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We have investigated Co-Pd multilayers deposited on a Pd-SiN granular seed layer and a FeTaC soft magnetic underlayer (SUL) for perpendicular magnetic recording. The Pd-SiN granular seed layer of 3 nm was found to be very effective for good magnetic properties with coercivity of 3.9 kOe, a negative nucleation field of -2.1 kOe, and a M-H loop slope parameter 4/spl pi/ (dM/dH)/sub H=Hc/ of 1.3. The average column diameter of 13.7 nm with a dispersion of 21.7% was evaluated from the transmission electron microscopy image of well-separated columns with a clear boundary. This Co-Pd medium gave better playback performances by a merged ring giant magnetoresistive head compared to the medium with a Pd seed layer. The effect of Ar plasma etching on the SUL was also investigated to improve playback performance.

In this study, we investigate the application of advanced coding and signal processing techniques for a magneto-optical (MO) disk system in order to improve its recording capacity. In particular, we study the application of low-density parity check (LDPC) codes with iterative soft decoding to the center aperture detection magneto-optical (CAD-MO) recording channel. The channel pulse response is identified from the read-back signals using the least mean squares (LMS) algorithm. The minimum mean-squared error (MMSE) technique was used to design appropriate generalized partial response (GPR) targets. LDPC encoded data are written onto and digitized read back signals are collected from a spin stand. Off-line numerical evaluations show that LDPC code concatenated with a channel detector matched to the GPR target can increase the capacity.

Ultrafast 100 femtosecond laser light was irradiated on an amorphous GdFeCo film under a DC magnetic field. Complete magnetization reversal and rewritable response were observed in a less than 1 picosecond time period. This experiment reveals the intrinsic capability of ultrafast high-speed rewitable storage under the thermomagnetic switching scheme. Current pure magnetic recording such as that in the case of hard disk storage has a serious spin reversal time problem limited by the ferromagnetic resonance (FMR) frequency. Such frequency is ordinarily 1 to 3 GHz, which means that the recording speed limit is of a similar order. A one-picosecond response enables a very attractive future information storage scheme realizing 10 to 1000 Gbps ultrafast devices.

長野県木曽郡上松町健康増進センターにおいて成人歯科検診の平成11年検診時にCommunity Periodontal Index of Treatment Needs (CPITN) を用いた歯周疾患調査を行った。調査対象は木曽郡上松町在住の292名 (男性104名, 女性188名) であり, 平均年齢は男性61.1歳, 女性52.2歳であった。調査項目は, 現在歯数 (健全歯数, 未処置歯数, 処置歯数), 要補綴処置歯数, 対象歯のCPITN値, 部位別の各CPITN値を示す被験歯数, 口腔清掃度である。実態調査の結果は各歯数をStudent t testにて, CPITN値と口腔清掃度をx二乗検定にて統計学的分析を行った。その結果, 現在歯数, 健全歯数, 処置歯数は各年代群において男性群と女性群間に有意差を認めなかった。男性群, 女性群ともに現在歯数は39歳以下群と比較して60歳以上群では有意に減少していた。女性群においてCPITN各Code値は各年代群と有意な関連を認めたが, 男性群においては認めなかった。口腔清掃度は不良と判定された被験者が年代群の上昇に伴って増加していた。この結果から高齢化の進む上松町においては, 女性においては60歳代以降では硬組織疾患の治療が, 男性女性とも歯周疾患については口腔清掃指導を含めた歯周治療が必要であることが示された。

We investigated head-to-head domain walls in nanostrips of epitaxial $\mathrm{Fe}_4\mathrm{N}(001)$ thin films, displaying a fourfold magnetic anisotropy. Magnetic force microscopy and micromagnetic simulations show that the domain walls have specific properties, compared to soft magnetic materials. In particular, strips aligned along a hard axis of magnetization are wrapped by partial flux-closure concertina domains below a critical width, while progressively transforming to zigzag walls for wider strips. Transverse walls are favored upon initial application of a magnetic field transverse to the strip, while transformation to a vortex walls is favored upon motion under a longitudinal magnetic field. In all cases the magnetization texture of such fourfold anisotropy domain walls exhibits narrow micro-domain walls, which may give rise to peculiar spin-transfer features.

