Search

We investigated difference in the transport properties between Al 0.1 In 0.9 Sb/InSb and Al 0.1 In 0.9 Sb/InAs 0.1 Sb 0.9 quantum wells (QWs). The resistivity of InSb QWs increases exponentially with decreasing temperature, while that of InAs 0.1 Sb 0.9 QWs is much lower than that of InSb QWs, showing low resistivity even at low temperature. Energy band diagram calculations of InAs x Sb 1− x /Al 0.1 In 0.9 Sb quantum wells (QWs) revealed that the bottom of the conduction band of the InAs x Sb 1− x well moves downward with increasing As content x . The bottom of the InSb QWs lies above the Fermi level ( E F ), resulting in depletion of the QW, while that in InAs 0.1 Sb 0.9 QWs lies under E F at low temperature. These calculation results support the experimental difference of the resistivity and sheet carrier density between two types of the QWs well. [ABSTRACT FROM AUTHOR]

The temperature dependence of the transport properties of undoped and Sn-doped InSb single crystal thin films grown on GaAs substrates by MBE were investigated. The temperature dependence of undoped InSb thin films was large and had maximum near room temperature, whereas the Sn-doped thin films showed very small and monotonic decrease with increasing temperature. The electron mobility of the films varied significantly in the growth direction from the InSb/GaAs hetero-interface to the InSb thin film surface. This large variation of the electron mobility in the growth direction explained the observed temperature dependence of the electron mobility for these films. The large variation of the electron mobility in the growth direction was described by a simple model of two layers with a low electron mobility layer near the hetero-interface and the other with a high electron mobility. These InSb films were used to fabricate practical and highly sensitive Hall sensors with a very small temperature dependence. [Copyright &y& Elsevier]

GaAs/AlGaAs two-dimensional electron gas (GaAs-2DEG) Hall probes are impractical for sub-micron room-temperature scanning Hall microscopy (RT-SHPM), due to surface depletion effects that limit the Hall driving current and magnetic sensitivity (Bmin). Nano and micro Hall-effect sensors were fabricated using Bi and InSb thin films and shown to be practical alternatives to GaAs-2DEG probes for high resolution RT-SHPM. The GaAs-2DEG and InSb probes were fabricated using photolithography and the Bi probes by optical and focused ion beam lithography. Surface depletion effects limited the minimum feature size of GaAs-2DEG probes to ∼1.5 μm2 with a maximum drive current Imax of ∼3 μA and Bmin∼0.2 G/√ of Hz. The Bmin of 1.5 μm2 InSb Hall probes was 6 × 10-3 G/√ of Hz at Imax of 100 μA. Further, 200 nm × 200 nm Bi probes yielded good RT-SHPM images of garnet films, with Imax and sensitivity of 40 μA and ∼0.80 G/√ of Hz, respectively. [Copyright &y& Elsevier]

Further diversification of Hall sensor technology requires development of materials with high electron mobility and an ultrathin conducting layer very close to the material’s surface. Here, we describe the magnetoresistive properties of micro-Hall devices fabricated using InAlSb/InAsSb/InAlSb heterostructures where electrical conduction was confined to a 30 nm-InAsSb two-dimensional electron gas layer. The 300 K electron mobility and sheet carrier concentration were 36 500 cm2 V-1 s-1 and 2.5×1011 cm-2, respectively. The maximum current-related sensitivity was 2 750 V A-1 T-1, which was about an order of magnitude greater than AlGaAs/InGaAs pseudomorphic heterostructures devices. Photolithography was used to fabricate 1 μm×1 μm Hall probes, which were installed into a scanning Hall probe microscope and used to image the surface of a hard disk. [ABSTRACT FROM AUTHOR]

