Μm Wall Thickness Research Articles

Clinical Performance of Computer-Aided Design (CAD)/Computer-Aided Manufacturing (CAM) Resin Nanoceramic Endocrowns in Restoring Molars: An In Vivo Study.

Background It is difficult to determine the optimal method for restoring endodontically treated teeth, as several factors affect this decision. Functional requirements and the amount of remaining coronal tissue are considered the most important factors in choosing the best restoration for those teeth. Endocrown was introduced as a conservative alternative for endodontically treated and coronally damaged teeth. Aim The aim of this study is to assess the clinical performance of the nanoceramic system for molar endocrowns by evaluating color change, gingival condition, prosthesis integrity, and the presence of secondary caries. Materials and methods The sample consisted of 20 endocrowns. The teeth were prepared with at least 2 mm of wall thickness and a cavity depth of 4 mm from the occlusal surface. The final impression was taken, and the prostheses were adhered using dual-cure resin cement. It was clinically evaluated according to clinical success criteria (United States Public Health Service) in terms of color stability, gingival indexes, integrity of the restoration, and the presence of secondary caries after a week, three months, six months, and a year. The statistical study was conducted using IBM SPSS Statistics for Windows, Version 23.0 (Released 2015; IBM Corp., Armonk, NY, USA), and the results were considered statistically significant at the 95% level of significance. The Friedman test was used to study the significance of the differences in the average values of color change, plaque index, and the integrity of the prostheses during follow-up periods. Results The study showed a gradual increase in the degree of color change with follow-up periods. Furthermore, there was no significant difference in the incidence of gingival changes, the integrity of the prosthetic margins, or the occurrence of secondary caries during the follow-up periods. Conclusions Within the limitations of this study, an endocrown made of CeraSmart nanoceramic is an acceptable option for crowning decayed and endodontic-treated molars with acceptable clinical performance.

Insights into reaction–diffusion behaviors of acetylene selective hydrogenation on pellet catalysts

AbstractIn this work, a particle‐resolved computational fluid dynamics model of the acetylene hydrogenation process is developed to investigate the effects of catalyst particle structures on the reaction–diffusion behaviors aiming to improve selectivity toward target ethylene. The effects of packing structures on mass and heat transfer are explored by employing particles with varying shapes, wall thicknesses, and external diameters. The simulation results reveal that decreasing diffusion paths and elevating reactor bed temperature will enhance ethylene selectivity, and cylinder and Raschig ring packing structures exhibit the lowest and highest ethylene selectivity of 35.6% and 48.9% at 70% of acetylene conversion, respectively. Reducing wall thicknesses of Raschig ring particles facilitates the diffusion of generated ethylene from the interior zone of catalysts but concurrently inhibits the conversion of acetylene to ethylene. The Raschig ring catalyst particle with 1.9 mm of wall thickness and 3.5 mm of external diameter is finally revealed to exhibit the highest ethylene selectivity.

26. BIOPRINTING VASCULAR GRAFTS WITHOUT SUPPORT MATERIAL: A COMPARISON BETWEEN NEW AND COMMERCIAL HYDROGEL

Abstract Introduction Currently, the demand for personalized vascular grafts is increasing and bioprinting techniques emerge as a promising approach for its development. The aim is to comparatively evaluate the performance of a Gelatin/Gellan Gum/Alginate hydrogel and a commercial bioink to produce bioprinted vascular grafts without support material. Methods Two hydrogels were employed in this study: a custom-made Gelatin/Gellan Gum/Alginate (8:3:0.5 %w/v) and a commercial bioink (Cellink Bioink) consisting of 5% alginate with nanocellulose. Three experiments were conducted to assess their performance. The first experiment involved diluting the commercial hydrogel in PBS at a 1:10 ratio. The second experiment applied the commercial hydrogel without dilution, while the third experiment utilized the custom-made hydrogel without dilution. Optimal printing conditions were established for both hydrogels, with the Cellink bioink set to 37 °C, 10 kPa, and 7 mm/s, and the Gelatin/Gellan Gum/Alginate hydrogel set to 50 °C, 45 kPa, and 9 mm/s. For each hydrogel, three grafts were printed, each with dimensions of 15 mm height, 500 μm wall-thickness, and a 6 mm inner diameter. The physical characteristics of these grafts were subsequently measured using an optical microscope. Results Results showed differences between the three experiments. Vascular grafts produced with Gelatin/Gellan Gum/Alginate hydrogel present a wall-thickness and an inner diameter of 553±150 μm and 5.33±0.24 mm, respectively. In contrast, the commercial bioink from Cellink failed to facilitate the production of vascular grafts, as it fully collapsed at layer 17 out of 37. Conclusion The Gelatin/Gellan Gum/Alginate hydrogel proves to be effective in bioprinting vascular grafts, demonstrating both adequate accuracy and structural stability. Notably, it distinguishes itself from commercial bioinks by not necessitating additional sacrificial materials in the process.

