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In recent decades, there has been considerable worldwide progress in the treatment of gastric cancer. Gastrectomy with a modified D2 lymphadenectomy (sparing the distal pancreas and spleen) has increasingly gained acceptance as a preferable standard surgical approach among surgeons in the East and the West. Despite growing consensus significant differences still exist in surgical techniques in clinical trials and clinical practices secondary to variations in epidemiology, clinicopathologic features, and surgical outcomes among geographic regions. In addition, Western physicians tend to prefer adjuvant chemotherapy and radiotherapy after surgery instead of using S-1 chemotherapy, as is the preference in the East.

Background Prognosis for locally advanced gastric cancer (LAGC), such as clinical T4 disease, bulky nodal metastases, type 4 and large type 3 gastric cancer, was not satisfactory even by D2 gastrectomy followed by adjuvant chemotherapy. Neoadjuvant chemotherapy is another promising approach. We conducted a multi-institutional, single-arm, open label, phase II study (Clinical trial information: UMIN000018661). The aim of this study was to evaluate the efficacy and safety of the neoadjuvant chemotherapy of G-SOX followed by gastrectomy with D2/3 lymph node dissection for LAGC. Methods Eligibility criteria included histologically proven adenocarcinoma of the stomach; clinical T4; clinically resectable gastric cancer of type 4 or large type 3 (over 8 cm); bulky nodal metastases around major branched arteries to the stomach; resectable peritoneal dissemination (pathological CY1 or P1, except for clinical CY1 or P1). Patients received two cycles of neoadjuvant chemotherapy with S-1 (80 mg/m2, p.o., days 1-14 followed by 1 week rest) and oxaliplatin (130 mg/m2 at day 1), followed by D2 or higher surgery with no residual disease. Patients with pathological R0/1 resection received S-1 (80 mg/m2, p.o., days 1-28 followed by 2 week rest) for 1 year as adjuvant chemotherapy. Primary endpoint was curative resection rate. Results Forty-one patients were enrolled from 11 institutions. Of the patients, 39 patients (95%) completed the two courses of neoadjuvant chemotherapy of G-SOX, 37 (90%) received gastrectomy, and 36 (87.8%) received curative resection (R0/1). Pathological response rate after neoadjuvant chemotherapy of G-SOX was 40.5%. Most frequent drug-related adverse events during neoadjuvant chemotherapy of G-SOX were anemia (76%), neutropenia (66%), anorexia (63%) and peripheral sensory neuropathy (63%). No treatment related deaths were observed. Conclusions Neoadjuvant chemotherapy of G-SOX is a feasible and one of the promising strategies for patients with LAGC. Clinical trial identification UMIN000018661. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure H. Satake: Honoraria (self): Taiho; Honoraria (self): Yakult. M. Kotaka: Honoraria (self): Taiho; Honoraria (self): Yakult. T. Kato: Honoraria (self): Taiho; Honoraria (self): Yakult. A. Tsuji: Honoraria (self): Taiho; Honoraria (self): Yakult. All other authors have declared no conflicts of interest.

In recent decades, there has been considerable worldwide progress in the treatment of gastric cancer. Gastrectomy with a modified D2 lymphadenectomy (sparing the distal pancreas and spleen) has increasingly gained acceptance as a preferable standard surgical approach among surgeons in the East and the West. Despite growing consensus significant differences still exist in surgical techniques in clinical trials and clinical practices secondary to variations in epidemiology, clinicopathologic features, and surgical outcomes among geographic regions. In addition, Western physicians tend to prefer adjuvant chemotherapy and radiotherapy after surgery instead of using S-1 chemotherapy, as is the preference in the East.

