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Biomedical subjects

V R Singh

Publications and source records attributed to V R Singh.

18 recordsLinked to original sources
PubMed1995

Bacillus licheniformis bacteremia: five cases associated with indwelling central venous catheters.

Bacillus species are being more frequently recognized as pathogens in immunocompromised hosts or in patients with cancer and central venous catheters. Only nine cases of Bacillus licheniformis infection have been reported in the English-language literature since 1966. In a retrospective study we describe six patients and 17 episodes of B. licheniformis bacteremia over a 5-year span. All six patients had either a Hickman or a Broviac catheter in place for more than 3 months. Five of the six patients had multiple clinically significant episodes of bacteremia due to B. licheniformis. The six patients ranged in age from 4 years to 62 years. Two patients had leukemia or lymphoma and three patients had solid tumors, but only one patient was neutropenic. No deaths were related to B. licheniformis bacteremia. B. licheniformis should be considered as a potential pathogen in immunocompromised patients, especially when bacteremia is associated with the presence of long-term central venous catheters. Mortality due to B. licheniformis bacteremia is low, but recurrent bacteremia due to this organism causes significant morbidity and usually necessitates removal of the catheter.

Adolescent↗
PubMed1992

Ultrasonic study of processed milk cream and vegetable oils.

Food systems are complex and inhomogeneous in nature. Ultrasonic propagation velocity in the food systems, in this case processed milk cream and vegetable oils, is studied. Ultrasonic properties of the food systems are similar to those of complex biological tissues. The presence of vegetable oil as an adulterant in the processed milk cream is detected with the help of a double-probe-through-transmission ultrasonic technique. The present study helps to maintain quality control of various food systems, particularly with regard to their adulteration, if any.

Animals↗
PubMed1992

Ultrasonic velocity and attenuation measurement in kidney stones: correlation to constituents and hardness.

In this investigation, ultrasonic parameters of kidney stones are measured, in vitro, using a double probe ultrasonic-through-transmission technique. Due to the complex chemical structure of these stones, a large variation in the values of the ultrasonic parameters is found. A correlation between ultrasonic properties and variation in pathology of the renal calculi is also discussed.

Acoustics↗
PubMed1991

A comparative study of fracture strength, ultrasonic properties and chemical constituents of kidney stones.

Ultrasonic properties of kidney stones were studied with a double-probe-through-transmission technique, the micro hardness was studied using the Viker indentation method and the chemical composition studied using an X-ray technique. The microhardness is found to vary with chemical composition as well as ultrasonic propagation velocity. The comparative results obtained are discussed in detail.

Hardness Tests↗
PubMed1991

Piezoelectric effect in renal calculi.

The piezoelectric effect is investigated for the first time in renal calculi in vitro. The kidney stones are shaped from solid samples as well as from stones crushed into powder and pressed into tablets. Presence of alpha quartz in the renal calculi is investigated by an X-ray technique and the presence of this constituent also helps to explain the piezoelectric effect in the renal calculi. The dielectric and piezoelectric parameters are studied in detail.

Electric Conductivity↗
PubMed1991

Stress-generated electric potential in renal stones due to ultrasound [43.35.Cg, 43.80.Cs, 62.20.Dc].

The presence of renal calculi in the kidney causes discomfort and pain to the patients and so removal of such stones is thus important. These days, nonsurgical and noninvasive techniques are used for this purpose. In this laboratory, an ultrasonic kidney stone disintegrator is being developed. In order to know design parameters for such instrument, various physical and mechanical properties of renal calculi, have been studied. During the course of ultrasonic studies in kidney stones, "stress-generated electric potential" has been observed. The in vitro samples of the kidney stones were obtained from local hospitals in Delhi. The stones were sliced into a regular shape of 1 x 1 cm. An ultrasonic field at 2.5 and 5.5 MHz was applied to the samples normal incidence to one surface. On the two surfaces parallel to the ultrasonic beam, two electrodes were applied and an electric potential was measured across these electrodes. This stress-generated potential was measured with the help of an electrometer, and varied from 0.50 to 3.0 mV and 3.10 to 12.50 mV at the two frequencies, respectively. This investigation shows that the renal calculi exhibit a stress-generated electric voltage due to their piezoelectric property.