Additive manufacturing of patient-specific high-fidelity and thickness-controlled cerebral aneurysm geometries

Additive Manufacturing (AM) offers unique advantages in rapidly fabricating highly complex and highly customized geometries; which suits very well for patient-specific medical applications. AM has been explored for a wide range of medical needs such as prosthetics, implants, surgical guides, and medical education. In particular, there is a growing need to leverage AM processing for achieving high-fidelity 3D biomimicry models to better understand critical physiological responses for clinical needs. In this study, a new design-manufacturing-evaluation workflow is presented and validated to manufacture complex optically clear and compliant 3D geometries that account for physiologically relevant conditions (i.e., 400 µm wall thickness at 100 mmHg) through an integrated AM (Vat Photopolymerization) and silicone molding technique. This study aims to establish the workflow by developing high-fidelity 3D intracranial aneurysm (IA) geometries using patient-specific data. The digital light processing (DLP) method was employed to create thin-walled shells for silicone molding. The samples created were successful in reproducing compliant, optically-clear aneurysms that can be used in in vitro studies. Findings from this study can be used to better understand the long-term growth effects of aneurysms, the causes for their sudden ruptures, and help develop potential prevention methods and treatments.

#5485 CHRONIC KIDNEY DISEASE NOR STROMAL CELL-DERIVED FACTOR 1Α PEPTIDE (SDF-1A) BIO-FUNCTIONALIZATION ALTER RODENT VASCULAR IN SITU TISSUE FORMATION

Abstract Background and Aims The systemic pro-inflammatory environment of chronic kidney disease (CKD) could influence neo-tissue formation of in situ tissue engineered vascular access grafts. Here, we studied in-graft tissue formation and inflammation in a rat CKD model. Moreover, we explored graft bio-functionalization with stromal cell-derived factor 1α peptides (SDF-1α), a progenitor cell chemotactic which may improve cell engraftment. Method Pristine or SDF-1α bio-functionalized vascular grafts (1,2 mm ID, 2 cm length, 250–300 μm wall thickness) were created from biodegradable, polycarbonate-bisurea (PC-BU) electrospun meshes. Abdominal aorta interposition grafts were implanted in female Sprague Dawley rats (n = 53) that underwent sham surgery or CKD induction by 5/6th nephrectomy. Explanations and analyses were performed after two (n = 25) or twelve (n = 9) weeks. Results At two weeks, survival and graft patency were 100%. Explant cellularity and collagen content were not significantly different between sham and CKD rats and were not influenced by SDF-1α. Endothelial cell coverage (RECA+) and smooth muscle cell presence (αSMA+) were visually similar irrespective of disease or bio-functionalization. Elastin+ (p = 0,11), pan-(CD68+, p = 0,08) and anti-inflammatory macrophage (CD163+, p = 0,52) surface area, as well as (anti-)inflammatory gene expression were not significantly different between groups. The twelve-week CKD-group was taken out of experiment prematurely due to rapid disease progression. In addition, preliminary death due to vascular rupture occurred in four animals (n = 2 pristine and n = 2 SDF-1α) in the twelve-week sham animals. While patent, all remaining sham explants at twelve weeks (n = 9) showed severe vascular dilatation and calcifications (Von Kossa+). No differences in inflammatory and neo-tissue markers were found between twelve-week sham pristine and SDF-1α grafts or between explants over time. Conclusion CKD did not significantly alter inflammation or tissue formation of in situ tissue engineered vascular grafts. Additionally, SDF-1α bio-functionalization did not significantly alter cell engraftment or tissue formation. Mechanical stability of the graft appears to be the primary driver of neo-tissue formation. Future emphasis on in vitro to in vivo translation should be on the fine balance between tissue formation on one hand and fiber resorption on the other hand.

