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Background Certain types of enteroviruses, including coxsackieviruses, cause encephalitis, and other neurological complications. However, these pathogens rarely cause fatal infections, especially in immunocompetent infants. In this study, we present a rare case of acute encephalopathy caused by coxsackievirus A2 (CV-A2), which progressed rapidly in a previously healthy female child. Case presentation In June 2013, a 26-month-old female child from Kanagawa, Japan, was found unresponsive during sleep. She was healthy until that morning. Her temperature was 37 °C at 08:00. She was feeling fine and went to the nursery that same morning. However, her condition worsened around noon. Therefore, she went home and slept at around 13:00. Surprisingly, after 2 h, her parents checked on her and found that she was lying on her back and was not breathing. Hence, she was immediately taken to a hospital by ambulance, but she was declared dead on arrival at the hospital. Subsequently, pathological autopsy and pathogenetic analysis, including multiple pathogen detection real-time PCR, were conducted to investigate the cause of death. The examination results revealed that she had an infectious respiratory disease and acute encephalopathy due to a CV-A2 infection. Conclusions Based on our findings, we concluded that a previously healthy girl who had no immediate history of underlying medical condition were susceptible to death by acute encephalopathy due to CV-A2 infections. We proposed this conclusion because the patient’s condition progressed rapidly in less than 2 h and eventually led to her death. This is the first report on an acute encephalitis-dependent death in a child due to CV-A2 infection.

Background The use of surgical metal clips is crucial for ligating vessels in various operations. The currently available metal clips have several drawbacks; they are permanent and interfere with imaging techniques such as computed tomography (CT) or magnetic resonance (MR) imaging and carry the potential risk of endo-clip migration. We recently developed a novel magnesium (Mg) alloy for biodegradable clips that reduces artifacts on CT imaging. This study aimed to examine the tolerance, biodegradability, and biocompatibility of the Mg alloy clips compared with those of standard titanium (Ti) clips in hepatectomy. Methods Thirty Wistar rats were divided into two groups based on the clip used (groups A and B). The vascular pedicle, including hepatic artery, portal vein, bile duct, and hepatic vein of the left lateral lobe, was ligated with the Ti clip in group A or the Mg alloy clip in group B, and then the left lateral lobe was removed. The rats were sacrificed at 1, 4, 12, 24, and 36 weeks after surgery. Clinical and histological evaluations were performed. Absorption rate was calculated by measuring the clip volume. Results Although the Mg alloy clips showed biodegradability over time, there were no significant differences in the serum concentration of Mg between the two groups. The remaining volume ratio of Mg alloy clips was 95.5, 94.3, 80.0, 36.2, and 16.7% at 1, 4, 12, 24, and 36 weeks, respectively. No side effects occurred. Most of the microscopic changes were similar in both groups. Conclusions The new biodegradable Mg alloy clips are safe and feasible in vessel ligation for hepatectomy in a rat model and reduce artifacts in CT imaging compared with the standard Ti clips.

Hot deformation behaviors accompanied with the development of new fine grains (NFGs) and microtexture were studied experimentally and numerically in a binary Mg-2.2 at% Y alloy by using compression test, SEM/OIM microscopy and full field crystal plasticity finite element modelling (CPFEM) method. NFGs are evolved along at original grain boundaries at low to medium strains and subsequently in grain interiors through grain fragmentation by frequent formation of kink bands in high strain. Such a series of strain-induced reactions occur in-situ during deformation. The addition of Y atoms to Mg results effectively in the appearance of much higher flow stress and also the slow development of NFGs even in high strain. Lattice orientations of NFGs are distributed almost randomly. The CPFEM results confirms that the dominant deformation mode changed from the combination of basal and prismatic slip system to the combination of pyramidal and basal slip system when deformation temperature increased from 673 K to 723 K, leading to a different microtexture between these two temperatures. Both mechanical and microstructural events are analyzed in detail and the operating mechanisms discussed.

To apply magnesium in biodegradable bone fixation devices, it is favorable to improve its properties through approaches such as by forming composites between magnesium and calcium phosphate. In this study, a powder metallurgical method was used to prepare composites of a magnesium–calcium alloy and α-tricalcium phosphate (α-TCP). Refinement of the α-TCP particle size caused more uniform distribution and microstructure. Consequently, the composite with finer α-TCP particle size had better ductility to the alloy lacking α-TCP. The biodegradation properties were improved by the addition of α-TCP, and the refinement of the α-TCP particles led to a slower degradation rate in electrochemical and immersion tests.

