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Satellite laser communication is a promising solution to satisfy the increasing demand for high-capacity wireless communications. Satellite laser communication has several advantages over its radio frequency counterparts, such as a higher capacity with a broader bandwidth and transmission security provided by highly directional laser beams. However, the received optical power fluctuations induced by atmospheric scintillation cause burst errors, requiring the employment of high-performance error correction codes, such as turbo or low-density parity check (LDPC) codes. Recently, polar code has been attracting significant attention, primarily because of its lower encoding and decoding computational complexity and its high performance, reaching the Shannon limit. We have reported a long-distance experiment using 7.8-km terrestrial free-space optical (FSO) communication links and compared the performance of polar and LDPC codes. Our experimental results revealed the advantage of polar codes over LDPC codes when channel state information (CSI) was not available. In FSO communications suffering from atmospheric fading, it is known that we can enhance the error-correction performance of these codes by utilizing a channel equalization technique based on the estimated CSI. In this study, we present the results of long-distance transmission experiments using polar codes with channel equalization. As a result, equalization improves the error-correction performance. Moreover, even with channel equalization, the block error rate of polar codes is better than that of LDPC codes, as in our previous report.

Quantum key distribution (QKD) is a technology to securely share keys against any attack physically permitted, with the principle of quantum mechanics. In recent years, the satellite QKD, which employs artificial satellites as trusted mobile nodes, has been attracting attention in order to overcome the bottleneck of transmission distance. However, in the satellite QKD, quality degradation due to atmospheric effects is expected, as in ordinary satellite laser communications. Therefore, it is desirable to apply an error-correcting code (ECC) that has high error-correcting performance even under the atmospheric-induced effects to the error-correcting process of the satellite QKD. Therefore, in this paper, we examined the application of polar codes, which is known as an ECC with high error correction capability. First, in order to optimize the error correction efficiency, we propose a method to adaptively obtain an appropriate code rate for the received signal strength that changes momentarily due to atmospheric effects. Then, we compare the throughput performances with polar codes to it with low-density parity-check (LDPC) codes, with the numerical simulation assuming Bennett-Brassard 1984 protocol (BB84).

Introduction Under the current pandemic situation of the coronavirus disease 2019 (COVID-19), we have newly developed a commercially available device named Endomask to prevent the diffusion of droplets from subjects undergoing esophagogastroduodenoscopy (EGD). Herein, we evaluate the efficacy and safety of the device, and also evaluate the stress of the device on the operators and the subjects of EGD. Methods The efficacy of the device was evaluated using an experimental model that simulated the environment of EGD. The safety of the device was evaluated clinically by means of measuring the oxygen saturation and the expiratory carbonic dioxide partial pressure of subjects with our device during EGD. The stress of the device on the operability of the endoscopists and the respiration of the subjects were evaluated using questionnaires. Results In the experiments with Endomask, the percentage of the area with simulated droplets was significantly reduced compared to that without our device (median, 0.24% vs. 6.96%, p = 0.009). The saturation of oxygen and the expiratory carbonic dioxide partial pressure of subjects with the device did not show significant change at any recording times. Neither the operators nor the subjects felt serious stress from examination with the device. Conclusions Endomask could remarkably and safely prevent the diffusion of droplets without serious stress. Endomask is expected to contribute to a reduction of the infectious risk of SARS-CoV-2 in endoscopy units during COVID-19 pandemic.

Appropriate management of constipation in hemodialysis patients has not been established, although constipation is the most frequent gastrointestinal complication in dialysis patients. We herein report the efficacy and safety of polyethylene glycol in constipated hemodialysis patients assessed prospectively. Seven patients using stimulant laxatives participated in this study. Polyethylene glycol was administered to reduce stimulant laxatives during the six-week intervention period. The amount of stimulant laxatives decreased and spontaneous bowel movements with ideal stool consistency increased significantly after the intervention. No serious adverse effects were observed throughout this study. In conclusion, polyethylene glycol can be a useful tool for managing constipated hemodialysis patients.

