INVESTIGATION INTO THE MATERIALS AND MANUFACTURING OF A NEW THIN FILM MAGNETORESISTIVE SENSOR

There is increasing interest in utilising very thin anisotropic magnetoresistive films (typically in the range of a few nano-metres) to make magnetic sensors which can be made very small and with a high signal-to-noise ratio. In this thesis, a new type of sensor is investigated which has a pair of thin film MR stripes whose magnetisation is switched alternately in opposite directions using bias fields from currents in overlay conductor films. The investigation considers in particular the Barkhausen noise in these sensors and its relationship with factors such as sensor film thickness. The effect of thickness and grain size on the coercivity of Ni81Fe19 permalloy thin films deposited by r.f. sputtering with negative substrata bias is systematically investigated as a function of under-layer materials, thickness, and substrata temperature. The results show that there is a minimum in coercivity at a thickness of about 7.5 nm with a grain size of 4 nm. This may be attributed to the grain size via its relationship with magnetic domain wall thickness. A tantalum under-layer favours a (111) (low anisotropy) surface plane in permalloy sensor films. Elevated deposition temperature may reduce defects in the films. A comparison of the magnetic domain wall structure and the state of magnetisation in the very thin (5 - 30 nm) permalloy films with and without Ta underlayer is made by using Lorentz TEM observation. The result shows that it is different in both cases. With Ta underlayer, the wider, straighter and more regular domain walls together with less rippling in magnetisation in adjacent domains may lead to a reduction in the Barkhausen noise. Barkhausen noise studies of films are carried out by sweeping an ac field of 77 Hz onto the permalloy films and recording the induced output voltage due to the flux change as a function of time on a digital storage oscilloscope. Barkhausen noise and corresponding hysteresis of the sensor is studied by analysis of the MR response of various sensors together with their magnetoresistive hysteresis, which may be reduced or improved by using a suitable external high frequency field (5 kHz to 20 kHz). Variation in the sensitivity of the sensor to the magnitude of a switched-biasing field was measured by applying a very small alternating field (from about tens to a few hundreds of nano-Tesla) at frequency above about 250 Hz and varying a transverse de field component (δH.), The effect of biasing field frequency and external linearising field on the sensitivities of these MR sensors is studied using an in-house built measurement system. Highly sensitive magnetoresistive sensors (120 different types have been available within 30 substrates) have been designed and then fabricated by photolithography in a temperature and humidity controlled clean room. Sensor thicknesses are typically in the range from 5 nm to 40 nm and other dimensions typically (10 µm - 80 µm wide) and 6.4 mm long. The sensor is linear in the range from zero to 14 400 nT. It produces an almost noise-free output of 20 to 30 millivolts for a field change of about 160 nano-Tesla

Preparation of the Branch Bark Ethanol Extract in Mulberry Morus alba

The biological activities of the branch bark ethanol extract (BBEE) in the mulberry Morus alba L. were investigated. The determination of active component showed that the flavonoids, phenols, and saccharides are the major components of the ethanol extract. The BBEE had a good scavenging activity of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical with around 100 μg/mL of IC50 value. In vitro assay revealed that the BBEE strongly inhibited both α-glucosidase and sucrase activities whose IC50 values were 8.0 and 0.24 μg/mL, respectively. The kinetic analysis showed that the BBEE as a kind of α-glucosidase inhibitor characterized a competitive inhibition activity. Furthermore, the carbohydrate tolerance of the normal mice was obviously enhanced at 0.5 h (P<0.05) and 1.0 h (P<0.05) after the BBEE intragastric administration as compared to negative control. At 0.5, 1.0, 1.5, and 2.0 h after the intragastric administration with starch, the postprandial hyperglycemia of the type 2 diabetic mice can be significantly decreased (P<0.01) by supplying various concentrations of the BBEE (10–40 mg/kg body weight). Therefore, the BBEE could effectively inhibit the postprandial hyperglycemia as a novel α-glucosidase activity inhibitor for the diabetic therapy

Scaling of Anisotropic Flows and Nuclear Equation of State in Intermediate Energy Heavy Ion Collisions