The Numerical Study of The Need for Transverse Reinforcement of a Spun Pile

A numerical study based on FEA was conducted to seek the optimal need for transverse reinforcement of a spun pile with 400mm-diameter and 75mm of wall thickness. Two equations from ACI 318-19 and ASCE 7-16 were compared. The parametric study was limited to a spun pile with 450mm diameter and 75mm of wall thickness. The amount of transverse reinforcement was presented as the ratio to the ACI requirement. The ratio was varied and its effect on strength and ductility was observed. Three different axial load ratios, 0.1, 0.2 and 0.3 Fc’Ag, that are usually applied on the foundation were considered. The needs for spun pile with and without concrete infill are different since it is a function of the ratio of gross area (Ag) to the confined area (Ach) of concrete. An empty spun pile require a higher amount than the filled pile. The axial load ratio is another factors that affect the need for that reinforcement. However, ACI does not recognize it. The study found that the amount of transverse reinforcement required by ACI and ASCE can be reduced to get an economical amount without significantly reducing the strength and the ductility of the spun pile.

First Report of Phytophthora occultans Causing Dieback of Buxus sempervirens in the Czech Republic.

In Nov 2011, and then recurrently since Sep 2020, an extensive decline has been recorded in boxwood (Buxus sempervirens), sometimes with several dozens of damaged individuals planted in private gardens and public areas and purchased in amateur markets in the Czech Republic. The leaves of the plants first showed orange-bronze discoloration, then dried and fell off, and the affected plants died. The roots, collars and stems of these plants had dark brown to black necrotic lesions. Phytophthora occultans Man in 't Veld & K. Rosend. was consistently isolated on selective medium PARPNH (Jung et al. 1996) directly from segments of symptomatic collar tissues and from rhododendron leaf pieces used to bait excised roots. On 20% V8 agar (V8A) and on carrot agar (CA), colonies had a stellate pattern. Radial growth at 25°C was 9.4 mm/day on V8A and 5.3 mm/day on CA. The cardinal growth temperatures were min. 7°C, optimum 25 to 27°C, and max. 32°C. The isolates were homothallic and produced on CA colorless globose oogonia ranging from 25.4 to 36.4 µm (n = 40) in diam. Oospores were slightly aplerotic and measured (n = 40) 22.5 to 31.9 µm in diam., with a 0.9 to 1.5 µm thick wall. The antheridia were predominantly paragynous and averaged 11.5 × 9.9 µm (height × width, n = 40). Noncaducous sporangia were obpyriform, ovoid, elongated to irregular and semipapillate, sometimes bipapillate and measured (n = 40) 31.4 to 73.4 × 17.8 to 32.1 µm, and the L:B ratio was 1.9 to 2.0. Chlamydospores and hyphal swellings were not observed. The morphological characteristics resembled those described for P. occultans (Man in't Veld et al. 2015). The isolates were deposited in the Czech Collection of Phytopathogenic Oomycetes (CCPO) under accession nos. 551.11, 1158.20, 1176.21, 1201.21, 1218.21, 1236.21 and 1261.22. For molecular identification, the internal transcribed spacer (ITS) region, cytochrome oxidase subunit 1 gene (COX1), and translation elongation factor-1α (EF) gene from all isolates were amplified and sequenced using the primer pairs ITS4/ITS5 (White et al. 1990), COXF-CIT/COXR-CIT (Man in't Veld et al. 2015), and ELONGF1/ELONGR1 (Kroon et al. 2004), respectively. The resulting sequences of representative isolates P1158.20 and P1176.21 were deposited in GenBank (accession nos. MW750576 and OP326036 for ITS, ON862131 and OP313505 for COX1 and MW762616 and ON862132 for EF). BLASTn searches of GenBank, using the partial ITS, COX1, and EF sequences, revealed 100, 100, and 99% sequence identity, respectively, to P. occultans ex-holotype culture CBS101557 accessions JX978155, JX978156 and KF650770 (Man in't Veld et al. 2015). Concatenated sequences of the three genes were used to conduct a phylogenetic analysis using the maximum likelihood method in MEGA 11 (Tamura et al. 2021). The isolates were identified as P. occultans based on morphology and a multigene phylogenetic analysis. Koch´s postulates were confirmed by a soil infestation test. Healthy 2-year-old B. sempervirens plants were inoculated (9 plants per isolate and control, isolates no. 1158.20, 1176.21, 1261.22) with three 5-mm-diam. V8A mycelial plugs by inserting into the substrate near the collar. Control plants were treated with sterile agar plugs. All plants were kept in a greenhouse at 25°C and exposed to 24 h of flooding up to collar once a week. All inoculated plants showed wilting, collar lesions and root rot occurred after 21 days, while control plants remained healthy. The pathogen was reisolated from infected plants and confirmed by molecular identification. P. occultans was found for the first time in 1998 on Buxus sempervirens in the Netherlands and later in Belgium, the United Kingdom, Germany and Romania (Man in´t Veld et al. 2015, Nechwatal et al. 2014), as well as in the USA (Reeser et al. 2015, Gitto et al. 2018). This is the first report of P. occultans in the Czech Republic. This pathogen likely poses another significant threat to boxwood cultivation in addition to the previously invaded Cydalima perspectalis and Calonectria pseudonaviculata.