The small bowel has been considered the "black box" of gastroenterology. Identifying the exact site of small bowel hemorrhage is often difficult, thus complicating surgical treatment. We report two cases of small bowel bleeding lesions that were successfully managed by intraoperative real-time capsule endoscopy and minimally invasive surgery.We developed a double-lumen tube similar to, but thinner and longer than, the Miller-Abbott tube. We insert the tube nasally, 3 or 4 days preoperatively, such that its balloon tip reaches the anus by the operative day. During surgery, the endoscopic capsule is connected to the balloon tip of the tube that protrudes from the anus. An assistant pulls on the nasal end of the tube, bringing the balloon tip and capsule back into the bowel. Capsule endoscopic images are displayed in a real-time video format.We employed this procedure in two patients with repeated melena. Various examinations including gastroendoscopy and total colonoscopy showed bleeding confined to the small bowel, but the exact lesion site was unknown. Minimally invasive surgery was successfully performed in both patients: open minilaparotomy in one and laparoscopy in the other. The small bowel and capsule endoscope were easily controlled during minilaparotomy, and real-time capsule endoscopic images clearly identified the bleeding lesion. Control of the small bowel was more difficult in the laparoscopic case; however, real-time capsule endoscopic images identified a small tumor that was successfully resected.Intraoperative capsule endoscopy combined with the tube provides surgeons real-time images indicating the exact site of lesions. The tube also helps surgeons control the position of the capsule endoscope and enables suction of intraluminal fluid or inflation of the lumen to allow clearer views during the operation. We conclude that combined use of capsule endoscopy and the tube facilitates management of bleeding lesions in the small bowel.

Electrogastrography (EGG) is a non-invasive diagnostic motility for recording gastric myoelectrical activity. Gastric myoelectrical activity was first recorded in 1922. Advances in recording equipment enabled widespread use of cutaneous EGG after 1985. Later, introduction of multichannel EGG (M-EGG) enabled measurement of electrical activity transmission. At present, M-EGG findings are used as objective indicators of gastric motility disorders caused by various diseases. EGG measures two categories of gastric electrical activity: electrical response activity, or spike potentials; and electrical control activity, or slow waves. The appearance of abnormal rhythmic electrical activity is indicative of abnormalities in gastric motility. The normal frequency range of gastric electrical activity (normogastria) is around 3 cycles per min. Multiple EGG parameters assist in the assessment of gastric myoelectrical activity, and significant correlations between EGG and other gastric motility tests have been demonstrated in many studies. In Japan, however, EGG remains in the exploratory stage, and its clinical use is limited. There are large variations in procedures and systems used in previous studies, thus there is a need for standardization of EGG procedures and technical terminology. Here, we outline the current status of EGG and report the M-EGG procedures used in our department in addition to our M-EGG findings. The abstract of this manuscript was presented during an educational seminar titled "Current status of gastrointestinal motility tests and keys for immediate implementation" at the 54th Annual Meeting of the Japan Society of Smooth Muscle Research

症例は76歳女性で糖尿病，慢性膵炎の既往がある．第12胸椎の圧迫骨折のため脊椎短縮術，後方固定，後側方固定術を施行された．腹臥位で，手術時間6時間20分であった．麻酔覚醒後から腹痛が出現し，術後1日目も腹痛は強く，膵酵素，WBC，CRPの上昇を認め，予後因子スコア5点で重症急性膵炎と診断．造影CTでは膵頭部の腫大および膵頭部内の造影不良域を認め，右腎下極以遠までの滲出液貯留を認めたため，造影CT grade 2と診断．蛋白分解酵素阻害薬・抗菌薬膵局所動注療法などの治療を行った．術後16日目の造影CTでは膵頭部の造影不領域が増大し，右後腹膜膿瘍も増大した．十二指腸の壁構造は消失し，十二指腸壁の壊死と考えられた．術後18日目に膵頭十二指腸切除術（PD）を行った．手術では十二指腸は広範に壊死に陥り，後腹膜膿瘍を形成していた．術後は縫合不全など大きな合併症はなく，PD術後101日に退院した．

症例は53歳，男性．幼少時から完全内臓逆位症と診断されていた．肛門痛を主訴に近医を受診し大腸内視鏡にて直腸にI sp型ポリープを指摘された．内科にてEndoscopic Submucosal Dissection（以下，ESD）が施行され，深達度smの直腸癌，脈管侵襲陽性と病理診断された．このため追加手術目的で外科に紹介された．患者のQOLを重視し，より低侵襲である腹腔鏡下直腸前方切除術を計画した．術前シミュレーションとして，正常解剖例の腹腔鏡下直腸前方切除術の手術動画を左右反転で再生，視聴し，イメージトレーニングを行った．ポート，術者の立ち位置等は通常の逆の位置にした．手術は予定通り腹腔鏡下直腸低位前方切除を行い，特に大きな問題もなく終了した．内臓逆位例でも術前のシミュレーションをし，慎重に解剖の同定を行えば腹腔鏡下手術も安全に施行できると思われた．

