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  • 1
    Electronic Resource
    Electronic Resource
    Thermomagnetic analysis of NdFeB melt-spun alloys with low Nd content (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4133-4135 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase transformation of NdFeB melt-spun alloys with low Nd content of 4–8 at. % was investigated by thermomagnetic analysis and x-ray diffractometry. Experimental results have shown that the metastable Nd2Fe23B3 compound formed in the alloys is considered to be transformed to Nd2Fe23B3+α-Fe+Fe3B in the temperature range of 550–690 °C, α-Fe+Fe3B+Nd1+eFe4B4 in the temperature range of 690–730 °C and finally α-Fe+Nd1+eFe4B4 above 840 °C. From the results, it has been concluded that Nd2Fe14B is not formed from metastable Nd2Fe23B3. On the other hand, the melt-spun alloy of Nd2Fe23B3 (∼Nd7.1Fe82.1B10.7) annealed under optimum conditions has been found to be composed of α-Fe, Fe3B, and Nd2Fe14B phases. The alloy has a coercivity comparable to Fe3B-based Nd4Fe77B19 and relatively high-energy product of about 71.6 kJ/m3 (∼9 MG Oe). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359501
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  • 2
    Electronic Resource
    Electronic Resource
    Temperature dependence of magnetoimpedance effect in amorphous Co66Fe4NiB14Si15 ribbon : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6575-6577 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the magnetoimpedance (MI) effect is important both for scientific study and for thermal stability of MI sensors. We have performed the measurement of MI effect in amorphous Co66 Fe4 NiB14 Si15 (Metglas 2714A) ribbon from a cryogenic chamber where the temperature of the sample can vary from 10 to 300 K. The ac current was fixed at 10 mA for all measured frequencies ranging from 100 kHz to 10 MHz. The magnetoimpedance ratio (MIR) was revealed the drastic increment as a function of MIR(T)=MIR(0)exp(cT2), where c is a constant. The measured MIR values at room temperature are usually 2–3 times larger than the data measured at 10 K for all measured frequencies. However, the shapes of the MIR curves are remained. This result shows the potential application of the MI effect for a temperature sensor. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367605
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  • 3
    Electronic Resource
    Electronic Resource
    A mathematical model for pH patterns in the rhizospheres of growth zones (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the classical model by Nye (1981), the main process for the change in pH across the rhizosphere is assumed to be diffusion. The classical model focuses on the non-growing part of the root and assumes that the distribution of ion fluxes along the root is spatially uniform. We consider the rhizosphere of the growth zone and take into account the root growth rate and spatially varying flux along the root surface. We present both analytical (dimensional analysis) and experimental (computational) evidence of the importance of taking into account the root growth rate. We describe a conceptual and mathematical model to analyse the pH field around the root tip over time. The model is used with published data to show that, for typical growth rates in sandy soil, the pH field becomes steady (independent of time) after 6 h. Dimensional analysis reveals that a version of the Péclet number, related to the quotient of root elongation rate and proton diffusivity, can be used to predict the extent of the rhizosphere and the time required for it to become steady. For Péclet numbers much greater than 1 (soils), the root influences soil pH for distances on the millimetre scale. In contrast, for Péclet numbers much less than one (agar, aqueous solution), the root influences substrate pH for radial distances on the scale of centimetres. We also present some evidence that agar-contact techniques to measure the soil pH may not be appropriate for measuring the millimetre-scale gradients in soil pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00512.x
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  • 4
    Electronic Resource
    Electronic Resource
    T2-weighted MR imaging for hepatic hemangiomas: comparison of breath-hold and non-breath-hold turbo spin-echo pulse sequences with phased-array multicoil (1998)
    Springer
    Abdominal imaging 23 (1998), S. 422-426 
    Details
    ISSN: 1432-0509
    Keywords: Key words: Angioma, gastrointestinal tract—Liver, MR—Liver neoplasms, MR—Magnetic resonance (MR), comparative studies—Magnetic resonance (MR), technique.