Syphilis, a sexually transmitted infection caused by the bacteriumTreponema palladium, is experiencing a worldwide resur-gence. The risk of syphilis infection is particularly high in men who have sex with men (MSM), especially those who are human immunodefi-ciency virus (HIV)-positive. Untreated syphilis can lead to rare but severe late-stage complications, including syphilitic aortitis. Herein, wepresent an autopsy case of a ruptured thoracic aneurysm that resulted from an undetected case of syphilitic aortitis in an HIV-positive JapaneseMSM with undiagnosed syphilis. Although no syphilitic skin lesions were observed on the body, anatomical changes consistent with a syphili-tic etiology were present at the site of the rupture, including medial aortic scarring with“tree-bark”-like atherosclerotic plaque. In addition,heart blood was positive forT. palladiumin a latex agglutination test. This case highlights for forensic pathologists the importance of recogniz-ing syphilis as a possible underlying cause of sudden death among HIV-positive MSM.

Paraquat (PQ) is one of the commonly used herbicides in the world, despite its high toxicity. The ingestion of PQ accidentally or intentionally causes severe damage in diverse organs including the lung. Pulmonary fibrosis triggered by PQ accumulation in the lung epithelial cells is one of the major causes of death. This study investigated the intracellular accumulation of PQ, reactive oxygen species (ROS) generation and mitochondrial injury using two lung epithelial cell lines A549 and BEAS-2B (BEAS). Although A549 exhibit greater resistance to oxidative stress than BEAS, a cytotoxicity assay for PQ demonstrated that EC50 for lethality in A549 was 7 times lower than that in BEAS. When exposed to PQ at a concentration around EC50 for lethality, the amount of ROS generated in A549 was as low as that in BEAS. Conversely, the cellular concentration of PQ in A549 after exposure was higher than that in BEAS, which suggests a distinct difference in the susceptibility to PQ between these cell lines. After a 16 h exposure to PQ, mitochondrial membrane potential (MMP) decreased in A549, but decreased only slightly in BEAS even following a 30 h exposure. PQ-exposed A549 reduced an accumulation of PTEN-induced kinase 1 (PINK1), which works in degradation of damaged mitochondria, following the decrease of MMP, whereas PQ did not decline the PINK1 in BEAS. These results suggest that mitochondrial dysfunction due to cellular accumulation of PQ might contribute to the PQ-provoked toxicity more than the ROS generation in the lung epithelial cells.

We present the first report of pneumopericardium observed by autopsy and on postmortem computed tomography (PMCT)images. The subject was a woman who died of self-inflicted stab wounds to the abdomen. The PMCT scan revealed air in the pericardial sac, a “flattened heart” sign, and retroperitoneal hemorrhage. Medicolegal autopsy revealed two abdominal stab wounds near the xiphoid process thathad cut the apical pericardium and adjacent diaphragm and liver. Examination of the open thorax confirmed that the pericardial sac was dis-tended with air. The wound extended to the abdominal aorta, causing retroperitoneal hemorrhage. PMCT images showed that the pneumoperi-cardial volume was 133 mL. We believe that cardiac tamponade occurred resulting from the tension pneumopericardium; however, the effectswere mitigated by hypovolemia secondary to the retroperitoneal hemorrhage as well as obstructive shock. Therefore, the cause of death appearsto have been low-pressure cardiac tamponade

The present study was designed to investigate the biodegradation behavior of Mg alloy plates in the maxillofacial region. For in vitro analysis, the plates were immersed in saline solution and simulated body fluid. For in vivo, the plates were implanted into the tibia, head, back, abdominal cavity, and femur and assessed at 1, 2, and 4 weeks after implantation. After implantation, the plate volumes and the formed insoluble salt were measured via micro-computed tomography. SEM/EDX analysis of the insoluble salt and histological analysis of the surrounding tissues were performed. The volume loss of plates in the in vitro groups was higher than that in the in vivo groups. The volume loss was fastest in the abdomen, followed by the head, back, tibia, and femur. There were no statistically significant differences in the insoluble salt volume of the all implanted sites. The corrosion of the Mg alloy will be affected to the surrounding tissue responses. The material for the plate should be selected based on the characteristic that Mg alloys are decomposed relatively easily in the maxillofacial region.