Objective Pro-brain natriuretic peptide (proBNP)-108 and N-terminal proBNP-76 (NT-BNP) contain seven sites for O-linked oligosaccharide attachment. Currently, levels of glycosylated NT-BNP are probably underestimated because it is not recognised by one antibody in the sandwich assay system. The pathophysiological significance of cardiac and plasma levels of non-glycosylated (nonglyNT-BNP) and glycosylated NT-BNP (glyNT-BNP) in heart failure (HF) and chronic renal failure (CRF) was investigated. Methods Plasma samples from 186 patients with HF and 76 patients with CRF on haemodialysis were studied, together with 11 atrial tissue samples. To measure nonglyNT-BNP and glyNT-BNP, samples were incubated with or without deglycosylating enzymes and NT-BNP was measured using Roche Elecsys proBNP I. The percentage glyNT-BNP was calculated as glyNT-BNP/(glyNT-BNP + nonglyNT-BNP). Results In HF, plasma BNP, nonglyNT-BNP and glyNT-BNP levels all increased with increasing disease severity (New York Heart Association class; p<0.0001), though the molar ratio remained constant (molar ratio, BNP:nonglyNT-BNP:glyNT-BNP = 1:2.4:9.6). Before haemodialysis for CRF, plasma BNP and nonglyNT-BNP were somewhat elevated, and glyNT-BNP was markedly increased (molar ratio, BNP:nonglyNT-BNP:glyNT-BNP = 1:8.5:82). After haemodialysis, plasma BNP, nonglyNT-BNP, atrial natriuretic protein and cGMP all declined (p<0.0001), but glyNT-BNP was unchanged. Notably, the percentage of glyNT-BNP was elevated before haemodialysis, and was further increased after haemodialysis (p<0.0001). Atrial tissue levels of BNP, nonglyNT-BNP and glyNT-BNP were similar. Conclusion The findings suggest that most endogenous plasma NT-BNP is glycosylated and therefore undetectable with the current assay system, and that the relative glycosylation level is increased by haemodialysis. [ABSTRACT FROM AUTHOR]

Objective Recent studies have shown that plasma levels of brain natriuretic peptide (BNP)-32 and proBNP-108 are increased in heart failure (HF) and that the BNP-32 assay kit in current clinical use cross-reacts with proBNP-108. We investigated why proBNP is increased without processing in HF was investigated. Design, setting and patients Plasma BNP-32 and proBNP-108 in normal individuals (n=10) and in patients with atrial fibrillation (AF) (n=18) and HF (n=132) was measured. BNP-32 and proBNP-108 in ventricular and atrial tissue and in pericardial fluid using a specific fluorescent enzyme immunoassay following Sep-Pak C18 (Waters, Milford, Massachusetts, USA) cartridge extraction and gel filtration was also measured. Main outcome measures Levels of both BNP-32 and proBNP-108 were higher in HF than in control or AF (both p<0.01), and the levels of these peptides significantly correlated (r=0.94, p<0.001). The proBNP-108/total BNP (BNP-32+proBNP-108) ratio was widely distributed and lower in HF (0.33 (0.17)) than in control (0.41 (0.06), p<0.05) and AF (0.45 (0.04), p<0.002). The proBNP-108/total BNP ratio was higher in HF with ventricular than in HF with atrial overload (0.45 (0.10) vs 0.20 (0.11), p<0.001). Consistent with this finding, the major molecular form were proBNP-108 and BNP-32 in ventricular (n=6, 0.67 (0.04)) and atrial (n=7, 0.76 (0.05), p<0.0001) tissues, respectively. ProBNP-108 was also the major molecular form of BNP in pericardial fluid (n=8, 0.82 (0.05)). The proBNP-108/total BNP ratio increased and decreased with HF deterioration and improvement, respectively. Conclusion These results suggest that BNP-32 and proBNP-108 is increased in HF and that the proBNP/total BNP ratio increases in association with pathophysiological conditions such as ventricular overload. [ABSTRACT FROM AUTHOR]