Dipeptidyl peptidase II (DPP II; EC 3.4.14.2) from rat kidney was purified to a specific activity of 65.4µmol/min per mg of protein for Lys-Ala-β-naphthylamide. The N-terminal and partial amino acid sequences of the enzyme were determined. The peptide sequences were used to identify expressed sequence tag (EST) clones. By using the cDNA fragment of one of the EST clones as a probe, we isolated a cDNA clone with 1710bp encoding DPP II from a rat kidney cDNA library. The cDNA of rat DPP II contained an open reading frame of 1500bp, coding for a protein of 500 amino acids. The first 10 residues of the purified enzyme matched the deduced protein sequence starting with residue 37, suggesting the presence of a signal peptide. The mature enzyme (464 residues) had a calculated molecular mass of 51400Da, which was lower than the value (about 60000Da) determined by SDS/PAGE; and the deduced amino acid sequence showed six potential N-glycosylation sites. The deduced amino acid sequence of rat DPP II shared high similarity with quiescent-cell proline dipeptidase (78% identity) and prolyl carboxypeptidase (38% identity) and bore the putative catalytic triad (Ser, Asp, His) conserved in serine peptidase families. We transiently transfected COS-7 cells with pcDNA3.1 containing the cloned cDNA and obtained the overexpression of an immunoreactive protein (of about 60000Da). The transfected cells showed Lys-Ala-methylcoumarinamide-hydrolysing activity that was 50 times higher than the control cells.

女性の生理的に起こりうる全身的変化として閉経がある。この生理的なホルモン分泌の減少期が歯周疾患の進行に与える影響を調査する目的で, 閉経前と閉経後の女性歯周疾患罹患患者を被験者として, 臨床パラメーターと歯槽骨吸収量とを比較した。被験者総数は233名 (閉経前群125名, 閉経後群108名) であり, 全身疾患および歯周治療の既往がなく, 咬合性外傷, 若年性歯周炎と診断されたものは除外した。女性歯周病患者各群は閉経前群と閉経後群に, 閉経後群は閉経1～5年群, 閉経6～10年群および閉経11年以上群に分類した。さらに男性歯周病患者106名を対象群とした。被験者は10年ごとの年齢層, 閉経後年数, 歯周疾患進行度により分類した。臨床パラメーターとして現在歯数, プラークコントロールレコード, プロービングによるポケット深さ, Gingival Index, 動揺度, Gingival Bleeding Indexを測定し, さらに歯槽骨吸収量をデンタルX線写真を用いて測定した。歯槽骨吸収量および臨床パラメーターは女性患者の閉経前後群および男性患者群とを比較した。その結果, 閉経前群と比較して閉経後群が歯槽骨吸収量は大きく, 前歯部に閉経後歯槽骨吸収量が大きかった。閉経後群の女性を同年齢層の男性患者群と比較すると, 閉経後問もない50歳代で歯槽骨吸収量が有意に大きくなったことから, 女性の歯周疾患患者における歯槽骨吸収量の増加には閉経というホルモン分泌の激減する全身的変化の影響が考えられた。

