Analog Pulse Research Articles

Bone morphogenetic protein-2 stimulates cell recruitment and cementogenesis during early wound healing.

The unique action of bone morphogenetic proteins (BMPs) on mineralised tissue formation indicates that BMPs are good candidates for use in stimulating periodontal regeneration. Relatively little is known about the mechanisms of actions of BMPs during periodontal regeneration, although recent evidence from our laboratory suggests that the effects of BMPs may be profoundly influenced by various factors including root surface conditioning, delivery systems and masticatory forces. The aim of this study was to investigate the effect of rhBMP-2 on cell recruitment during periodontal regeneration using a pulse-chase technique where cells are labelled with a thymidine analogue (BrdU) (pulse) and the migration of their progeny is followed (chase) during early wound healing. The relationship between the rhBMP-2 influence on cell recruitment from the periodontal ligament (PDL) and its ability to stimulate cementogenesis was also evaluated. The buccal aspect of the distal root of the first molar was denuded of its PDL, cementum and superficial dentine through a bony window created in the mandible of 64 Wistar rats under general anaesthesia. Test animals were treated with 10 microL of 500 microg/ml rhBMP-2 in a collagen membrane sponge (n=32) and control defects received 10 microl of saline in a collagen sponge (n=32). All animals received an intraperitoneal single pulse injection of 40 mg/kg BrdU label 2 days postoperatively. Groups of test and control animals (n=8) were killed 2 hours later on day 2 and at 4, 7 and 10 days postoperatively. Mandibles were processed for histological examination. The results show that rhBMP-2 had a profound effect on proliferation and migration of cells in the adjacent and deeper aspects of the PDL at 7 and 10 days post periodontal wounding (p<0.05). Significantly greater new cementum formation occurred in the test group at 10 days (p=0.03). This study shows that following periodontal wounding rhBMP-2 stimulates cell recruitment by increasing proliferation and migration of cells from the adjacent unwounded PDL into the wounded area, thus promoting periodontal regeneration by increasing new cementum formation.

Distributed measurement and control system based on microcontrollers with automatic program generation

The paper describes an open architecture microcontroller based distributed measurement and control system with automatic generation of application program. Interpretation of functions and generation of program for control of the newly added distributed unit or distributed unit of a new type connected to the system performs automatically, without user assistance. The elements of the system are interconnected by means of a serial common bus according to the reduced OSI protocol. The proposed concept was tested in a system developed by using 8-bit Atmel microcontrollers of 89S and 89C series. Apart from the central unit, intelligent distributed units were developed for the control of a stepper motor, programmable linear movement, control of halogen lamps, acquisition and generation of analogue, digital and timing pulses and a real time clock (RTC).

Powder X-ray diffraction diagram with a silicon microstrip detector

The present paper reports on a complete diffraction pattern obtained with a 32 channels Si microstrip detector when a standard ZnO sample is illuminated with 8.04 keV photons. Information from single photon conversion in each detector channel is routed to a VLSI readout chain that contains analog amplification, pulse shaping, digitization and counting circuitry for each individual channel. The read out pitch is 200 /spl mu/m and data acquisition is performed with a custom made PC card. The current system represents an intermediate step toward a long linear array for powder X-ray crystallography.

OSS Responsibilities

We are all familiar with technological advances that have transformed the telecommunications industry in recent history. Why, it was only last millennium that the simplicity of digital signalling replaced the click-whirr of analogue pulses. With all these advances, we have taken for granted that sophisticated mechanisms exist behind the scenes to support the operation of the services we use. Your details are all filed on a computer somewhere. Whatever your provider needs to know about you, and the way you use the service, is all available at the touch of a button if they need it. Isn't it? This paper explores the story behind the scenes. In an exciting industry, keen to try out new ideas, and often racing to gain from new technology, we look at the race to keep support systems up to the task of handling new market offerings.

Development of a shaping amplifier, gated integrator and 16 K Channel ADC for a portable spectroscopy system

Fieldable, portable spectroscopy systems which provide 16 K channel space with high resolution and which can operate for long periods of time on readily available batteries are a valuable tool for environmental monitoring and non-proliferation applications. A low power portable spectroscopy system for use with a 100% n-type HPGE detector was recently completed by Constellation Technology Corporation. This system provides 16 K channel resolution while consuming under 1.3 W. A major component of this system, the ADC board assembly, implements a semi-Gaussian shaping amplifier, gated integrator, and analog-to-digital converter (ADC) to perform analog pulse processing and amplitude digitization of charge pulses from the detector preamplifier. All functions of the board are implemented onto a 4″×6″ circuit board using commercially available components. The board exhibits an integral non-linearity of less than ±0.015% over the top 99% of 16 K channels and a combined offset and gain temperature coefficient of 52.9 ppm/°C over a −25 to +85 degree Celsius temperature range. The power consumption for the board while converting at 10 kHz is 460 mW.