This study was designed to examine osteoconductive effects of Mg in rats tibia. The animals were sacrificed after 1, 2, and 8 weeks. The elemental analysis was performed using SEM/EDX at week 1. Following X-ray micrography at weeks 2 and 8, samples were embedded in paraffin. The expression of osteocalcin was observed by immunohistochemical staining. The element concentrations of fibrous capsules around the specimens were also measured by ICP-MS. The concentrations of Ca and P on the surface of the Mg specimen increased in SEM/EDX. The tissue specimen showed new bone formation on the bone surface near the implanted area. The concentrations of Mg, Ca, and P were high in the fibrous capsules surrounding Mg. Implantation induced differentiation of osteoblasts, and this process was considered to be associated with new bone formation. Induction of cell differentiation may be influenced by corrosion products in addition to corroding magnesium.

Drawing is suitable for manufacturing fine metal wire. This study was designed to clarify the effects of additive elements, calcium or zinc, on mechanical properties of drawn magnesium wires. Binary alloys of Mg-0.3 at. % Ca and Mg-0.1 at. % Zn were cast followed by extrusion. The extrusion bars were drawn to fabricate a fine wire with a diameter of 0.2 mm. Tensile tests were conducted for the wires. The results of the tensile tests confirmed that yield stress increased as the content of the solute element increased, while the work hardening rate and tensile ductility differed depending on the types of additive element. Inspection of the drawn microstructure revealed that the additive element plays an important role in microstructure evolution in magnesium.

In recent years, magnesium is expected to be used as a structural material in vehicles. Since limited slip systems in magnesium induces marked yield anisotropy and poor deformability at room temperature, there is a specific demand for developing magnesium alloys with reduced plastic anisotropy. In this study, we focused on the Mg–Al system alloy, which is widely used in commerce, and examined the third element contributing to the reduction of the plastic anisotropy. Generalized stacking fault energy (GSFE), which corresponds to the energy for sliding atomic layer along a slip plane, was calculated in the first-principles calculations to estimate deformability of ternary Mg–Al-X alloys adding the third element X, to the Mg–Al binary alloy. As the third element X, Zn, Zr, and Gd were selected. The slip properties were evaluated using the unstable stacking fault energy (USFE), which represents the maximum value of GSFE. The result suggested that the addition of zirconium contributes most to the reduction of plastic anisotropy.

Oxidative stress has been suggested to play a role in brain damage during carbon monoxide (CO) poisoning. Severe poisoning induced by CO at 3000 ppm, but not 1000 ppm, enhances hydroxyl radical (˙OH) production in the rat striatum, which might be mediated by NADPH oxidase (NOX) activation associated with Ras-related C3 botulinum toxin substrate (Rac) via cAMP signaling pathway activation. CO-induced ˙OH production was suppressed by antagonists of angiotensin II (AngII) type 1 receptor (AT1R) and type 2 receptor (AT2R) but not an antagonist of the Mas receptor. Suppression by an AT1R antagonist was unrelated to peroxisome proliferator-activated receptor γ. Angiotensin-converting enzyme inhibitors also suppressed CO-induced ˙OH production. Intrastriatal AngII at high concentrations enhanced ˙OH production. However, the enhancement of ˙OH production was resistant to inhibitors selective for NOX and Rac and to AT1R and AT2R antagonists. This indicates a different mechanism for ˙OH production induced by AngII than for that induced by CO poisoning. AT1R and AT2R antagonists had no significant effects on CO-induced cAMP production or ˙OH production induced by forskolin, which stimulates cAMP production. These findings suggest that the renin-angiotensin system might be involved in CO-induced ˙OH production in a manner independent of cAMP signaling pathways.

