A BiCMOS Differential Amplifier and Timing Discriminator for the Receiver of a Laser Radar

A differential BiCMOS amplifier channel with gain control circuitry and a timing discriminator has been designed for a pulsed time-of-flight laser radar. The measured bandwidth of the amplifier channel is 160 MHz and its gain can be controlled with a variable R-2R ladder attenuator in 7 discrete steps from 0.44 to 23. A peak detector, used for gain control, can detect the peak of a single 10 ns pulse, the amplitude of which varies from 50 mV to 3.5 V. The timing discriminator produces accurately timed logic level pulses from noisy analog output pulses of the amplifier channel. The distance measurement result of the designed timing discriminator varies +/– 4 mm with an input amplitude range of 55 mV – 3.3 V. The single shot resolution with SNR = 250 is better than 6 mm. Measurement results suggest that a cm-level distance measurement accuracy can be realized using integrated ASICs.     

A current-mode gain-control scheme with constant bandwidth andpropagation delay for a transimpedance preamplifier

This paper presents a current-mode gain-control scheme that significantly increases the input dynamic range of a wideband optoelectronic receiver without affecting its bandwidth or delay or deteriorating its noise properties. A current buffer with variable attenuation is placed between the photodetector and the transimpedance preamplifier. In this way, the input dynamic range of the receiver can be increased, or alternatively, the signal dynamics can be reduced, by over 20 dB. A BiCMOS test circuit designed for a pulsed time-of-flight laser rangefinder has a measured bandwidth of 170 MHz and an input dynamic range of ~80 dB. The delay varies only ±5 ps when the gain is varied by 24 dB (1:15)     

Deletion of Col15a1 Modulates the Tumour Extracellular Matrix and Leads to Increased Tumour Growth in the MMTV-PyMT Mouse Mammary Carcinoma Model

Basement membrane (BM) zone-associated collagen XV (ColXV) has been shown to suppress the malignancy of tumour cells, and its restin domain can inhibit angiogenesis. In human breast cancer, as well as in many other human carcinomas, ColXV is lost from the epithelial BM zone prior to tumour invasion. Here, we addressed the roles of ColXV in breast carcinogenesis using the transgenic MMTV-PyMT mouse mammary carcinoma model. We show here for the first time that the inactivation of Col15a1 in mice leads to changes in the fibrillar tumour matrix and to increased mammary tumour growth. ColXV is expressed by myoepithelial and endothelial cells in mammary tumours and is lost from the ductal BM along with the loss of the myoepithelial layer during cancer progression while persisting in blood vessels and capillaries, even in invasive tumours. However, despite the absence of anti-angiogenic restin domain, neovascularisation was reduced rather than increased in the ColXV-deficient mammary tumours compared to controls. We also show that, in robust tumour cell transplantation models or in a chemical-induced fibrosarcoma model, the inactivation of Col15a1 does not affect tumour growth or angiogenesis. In conclusion, our results support the proposed tumour suppressor function of ColXV in mammary carcinogenesis and reveal diverse roles of this collagen in different cancer types.     

A 250-MHz BiCMOS receiver channel with leading edge timing discriminator for a pulsed time-of-flight laser rangefinder

An integrated receiver channel of a pulsed time-of-flight (TOF) laser rangefinder for fast industrial measurement applications with the measurement accuracy of a few centimeters in the measurement range from /spl sim/1 m to /spl sim/30 m to noncooperative targets was developed. The receiver channel consists of a fully differential transimpedance amplifier channel, a peak detector, an rms meter and a timing discriminator. In this particular application there is no time to measure the received signal strength beforehand and it is not predictable from previous measurements, so a leading edge timing discriminator with a constant threshold voltage was used. The amplitude of the received pulse is measured with a peak detector and the amplitude information is used to compensate for the resulting walk error. The measured bandwidth of the receiver channel is 250 MHz, the maximum transimpedance 40k/spl Omega/ and the input-referred noise /spl sim/7pA//spl radic/Hz (C/sub photodiode/=2 pF). The timing detection accuracy of the receiver is better than /spl plusmn/35 mm in a single-shot measurement in a dynamic range of 1:4000 and a temperature range of 0/spl deg/C to +50/spl deg/C.     

Pn Photodiodes for Pulsed Laser Rangefinding Applications Realized in Standard CMOS/BiCMOS Processes

This paper describes simulation of theoperation of integrated high-speed photodiodes and verification of the results bymeans of measurements performed with two typesof photodiode, one implemented in a standard 0.8m CMOS process and the other in a standard1.2 m BiCMOS process. The measured rise timesand responsivities of the photodiodes were <5ns and 0.28 A/W in the CMOS process and 30 ns and0.31 A/W in the BiCMOS process. Furthermore, thesuitability of the photodiode for 3D vision wasinvestigated by designing an array ofphotodetectors and measuring the isolationbetween the detector blocks. The results confirmthat the photodetectors and receiver for a pulsedlaser rangefinder can be implemented on the samechip in a standard process without any processmodifications.     