In this work, we address the issue of spin relaxation and its relevance to spin detection in ZnO-based materials, by spin-polarized, time-resolved magneto-optical spectroscopy. We have found that spin relaxation is very fast, i.e. about 100 ps for donor bound excitons in wurtzite ZnO, despite of a weak spin–orbit interaction. We also reveal that alloying of ZnO with Cd enhances spin relaxation, prohibiting ZnCdO/ZnO structures for efficient optical spin detection. On the other hand, a variation in strain field induced by lattice mismatch with substrates does not seem to lead to a noticeable change in spin relaxation. The observed fast spin relaxation, together with the limitation imposed by the band structure, are thus identified as the two most important factors that limit the efficiency of optical spin detection in the studied ZnO-based materials.

We report on the spectroscopic magnetooptical studies of spin dynamics in diluted magnetic semiconductor (DMS) GaAs / AlGaAs / ZnSe / ZnCdMnSe heterovalent double quantum wells (QW). The transients of circularly polarized photoluminescence in an external magnetic field are detected in the structures with different widths of the GaAs QW. The analysis of the data, performed within the rate-equation model, has allowed separate estimations of the spin relaxation rate of localized electrons and holes. The spin flip of the electrons confined in the DMS ZnCdMnSe QW is faster than 20 ps, whereas the spin flip of the heavy hole localized in the GaAs QW is as long as ~9 ns. The long spin flip of the holes is presumably governed by their strong 3-dimensional localization.

Spin polarization in carrier tunneling was studied in double quantum wells by the polarized photoluminescence-excitation spectroscopy. The double quantum wells consist of a diluted magnetic quantum well of Zn0.77Cd0.15Mn0.08Se and a nonmagnetic quantum well of Zn0.82Cd0.18Se. Efficient spin-conserving tunneling of an exciton as an entity was observed from the nonmagnetic quantum well to the magnetic well. The spin-reversing tunneling was suppressed by two orders of magnitude in high magnetic field. The spin-conserving tunneling time was determined as 20 ps by time resolved photoluminescence measurement.

Spin injection processes from a Zn0.80Mn0.20Se diluted magnetic semiconductor (DMS) to adjacent self-assembled CdSe quantum dots (QDs) were investigated by cw and time-resolved magneto-optical spectroscopy in combination with tunable laser excitation. Direct experimental evidence for the spin injection was provided from the generation of the spin polarization in the QDs, which was opposite to their expected intrinsic polarization, by resonantly generating the spins in the DMS. The observed limited spin polarization generated by the spin injection, together with the sensitivity of the spin injection efficiency on structure design, indicates severe spin loss during the process and calls for further investigations to optimize spin injection efficiency in quantum structures. © 2007 Elsevier Ltd. All rights reserved.

Magneto-optical spectroscopy in combination with tunable laser spectroscopy is employed to study the effect of sample design on optical spin-injection efficiency from a Zn(Cd)MnSe diluted magnetic semiconductor (DMS) into non-magnetic CdSe quantum dots (QDs). Two samples with inverted growth sequence of the DMS and QD layers were grown for this purpose. Despite observation of clear evidence for exciton/carrier-injection from the DMS to the QDs in both structures, their spin-injection efficiency is markedly different. The structure grown with the QD layer topmost exhibits rather efficient spin-injection, while the structure grown with the DMS layer topmost does not show any sign of spin-injection. Even in the former case, the spin-polarization of the injected excitons/carriers is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin-injection across the heterointerfaces.

We demonstrate the efficient transfer of spin-polarized excitons in diluted magnetic semiconductor (DMS) double quantum wells (QWs), where the spin-polarized excitons tunnel from the bottom of a non magnetic QW into a DMS-QW across a tunneling barrier and subsequently relax to the exciton ground state in the DMS-QW with phonon emissions. The exciton-transfer time decreases significantly when the exciton energy difference between both wells is equal to the energy of one longitudinal optical (LO) phonon. This observation indicates that the exciton spin transfer can be accelerated with the conservation of the spin polarization by the energy relaxation with the LO-phonon emission immediately after the tunneling.

We review our recent experimental findings by optical orientation spectroscopy that show efficient spin relaxation within semiconductor spin detectors to be an important factor limiting efficiency of spin injection in spin light-emitting structures based on ZnCdSe/ZnMnSe and InGaN/GaMnN. We provide evidence for the physical mechanism responsible for the observed efficient spin relaxation that accompanies momentum and energy relaxation of excitons/carriers. These findings call for increasing efforts in suppressing spin relaxation in spin detectors.

