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Microarray studies conducted to determine the accumulation of organic acids in the fruit of 60Co-y-irradiated melon (Cucumis melo var. amen) resulted in the detection of 475 differentially expressed genes. Among these, 251 were up-regulated and 224 were down-regulated. This finding included an additional 62 upand 33 down-regulated unknown ("no hit") genes. Among the genes identified, 47 showed significant False Discovery Rates (FDR) of < 0.01 and substantial (⩾ 2-fold) differential expression. The genes identified included those for the mitochondrial precursor of citrate synthase (CS), genes associated with plant defense responses, cell wall modification, plant hormone synthesis and signal transduction, and the structural constituents of ribosomes, as well as transcription and regulatory factors. The compositions and concentrations of organic acids and CS activities during preand post-irradiated fruit development were measured using HPLC and a UV-spectrophotometer. Comparative transcription profiling found several genes that could be related to "sourness" in 60Co-y-irradiated fruit. Our results also suggested that 60Co-y-irradiation changed mRNA levels for mitochondrial CS, followed by changes in CS protein levels and/or enzyme activities related to changes in citrate concentration. This may be the primary trigger for citrate accumulation in fruit, post-irradiation. [ABSTRACT FROM AUTHOR]

Halbach cylinder magnet has been widely used as field source due to its great features. However, the existence of the magnetic moment in the Halbach cylinder magnet limits its application in some fields. To eliminate the dipole moment of the whole magnet system, a method is presented here that incorporates permanent magnets to provide an opposite dipole moment. Both the FEM simulation and the experimental results demonstrate that this method is effective. [ABSTRACT FROM AUTHOR]

Combustion exhaust monitoring was simulated by measurement on a sulfur dioxide flow at different temperatures using broadband absorption spectroscopy and electrochemical analysis. A linear relationship with varying rates of slope for different temperatures was found between the gas concentrations obtained using the two methods, attributed to the influence of gas volume increase and absorption line broadening. By utilizing the differential absorption at an on/off pair combined with an experimentally determined temperature correction coefficient, the sulfur dioxide concentration was evaluated with the spectroscopic method yielding a measurement precision of 4%. [ABSTRACT FROM AUTHOR]

A series of InGaAsN/GaAs single-quantum wells (SQWs) with N contents varied from 0% to 5.3% were grown by molecular-beam epitaxy using a solid As and a nitrogen plasma sources. The impact of nitrogen concentration on the optical properties, as determined by the temperature dependence of photoluminescence (PL), of a 6 nm SQW was investigated. In the low-temperature region, a pronounced temperature-dependent S-shaped peak position was observed in PL spectra while increasing the nitrogen concentration. Quenching behavior reveals that the defect-related nonradiative processes might be enhanced in the highly nitrogen incorporated samples and thus influence the recombination dynamics. In addition, the evolution of the peak position of the InGaAsN/GaAs samples was in agreement with the empirical Varshni model in the high-temperature region. A significant reduction in the temperature dependence of the emission peak position is analyzed as well, and further confirms the prediction of proposed band anticrossing model of the electronic structure of III-N-V alloys. [ABSTRACT FROM AUTHOR]

Aim: To study the difference between pyridoxine (PN) and its active form, pyridoxal phosphate, (PLP) in control of idiopathic intractable epilepsy in children. Methods: Among 574 children with active epilepsy, 94 (aged 8 months to 15 years) were diagnosed with idiopathic intractable epilepsy for more than six months. All received intravenous PIP 10 mg/kg, then 10 mg/kg/day in four divided doses. If seizures recurred within 24 hours, another dose of 40 mg/kg was given, followed by 50 mg/kg/day in four divided doses. For those patients whose seizures were totally controlled, PLP was replaced by the same dose of oral PN. lithe seizure recurred, intravenous PLP was infused followed by oral PLP 50 mg/kg/day. Results: Filly seven patients had generalised seizures (of whom 13 had infantile spasms) and 37 had focal seizure. Eleven had dramatic and sustained responses to PLP; of these, five also responded to PN. Within six months of treatment with PLP or PN, five of the 11 patients were seizure free and had their previous antiepileptic medicine tapered off gradually. Two were controlled with pyridoxine and the other three needed PLP to maintain seizure freedom. The remaining six responders needed PLP exclusively for seizure control. Six of the 11 responders to PLP had infantile spasms (46%); four of them needed PIP exclusively. The other five responders were in the remaining 81 patients with other seizure type. Conclusions: PIP could replace PN in the treatment of intractable childhood epilepsy, particularly in the treatment of infantile spasms. [ABSTRACT FROM AUTHOR]