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The effect of plasticizer content on the vibration absorbing properties for polyurethane elastomers was investigated. A natural frequency appeared on the frequency spectra at around 100 Hz. The natural frequency linearly decreased, and the transmissibility also decreased with the plasticizer content. Magnetic elastomers containing carbonyl iron particles with a dimeter of 7.0 mm also showed a natural frequency at ~260 Hz, and the natural frequency significantly decreased with the plasticizer content. The decrease in the transmissibility with the plasticizer content was larger than that for polyurethane elastomers. The natural frequency for magnetic elastomers increased by several ten Hz by a magnetic field of 60 mT although the transmissibility was independently of the plasticizer content. The effect of load on the natural frequency for these elastomers was also investigated, and it was found that the natural frequency is proportional to the storage modulus, G, with different two slopes depending on the mass of the system, m. The linear relation between the natural frequency and (G’/m)1/2 revealed that the observed vibration can be basically described by a simple harmonic oscillation.

Free-space optical (FSO) communications can offer secure connectivity thanks to the high directionality of the laser beam and the line-of-sight configuration. These security advantages are employed to realize high-speed key establishment between two distant parties, which is provably secure against an eavesdropper with unlimited computational resources. Besides, a well-maintained laser beam divergence allows group key agreement (GKA) among multiple parties. Here, we propose a novel method of GKA over FSO link—FSO-GKA. After numerically characterizing fundamental behaviors, we present a proof-of-concept demonstration of FSO-GKA using a 7.8-km terrestrial link. We achieve a group key rate of roughly 8 Mbps over a 58dB-loss channel based on 10-MHz on-off keying. We also investigate information leakage risks under several atmospheric conditions, which provides the basis for security certification of FSO-GKA. Our proposed scheme shows a new way to construct high-speed key exchange platforms.

We propose a self-validating scheme to calculate the unbiased responses of quantum many-body systems to external fields of arbibraty strength at any temperature. By switching on a specified field to a thermal pure quantum state of an isolated system, and tracking its time evolution, one can observe an intrinsic thermalization process driven solely by many-body effects. The transient behavior before thermalization contains rich information on excited states, giving the linear and nonlinear response functions at all frequencies. We uncover the necessary conditions to clarify the applicability of this formalism, supported by a proper definition of the nonlinear response function. The accuracy of the protocol is guaranteed by a rigorous upper bound of error exponentially decreasing with system size, and is well implemented in the simple ferromagnetic Heisenberg chain, whose response at high fields exhibits a nonlinear band deformation. We further extract the characteristic features of excitation of the spin-1/2 kagome antiferromagnet; the wavenumber-insensitive linear responses from the possible spin liquid ground state, and the significantly broad nonlinear peaks which should be generated from numerous collisions of quasi-particles, that are beyond the perturbative description., published version; 6 pages with 3 figures, and Supplemental Material

The effect of a weak magnetic field on vibration transmissibility was investigated for magnetic elastomers with various volume fractions of magnetic particles. Polyurethane elastomers without magnetic particles exhibited a natural frequency at 53 Hz and were insensitive to a magnetic field of 60 mT. The natural frequency for magnetic elastomers with a volume fraction of 0.23 was 115 Hz at 0 mT, and increased to 134 Hz at 60 mT. The vibration transmissibility was independent of the magnetic field. A linear relation between the natural frequency and (G/m)1/2 was observed (G: storage modulus, m: mass), indicating that the observed vibration is basically described by a simple harmonic oscillation.

Recently, the free space optical (FSO) communications have been widely studied as an alternative for large capacity communications and its possible implementation in satellite and terrestrial laser links. In satellite communications, clouds can strongly attenuate the laser signal that would lead to high bit-error rates or temporal unavailability of the link. To overcome the cloud coverage effects, often site diversity technique is implemented. When using multiple ground stations though, simplified optical system is required to allow the usage of more flexible approaches. In terrestrial laser communications, several methods for optical system simplification by using a multimode fiber (MMF) have been proposed.

