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51.
The efficiency and accuracy of estrus detection using HeatWatch (DDx Inc., Denver, CO) or visual observation were compared in an autumn-calving Friesian herd (n = 48 per group) and a spring-calving Jersey herd (n = 50 per group) grazing on pasture. Cows in the group monitored by the HeatWatch system were fitted with a pressure-sensitive transmitter that signaled mounting activities associated with estrus. Visual observation was carried out for about 20 min before the morning and afternoon milkings and was aided by a strip of paint applied over the tailhead. Ovarian cyclicity was monitored with progesterone concentrations in milk samples collected twice a week. The efficiency and accuracy of estrus detection were, respectively, 98.4 and 97.6% for visual observation and 91.7 and 100% for HeatWatch detection. Autumn-calving herds differed from spring-calving herds in duration of estrus (9.7 vs. 7.3 h), number of mounts (13.6 vs. 8.5), total duration of mounts (36.8 vs. 19.9 s), and mean duration of a mount (2.6 vs. 2.3 s). There was no significant variation in the distribution of the time of onset of estrus or mounting activities at different hours of the day. Conception rate was similar for AI after estrus detection with HeatWatch (65.8%) or after visual observation (65.0%). The highest conception rate was obtained when AI was carried out between 12 and 18 h after the first mount. Both the HeatWatch system and visual observation plus tail painting can be used for estrus detection of dairy cows on pasture.  相似文献   
52.
This study examined the relationship of global Type A behavior and its components (time pressure and hard-driving competitiveness) with individual and organizational outcomes. Data were collected by means of a structured questionnaire from hospital employees (n=175) and telecommunication employees (n=110) in a large Canadian city. Global Type A behavior and its 2 components were significantly related to job stress, health problems, job satisfaction, organizational commitment, and turnover motivation in both samples. Limited support for the differential effects of Type A component measures on outcomes was found. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
53.
Adaptive turbo-coded modulation for flat-fading channels   总被引:1,自引:0,他引:1  
We consider a turbo-coded system employed on a flat-fading channel where the transmitter and receiver adapt the encoder, decoder, modulation scheme, and transmit power to the state of the channel. Assuming instantaneous and error-free channel gain and phase knowledge at the transmitter and the receiver, we determine the optimal adaptation strategy that maximizes the throughput of this system, while achieving a given bit-error rate under an average power constraint. Our optimized adaptive modulation strategy is based on an extensive set of existing turbo-coded modulation schemes. We find that adapting both the turbo encoder (rate) and the transmit power can achieve performance within 3 dB of the fading channel capacity.  相似文献   
54.
The conventional two-bubble-class model for bubble column reactors has been modified to account for interactions between the two bubble classes. It is shown that the modified model is more consistent with the observed residence time distribution in the gas phase than the conventional model. The results indicate that there is an intensive cross-mixing between the bubble phases. This study also reveals that the modified two-bubble-class model cannot be distinguished from the single-bubble-class model solely on the basis of the residence time distribution.  相似文献   
55.
Black carrot, a potential source of anthocyanin pigment, has high antioxidant activity. The effect of pre-press maceration treatment with different doses of cell wall degrading enzyme pectinase (Aspergillus niger Teigh) on antioxidant composition of black carrot juice was investigated. Enzyme-assisted processing significantly (p < 0.05) improved the antioxidant composition of black carrot juice. There was an overall increase of 33% in juice yield, 27% in total phenolics and 46% in total flavonoids. The total anthocyanin content in black carrot juice was almost doubled. The in vitro total antioxidant activity in black carrot juice extracted through enzyme-assisted processing was 30.0 and 62.0 μmol TE/mL in ferric reducing antioxidant power (FRAP) and cupric reducing antioxidant capacity (CUPRAC) assays, respectively.There was 30% increase in total antioxidant activity of black carrot juice extracted with enzyme over straight pressed juice. The results indicate that tailoring of specific enzyme mixtures can yield antioxidant rich juice products. Optimizing a strategy for extraction of phenolic rich juice from black carrots can offer an opportunity for its utilization in developing novel functional beverages with enhanced color appeal and high antioxidant activity.  相似文献   
56.
Sarcoidosis (S) is a systemic disease affecting above all lymph nodes and lung tissue. Skeletal involvement is reported to occur in 14% of patients, the most common manifestations is cystoid osteitis, an asymptomatic lesion localized to the small bones of hand and feet. Lytic lesions are rare and usually accompanied by visceral involvement, the lesions may be detected in vertebral bodies and in long bones, pelvis and scapulae. MRI may be a good diagnostic tool, but open biopsy is often necessary. Joints are involved in about 89% of patients with acute sarcoidosis. Arthritis is localized more frequently to knees and ankles, is polyarticular, a little painful, migratory and transient, often accompanied by erythema nodosum. Clinical manifestations disappear in a few weeks, chronic and erosive disease is rare and always associated with systemic involvement. In these patients it may be useful to perform gallium citrate 67 scintigram and evaluation of serum ACE. Synovial biopsy lacks of specificity and sensibility, and in some cases it is necessary to perform open biopsy. S is a disease that may spontaneously regress and therapy may be unnecessary. In some cases, methotrexate may be useful in addition to prednisone. Chloroquine and hydroxychloroquine are effective in cases of skeletal involvement.  相似文献   
57.
