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At least 775 records · Page 43Linked to original sources
PubMed2000

Charge capacity limitations of radio frequency ion guides in their use for improved ion accumulation and trapping in mass spectrometry.

The use of radio frequency (rf) ion guides as "linear" two-dimensional ion traps and ion guides for ion storage and accumulation, respectively, is becoming increasingly important for realizing improved sensitivity in mass spectrometry. Analytical relationships describing the ion accumulation operation mode of rf ion guides are reported. Comparisons are made between the rf quadrupole ion guide, higher-order rf multipoles and rf stacked ring ion guides, in terms of the charge capacity limitations due to the instability of ions, rf focusing efficiency limits, and effects due to rf ion heating (i.e., collisional activation due to rf oscillations of ions). Analytical relations for the stored charge quantity are derived in the low ion energy approximation, which is shown to be reasonable for the systems considered. The ion density spatial distribution is derived, an exponential form of which proved to provide a good approximation for high-order rf multipoles and stacked ring rf ion guides. The limit on the stored charge dependence upon rf is shown to be directly related to the thermal dissociation thresholds for the ions being studied; the limitation is weaker for higher-order multipoles and stacked ring ion guides. These results suggest that rf quadrupoles provide an optimum configuration when accumulation of a moderate ion density is sufficient (below 10(9) elementary charges/m). Alternatively, accumulation of an appreciable density for more fragile species, such as noncovalent complexes, may be realized using higher-order multipoles and stacked ring ion guides.

Ions↗
PubMed2002

Continuous real-time monitoring of phosphine concentrations in air using electrochemical detectors interfaced by radio telemetry.

This work involves the novel use of a radio telemetry-based system that continuously monitors phosphine using two different types of electrochemical detectors (ECD/RT). The ECD/RT units were used to monitor phosphine inside and at varying distances from large tobacco storage warehouses. A master controller unit transferred the data to a personal computer that received and displayed the data. Supervisory control and data acquisition software assimilated the data from each ECD/RT unit, displayed and updated it as new transmissions were received, and stored the data in secure databases. Phosphine concentrations outside five warehouses simultaneously under fumigation and at the facility boundaries were <0.3 parts per million (ppm). Phosphine levels ranged from 0 to 580 ppm inside sealed warehouses. A comparison was made between the data collected at an ECD/RT unit approximately 4 m downwind of a sealed warehouse and a colorimetric tube at the same location. The final phosphine concentration from the colorimetric method was 0.05 ppm and the average over the 20-minute collection period for the ECD/RT was 0.13 ppm. This system allows for continuous, remote monitoring around warehouses under fumigation and superior time resolution allowing timely response to fugitive emissions of phosphine.

Air Pollution, Indoor↗
PubMed1987

The main source of radio emission from the magnetosphere of Uranus.

Observations of kilometric radiation from Uranus made with the planetary radio astronomy experiment on the Voyager 2 spacecraft are presented and discussed. Similarities between the auroral kilometric radiation from Earth and the observed Uranus emission are pointed out. A geometrical beaming model is developed in which a single distributed source is located above the darkside auroral region and emits in the extraordinary mode by the cyclotron maser process. The model can account for nearly all the Uranian kilometric radiation from the high-frequency limit near 850 kHz down to about 150 kHz and for much of it down to the lower limit of 20 kHz.

Astronomical Phenomena↗
PubMed1999

Multi-electrode radio frequency resurfacing of ex vivo human skin.

BACKGROUND: A novel radio frequency multi-electrode surgical (MES) device has produced minimal residual thermal collagen damage (RTCD) and rapid healing in treating articular cartilage. OBJECTIVE: To assess the immediate tissue effects of the MES device on human skin. METHODS: Specimens of ex vivo human skin were subjected to 1 to 3 passes of the device at 3 voltage settings, then processed for routine and polarized light microscopy. The degree of tissue ablation, amount of RTCD, and level of follicular injury were assessed. RESULTS: Epidermal ablation did not occur; epidermal removal correlated with manual debridement after the first passes. Dermal ablation was not readily discernable even after 2 or 3 passes. The thickness of RTCD tended to increase with increased pass number. The mean thickness of this zone of damaged collagen measured 24-53 micro after 1, 63-83 micro after 2, and 80-97 micro after 3 passes, respectively. For a given number of passes, the thickness of the zone of RTCD did not consistently change with increasing voltage applied (86, 108, and 139 V). The small number of samples did not enable meaningful statistical analysis of these observations. In samples with pilosebaceous units, the electrosurgical keratinocyte injury extended down the follicular epithelium, but never beyond the level of the infundibulum. CONCLUSIONS: These findings suggest the MES device produces immediate tissue effects favorable for effective cutaneous resurfacing and rapid postoperative wound healing.

