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Low-flow blood pumps rated under 1 L/min are emerging for new medical applications, such as hemofiltration in acute use. In those pumps, platelet adhesion and aggregation have to be carefully considered because of clogging risk in the filter part. To find an acceptable hemocompatibility that can be applied to low-flow centrifugal blood pump design, the platelet aggregation index, clogging on a micromesh filter, and the hemolysis index were investigated using a low-flow blood pump designed for hemofiltration use. We conducted circulation testing in vitro using fresh porcine blood and two centrifugal pumps with different impeller inlet shapes. The Negative Log Platelet Aggregation Threshold Index (NL-PATI), which reflects the ability of residual platelets to aggregate, and flow rate were measured during reflux for 60 min, and the Normalized Index of Hemolysis (NIH (g/20 min)) was calculated. In addition, blood cell clogging after reflux was observed on the micromesh filter by SEM, and the adhesion rate was calculated. Our results showed that the platelet clogging on the micromesh filter occurred when the average NL-PATI was greater than 0.28 and the average NIH (g/20 min) was greater than 0.01. In contrast, platelet clogging on the micromesh was suppressed when NL-PATI was less than 0.17 and the NIH (g/20 min) was less than 0.003. These values might be used as acceptable hemocompatibility of low-flow centrifugal blood pumps with suppressed platelet clogging for hemofiltration pumps.

The effects of electron beam irradiation were examined on perforation holes and fragments from quasi-isotropic carbon fiber reinforced plastic plates (CFRP plates). CFRP plates with a total dose up to 60 MGy of electron beam irradiation were prepared for hypervelocity impact experiments. The perforation holes of CFRP plates in the hypervelocity impact experiments were decreased with electron beam irradiation when aluminum alloy spherical projectiles (2017-T4) of diameter of 1 mm struck at an impact velocity of 5 km/s. However, a slight reduction in the size of the perforation hole was observed at 2 km/s. Fragments ejected from CFRP plates were examined after collection from the impact side and rear side of the targets. The cumulative number distributions of fragment length and aspect ratio were compared among specimens with different total doses.

Introduction: Real-time, non-invasive monitoring of thrombus formation in extracorporeal circuits has yet to be achieved. To address the challenges of conventional optical thrombus detection methods requiring large devices that limit detection capacity, we developed a micro-optical thrombus sensor. Methods: The proposed micro-optical thrombus sensor can detect the intensity of light scattered by blood at wavelengths of 660 and 855 nm. Two thrombus sensors were installed on in vitro circuit: one at the rotary blood pump and one at a flow channel. To evaluate the variation in the ratio of incident light intensity at each wavelength of the two sensors, Rfluct (for 660 nm) and Ifluct (for 855 nm) were defined. Using fresh porcine blood as a working fluid, we performed in vitro tests of haematocrit (Hct) and oxygen saturation (SaO2) variation and thrombus detection. Thrombus tests were terminated after Rfluct or Ifluct showed a larger change than the maximum range of those in the Hct and SaO2 variation test. Results: In all three thrombus detection tests, Ifluct showed a larger change than the maximum range of those in the Hct and SaO2 variation test. After the tests, thrombus formation was confirmed in the pump, and there was no thrombus in the flow channel. The results indicate that Ifluct is an effective parameter for identifying the presence of a thrombus. Conclusion: Thrombus detection in an extracorporeal circuit using the developed micro-optical sensors was successfully demonstrated in an in vitro test.

