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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 8017-8021 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Amounts of spontaneous spin splittings were estimated from low-temperature magnetoresistances in two-dimensional electron gases created at In0.75Ga0.25As/In0.75Al0.25As heterojunctions under a gate bias. Typical sheet electron densities and mobilities in the raw wafers were ∼1.0×1012/cm2 and 2–5×105 cm2/V s at 1.5 K, respectively. A maximum spin-orbit coupling constant αzero of ∼30(×10−12 eV m) was obtained for the van der Pauw sample. In gated Hall-bar samples, a decrease in the αzero value with decreasing gate voltage (Vg) was first confirmed in a normal heterojunction. The main origin for such a large αzero, which is a few times larger than any previously reported, was found to be a structure-dependent so-called interface contribution in the Rashba term. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 573-575 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A compact electron cyclotron resonance ion source has been developed for heavy-ion medical facilities. The beam intensity and stability were considerably improved by recent modifications on three points (length of sextupole, cooling system for the extraction electrode, and position of the Einzel lens). Initial results of C4+ beam tests show that an intensity of 180 eμA can be routinely obtained with simple tuning. The best record was 220 eμA for C4+, which meets the medical requirements. Throughout these tests, CH4 gas was used with 0.1 cc/min and the extraction voltage was fixed at 25 kV. Results on beam emittance and long-term stability are also briefly discussed. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 720-722 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We recently reported on the first observation of ion-pumping phenomenon in a low-duty pulsed Penning source at the heavy-ion medical accelerator (HIMAC) in Chiba and its effectiveness to produce multiply charged ions [Y. Sato et al., Nucl. Instrum Methods Phys. Res. A 450, 231 (2000)]. In the Penning-ionized gauge ion source (PIGIS) of the HIMAC, the gas flow is not being pulsed, but there is a transient pressure response in the source when the arc is pulsed that permits the production of high-charge-state ions under a reasonably low gas pressure obtained by ion pumping. The best record for Ar8+ is 700 eμA in a peak under a constant gas flow of 0.2 cc/min, an extraction voltage of 24 kV, and a pulsed arc power of 1 kV and 5 A with a duty factor of 0.5% (25 W on average). This yield is higher than those of cw PIGISs by a factor of 100–1000 having a similar design and power (peak). This article gives a brief review for the mechanism and effects of ion pumping in a pulsed PIGIS. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 984-986 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Carbon–ion cancer treatment is successfully being made at the Heavy Ion Medical Accelerator in Chiba (HIMAC). Design philosophy for the ion sources for medical facilities are as follows: (1) sufficient beam intensity, a few hundred e μA; (2) long lifetime with good stability; (3) easy operation and easy maintenance; and (4) compactness. In order to develop such source for future heavy-ion facilities, we have tested compact electron cyclotron resonance (ECR) ion sources using permanent magnets both for axial and radial confinement of hot electrons. Since the yield of C2+ ion in the first developed source (2.45 GHz ECR) was 15 e μA and far below the medical requirement (∼150 e μA for the HIMAC), a new source has been proposed, having a frequency of 10 GHz. The extracted intensity of C4+ (and C2+) ions is expected to be higher than 200 e μA. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 461-464 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We have performed the fs pump–probe experiment on the B˜→a˜ nonadiabatic transition in the Hg–CO vdW complex. It is found that the transition occurs near the point where Hg and CO come nearest to each other on the B˜-state surface with a probability of 0.07 for their single encounter. This experiment serves as the first observation of the wave packet dynamics associated with an intermolecular energy flow in the vdW interaction. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 30 (2003), S. 0 
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: summary  At the oral stage of swallowing, the tongue plays a major role and proper tongue performance is necessary to form the bolus and transfer it to the pharynx. For the present study we built a prototype device for safe and handy objective estimation of tongue motion and coordination with laryngeal elevation at swallowing. The device records tongue pressure by means of two strain gauge pressure transducers aligned 20 mm apart on a brass strap placed along the palatal midline. Laryngeal vibration is recorded with piezo-electric acceleration transducers. Time differences between pressure onset at the anterior and posterior transducers and the first spike from laryngeal vibration are measured. Ten healthy subjects were asked five times to swallow 5 mL of water. Pressure onset at the anterior transducer preceded posterior pressure by 294 ± 164 ms. Given the distance between the transducers, the tongue contracted (squeezed) at a speed of 93 ± 60 mm s−1. Laryngeal vibration occurred 671 ± 175 ms after the onset of anterior pressure. There was considerable variation in these parameters between subjects. Though the data is limited, the device successfully and easily revealed certain aspects of tongue motion and coordination with laryngeal elevation.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 27 (2000), S. 0 