毛束反復回転式電動歯ブラシ (電動歯ブラシ) のプラーク除去効果および使用感について手用歯ブラシとの比較を行った。被験者は健康歯肉および軽度歯肉炎と診断された成人30名 (平均年齢26.8歳) とし2群 (A, B: 15名ずつ) に分けた。両群とも実験開始1週間前に電動歯ブラシの使用法およびバス法を指導し, 同時にプラークフリーとした。7日間の通常のブラッシング後, 実験期間1において, 被験者は6日間の手用歯ブラシあるいは電動歯ブラシによるブラッシングを行い, その後1日ブラッシングを停止させ, 7日目に同じ歯ブラシによる十分なブラッシングを行い, その前後のプラーク付着量を6歯について測定した。再びプラークブリーにし, 7日間の通常のブラッシング後, 実験期間IIにおいて, 被験者は実験期間1と別の歯ブラシを用いてブラッシングを行い, その後実験期間Iと同様にプラーク付着量を測定した。また実験期間終了後, 各被験者に対しブラッシングによる軟組織への損傷の診査および各歯ブラシの使用感に関するアンケートを実施した。その結果, 1) 電動歯ブラシは手用歯ブラシと比較して各群とも歯種, 歯面 (とくに隣接面で) 共有意にプラーク除去効果に優れていた。2) 両群間における各歯ブラシの使用順序によるプラーク除去効果に差を認めなかった。3) アンケートによる電動歯ブラシの使用感も良好であり, 軟組織の損傷は実験期間中認めなかった。これらの結果から本電動歯ブラシのプラーク除去効果が示された。

An activated Nd:YAG fiber tip using fiber-tip enhanced device (FTED) makes an activated and scattered irradiation beam. The enhanced (activated) fiber tip could be irradiated parallel to the target surface. The purpose of this study was to determine the effect of the activated laser fiber tip for calculus removal compared with other techniques. Specimens of extracted teeth with or without calculus were prepared. Nd:YAG laser power pulse 1 (SLT Japan, Tokyo, Japan) was used. The diameter of the optimal fiber was 400 μm. The enhanced condition was firstly examined using irradiation power from 100 to 900 mJ, 1 to 10 pps, in order to verify which is the best condition for calculus removal with scattering irradiation beam. Four types of calculus removal methods were compared: (1) hand curette; (2) ultrasonic scaler; (3) laser irradiation through a normal optimal fiber tip at 900 mJ, 10 pps, using a perpendicular irradiation mode with water coolant; (4) laser irradiation through the active fiber tip at 900 mJ, 10 pps, using a parallel irradiation mode with water coolant. After the roughness of the surfaces was clinically measured, the specimens were then prepared for scanning electron microscopy (SEM) observation. These results indicated that the best enhanced condition of the FTED for calculus removal with scattering irradiation beam was 800 mJ, 10 pps. The FTED was more useful for calculus removal than the normal fiber tip. However, it was less effective than hand and ultrasonic scaling considering the treatment time.

For almost all optical disks, signal decline is mainly due to inter symbol interference (ISI) caused by laser beam spot size or magnetic aperture size. Such 151 does not appear for Zero Field Magnetic Amplifying Magneto-optical System (Zero Field MAMMOS). The limit of the frequency response comes from the frequency range of the MO readout channel. MAMMOS has a resolution for 1/10 of a laser beam corresponding to 0.1μm. Decrease in the carrier level and error of less than 0.1μm is caused by expansion failure. If expansion failure were circumvented, Zero Field MAMMOS would have a possibility of readout with 0.04μm resolution using a laser with wavelength, 650nm and an objective lens of NA, 0.6.

Recent experiments indicate room-temperature ferromagnetism in graphite-like materials. This paper offers multiple spin state analysis applied to asymmetric graphene molecule to find out mechanism of ferromagnetic nature. First principle density functional theory is applied to calculate spin density, energy and atom position depending on each spin state. Molecules with dihydrogenated zigzag edges like C64H27, C56H24, C64H25, C56H22 and C64H23 show that in every molecule the highest spin state is the most stable one with over 3000 K energy difference with next spin state. This result suggests a stability of room temperature ferromagnetism in these molecules. In contrast, nitrogen substituted molecules like C59N5H22, C52N4H20, C61N3H22, C54N2H20 and C63N1H22 show opposite result that the lowest spin state is the most stable. Magnetic stability of graphene molecule can be explained by three key issues, that is, edge specified localized spin density, parallel spins exchange interaction inside of a molecule and atom position optimization depending on spin state. Those results will be applied to design a carbon-base ferro-magnet, an ultra high density 100 tera bit /inch2 class information storage and spintronic devices., 6 pages, 8 figures