Topoisomerase I (TOP1) controls the topological state of DNA during DNA replication, and its dysfunction due to treatment with an inhibitor, such as camptothecin (CPT), causes replication arrest and cell death. Although CPT has excellent cytotoxicity, it has the disadvantage of instability under physiological conditions. Therefore, new types of TOP1 inhibitor have attracted particular attention. Here, we characterised the effect of a non-camptothecin inhibitor, Genz-644282 (Genz). First, we found that treatment with Genz showed cytotoxicity by introducing double-strand breaks (DSBs), which was suppressed by co-treatment with aphidicolin. Genz-induced DSB formation required the functions of TOP1. Next, we explored the advantages of Genz over CPT and found it was effective against CPT-resistant TOP1 carrying either N722S or N722A mutation. The effect of Genz was also confirmed at the cellular level using a CPT-resistant cell line carrying N722S mutation in the TOP1 gene. Moreover, we found arginine residue 364 plays a crucial role for the binding of Genz. Because tyrosine residue 723 is the active centre for DNA cleavage and re-ligation by TOP1, asparagine residue 722 plays crucial roles in the accessibility of the drug. Here, we discuss the mechanism of action of Genz on TOP1 inhibition.

To enhance bone regeneration, the use of bone morphogenetic protein (BMP)-2 is an attractive option. Unfortunately, the dose-dependent side effects prevent its widespread use. Therefore, a novel osteogenic agent using a different mechanism of action than BMP-2 is highly desirable. Previous reports demonstrated that prostaglandin E2 receptor 4 (EP4) agonists have potent osteogenic effects on non-human cells and are one of the potential alternatives for BMP-2. Here, we investigated the effects of an EP4 agonist (AKDS001) on human cells with a rat heterotopic xenograft model of human bone. Bone formation in the xenograft model was significantly enhanced by AKDS001 treatment. Histomorphometric analysis showed that the mode of bone formation by AKDS001 was minimodeling rather than remodeling. In cultured human mesenchymal stem cells, AKDS001 enhanced osteogenic differentiation and mineralization via the cAMP/PKA pathway. In cultured human preosteoclasts, AKDS001 suppressed bone resorption by inhibiting differentiation into mature osteoclasts. Thus, we conclude that AKDS001 can enhance bone formation in grafted autogenous bone by minimodeling while maintaining the volume of grafted bone. The combined use of an EP4 agonist and autogenous bone grafting may be a novel treatment option to enhance bone regeneration. However, we should be careful in interpreting the results because male xenografts were implanted in male rats in the present study. It remains to be seen whether females can benefit from the positive effects of AKDS001 MS by using female xenografts implanted in female rats in clinically relevant animal models.

Postoperative over-telescoping (OT) with lag screws is often observed in reverse oblique intertrochanteric fractures. This study aimed to clarify the risk factors of OT in patients with reverse oblique intertrochanteric fractures.Electronic medical records of patients diagnosed with reverse oblique intertrochanteric fractures using plain radiography who underwent operative fixation with an intramedullary nail between August 2013 and December 2019 were reviewed. Patients were classified into two groups according to the Futamura classification: lateral wall pattern (LW) and reverse oblique pattern (RO). The incidence of OT in the LW and RO groups was compared. Also, we compared the incidence of OT for each reduction type in the LW group.Twenty patients had LW, and nine had RO. OT was observed in eight fractures (42.1%) in the LW group but not in the RO group. The incidence of OT was significantly higher in the LW group than in the RO group (P = 0.0261). Among the 19 fractures with LW, OT was observed in 7 of 10 and 1 of 9 fractures with postoperative reduction in the intramedullary and extramedullary or anatomical types, respectively. In the LW group, the incidence of OT was significantly higher in fractures with postoperative reduction in the intramedullary type than in those of the extramedullary or anatomical type (P = 0.0198).Our study showed that the incidence of OT was significantly higher in LW than in RO and that postoperative reduction in the intramedullary type in LW was a risk factor for OT.

Nylon 66 is an engineering plastic with the advantageous characteristics of light weight, heat resistance, high strength, and high rigidity; it has been used in automobile parts as a substitute for aluminum alloys. There have also been many studies on the mechanical properties of nylon 66. However, the flow stress in nylon 66 after necking has not been thoroughly investigated yet due to the difficulty in identifying local stress. In this study, a flow stress optimization method based on the digital image correlation (DIC) method and response surface method, is proposed. The averaged true stress–true plastic strain curve is first obtained by a quasi-static tensile test via DIC. Subsequently, the flow stress is optimized via the response surface method to obtain the actual flow stress state after necking. The accurate flow stress in the specimen can be obtained based on the relationship between the global load force and distance between the two shoulders of the specimen grip parts that is unaffected by the cross-sectional area change during necking. The results indicate that the average true stress recorded from the experiment overestimates the flow stress after necking. The optimized flow stress exhibits the maximum decrease of 9%. The accuracy of the optimized flow stress is evaluated by comparison with the true strain distribution on the specimen that is accurately measured via DIC.