We present practical GHz-clocked QKD systems, next generation entanglement QKD technologies, and QKD platform to manage the secure keys and to support a variety of applications. We then show the intrinsic limit of QKD, i.e., a key rate bound, and discuss how to realize the provable (information theoretic) security with a larger secrecy capacity over longer distances. In particular, we present a basic theory of physical layer cryptography, which characterizes the secrecy capacity, and engineers the tradeoff between the efficiency of reliable transmission and secrecy of communication. We introduce a concept to unify these schemes in photonic network, referred to as quantum photonic network. Future issues for realizing this new network paradigm are discussed.

Cholangiocarcinoma is an aggressive malignant tumor originating from intrahepatic or extrahepatic bile ducts. Its malignant phenotypes may be assumed by cancer stem cells (CSC). Here, we demonstrate that CD274 (PD-L1), known as an immunomodulatory ligand, has suppressive effects on CSC-related phenotypes of cholangiocarcinoma. Using two human cholangiocarcinoma cell lines, RBE and HuCCT1, we attempted to isolate the CD274(low) and CD274(high) cells from each cell line, and xenografted them into immunodeficient NOD⁄scid⁄γcnull (NOG) mice. We found that the CD274(low) cells isolated from both RBE and HuCCT1 are highly tumorigenic in NOG mice compared with CD274(high) cells. Furthermore, the CD274(low) cells possess several CSC-related characteristics, such as high aldehyde dehydrogenase (ALDH) activity, reduced reactive oxygen species production and a dormant state in the cell cycle. Furthermore, depletion of CD274 expression by shRNA in RBE cells enhances their tumorigenicity and increases ALDH activity. These findings are compatible with our observation that clinical cholangiocarcinoma specimens are classified into low and high groups for CD274 expression, and the CD274 low group shows poorer prognosis when compared with the CD274 high group. These results strongly suggest that CD274 has a novel function in the negative regulation of CSC-related phenotypes in human cholangiocarcinoma, which is distinct from its immunomodulatory actions.

Gastric acid measurement is useful in assessing the effectiveness of antisecretory drugs, however, the conventional tests involve invasive nasogastric intubation. Orally administered ¹³C-labeled calcium carbonate (Ca¹³CO₃) reacts with gastric acid to produce ¹³C-labeled carbon dioxide (¹³CO₂), which is then excreted in the breath. The objective of this study was to evaluate the suitability of Ca¹³CO3 breath test for estimating gastric acid secretion in human noninvasively. First, the Ca¹³CO₃ breath test and the measurement of pooled gastric acid under a fasting condition were performed in 6 healthy volunteers to evaluate the correlation between the two parameters. Next, endoscopic gastric acid collection and the Ca¹³CO₃ breath test were performed on different days after pentagastrin injection in 20 subjects to evaluate the correlation between the tests and the reproducibility. Finally, the same studies were repeated in 4 subjects before and after 1-week rabeprazole, a proton pump inhibitor, administration. The maximum CO₂ concentration (Cmax) correlated very well with the amount of pooled gastric acid (r = 0.95), suggesting that Ca¹³CO₃ breath test values well reflected the fasting intragastric acidity. The ¹³CO₂ concentration after pentagastrin injection correlated well with pentagastrin-stimulated maximal acid output (r = 0.79 at 20 min). The reproducibility of the Ca¹³CO₃ breath test under pentagastrin-stimulation was good (coefficient of variation = 0.11). Rabeprazole administration markedly reduced the values of the Ca¹³CO₃ breath test, suggesting that it can sensitively assess the efficacy of rabeprazole. The Ca¹³CO₃ breath test can potentially be a useful method for non-invasive estimation for gastric acid secretion in human.