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Background: We compared T2-weighted and heavily T2-weighted breath-hold turbo spin-echo (TSE) sequences with T2-weighted non-breath-hold TSE sequence to evaluate hepatic hemangiomas on magnetic resonance (MR) with a phased-array multicoil. Methods: Twenty-two patients with 27 hemangiomas were studied at 1.0-T scanner by using T2-weighted and heavily T2-weighted breath-hold TSE sequences (18 s each) and non-breath-hold T2-weighted TSE sequences with use of a phased-array multicoil. Images were quantitatively analyzed for tumor-to-liver signal-difference-to-noise ratios (SD/Ns) and tumor-to-liver signal intensity ratios (T/Ls) and qualitatively analyzed for tumor conspicuity and motion-induced image artifacts. Results: Quantitatively, T2-weighted breath-hold TSE images showed the highest SD/Ns among the three sequences, although the differences from the heavily T2-weighted breath-hold TSE sequence and the T2-weighted non-breath-hold TSE sequence were not statistically significant (p= 0.61 and 0.06, respectively). Heavily T2-weighted breath-hold TSE images showed the highest T/Ls among the three sequences. The differences from the T2-weighted breath-hold TSE sequence and the T2-weighted non-breath-hold TSE sequence were statistically significant (p 〈 0.001). Qualitatively, breath-hold TSE images were superior to non-breath-hold TSE images in terms of tumor conspicuity (p 〈 0.01) and motion artifacts (p 〈 0.01). Conclusion: T2-weighted breath-hold TSE sequence is superior to T2-weighted non-breath-hold TSE sequence in the evaluation of hepatic hemangiomas on MR with a phased-array multicoil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002619900372
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  • 5
    Electronic Resource
    Electronic Resource
    Hepatic Hemangioma: Contrast-Enhancement Pattern during the Arterial and Portal Venous Phases of Spiral CT (1999)
    Springer
    Abdominal imaging 24 (1999), S. 262-266 
    Details
    ISSN: 1432-0509
    Keywords: Key words: Liver, CT—Liver, neoplasm—Hemangioma.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The objective of the present study was to evaluate contrast-enhancement patterns of hepatic hemangioma according to size during hepatic arterial (30-s delay) and portal venous (65-s delay) phases of spiral computed tomography (CT). During a 10-month-period, 73 patients with 118 hemangiomas underwent two-phase spiral CT examination. The enhancement patterns of tumors were divided into four types based on the attenuation of surrounding liver parenchyma: peripherally nodular high, uniform high, iso, and low. The diameter of the tumors were 〈10 mm (n= 39), 11–20 mm (n= 33), and 〉21 mm (n= 46). Overall, the most common enhancement patterns of hemangioma were peripherally nodular high (66/118, 55.9%) during the arterial and portal venous phases. The second most common contrast-enhancement patterns of hemangioma were uniform high (15/118, 12.7%) during the arterial and portal venous phases. In tumors smaller than 20 mm, 11 (9.3%) had low-low attenuation and two (1.7%) had iso-low attenuation during the arterial and portal venous phases, respectively. In conclusion, at two-phase spiral CT, the most common contrast-enhancement patterns of hemangioma are peripherally nodular high and/or uniform high during the arterial and portal venous phases. However, hemangiomas smaller than 2 cm may have atypical enhancing patterns including low and iso-attenuation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002619900492
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  • 6
    Electronic Resource
    Electronic Resource
    MR cholangiopancreatography: comparison between half-Fourier acquisition single-shot turbo spin-echo and two-dimensional turbo spin-echo pulse sequences (1998)
    Springer
    Abdominal imaging 23 (1998), S. 398-403 
    Details
    ISSN: 1432-0509
    Keywords: Key words: Bile ducts, MR—Magnetic resonance (MR), comparative studies—Magnetic resonance (MR), half-Fourier imaging.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Background: To compare half-Fourier acquisition single-shot turbo spin-echo (HASTE) magnetic resonance cholangiopancreatography (MRCP) with two-dimensional turbo spin-echo (2D TSE) MRCP for imaging pancreatobiliary diseases. Methods: Twenty-seven patients with biliary or pancreatic disease underwent MRCP on a 1.0-T scanner with a body phased-array coil. A T2-weighted HASTE sequence (18 s) and a T2-weighted 2D TSE sequence (45 s) were used during a breath-hold by the patient. The source images and maximum intensity projection images of both sequences were reviewed independently by two radiologists. Results: Motion artifacts were more severely pronounced with 2D TSE sequences than with HASTE sequences (p 〈 0.001). All obstructions and their sites were accurately identified with both sequences. Filling defects (calculi) in bile ducts were identified in all 22 segments (100%) with HASTE-MRCP, whereas calculi in 19 of 22 segments (86%) were identified with 2D TSE-MRCP (p= 0.25). Three missed sites on 2D TSE-MRCP were intrahepatic bile ducts. Conclusions: HASTE-MRCP is superior to 2D TSE-MRCP in terms of detecting motion artifacts and visualization of the pancreatic ducts. HASTE-MRCP is comparable to 2D TSE-MRCP for visualization of the biliary ducts and their obstruction and is superior to 2D TSE-MRCP for identification of calculi in intrahepatic bile ducts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002619900368
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  • 7
    Electronic Resource
    Electronic Resource
    Dysplastic nodules of the liver: imaging findings (1999)
    Springer
    Abdominal imaging 24 (1999), S. 250-257 
    Details
    ISSN: 1432-0509
