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At least 145 records · Page 8Linked to original sources

[Radiosurgical excision in the treatment of cervical intraepithelial neoplasia].

39 patients affected by CIN had undergone radio surgical excision. This non-traumatic method employs 3.8 MHz radio waves are employed to cut and/or coagulate. The radio surgical excision was carried out by a loop electrode, or microneedle, according to the colposcopic, histologic and microcolpohysteroscopic characteristics of the cervical lesion. In fact 14 patients, among whom 11 affected by CIN I and 4 by CIN II with a total visibility of squamous columnar junction and not extended lesion of the cervical canal, had undergone radio surgical excision through various dimensions loop according to the size of the tissue to be excised. Whereas 10 CIN II patients who had not entirely visible squamous columnar junction or large cervical canal lesion, and 14 CIN III patients underwent to radiosurgical conization through a subtle and extensible tungsten thread according to the size of the tissue to be excised. In the 100% of the both groups the recovery was confirmed after three and six months. Inno cases cervical canal stenosis was observed and the squamous columnar junction resulted well visible. In both groups no thermal damages on the excised tissue, which could create difficulties on the histological diagnosis, were observed. Therefore, this method resulted an easy and cheap technique to be executed in surgery with excellent results under the therapeutic and economical aspect.

Adult↗

[Light, laser and PDT therapy for acne].

In recent years, a number of studies have evaluated the treatment of acne using electromagnetic waves, such as lasers, photodynamic therapy, visible light or radio waves. While the efficacy of laser treatment is still uncertain, photodynamic therapy shows promising results, but with marked side-effects, as destruction of sebaceous glands. Treatment with blue light (405-420 nm wavelength) also appears effective and can be regarded as an treatment option for inflammatory acne.

Acne Vulgaris↗

Luxemburg-gorky effect retooled for elastic waves: a mechanism and experimental evidence.

A new mechanism is proposed for the linear and amplitude-dependent dissipation due to elastic-wave-crack interaction. We have observed one of its strong manifestations in a direct elastic-wave analog of the Luxemburg-Gorky effect consisting of the cross modulation of radio waves at the dissipative nonlinearity of the ionosphere plasma. The counterpart acoustic mechanism implies, first, a drastic enhancement of the thermoelastic coupling at high-compliance microdefects, and, second, the high stress-sensitivity of the defects leads to a strong stress dependence of the resultant dissipation.

Journal Article↗

Observation of the "Luxemburg-Gorky effect" for elastic waves.

An experimental observation of a new nonlinear-modulation effect for longitudinal elastic waves is reported. The phenomenon is a direct elastic wave analogy with the so-called Luxemburg-Gorky (L-G) effect known over 60 years for radio waves propagating in the ionosphere. The effect consists of the appearance of modulation of a weaker initially non-modulated wave propagating in a nonlinear medium in the presence of an amplitude-modulated stronger wave that produces perturbations in the medium properties on the scale of its modulation frequency. The reported transfer of modulation from one elastic wave to another was observed in a resonator cut of a glass rod containing a few small cracks. Presence of such a small damage drastically enhances the material nonlinearity compared to elastic atomic nonlinearity of homogeneous solids, so that the pronounced L-G type cross-modulation could be observed at strain magnitude in the stronger wave down to 10(-7) and smaller. Main features of the effect are pointed out and physical mechanism of the observed phenomena is discussed.

Journal Article↗

Radio and plasma wave observations at Saturn from Cassini's approach and first orbit.

We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 +/- 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.

Journal Article↗

Nikola Tesla: the man behind the magnetic field unit.

The magnetic field strength of both the magnet and gradient coils used in MR imaging equipment is measured in Tesla units, which are named for Nikola Tesla. This article presents the life and achievements of this Serbian-American inventor and researcher who discovered the rotating magnetic field, the basis of most alternating-current machinery. Nikola Tesla had 700 patents in the United States and Europe that covered every aspect of science and technology. Tesla's discoveries include the Tesla coil, AC electrical conduction, improved lighting, newer forms of turbine engines, robotics, fluorescent light, wireless transmission of electrical energy, radio, remote control, discovery of cosmic radio waves, and the use of the ionosphere for scientific purposes. He was a genius whose discoveries had a pivotal role in advancing us into the modern era.