Quantum communication and quantum cryptography are expected to enhance the transmission rate and the security (confidentiality of data transmission), respectively. We study a new scheme which can potentially bridge an intermediate region covered by these two schemes, which is referred to as quantum photonic network. The basic framework is information theoretically secure communications in a free space optical (FSO) wiretap channel, in which an eavesdropper has physically limited access to the main channel between the legitimate sender and receiver. We first review a theoretical framework to quantify the optimal balance of the transmission efficiency and the security level under power constraint and at finite code length. We then present experimental results on channel characterization based on 10 MHz on–off keying transmission in a 7.8 km terrestrial FSO wiretap channel. This article is part of the themed issue ‘Quantum technology for the 21st century’.

Background: Metabolic acidosis is known to accelerate the progression of chronic kidney disease (CKD). However, whether undetermined anions as indicated by the adjusted anion gap (aAG) are associated with estimated glomerular filtration rate (eGFR) decline in patients with CKD is unclear. Methods: Data from 42 patients with CKD (baseline eGFR, 7.1-52.0 ml/min/ 1.73 m2) without massive proteinuria (urinary protein-creatinine ratio, UPCR Results: The mean baseline eGFR was 27.5 ± 11.1 ml/min/1.73 m2 and the mean %ΔeGFR/6m was 13.8 ± 10.3. UPCR and aAG were 1.13 ± 0.93 and 9.48 ± 1.88, respectively. %ΔeGFR/6m was associated with aAG (r = 0.438, p < 0.005), but not with UPCR (r = 0.194, p = 0.218). In multivariate linear regression analyses, aAG remained significantly associated with %ΔeGFR/6m (β = 0.45, p < 0.01) after controlling for age, baseline eGFR, UPCR and HCO3- concentration. Conclusion: These data suggest that aAG appears to be associated with the progression of CKD. aAG might be an independent predictor of CKD progression.

We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security., Comment: 16 pages, 8 figures

Although Helicobacter pylori (H. pylori) eradication has some inhibitory effects on the subsequent development of gastric cancer, there are sporadic cases of gastric cancer even after successful eradication. The pathogenesis of gastric cancer emerging after H. pylori eradication remains to be clarified. In this study, employing Congo-red chromoendoscopy, which is capable of visualizing the acid-secreting fundic mucosa, we investigated the topographic relationship of the acid secretion pattern to the occurrence site of gastric cancers emerging after eradication. Fourteen consecutive patients who suffered from new gastric cancer after eradication, defined as lesions that were discovered at least 2 years after the eradication, were prospectively enrolled. Whether the neoplasias arose from acid-secreting or non-acid-secreting areas was evaluated with Congo-red chromoendoscopy. Biopsy specimens taken from the two areas were subjected to histologic evaluation and immunohistochemistry for Ki-67 and p53. The mean period from the eradication to the subsequent occurrence of gastric cancer was 74 (44) months. There were two cancer lesions in 5 cases, and thus there was a total 19 lesions from 14 cases. Congo-red chromoendoscopy revealed that all 19 lesions arose exclusively from non-acid-secreting areas. Histological examination revealed sustained hyperproliferation and accumulation of p53 protein was frequently detectable in non-acid-secreting areas. Genetic alteration such as p53 mutation seems to be already present in the residual non-acid-secreting areas after eradication, areas that could be the origin of gastric carcinogenesis after eradication. Identification of such high-risk areas should be a promising approach for estimating the individual cancer risk after eradication.