Objective Recent studies have shown that plasma levels of brain natriuretic peptide (BNP)-32 and proBNP-108 are increased in heart failure (HF) and that the BNP-32 assay kit in current clinical use cross-reacts with proBNP-108. We investigated why proBNP is increased without processing in HF was investigated. Design, setting and patients Plasma BNP-32 and proBNP-108 in normal individuals (n=10) and in patients with atrial fibrillation (AF) (n=18) and HF (n=132) was measured. BNP-32 and proBNP-108 in ventricular and atrial tissue and in pericardial fluid using a specific fluorescent enzyme immunoassay following Sep-Pak C18 (Waters, Milford, Massachusetts, USA) cartridge extraction and gel filtration was also measured. Main outcome measures Levels of both BNP-32 and proBNP-108 were higher in HF than in control or AF (both p<0.01), and the levels of these peptides significantly correlated (r=0.94, p<0.001). The proBNP-108/total BNP (BNP-32+proBNP-108) ratio was widely distributed and lower in HF (0.33 (0.17)) than in control (0.41 (0.06), p<0.05) and AF (0.45 (0.04), p<0.002). The proBNP-108/total BNP ratio was higher in HF with ventricular than in HF with atrial overload (0.45 (0.10) vs 0.20 (0.11), p<0.001). Consistent with this finding, the major molecular form were proBNP-108 and BNP-32 in ventricular (n=6, 0.67 (0.04)) and atrial (n=7, 0.76 (0.05), p<0.0001) tissues, respectively. ProBNP-108 was also the major molecular form of BNP in pericardial fluid (n=8, 0.82 (0.05)). The proBNP-108/total BNP ratio increased and decreased with HF deterioration and improvement, respectively. Conclusion These results suggest that BNP-32 and proBNP-108 is increased in HF and that the proBNP/total BNP ratio increases in association with pathophysiological conditions such as ventricular overload. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the spin–orbit interaction (SOI) in Al0.1In0.9Sb/Sn-doped InAs0.1Sb0.9 quantum wells (QWs) with different doping levels using the weak anti-localization effect in the magneto-resistance. The inelastic scattering time is close to the T −1 law predicted theoretically for electron–electron interaction, and the spin–orbit scattering time is temperature independent as expected for the D''yakonov–Perel mechanism. The carrier-density dependence of zero-field spin-splitting energy extracted from the fits of magneto-resistance was examined by the theoretical calculation. The result confirms that the Dresselhaus SOI is much larger than the Rashba SOI in our QWs. The dominance of the Dresselhaus term in SOI originates in the large weight factor of InSb-based alloy. [Copyright &y& Elsevier]

Abstract: We have investigated the spin–orbit interaction in strain-free Al0.1In0.9Sb/InAs0.1Sb0.9 quantum wells with different widths. The weak anti-localization (WAL) effect was clearly observed in the magneto-resistance for all samples. The inelastic scattering time is close to the T −1 law predicted theoretically for electron–electron interaction in the diffusive regime, and the spin–orbit scattering time is temperature independent as expected for the D’yakonov–Perel mechanism. The zero-field spin-splitting energies extracted from these observations were around 1.0meV. The WAL behavior becomes distinct in samples with wider well width, and the zero-field spin-splitting energy slightly increases with well width. This seems to reflect increase of the carrier concentration. [Copyright &y& Elsevier]

Abstract: Transport properties were investigated for undoped Al0.1In0.9Sb/ InAs0.1Sb0.9 quantum wells (QWs), and two-carrier analyses were applied to the magnetic-field variations of the Hall coefficient and magnetoresistance at 77K. The Hall coefficient increases with magnetic field, which shows coexistence of electrons and holes. This behaviour is similar to AlGaAsSb/ InAs QWs, which have a type-II band structure. Additionally, the Hall coefficient turns to decrease in more than 1T, and the behaviour was not observed in the deep InAs QWs. This indicated that there are other electrons with different mobility. These are thought to be electrons extended over the QW, accumulated near the hetero-interface, and thermally excited in the barrier layer. [Copyright &y& Elsevier]

We have investigated magneto-resistance in InAs/Al0.6Ga0.4As0.1Sb0.9 quantum well (QW), where the lattice mismatch at the interface is less than 2 %. The carrier concentration can be tuned by using positive and negative persistent photoconductivity effect, selected by the wavelength (λ=1.6μm or 0.95 μm) of illumination. The electrons and holes coexist in the QW structure, and the contribution of both carriers should be taken into account. The observed deviation of Hall plateaus from the quantized value can be understood by considering the carrier transport in both electron and hole edge channels, and the equilibrium of chemical potential at the all electrodes in the sample. The transport properties in quantum Hall regime measured in the samples with the QW thickness of 15, 50 and 150 nm are reported. [ABSTRACT FROM AUTHOR]