We report on the magneto-optical study of spin polarized energetic fine structures for exciton complex in single CdSe quantum dot (QD) by using micro- photoluminescence (micro-PL) spectroscopy. The zero-field splitting of exciton luminescence peak arisen from the anisotropic exchange interaction of carriers in the QDs was observed. The g-factors for exciton and negatively-charged exciton, i.e. trion in a single QD were determined by fitting the magnetic field dependence of the corresponding PL peaks. By exciting the single QD with circularly polarized light of σ- and σ+ polarization, the spin-up and spin-down trions were selectively generated. The ratio, τ/τsf, of the exciton lifetime and the time constants for the spin-flipping process of trion in a single QD was estimated to be 0.13, which implies a long spin-lifetime in single CdSe QD.

In this paper we review our recent results from in-depth investigations of physical mechanisms which govern efficiency of several processes important for future spintronic devises, such as spin alignment within diluted magnetic semiconductors (DMS), spin injection from DMS to non-magnetic spin detectors (SDs) and also spin depolarization within SD. Spin-injection structures based on II-VIs (e.g. ZnMnSe/Zn(Cd)Se) and III-Vs (e.g. GaMnN/Ga(In)N) were studied as model cases. Exciton spin relaxation within ZnMnSe DMS, important for spin alignment, was found to critically depend on Zeeman splitting of the exciton states and is largely facilitated by involvement of longitudinal optical (LO) phonons. Optical spin injection in ZnMnSe/Zn(Cd)Se was shown to be governed by (i) commonly believed tunneling of individual carriers or excitons and (ii) energy transfer via localized excitons and spatially separated localized electron-hole pairs (LEHP) located within DMS. Unexpectedly, the latter mechanism is in fact found to dominate spin injections. We shall also show that spin depolarization in the studied structures is essentially determined by efficient spin relaxation within non-magnetic spin detectors, which is an important factor limiting efficiency of spin detection. Detailed physical mechanisms leading to efficient spin depolarization will be discussed.

Spin injection is studied in self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor quantum well (DMS-QW) of Zn 1− x − y Cd x Mn y Se, by means of time-resolved circularly polarized photoluminescence (PL). Excitonic PL from the CdSe QDs shows σ − -circular polarization in magnetic fields, mainly due to negative g -values of individual dots, when the energy difference of excitons between the QDs and DMS-QW is large as 300 meV. However, when such energy difference is comparable with LO-phonon energy in the QD, we observe an additional PL peak with the long lifetime as 3.5 ns and σ + -polarization in magnetic fields. It can be attributed to a type-II transition between the down-spin electron injected from the DMS-QW into the QDs, via LO-phonon-assisted resonant tunneling, and the down-spin heavy hole in the DMS-QW. In addition, the electron spin-injection is also evidenced by σ + -polarized PL with the fast rise-time of 20 ps in the QDs.

Micro-photoluminescence (PL) has been studied in magnetic fields for single quantum nanostructures, such as, a quantum wire (QWR) and dot (QD) of Zn 1-x-y Cd x Mn y Se diluted magnetic semiconductor (DMS), where the DMS nanostructures were fabricated by means of electron-beam lithography. The giant Zeeman shift of excitons in the DMS-QWRs with the widths less than 50 nm appears larger than that in a quantum well (QW), which can be attributed to suppression of the exciton diffusion into deeper local sites with less Mn-content. In addition, the DMS-QDs have successfully been fabricated. We show spin injection from the DMS to non-magnetic dots in a coupled QD structure. The spin injection is clearly shown by PL with the circular polarization degree up to 20% from the non-magnetic dot, which is higher than that of 11% in the case of coupled QW. Effects of exciton diffusion are also discussed in the dot structures.