Cold Microdrawing of Pure Magnesium Capillary Structures for Biomedical Applications

Abstract This paper presents a study on cold microdrawing of pure magnesium for biomedical applications, where hollow sinking drawing of microtubes of 820 μm diameter and wall thickness around 100 μm was used, varying drawing speeds to achieve a significant reduction in cross-sectional area in a single pass. Results showed an improved surface finish with reduced surface roughness after drawing. The material exhibited an increase in microhardness and ultimate tensile strength by 41% due to work hardening caused by plastic deformation. The study also identified wall thickening of the tube and observed springback behavior of Mg at the die exit. Drawing forces were collected for process monitoring, and finite element (FE) simulations were conducted to assess the risk of pure Mg microtube breakage. This research contributes to advancing the state of the art in Mg microtube drawing, addressing the unique challenge of working with such small tube dimensions where limited studies currently exist.

Imaging acute cholecystitis, one test is enough

BackgroundPatients with right upper quadrant pain are often imaged using multiple modalities with no established gold standard. A single imaging study should provide adequate information for diagnosis. MethodsA multicenter study of patients with acute cholecystitis was queried for patients who underwent multiple imaging studies on admission. Parameters were compared across studies including wall thickness (WT), common bile duct diameter (CBDD), pericholecystic fluid and signs of inflammation. Cutoff for abnormal values were 3 mm for WT and 6 mm for CBDD. Parameters were compared using chi-square tests and Intra-class correlation coefficients (ICC). ResultsOf 861 patients with acute cholecystitis, 759 had ultrasounds, 353 had CT and 74 had MRIs. There was excellent agreement for wall thickness (ICC = 0.733) and bile duct diameter (ICC = 0.848) between imaging studies. Differences between wall thickness and bile duct diameters were small with nearly all <1 mm. Large differences (>2 mm) were rare (<5%) for WT and CBDD. ConclusionsImaging studies in acute cholecystitis generate equivalent results for typically measured parameters.

An ultra‐stable sodium half/full battery based on a unique micro‐channel pine‐derived carbon/SnS2@reduced graphene oxide film

AbstractDeveloping super stability, high coulomb efficiency, and long‐span life of sodium‐ion batteries (SIBs) can significantly widen their practical industrial applications. In this study, we report a pine‐derived carbon/SnS2@reduced graphene oxide (PDC/SnS2@rGO) film with fast ion/electron transport micro‐channel used as a SIB anode, which shows ultrahigh stable stability and long‐span life. Functionally, a biomass PDC/SnS2@rGO film with ~30 μm micro carbon channel and ~1.2 μm thick carbon wall can simultaneously provide the fast electron transport path and the Na+ transport channel. Also, the two‐dimensional (2D) layered SnS2 particles attached to the carbon wall of PDC can increase more Na+ contact sites and shorten the Na+ transport path in the NaPF6 electrolyte. To avoid the separation of SnS2 from PDC during the sodiation process, rGO with excellent conductivity and flexibility is wrapped in the SnS2 outer layer as an “electronic garment”. A ~650 mA h g−1 high Na+ storage capacity at 0.1 A g−1 and ~99.8% ultrahigh coulomb efficiency after 800 cycles at 5 A g−1 are obtained when PDC/SnS2@rGO film is used as a SIB anode. Furthermore, a SIB full‐cell is assembled using PDC/SnS2@rGO film (anode) and Na3V2(PO4)3 (cathode), which exhibits a ~163.9 mA h g−1 high reversible capacity and ~99.7% coulomb efficiency performance. Our work provides a reasonable design strategy for the application of biomass‐derived carbon in SIBs, which may inspire more biomass‐derived material studies.