N-Propargyl-2,4-bis(trifluoroacetyl)-1-naphthylamine (3) underwent nitrogen-containing heterocyclic ring-formation reactions with a variety of active methylene compounds in the presence of sodium alkoxides. This annulation reactions with dialkyl malonates were highly dependent on reaction temperature to give selectively the corresponding fluorine-containing benzo[h]quinolines (5) at high temperature and 1H-benzo[h]quinolin-2-ones (7 and 8) at low temperature. Furthermore, changing the electron-withdrawing groups of active methylene compounds led to alternation of the reactive site wherein the reagents attack first and to the formation of the different nitrogen-containing heterocyclic systems, pyridine (9), dihydropyridine (11 and 13) and pyridone (12).

辺縁性歯周炎に対する塩化リゾチーム270mg/日×4週間 (L群) の臨床的有用性をプラセボ (P群) を対照とする二重盲検試験で検討した。311例 (L群159例, P群152例) を対象に, プロービング時の出血, 歯肉の炎症, 歯の動揺, ポケットの深さ, ポケット内滲出液量, 滲出液中PGE2量, 縁下プラーク細菌について検討し, 全般的改善度, 概括安全度, 有用度の評価を行った。全例に薬剤投与開始前にスケーリングを, 投与期間中ブラッシングを実施した。出血, 炎症, 歯の動揺, ポケットの深さおよび滲出液中PGE2量の改善度についてはL, P両群間に差をみなかったが, ポケット内滲出液量はL群でのみ有意に減少するのを認めた。また, 縁下プラークの細菌数はL群で有意に減少, P群で有意に増加し, 両群の変化量に有意の差を認めるとともに全細菌のうち, 運動性桿菌の占める比率はL群でのみ有意に低下するのを認めた。全般改善度 (4週後) および有用度については, L群がP群に優るのを認めた。なお, 副作用はL群に13件, P群に19件発現したが, 両群の概括安全度には差をみなかった。これらの成績から, スケーリングならびにブラッシングと併用するとき, 塩化リゾチームは辺縁性歯周炎の治療に有用な薬剤であると考えられる。

β,β-Bis(trifluoroacetyl)vinyl ether (1) reacted with 1,2-phenylenediamine to give dihydrobenzodiazepinol (4a) selectively, whereas β-trifluoroacetylvinyl ether (2) and β-trifluoroacetyl-a-phenylvinyl ether (3) gave the corresponding O-N exchange products (6b, c) when reacted with 1,2-phenylenediamine. The factors determining the reaction products of the reaction of three substrates 1-3 having similar structures with 1,2-phenylenediamine were elucidated on the basis of molecular orbital calculations. The dehydration processes from dihydrobenzodiazepinols (4 and 8) to benzodiazepines (5 and 7) are also discussed.

Periodontitis, which is a widespread and major dental disease, is a multifactorial, lifestyle-related disease and has been analyzed for gene polymorphism. We examined the frequency of the polymorphisms of the pro-inflammatory cytokine genes IL-1 A (-889) and IL-1 B (+3953) in relation to periodontitis in the Japanese population. We also examined whether polymorphism of TLR2 (Arg677Trp) and TLR4 (Asp299Gly), which are receptors recognized by periodontopathic bacteria, may also be associated with periodontitis. The subjects were 92 Japanese individuals, among whom 43 had periodontitis and 49 were healthy controls. We isolated genomic DNA from lingual mucosal cells and tested them for single nucleotide polymorphisms by polymerase chain reaction-restriction fragment length polymorphism. The incidence of polymorphisms was analyzed statistically by Fisher's exact test, and the sensitivity and specificity of the gene polymorphisms were calculated. The purpose was to determine whether such polymorphisms might be effectively used in the diagnosis of periodontitis. However, we found no evidence that the gene polymorphism of IL-1A (p = 0.082), IL-1 B (p = 0.180), TLR2 (p = 1.000) or TLR4 (p = 1.000) and overall gene polymorphism in any of the genes (p = 0.752) correlate with periodontitis. The sensitivity (14.0%) and specificity (83.7%) of the mutations found in all of the genes were low. Therefore, we advise against using the analyses of polymorphism of these genes to detect periodontitis in the Japanese population.