We study spin-dependent type-II band alignment and the carrier spin dynamics in a diluted magnetic double quantum well (DQW) composed of a magnetic well (MW) of Zn0.70Cd0.22Mn0.08Se and a Zn0.76Cd0.24Se non-magnetic well (NMW). In this DQW structure, a heavy-hole (hh) level in the MW intersects that in the NMW by applying a magnetic field of 1 T, resulting from the giant Zeeman effect of the hh in the MW. This hh-level crossing induces a type-II band alignment for the spin-polarized hh in the MW and an electron in the NMW. The circularly polarized photoluminescence (PL) energy decreases and the PL lifetime increases simultaneously with an increase in the magnetic field, which is quantitatively explained by the formation of spin-polarized indirect exciton. The magnetic-field dependence of the exciton PL shows the hh-spin dynamics in the transformation from the direct exciton state to indirect one. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We study the spin dynamics of photo-excited carriers in a diluted magnetic Cd0.95Mn0.05Te quantum well by means of pump-probe absorption spectroscopy. Transient differential absorption intensities, which are discriminated with left/right circular polarizations, indicate the spin-relaxation dynamics after pumping. Time constants of 0.5 and 7 ps are obtained for the heavy-hole (hh)- and electron-spin relaxations at 0 T, where the electron-spin relaxation is mainly caused by the s-d exchange mechanism involving Mn-spins. We observe a systematic increase in the electron-spin relaxation time up to 19 ps with an increase in the magnetic field up to 2.5 T. We attribute this to suppression of the electron-spin relaxation via the s-d exchange mechanism, where the spin transfer from the electron to the Mn-spin requires energy compensation due to the Zeeman splitting of the Mn-spin under magnetic fields. Above 3 T, the electron-spin relaxation time decreases with increasing magnetic field, possibly resulting from LO-phonon scattering involving acoustic phonons and Mn-spins. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We study the spin dynamics in self-assembled quantum dots (QDs) coupled with a diluted magnetic semiconductor (DMS) layer, where spin-polarized excitons can be injected from the DMS into QDs. Excitonic photoluminescence in the coupled QDs shows an increase in the degree of circular polarization P up to 0.3 at 5 T with increasing time after the excitation with a linearly polarized light pulse, indicating the spin injection dynamics from the DMS. The P-value turns to decay gradually after reaching its maximum, resulting from the spin relaxation in the QDs. We find that an inter-dot energy transfer affects the observed P-value. From a rate equation analysis, we deduce time constants responsible for the exciton-spin injection in the coupled QD system. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We study the emission from exciton states in a single CdSe/ZnSe quantum dot molecule (QDM) with different separation distances between the upper and the lower dot by applying micro-photoluminescence spectroscopy at low temperature. The observed splitting of the emission peaks demonstrates the coupling of quantum states that results in the bonding and antibonding configurations of exciton states in the QDM. As the separation distance decreases, the coupling strength increases gradually and brings forth the red-shift of the emission peaks. Furthermore, the coupling strength exhibits a lower dependence on the separation distance compared with a III–V QDM. By pumping the sample with circularly polarized photons, we investigate the fine splitting that arises from the asymmetric disk-like shape of the dots.

Dynamics of spin injection has been studied in double quantum wells (DQWs) composed of diluted magnetic and non-magnetic semiconductors. Picosecond-transient photoluminescence (PL) of excitons in t ...

Spin injection from diluted magnetic semiconductor (DMS) barriers of Cd 1− x Mn x Te into a quantum well (QW) of CdTe is studied, by means of pump–probe absorption spectroscopy in magnetic fields. Fast decay characteristics of circularly polarized differential absorbances of spin-polarized excitons in the DMS barrier show the exciton injection time of 6 ps from the barriers into the QW. In accordance with the fast relaxation of the spin-polarized excitons from the barrier, we observe the rise of circular polarization degree for the differential absorption of the CdTe QW in magnetic fields, evidently indicating the spin injection. In addition, the circular polarization degree up to 0.3 is developed in the well immediately after pumping, originating from the fast relaxation of a heavy hole (hh) spin less than 0.2 ps, due to the giant Zeeman effect caused by the penetration of the hh wave function into the DMS barriers.

In this work, we studied the magneto-optical properties of ZnMnTe/ZnMgTe spin superlattices by using photoluminescence (PL) spectroscopy at low temperature. The circularly polarized PL measurements in an increasing magnetic field were performed. Detailed characteristics of the level crossing behavior for the spin-polarized excitonic states due to the giant Zeeman splitting were observed. The results show that an increase of the magnetic field transfers the spin superlattices from direct band gap system to indirect band gap system, and spatially separates the electrons and the holes by changing type-I band alignment to type-II band alignment. These features are confirmed by the behavior of the PL intensity in magnetic field, and agree well with the theoretical expectation basing on the sp–d exchange interaction.

