Detecting Magnetoelectric Effect in a Metallic Antiferromagnet via Nonreciprocal Rotation of Reflected Light.

Certain types of media breaking both space-inversion (P) and time-reversal (T) symmetries but preserving their combination PT exhibit the polarization rotation of reflected light even when that of transmitted light is prohibited. Such an effect is termed nonreciprocal rotation of reflected light (NRR). Although NRR shows nearly the same phenomenon as the magnetooptical Kerr effect or, equivalently, the Hall effect at optical frequencies, its origin is distinct and ascribed to a magnetoelectric (ME) effect at optical frequencies, i.e., the optical ME effect. Here we show the observation of NRR in a metallic antiferromagnet TbB_{4}. The result demonstrates that the ME effect in a metallic system, which is considered to be ill defined, can be detected using reflected light. Furthermore, we spatially resolve antiferromagnetic domains in TbB_{4} by microscope observations of NRR. Our work offers a unique way to probe the ME effect in metallic systems.

Electric field-induced magnetochiral dichroism in a ferroaxial crystal.

In a chiral medium, any mirror symmetries are broken, which induces unique physical properties represented by natural optical rotation. When electromagnetic waves propagate through a chiral medium placed in a magnetic field, the refractive index, or equivalently, the absorption encountered by the electromagnetic waves differs depending on whether it travels parallel or antiparallel to the magnetic field. Such a phenomenon is known as magnetochiral dichroism (MChD), which is the characteristic interplay between chirality and magnetism. Similar to chirality, the so-called ferroaxial order, an emergent ferroic state of crystalline materials, is also characterized by mirror symmetry breaking. In contrast to chiral materials, however, the mirror symmetry perpendicular to the crystalline principal axis is allowed in ferroaxial materials. In other words, chirality and thus phenomena unique to chirality can be induced by breaking the remaining mirror symmetry by applying an electric field. Here, we show electric control of chirality and resulting electric field-induced MChD (E-MChD) of the short-wavelength infrared region in a ferroaxial crystal, NiTiO3. We performed spectroscopy measurements of E-MChD by taking a difference of absorption coefficients obtained with and without electric and magnetic fields. As a result, E-MChD was observed around the excitation energy corresponding to Ni2+ d-d magnetic-dipole transitions. The result is nicely explained by adopting the theory of MChD concerning the pseudo-Stark splitting of the energy state. Ferroaxial materials therefore provide platforms to achieve electric control of chirality-related phenomena.

Switching Crystallographic Chirality in Ba(TiO)Cu4(PO4)4 by Laser Irradiation.

Switching crystallographic chirality is nontrivial because there is no simple conjugate field to chirality. Here we demonstrate chirality switching in an inorganic crystalline material by manipulating the boundaries of chiral domains with laser irradiation. Our study material is Ba(TiO)Cu4(PO4)4, exhibiting a chiral structure at room temperature and a chiral-achiral phase transition at 710 °C. By irradiation of a laser beam with a wavelength at which Ba(TiO)Cu4(PO4)4 exhibits strong optical absorption, local heating is induced. This leads to reconstructions of chiral domain boundaries, revealed by optical rotation measurements. In the reconstruction process, energetically unstable domain boundaries tend to be minimized, affecting resultant domain patterns. On the basis of this feature, we successfully manipulate chiral domain patterns by scanning the laser beam on the sample surface. Our findings provide a unique approach to controlling chirality in inorganic crystalline materials.

Observation of Ferrochiral Transition Induced by an Antiferroaxial Ordering of Antipolar Structural Units in Ba(TiO)Cu4(PO4)4.

Ferrochiral transition, i.e., a transition involving an emergence of chirality, provides an unique opportunity to achieve a nonvolatile reversible control of chirality with external fields. However, materials showing pure ferrochiral transitions, which are accompanied by no other types of ferroic transition, are exceedingly rare. In this study, we propose that a pure ferrochiral transition is achieved by a combination of antipolar and antiferroaxial orderings of structural units, and substantiate this proposal through a study of the chiral compound Ba(TiO)Cu4(PO4)4. Single crystal X-ray diffraction measurements have revealed that this material undergoes a second order ferrochiral transition whose order parameter is described by an antiferroaxial (staggered) rotation of antipolar structural units, thus demonstrating our proposal. Furthermore, by measuring spatial distributions of optical rotation, we successfully visualized a temperature evolution of ferrochiral domains across the transition temperature and demonstrated the relationship between chirality and optical rotation. This work provides a guide to find a pure ferrochiral transition, thus providing an opportunity to achieve a ferroic control of chirality.