Electric Conductivity↗
PubMed1991

Dielectric properties of kidney stones as electro-ceramics.

Dielectric properties of kidney stones in processed form are studied in a frequency range of 1 kHz-10 MHz. The samples under test are in the form of discs of the stones. The dielectric properties are found to be highly dependent on the frequency, and as expected, similar to those of conventional electro-ceramics and other such bio-materials, due to presence of alpha-quartz in the calculi.

Electric Conductivity↗
PubMed1991

Loss of strength in drilled bone in orthopaedic surgery.

It is common practice in orthopaedic surgery to drill holes in bones for the placement of screws. Such holes make the bone weaker compared to an intact one. The loss of strength after drilling holes in the compact bone is studied here.

Animals↗
PubMed1990

A stress wave propagation technique for bone repair study.

The diagnosis of bone fracture and its rate of healing still remains a problem among orthopedic surgeons. An acoustic technique based on stress-wave propagation is developed. The technique is used on laboratory experimental in vitro bones, as well as on in vivo (human) bones, to diagnose a fracture. The rate of healing of the fracture is also studied. The technique developed is quick, economical, reliable, portable, and safe for both the patient and the operator.

Animals↗
PubMed1990

Measurement of ultrasonic velocity and attenuation in bone tumors, in vitro.

Ultrasonic velocity and attenuation are determined in different types of bone tumors by using a double-probe-through-transmission ultrasonic technique. The average values of propagation velocity in different types of tumors are found as 2106, 2304, 2677.5, and 3586 m/s with 1.49%, 1.04%, and 0.74% standard deviation in Giant Cell, Lymphoma, Chondro Sarcoma, and Osteogenic Sarcoma, respectively. Absorption coefficient of ultrasound is found to be minimum as 19.7 dB/cm with 0.002% standard deviation in Lymphoma, and high in Osteochondroma and not measurable with the present setup. A direct technique for the diagnosis and differentiation of various types of tumors can be developed by standardization of the data.

Bone Neoplasms↗
PubMed1989

Ultrasonic studies of gall-bladder stones.

Measurements of ultrasonic speed, attenuation and other derived physical properties of gallstones, in vitro, have been evaluated and reported. A double-probe-contact through-transmission technique was used; the average values of ultrasonic speed and attenuation were found to be 1897 m s-1 and 10.2 dB cm-1, respectively, at 2.5 MHz (the value of speed thus being about 25% higher than that in water or soft biological tissues). The object of the present study was to determine the characteristics of stones to permit the optimization of a disintegrator design.

Bilirubin↗
PubMed1989

Role of natural frequency of bone as a guide for detection of bone fracture healing.

The natural frequency of bone is studied in normal and fractured bones, in vitro as well as in vivo, by recording the outputs of microphone pick-ups, attached at proximal and distal ends to the bone defect. Natural frequency of bone is determined for an optimum output displayed on a cathode ray oscilloscope with respect to different stress wave frequencies. A comparative study of normal and fractured bone in vivo in 25 patients was made to diagnose the size of the fracture and its rate of healing. The natural frequency and intensity of sound in the injured bone was reduced while the output voltage increased with respect to the normal bone. The investigation reports a simple, reliable and rapid technique for the assessment of bone fracture.

Animals↗
PubMed1980

Acoustic power measurement of medical ultrasonic probes using a strain gauge technique.

A new method using a semiconductor strain guage is described for the measurement of the acoustic power output of ultrasonic medical therapy and other probe heads. The acoustic power output of the probe heads is found to be linearly related to the calibrated electrical output of the strain gauge transducer system, as expected theoretically. The instrument developed is inexpensive, portable and easy to operate for the routine measurement of ultrasonic output of the equipment in hospitals.

Calibration↗