Purpose To develop a novel biocompatible solid fiducial marker that prevents radiopaque imaging artifacts and also maintains high imaging contrast for kilovoltage x-ray image-guided radiation therapy. Methods The fiducial marker was made of pure zinc. An in-house water-equivalent phantom was designed to evaluate artifacts and visibility under various simulated treatment scenarios. Image artifacts were quantitatively assessed in terms of the metal artifact index (MAI) on kilovoltage computed tomography (CT) and cone-beam CT (CBCT) scans. Marker visibility was evaluated on two types of kilovoltage planar x-ray images in terms of the contrast-to-background ratio (CBR). Comparisons with a conventional gold fiducial marker were conducted. Results The use of zinc rather than a gold marker mitigates imaging artifacts. The MAI near the zinc marker decreased by 76, 79, and 77 % in CT, and by 77 (81), 74 (80), and 79 (85) % in CBCT full-fan (half-fan) scans, when using one-, two-, and three-marker phantom settings, respectively. The high-contrast part of the zinc marker exhibited CBRs above 2.00 for 28/32 exposures under four (lung, tissue, low-density bone, and high-density bone) different simulation scenarios, making its visibility comparable to that of the gold marker (30/32 exposures with CBRs > 2.00). Conclusions We developed a biocompatible, artifact-robust, and highly visible solid zinc fiducial marker. Although further evaluation is needed in clinical settings, our findings suggest its feasibility and benefits for kilovoltage x-ray image-guided radiation therapy.

Magnesium alloys are promising lightweight structural materials. However, their practical utilization requires improvement of strength and ductility. Adding manganese as a solute improves the room-temperature ductility of magnesium alloys by facilitating grain boundary sliding, but its effects on deformation behavior under dynamic loading remain unclear. Accordingly, we investigated the strain rate dependence of both the flow stress and the deformation mechanism of Mg–Mn alloys via tensile tests over a wide range of strain rates. Grain boundary sliding induced relatively larger elongation under quasi-static conditions. On the contrary, the Mg–Mn alloy exhibited limited necking in the high strain rate regime dominated by intergranular fracture.

The effect of grain refinement on the yield stress of magnesium with calcium as the solid solute was investigated. Ultra-grain refinement down to 0.5 μm by extrusion under the controlled Zener–Hollomon parameter resulted in a high tensile yield stress over 400 MPa for biodegradable devices.

In this study, mechanical tests were conducted on a face-centered cubic FeCoNiCrMn high-entropy alloy, both in tension and compression, in a wide range of strain rates (10−4–104 s−1) to systematically investigate its dynamic response and underlying deformation mechanism. Materials with different grain sizes were tested to understand the effect of grain size, thus grain boundary volume, on the mechanical properties. Microstructures of various samples both before and after deformation were examined using electron backscatter diffraction and transmission electron microscopy. The dislocation structure as well as deformation-induced twins were analyzed and correlated with the measured mechanical properties. Plastic stability during tension of the current high-entropy alloy (HEA), in particular, at dynamic strain rates, was discussed in lights of strain-rate sensitivity and work hardening rate. It was found that, under dynamic conditions, the strength and uniform ductility increased simultaneously as a result of the massive formation of deformation twins. Specifically, an ultimate tensile strength of 734 MPa and uniform elongation of ∼63% are obtained at 2.3 × 103 s−1, indicating that the alloy has great potential for energy absorption upon impact loading.

Due to the excellent balance of strength and ductility exhibited by some Mg-Zn-RE (Y subgroup rare earth element) alloys, which contain icosahedral quasicrystalline precipitates, it is of interest to examine their deformation mechanisms. The internal strain evolution Mg-3at%Zn-0.5 at%Y with 4 vol% i-phase was measured using in-situ neutron diffraction. The extruded samples exhibit an initially weak || extrusion direction “rod texture,” distinct from the normally strong texture of extruded Mg alloys, but the grain size is unexceptional (16.7 ± 2.1 μm). The initially weak texture contributes to a nearly symmetric yielding response between tension and compression. The hardening responses are asymmetric, however, since {10.2} extension twinning is significantly more active during compressive straining, despite the initially weak texture. In-situ neutron diffraction tension and compression experiments parallel to the extrusion direction, together with elasto-plastic self-consistent (EPSC) crystal plasticity modeling, reveal the strength and hardening behavior of individual slip and twinning modes. The previously published twinning-detwinning (TDT) model is implemented within the EPSC framework, and it is proven effective for describing the observed, mild tension-compression asymmetry. This is not possible with previous EPSC-based models of twinning. Finally, the description of hardening within the TDT model is modified, in order to accurately describe the evolution of internal strains within the twins.