Lithium does not attenuate the effects of d-amphetamine in healthy volunteers

It has previously been suggested that an acute dose of 20 mg d-amphetamine can be a good model of mania. In the present study we attempted to validate this model by determining if subacute administration of lithium (for 7 days) would attenuate the effects of 20 mg d-amphetamine in human volunteers. Sixteen healthy volunteers were enrolled in this double-blind, placebo-controlled study. Subjects received either oral lithium at night for 7 nights (1200 mg) ( n=10) or matching placebo ( n=6). On day 8, subjects were assessed at baseline and then once each hour for 3 h following an oral dose of d-amphetamine (20 mg). Subjective states were measured with visual analog scales, and pulse, systolic and diastolic blood pressure were also repeatedly assessed. The results showed that d-amphetamine alone produced a number of subjective and cardiovascular changes, as expected. However, lithium did not attenuate any of these subjective or cardiovascular changes, as would be predicted if d-amphetamine were a valid model of mania. It is suggested that whilst d-amphetamine may produce effects similar to mania, its mechanism of action is different from that which occurs in mania, and therefore the usefulness of the amphetamine model of mania is called into question.

An electronic detector simulator for testing position, energy, and timing spectral performance of detector electronics

Repeatable and accurate spectral evaluation of detector front-end electronics is necessary to ensure proper operation of positron emission tomography (PET) and other nuclear detection systems. A block-detector simulator has been developed that repeatably emulates the position and energy spectral output of PET block detectors having four photomultiplier tubes (PMTs) to decode event position from a crystal scintillator matrix. The simulator operates by mapping uniform random numbers to representative position (X and Y) and energy (E) spectra. Digital event values of X, Y, and E are then converted to the four corresponding digital PMT values which are converted to shaped analog pulses emulating the detector output. Measured position and energy spectra taken with the detector simulator closely match those observed with actual detectors. Random (uniform) or coincident timing spectra are generated by selecting a simulator clock source that is either uncorrelated or correlated respectively with the detector electronics timing clock.

A 1.3 GHz SOI CMOS test chip for low-power high-speed pulse processing

A test chip has been fabricated in a fully depleted SOI CMOS process with 0.25-/spl mu/m drawn gate length, It successfully demonstrates the types of circuits required to perform digital filtering, detection, and data thinning functions at high clock speeds. The test chip contains over 5000 transistors and was clocked at speeds up to 1.3 GHz. A target application for these circuits is a very wideband compressive receiver for real-time spectral analysis, which requires digital signal processing to be performed on a 20-Gb/s data stream formed by digitizing a stream of fast analog pulses. Adjustable high-speed on-chip clocks, input and output registers, and large decoupling capacitors allowed testing of the chip to be performed using an inexpensive, low-speed probe card and a standard wafer prober.

Wavelets for waveform coding of digital symbols

A wavelet-based coder-decoder (codec) structure is defined for baseband waveform coding. Numerical results for bandwidth efficiency are given, and a comparison between several different wavelets is presented. Moreover, it is shown that wavelets obey the Nyquist pulse shaping condition and provide a unified framework for analog pulse shaping concepts of communications.

A fast, programmable, stand-alone pulse generator emulating spectroscopy nuclear events

The design of a fast, programmable, stand-alone pulse generator emulating spectroscopy nuclear events is described. The generator is one unit in a system aiming to test the validity of the simulation and theoretical work relating to the shaping, acquisition, and processing of spectroscopy signals in different experimental situations arising from different technical and scientific fields. The generator output, which also includes piled-up shapes, can be used in many different ways. For example, it can be used: (1) as an input to a charge sensitive preamplifier and shaping amplifier system; (2) as an input to a module for real-time digital shaping of spectroscopy pulses; and (3) it can generate a digital sequence emulating a digitally sampled analog pulse. The signals that it can emulate include those from simple charge sensitive preamplifiers, from more refined analog shapers, and the signals generated directly from scintillation detectors. The main element of the generator is the Analog Devices 21060, a fast and flexible digital signal processor (DSP). This paper considers various generator configurations arising from the need to reach a compromise among generator speed, shape resolution, and memory requirements. It is possible to program both the emulated average counting rate and the time interval between two consecutive samples (tns) using a predetermined pulse shape. The minimum tns value is equal to 10 ns in parallel configurations.