Helicobacter pylori infection is the major cause for mucosa-associated lymphoid tissue (MALT) lymphoma and gastric cancers. On the other hand, gastric cancers are known to arise from gastric mucosal atrophy. We here report a case of signet ring cell gastric cancer that developed after radiation therapy for MALT lymphoma in H. pylori-uninfected patient whose stomach did not show gastric mucosal atrophy. A 58-year-old female was referred to our hospital for treatment of gastric MALT lymphoma. This patient was not infected with H. pylori, and upper gastrointestinal endoscopy revealed that she did not have gastric mucosal atrophy but had submucosal tumor-like MALT lymphoma lesion in the anterior wall of the upper gastric body. Since conventional eradication therapy was ineffective, her whole stomach was irradiated as a second-line therapy. The MALT lymphoma lesion turned into complete remission state after the therapy. The patient was followed every 6 months by upper gastrointestinal endoscopy for 4 years as complete remission until a newly developed decolorized depressed lesion was detected in the greater curvature of the proximal antrum, a completely different location from the MALT lymphoma lesion. A biopsy specimen from the lesion contained signet ring cell carcinoma, and she was successfully treated by endoscopic submucosal dissection. No signs of recurrence have been detected so far. The radiation therapy for MALT lymphoma might be associated with the occurrence of this signet ring cell gastric cancer, and since MALT lymphoma is indolent in nature, this case suggests that careful consideration is required when choosing the second-line therapy for MALT lymphoma patients.

Free space optical (FSO) communications are enabling high-speed global wireless networks. Thanks to the highly directional nature of laser beam, they also yield a greater security advantage over radio frequency counterparts. When combined with a scheme of secret key agreement (SKA), FSO-SKA can establish at high speed a symmetric secret key which cannot be decrypted even by unbounded computer resources. Although there have been many theoretical studies on SKA, experimental investigations have been quite lacking, especially on quantifying eavesdropping risks and secret key rates in realistic environment. Here, we report the first full-field implementations of FSO-SKA in a 7.8-km terrestrial link with a probing station, enabling the estimation of eavesdropping risks. We attain the final key rates from 100 kbps to 7.77 Mbps under various atmospheric and beaming conditions even with total losses of 55dB or higher, in which known quantum key distribution schemes attain impractically low key rates.

We investigate the secret key rates for the recently proposed intensity-modulated dual-threshold key distribution [T. Ikuta and K. Inoue, New J. Phys. 18 (2016)] under beam splitting attacks. We show that previous assumptions on an eavesdropper that performs hard decision measurements on the channel, overestimates the secret key rate. We discuss the impact of an eavesdropper that can measure full soft information and give the secret key rates under forward and reverse reconciliation. Further, we perform simulations for different system assumptions and show the optimal modulation depths for these systems. We also outline an attack on this protocol based on photon counting that prohibits secret key generation.

Secret key agreement using physical properties of a wireless channel is becoming a promising scheme to establish a secret key between two users, especially in short-distance radio frequency (RF) communications. In this scheme, the existence of codes or key distillation that can make the leaked information to an eavesdropper arbitrarily small can be derived in an information theoretical way, given a priori knowledge on the channel linking a sender (Alice), a legitimate receiver (Bob), and an eavesdropper (Eve), which is called the wiretap channel. In practice, however, it is often difficult for Alice and Bob to get sufficient knowledge on Eve. In this study, we implement a free-space optical wiretap channel in a 7.8 km-terrestrial link and study how to estimate Eve's tapping ability, demonstrating high speed secret key agreement in the optical domain under a certain restricted condition of line-of-sight.

A device consisting of a phase of magnetic elastomer, a phase of polyurethane foam (PUF), and permanent magnet was fabricated and the stress?strain curves for the two-phase magnetic elastomer were measured by a uniaxial compression measurement. A disk of magnetic elastomer was adhered on a disk of PUF by an adhesive agent. The PUF thickness was varied from 1?mm to 5?mm while the thickness of magnetic elastomers was constant at 5?mm. The stress at a strain of 0.15 for the two-phase magnetic elastomers was evaluated in the absence and in the presence of a magnetic field of 410 mT. The stress at 0 mT decreased remarkably with the PUF thickness due to the deformation of the PUF phase. On the other hand, the stress at 410 mT slightly decreased with the thickness; however, it kept high values even at high thickness. When the PUF thickness was 5?mm, the maximum stress increment with 45 times to the off-field stress was observed. An experiment using ping-pong balls demonstrated that the coefficient of restitution for the two-phase magnetic elastomers can be dramatically altered by the magnetic field.