First Report of Puccinia menthae Causing Leaf Rust on Spearmint (Mentha spicata) in Mexico.

Spearmint (Lamiaceae) is an aromatic herb widely cultivated in Mexico for its culinary, medicinal, and industrial properties. In May 2020, symptoms and signs of rust were observed in a two-ha commercial crop of spearmint in Cuautla, Morelos (18°50'26.6"N 98°57'31.9"W), Mexico. The disease incidence was 85% and the severity was 23%. Initial symptoms included chlorotic spots on the adaxial surface of the leaves. At advanced stages of the disease, necrotic spots surrounded by chlorotic halos were developed, and later the plants were defoliated. The signs were observed as numerous orange to reddish-brown erumpent pustules primarily on the abaxial surface of the leaves. Microscopic examination of the samples revealed the presence of subepidermal uredinia, erumpent, with hyaline and cylindrical paraphyses. Urediniospores (n = 50) were hyaline to light yellow, globose to obovoid, measuring 17-27  11-25 μm, including 0.6-0.7 μm wall thickness, individually supported on pedicels, echinulate, with two germinative pores. Morphological features of the fungus correspond with previous descriptions of Puccinia mentha by Kabaktepe et al. (2017). A voucher specimen (accession no. UACH448) was deposited in the Department of Agricultural Parasitology Herbarium at the Chapingo Autonomous University. To confirm identification, the 28S gene region of rDNA was amplified from one sample by a nested PCR using the primer sets Rust2inv (Aime, 2006) and LR6 (Vilgalys and Hester, 1990), and Rust28SF primers (Aime et al., 2018), and LR5 (Vilgalys and Hester, 1990) for the first and second reactions, respectively. The sequence of our specimen (GenBank accession No. OL878354) showed 100% homology (923/1304bp) with the type-specimen sequence of P. menthae (GenBank accession No. DQ354513) from Cunila origanoides from USA (Aime, 2006). Also, a phylogenetic analysis (Bayesian inference) including a published 28S dataset for Puccinia species was performed and the isolate UACH448 was grouped into a clade with P. menthae. Pathogenicity was demonstrated by spraying five ml of a suspension of urediniospores (1104 spores/ml) recovered from infected leaves onto leaves of ten healthy spearmint plants and ten noninoculated plants served as controls. All plants were maintained at temperatures from 28 to 35°C and relative humidity ranging from 70 to 80%. All inoculated plants developed the characteristic symptoms of the disease after 14 days, whereas the control plants remained symptomless. The pathogenicity test was performed twice with similar disease response. The morphological characteristics of the pathogen recovered from all the inoculated plants were identical to that originally inoculated, thus fulfilling Koch's postulates. To our knowledge, this is the first report of Puccinia menthae causing leaf rust on Mentha spicata in Mexico. This species has been previously identified in Australia (Edwards et al. 1999), New Zealand (Beresford et al. 1982), and USA (Farr and Rossman, 2021) on Mentha spicata. This disease reduces considerably the quality of peppermint plants, so it is necessary to develop management strategies.

Preparation of core-shell microcapsules based on microfluidic technology for the encapsulation, protection and controlled delivery of phycocyanin

Phycocyanin (PC) is a naturally active protein with extensive potential physiological functions. However, the poor stability and low bioavailability of PC have limited its development in nutraceuticals. Therefore, we developed an efficient microfluidic device to fabricate core-shell microcapsules for PC entrapment and colonic delivery. Microfluidics utilizes microchannels and fluid flow rates to shear mutually incompatible fluids to form dispersed emulsion droplets, providing an opportunity to investigate the structure and size of emulsions and precisely control the production of emulsion droplets. By introducing intermolecular interactions, PC was effectively immobilized in the cavity of the inner core sodium alginate (SA) gel, ensuring a high encapsulation efficiency of up to 98% for SA-E microcapsules. The release effects of microcapsules with different wall thicknesses were evaluated by simulating gastrointestinal juice digestion experiments. The results revealed that the microcapsules with 20–30 μm wall thickness were more stable and had superior release performance in gastrointestinal fluid compared with the microcapsules with 10 and 50 μm wall thickness. In addition, after the simulated digestion process in artificial gastrointestinal fluid, the PC embedded in SA-E microcapsules still remained the same structure and exhibited good antioxidant and immunomodulatory activities. The enhanced stability and bioavailability of PC suggested that SA-E microcapsules can be used for PC entrapment and colonic delivery.