Elliptic flow ($v_2$) and hexadecupole flow ($v_4$) of light clusters have been studied in details for 25 MeV/nucleon $^{86}$Kr + $^{124}$Sn at large impact parameters by Quantum Molecular Dynamics model with different potential parameters. Four parameter sets which include soft or hard equation of state (EOS) with/without symmetry energy term are used. Both number-of-nucleon ($A$) scaling of the elliptic flow versus transverse momentum ($p_t$) and the scaling of $v_4/A^{2}$ versus $(p_t/A)^2$ have been demonstrated for the light clusters in all above calculation conditions. It was also found that the ratio of $v_4/{v_2}^2$ keeps a constant of 1/2 which is independent of $p_t$ for all the light fragments. By comparisons among different combinations of EOS and symmetry potential term, the results show that the above scaling behaviors are solid which do not depend the details of potential, while the strength of flows is sensitive to EOS and symmetry potential term.Comment: 5 pages, 5 figure

Deletion or insertion in the first immunoglobulin-plexin-transcription (IPT) domain differentially regulates expression and tumorigenic activities of RON receptor Tyrosine Kinase

<p>Abstract</p> <p>Background</p> <p>Activation of the RON receptor tyrosine kinase, a member of the c-MET family, regulates tumorigenic phenotypes. The RON extracellular domains are critical in regulating these activities. The objective of this study was to determine the role of the first IPT domain in regulating RON-mediated tumorigenic activities and the underlying mechanisms.</p> <p>Results</p> <p>Two RON variants, RON160 and RON^E5/6inwith deletion and insertion in the first IPT domain, respectively, were molecularly cloned. RON160 was a splicing variant generated by deletion of 109 amino acids encoded by exons 5 and 6. In contrast, RON^E5/6inwas derived from a transcript with an insertion of 20 amino acids between exons 5 and 6. Both RON160 and RON^E5/6inwere proteolytically matured into two-chain receptor and expressed on the cell surface. RON160 was constitutively active with tyrosine phosphorylation. However, activation of RON^E5/6inrequired ligand stimulation. Deletion resulted in the resistance of RON160 to proteolytic digestion by cell associated trypsin-like enzymes. RON160 also resisted anti-RON antibody-induced receptor internalization. These features contributed to sustained intracellular signaling cascades. On the other hand, RON^E5/6inwas highly susceptible to protease digestion, which led to formation of a truncated variant known as RONp110. RON^E5/6inalso underwent rapid internalization upon anti-RON antibody treatment, which led to signaling attenuation. Although ligand-induced activation of RON^E5/6inpartially caused epithelial to mesenchymal transition (EMT), it was RON160 that showed cell-transforming activities in cell focus formation and anchorage-independent growth. RON160-mediated EMT is also associated with increased motile/invasive activity.</p> <p>Conclusions</p> <p>Alterations in the first IPT domain in extracellular region differentially regulate RON mediated tumorigenic activities. Deletion of the first IPT results in formation of oncogenic variant RON160. Enhanced degradation and internalization with attenuated signaling cascades could be the mechanisms underlying non-tumorigenic features of RON^E5/6in.</p

Dynamic GATA4 enhancers shape the chromatin landscape central to heart development and disease.

How stage-specific enhancer dynamics modulate gene expression patterns essential for organ development, homeostasis and disease is not well understood. Here, we addressed this question by mapping chromatin occupancy of GATA4--a master cardiac transcription factor--in heart development and disease. We find that GATA4 binds and participates in establishing active chromatin regions by stimulating H3K27ac deposition, which facilitates GATA4-driven gene expression. GATA4 chromatin occupancy changes markedly between fetal and adult heart, with a limited binding sites overlap. Cardiac stress restored GATA4 occupancy to a subset of fetal sites, but many stress-associated GATA4 binding sites localized to loci not occupied by GATA4 during normal heart development. Collectively, our data show that dynamic, context-specific transcription factors occupancy underlies stage-specific events in development, homeostasis and disease

Room-temperature ammonia sensor based on ZnO nanorods deposited on ST-cut quartz surface acoustic wave devices

Using a seed layer-free hydrothermal method, ZnO nanorods (NRs) were deposited on ST-cut quartz surface acoustic wave (SAW) devices of ammonia sensing at room-temperature. For a comparison, a ZnO film layer of 30 nm thick was also coated onto ST-cut quartz SAW device using a sol–gel and spin-coating technique. The ammonia sensing results showed that the sensitivity, repeatability and stability of the ZnO NRs coated SAW device were superior to those of the ZnO film coated SAW device due to the large surface-to-volume ratio of the ZnO NRs