Design of a low noise, low power consumption CMOS preamplifier shaper for readout of microstrip detectors in the DMILL radiation hardened process and irradiation measurements

One of the proposed schemes of microstrip detector readout in the future LHC collider experiments is the use of a slow preamplifier with subsequent analog pulse shape processing (deconvolution) to recover initial time information. Following this idea a CMOS preamplifier shaper (CR-RC active filter) with 75 ns shaping time has been designed using a radiation hardened process DMILL. The tests of a prototype chip show a noise performance of ENC = 330 e− + 51 e−pF for a peaking time of 100 ns, gain of 30 mV/MIP and a power consumption of 1.1 mW per channel. Measurements after irradiation by γ photons, electrons and neutrons are also presented in this paper.

Analog pulse compression system for real-time ultrasonic non-destructive testing

An analog pulse compression system based on the use of a magnetoacoustic storage correlator as a pulse compressor is proposed, and a real-time operation of the system is demonstrated. The system offers good flexibility; it is not limited to any particular type of large time-bandwidth signal.

Performance of two-level PAM and analogue PWM hybrid optical fiber transmission systems

We analyze the performance of optical fiber transmission systems using a 2-level pulse amplitude modulation (PAM) and analogue pulse width modulation (PWM) hybrid technique. The system performance is evaluated by considering the signal-to-noise ratio (SNR) of 50 dB for video communications and the bit error rate (BER) of 10/sup -9/ for digital communications as a lower bound. Optical receivers using both avalanche photodiode (APD) and PIN photodiode are considered. The minimum average optical power, which is required by an analogue-PWM signal to guarantee the 50-dB SNR at an optical receiver, is calculated, while the receiver sensitivity is analyzed for a 2-level PAM digital optical fiber system. The results show that the proposed system can perform better than the required lower bound.

Digital two-level PAM and analogue PWM hybrid optical fiber transmission systems for TV and data applications

We propose a novel optical fiber transmission system for supporting both digital and analogue communications in a very cost-effective fashion. The proposed system simultaneously uses a 2-level pulse amplitude modulation (PAM) for data communications and an analogue pulse width modulation (PWM) for TV applications. The principle of the 2-level PAM and analogue PWM hybrid scheme is presented, and its some distinguishing features are explained. Moreover, this proposed technique requires the same transmission bandwidth as a conventional analogue PWM scheme. Consequently, two different types of communication services can be transmitted over a common optical fiber channel by using the 2-level PAM and analogue PWM technique, without the use of wavelength- or frequency- or time-division multiplexing.

A stochastic model for dual label experiments: an analysis of the heterogeneity of S phase duration

We develop a statistical approach for the study of S phase duration in experiments using sequential pulses of two thymidine analogues. Cell entrance into S phase is assumed to follow a possibly nonhomogeneous Poisson process, and the duration in S phase independently follows an unspecified distribution, thus allowing the possibility of variable S phase duration times for cells. Several conclusions regarding experimental design considerations are reached. The availability of three labelled cell subgroups comprising cells receiving exactly one of the two thymidine analogues or receiving both thymidine analogues at least doubles the efficiency of the mean S phase duration estimate compared to conventional estimates based on two labelled groups. Increasing the duration between the two thymidine analogue pulses can also dramatically increase the efficiency. The modelling technique was applied to fourteen uveal melanomas from patients who received in vivo injections of two thymidine analogues, bromodeoxyuridine (BrdUrd) and iododeoxyuridine (IdUrd). Counts of labelled cells were consistent with steady-state time homogeneous entry into S phase and nonhomogeneous spatial entry into S phase.

XSPRESS — X-ray signal processing electronics for solid state detectors

With recent improvements in synchrotron sources and X-ray optics great pressures have been placed on detector systems to produce higher count rates and better resolutions. Present high performance 13 element germanium detector systems can give reasonable count rates with good resolution (∼ 104–105 Hz per channel and ∼ 250 eV FWHM @ 55Fe with 0.5 μs shaping time). However, these systems are restricted by limitations in both the detector and in the analogue pulse processing after the detector. With respect to the detector, increasing the number of channels without degrading the energy resolution is a great challenge due to increased crosstalk and capacitance. The analogue pulse processing electronics are significantly limited by the dead time introduced by the shaping amplifier. This dead time causes pulse pile-up at higher rates which leads to non-linearity and poor resolution. This paper describes the XSPRESS system which has been developed at Daresbury Laboratory for the new Wiggler II beamline 16. This system overcomes previous limits in both signal processing and detector fabrication to give great improvements in system performance. The signal processing electronics departs from standard analogue processing techniques and employs sophisticated adaptive digital signal processing hardware to reduce the dead time associated with each event to a minimum. This VME based technology allows us to vastly increase the count rate for each channel yet still retain the ability to gain very good resolution. The detector has been developed through a collaborative agreement with EG & G Ortec and packs an unprecedented 30 germanium crystals into an extremely small area whilst still retaining the energy resolution of smaller arrays. This system has increased throughput rate by an order of magnitude per channel and when all channels are implemented, an increase of at least two orders of magnitude for the whole array should be seen. Data has been taken using this system on the SRS at Daresbury Laboratory and these results will be given along with a detailed explanation of the operation of this system.

