A single-chip 12.7 Mchips/s digital IF BPSK direct sequencespread-spectrum transceiver in 1.2 μm CMOS

This paper describes a fully integrated digital-spread spectrum transceiver chip fabricated through MOSIS in 1.2 μm CMOS. It includes a baseband spread spectrum transmitter and a coherent intermediate frequency (IF) receiver consisting of a Costas loop, an acquisition loop for the pseudo-noise (PN) sequence, and a clock recovery loop with a 406.4 MHz onchip numerically controlled oscillator (NCO). The transceiver is capable of operating at a maximum IF sampling rate of 50.8 MS/s and a maximum chip rate of 12.7 R Mchips/s (Mcps) with selectable data rates of 100, 200, 400, and 800 kbps. At the maximum operating speed of 50.8 R MS/s, it dissipates 1.1 W. In an additive white Gaussian noise channel the IF receiver achieves a receiver output SNR within 1 dB of theory and can acquire code with a wide range of input SNR from -17 dB to over 30 dB. The transceiver chip has been interfaced to an RF up/down converter to demonstrate a wireless voice/data/video link operating in the 902-928 MHz band     

Influence of the purity of the starting materials on the recording of dynamic holograms in Bi12TiO20 crystals

The parameters of Bi₁₂TiO₂₀ crystals grown with bismuth oxide of different degrees of purity were measured by a holographic recording technique in an external ac electric field and were compared with a crystal specially doped with chromium. Various crystal parameters such as the diffusion length of the photoexcited carriers and the Debye screening length were determined. It was found that the absorption spectrum of the material and the holographic recording efficiency were strongly influenced by light chromium doping and by insufficient purity of the starting mixture. Pis’ma Zh. Tekh. Fiz. 23, 27–32 (March 12, 1997)     

EFFECT OF STORAGE ON THE RHEOLOGICAL BEHAVIOUR OF BABY FOODS

The effect of storage temperature on rheological behaviour of four varieties of baby foods was studied. After 24-month storage at 15C and 25C, the constant A in Weltman model increased significantly for the vegetables, meat and fish samples, and decreased significantly for the fruit samples. After 24-month storage at 5C and 15C there were no significant changes in flow behavior index, consistency index and yield stress of the Herschel-Bulkley model for the vegetables, meat, fish and fruit samples. Increase in storage temperature decreased the consistency index and yield stress of the fruit samples.     

NMR IMAGING, CALORIMETRIC, and MATHEMATICAL MODELING STUDIES of FOOD FREEZING

Nuclear magnetic resonance imaging (MRI), calorimetry, and temperature measurements were used to monitor cylindrical potato sections frozen at -11C and -42C. MRI showed the advance of the nonsymmetric freezing zone and loss of signal intensity as liquid water turned to ice. Differential calorimetry was used to follow heat removal during transient freezing. Measured times to 95% enthalpy change were 24 min (-42C) and 49 min (-11C), as compared to modeled values of 29 min (-42C) and 100 min (-11C). Times to 95% change in the NMR signal, integrated over the area of the image, were 21 min (-42C) and 56 min (-11C). Changes in NMR signal intensity could be correlated with the amount of unfrozen water remaining after a steady-state had been reached. At -42C, NMR indicated 25% unfrozen water remaining as compared to 26% by calorimetry, and 22% by modeling. At -11C, NMR measured 67% unfrozen water remaining as compared to 48% by calorimetry, and 25% by equilibrium modeling.     

Antibacterial activity of sourdough lactic acid bacteria: isolation of a bacteriocin-like inhibitory substance fromLactobacillus sanfranciscoC57

A total of 232 strains from nine species ofLactobacillusisolated from sourdoughs were screened for antagonistic activity against sourdough-related micro-organisms. Seventy-seven strains on agar medium and 52 in culture supernatants, re-adjusted to pH 6.5 and catalase-treated, showed antagonistic activity. The activities were species and strain specific showing different spectra of inhibition against sourdough lactobacilli. All the strains were inhibitory toBacillus subtilisbut not against sourdough yeasts and moulds.Lactobacillus sanfranciscoandLactobacillus plantarumstrains had the largest inhibitory spectrum. All the antimicrobial compounds produced from strains of different species contained a protein moiety and were differently sensitive to different proteinases. A bacteriocin-like inhibitory substance, which was heat-stable (100°C for 20 min), insensitive to lipase and α-amylase, of a protein nature, with an inhibitory spectrum centred about lactic acid bacteria and a bactericidal or bacteriolytic mode of action was isolated fromLb. sanfranciscoC57. The antimicrobial substance also inhibitedListeria monocytogenes, and was mainly produced in the stationary phase of growth and at pH 4.0–5.0.Lb. sanfranciscoC57 variants, which did not contain the nativec. 17 kbp plasmid, maintained their antagonistic activity, therefore, the gene encoding for the bacteriocin-like inhibitory substance fromLb. sanfranciscoC57 is chromosomally located.     

