Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RADIO”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed2005

Radio frequency versus susceptibility effects of small conductive implants--a systematic MRI study on aneurysm clips at 1.5 and 3 T.

PURPOSE: Metallic implants cause enlarged artifacts in magnetic resonance (MR) images at higher magnetic fields, B0, due to their magnetic susceptibility. Interactions of conductive material with radio frequency (RF) pulses also change for higher field strengths, B0, due to the frequency dependence of resonance conditions. Systematic measurements on commercial aneurysm clips and simplified copper models were performed in order to investigate both phenomena at 1.5 and 3 T. MATERIALS AND METHODS: Six different commercial aneurysm clips made of titanium, straight copper wires and bent copper models were examined in Gd-DTPA-doped water. RF-related effects were measured by adapted 2D and 3D spin-echo sequences. For reliable differentiation from susceptibility-related effects, variable transmitter voltages were applied. In addition, RF-induced heating was controlled by an infrared (IR) camera. RESULTS: At 3 T, a significant RF-induced electric response could be demonstrated for the copper samples and more moderate for one of the commercial clips, dependent on the geometrical structure determining possible resonant RF coupling. Related RF effects could be distinguished from susceptibility artifacts: a signal enhancement at reduced transmitter voltages indicated locally amplified B1-field amplitudes. No significant heating effect could be measured by IR measurements. CONCLUSION: MR imaging was used to analyze possible RF-induced effects. At 3 T, resonant RF coupling even of small metallic implants has to be considered carefully. Despite a local enhancement of the RF amplitude, no significant RF-induced heating inside the surrounding fluid was found. A direct thermal endangering of patients seems to be unlikely, but extremely high B1-field amplitudes might occur adjacent to the metallic surface with potential nonthermal affection of tissue.

Artifacts↗
PubMed2005

Hsp70 expression and free radical release after exposure to non-thermal radio-frequency electromagnetic fields and ultrafine particles in human Mono Mac 6 cells.

The contemporary urban environment has become increasingly complex in its composition, leading to discussions regarding possible novel health effects. Two factors that recently have received considerable attention are ultrafine particles (UFP; <0.1 microm) produced by combustion processes and emissions from wireless communication devices like mobile phones that emit in the radio-frequency (RF) part of the spectrum. Several studies have shown biological effects of both these exposures in various cell systems. Here we investigate if exposure to UFP (12-14 nm, 100 microg/ml) and RF-electromagnetic fields (EMF; 2 W/kg specific absorption rate (SAR); continuous wave (CW) or modulated (217Hz or GSM-nonDTX)), alone or in combination influences levels of the superoxide radical anion or the stress protein heat-shock protein (Hsp70) in the human monocyte cell line Mono Mac 6. Heat treatment (42-43 degrees C, 1h) was used as positive control for both stress reaction and for heat development in the RF exposure setup. Our results clearly show that Mono Mac 6 cells are capable to internalise UFP, and that this phagocytic activity is connected to an increased release of free radicals. This increase (40-45% above negative control) is stronger than the effect of heat treatment. On the other hand, none of the employed RF exposures showed any effects on free radical levels. Co-exposure of RF and UFP did not potentiate the UFP effect either. Our investigations showed a significantly increased Hsp70 expression level by heat treatment in a time-dependent manner, whereas UFP, RF, or UFP+RF were without any effect. Therefore, we conclude that in the investigated Mono Mac 6 cells, RF exposure alone or in combination with UFP cannot influence stress-related responses.

Blotting, Western↗
PubMed2001

Miniature radio-frequency mobility analyzer as a gas chromatographic detector for oxygen-containing volatile organic compounds, pheromones and other insect attractants.

A high electric field, radio-frequency ion mobility spectrometry (RF-IMS) analyzer was used as a small detector in gas chromatographic separations of mixtures of volatile organic compounds including alcohols, aldehydes, esters, ethers, pheromones, and other chemical attractants for insects. The detector was equipped with a 2 mCi 63Ni ion source and the drift region for ion characterization was 5 mm wide, 15 mm long and 0.5 mm high. The rate of scanning for the compensation voltages was 60 V s(-1) and permitted four to six scans to be obtained across a capillary chromatographic elution profile for each component. The RF-IMS scans were characteristic of a compound and provided a second dimension of chemical identity to chromatographic retention adding specificity in instances of co-elution. Limits of detection were 1.6-55 x 10(-11) g with an average detection limit for all chemicals of 9.4 x 10(-11) g. Response to mass was linear from 2-50 x 10(-10) g with an average sensitivity of 4 pA ng(-1). Separations of pheromones and chemical attractants for insects illustrated the distinct patterns obtained from gas chromatography with RF-IMS scans in real time and suggest an analytical utility of the RF-IMS as a small, advanced detector for on-site gas chromatographs.