This study examines how gamma ray irradiation affects the penetration holes in and fragment sizes from carbon fiber reinforced plastic (CFRP) plates due to hypervelocity impacts. In order to do so, quasi-isotropic CFRP plates made of unidirectional pre-impregnated sheets and 1-mm-diameter spherical projectiles made of aluminum alloy (2017-T4) were used. Witness plates (200 mm × 200 mm × 2 mm) made of copper (C1100P-1/4H) and containing a 30-mm-diameter hole were placed 50 mm in front of and behind each target to examine the fragments based on ISO 11227. The fragments collected from the impact and rear sides of the target were compared. Gamma ray irradiation had a slight effect on the penetration hole, the fragment size distributions, and the craters on the witness plates. When the gamma ray irradiation was 10 MGy, the penetration holes at impact velocities of 2.4 km/s and 5.3 km/s became slightly smaller. At the impact velocity of 2.4 km/s, perforation of the 0.5 MGy, 6.5 MGy, and 10 MGy specimens prevented the projectile from fracturing.

When aluminum alloy 2017-T4 spheres strike thick aluminum alloy 6061-T6 targets at 4 km/s, the size of fragments collected from a test chamber was measured and the effects of impact angle on the size and projected area of the fragments were examined. Impact angle clearly affected the size distribution and projected area distribution of the fragments. The cumulative number of fragments as a function of fragment length and projected area was proportional to the normal component of the impact velocity raised to the power 1.5. When the cumulative number on the vertical axis was divided by the normal component of the impact velocity raised to the power 1.5, experimental formulas with respect to fragment length and projected area were proposed using a bilinear exponential distribution function. The crater shapes on the targets were also examined, as were the area and shape of the indentations created by fragment particles on the witness plate. Their relationship to fragment size distribution was discussed. These results will assist in the revision of ISO 11227 with respect to oblique impact conditions.

In exploration for a methodology to analyze fast deformation of a thick specimen where a state of equilibrium cannot be assumed, high-speed impact tests on pumice-stone and granite sample specimens are conducted with Hopkinson bar test apparatus. A compressive stress pulse from the input bar is applied to the specimens ranging from 8 mm to 30 mm in thickness. The stresses on the front (input-bar) side and the rear (output-bar) side of the specimen are evaluated separately based on the strain gauge signals from the input and output bars. Optical emission from the specimen is captured with a photomultiplier. Analyses on the time variation of the strain gauge and photomultiplier signals lead to the following observations. (a) The front-side stress plays an important role in the deformation and fracture, (b) the transition from the elastic to plastic regime can be estimated from oscillatory features observed in the front-side stress and other quantities derived from the strain gauge signals, (c) the optical emission is highly correlated with the front side stress and step-wise energy loss in the specimen, and (d) the main frequency components of the stress wave associated with the energy-loss are found in the same frequency band as conventional acoustic emissions observed in rock fractures. A question remains, and provides an interesting subject for future study, regarding the step-wise energy loss observed in the strain gauge signal unaccompanied by the optical emission. In view of a recent fracture mechanical theory that states the evolution of fracture is accompanied by a reduction in frequency on the emission spectrum, it is possible that these energy loss is associated with emission in frequency ranges outside the sensitivity of the photomultiplier.