Detecting delaminations in a composite beam using anti-optimization

The present study proposes a detection technique for delaminations in a laminated beam. The proposed technique optimizes the spatial distribution of harmonic excitation so as to magnify the difference in response between the delaminated and intact beam. The technique is evaluated by numerical simulation of two-layered aluminum beams. Effects of measurement and geometric noise are included in the analysis. A finite element model for a delaminated composite, based on a layer-wise laminated plate theory is used in conjunction with a step function to simulate delaminations     

Joint stick-slip friction compensation of robot manipulators by using smooth robust controllers

In this article, two new smooth robust nonlinear compensators have been developed, respectively, for positional regulation and trajectory tracking of rigid robot manipulators with internal joint stick-slip friction. The proposed controllers can improve not only the positioning accuracy but also the smoothness of motion. No exact knowledge of the friction models is required for the design of the controllers. Furthermore, the tracking controller is also robust with respect to the uncertain link parameters. Using Lyapunov's direct method, we can show that the time-invariant positional regulation controller guarantees the global boundedness stability of the closed-loop system, while the time-varying positional tracking controller guarantees the global asymptotic stability of the closed-loop system. The numerical simulations of the controllers on a two-link robot are presented as illustrations. © 1994 John Wiley & Sons, Inc.     

Epstein-Barr virus recombinants from overlapping cosmid fragments

Five overlapping type 1 Epstein-Barr virus (EBV) DNA fragments constituting a complete replication- and transformation-competent genome were cloned into cosmids and transfected together into P3HR-1 cells, along with a plasmid encoding the Z immediate-early activator of EBV replication. P3HR-1 cells harbor a type 2 EBV which is unable to transform primary B lymphocytes because of a deletion of DNA encoding EBNA LP and EBNA 2, but the P3HR-1 EBV can provide replication functions in trans and can recombine with the transfected cosmids. EBV recombinants which have the type 1 EBNA LP and 2 genes from the transfected EcoRI-A cosmid DNA were selectively and clonally recovered by exploiting the unique ability of the recombinants to transform primary B lymphocytes into lymphoblastoid cell lines. PCR and immunoblot analyses for seven distinguishing markers of the type 1 transfected DNAs identified cell lines infected with EBV recombinants which had incorporated EBV DNA fragments beyond the transformation marker-rescuing EcoRI-A fragment. Approximately 10% of the transforming virus recombinants had markers mapping at 7, 46 to 52, 93 to 100, 108 to 110, 122, and 152 kbp from the 172-kbp transfected genome. These recombinants probably result from recombination among the transfected cosmid-cloned EBV DNA fragments. The one recombinant virus examined in detail by Southern blot analysis has all the polymorphisms characteristic of the transfected type 1 cosmid DNA and none characteristic of the type 2 P3HR-1 EBV DNA. This recombinant was wild type in primary B-lymphocyte infection, growth transformation, and lytic replication. Overall, the type 1 EBNA 3A gene was incorporated into 26% of the transformation marker-rescued recombinants, a frequency which was considerably higher than that observed in previous experiments with two-cosmid EBV DNA cotransfections into P3HR-1 cells (B. Tomkinson and E. Kieff, J. Virol. 66:780-789, 1992). Of the recombinants which had incorporated the marker-rescuing cosmid DNA fragment and the fragment encoding the type 1 EBNA 3A gene, most had incorporated markers from at least two other transfected cosmid DNA fragments, indicating a propensity for multiple homologous recombinations. The frequency of incorporation of the nonselected transfected type 1 EBNA 3C gene, which is near the end of two of the transfected cosmids, was 26% overall, versus 3% in previous experiments using transfections with two EBV DNA cosmids. In contrast, the frequency of incorporation of a 12-kb EBV DNA deletion which was near the end of two of the transfected cosmids was only 13%.(ABSTRACT TRUNCATED AT 400 WORDS)     

A comparison of mail and telephone interview strategies for mental health surveys

The high cost of mental health surveys of the general population has sparked interest in less costly research methods. Two low-cost mental health survey strategies (mail and telephone) were compared in terms of cost, response rate and quality of data obtained. A total of 1,074 persons agreed to participate in the study as a sample, one-half by telephone and the other half by mail. They completed the Diagnostic Interview Schedule Self-Administered, a questionnaire designed to be self-administered, which was used to assess specific mental disorders and to evaluate risk factors. In addition, 239 respondents who were selected according to the presence or absence of specific diagnoses were reinterviewed face-to-face using the Diagnostic Interview Schedule as an external criterion. The telephone method yielded a better response rate (15% higher) and better control over answers (for example, less missing data). The mail strategy was less expensive and appeared to yield data of slightly better quality, particularly for respondents suffering from anxiety disorders.