Arm↗
PubMed1976

[Influence of radio and television sets on implanted cardiac pacemakers (author's transl)].

Investigations done on implanted pacemakers with a low threshold against extraneous signals and in-vitro tests under suitable conditions both showed that pacemaker wearers may go near television and accessories such as ultrsound distant control or flexless infrared ear phones without any danger. Radio and television sets are fitted to an increasing degree with electronic sensor switches which initiate various functions after a slight touch. This satisfies present regulations of German Electrical Engineers concerning permitted contact currents. However, pacemaker patients can cause impulse defects by use of sensor switches provided the contact current is less than 25 muA. Sensor technique will in the future be introduced for everyday use on a large scale. Therefore, pacemaker patients should be alerted to the possibilities of an influence, and industry should be made to reduce contact currents in sensors to values below 20 muA.

Infrared Rays↗
PubMed2003

[Radio-frequency-ablation (RFA) with wet electrodes in the treatment of primary and secondary liver tumours].

INTRODUCTION: The majority of patients with primary and secondary tumours of the liver cannot be treated curatively by surgery. The treatment of these patients with radio-frequency thermoablation using perfused needle applicators (wet electrodes) was evaluated in a feasibility study. METHOD: Patients with primary and secondary tumours of the liver and contraindications against surgery or LTX were included into the feasibility study. RFA was performed percutaneously under ultrasound guidance. The patients were followed up sonographically and by computed tomography. RESULTS: 20 patients (9 male, 11 female) with 35 lesions were treated with RFA. 12 patients (22 tumour locations) suffered from HCC and 8 patients (13 tumour masses) had liver metastases (colorectal, breast, pancreas, carcinoid). The median age was 65.6 years (36 to 83 years). The median tumour size was 33.5 mm. 59 RFTA applications (1.7 applications per tumour mass) were performed. The mean duration of RFTA per patient was 16.2 minutes. During the procedure isotonic saline was injected at a mean flow rate of 6.63 ml/min. All patients received local anaesthesia. In 33 sessions an additional analgosedation was necessary (average dose 63.8 mg Pethidine and 1.4 mg Midazolam). In 2 cases a reduction of the haemoglobin level, occurred, necessitating a blood transfusion. 3/4 of the treated metastases could be eradicated completely. Within a median follow-up of 145 days no intrahepatic local recurrence but 4 distant metastases occurred. 2/3 of the treated HCC could initially be brought into complete remission (CR). After a median follow-up of 329 days 5 of the 8 initially successfully treated patients with HCC were still in complete remission. In 3 cases an intrahepatic local recurrence developed. CONCLUSION: RFA with wet electrodes is a safe, effective and inexpensive treatment for primary and secondary tumours of the liver, measuring less than 4 cm in diameter.

Adult↗
PubMed2005

Genital self-mutilation by radio-frequency in a male-to-female transsexual.

We report the case of a male-to-female transgender individual who inflicted radio-frequency injuries to her testicles in an attempt to damage them. Important consideration should be given by medical practitioners when they are faced with an individual who believes he or she is transgender. A sympathetic approach should be taken and a referral made to a clinician or service experienced in dealing with transgender patients.

Adult↗
PubMed2001

Does humor in radio advertising affect recognition of novel product brand names?

The authors proposed that item selection during shopping is based on brand name recognition rather than recall. College students rated advertisements and news stories of a simulated radio program for level of amusement (orienting activity) before participating in a surprise recognition test. Humor level of the advertisements was varied systematically, and content was controlled. According to signal detection analysis, humor did not affect the strength of recognition memory for brand names (nonsense units). However, brand names and product types were significantly more likely to be associated when appearing in humorous advertisements than in nonhumorous advertisements. The results are compared with prior findings concerning humor and recall.

Advertising↗
PubMed1988

Physiological effects of 2.8 GHz radio-frequency radiation: a comparison of pulsed and continuous-wave radiation.