Comparison of outcome in aortic dissection with single false lumen versus multiple false lumens: CT assessment.

PURPOSE: To investigate the clinical features and outcomes of type B multibarreled (multiple false lumens) aortic dissection (AD) compared with those of double-barreled (single false lumen) AD by using computed tomography (CT). MATERIALS AND METHODS: The ethics committee approved this study. Informed consent was waived. A total of 221 consecutive patients (127 men; median age, 62 years) with acute type B AD were evaluated by using CT. The clinical outcome, including AD-related events, AD-related deaths, and long-term survival, was retrospectively reviewed and compared with that of patients with double-barreled AD during the follow-up period (median, 60 months). Survival analysis was performed by using Kaplan-Meier analysis with the log-rank test within 10 years after onset. The Cox proportional hazards model was used to estimate the risk for AD-related events and death. RESULTS: In 201 of 221 patients (91.0%), double-barreled AD was identified at initial CT. In 20 of 221 patients (9%), multibarreled AD was identified at initial CT (n = 16) and follow-up CT (n = 4). In 15 of 20 patients (75%) with multibarreled AD, AD-related events occurred, and nine patients (45%) died of AD-related complications. Patients with multibarreled AD showed significantly poorer survival rates than patients with double-barreled AD (P = .0002). The presence of a multibarreled false lumen was the most powerful risk factor for AD-related deaths according to multivariate analysis (hazard ratio, 5.61; 95% confidence interval: 2.44, 12.90; P < .0001). CONCLUSION: Multibarreled AD occurs in 9% of acute type B dissections. The presence of multibarreled AD is a powerful predictor of AD-related deaths.

Quantification of lung perfusion blood volume (lung PBV) by dual-energy CT in pulmonary embolism before and after treatment: preliminary results.

The purpose was to investigate the quantification of lung perfusion blood volume (PBV) by dual-energy computed tomography (CT) in patients with pulmonary embolism (PE) before and after treatment. Twenty-five patients with PE underwent dual-energy CT angiography before and after treatment. In all 25 patients, pulmonary CT confirmed that there was no PE after treatment. This preliminary study demonstrated the possibility that quantification of lung PBV may reflect parenchymal arterial perfusion before and after treatment, including the compensatory increase of lung perfusion.

Bacterial peritonitis due to duodenal perforation by a fish bone in an elderly peritoneal dialysis patient.

The patient, a 77-year-old-man, began peritoneal dialysis (PD) in August 2005. In January 2009, he developed lower abdominal pain and cloudy PD effluent. A diagnosis of peritonitis was made and Escherichia coli was detected in cultures of the PD effluent. An abdominal computed tomography scan showed a fish bone in the duodenal wall. An upper gastrointestinal endoscopy was performed, and a 3-cm fish bone was removed. We thus recommend careful investigation with the possibility of enteric peritonitis from the intestinal tract when E. coli is detected in effluent cultures during PD.

Quantification of lung perfusion blood volume (lung PBV) by dual-energy CT in patients with and without pulmonary embolism: preliminary results.

OBJECTIVES: Recently, software has been used for quantification of lung PBV, which can be evaluated objectively; however, this technique is yet to be validated. The purpose was to investigate the clinical feasibility of the quantification of lung perfusion blood volume (lung PBV) by dual-energy CT in patients with pulmonary embolism (PE). MATERIALS AND METHODS: One hundred thirteen patients with clinical suspicion of PE underwent dual-energy CT angiography with a standard injection protocol. Patients were divided into each two groups with and without PE based on the presence of endoluminal clots on transverse diagnostic scans. We evaluated the quantification of lung PBV using a workstation. Associations between lung PVB and the numbers of pulmonary segments with PE were also evaluated. RESULTS: Thirty three of 113 (29%) patients were found to have endoluminal clots in the right and/or left lungs. The remaining 80 patients did not have endoluminal clots. In 33 patients, the mean number of segments with endoluminal clots was 5.2±3.3. For patient (whole lung)-based analysis, in patients with and without PE, mean lung PBVs were 20.8±2.3 and 28.7±6.8 Hounsfield Unit (HU), respectively, with a significant difference between the two groups (p<0.0001). In patients with PE, there was a significant correlation between lung PBV and the numbers of pulmonary segments with PE (R=0.57, p=0.0005). CONCLUSION: The findings of this preliminary study suggest that quantification of lung PBV may reflect the pulmonary artery perfusion, which is useful to evaluate pulmonary blood flow in patients with PE.