Dynamics of spin injection has been investigated in a double quantum well (DQW) composed of a diluted magnetic semiconductor by the pump–probe transient absorption spectroscopy in magnetic field. The DQW consists of a non-magnetic well (NMW) of CdTe and a magnetic well (MW) of Cd 0.92 Mn 0.08 Te. The MW shows a transient absorption saturation in the exciton band for more than 200 ps after the optical pumping, while the exciton photoluminescence does not arise from the MW. In the NMW, the circular polarization degree of the transient absorption saturation shows an increase with increasing time. The results are interpreted by the individual tunneling of spin-polarized electrons and holes from the MW to the NMW with different tunneling times. Depolarization processes of the carrier spins in the MW and the NMW are also discussed.

Electron-spin injection has been studied from a diluted magnetic semiconductor quantum well (DMS-QW) of Zn1–x–yCdxMnySe into self-assembled quantum dots (QDs) of CdSe through a tunneling barrier of ZnSe. The spin injection is experimentally evidenced by time-resolved circularly polarized photoluminescence (PL) in the QDs with the circular polarization degree up to 40%. The fast injection time of 20 ps can be attributed to the tunneling probability of the electron from the DMS-QW side. In addition to this, circularly polarized PL with the lifetime of 3.5 ns is simultaneously observed, indicating type-II transition between the electron in the QDs and the spin-polarized heavy hole in the DMS-QW. Those PL energies directly indicate that the electron tunneling is assisted by a LO phonon in the CdSe QD. The spin injection via LO-phonon-assisted resonant electron tunneling provides an efficient spin-injection process into the self-assembled QD exhibiting strong quantum confinement effects. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Hybrid nanostructures of a diluted magnetic semiconductor quantum well (DMS-QW) of Zn 1-x-y Cd x Mn y Se have been fabricated with a ferromagnetic Co/Pt-multilayered film, by electron beam lithography. The disk structure of the DMS-QW with the diameter of 100 nm was embedded in the magnetic thin film with the thickness of 50 nm. Giant Zeeman effects of excitons in the DMS-QW in the hybrid structure are studied by micro-photoluminescence (PL) spectroscopy. The Co/Pt film shows perpendicular magnetization without external field, and therefore it can generate magnetic fields nearly perpendicular to the DMS-QW plane in the hybrid structure. As the result, the circularly polarized excitonic PL arises in zero external field, indicating that the perpendicular magnetic field applied from the Co/Pt film aligns the exciton spins in the DMS-disk in the present hybrid structure.

Carrier-spin relaxation under a magnetic field has been studied in a diluted magnetic semiconductor quantum well (DMS-QW) of Cd0.95Mn0.05Te, by means of pump-probe absorption spectroscopy. With resonant excitation using a circularly polarized pump-pulse, dynamical spin-flip processes of an electron and heavy-hole (hh) are clearly observed in time dependences of the circularly polarized differential absorbance. In 0 T, time constants of 17 ps and 0.4 ps for the electron- and hh-spin relaxations in the Cd0.95Mn0.05Te QW are shorter than those of 46 ps and 1.0 ps in a non-magnetic CdTe QW, due to s-d exchange interactions between the carriers and Mn spins. The spin-flip time of the electron due to the exchange mechanism is determined as 27 ps. In an intense magnetic field of 5 T, the electron-spin relaxation due to the exchange mechanism is found to be strongly suppressed in the DMS-QW by magnetic-field-induced pinning of the Mn spins, exhibiting a longer time constant of 29 ps than that of 17 ps in 0 T. The role of LO-phonon is also discussed in the electron-spin relaxation under magnetic fields. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of shark cartilage proteoglycan (SCPG), which has heat-stable inhibitory activities against matrix metalloproteinase (MMP)-2 and -9 in vitro, on pancreatic carcinogenesis were studied in a rapid production model for pancreatic duct adenocarcinomas (PCs) in hamsters. Female Syrian golden hamsters received a diet containing 0% (group 1), 0.2% (group 2) or 0.4% (group 3) of SCPG for 50 days after initiation with N-nitrosobis(2-oxopropyl)amine followed by augmentation pressure. The number of PCs were 3.1 ± 2.0 in group 1 and 1.4 ± 0.9 in group 3, and total ductal lesions including hyperplasia, atypical hyperplasia and PCs were 9.7 ± 4.0 and 5.6 ± 2.7, respectively, the differences being significantly different (P < 0.05). These results were confirmed in a repeat experiment (P < 0.01). Gelatin zymography revealed that oral administration of SCPG did not affect the expression and activation of MMP-2 and MMP-9 in either serum or PC tissue. These results suggest that inhibition of pancreatic carcinogenesis by SCPG might involve a mechanism different from other synthetic-MMPs inhibitors.