Multi-center, retrospective cohort study.To determine the epidemiology, identify predictors of early mortality, and develop predictive models for traumatic spinal cord injury (SCI).Despite improved initial care and management strategies, traumatic SCI remains a devastating event. Knowledge of the epidemiological state and predictive factors for mortality is important for developing strategies and counseling; however, they have not been adequately investigated, and predictive modeling regarding outcomes remains an underused modality for patients with traumatic SCI.Using a nationwide trauma registry-the Japan Trauma Data Bank-we identified adult (≥18 yrs) patients with SCI between 2004 and 2015. The endpoint was in-hospital mortality. Characteristics of each patient were described. Multivariate logistic regression analyses were performed to identify factors significantly associated with in-hospital mortality and develop a predictive model.In total, 236,698 patients were registered in the database. Of the 215,835 adult patients, 8069 (3.7%) had SCI. The majority had SCI at the cervical level with falls at ground level being the primary etiology. Over the study period, median age, the proportion of cervical SCI, and the etiology of falls at ground level increased. The mortality rate was 5.6%. The following eight factors, age, sex, Glasgow Coma Scale on arrival (GCS), hypotension on arrival, bradycardia on arrival, severe head injury, Injury Severity Score (ISS), and neurological severity of SCI, were independently associated with mortality. A predictive model consisting of these variables predicted mortality with area under the receiver operating characteristic curve of 0.88 (95% confidence interval [CI], 0.86-0.90).Over the 12-year period, patient characteristics, etiology, and post-SCI outcomes significantly changed. We identified eight prognostic factors of early mortality. A predictive model including these factors showed excellent performance and may improve treatment strategies, healthcare resource allocation, and counseling.3.

Details of the mechanism underlying the tensile properties of plasticized polyhydroxyalkanoates (PHA) including poly(butylene succinate) (PBS) were investigated by blending with poly(ε-caprolactone) (PCL) as well as the addition of compatibilizers. Multi-scale instrumental analyses employed micro-focus X-ray CT to provide micro-scale morphology information on the order of ten microns while solid-state NMR spectral and relaxation time analyses contributed knowledge of the environment and molecular mobility of each constituent at the molecular to nano-scale. The blend of plasticized PHA with 50% PCL adopted a sea-island morphology to improve elongation at break in a quasi-static tensile test, which was dominated by the tensile properties of the added PCL. However, impact tensile properties were less improved by PCL addition, because its molecular mobility was suppressed by blending. Meanwhile, peroxy crosslinkers changed the sea-island morphology to homogenous in X-ray CT observations. Although the homogenous morphology sharply lowered the elongation at break in a quasi-static tensile test, the homogenous morphology improved impact tensile properties. Furthermore, graft polymers having acrylonitrile-styrene side-chains did not change the sea-island morphology but increased the molecular mobility of PBS in the plasticized PHA. This weak interaction between the plasticized PHA and PCL improved tensile properties in both quasi-static and impact tensile tests.

We have developed a hydrodynamically levitated centrifugal blood pump. In the blood pump having hydrodynamic bearings, the narrow bearing gap has a potential for high hemolysis. The purpose of the this study is to improve hemolysis performance in a hydrodynamically levitated centrifugal blood pump by optimizing a shroud size. The impeller was levitated passively at the position where the thrust forces acting on the impeller were balanced. We focused on a size of a bottom shroud with a hydrodynamic bearing that could change the bottom hydrodynamic force to balance the thrust force at the wide bearing gap for reducing hemolysis. Five test models with various shroud size were compared: 989 mm2 (HH-10.5), 962 mm2 (HH-12), 932 mm2 (HH-13.5), 874 mm2 (HH-16), and 821 mm2 (HH-18). A numerical analysis was first performed to estimate the bearing gaps in the test model. The bearing gaps were then measured to validate the numerical analysis. Finally, an in vitro hemolysis test was performed. The numerical analysis revealed that the HH-13.5 model had the widest bearing gap of 129 µm. In the measurement test, the estimation error for the bearing gap was less than 10%. In the hemolysis test, the HH-13.5 model achieved the lowest hemolysis level among the five models. The present study demonstrated that the numerical analysis was found to be effective for determining the optimal should size, and the HH-13.5 model had the optimal shroud size in the developed hydrodynamically levitated centrifugal blood pump to reduce hemolysis.

