for 1000 cycles with no degradation of heat removal, which meets the requirement of HL-2M divertor.

Systems engineering approach for pre-conceptual design of DEMO divertor cassette

This paper presents the pre-conceptual design activities conducted for the European DEMO divertor, focusing on cassette design and Plasma Facing Components (PFC) integration. Following the systems engineering principles, a systematic design method, the Iterative and Participative Axiomatic Design Process (IPADeP), has been adopted. Basing on Axiomatic Design, IPADeP supports the early conceptual design of complex systems. The work moved from the geometrical and interface constraints imposed by the 2015 DEMO configuration model. Then, since different materials will be used for cassette and PFCs, the divertor geometry has been developed taking into account the cooling parameters of the cassette Eurofer steel and the integration of PFCs cooling system. Accordingly, the design process led to a double wall cassette structure with internal reinforcing ribs to withstand cassette coolant pressure and three different kinds of piping schemes for PFCs with dual circuits. These three solutions differs in the feeding pipes layouts and target manifold protection and they have been proposed and evaluated considering heat flux issues, shielding problems, interface requirements with blanket and vacuum vessel and remote maintenance needs. A cassette parametric shell model has been used to perform first structural analyses of the cassette body against coolant pressure. Taking advantages of the parametric surface modelling and its linkage with Finite Element (FE) code, the cassette ribs layout and thickness has been evaluated and optimized, considering at the same time the structural strength needed to withstand the coolant parameters and the maximum stiffness required for cassette preloading and locking needs.

Thermal analysis on the EAST tungsten plasma facing components with shaping structure counteracting the misalignment issues**Supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB107004 and 2013GB105003) and National Natural Science Foundation of China (No. 11405209).

Tungsten monoblock type tiles with ITER dimensions along with supporting cassette components were installed at EAST’s upper diverter during 2014 and EAST’s lower diverter will also be upgraded in the future. These cassette structures pose critical issues on the high cumulative incident heat flux due to the leading edges and misalignments (0 ∼ 1.5 mm), which may result in the destruction or even melting of the tungsten tile. The present work summarizes the thermal analysis using ANSYS multiphysics software 15.0 performed on the actively cooled W tiles to evaluate the shaping effect on surface temperature. In the current heat flux conditions (Q|| ∼ 100 MW m−2), the adopted chamfer shaping (1 × 1 mm) can only reduce the maximum temperature by about 14%, but it also has a melting risk at the maximum misalignment of 1.5 mm. The candidate shaping solutions elliptical (round) edge, dome and fish-scale are analyzed for comparison and are identified not as good as the dual chamfer structure. A relatively good dual chamfer (2 × 13 mm) shaping forming a symmetrical sloping roof structure can effectively counteract the 1.5 mm misalignment, reducing the maximum temperature by up to 50%. However, in the future heat flux conditions (Q|| ∼ 287 MW m−2), it may only endure about 0.5 mm misalignment. Moreover, no proper shaping solution has been found that can avoid melting at the maximum misalignment of 1.5 mm. Thus, the engineering misalignment has to be limited to an acceptable level.

CRISPR/Cas9-Mediated Insertion of loxP Sites in the Mouse Dock7 Gene Provides an Effective Alternative to Use of Targeted Embryonic Stem Cells.

Targeted gene mutation in the mouse is a primary strategy to understand gene function and relation to phenotype. The Knockout Mouse Project (KOMP) had an initial goal to develop a public resource of mouse embryonic stem (ES) cell clones that carry null mutations in all genes. Indeed, many useful novel mouse models have been generated from publically accessible targeted mouse ES cell lines. However, there are limitations, including incorrect targeting or cassette structure, and difficulties with germline transmission of the allele from chimeric mice. In our experience, using a small sample of targeted ES cell clones, we were successful ∼50% of the time in generating germline transmission of a correctly targeted allele. With the advent of CRISPR/Cas9 as a mouse genome modification tool, we assessed the efficiency of creating a conditional targeted allele in one gene, dedicator of cytokinesis 7 (Dock7), for which we were unsuccessful in generating a null allele using a KOMP targeted ES cell clone. The strategy was to insert loxP sites to flank either exons 3 and 4, or exons 3 through 7. By coinjecting Cas9 mRNA, validated sgRNAs, and oligonucleotide donors into fertilized eggs from C57BL/6J mice, we obtained a variety of alleles, including mice homozygous for the null alleles mediated by nonhomologous end joining, alleles with one of the two desired loxP sites, and correctly targeted alleles with both loxP sites. We also found frequent mutations in the inserted loxP sequence, which is partly attributable to the heterogeneity in the original oligonucleotide preparation.