Phase equilibrium was established in the Y–Fe–O system at 1100°C by varying the oxygen partial pressure from −log( P O 2 /atm)=15.00 to 0, allowing construction of a phase diagram at 1100°C for the system Y 2 O 3 –Fe–Fe 2 O 3 . In the system, two ternary compounds, YFeO 3 and Y 3 Fe 5 O 12 , were stable and had nonstoichiometric composition, whereas YFe 2 O 4 was not found to be stable. The present result was different from that of previous studies at 1200°C, in which YFe 2 O 4 was stable, along with the above two ternary compounds. Lattice constants of YFeO 3 and Y 3 Fe 5 O 12 , prepared in air by a quenching method, were determined and compared with previous values, and showed close agreement. The standard Gibbs energy changes of the reactions in the Fe–O system, Fe+1/2O 2 =FeO, 3FeO+1/2O 2 =Fe 3 O 4 , and 2/3Fe 3 O 4 +1/6O 2 =Fe 2 O 3 , were determined, and the obtained values were compared with the previous values. The standard Gibbs energy changes of the reactions, Fe+1/2Y 2 O 3 +3/4O 2 =YFeO 3 , and 3YFeO 3 +2/3Fe 3 O 4 +1/6O 2 =Y 3 Fe 5 O 12 , were calculated from the oxygen partial pressures in equilibrium.

Many kinds of gasification systems are under development now. Heating value of gaseous fuels produced from solid fuel (wastes and biomass) gasification systems are as low as 1/10 of that of natural gas, and there is almost no established energy conversion methods for such low-BTU gases. Two kinds of low-BTU gas, one was produced by diluting from natural gas with nitrogen and the other was produced from the two-step pyrolysis/reforming gasification process were tested in a dual fueled diesel engine. In these experiments, power output could be kept constant by controlling the gas oil supply, when low-BTU gas supply changed. It was demonstrated that nearly 80% of oil supply could be replaced by low-BTU fuel gas with slight decrease of the thermal efficiency while significant reduction of NOx emission was possible due to lower combustion temperature in the engine. Experimental results show that dual fueled diesel engines are quite feasible option for efficient utilization of low-BTU gases.

Loose-abrasive machining with ceria, zirconia or iron oxide slurry is traditionally employed for finishing optical glass. The machining process, however, has problems involving inefficiency and a detrimental impact on environment. Therefore, it is strongly recommended that the process be replaced with fixed-abrasive machining, but conventional fixed-abrasive tools have problems relating to low finishing efficiency or low finished surface quality. In this study, a lapping film utilizing agglomerative fine abrasives is introduced for finishing optical glass to overcome the above problems. The finishing experiments revealed that the good surface quality was comparable to that obtained by polishing with ceria slurry and the finishing efficiency was much higher. Furthermore, it was found that in the process of finishing, agglomerative abrasives were worn flat uniformly and gradually, that is, the self-dressing action of agglomerative abrasive occurred continuously.

Woodceramic thin films were prepared onto alumina sheet and glass slide substrates by conventional radio frequency sputtering in an argon plasma. A woodceramic disk, 100 mm in diameter, sintered at 850°C was used as a target. The deposition rate was about 90 nm/h for 200 W input power. Remarkable differences were observed in the characteristics of films depending on the substrate temperature. Films prepared below 100°C had insulating properties, ρ > 106 Ω cm, and had transmission in the visible region (λ > 600 nm), and had smooth surfaces. Increasing the substrate temperature causes sharp a decrease in the film resistivity and the growth of grain was 3–5 μm. The film prepared at 300°C had semiconductor characteristics with an energy gap of about 0.05 eV.