Although a code-division multiple-access (CDMA) system is spectrally efficient and has some immunity against intentional reception, its capacity and performance are generally limited by multiple access interference (MAI) caused by other users. For an aperiodic CDMA system, the spreading sequences span multiple symbol intervals, and the cross-correlations between these sequences, which are a measure of the MAI, are periodic over multiple symbols. In this paper, we present a receiver with a parallel architecture that converts an aperiodic CDMA sequence into a piecewise periodic sequence in each arm. We refer to this receiver as a cyclodespreader because the despreader exploits the cyclostationary property of an aperiodic signal. As a result, the transmitted data can be detected separately in each arm of the receiver using low-complexity conventional algorithms proposed for periodic CDMA systems. The goal of the receiver is to decode several signals received from different cochannel base stations. The performance of the system is evaluated using real aperiodic CDMA signals, and it is compared to that of a conventional matched filter (MF) receiver using the number of correctly decoded messages as the performance measure.  相似文献   
58.
The swelling and diffusion characteristics of a polar polymer [ethylene vinyl acetate (EVA)] and a nonpolar polymer [low-density polyethylene (LDPE)] were studied with swelling experiments of the polymers in asphalt at different temperatures. The study showed that the diffusion mechanisms for LDPE and EVA were different and temperature-dependent. In the case of LDPE, the observed diffusion was anomalous at both swelling temperatures (70 and 90°C). LDPE at 90°C showed sigmoidal solvent-uptake behavior during the initial period of swelling and a sorption overshoot in a later period. EVA showed Fickian transport at 60°C and anomalous diffusion at a higher swelling temperature (70°C) with sigmoidal uptake behavior. An analysis of the diffusion coefficients and the Fourier transform infrared results showed that the diffusing molecules were different in the case of LDPE and EVA, and there were possible polymer–asphalt interactions. Differential scanning calorimetry and swelling studies showed that penetrant-induced crystallization affected the diffusion process in the case of LDPE. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
59.
This paper presents a novel method for detecting stator winding inter-turn short circuit fault in a three-phase induction motor by vibration signature analysis using non-electrical contact type microelectromechanical systems (MEMS) accelerometer. The present work detects inter-turn short circuit by vibration analysis in a three-phase induction motor running under different load conditions. Theoretical analysis of stator winding under inter-turn short circuit condition has been presented. Experimental investigations have been carried out to detect inter-turn short circuit fault by vibration signature analysis using a MEMS accelerometer with three-phase induction motor operating under different conditions. The spectral analysis of motor vibration has been carried out using radix-2 decimation in time fast Fourier transform algorithm. The appearance of particular characteristic frequency components in vibration spectrum indicates stator winding inter-turn short circuit faults. The experimental results are found to closely match with the theoretical values, indicating that MEMS accelerometers can be successfully employed for the detection of stator winding inter-turn short circuit fault in induction motors.  相似文献   
60.
A comparison of enzyme activities has been made between a site-specifically immobilized and a randomly immobilized bacterial alkaline phosphatase (BAP) on macroporous membranes. An octapeptide tag (FLAG™) was attached at the N-terminus of alkaline phosphatase by recombinant DNA techniques (gene fusion) to yield BAP that is modified in a site-directed fashion (SDBAP). The corresponding antibody (antiFLAG™) was immobilized on an aldehyde-modified polyethersulfone (MPS) membrane via protein A. Immobilization of SDBAP on this membrane result in a membrane–protein A–antiFLAG–SDBAP linkage. This site-specifically immobilized enzyme demonstrated a relative activity (RA), defined as the ratio of immobilized activity (Vmax) to the corresponding homogeneous enzymatic activity, of 85% as compared with the randomly immobilized BAP which had an RA of 0·8%. BAP, when chemically conjugated to the FLAG peptide and immobilized via antiFLAG and protein A on the MPS membrane, showed an RA of only 1·9%, demonstrating the effectiveness of site-directed immobilization. SDBAP was also immobilized on the MPS membrane in the absence of protein A. In this case, the RA dropped to 22%, further explaining the effectiveness of ordered immobilizations as compared with random immobilizations. The ratio of immobilized enzyme activity to the activity in the absence of added phosphate inhibitor for the immobilized BAP was three-fold higher than the corresponding homogeneous ratio, showing a reduction in product inhibition for the immobilized enzyme. © 1997 SCI.  相似文献   
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