BackgroundHepatic pseudoaneurysm (HPA) is a rare complication that can occur after liver trauma and carries a high risk of rupture. HPA is usually asymptomatic until rupture, so performing routine surveillance of liver trauma patients is important. Most posttraumatic HPA occurs within the first week after injury, so surveillance imaging ~ 7 days postinjury is suggested.Case presentationWe herein report a 47-year-old man who was diagnosed with asymptomatic HPA 25 days after a knife injury. The patient was transferred to the emergency room after attempting suicide by stabbing himself in his abdomen with a knife. The knife was surgically removed, and the postoperative course was uneventful. Computed tomography (CT) on postoperative day (POD) 12 showed no HPA. However, follow-up CT on POD 25 revealed HPA. The HPA was treated with coil embolization. The patient was discharged with no complications. One year after the injury, the patient had no recurrence or medical problems.ConclusionWhen managing patients with penetrating liver trauma, it is important to note that HPA may not be identifiable on CT early after injury but may still develop later.

Summary Sealing elements (SEs) of fracture plugs have crucial roles to isolate target zones of a well in hydraulic fracturing. If the zonal isolation by the SE is not adequate, it can result in erosion of the casing. To the best of the authors’ knowledge, the effect of casing deformation on sealing performance is not well researched or understood. To study the effect of casing deformation on sealing performance, finite element analysis (FEA) of SEs in oval casings was conducted in this study. Finite element simulation of a degradable fracture plug with three different casings ovalities (0%, 2%, and 5%) and three different SE designs (O-ring type, short type, and traditional long type) was conducted to evaluate deformation behavior and sealing performance of SEs in deformed casings. Contact pressure (CPRESS) on the casing by the SE after the plug was set in the casing and the risk of leakage were discussed and compared for each design. In the casing with 0% ovality, all the SE designs established contact with the inner surface of the casing when setting force was applied. However, for the O-ring-type design, the area in contact with the casing was small and it may result in leak and erosion in the actual well if there is a small dent or deformation on the casing. When there is ovality in the casing, the minor inside diameter (ID) has a smaller ID and the major ID has a larger ID compared to the nominal ID of the casing. In the casing with 2% and 5% ovality, neither O-ring-type SE (O-SE) nor short-type SE (S-SE) could contact the major ID of the casing and there was a gap between the inner surface of the casing and the SE. This gap can cause erosion of the fracture plug and casing when the fluid passes through the gap. In contrast, the traditional long-type SE (L-SE) contacted both major and minor IDs of the casing, and no gap was observed. This result indicates that there is a potential risk of insufficient isolation of target zones and erosion of casings in actual well conditions if fracture plugs with S-SEs are used. Because there are various types of fracture plugs with different SE designs, this study helps to select proper fracture plugs with good SE design and mitigate the risk of erosion of casings and plugs. As this study is based on FEA simulations, future demonstrations through experiments and field trials are needed.

Ghost fishing, caused by lost fishing lines and nets, has become a severe problem in marine environments. To eliminate ghost fishing in the ocean, the environmental degradation behavior of fishing lines must be understood. In this study, the environmental degradation of biodegradable nylon 4 fishing lines and commercial nylon 6, poly(ethylene terephthalate) (PET), and poly(vinylidene fluoride) (PVDF) fishing lines was simulated in the laboratory using an artificial weathering tester and biodegradation test in extracted seawater. To understand the degradation mechanism, the chemical and structural changes induced by photo-oxidation and biodegradation were investigated using tensile test, scanning electron microscopy, differential scanning calorimetry, gel permeation chromatography, infrared spectroscopy, and wide- and small-angle X-ray scattering. The results indicated that photo-oxidation occurred in the amorphous phase of the nylon 4, nylon 6, and PET fishing lines during ultraviolet (UV) exposure. The nylon 4 fishing lines exhibited excellent biodegradability, whereas the nylon 6, PET, and PVDF fishing lines could not be degraded by microorganisms in the extracted seawater. Both processes, i.e., photo-oxidation and biodegradation, were confined to the amorphous regions of nylon 4. Note that the PVDF fishing lines could not be degraded by UV exposure and biodegradation and, hence, should be recycled after use.

Polyglycolic acid (PGA) sheets are difficult to adapt to the central airway because of poor durability against high air pressure. Therefore, we developed a novel layered PGA material to cover the central airway and examined its morphologic traits and functional performance as a potential tracheal replacement. A critical-size defect in rat cervical tracheas was covered with the material. Morphologic changes were bronchoscopically and pathologically evaluated. Functional performance was evaluated by regenerated ciliary area, ciliary beat frequency and ciliary transport function determined by measuring the moving distance of microspheres dropped onto the trachea (µm/s). The evaluation time points were 2 weeks, 1 month, 2 months and 6 months after surgery (n = 5, respectively). Forty rats underwent implantation, and all survived. Histological examination confirmed ciliated epithelization on the luminal surface after 2 weeks. Neovascularization was observed after 1 month, tracheal glands after 2 months and chondrocyte regeneration after 6 months. Although the material was gradually replaced by self-organization, tracheomalacia was not bronchoscopically observed at any time point. The area of regenerated cilia significantly increased between 2 weeks and 1 month (12.0% vs 30.0%; P = 0.0216). The median ciliary beat frequency significantly improved between 2 weeks and 6 months (7.12 vs 10.04 Hz; P = 0.0122). The median ciliary transport function was significantly improved between 2 weeks and 2 months (5.16 vs 13.49 µm/s; P = 0.0216). The novel PGA material showed excellent biocompatibility and tracheal regeneration both morphologically and functionally 6 months after tracheal implantation.