Chromatography, Gas↗
PubMed2004

Radio frequency radiation effects on protein kinase C activity in rats' brain.

The present work describes the effect of amplitude modulated radio frequency (rf) radiation (112 MHz amplitude-modulated at 16 Hz) on calcium-dependent protein kinase C (PKC) activity on developing rat brain. Thirty-five days old Wistar rats were used for this study. The rats were exposed 2 h per day for 35 days at a power density of 1.0 mW/cm2 (SAR = 1.48 W/kg). After exposure, rats were sacrificed and PKC was determined in whole brain, hippocampus and whole brain minus hippocampus separately. A significant decrease in the enzyme level was observed in the exposed group as compared to the sham exposed group. These results indicate that this type of radiation could affect membrane bound enzymes associated with cell signaling, proliferation and differentiation. This may also suggest an affect on the behavior of chronically exposed rats.

Animals↗
PubMed1995

Prehospital classification combined with an in-hospital trauma radio system response reduces cost and duration of evaluation of the injured patient.

BACKGROUND: This study was undertaken to determine whether a prehospital trauma classification system (PHTCS) in combination with an in-hospital trauma radio system response (IHTRSR) impacts emergency care of the injured patient. METHODS: In 1991 our trauma center used no prehospital trauma classification system. A PHTCS was implemented in 1992, and in 1993 the PHTCS was integrated with an IHTRSR: RESULTS: Implementation of the PHTCS and IHTRSR resulted in a significant reduction in the time required for initial evaluation of the trauma patient with an associated reduction in cost. Reduction in time of the initial trauma evaluation was noted in both adult and pediatric populations, in patients with a blunt mechanism of injury, and in the injured patients posing the greatest strain to health care resources. CONCLUSIONS: Integration of a PHTCS with an IHTRSR has a significant impact on the cost and time of emergency treatment of the trauma victim with no adverse effect on patient outcome. Use of an integrated trauma response provides cost-effective and expeditious care of the injured patient and should be considered in trauma system development.

Adolescent↗
PubMed2002

Soft tissue response to microtextured silicone and poly-L-lactic acid implants: fibronectin pre-coating vs. radio-frequency glow discharge treatment.

From in vitro studies it is known that a plasma-treatment can enhance cell spreading. Similar effects can be observed after pretreatment of the surface with a protein coating, to mediate cell adhesion. The aim of the current study was to evaluate the in vivo effects of these surface modifications, in a three-month experiment in a goat model. We made silicone and poly-L-lactic acid implants with double-sided parallel micro-grooves (depth 1.0 microm, width 10.0 microm), a random surface roughness, or a smooth surface. Implants either received a radio-frequency glow discharge (RFGD) treatment, a fibronectin (Fn) pre-coating, or no pre-treatment. Subsequently, they were inserted into subcutaneous pockets created on the flanks of goats for 1, 3 or 12 weeks. Histological analysis showed that a fibrous tissue capsule had formed around all implants. Histomorphometrical analysis was performed on capsule thickness, capsule quality and the implant-tissue interface quality. Fn-treated surfaces showed a considerable early inflammatory reaction. Besides this, RFGD treatment or Fn pre-coating did not further influence any of the measured parameters. In conclusion, pre-treatment of polymer implant surfaces with Fn or RFGD treatment did not significantly influence tissue reaction around implants with micro-grooved, roughened or smooth surfaces.

Animals↗
PubMed2003

Radio frequency (RF) suspension plasma sprayed ultra-fine hydroxyapatite (HA)/zirconia composite powders.

Ultra-fine hydroxyapatite (HA)/ZrO(2) composite powders was synthesised by radio frequency (RF) induction suspension plasma spray. A wet suspension of HA/ZrO(2) was employed as feedstock. The suspension was injected axially into the RF plasma to produce the nano-composite powders, which were subsequently accumulated in cyclone collectors. The particle size and morphology was resolved by using the Zeta potential nano-particle size analyser, scanning electron microscopy, transmission electron microscopy, field emission microscopy techniques. The phase composition, phase concentration, and, molecular structure of the powders were characterised using differential scanning calorimetry, Fourier transform infra-red and X-ray diffractometry with quantitative phase analysis empowered by the Rietveld method. Results indicated that nano-size, spherical HA/ZrO(2) composite powders were produced with varying morphological features that depend on the thermal treatment. Calcium zirconate (CaZrO(3)) was produced as a byproduct whose biocompatibility is not well documented. Results also showed that the HA decomposed into alpha and beta-TCP due to decreasing Ca/P ratio with the formation of CaZrO(3).