2,3-Dimethylthiazolium iodides (1) reacted easily with trifluoroacetic anhydride in the presence of pyridine to give 2-bis(trifluoroacetyl)methylene-2,3-dihydro-3-methylthiazoles (2) in excellent yields. Deacylation of 2 proceeded readily in moderate to high yields by acid catalyst such as silica gel and aqueous hydrochloric acid to afford the corresponding 2-trifluoroacetylmethylene-2,3-dihydro-3-methylthiazoles (3), which were smoothly reconverted into diacylated compounds (2) with trifluoroacetic anhydride. The highly poralized structure of 2 was also briefly discussed.

The purpose of this study was to investigate the effects of different methods of brushing on plaque removal, using O'Leary's plaque Control Record during initial preparation. The results were as follows: 1. There were many 40-50 year-old patients and they showed a 63.0 percent first visit Plaque Control Record average. 2. Many of the patients entering the clinic had periodontal disease in mild stages. 3. In most cases the toothbrushing methods were the Rolling method and the Modified Stillman's method. Of the patients, 73.5% achieved Plaque Control scores at the 20 percent level. 4. Of the patients who had achieved a Plaque Control Record at the 20 percent level, half of the patients instructed to brush using the Rolling method had developed moderate forms of periodontal diseases, and half of the patients instructed to use the Modified Stillman's method had developed mild forms of periodontal disease. There is a close relationship between toothbrushing methods and the progression of diseases, and this shows that Plaque removal methods should be controlled.

歯肉の形態に影響を及ぼす因子としての主要な臨床所見の症状に着目し, それぞれの所見との関連性を検索した。その結果, 様々な歯肉形態め出現率に, 臨床所見の症状である歯周ポケット, 歯槽骨の吸収, プラーク, 歯石, 不良修復物等が影響し, 歯周疾患と歯肉形態には密接な関係があることが示唆された。各検査項目間の相関性の検討においてもcleft form以外で有為な相関性が認められた。これらの関連性を把握することは, 治療計画, 治療方法, 予後の推測等において重要な役割を果たすものと考えられる。

本研究の目的は歯周病患者の臨床症状として, 欠かすことの出来ないX線写真による骨吸収に重点をおいて診査し, 同部位のポケットの状態, 炎症の程度, 歯の動揺度との関係と特徴をとらえるために統計的に検討した。その結果, (1) 上下顎中切歯部において骨吸収が多く見られるが, ポケットの深さは平均2.6mm前後であった。 (2) 上下顎第一大臼歯部では骨吸収量は中切歯部に比べ少ないが, ポケットは平均約3.0mmであった。 (3) 骨吸収量の増加に伴い, 動揺度の値も大きくなる傾向が見られた。 (4) 骨吸収量の大きい中切歯部において歯肉炎症指数 (GI) も高い結果であった。 (5) 骨吸収パターンは約8割が水平型で遠心側に, 約2割が垂直型で近心側に多く見られた。