Abstract WMP69: Features Of Calcified Carotid Atherosclerosis Are Associated With Stroke In Patients With Embolic Stroke Of Undetermined Source

Introduction: We examined qualitative features of calcified plaque in patients with embolic stroke of undetermined source (ESUS). Methods: A retrospective cohort of anterior circulation acute ischemic stroke patients with CTA neck and meeting criteria for ESUS was identified. A segmentation software measured carotid bifurcation calcified plaque volumes. A neuroradiologist manually measured maximum carotid wall and calcified wall thickness (WT), maximum craniocaudal calcified plaque length, degree of circumferential involvement (none, punctate, 90°, 180°, 270°, 360°) and assessed for intimal, transmural, and adventitial calcifications. Descriptive statistics included medians and interquartile ranges. Differences between ipsilateral (carotid ipsi ) and contralateral (carotid contra ) carotid arteries to stroke side were tested using Wilcoxon Signed-Rank, McNemar, and marginal homogeneity tests. Results: Ninety-four subjects met criteria for ESUS. Mean age was 65 years and 55% were women. Carotid ipsi had a significantly higher volume of calcified plaque [Vol ipsi =39.1 (12.4, 86.7) vs Vol contra =25.9 (4.9, 71.7), p=0.05] and maximum calcified WT [CalcWT ipsi= 1.4 (0, 2.6) vs CalcWT contra =0 (0, 2.1), p=0.03] than carotid contra . There were no significant differences in the maximum craniocaudal calcified plaque length (p=0.09) or degree of circumferential calcified plaque involvement (p=0.35) between carotid ipsi and carotid contra . Intimal (p=0.03) but not transmural (p=0.14) or adventitial (p=0.12) calcifications were significantly more frequent in carotid ipsi than carotid contra . A subgroup analysis (n=48) including either carotid artery measuring ≥3mm in maximum WT showed intimal calcifications remained significantly associated with stroke side (p=0.02; Figure). Conclusion: Higher calcified plaque volumes, calcified wall thickness and intimal calcifications may be associated with ischemic stroke in patients with ESUS.

Insights from microstructure and mechanical property comparisons of three pilgered ferritic ODS tubes

To develop advanced nuclear fuel claddings, two oxide dispersion strengthened (ODS) alloys were designed, manufactured, and evaluated. First, 12 %Cr alloy, is an ODS-version of ferritic steel, and second, 10 %Cr-6 %Al alloy, is a high-strength version of accident tolerant iron-chrome-aluminum alloy. Their properties and performance were compared with “classical” ODS material, 14 %Cr alloy 14WYT. Thin-walled (∼500 µm wall thickness) tubes were manufactured successfully using the pilgering technique. For all alloys, axial tensile specimens exhibited high tensile strength (>1 GPa) and reasonable plastic strains (10–17%). Ring tensile specimens, conversely, showed limited ductility (∼1%) with similar strengths to those measured in the axial orientation. The grain size, precipitate dispersion characteristics, and dislocation densities were then used to estimate yield strengths that were compared against room temperature axial and ring-pull tensile test data. The strengthening models showed mixed agreement with experimentally measured values due to the highly anisotropic microstructures of all three ODS tubes. These results illustrate the need for future model optimization to accommodate non-isotropic microstructures associated with components processed using rolling/pilgering approaches. In all cases, atom probe tomography and energy-filtered transmission electron microscopy demonstrated that ODS structure survived multiple pilgering operations, and precipitate microstructure evolution matched well the state-of-the-art nanoprecipitate coarsening models.