This work investigates the plasma skimming effect in a spiral groove bearing within a hydrodynamically levitated centrifugal blood pump when working with human blood having a hematocrit value from 0 to 40%. The present study assessed the evaluation based on a method that clarified the limitations associated with such assessments. Human blood was circulated in a closed-loop circuit via a pump operating at 4000 rpm at a flow rate of 5 L/min. Red blood cells flowing through a ridge area of the bearing were directly observed using a high-speed microscope. The hematocrit value in the ridge area was calculated using the mean corpuscular volume, the bearing gap, the cross-sectional area of a red blood cell, and the occupancy of red blood cells. The latter value was obtained from photographic images by dividing the number of pixels showing red blood cells in the evaluation area by the total number of pixels in this area. The plasma skimming efficiency was calculated as the extent to which the hematocrit of the working blood was reduced in the ridge area. For the hematocrit in the circuit from 0 to 40%, the plasma skimming efficiency was approximately 90%, meaning that the hematocrit in the ridge area became 10% as compared to that in the circuit. For a hematocrit of 20% and over, red blood cells almost completely occupied the ridge. Thus, a valid assessment of plasma skimming was only possible when the hematocrit was less than 20%. Electronic supplementary material The online version of this article (10.1007/s10047-020-01221-9) contains supplementary material, which is available to authorized users.

A suitable index is needed for hemolysis tests that use low-flow pumps, such as pediatric blood pumps or blood purification pumps. To create such an index, the present study investigates the change of plasma-free hemoglobin in the pump circuit with time and the change of the hemolysis rate with flow rate and impeller rotational speed. The results show that the hemolysis rate or the increase rate of the total free hemoglobin are suitable measures for hemolysis evaluation for low-flow pumps.

We describe a medicinal chemistry approach to the discovery of a novel EP1 antagonist exhibiting high potency and good pharmacokinetics. Our starting point is 1, an EP1 receptor antagonist that exhibits pharmacological efficacy in cystometry models following intravenous administration. Despite its good potency in vitro, the high lipophilicity of 1 is a concern in long-term in vivo studies. Further medicinal chemistry efforts identified 4 as an improved lead compound with good in vitro ADME profile applicable to long term in vivo studies. A rat fracture study was conducted with 4 for 4 weeks to validate its utility in bone fracture healing. The results suggest that this EP1 receptor antagonist stimulates callus formation and thus 4 has potential for enhancing fracture healing.

Accepted: 2017-08-07, 資料番号: SA1170125000

Because long period stacking ordered (LPSO) type magnesium alloys have the low density, excellent mechanical strength and ignition resistance, LPSO-type magnesium alloys have a great potential as structural materials of satellites. Ejecta size and crater shape were examined when spherical projectiles struck targets made of LPSO-type magnesium alloy at hypervelocities of 2 km/s and 5 km/s. After impact experiments, crater surfaces and lips near craters were observed X-ray computed cosmography (CT) in detail. Ejecta collected from test chamber were measured. Results of LPSO-type magnesium alloy targets were compared with those of aluminum alloy (A6061-T6). Fracture behavior of LPSO-type magnesium alloy targets seemed to be brittle and many small ejecta from LPSO-type magnesium alloy were observed., 14th Hypervelocity Impact Symposium 2017(HVIS2017), 24-28 April 2017, Canterbury, Kent, UK

Blast furnace iron ore pellets are sintered, centimetre-sized ore spheres with a high iron content. Together with carbonized coal, iron ore pellets are used in the production of steel. In transporting pellets from pelletizing plants to customers, iron ore pellets are exposed to different static and dynamic loading situations, resulting in strength degradation and, in some cases, fragmentation. This can lead to a reduced gas flow in the blast furnace, which causes reduced quality in steel production. Reliable numerical simulations that can predict the ability of the pellets to endure their handling are important tools for optimizing the design of equipment for iron ore handling. This paper describes the experimental and numerical work performed to investigate the impact fracture behaviour of iron ore pellets at different strain rates. A number of split Hopkinson pressure bar tests with different striker velocities are carried out and analysed to investigate the strain rate dependency of the fracture strength of iron ore pellets. Fracture data for iron ore pellets are derived and expressed in terms of statistical means and standard deviations. A stress based, strain-rate dependent fracture model that takes triaxiality into account is suggested. The fracture model is used and validated with impact tests of iron ore pellets. In the validation experiment, iron ore pellets are fired against a steel plate, and the percentage of fractured pellets at different impact velocities are measured. Finite element simulations of the experiment are carried out and the probability of pellets fracturing during impact are calculated and compared with the experimental results. The agreement between the experiments and numerical simulations shows the validity of the model.