Addition of Al to equiatomic high entropy alloy CrMnFeCoNi alloy with a single phase FCC structure is known to promote formation of a BCC phase. In addition, tetragonal intermetallic phase σ was also found to form in a (CrMnFeCoNi)92Al8 alloy when subjected to processing by caliber rolling (8 passes) at room temperature followed by annealing at 800 ∘C. Microstructure of the as-rolled alloy is complex, containing a high dislocation density and planar faults (including twins) which can be parallel and perpendicular to the rolling direction. Morphological features of the transformations induced by straining by caliber rolling have been determined by transmission electron microscopy (TEM). Two main morphologies have been determined. In one type of morphology, bundles of elongated domains of B2 ordered BCC phase form preferentially on {111} matrix planes, inside which σ phase particles nucleate on interface with the matrix. In another type of morphology called “aggregate” here, “spines” of elongated grains of σ phase form, over which domains of B2 phase nucleate driven by change in solute concentration ahead of the interface. The σ phase forms by nucleation on planar faults in the matrix with its (001) plane, forming the known orientation relationship (OR) {001}σ ∥ {111}FCC and 〈110〉σ ∥ 〈110〉FCC. Since the planar faults in a caliber rolled alloy form parallel as well as perpendicular to the rolling direction, spines of the σ phase elongated in three mutually perpendicular directions are shown to exist. OR of the B2 phase with the matrix is Kurdjumov-Sachs. The B2 phase matched pairs of close packed planes with σ phase, but no particular or was found. Elemental concentration profiles across interfaces suggests that σ and B2 phases grow into the matrix. All the evidence suggests that the σ phase nucleates on the planar faults in the matrix, and then B2 phase forms by elemental concentration changes in the matrix caused by growth of the σ phase, forming the aggregate morphology.

An equiatomic CrMnFeCoNi alloy is usually a single-phase solid-solution with a face-centered cubic (fcc) structure. However, a Cr-rich σ phase with a tetragonal structure is formed in coarse-grained alloys after extended heat treatment between 873 K and 1073 K, which is indicative of metastability of the CrMnFeCoNi alloy. In this study, it was demonstrated that cold-working facilitated σ-phase formation during heat treatment at 1073 K in (CrMnFeCoNi)100−xAlx (x = 8 and 9 at%). More specifically, the heat treatment produced a unique σ–body-centered cubic (bcc) aggregate morphology in the unrecrystallized fcc matrix. Each aggregate was composed of σ-phase spine and bcc particles at the fcc/σ interface, and formed in a short period (0.5 h). It is suggested that aggregates precipitated on dislocations that were introduced by cold-working.

Fine and coarse grained (5–20 μm) and ultra-fine-grained (down to 1 μm) samples of a binary Mg-Al alloy were fabricated by extrusion at various temperatures. When tested in compression, a slight stress drop was observed after yielding, followed by a plateau in flow stress. This behavior is typical of textured fine-grained samples. Examination of deformed structures within the ultra-fine-grained samples at various levels of deformation showed that the stress drop after yielding is due to an occurrence of long, thin twins across low angle boundaries and in unrecrystallized regions. In the plateau region, extensive twinning occurs inside individual grains. Then, in a rapid strain hardening region that follows the plateau region, stress concentrations were found to build up on boundaries. Such pile-ups could be responsible for a lowering of fracture strain.

Here the pathophysiology of venous thromboembolism is reviewed with respect to the anatomical features of the deep veins of lower limbs. A thrombus is less likely to form in the thigh veins compared with that in the calf veins; however, clinical symptoms are more likely to appear in the thigh veins owing to vascular occlusion. When a patient is bedridden, thrombosis is more likely to occur in the intramuscular vein, which mainly depends on muscular pumping and the venous valve, rather than in the three crural branches, which mainly depends on the pulsation of the accompanying artery. Thrombi are prone to be generated in the soleal vein compared with those in the gastrocnemius vein because of the vein and muscle structures. A soleal vein thrombosis grows toward the proximal veins along the drainage veins. To prevent a sudden pulmonary thromboembolism-related death in bedridden patients, preventing soleal vein thrombus formation and observing the thrombus proximal propagation via the drainage veins are clinically important. When deep vein thrombosis occurs, avoiding embolization and sequela caused by the thrombus organization is necessary.

Equal channel angular extrusion (ECAE) was applied to an extruded Mg–1.0mass%Ca alloy to achieve a high strength and high damping capacity. Microstructure observations revealed that the texture and local misorientation distribution depend on the ECAE temperature. ECAE at a low temperature of 260 °C resulted in a high average Schmid factor of basal slip and a high kernel average misorientation in the processed alloy. Consequently, the alloy processed by ECAE showed a high yield strength without sacrificing the damping capacity.