Ketamine-anesthetized female Sprague-Dawley rats were exposed individually to far-field 2.8 GHz continuous wave (CW) and pulsed (2 microseconds, 500 pps) radio-frequency radiation (RFR) at average power densities of 30, 45, and 60 mW/cm2 [specific absorption rates (SAR) of 8.4, 12.6, and 16.8 W/kg, respectively] and to pulsed RFR at 75 mW/cm2 (SAR = 21 W/kg). Intermittent exposures were conducted to repeatedly increase colonic temperature from 38.5 to 39.5 degrees C. Colonic, tympanic, and subcutaneous temperatures, electrocardiogram, respiratory rate, and arterial blood pressure were continuously monitored and recorded. The time required to effect a 1 degree C colonic temperature increase varied inversely with the average power density used during exposure; however, the rate of cooling was independent of the heating rate. During pulsed irradiation, heart rate increased significantly at average power densities above 30 mW/cm2; heart rate increase during CW exposure was not significant. Heart rate returned to baseline when exposure was discontinued. Blood pressure and respiratory rate did not significantly change during irradiation. Pulsed RFR exposure caused a significantly greater increase in subcutaneous and tympanic temperatures than did CW exposure; however, no significant difference was noted between the effects of CW or pulsed RFR upon the rats' colonic temperature responses (heating and cooling time), heart rate, blood pressure, and respiratory rate.

Animals↗
PubMed1988

Long-term study of 435 MHz radio-frequency radiation on blood-borne end points in cannulated rats. Part I: Engineering considerations.

To study the effects of exposure to long-term, low-level radio-frequency radiation (RFR) on various physiological systems in a large population of rodents, a complete exposure facility was designed and constructed at the Georgia Institute of Technology. The major components of the facility included a set of circular, stacked, parallel-plate waveguides fed by slotted-cylinder antennas. The waveguides provided a TE10 mode, horizontally polarized field in which the maximal power density occurred midway between the parallel plates. The feed antenna and the parallel-plate waveguides generated a field that radiated outward and was uniform in the azimuthal plane. Thus, animals arrayed along the periphery of the plates were exposed to a uniform 1.0 mW/cm2 field (1.0 microsecond pulse width, 1 kHz pulse repetition rate, 435 MHz carrier). The facility transmitter provided four channels of 435 MHz RFR at 200 W average (continuous wave) or 5 kW peak (pulsed-wave) power; in addition, the transmitter outputs could be combined into a single channel capable of energizing one tier of the stacked parallel-plate waveguide system at 800 W continuous wave or at 16 kW of pulsed waves. To individually house the 200 rodents involved in the study, both biological and engineering criteria were examined and used to design and construct special Plexiglas cages.

Animal Husbandry↗
PubMed1988

Long-term study of 435 MHz radio-frequency radiation on blood-borne end points in cannulated rats. Part II: methods, results, and summary.

This study investigated the effects of long-term, low-level exposure to radio-frequency radiation (RFR) on various physiological systems in a large rodent population. Two hundred adult male white rats with chronically implanted aortic cannulas were randomly divided into two groups. Animals in the first group were exposed to the low-level RFR environment for approximately 22 hours daily, seven days a week, for six months. Depending on animal orientation within the home cage (all animals singly caged) the estimated whole-body specific absorption rate (SAR) ranged from 0.04 to 0.4 W/kg. The estimated mean whole-body SAR ranged from 0.3 W/kg (medium-sized rats) to 0.35 W/kg (large-sized rats). A second, sham-exposure group was maintained under identical conditions, but were not radiated. Microsamples of blood were withdrawn on a cyclic schedule from the unanesthetized and unrestrained rats. The blood samples were assayed for plasma adrenocorticotropin (ACTH), plasma corticosterone, plasma prolactin, plasma catecholamines (norepinephrine, epinephrine, and dopamine), hematological end points (hematocrit ratio, complete red blood cell count, complete white blood cell count, and a differential count of neutrophils, eosinophils, and monocytes), and cardiovascular end points (heart rate and mean arterial blood pressure). Analysis of the results showed no significant RFR-induced differences in these end points when the RFR-exposed group was compared to the sham-exposed group. Chronic exposure to the low-level, pulsed field resulted in no adverse effects on animal health, as measured by the spectrum of blood-borne end points.

Adrenocorticotropic Hormone↗
PubMed2001

European regulations of the radio spectrum, ISM use and safety.

In Europe, many standards dealing with equipment electromagnetic compatibility (EMC) are threatening the ISM use of the radio spectrum. The basis and the shortcomings of the standards are discussed and compared with the actual electromagnetic environment. The standards for equipment are too strict involving higher investment costs. High frequency and microwave power applications are therefore likely to slow down. Guidelines and standards for protection of human exposure to electromagnetic fields (EMF) are too conservative and have no reference to ISM applications. Only a leakage standard for the domestic microwave oven and similar equipment exist. Some recommendations are presented for improvement.

Consumer Product Safety↗
PubMed2004

Electrical properties of soils at ism radio frequencies, from 1 to 40 MHz.