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: An I-bar clasp is a popular retainer for distal-extension removable partial dentures. However, there have been almost no evidence-based criteria on the mechanically preferable shape. The present study aimed to investigate the variations of dimension in I-bar clasps used in patients, and to clarify the effect of the variations on stiffness and stress of I-bar clasps by finite element analysis. Dimensions (thickness, width, taper, radius of curvature, length, relation to oral structures) of 23 I-bar clasps were measured. A three-dimensional finite element model was made for each measured I-bar clasp with vertical and horizontal straight sections connected with a curved section. A concentrated load of 5 N was applied at the lowest point of the tip that contacted the abutment in the buccal direction. Maximal equivalent stress and stiffness of each clasp were evaluated. The measured dimension, stiffness, and maximum stress showed wide variations. Mean stiffness was far from the proper one, and mean stress was near the proportional limit of Co–Cr alloy. Considering the stiffness and stresses in this study, only six clasps out of 23 were appropriate. These results suggest that evidence-based criteria of preferable shape of I-bar clasps should be determined.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 27 (2000), S. 0 
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: To gather knowledge related to establishing criteria for selecting soft denture liners for individual patients, the effects of certain properties of soft denture liners on stress distribution were evaluated by two-dimensional finite element analysis. A partial mandibular edentulous ridge crest was modelled. Six combinations of thickness (mucosa: 1 or 2 mm; soft denture liner: 1, 2, or 3 mm) and 18 combinations of Young's modulus (mucosa: three kinds; soft denture liner: six kinds) were analysed. The ratio of maximum to minimum stress in the mucosa (stress ratio) was calculated to estimate stress concentration. In the case of thin mucosa (1 mm thickness), the lower the Young's modulus of the soft denture liner, the lower the stress ratio. However, if the soft denture liner had a lower Young's modulus than the mucosa, stress concentrated adversely. These results suggest that the elasticity of the soft denture liner should match the elasticity of the mucosa to obtain the optimum cushioning effect.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 27 (2000), S. 0 
    ISSN: 1365-2842
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Double implants have been thought to have biomechanical advantages for single molar replacement. To evaluate the effectiveness of double implants versus a wide implant, the vertical forces and torque on each implant were calculated by three-dimensional geometric analysis. Buccal load (100 N) perpendicular to cuspal inclination (20°) was applied at the occlusal surface of the superstructure. The three kinds of load points (A, B, C) were 1·5, 3·5, and 5·5 mm from the mesial contact point, respectively. Three implants were compared: mesial and distal double implants (∅ 3·3 mm), and a wide implant (∅ 5 mm). The wide implant showed torque around the long axis (1·8–15·0 N · cm) whereas double implants had no torque. On the other hand, the vertical forces on the mesial double implant were both smaller (60%: loaded at point C) and larger (140%: loaded at point A) than the wide implant. Given the smaller surface area of the mesial double implant, this large force may generate much higher stress in the peri-implant bone. These results suggest that the biomechanical advantage of double implants for single molar replacement is questionable when the occlusal force is loaded at the occlusal surface near the contact point.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1365-2559
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Epstein–Barr virus (EBV) and its associated proteins may be protective against the occurrence of apoptosis that would normally inhibit cancer development and progression. Alternatively, the viral infection may cause altered or mutated expression of oncogenes or tumour suppressor genes that are necessary for tumour development, an action that may also involve apoptosis. In this study, a relationship was sought between occurrence of EBV infection, expression of apoptosis-associated proteins (tumour suppressor gene p53 and oncogenes c-myc and bcl-2) and levels of cell death (apoptosis or necrosis) in 119 cases of gastric carcinoma.〈section xml:id="abs1-2"〉〈title type="main"〉Methods and results:The EBV status of the gastric carcinomas (using the EBV-encoded small RNA I (EBER-1) and in-situ hybridization), stage and grade of tumour and sex of patients were compared for bcl-2, p53 and c-myc expression patterns. EBER-1 was detected in approximately 20% of cases studied. There was no significant correlation between levels of cell death in the tumour tissue and EBV status. In the protein analyses, development and progression of gastric carcinoma, with or without EBV infection, was independent of bcl-2 expression. However, in gastric cancers with EBV infection, p53 overexpression was inhibited and c-myc expression was increased in early stage cancers, in comparison with decreased c-myc expression in late stage cancers.〈section xml:id="abs1-3"〉〈title type="main"〉Conclusions:The p53 and c-myc expression patterns indicate that EBV-infected gastric carcinomas are less likely to have a natural regression via apoptosis at an early stage and explain, in part, the resistance to treatment of late stage of gastric cancers.
    Materialart: Digitale Medien
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