Application of Digital Waveform Processing to Proportional counter

In a charge-division type position-sensitive proportional counter (PSPC) with an anode wire of small resistance, a reflected component from an opposite end and thermal noise involved in signals deteriorate the position resolution of the PSPC. A digital waveform processing method was applied to the reduction of these undesirable effects by skillfully utilizing their signal characteristics that can be observed as inversely correlative signals between two-output signals from both sides of the PSPC. The digital waveform processing could improve the position resolution compared to a conventional pulse height processing method with analog filters. When the digital waveform processing was applied to signals of an equivalent circuit simulating the PSPC, the position resolutions defined by the full width at half maximum were improved to about 30% of those of conventional analog pulse processing. In the case of an actual PSPC, the position resolutions by the digital waveform processing were improved by 4–10% as com...

X-ray signal processing electronics for solid state detectors

With recent improvements in synchrotron sources and x-ray optics great pressures have been placed on detector systems to produce higher count rates and better resolutions. Present high performance 13 element germanium detector systems can give reasonable count rates with good resolution (∼104–105 kHz per channel and ∼250 eV FWHM at Fe55 with 0.5 μs shaping time). However, these systems are restricted by limitations in both the detector and in the analog pulse processing after the detector. With respect to the detector, increasing the number of channels without degrading the energy resolution is a great challenge due to increased crosstalk and capacitance. The analog pulse processing electronics are significantly limited by the dead time introduced by the shaping amplifier. This dead time causes pulse pileup at higher rates which leads to nonlinearity and poor resolution. This paper describes the XSPRESS system which has been developed at Daresbury Laboratory for the new Wiggler II beamline 16. This system overcomes previous limits in both signal processing and detector fabrication to give great improvements in system performance. The signal processing electronics departs from standard analog processing techniques and employs sophisticated adaptive digital signal processing hardware to reduce the dead time associated with each event to a minimum. This VME based technology allows us to vastly increase the count rate for each channel yet still retain the ability to gain very good resolution. The detector has been developed through a collaborative agreement with EG&amp;G ORTEC and packs an unprecedented 30 germanium crystals into an extremely small area while still retaining the energy resolution of smaller arrays. This system has increased the throughput rate by an order of magnitude per channel and when all channels are implemented, an increase of at least two orders of magnitude for the whole array should be seen. Data have been taken using this system on the SRS at Daresbury Laboratory and these results will be given along with a detailed explanation of the operation of this system.

Application of Digital Waveform Processing to Position-Sensitive Proportional Counter.

In a charge-division type position-sensitive proportional counter (PSPC) with an anode wire of small resistance, a reflected component from an opposite end and thermal noise involved in signals deteriorate the position resolution of the PSPC. A digital waveform processing method was applied to the reduction of these undesirable effects by skillfully utilizing their signal characteristics that can be observed as inversely correlative signals between two-output signals from both sides of the PSPC. The digital waveform processing could improve the position resolution compared to a conventional pulse height processing method with analog filters. When the digital waveform processing was applied to signals of an equivalent circuit simulating the PSPC, the position resolutions defined by the full width at half maximum were improved to about 30% of those of conventional analog pulse processing. In the case of an actual PSPC, the position resolutions by the digital waveform processing were improved by 4-10% as compared with those of conventional pulse height processing.

Microcalorimeters for broad band high resolution X-ray spectral analysis

A large area microcalorimeter with 95% quantum efficiency at 6 keV has been developed. When fully illuminated, it produces X-ray spectra between 0.5 and 7 keV with an energy resolution of 23 eV. On a smaller, but similar detector, we measure 18 eV. The resolution is obtained at input count rates of 10–50 Hz in real-time with analog pulse processing and thermal pile-up rejection. The detector is incorporated into a compact and portable cryogenic refrigerator system that is ready for use as a tool for analytical spectroscopy.