Bone Substitutes↗
PubMed1998

Measurements of behavior in the naked mole-rat after intraperitoneal implantation of a radio-telemetry system.

The naked mole-rat (Heterocephalus glaber) is a unique fossorial mammal that is eusocial, object blind, and virtually poikilothermic. This animal is an ideal model to examine questions pertaining to the thermoregulatory aspects of sleep/wake cycles and other circadian events. However, the monitoring of mammalian sleep usually involves implanting permanent electrodes into the skull which are linked to a counter-weighted cable apparatus. This is not a viable option for H. glaber because of the tunneled environments and sensitive social milieu. Instead, to monitor sleep, core temperature, and activity we have utilized intraperitoneal telemetry, a technique that transmits biopotential signals by radio waves. Here we describe the surgical procedure used to implant the device, the anesthesia technique developed, and the social reintroduction method devised for this novel animal model.

Anesthesiology↗
PubMed2003

An application system for automation of constant-time radio frequency electron paramagnetic resonance imaging.

A Windows based application system for data collection, Fourier reconstruction and analysis of pure phase encoded constant-time radio frequency electron paramagnetic resonance (EPR) images, is described. The graphical user interface (GUI) of the system was written in MATLAB version 5.0, using its built-in GUI utilities. Design considerations of the application system included speed, flexibility and user-friendly data display and analysis. To maximize the speed of image data collection, MATLAB's built-in C interface system, MEX was not used for data collection. Instead, MATLAB programs call the C programs from the DOS prompt directly, based on the data collection parameters entered through the GUI. Computational procedures included various digital signal-processing steps such as filtering, interpolation etc. for the Fourier reconstruction of 2D, and 3D EPR images from the pure phase encoded data. Examples of 2D images illustrating the performance of the system are presented. Although the application system has been developed for the specific purpose of EPR imaging, it can easily be adapted to other areas such as magnetic resonance microscopy as well.

Electron Spin Resonance Spectroscopy↗
PubMed1981

A method for reviewing radio-telemetry paramedic calls.

A method is presented for reviewing the taped radio-telemetry records of paramedic calls managed by hospital-based emergency medicine residents. All paramedic calls to the LAC/USC base station are reviewed by an emergency medicine resident using a special tape review form which focuses on communication skills, initial paramedic field assessment, sense of urgency of the case, and the completeness of the filed report. Additional emphasis is placed on the base station physician's interpretation of the field presentation and his choice of therapy. Tapes demonstrating particular skills or pitfalls in prehospital management are selected for monthly tape review conferences. Such conferences provide a method by which each side of the prehospital care team can perceive the position of the other, encouraging physicians and paramedics to enhance their respective roles in providing effective prehospital emergency care.

Allied Health Personnel↗
PubMed1998

Radio and the commodification of natural medicine in Ecuador.

This paper explores the discourse that is being created around medical commodities in one Ecuadorian city in an effort to understand how desire for new medical products is generated and sustained. Commercial natural medicine, which includes vitamins, herbal remedies and tonics is a relatively new addition to the medical marketplace in Ecuador, yet the popularity of these products seems to be growing rapidly. Much of the success of natural medicines is due to promotional campaigns, most notably radio programs, that emphasize and manipulate, important cultural themes about the body, identity, morality and social success. Although on the surface natural medicine seems to be creating a radically new discourse about the body and illness causation, that discourse ultimately serves only to reinforce the unequal social relations associated with capitalist marketplaces.

Advertising↗
PubMedDate not supplied

Thalamo-cortical interactions modeled by weakly connected oscillators: could the brain use FM radio principles?

We consider all models of the thalamo-cortical system that satisfy the following two assumptions: (1) each cortical column is an autonomous oscillator; (2) connections between cortical columns and the thalamus are weak. Our goal is to deduce from these assumptions general principles of thalamo-cortical interactions that are independent of the equations describing the system. We find that the existence of synaptic connections between any two cortical columns does not guarantee that the columns interact: They interact only when there is a certain nearly resonant relation between their frequencies, which implies that the interactions are frequency modulated (FM). When the resonance relation holds, the cortical columns interact through phase modulations. Thus, communications between weakly connected cortical oscillators employ a principle similar to that in FM radio: The frequency of oscillation encodes the channel of communication, while the information is transmitted via phase modulations. If the thalamic input has an appropriate frequency, then it can dynamically link any two cortical columns, even those that have non-resonant frequencies and would otherwise be unlinked. Thus, by adjusting its temporal activity, the thalamus has control over information processing taking place in the cortex. Our results suggest that the mean firing rate (frequency) of periodically spiking neuron does not carry any information other than identifying a channel of communication. Information (i.e. neural code) is carried through modulations of interspike intervals.