To investigate whether genomic DNA can be purified in sufficient quantity and quality from the oral cavity.One milliliter of peripheral blood and saliva were collected. The buccal and lingual mucosal cells were also obtained using 10 strokes with a swab or a toothbrush, respectively. All materials were centrifuged and the cells were lysed by adding sodium dodecyl-sulfate and proteinase K. The DNAs were extracted with phenol and precipitated with ethanol followed by electrophoresing on 0.8% agarose gel. The purified DNAs were digested with restriction enzyme Dpn I and Mbo I, respectively. Amplification of the IL-1A gene by PCR was carried out using the purified DNAs and electrophoresing on polyacrylamide gel.DNA was obtained from lingual mucosal cells collected with a toothbrush. Only about one-thirtieth of the recovered DNA was of non-human origin (bacterial contaminants from the oral cavity). Judging from the PCR amplifications of the IL-1A gene, the DNA extracted from lingual cells was of sufficient quality, in all respects indistinguishable from the DNAs extracted from the other specimen, such as peripheral blood, saliva and buccal mucosal cells collected with a swab, and in sufficient quantity. Our results indicate that it is possible to purify DNAs from lingual mucosal cells collected with a toothbrush in a simple and safe manner. Compared to DNA samples from patients by blood extraction, the described method also had the advantage of being painless and not inducing mental distress.

SVOD (Stacked Volumetric Optical Disk) can realize 0.94-5TB capacity cartridge using 100 ultra thin disks and commercialized drive. This paper presents the mechanism of aerodynamic stabilizer and several types of thin discs.

We grow a 15-nm-thick ferromagnetic Fe4N epitaxial film on a SrTiO3(001) substrate by molecular beam epitaxy, and process it into approximately 0.5-µm-wide and 24-µm-long L-shaped ferromagnetic narrow wires by electron-beam lithography and Cl2 reactive ion etching. Their longitudinal directions are set in parallel to the magnetic easy axes, Fe4N[100] and [010]. With applying external magnetic field in the direction parallel to Fe4N[100] or [010], the position of domain wall is controlled either on the upper side or lower side of the corner. This experiment is the preliminary step toward current-driven domain wall motion in Fe4N having a negative spin polarization.

The magnetization and spin transport of asymmetric zigzag-edge graphene nanoribbons, terminated by hydrogen on one edge while unterminated on the other edge, were investigated by a combination of first-principles calculations and a tight-binding approach. At the unterminated edge, a spin-polarized σ edge state of minority spin appears near the Fermi level and contributes to spin transport. This state enters the band gap for ribbon widths of less than 15 chains, dominating the spin-polarized current. This indicates the importance of the σ edge states in the design of spintronic devices using graphene nanoribbons. We also examined the case where the ‘unterminated’ edge is partially terminated by hydrogen.

First-principles calculations on stoichiometric ${\mathrm{Mo}}_{n}{\mathrm{S}}_{2n}$ and ${\mathrm{W}}_{n}{\mathrm{S}}_{2n}\phantom{\rule{0.3em}{0ex}}(n=1\text{--}8)$ clusters show that their lowest energy atomic structures are dominated by a central core of metal atoms while the S atoms cap this core. We discuss in detail terminal, edge, and face capping of tetrahedral and octahedral Mo clusters by sulfur atoms for off-stoichiometric compositions also. Capping on the terminal sites is found to be least favorable. Edge capped ${\mathrm{Mo}}_{4}{\mathrm{S}}_{6}$ and face capped ${\mathrm{Mo}}_{6}{\mathrm{S}}_{8}$ clusters have high symmetries and high stability among all the clusters we have studied. We find that magnetic isomers are lowest in energy for some clusters though bulk $M{\mathrm{S}}_{2}$ ($M=\mathrm{Mo}$ and W) is nonmagnetic. Our results on ${\mathrm{Mo}}_{6}{\mathrm{S}}_{8+p}\phantom{\rule{0.3em}{0ex}}(p=0\text{--}6)$ clusters further show that ${\mathrm{Mo}}_{6}{\mathrm{S}}_{12}$ is magic with $4{\ensuremath{\mu}}_{B}$ magnetic moment. The origin of magnetism and bonding nature in these clusters is discussed. Our finding could lead to the possibility of magnetic clusters of a variety of nonmagnetic transition-metal compounds and their interesting assemblies.