This paper reports a newly developed micro optical sensor for detecting blood clotting in an artificial circulation apparatus, such as a blood pump. The sensor comprises three LEDs, CMOS chip, which has monolithically-fabricated photodiodes, and amplifier circuits. The small sensor size (2.8×2.8×0.4 mm3, after packaging with epoxy resin: 5.5×5.5×1.2 mm3) allowed it to be mounted and measure various points of the artificial circulation apparatus. We have evaluated the blood clotting detection performance using porcine blood. Then, we detected blood clotting in a blood pump by analyzing the change in the optical characteristics of blood that lead to clotting using the developed sensor. The micro optical sensor contributes to the development of a blood clotting monitoring system for artificial circulation apparatus.

Multi-vessel cervical arterial injury after blunt trauma is rare, and its pathophysiology is unclear. Although blunt cerebrovascular injury is a common cause of cerebral ischemia, its management is still controversial. We describe a 23-year-old man in previously good health who developed three-vessel cervical arterial dissections due to blunt trauma. He was admitted to our emergency and critical care center after a motor vehicle crash. Computed tomography showed a thin, acute subdural hematoma in the right hemisphere and fractures of the odontoid process (Anderson type III), pelvis, and extremities. He was treated conservatively, and about 1 month later, he developed bleariness. Computed tomography angiography showed bilateral internal carotid and left vertebral artery dissection. Aspirin therapy was started immediately, and then clopidogrel was added to the regimen. Two weeks later, magnetic resonance angiography (MRA) showed improved blood flow of the vessels. Only aspirin therapy was continued. About 3 months after discharge, MRA demonstrated further improvement of the blood flow of both internal carotid arteries, but the dissection flap on the right side remained. Therefore, we extended the duration of antiplatelet therapy. On the basis of our experience with this case, we think that antithrombotic therapy is crucial for the management of multi-vessel cervical arterial injury, and agents should be used properly according to the injury grade and phase; however, further study is needed to confirm this recommendation.

[Aim] To determine genotypes of Mycobacterium tuberculosis strains in Fukuoka Prefecture, Japan. [Methods] A total of 296 isolates from 296 tuberculosis patients is tested using 24-locus variable-number tandem- repeat (VNTR) typing. We also determined whether these isolates and a further 10 were Beijing lineage. [Results] The 296 isolates were classified into 264 VNTR types, and re-classified into 25 clusters when each cluster was defined as isolates being identical to VNTR types in 24 regions, or in 23 regions with the exception of one hypervariable region. Two clusters were shown to be identical to that of the Kansai regional epidemic. Regarding regional diversity, hypervariable regions showed relatively higher variation of isolate types. The Beijing lineage accounted for 78.1% of all isolates, which was similar to the value obtained from Kobe (78.5% in 2009) in the Kansai region. [Discussion] Six isolates from Fukuoka Prefecture over- lapped with those from Kansai region with respect to domi- nant VNTR type, while clusters from Fukuoka Prefectural isolates were unique, which may be a feature of Fukuoka prefectural isolates. [Conclusion] These data are likely to be useful for public health measures in the area.