AbstractSealing element of frac plugs have crucial roles to isolate target zones of the well in hydraulic fracturing. If the zonal isolation by the sealing element is not adequate, it can result in erosion of the casing. The effect of casing deformation on sealing performance of sealing element is not well researched or understood. To study the effect of casing deformation on sealing performance, finite element analysis of sealing element in deformed casing was conducted in this study to assess the effect of casing deformation on sealing performance. In this study, finite element simulation of a full frac plug with three different casings ovalities (0%, 2%, and 5%) and three different sealing element designs (O-ring type, short type, traditional long type) was conducted to evaluate deformation behavior and sealing performance of the sealing elements in the deformed casings. Compression pressure on the casing by sealing element after the plug is set in the casing and the risk of leak were discussed and compared for each design. In the casing with 0% ovality, all the sealing element designs established contact with inner surface of the casing when setting force is applied. However, for the O-ring type design, area in contact with the casing was small and it may result in leak and erosion in the actual well if there is a small dent or deformation on the casing. When there is deformation and ovality in the casing, the minor ID has a smaller ID and a major ID has a larger ID compared to nominal ID of the casing. In the casing with 2% and 5% ovality, neither O-ring type nor short type sealing element could contact the major ID of the casing and there was a gap between inner surface of the casing and the sealing element. This gap can cause erosion of the frac plugs and casing when fluid passes through the gap. In contrast, traditional long type sealing element contacted both major and minor IDs of the casing and no gap was observed. This result indicates that there is a potential risk of insufficient isolation of target zones and erosion of casings in actual well condition if frac plugs with small sealing element is used. Since there are various types of frac plugs with different sealing element designs, this study helps to select proper frac plugs with good sealing element design and mitigate the risk of erosion of casings and plugs.

We investigated the occurrence of solvent cracking in unplasticized polyvinyl chloride pipes using test materials prepared by conventional methods. We confirmed that voids were formed on the inner surface of the pipe at a holding time of 2 weeks under conditions of room temperature (298 K), 1.0 g of applied adhesive, and 4 N/m U-band tightening torque. The voids formed linearly in the circumferential direction at regions in contact with the U-band and linearly in the axial direction at regions not in contact. Environmental agents of tetrahydrofuran (THF), 2-butane, and cyclohexanone were detected during analysis of void regions on the inner surface of the pipe and residual gas in the pipe. The results suggest that the stress generated by tightening of the U-band and the environmental agents affected void generation. Furthermore, stress analysis simulation of the U-band contact region show the presence of tensile stress at regions in contact with the U-band and compressive stress at regions not in contact. The difference in these stresses and the regularity of the molecular arrangement during manufacturing of the pipe likely influences the direction of void generation, which can progress into cracks.

We investigated the evolution of the γ-phase spherulites of poly(vinylidene fluoride) (PVDF) added to 1 wt% of tetrabutylammonium hydrogen sulfate during the isothermal crystallization at 165 °C through polarized optical microscopy and light scattering measurements. Optically isotropic domains grew, and then optical anisotropy started to increase in the domain to yield spherulite. Double peaks were seen in the time variation of the Vv light scattering intensity caused by the density fluctuation and optical anisotropy, and the Hv light scattering intensity caused by the optical anisotropy started to increase during the second increase in the Vv light scattering intensity. These results suggest the two-stage evolution of the γ-phase spherulites, i.e., the disordered domain grows in the first stage and ordering in the spherulite increases due to the increase in the fraction of the lamellar stacks in the spherulite without a change in the spherulite size in the second stage. Owing to the characteristic crystallization behavior, the birefringence in the γ-phase spherulites of the PVDF/TBAHS was much smaller than that in the α-phase spherulites of the neat PVDF.

Microplastics have recently been identified as one of the major contributors to environmental pollution. To design and control the biodegradability of polymer materials, it is crucial to obtain a better understanding of the aggregation states and thermal molecular motion of polymer chains in aqueous environments. Here, we focus on melt-spun microfibers of a promising biodegradable plastic, polyamide 4 (PA4), with a relatively greater number density of hydrolyzable amide groups, which is regarded as an alternative to polyamide 6. Aggregation states and thermal molecular motion of PA4 microfibers without/with a post-heating drawing treatment under dry and wet conditions were examined by attenuated total reflectance-Fourier transform infrared spectroscopy and wide-angle X-ray diffraction analysis in conjunction with dynamic mechanical analysis. Sorbed water molecules in the microfibers induced the crystal transition from a meta-stable γ-form to a thermodynamically stable α-form via activation of the molecular motion of PA4 chains. Also, the post-drawing treatment caused a partial structural change of PA4 chains, from an amorphous phase to a crystalline phase. These findings should be useful for designing PA4-based structural materials applicable for use in marine environments.