Soil electrical properties, conductivity and permittivity, vary with moisture content and temperature. The goal of the work was to generate working correlative functions of the electrical properties of soil over practical ISM radio fJequencies (6.78 to 40.68 MHz) from the Kirtland Air Force Base RF soil remediation project, and its constituent soil types, to facilitate numerical model studies. Correlates were developed to facilitate numerical model temperature and moisture dependence of the electrical properties. Measurements were made in continuous spectra from 1 to 40 MHz for varying moisture content and temperatures of sand, kaolinite, Austin landfill clay, sandy loam and Kirtland Air Force Base soil samples. The measurements were conducted in a 1 5/8" coaxial sample holder with flush mounted center conductor. Impedance data were collected with a Hewlett-Packard 4194A Impedance Analyzer from which calculations of permittivity were made. In general, the relative permittivity and effective loss factor are sensitive functions of water content and temperature.

Electric Impedance↗
PubMedDate not supplied

A paid radio advertising campaign to promote parent-child communication about alcohol.

This study assessed the impact of a paid radio commercial designed to promote parent-child communication about alcohol use and sponsored by the Bureau of Substance Abuse Services, Massachusetts Department of Public Health. A random-digit-dial telephone survey of parents or guardians of children ages 10-17 years was conducted after a four-week advertising flight. Respondents with unassisted recall of the commercial more often disagreed that parent-child discussion is useful only if children have begun to experiment with alcohol, and more often reported having three or more parent-child discussions about alcohol compared to those who did not recall the commercial. Findings suggest the potential benefit of paid media campaigns to encourage parents to talk with their children about alcohol.

Adolescent↗
PubMed2001

Strategy for increased efficiency of transfection in human cell lines using radio frequency electroporation.

Traditional electroporation devices use direct current electric fields to stimulate the uptake of oligonucleotides, plasmids, short peptides, and proteins into a variety of cell types. A variation of this widely used technique is now available which relies on radio frequency (RF) electrical pulses. This oscillating type of electrical field reportedly elicits greater uptake of plasmid DNA across the plasma membrane. We evaluated a protocol for RF electroporation of the a human embryonic kidney cell line and a Burkitt's lymphoma (BL) cell line for effeciency of transfection by RF electroporation. The plasmid EGFP, which codes for the widely used fusion protein, enhanced green fluorescent protein (EGFP), was used as a reporter of plasmid uptake after transfections. Transfection efficiency consistently increased approximately 30% from that typically obtained with conventional DC type electroporation and was accompanied by greater survivability of cells. Additionally, in some instances, percent transfection efficiency increased to over 70%. Thus, RF electroporation represents an improved methodology for transfection of human cell lines. Moreover, the RF protocol is simple to incorporate in laboratories already utilizing conventional electroporation devices and techniques.

Burkitt Lymphoma↗
PubMed1988

An electrodeless measuring technique for determining conductivity of biological tissues at radio frequencies.

An electrodeless measuring technique for determining the conductivity of biological tissues at radio frequencies is described. The technique is based on measuring magnetic power dissipation in a conducting sample using a tuned circuit when the sample is immersed in a time-varying magnetic field. Theory regarding the measurements is presented. Consideration for coil design is given. Coil construction and measurement techniques are described in detail. The technique has three advantages: errors resulting from electrode lead inductance are completely removed; contacts between tissue surfaces and electrode surfaces are not needed; and maintaining water content and concentration of pH solution inside the tissues during measurements becomes easily facilitated. With the technique, conductivity values of dog kidney at room temperature were obtained in good agreement with previous work.

Animals↗
PubMed2005

Comparison of radio frequency energy absorption in ear and eye region of children and adults at 900, 1800 and 2450 MHz.

The increasing use of mobile communication devices, especially mobile phones by children, has triggered discussions on whether there is a larger radio frequency (RF) energy absorption in the heads of children compared to that of adults. The objective of this study was to clarify possible differences in RF energy absorption in the head region of children and adults using computational techniques. Using the finite-difference time-domain (FDTD) computational method, a set of specific absorption rate (SAR) calculations were performed for anatomically correct adult and child head models. A half-wave dipole was used as an exposure source at 900, 1800 and 2450 MHz frequencies. The ear and eye regions were studied representing realistic exposure scenarios to current and upcoming mobile wireless communication devices. The differences in absorption were compared with the maximum energy absorption of the head model. Four magnetic resonance imaging (MRI) based head models, one female, one adult, two child head models, aged 3 and 7 years, were used. The head models greatly differ from each other in terms of size, external shape and the internal anatomy. The same tissue dielectric parameters were applied for all models. The analyses suggest that the SAR difference between adults and children is more likely caused by the general differences in the head anatomy and geometry of the individuals rather than age. It seems that the external shape of the head and the distribution of different tissues within the head play a significant role in the RF energy absorption.

Absorption↗