High-precision laser powder bed fusion processing of pure copper

Pure copper is widely used in the industry as the base metal for heat transfer and electromagnetic applications, thanks to its superior electrical and thermal conductivity. Complex pure copper components have been attempted by various additive manufacture (AM) techniques. Among them, laser powder bed fusion (LPBF) is competent to print smooth curved surfaces and complex geometries due to its high resolution and powder bed support. However, the fabrication of pure copper by LPBF generally requires a laser power of more than 400 W (usually up to 1000 W) due to the high infrared laser reflection and thermal conductivity of pure copper. Therefore, the laser optics could be damaged by the back reflection of high-power laser. The LPBF with a short-wavelength laser has also been attempted but with a low resolution of 500 µm at present. In this work, a high-precision LPBF (hp-LPBF) system with small laser spot (25 µm), fine powder (5–25 µm), and small layer thickness (10 µm) is developed, which can achieve the full densification of pure copper components with high resolution and low roughness at a relatively low laser power. The thin walls and cube bulks were employed to investigate the effect of parameters on the resolution, roughness, and performance. As a result, the as-built pure copper components with the relative density (RD) (99.6%) and the electrical conductivity of 76.1% International Annealed Copper Standard (IACS) are fabricated by the optimal parameters of the laser power of 200 W, the scan speed of 600 mm/s, the hatch distance (HD) of 0.05 mm. After heat treatment, the electrical performance can be further increased to 96% IACS. The pure copper parts with complex cellular structures were printed with 100 µm wall thickness and the top/side/bottom surface roughness Ra of 3.3/14.8/19.2 µm. Overall, the hp-LPBF has demonstrated its capability to print finer and smoother pure copper parts with the same level of relative density and properties compared to conventional LPBF.

Perichondrium-inspired permeable nanofibrous tube well promoting differentiation of hiPSC-derived pellet toward hyaline-like cartilage pellet

The pellet formation has been regarded as a golden standard for in vitro chondrogenic differentiation. However, a spatially inhomogeneous chondrogenic microenvironment around a pellet resulted from the use of a traditional impermeable narrow tube, such as the conical tube, undermines the differentiation performance and therapeutic potential of differentiated cartilage pellet in defective articular cartilage treatment. To address this drawback, a perichondrium-inspired permeable nanofibrous tube (PINaT) well with a nanofibrous wall permeable to gas and soluble molecules is proposed. The PINaT well was fabricated with a micro deep drawing process where a flat thin nanofibrous membrane was transformed to a 3.5 mm deep tube well with a ∼50 µm thick nanofibrous wall. Similar to in vivo perichondrium, the PINaT well was found to allow oxygen and growth factor diffusion required for chondrogenic differentiation across the entire nanofibrous wall. Analyses of gene expressions (COL2A1, COL10A1, ACAN, and SOX9), proteins (type II and X collagen), and glycosaminoglycans contents were conducted to assess the differentiation performance and clinical efficacy of differentiated cartilage pellet. The regulated spatially homogeneous chondrogenic microenvironment around the human induced pluripotent stem cell-derived pellet (3 × 105 cells per pellet) in the PINaT well remarkably improved the quality of the differentiated pellet toward a more hyaline-like cartilage pellet. Furthermore, an accelerated chondrogenic differentiation process of the pellet produced by the PINaT well was achieved for 14 days, demonstrating a hyaline cartilage-specific marker similar to the control pellet differentiated for 20 days. Finally, the enhanced clinical efficacy of the hyaline-like cartilage pellet was confirmed using an osteochondral defect rat model, with the repaired tissue resembling hyaline cartilage rather than fibrous cartilage after 8 weeks of regeneration.

Different Approaches for Manufacturing Ti-6Al-4V Alloy with Triply Periodic Minimal Surface Sheet-Based Structures by Electron Beam Melting.

Targeting biomedical applications, Triply Periodic Minimal Surface (TPMS) gyroid sheet-based structures were successfully manufactured for the first time by Electron Beam Melting in two different production Themes, i.e., inputting a zero (Wafer Theme) and a 200 µm (Melt Theme) wall thickness. Initial assumption was that in both cases, EBM manufacturing should yield the structures with similar mechanical properties as in a Wafer-mode, as wall thickness is determined by the minimal beam spot size of ca 200 µm. Their surface morphology, geometry, and mechanical properties were investigated by means of electron microscopy (SEM), X-ray Computed Tomography (XCT), and uniaxial tests (both compression and tension). Application of different manufacturing Themes resulted in specimens with different wall thicknesses while quasi-elastic gradients for different Themes was found to be of 1.5 GPa, similar to the elastic modulus of human cortical bone tissue. The specific energy absorption at 50% strain was also similar for the two types of structures. Finite element simulations were also conducted to qualitatively analyze the deformation process and the stress distribution under mechanical load. Simulations demonstrated that in the elastic regime wall, regions oriented parallel to the load are primarily affected by deformation. We could conclude that gyroids manufactured in Wafer and Melt Themes are equally effective in mimicking mechanical properties of the bones.