The effect of a multi-functional epoxy-based chain extender on the tensile properties of poly( l -lactic acid) (PLLA)/poly(butylene succinate-co- l -lactate) (PBSL) blends was investigated using X-ray diffraction, differential scanning calorimetry, attenuated total reflection infrared spectroscopy, solid-state nuclear magnetic resonance spectroscopy, and scanning electron microscopy. The PLLA/PBSL blend without the chain extender showed low strain at break because of its immiscible sea-island morphology. The chain extender reacted with both PLLA and PBSL during the blending process to produce three types of graft polymers. The graft polymer formed by the reaction of the chain extender with both PLLA and PBSL at the PLLA/PBSL interface improved the miscibility and tensile properties of the blend through interfacial interactions. The graft polymers connected with either PLLA or PBSL existed within the PLLA or PBSL domains, respectively and suppressed the molecular motions due to the intra-domain interactions. When 4 % chain extender was used, the miscibility of the blend improved and the suppressed molecular motions of the PBSL portion increased the maximum stress and strain at break. At the chain extender concentration of 6 %, the miscibility of the blends did not increase; however, the interfacial and intra-domain interactions increased, which deteriorated the tensile properties of the blends.

In order to improve the mechanical properties of Polyhydroxyalkanoate (PHA), the polycaprolactone (PCL) pellet was blended with a PHA-based pellet. The effects of the mixing ratio on the tensile properties, Young's modulus, tensile strength and elongation at break, were examined using a universal testing machine. When the mixing ration of PCL increased to 50%, the elongation at break of the polymer blend increased and the gauge area of tensile test specimens whitened and became porous. In order to understand this behavior, a rheo-optical characterization technique based on near-infrared (NIR) spectroscopy was applied to the mechanical deformation of the polymer blends during static tensile tests. Two-dimensional (2D) correlation of NIR spectra was then examined. It was found from peaks of ethyl group or methyl group that PCL was preferentially deformed. The difference in the deformation behavior is thought to be the cause of the porous structure.

Bioplastics have attracted attention over the years from a perspective of environmental protection. Recently, attention is focused on bioplastics derived from inedible objects. Polyhydroxyalkanoates (PHAs) are known as a microbial origin plastic and expected to deal effectively with the food security issue. In this study, in order to use PHA for industrial and machinery parts and products, polycaprolactone (PCL) was blended with a PHA-based pellet to improve ductility and tensile strength. The effects of additives on tensile strength and elongation at break, dynamic tensile tests of the polymer blends were examined using split Hopkinson bar (SHPB) method at high strain rates.

Experiments and simulations on projectile impact to circular and rectangular plates made of aluminum alloy 2024-T3 were carried out. Ballistic limit and deformation of circular plates and rectangular plates at impact point were examined. The experimental results were compared with the simulation ones which calculated using the materials properties experimentally obtained. The effects of mesh size and fracture strain on both the crack limit velocity and the perforate limit velocity were discussed.

As a preliminary study, the effects of target temperature on ejecta size were examined at an impact velocity of 3.5 km/s with the goal of improving the ISO11227. At first, the size of each ejecta collected from test chamber, was examined by the image analysis software using a photograph of each ejecta (direct method). The cumulative number distributions of ejecta size were discussed. The effects of target temperature on ejecta size were small within a predictable range. After that, we compared the ejecta size distribution of the direct method with the results of the international standard method using witness plate (indirect method). The number of ejecta impact craters evaluated by the international standard method was very small at the high temperature. The results of international standard method using witness plate were easily influenced by temperature of target at the high temperature. It is highly possible that the international standard method underestimate the ejecta from target at high temperature.