The correlation between periodontal disease and osteoporosis was evaluated by comparing age, panoramic radiographic and clinical parameters of periodontal disease. Diagnosis of osteoporosis in periodontal diseased patients was evaluated by panoramic radiographic parameters (mandibular cortical width:MCW). Subjects which had more than 20 teeth and examined by panoramic radiography were untreated adults with periodontal disease who were free of other systemic disease. The following parameters were examined on panoramic X-ray film:alveolar bone loss (ABL), mandibular bone mass with the use of mandibular cortical width (MCW). ABL was significantly higher and MCW significantly lower in the postmenopausal group (6 years after menopause). The number of teeth was significantly lower and CAL significantly higher in the postmenopausal group (11 years after menopause). Age and ABL correlated positively in men and women. Years after menopause and ABL and MCW and CAL in the postmenopausal group were correlated positively. Women whose MCW was less than mean - 2 SD should be diagnosed with osteoporosis. Our results demonstrated that periodontal disease correlates with osteoporosis, and MCW could be useful in detecting of osteoporosis in women with periodontal disease.

Magnetic recording will face very serious problems beyond Tera bit/in/sup 2/, such as: recorded bit thermal stability in a size range of less than 20 nm×30 nm; very strong magnetic field necessary to write on a high coercive media, estimated over 15 kOe; write frequency limited to a few GHz, depending on the natural resonance of the magnetic material. In a hybrid recording scheme, writing is done at a high temperature around 150-230 °C, while archiving at room temperature. Such a simple concept brings solutions to solve the above difficulties. This paper outlines various hybrid recording device configurations and checks out the applicability of several materials for this type of application.

Recently, M. Sekine et al. (Techn. Digest ODS, pp 61, 2001) showed the first experimental results on a new MAMMOS magneto optical super resolution media type, which they call zero-field MAMMOS, that in contrast to the earlier developed AC MAMMOS type can be read-out without the need for any external modulating expansion field. These media were designed for use in a system with a DVD-like optical light path, employing a 650 nm laser and an NA of 0.6. Philips and Hitachi Maxell have, in joint effort, made and tested the first zero field MAMMOS media for use in a first-surface MO (magneto optical) recorder using a blue-violet laser with a wavelength of 405 nm and an NA of 0.7. In this paper we present the first recording results on these media, recorded with an actuated recording head that operates at 15 /spl mu/m from the storage layer of the disc. This distance is an order of magnitude smaller than the free working distance of the Blu-Ray Disc system.

Summary form only given. Hybrid recording has already been realized in laser beam assisted perpendicular magnetic recording in audio recordable MiniDiscs. In the year 2000 alone, more than 20 million drives and 220 million disks were shipped. Hybrid recording is expected to be a very strong candidate in the near future in the very high density region, exceeding terabits/in/sup 2/. Here, we report on hybrid recording with the capability to overcome two of the main serious problems; the paramagnetic limit in high density region and the writing speed limit caused by ferromagnetic resonance around 2 to 5 GHz.

Magnetic amplifying magneto-optical system (MAMMOS) technique has gained recent attention because of its potential to achieve high recording density. Timing recovery module plays a very important role in the performance of MAMMOS sampled-data detectors because it controls the time instants at which the continuous playback signal is sampled. In this paper, we report a new timing recovery algorithm for MAMMOS and investigate its performance through spin stand data.

Hybrid recording is a novel scheme combining optical recording and magnetic recording (H. Saga et al, J. Magn. Soc. Jpn, vol. 23, suppl. S1, p. 225, 1999). In this paper, basic experiments satisfying the principles of both very high density and ultra high speed writing are shown. We discuss the future capability of the storage device toward Tbit/in/sup 2/ and 100 Gbps directly coupled to an optical fiber communication network.

To obtain an areal density of 100 Gbit/in/sup 2/, magneto-optical (MO) technologies are attractive from the perspectives of magnetic field modulation recording, magnetic domain expansion readout, and high read/write cyclability. In this paper, we discuss the micro magnetic mechanism and compare the domain expansion MO schemes.

Advantages of Hybrid recording and material candidates like CoCrPt,TbFeCo.Pd/Co and FePt are discussed targeting the recording density beyond Tera bit/in2.