Evaluation of celiac disease with uniphasic and multiphasic dynamic MDCT imaging.

An analysis of dynamic contrast MRI has been shown to provide valuable information about disease activity in Crohn's disease and Celiac disease(CD). However, there are no reports of dynamic multi-detector computer tomography use in patients with CD. The aim of this study is to determine and compare the perfusion dynamics of the patients treated with control subjects and the perfusion dynamics in patients with untreated CD, using dynamic contrast in MDCT and compare studying contrast dynamics in Marsh types as well. In this retrospective study, uniphasic and multiphasic MDCT, untreated, treated, incompatible CD patients and healthy control group duodenum wall thickness and HU values were compared in terms of patient groups and modified Marsh types. In dynamic CT, the highest contrast curve was observed in the untreated group and Marsh type 1. While the contrast curve of the untreated and non-compliant patients increased rapidly and showed wash out, the type 4 contrast curve was observed, whereas the treated and control group slowly increased type 5 contrast curve. In the contrast-enhanced CT in the venous phase, in the ROC analysis between Marsh 1-2 and Marsh 3a-c, the sensitivity was 97% and the specificity was 87% when the cut off was taken as 4.45mm for wall thickness (p: 0.005). Contrast-enhanced single-phase and dynamic MDCT imaging in CD patients may be useful in evaluating the inflammatory and pathological process in the small intestine.

A fluid-supported 3D hydrogel bioprinting method

Hydrogels are used in many biomedical applications, including regenerative medicine and surgical training phantoms. However, the ability to shape these materials into complex anatomical structures using additive manufacturing is limited in part by their low mechanical stiffness. We developed a hydrogel 3D printer, that projects patterns directly onto a thin layer of fluid-supported hydrogel precursor, which serves as a floating, liquid projection screen. This approach avoids inadvertent adhesion that affects typical resin-based 3D printers, and enables fast, continuous printing. As a consequence, we can print smooth objects free of layering artifacts, at rates of 200 mm/h along the Z-axis. We demonstrate the versatility of our approach by printing various complex structures, including free-standing channel networks with 500 μm-thick walls, using hydrogels with a wide range of stiffness from 7 kPa to more than 4 MPa. Lastly, because the printer features a free surface, we combined it with an extruder to perform multi-material printing. We use this strategy to create centimeter-scale, cell-laden hydrogels containing channels, that help address the key nutrient supply problem in bioprinting.

Inverse 3D Printing with Variations of the Strand Width of the Resulting Scaffolds for Bone Replacement.

The objective of this study was to vary the wall thicknesses and pore sizes of inversely printed 3D molded bodies. Wall thicknesses were varied from 1500 to 2000 to 2500 µm. The pores had sizes of 500, 750 and 1000 µm. The sacrificial structures were fabricated from polylactide (PLA) using fused deposition modeling (FDM). To obtain the final bioceramic scaffolds, a water-based slurry was filled into the PLA molds. The PLA sacrificial molds were burned out at approximately 450 °C for 4 h. Subsequently, the samples were sintered at 1250 °C for at least 4 h. The scaffolds were mechanically characterized (native and after incubation in simulated body fluid (SBF) for 28 days). In addition, the biocompatibility was assessed by live/dead staining. The scaffolds with a strand spacing of 500 µm showed the highest compressive strength; there was no significant difference in compressive strength regardless of pore size. The specimens with 1000 µm pore size showed a significant dependence on strand width. Thus, the specimens (1000 µm pores) with 2500 µm wall thickness showed the highest compressive strength of 5.97 + 0.89 MPa. While the 1000(1500) showed a value of 2.90 + 0.67 MPa and the 1000(2000) of 3.49 + 1.16 MPa. As expected for beta-Tricalciumphosphate (β-TCP), very good biocompatibility was observed with increasing cell numbers over the experimental period.