Taurine infused intrastriatally elevates, but intranigrally decreases striatal extracellular dopamine concentration in anaesthetised rats

In the present study we infused taurine (50, 150 or 450 mM, 2 microliters/min for 4h) into the dorsal striatum or into the substantia nigra via microdialysis probe and estimated the extracellular concentrations of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in the dorsal striatum of anaesthetised rats. Intrastriatal infusion of taurine elevated striatal dopamine at all concentrations studied. At the 450 mM concentration taurine elevated the extracellular dopamine 10-fold, but only in the first 30 min sample after starting the taurine infusion. At 50 and 150 mM taurine elevated dopamine throughout the 4h infusion maximally up to 3-4-fold the control level. Extracellular DOPAC was increased by 150 and 450 mM taurine (up to about 150-160% of the control level), whereas at all three concentrations taurine decreased HVA to about 85% of the control; however, the decrease caused by 450 mM taurine was short-lasting. At all three concentrations taurine infused into the substantia nigra decreased the extracellular dopamine in the ipsilateral striatum to about 40-50% of the control, and increased extracellular DOPAC and HVA maximally to about 150% and 170% of the control, respectively. These results show that the effects of taurine on the concentrations of extracellular dopamine and its metabolites depend on its administration site on nigrostriatal dopaminergic neurons. It elevates the extracellular dopamine when given into the striatum, but when given into the cell body region of the nigrostriatal dopaminergic pathway it decreases the extracellular dopamine in the ipsilateral striatum.     

PET studies on brain monoamine transporters with carbon-11-beta-CIT in Parkinson's disease

The cocaine analog 2 beta-carbomethoxy-3 beta-[4-iodophenyl]tropane (beta-CIT) labeled with 11C was used to study dopamine reuptake sites with PET. METHODS: Three normal subjects and nine patients with Parkinson's disease were investigated. Each of them underwent a dynamic PET scan (25 timeframes over 80 min) with [11C]-beta-CIT. A dose of 102.5-211.3 MBq (2.77-5.71 mCi) of this ligand was administered intravenously and a PET examination with an ECAT 931/08 PET camera was carried out. Ratios between the striatal/cortical/thalamic/midbrain and cerebellar uptake of this radioligand were calculated. RESULTS: The highest accumulation of [11C]beta-CIT was observed in the caudate and putamen, though there was some uptake in the thalamus and the midbrain. Cortical uptake was negligible. Carbon-11-beta-CIT accumulated significantly less in the putamen of the Parkinson's patients than in the normal subjects. The putamen-to-cerebellum ratio in the Parkinson's patients was 1.59 +/- 0.04 and 1.80 +/- 0.13s (p = 0.028) in the normal subjects. In the caudate, there was no significant difference between the Parkinson's patients and the normal subjects. CONCLUSION: These results imply that [11C]beta-CIT is a useful compound for carrying out a PET examination of the function of the presynaptic monoaminergic neurons both in normal and pathological brains.     

THE IDENTIFICATION OF SEASONAL AUTOREGRESSIVE MODELS

Abstract. In this paper we present a new approach for identifying seasonal autoregressive models and the degree of differencing required to induce stationarity in the data. The identification method is iterative and consists in systematically fitting increasing order models to the data and then verifying that the resulting residuals behave like white noise using a two-stage autoregressive order determination criterion. Once the order of the process is determined the identified structure is tested to see if it can be simplified. Simulation experiments based on different model structures with varying numbers of observations and parameter values as well as some macroeconomic data are used to evaluate the performance of the procedure.     

Striatal 6-[18F]fluorodopa accumulation after combined inhibition of peripheral catechol-O-methyltransferase and monoamine oxidase type B: differing response in relation to presynaptic dopaminergic dysfunction

The aim was to investigate the effects of inhibition of monoamine oxidase type B (MAO-B) with selegiline alone and the combined inhibition of peripheral catechol-O-methyltransferase (COMT) with entacapone and MAO-B with selegiline on striatal 6-[18F]fluorodopa (FDOPA) accumulation, and whether the effect of entacapone + selegiline on FDOPA uptake differed depending on the severity of the presynaptic dopaminergic dysfunction. Thus, eight healthy controls, eight de novo patients with Parkinson's disease (PD), and 18 levodopa-treated PD patients were investigated with positron emission tomography (PET). Half of the subjects in each population belonged to the selegiline group and half to the entacapone + selegiline group. Both groups were studied twice with PET using FDOPA. After the first (baseline) FDOPA PET investigation, both groups were on 2 weeks of selegiline treatment, 10 mg daily. Thereafter, the second FDOPA PET was performed for all subjects with a premedication administered 60 min before the PET imaging; one group received 10 mg of selegiline, and the other group received a single 400 mg dose of entacapone coadministered with 10 mg of selegiline. Selegiline treatment alone had no significant influence on striatal FDOPA metabolism. The FDOPA accumulation, expressed as striatal-to-occipital ratios and modified decarboxylation coefficients (k3R0), increased significantly after entacapone + selegiline administration in all subject populations. The FDOPA uptake rate constant (Ki) remained virtually unchanged in controls and in de novo patients but decreased significantly in levodopa-treated PD patients after entacapone + selegiline intake. Entacapone + selegiline administration did not influence significantly the unidirectional blood-to-brain clearance for FDOPA (K1D) or the relative dopadecarboxylase activity (k3D). The changes in the studied parameters after entacapone + selegiline administration probably reflect the effects of entacapone, since entacapone alone has caused similar changes in previous PET studies. Response in FDOPA accumulation to entacapone + selegiline was higher in controls and de novo patients compared with levodopa-treated PD patients. The milder response in levodopa-treated patients might reflect the reduced ability of the degenerated dopaminergic neurons to utilize the prolonged FDOPA availability, produced by entacapone.