An ultrasonic obstacle detector based on phase beamforming principles

A prototype of an ultrasonic obstacle detector developed as a part of a navigation system for blind and visually impaired people is presented. The detector, which employs a single ultrasound source and an array of microphones, determines the distance to the obstacle by measuring time between sending the pulse and receiving the reflected signal. Using the phase beamforming technique, borrowed from hydroacoustics, to process the output signals of microphones, it determines also the direction from which the reflected signal is received, thereby locating the obstacle. The obstacle detector was subjected to a series of tests in order to verify its design and to assess its ability to detect a broad range of obstacles. Presented test results show that most obstacles can be detected and recognized, and that the tested obstacle detector provides complete coverage of the safety zone in front of the user.     

Mammalian Rh/T2/S-glycoprotein ribonuclease family genes: cloning of a human member located in a region of chromosome 6 (6q27) frequently deleted in human malignancies

OBJECTIVE: To implement a low-cost system of transmitting high-quality digital photographs of mutilating extremity injuries using the speed of the Internet. DESIGN: A high-resolution digital camera and simple hardware and software platform are used to take and transmit images via electronic mail. The images are received within minutes by the consultant, and an assessment can be made. RESULTS: A low-cost and high-quality system can easily be implemented. Images can be seen by consultants only a few minutes after they are obtained. The quality of the reproductions is excellent, and they are handled exactly as other photographs. CONCLUSION: This technique can be widely applicable and inexpensive to initiate in any emergency room. It allows rapid assessment of extremity injuries and x-ray images by expert consultants, who can then evaluate the replantation or revascularization potential of extremity trauma cases. This can eliminate unnecessary and often expensive transfer of patients who are not candidates for replantation.     

Detection of human papillomavirus gene sequences in laryngeal tumors and premalignant changes by polymerase chain reaction

Human papillomavirus gene sequences have been detected in a number of malignant and benign tumours. Non-oncogenic types 6 and 11 are etiological factors of benign mucosal tumours. Types 16 and 18 can be detected in malignancies most often but their role in the etiopathogenesis of cancers is still unclear. In our study we examined formalin-fixed and paraffin-embedded archive laryngeal tissues containing squamous cell carcinoma, papilloma and precancerous lesions for the presence of human papillomavirus genes. As a control we also examined tissues harbouring laryngeal nodules which represented the normal larynx in our study. After DNA preparation from the paraffin blocks we performed polymerase chain reaction to detect the DNA of human papillomavirus types 6, 11, 16 and 18. In the squamous cell carcinomas, papillomas and precancerous lesions the presence of human papillomavirus gene sequences was significantly higher than in the control group. To verify the integrity of DNA we also amplified a sequence deriving from the cellular beta-globin gene. Based on the 100% positivity for this gene we declare that the combination of our DNA preparation and polymerase chain reaction is a reliable method for detecting DNA sequences from formalin-fixed and paraffin-embedded tissues.     

Use of the nuclear microprobe at the University of Arizona for the study of heavy metal deposition in rabbit renal tissue

Industrial wastes consigned to disposal sites frequently contain substantial amounts of heavy metals. We have successfully applied proton induced X-ray emission analysis (PIXE) in the conduct of heavy metal (Hg, Cd, Cr, As) toxicity studies using precision cut rabbit renal cortical slices. The large beam diameter (4000 μm) of the proton macroprobe at The University of Arizona Ion Beam Analysis facility allowed an overall concentration of the metal(s) of interest in the samples to be determined, but lacked the ability to resolve point concentrations in the tissue. The ability to locate these areas has now been made available to us with the addition of a rastering microprobe (μ-PIXE) to the facility. Studies now being conducted in our laboratory using this micro-technique include analysis of renal tissue taken from rabbits injected intraperitoneally with HgCl₂, K₂Cr₂O₇, and NaAsO₂. The small beam size (3 μm) and the ability to raster this beam over areas of up to 125 μm × 125 μm has allowed regional mapping of endogenous and non-endogenous metal concentrations and revealed trends in heavy metal deposition in in vivo treated renal tissue, significantly increasing the amount of information obtained from these animal studies using PIXE alone. The combination of small beam size, high resolution, and multi-element detection makes μ-PIXE a powerful tool for investigating the impact of non-endogenous metals on the kidney.     

A packet delay analysis for cellular digital packet data

We formulate and analyze a model of voice and data burst traffic for cellular digital packet data (CDPD). To develop a tractible model, we make some reasonable simplifying assumptions to model the voice traffic and one of the logical CDPD channels as an M/M/1 queue in a random environment. Rather than explicitly solve the resulting matrix quadratic equation, we develop an asymptotic analysis that gives us simple approximate formulas (with error bounds) for many performance measures of interest. In particular, one metric that we highlight comes from using our approximate mean data burst delay formula to characterize the performance of a set of interacting logical CDPD channels. We do so by describing it in terms of an equivalent number of independent, dedicated CDPD channels, We can use this metric to suggest what the optimal number of logical CDPD channels for a given system should be     

Numerical simulation of a silicon-on-insulator waveguideFabry-Perot interferometer for intensity light modulators at 1.3 μm

We present a new silicon-on-insulator (SOI) integrated optics structure to be used as an intensity light modulator at 1.3 μm. The device consists of a waveguide Fabry-Perot interferometer. In association with a grating coupler this device could function as a spatial light modulator or a reflective-mode modulator. The Fabry-Perot reflectivity is tuned by free-carrier injection from a forward-biased lateral P⁺/N^-/N⁺ diode. Consequently, the reflected back guided-mode has an intensity that is a function of the effective index modulation in the central waveguide of the Fabry-Perot. Our numerical simulation reveals that such a structure could function for current densities not exceeding 500 A/cm² with a cutoff frequency of 100 MHz. This new type of device is compatible with the mature silicon technology and could replace in applications the standard liquid-crystal spatial light modulators or for fiber-to-the-home intensity modulators     

Generalized Tunstall codes for sources with memory

Tunstall codes are variable-to-fixed length codes that maximize the expected number of source letters per dictionary string for discrete, memoryless sources. We analyze a generalization of Tunstall coding to sources with memory and demonstrate that as the dictionary size increases, the number of code letters per source symbol comes arbitrarily close to the minimum among all variable-to-fixed length codes of the same size. We also find the asymptotic relationship between the dictionary size and the average length of a dictionary entry     

Scattering center parameterization of wide-angle backscattered datausing adaptive Gaussian representation

We present a scattering center extraction algorithm to parameterize the backscattered data from complex targets collected over large angular apertures. This parameterization is based on a scattering center model of the target, but includes an aspect-dependent amplitude function for each scattering center. A two-dimensional (2-D) adaptive Gaussian representation (AGR) algorithm is used to extract the position and the amplitude function associated with each scattering center. The algorithm is tested with data generated by the Xpatch radar simulation code as well as chamber measurement data. The results show that a very good compression ratio can be achieved, resulting in a compact scattering center model of the target. Once such model is available, we can easily reconstruct range profiles and ISAR images at any aspect on the same plane with good accuracy     

Performance and buffering requirements of Internet protocols overATM ABR and UBR services

ATM networks are quickly being adopted as backbones over various parts of the Internet. This article studies the dynamics and performance of the TCP/IP protocol over the ABR and UBR services of ATM networks. Specifically the buffering requirements in the ATM switches as well as the ATM edge devices. It is shown that with a good switch algorithm, ABR pushes congestion to the edges of the ATM network while UBR leaves it inside the ATM portion. As a result, the switch ABR buffer requirement for zero-packet-loss high-throughput TCP transmission is a sublinear function of the number of TCP connections