PET features of aortic diseases.

OBJECTIVE: Recently, several reports have highlighted the potential role of (18)F-FDG PET for the assessment of various aortic diseases based on FDG accumulation. In this article, we divided various aortic diseases into the following three groups on the basis of the mechanism of FDG accumulation: atherosclerosis, aortitis or periaortitis, and thrombus. Elucidating the mechanisms and patterns of FDG uptake in various aortic diseases provides valuable information for clinical management. CONCLUSION: PET findings can provide additional information for the diagnosis of aortic diseases and valuable information for clinical management. It is essential to understand the characteristics of FDG uptake in various aortic diseases for proper appreciation of PET findings.

Vascular complications of hepatic artery after transcatheter arterial chemoembolization in patients with hepatocellular carcinoma.

OBJECTIVE: The purpose of this article is to review the angiographic changes, development of collaterals, and possible complications after transcatheter arterial chemoembolization (TACE) in hepatocellular carcinoma (HCC). CONCLUSION: Extrahepatic collateral arteries can supply the tumor after repeated TACE. Knowledge of hepatic artery changes can help in repeated TACE procedures and reduce TACE time. Appreciation of the complications and collaterals may improve the outcome of patients with HCC.

Serum amyloid A is a useful marker to evaluate the disease activity of Takayasu's arteritis.

Takayasu's arteritis (TA) is a rare large vessel vasculitis that is difficult to diagnose in the early stages. Therefore, it is also very difficult to manage and prevent irreversible vascular damage in TA. A 19-year-old female patient with back pain was examined using [(18)F]-FDG-PET to detect the source of inflammation. Specific accumulation of [(18)F]-FDG was observed in the thoracic and abdominal aorta, leading to the diagnosis of TA. Corticosteroid treatment resulted in clinical remission. However, the serum amyloid A (SAA) levels remained elevated. A follow-up scan showed residual uptake of [(18)F]-FDG in the thoracic aorta suggesting subclinical vascular inflammation. Methotrexate was combined with the corticosteroid, and the elevated levels of SAA became normalized. The present case suggests that monitoring serum levels of SAA and [(18)F]-FDG-PET could help clinicians to make adequate treatment adjustments in TA patients.

Quantification of enhancement of left ventricular myocardium in patients with dilated cardiomyopathy using delayed enhanced MR imaging.

The purpose is to evaluate delayed enhancement (DE) of the myocardium in patients with dilated cardiomyopathy (DCM), compared with control subjects. We also evaluated the interrelationships of DE and contractile function. DCM patients (n = 42) and 14 control subjects were evaluated by DE MR imaging, acquired using a two-dimensional segmented inversion-recovery prepared gradient-echo sequence (TI = 250 ms), 15 min after intravenous administration of 0.2 mmol/kg gadolinium. For the myocardium of left ventricle (LV), we traced epicardial and endocardial borders, and regions of interest (ROIs) were placed in each slice. For analysis of DE images, the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) of the LV myocardium were calculated. The averaged SNR (aSNR) and averaged CNR (aCNR) per slice of the LV myocardium were calculated. In the DCM group, we also evaluated the interrelationship of DE and the contractile function of the LV. Mean aSNR was not significantly different between the studied groups; however, mean aCNR was significantly higher in the DCM group (3.5+/-3.1) than in control subjects (-4.1+/-2.1). In the DCM group, aCNR was moderately related to LV ejection fraction (LVEF) (r = 0.52, P<.0001). Mean aCNR was significantly higher in the DCM group with low LVEF (<25%) (6.0+/-2.8) than in the DCM group with high LVEF (>or=25%) (2.0+/-2.3). In DE MR imaging, the LV myocardium of DCM usually has high aCNR, which may suggest fibrosis. Quantification of aCNR may contribute to the diagnosis of DCM. The level of aCNR seems to correlate with LVEF. Using this technique, quantification of aCNR is objective and very useful for the diagnosis of DCM and contractile function of LV.