Spin injection processes in the double quantum dots of ZnSe-based diluted magnetic semiconductors are discussed. Double quantum dots are fabricated from ZnSe-based double quantum wells by electron beam lithography and wet etching. In these samples, the photo-excited carriers in the magnetic dots are injected into the non-magnetic dots. The circular polarization degrees of photoluminescence from the non-magnetic dots are measured by micro-photoluminescence measurement system under the magnetic field up to 5 T. The maximum spin polarization degrees of injected carriers determined from our experiment are 10% for double quantum wells and 15% for double quantum dots. The spin injection efficiency was estimated both from the observed circular polarization degree and the diffusion length of carriers. We concluded that the spin injection efficiency is increased in the double quantum dots.

Giant Zeeman effects of excitons were studied in hybrid nanostructures of diluted magnetic semiconductor (DMS) quantum wells (QWs) with ferromagnetic Co, where the DMS-QW wires with the width of 200 nm were sandwiched in the Co wires with the width of 400 nm. When the direction of the Co magnetization is normal to the wire plane, a magnetic field B ⊥ Co‐flux perpendicular to the well plane can be applied from the Co wires to all of the DMS-QW wire. In addition, the use of a Co/Pt multilayered film with the perpendicular magnetization at zero external field was examined instead of the pure Co film. The excitonic photoluminescence spectrum from the DMS-QW shows significant broadening in the hybrid structures, indicating the giant Zeeman shift of excitons induced by B ⊥ Co‐flux.

Giant Zeeman effects and spin dynamics of excitons are studied in dense self-organized quantum dots (QDs) of CdSe and Cd1−xMn x Se. Microphotoluminescence (PL) measurements for each individual dot reveal the typical dot diameter of 3.5 ± 0.2 nm and the density of 5000 μm−2 in the CdSe QDs. The exciton lifetime is shorter in smaller dots with higher energies, indicating energy transfer and tunneling processes among the dots. Circular polarization of excitonic PL is observed at 0 T with an opposite sign to that of the excited light and with the rise time of 50 ps. The CdSe QDs coupled with a Zn1−xMn x Se layer show the giant Zeeman shift of exciton, arising from overlapping of exciton wavefunctions in the dots with Mn ions. Spin polarization dynamics in the coupled QDs is also studied.

Magnetic-field-induced switching of the spin configuration and the resultant spin injection direction have been studied in a Zn1−xMnxTe/ZnTe double quantum well. The up- and down-spin excitons are injected from the Zn1−xMnxTe layers to the ZnTe well in weak magnetic fields, where both exciton energies in the Zn1−xMnxTe layer are higher than those in the ZnTe. Above the level crossing field, the down-spin exciton energy in the Zn1−xMnxTe layers becomes lower due to the giant Zeeman effect. Therefore, the up- and down-spin excitons are spatially separated in each layer and the down-spin exciton in the ZnTe layer is injected to the Zn1−xMnxTe. It means that the direction of the excitonic spin injection can be switched by the external field. The injection time increases from 12 psec to 300 psec toward the level crossing field of 2.5 T, since the spin-polarized excitons in those layers are associated and can cause reverse spin injection processes. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Sub-micron scale hybrid structures of Zn 1-x-y Cd x Mn y Se diluted magnetic semiconductor (DMS) quantum wells (QWs) with ferromagnetic Co wires have been fabricated for the purpose of applying local magnetic fields to the DMS-QW. The wire of DMS-QW with the width down to 100 nm was sandwiched between the Co wires. The magneto-optical properties are studied by spin-flip light scattering of paramagnetic Mn-ions in the DMS. The application of uniform magnetic fields higher than 0.25 T has been attained from the Co wires to the DMS-QWs. In addition, the field application from the Co to the DMS-QWs is switched on by weak magnetic fields of 0.03 T due to the magnetic shape anisotropy of the Co wires, which can realize the switching behavior of the spin alignment of Mn-ions in the DMS-QW.