The effect of the flow path geometry of the impeller on the lift-off and tilt of the rotational axis of the impeller against the hydrodynamic force was investigated in a centrifugal blood pump with an impeller supported by a single-contact pivot bearing. Four types of impeller were compared: the FR model with the flow path having both front and rear cutouts on the tip, the F model with the flow path having only a front cutout, the R model with only a rear cutout, and the N model with a straight flow path. First, the axial thrust and the movement about the pivot point, which was loaded on the surface of the impeller, were calculated using computational fluid dynamics (CFD) analysis. Next, the lift-off point and the tilt of the rotational axis of the impeller were measured experimentally. The CFD analysis showed that the axial thrust increased gently in the FR and R models as the flow rate increased, whereas it increased drastically in the F and N models. This difference in axial thrust was likely from the higher pressure caused by the smaller circumferential velocity in the gap between the top surface of the impeller and the casing in the FR and R models than in the F and N models, which was caused by the rear cutout. These results corresponded with the experimental results showing that the impellers lifted off in the F and N models as the flow rate increased, whereas it did not in the FR and R models. Conversely, the movement about the pivot point increased in the direction opposite the side with the pump outlet as the flow rate increased. However, the tilt of the rotational axis of the impeller, which oriented away from the pump outlet, was less than 0.8° in any model under any conditions, and was considered to negligibly affect the rotational attitude of the impeller. These results confirm that a rear cutout prevents lift-off of the impeller caused by a decrease in the axial thrust.

In vitro antithrombogenic testing with mock circulation is a useful type of pre-evaluation in ex vivo testing of mechanical assist devices. For effective in vitro testing, we have been developing a clear quantitative thrombogenesis model based on shear stress and blood coagulability. Bovine blood was used as the test medium. The activating clotting time (ACT) was adjusted with trisodium citrate and calcium chloride from 200 to 1,000 seconds. The blood was then applied to a rheometer and subjected to shear at 50 to 2,880 s-1. Blood coagulation time and degree of thrombogenesis were measured by the torque sensor of the rheometer. Prothrombin time (PT) and activated partial thromboplastin time (APTT) of the test blood were also measured after the application of shear. Blood coagulation time increased, and the degree of thrombogenesis decreased, with increases in shear rate to between 50 and 2,880 s-1. for test bloods with ACTs of 200 to 250 seconds. An ACT of 200 to 250 seconds is thus appropriate for in vitro antithrombogenic testing under a shear rate of 2,880 s-1. APTT was prolonged, whereas PT did not change, with increasing shear rate: that is, increasing the shear rate reduced thrombogenesis related to the intrinsic clotting pathway. An ACT of 200 to 250 seconds was suitable for in vitro antithrombogenic testing, and increasing the shear stress generated in the mechanical assist device reduced thrombogenesis via the intrinsic clotting pathway.

The aggregability of red blood cell (RBCs) is associated with the contribution of plasma proteins, such as fibrinogen and lipoproteids, to blood-clotting. Hence, we hypothesized that RBC aggregability reflects the blood-clotting reaction. A noninvasive optical monitoring method to measure RBC aggregability for the assessment of blood-clotting stage during mechanical circulatory support was developed. An in vitro thrombogenic test was conducted with a rotary blood pump using heparinized fresh porcine blood. Near-infrared laser light at a wavelength of 785 nm was guided by an optical fiber. The fibers for detecting incident, forward-, and backward-scattered light were fixed on the circuit tubing with an inner diameter of 1/4 inch. Because there is substantial RBC aggregation at low shear flow rates, a pulsatile flow was generated by controlling the pump rotational speed. The flow rate was changed from 0 to 8.5 L/min at a period of 40 s. The intensities of forward- and backward-scattered light changed dramatically when the flow stopped. The aggregability was evaluated by the increase ratio of the transmitted light intensity from the flow stopping in the low-flow condition. The experiment started when the anticoagulation was stopped by the addition of protamine into the circulating blood. Reduction in RBC aggregability was associated with a decrease in the amount of fibrinogen and the number of platelets. Continuous, noninvasive monitoring of thrombosis risk is possible using optical measurements combining pulsatile flow control of a rotary blood pump. RBC aggregometry is a potential label-free method for evaluating blood-clotting risk.

Micro scale torsion test method was developed to investigate continuous deformation behavior around initial yield point of copper single crystal structure. Continuous load–displacement curve was obtained by torsion test because dislocation burst phenomenon was suppressed by stress gradient and torsion stress direction which parallel to the specimen surface. In case that new constitutive law was applied to the simulation, crystal plasticity parameter of copper could be evaluated by parameter fitting which using load–displacement curve of experiment and simulation.