Deformation structures have been examined by transmission electron microscopy after 4% plastic deformation in tension and compression in a Mg-2.2 at%Y alloy extruded at 698 K to obtain a recrystallized grain size of about 20 μ m . The extruded alloy showed similar yield stresses of about 240 MPa in both tension and compression at room temperature. Dislocations formed by tensile stress showed a tendency of 〈 a 〉 type dislocations to cross slip to prismatic planes, resulting in long continuous dislocation loops. Dislocation loops with 〈 c 〉 components were also observed. Occasionally, { 10 1 ¯ 2 } type twinning was also observed in grains with large orientation away from basal texture. These grains contained predominantly basal slip. Compression deformed samples showed a limited number of { 10 1 ¯ 2 } type twins. The matrix contained loops of non-basal 〈 a 〉 type dislocations, together with basal dislocations with 〈 c 〉 component. Inside the twins occurred stacking faults and loops of 〈 c 〉 type dislocations with segments perpendicular to the basal plane. Activation of several deformation modes and complex dislocation structures explains the strain hardening behavior and low anisotropy of the alloy.

Metallic medical devices are typically constructed from non-bioabsorbable metals that remains in the body and causes considerable complications. Particularly in the urinary tract, calculus, intractable infection, and misdiagnosis as calculus are often caused by non-bioabsorbable metals. Here, we developed a zinc–magnesium alloy as a new bioabsorbable metal and sought to evaluate the bioabsorbable behavior of zinc and zinc–magnesium alloy in a rat bladder implantation model. We prepared zinc–magnesium alloy wires with various proportions of magnesium and investigated the strength, shape retention, formability, and absorbability of these novel materials. Then, we implanted zinc and zinc–magnesium alloy rings formed by the wires into rat bladder. Rats were euthanized at the end of the observation period, and the rings were removed for volume evaluation. Extracted bladder tissues were subjected to histological analysis. The strength of the zinc wire was enhanced by more than fourfold upon the addition of magnesium, without loss of ductility. Linear reduction of ring volume in urine was observed based on the concentration of magnesium within the ring. Nearly all rings were covered with a thin layer of calculus. Histological findings of the transected urinary bladder tissues did not differ among groups. Zinc–magnesium alloy is a promising candidate for use as a bioabsorbable medical device in the urinary tract.

The impact of alloying elements on the room temperature tensile behaviour was investigated for a wide range of strain rates using eight types of extruded Mg-0.3 at.% X (X = Ag, Al, Li, Mn, Pb, Sn, Y and Zn) binary alloys with an average grain size of 2–3 μm. The solid solution alloying element affected not only tensile plasticity but also rate-controlling mechanism for these fine-grained magnesium alloys. Most of the alloys exhibited an elongation-to-failure of 20–50% , while the alloys with a high m-value exhibited large tensile plasticity, such as an elongation-to-failure of 140% in a strain rate of 1 × 10−5 s−1 for the Mg–Mn alloy. This elongation-to-failure is more than two times larger than that for pure magnesium. This is due to the major contribution of grain boundary sliding (GBS) on the deformation. Microstructural observations reveal that grain boundary segregation, which is likely to affect gain boundary energy, plays a role in the prevention or enhancement of GBS. The present results a...

We measured the impact toughness of three alloys (Mg, Mg-0.3 at%Ca-0.6 at%Zn, and Mg-0.3 at%Ca-0.6 at%Al) by the impact three-point bending test. The plastic deformability and impact toughness were higher in the ternary alloys than in pure Mg. The generalized stacking fault energy and grain boundary cohesive energy were estimated by first-principles calculations for Mg, binary Mg–Ca, ternary Mg–Ca–Zn, and ternary Mg–Ca–Al alloys. The calculation results agreed with the trend in the experimental results. We suggest that addition of Ca along with Zn or Al reduced plastic anisotropy and strengthened the grain boundaries, leading to higher in impact toughness of Mg alloys.

Superplastic deformation behavior was investigated for a dual-phase Mg-Ca alloy. The elongation-to-failure reached more than 120% with the strain rate sensitivity, m, over 0.4. The activation energy required for the deformation was estimated to be 98 kJ/mol which is close to the activation energy for grain boundary diffusion in magnesium. Therefore, the superplastic deformation mechanism was suggested to be the grain boundary sliding rate, which is controlled by boundary diffusion.