The structures of Pr[sub 0.7]Ca[sub 0.3]MnO[sub 3] thin films on LaAlO[sub 3] (001) and NdGaO[sub 3] (001) substrates were investigated using transmission electron microscopy. These substrates induce a significant compressive strain and a slight tensile strain respectively on the film, and quite different microstructures were found in the two cases. Many complex tangles of dislocations were found in the film on LaAlO[sub 3], and it had a two-domain structure where both domains have a [110] axis perpendicular to the film plane. The film on NdGaO[sub 3] was mostly defect free, apart from occasional precipitates, which appeared to be NaCl-structure MnO, and displayed a single domain structure with the [001] axis perpendicular to the film. The difference in domain structure was explained on the grounds of misfit minimization, and the possible consequences of such a dependence of the domain structure on the substrate for the magnetic properties were discussed. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the possible regulatory roles of insulin-like growth factors (IGF) and IGF binding protein-1 (IGFBP-1) on postmenopausal endometrium in women undergoing hormone replacement therapy (HRT). Endometrial tissues and blood samples were collected from 25 postmenopausal women with abnormal uterine bleeding before and after HRT. As a control, blood and endometrial samples were also obtained at mid-luteal phase (days 18-23 of the menstrual cycle) from 10 women with benign uterine leiomyoma during surgical intervention. Expression of mRNA for IGF-I, IGF-II, type 1-IGF receptor, IGFBP-1, oestrogen receptor (ER) and progesterone receptor (PR) in the endometrium was explored by a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). Serum concentrations of IGFBP-1, oestradiol, progesterone, follicle stimulating hormone (FSH) and sex hormone-binding globulin (SHBG) were also determined. In the endometrium obtained from postmenopausal women with abnormal uterine bleeding (before HRT), expression of IGFBP-1 was undetectable, whereas PR expression was abundant. HRT significantly up-regulated expression of IGFBP-1 but down-regulated PR. Moderate expression of IGF-I, IGF-II, type 1-IGF receptor and ER was identified in the postmenopausal endometrium before HRT. HRT significantly down-regulated IGF-I, up-regulated IGF-II, but had no effects on expression of type 1-IGF receptor and ER. In conclusion, up-regulation of IGFBP-1 collaboratively with down-regulation of IGF-I may account for the protective effect of progesterone in HRT on the endometrium. [ABSTRACT FROM AUTHOR]

Following the work reported in an earlier paper, the possibility of rejecting coherent interference of finite bandwidth and distributed direction of incidence by purely amplitude shading of a transducer array is investigated. Using the same linear transducer array immersed in the same distributed interference and ambient noise fields, it is demonstrated that, if the array shading is optimized by assuming all the interference power to be concentrated at its band center, interference of bandwidths up to 10% of its center frequency and intensity 70 dB above ambient noise field can be effectively rejected. This confirms that the theroy reported earlier is adequate for applications in narrow-band receiving systems. If a broadband interference power quadratic is used in the process of shading optimization, the above interference-rejecting capability can be extended to a bandwidth equal to 40% of its center frequency. These results further suggest that an optimum/adaptive broadband beamformer for passive sonar typically needs to be amplitude shaded in only eight bands. [ABSTRACT FROM AUTHOR]

It is demonstrated that strong coherent interference incident from arbitrary directions can be effectively rejected by amplitude shading or real weighting of channel signals. For a given spatial distribution of interference field, the total interference power received by a transducer array is formulated and superimposed on the power received from an isotropic noise field. The total noise plus interference power is then minimized with respect to the shading coefficients and subject to the constraint that the mainbeam peak be maintained at a fixed level. As an illustrative example, we have calculated the optimum amplitude shading coefficients for a linear array with logarithmically spaced transducer elements to reject an interference field uniformly distributed over a 15°×36° solid angle with an intensity up to 70 dB above the noise field. In each case, the directivity pattern of the array adjusts itself by bunching several null points in the direction of interference incidence to achieve a nearly complete rejection. The merit of a narrow-band processor based on the principle of optimum amplitude shading is then examined by comparing its performance with those of a conventional processor and an optimum processor with both amplitude and phase adaptation. The optimum amplitude shading processor is clearly superior to the ocnventional processor under strong interference, but much simpler to implement than the optimum processor with amplitude and phase adjustment. Furthermore, the very little additional SNR0 due to complex weighting probably cannot be achieved in practice because of the extreme super-gain condition which often results. [ABSTRACT FROM AUTHOR]