Abstract: Low-temperature magneto-transport properties of Al x Ga1− x As y Sb1− y /InAs deep quantum wells (QWs) with different well widths (L w=15–500nm) and their dimensionality were studied. The Hall data were analyzed by means of the two-carrier model: coexistence of electrons and holes for L w=15–150nm and existence of two types of electrons with different mobility for L w=300 and 500nm. The profile of perpendicular magnetoresistance (MR), ρxx (B ⊥) for the two-dimensional electrons (2DEs) in narrow QWs (L w=15 and 50nm) can be divided into the following four regimes: (1) the negative MR due to the weak localization (WL) in extremely low B-fields, (2) the crossing of ρxx for different temperatures at B c=1/μ e in moderate B-fields due to the orbital effect on the electron–electron interaction, (3) the Shubnikov–de Haas oscillations and (4) the quantum Hall effect in high-B fields. As for the in-plane MR except in the very low-field region characterized by the WL, Δρxx (B ∥)/ρ 0 always starts from a negative one essentially independent of T, which was explained by the classical boundary scattering at the wall of the barrier in quasi-ballistic regime. The quantum Hall resistance of the electron–hole system has also been discussed. [Copyright &y& Elsevier]

Abstract: Both negative and positive persistent photoconductivity (NPPC and PPPC) effects on the low-temperature transport properties were studied in the Al x Ga1− x As y Sb1− y /InAs quantum wells with a well width of L w=15 and 50nm. The irradiation of light with λ<1.0μm causes the NPPC, while the light with λ=1.6μm causes the PPPC. The Hall coefficient R H(B) in the dark or after illumination considerably increases with increasing B, indicating the coexistence of majority electrons and minority holes and allowing to analyze it by means of the two-carrier model. The PPPC effect leads to an increase in both density (n and p) and mobility of electrons and holes, while the NPPC inversely leads to their decrease, which was confirmed by the PPC effects on the SdH oscillations and the Hall resistance in the regime of quantum Hall effect in high magnetic fields. We have found the experimental relation, pμn3, so that the minority holes increases (decreases) much more rapidly than the majority electrons increases (decreases) in the PPPC (NPPC). [Copyright &y& Elsevier]

Abstract: Weak-field magnetoresistance (MR) in the variable-range hopping (VRH) in the presence of spin–orbit interaction (SOI) for 2DEGs at the hetero-interface of InSb quantum wells was examined in view of the quantum interference (QI) effect. Samples with the sheet resistance, ρ>ρ c=h/e 2, exhibit VRH, while those with ρ<ρ c exhibit weak localization (WL) at low temperatures, where h/e 2 is the quantum resistance. In the WL regime, a positive magnetoresistance (MR) peak due to the weak anti-localization (WAL) with SOI is clearly observed in low magnetic field. In contrast, the low-field hopping MR remains entirely negative surviving the SOI, indicating that the hopping MR due to the QI is completely negative regardless of the SOI. This result supports the predictions based on the directed-path approach for forward-scattering paths ignoring the back-scattering return loops for the QI in the VRH. [Copyright &y& Elsevier]

Presents a study that developed thin film micro-Hall sensor for room temperature scanning Hall probe microscopy. Measurements of the Hall probe noise; Comparison of the performance of the developed micro-Hall sensor with gallium arsenide-based sensors; Features of the micro-Hall sensor.

The article presents a case study of 33-year-old whose Platelet concentrates (PCs) was collected using PLT apheresis system and inspected visually. Topics include observation of chain aggregates in microscopic field, appearance of platelet (PLT) clumps on third day, presence of transmembrane glycoprotein CD62P as a measure of activated PLTs, absence of abnormal blood test in the donor, relationship between red blood cells (RBC) morphology and PLT clumps and elimination of acanthocytes.