Highly resistant, high-transmittance woodceramic thin films were prepared using rf magnetron sputtering of a woodceramic disk in argon plasma. A film series was deposited based on substrate temperature, which was varied from 50 to 500°C. The film's electrical and optical properties depended on substrate temperature. Films deposited below 300°C were insulative, ρ>1010Ω·cm. Films deposited at 50°C had a density of 1.9-2.2g/cm3 comparable to that of single crystal graphite. Below 200°C, films had higher transmittance than typical DLC films in the visible and infrared region. Infrared C-H absorption spectrum was observed by FT-IR and there exist two types of bonding corresponding to sp2 or sp3.

Wood and bamboo ceramics are newly developed porous carbon materials from wood and bamboo impregnated with resin, and they possess some special properties and can be expected to be used as electromagnetic materials, absorbents, catalyst carrier materials, etc. In this work, the graphitization behavior of wood and bamboo ceramics was investigated by X-ray diffraction. Experimental results show that the d002 spacing of the bamboo carbon, wood and bamboo ceramics decreased and the apparent graphite crystallite size Lc(002) increased with the increase of graphitization temperature. However, even after heat treatment at 3273 K, the d002 and Lc(002) value was only about 0.341 and 9 nm, respectively. These results indicate that all of the bamboo carbon, wood and bamboo ceramics investigated are typical non-graphitizable carbon or hard carbon.

There are two major trends of PM material development. The first is PM products application to the structural parts of automobiles which were originally made of conventional cast iron, carbon steel or alloyed steel.The PM materials were improved based on the alloyed material design, optimum manufacturing process and conditions to obtain comparable mechanical properties with them. The second is unique PM materials having heat and wear resistant properties utilizing PM advantage of flexibility in alloy elements and microstructures. It is understood that there is getting no economical advantage of the PM materials for the former application unless any further new development concept implemented.In this paper, existing concerns for PM materials to be more widely applied to the automobiles and future trend of their development are mentioned focusing on iron base materials.

The wiretap channel has been devised and studied first by Wyner, and subsequently extended to the case with non-degraded general wiretap channels by Csiszar and Korner. Focusing mainly on the Poisson wiretap channel with cost constraint, we newly introduce the notion of reliability and security functions as a fundamental tool to analyze and/or design the performance of an efficient wiretap channel system. Compact formulae for those functions are explicitly given for stationary memoryless wiretap channels. It is also demonstrated that, based on such a pair of reliability and security functions, we can control the tradeoff between reliability and security (usually conflicting), both with exponentially decreasing rates as block length n becomes large. Two ways to do so are given on the basis of concatenation and rate exchange. In this framework, the notion of the {\delta} secrecy capacity is defined and shown to attain the strongest security standard among others. The maximized vs. averaged security measures is also discussed., Comment: 60 pages, 12 figures

Exposure of the esophageal mucosa to refluxed gastroduodenal contents is recognized to be an important risk factor for Barrett's esophagus (BE). At the human gastroesophageal junction, nitric oxide is generated luminally through the enterosalivary recirculation of dietary nitrate, and in cases with gastroesophageal reflux, the site of luminal nitric oxide generation could shift to the distal esophagus. The aim of this study is to investigate whether exogenous luminal nitric oxide could promote the development of BE in rats. Sodium nitrite plus ascorbic acid were administered to a rat surgical model of BE, in which the gastroduodenal contents were refluxed into the esophagus to generate exogenous luminal nitric oxide in the esophagus by the acid-catalyzed chemical reaction between the 2 reagents. The emergence of BE was evaluated histologically in the early phase (several weeks) after the surgery with or without exogenous nitric oxide administration. To elucidate the histogenesis of BE, CDX2, MUC2 and MUC6 expressions were investigated immunohistochemically. Coadministration of sodium nitrite plus ascorbic acid significantly accelerated the timing of emergence and increased the area of BE compared with controls. Administration of either reagent alone did not show any promotive effects on BE formation. Immunohistochemically, the columnar epithelium thus induced was similar to the specialized intestinal metaplasia in human BE. The results of this animal model study suggest that exogenous luminal nitric oxide could be involved in the pathogenesis of the columnar transformation of the esophagus. Further studies in human are warranted.