Cerebral Cortex↗
PubMed1992

Hepatic ablation with use of radio-frequency electrocautery in the animal model.

The potential of percutaneous radio-frequency (RF) electrocautery hepatic ablation was evaluated in the animal model. RF hepatic ablation was performed under ultrasound (US) guidance in the liver of 10 swine with use of a specifically designed needle. The needle was placed through the liver capsule, and ablation was performed after isolating the liver at laparotomy. Animals were killed immediately (n = 4), at 1 week (n = 1), 2 weeks (n = 3), or at 5 weeks (n = 2). The US findings were correlated with the pathologic results in the animal livers. RF hepatic ablation was successfully performed in the animal model without complications. Lesions in the animal livers were typically 1 x 2 cm, which initially appeared highly echogenic on US scans. These images corresponded to an area of hepatic necrosis. The lesions became less echogenic shortly after initial treatment but could still be visualized with US at 5 weeks. At histologic study at 5 weeks, the treated livers showed central debris, a larger area of necrotic liver, and a zone of granulation tissue surrounded by a fibrotic capsule. No complications were encountered. RF hepatic ablation shows future promise in treatment of hepatic neoplasms.

Animals↗
PubMed1999

The incidence of radio-frequency impulsive noise within hospital buildings: initial measurements in the 450 MHz band.

This paper reports on the incidence and level of man-made electrical impulse noise capable of causing interference to low-power, ASK and FSK radio biotelemetry links. Measurements were made at two acute hospitals, one in a residential area of Belfast, Northern Ireland and the other in an industrial part of Berlin, Germany. Monitoring was effected in the 450 MHz band using a communications receiver with its AGC line disabled and AM-detector AM output fed to a PC-based logger. The RF bandwidth was 20 kHz and a rotatable folded-dipole receiving antenna was used. Seven-day impulse counts were recorded at each location, for separate RF input thresholds of -100, -110 and -120 dBm and a common trigger window of 10 micros-10 ms. Histograms depicting the average pulse count per minute are presented; values range from a maximum of 55x10(3)/min for -120 dBm sensitivity in Berlin, to a minimum of 1.2/min for -100 dBm sensitivity in Belfast, both with vertical polarisation.

Artifacts↗
PubMed2004

Electron capture dissociation in a radio frequency ion trap.

We report on the first evidence of electron capture dissociation (ECD) in a radio frequency (rf) ion trap. Peptide ions, [substance P]2+, trapped in a two-dimensional, linear rf ion trap were cleaved by electrons injected along the central axis of the trap. Along the axis, the rf field component was zero and a magnetic field of 50 mT was applied. This electron injection scheme keeps the energy of the electrons below 1 eV, preventing them from heating by the rf field. The present ECD efficiency is approximately 4% by irradiation of electron current of 0.2 microA for 80 ms. ECD in rf traps may open high-throughput and low-cost ECD applications to obtain molecular structure information complementary to collision-induced dissociation.

Electrons↗
PubMed2007

Multianalyte chemical identification and quantitation using a single radio frequency identification sensor.

We demonstrate an approach for multianalyte chemical identification and quantitation using a single conventional radio frequency identification (RFID) tag that has been adapted for chemical sensing. Unlike other approaches of using RFID sensors, where a special tag should be designed at a much higher cost, we utilize a conventional RFID tag and coat it with a chemically sensitive film. As an example, we demonstrate detection of several vapors of industrial, health, law enforcement, and security interest (ethanol, methanol, acetonitrile, water vapors) with a single 13.56-MHz RFID tag coated with a solid polymer electrolyte sensing film. By measuring simultaneously several parameters of the complex impedance from such an RFID sensor and applying multivariate statistical analysis methods, we were able to identify and quantify several vapors of interest. With a careful selection of the sensing film and measurement conditions, we achieved parts-per-billion vapor detection limits in air. These RFID sensors are very attractive as ubiquitous multianalyte distributed sensor networks.

Acetonitriles↗