    Keywords: Key words: Liver—Neoplasms—US—CT—MR.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: To verify characteristic features of hepatic dysplastic nodules at different imaging modalities. Methods: Twenty-eight patients with 37 dysplastic nodules of the liver (0.8–3.0 cm) underwent sonography (28 patients), computed tomography (CT; 24 patients), magnetic resonance (MR; 11 patients), and angiography (12 patients). Each nodule was analyzed for echogenicity, attenuation, signal intensity, and vascularity. Results: Echogenicity of nodules was high in 16 (43%), homogeneous in two (6%), and low in 19 (51%) of 37 nodules. Attenuation of nodules was high in one (7%), homogeneous in four (26%), and low in 10 (67%) of 15 nodules on the arterial-phase CT images; homogeneous in five (33%) and low in 10 (67%) of 15 nodules on the portal-phase CT images; and high in four (17%), homogeneous in six (26%), and low in 13 (57%) of 23 nodules on the delayed-phase CT images. Signal intensity of nodules was high in 15 (94%) and homogeneous in one (6%) of 16 nodules on T1-weighted MR images and was homogeneous in seven (44%) and low in nine (56%) of 16 nodules on T2-weighted MR images. Vascularity of nodules was avascular in 14 (88%) and slightly vascular in two (12%) of 16 nodules. Conclusions: Hepatic dysplastic nodules show diverse imaging characteristics with different imaging techniques; however, common imaging findings of hepatic dysplastic nodules are low echo, low attenuation, and high, low, or homogeneous intensity on T1- and T2-weighted MR, and avascularity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002619900490
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  • 8
    Electronic Resource
    Electronic Resource
    Visualization of high-speed gas jets and their airblast sprays of cross-injected liquid (1999)
    Springer
    Experiments in fluids 27 (1999), S. 102-106 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  A planar and instantaneous visualization study of high-speed gas jets and their airblast sprays was performed to qualitatively examine the different atomization performances of different gas nozzles. For the visualization of high-speed gas jets (with no liquid injected), Nd:YAG pulsed laser sheets imaged the clustered vapor molecules in the Rayleigh range (d≪λ), condensed from the natural humidity during the isentropic gas expansion through a nozzle. This method visualized both underexpanded sonic gas jets from a converging nozzle (SN-Type) and overexpanded supersonic gas jets from a converging-diverging nozzle (CD-Type). When liquid is cross-injected, the same laser sheet images the spray droplets of relatively large sizes (d?λ). The present visualization results show that the SN-Type nozzle develops a wider spray than the CD-Type nozzle, quite probably because the SN-Type nozzle has a wider gas jet (in the absence of liquid) than the CD-Type. Also, the wider spray of the SN-Type nozzle lowers the probability of droplet coalescence and generates finer sprays compared to the CD-Type nozzle. These visualization results qualitatively agree with the previous quantitative finding of the different atomization characteristics of the two types of nozzles (Park et al. 1996).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050334
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  • 9
    Electronic Resource
    Electronic Resource
    Re-evaluation of optimal dose of contrast medium for vascular enhancement in CT of the head and neck (1997)
    Springer
    Neuroradiology 39 (1997), S. 30-34 
    Details
    ISSN: 1432-1920
    Keywords: Key words Computed tomography ; head and neck ; Contrast medium ; dose ; Comparative study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Adequate contrast enhancement of major neck vessels is more important than that of a tumour itself in CT of most head and neck tumours because of differentiation from neck node metastases. Our purpose was to re-evaluate the dosage of contrast medium for adequate vascular enhancement in CT of the head and neck. In a blind prospective fashion, 60 patients with a variety of head and neck lesions were randomised into three equal groups receiving 0.75, 1.0, or 1.25 ml/kg of meglumine ioglycate, 300 mg/ml. Contrast medium was administered by injector at 2 ml/s. The scan time and interscan delay were each 1 s, and total scan time 50–180 s. The scan was started immediately after administration of two-thirds of the contrast medium. The degree of vascular enhancement was assessed visually and quantitatively. We visually scored the degree of vascular enhancement as excellent (4 points), good (3), fair (2) or poor (1). For quantitative study, after measuring the CT numbers of the common or internal carotid artery (CA), internal jugular vein (IJV) and adjacent muscle at three levels, were calculated mean vessel/muscle contrast ratios. The degree of enhancement of the CA and IJV tended to increase with dose of the contrast media, but no examination was rated as showing poor enhancement in any group. The mean visual assessment scores for 0.75, 1.0, and 1.25 ml/kg were 2.7, 2.9 and 3.1, respectively; the mean ICA/muscle contrast ratios were 1.58, 1.55 and 1.63, and those of IJV/muscle 1.65, 1.59 and 1.59. There was no significant difference between visual and quantitative assessment in any group. The results suggest that 0.75 ml/kg of contrast medium appears sufficient for vascular opacification for head and neck lesions when the CT scan can be completed in about 120 s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050362
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