The signal processing gain by digital beamforming in Doppler sonar was investigated in terms of the enhancement of signal-to-reverberation ratio (SRR) at the postbeamforming Doppler-filter output with an objective to determine the minimum number of bits necessary for the quantization of beamformer channel input signals without appreciable degradation of sonar performance. The formulation of the problem follows closely the author's earlier work which extends Davenport's analysis of bandpass limiter to the more general multichannel multibit signal processors. Owing to the Doppler shift of target signal frequency and the relatively narrow bandwidth of Doppler filters, we express the frequency selective effect in the nonlinear interacting power series in terms of a new set of coefficients cmk, which bear crucial significance in sonar performance. Extensive numerical calculations of ''Doppler processing gain'' were carried out to demonstrate that four-bit quantization of array transducer signals is theoretically sufficient to yield a performance essentially identical to that of a linear beamformer, but severe loss of gain could result if fewer than four bits are taken at the quantizer output. It is further demonstrated numerically and substantiated analytically that, for small input SRR, the processing gain of a digital beamformer with Doppler filters cannot exceed that of a linear (or optimized four-bit digital) beamformer even it its channel signals are quantized into more than four bits. [ABSTRACT FROM AUTHOR]

Amplitude shading is an important technique for controlling the beamwidth and sidelobe level of transmitting and receiving arrays in sonar and radar. The traditional method of Dolph-Tchebyscheff synthesis for the determination of array amplitude shading or weighting coefficients is, however, highly restrictive despite the extension and generalizations by many workers following Dolph. This paper outlines an entirely new method of finding these shading coefficients by minimizing the power received by the array in an isotropic noise field exclusive of a three-dimensional spatial slice around the mainbeam direction. The method is completely general in the sense that it is applicable to any discrete array of transducers arbitrarily distributed in a three-dimensional space. As an illustrative example, nonuniformly spaced linear arrays (which are necessary for reasons of economy and operation over a band of frequencies) are shown to have been successfully shaded to acceptable pattern shape and sidelobe levels. In the special case of equally spaced linear transducer arrays, the new method of shading yields an essentially identical mainbeam shape as Dolph-Tchebyscheff's for the same sidelobe level, while the total power received (or transmitted) via the sidelobes is actually slightly less than one half of that by the latter synthesis. Necessary detailed mathematical formulas for applying the method to circular or arc arrays are also suggested. Subject Classification: 30.82; 20.15; 60.30. [ABSTRACT FROM AUTHOR]

Utilizing a formulation of output power of a digital beamformer with input quantizers of unequal input and output step sizes given previously, the optimum quantizer step sizes which yield maximum processing gain for a typical array were searched by the method of 'steepest ascent' with a digital computer. For the case of two-bit /channel quantization with small input SNR (<= - 10 dB), the array gain surface as a function of two independent step variables exhibits a maximum which is only slightly greater than the maximum array gain achievable with uniform input quantizers. For larger input SNR, the array gain surface tends to be concave upward, and the performance of uniform quantizers can at the best be a suboptimum. The high theoretical processing gain in the limiting case of very large step sizes is attributed to a threshold effect of the input quantizers. Except for these latter conditions, the optimum uniform quantizing condition previously reported by the author represents essentially valid optimum design. [ABSTRACT FROM AUTHOR]

The formulation of output autocorrelation function of a digital beamformer into an infinite series leads naturally to the introduction of 'quantizer functions' of various orders as a convenient vehicle in the evaluation of beamformer performance corresponding to different input quantizer designs. For arrays operating in a Gaussian ambient noise field, the quantizer function of a general nonuniform quantizer is defined and evaluated in terms of 'reduced Hermite polynomials,' which facilitate less costly machine computation via their unique recursion formulae. A rigorous proof of the convergence of the series of quantizer functions is given to ensure confidence in numerical results. Examples of the use of quantizer functions given are (i) determination of optimum step sizes of 2-, 3-, and 4-bit uniform quantizers which yield maximum array gain for a typical array, (ii) calculation of directivity patterns of digital beamformer with input signals of arbitrary bandwidth, and (iii) evaluation of the effect of post filtering on the directivity patterns of digital beamformers. The special case of 1 bit per channel quantization (DIMUS) was especially discussed in detail with respect to both array gain and directivity patterns. The use of quantizer functions can also be extended to the solution of active-sonar problems involving sine-wave signals, and a brief example was given to illustrate the partial recovering of clipping loss in DIMUS by post filtering. [ABSTRACT FROM AUTHOR]