Electricity↗

Ndn, volume transmission, and self-organization in brain dynamics.

Fields of neural activity are seen in synchronized oscillations that are detected at mesoscopic scales in syntheses of multicellular recordings of action potentials and electroencephalograms (EEGs) over broad areas of cerebral cortex. The waves often have large-scale, highly textured spatial patterns of cortical activity, formed in the context of associative learning under classical and operant conditioning in rabbits. The patterns show spatial amplitude modulation of shared oscillations of carrier waves in the beta and gamma ranges of the EEG, with recurrence at frame rates in the alpha and theta ranges. The frames also show spatial phase modulation that is inconsistent with driving of the oscillations by focal pacemakers. The hypothesis is developed that the synchronization manifests continuous distributions of activity in cortical neuropil that modulate firings of selected neural networks embedded in the neuropil. Five interactive agencies have been postulated to explain the mechanism for the field synchrony: electric fields; magnetic fields; electromagnetic fields (radio waves); diffusion chemical gradients; and order parameters that control self-organization of large populations of neurons by widespread synaptic interaction constituting negative and positive feedback. Only the last interactive agency fits the data. The points are emphasized that these field patterns in frames require interactive neural dynamics that is modulated in respect to global operations mediating arousal, attention, selective emotional stance, wake, sleep, learn, habituate, dishabituate, etc., and that these operations require differing but complementary fields that form by massive parallel feed-forward architectures of brainstem neuromodulatory nuclei. An example is given using histamine of the neural discharges of brainstem nuclei that do not require fine spatiotemporal texturing of their firing; they operate by nonsynaptic release of neuromodulators that effect changes in background state, such that textured patterns of cortical activity can form and update in flexible adaptations of brains to their environments. These systems instantiate volume transmission by nonsynaptic diffusion transmission, in concert with the self-organization of the textured neural activity that supports cognition.

Animals↗

Measurement of the spatial coherence of a trapped Bose gas at the phase transition

The experimental realization of Bose-Einstein condensates of dilute gases has allowed investigations of fundamental concepts in quantum mechanics at ultra-low temperatures, such as wave-like behaviour and interference phenomena. The formation of an interference pattern depends fundamentally on the phase coherence of a system; the latter may be quantified by the spatial correlation function. Phase coherence over a long range is the essential factor underlying Bose-Einstein condensation and related macroscopic quantum phenomena, such as superconductivity and superfluidity. Here we report a direct measurement of the phase coherence properties of a weakly interacting Bose gas of rubidium atoms. Effectively, we create a double slit for magnetically trapped atoms using a radio wave field with two frequency components. The correlation function of the system is determined by evaluating the interference pattern of two matter waves originating from the spatially separated 'slit' regions of the trapped gas. Above the critical temperature for Bose-Einstein condensation, the correlation function shows a rapid gaussian decay, as expected for a thermal gas. Below the critical temperature, the correlation function has a different shape: a slow decay towards a plateau is observed, indicating the long-range phase coherence of the condensate fraction.

Journal Article↗

[Experimental-morphological study of the effects of diode laser scalpel with different irradiation parameters (wave length 0.97 mm) on oral mucosa].

An experimental-morphologic study of the effects of diode laser scalpel with different irradiation parameters (wave length 0.97 mm) on oral mucosa of 12 rabbits showed that incisions on oral membrane of the tongue, cheek and palate made by diode laser scalpel in different modes of operation (diode laser scalpel LC-0.97-IRE-Polus: in continuous mode /4 W/; frequency modulated mode 2000 x 100 /5 W/; frequency modulated mode 1000 x 50 /6 W/) after 2 hours produced the effect of superficial tissues defects with consequent development in 1-2 days of necrotic changes, oedema and angiomatosis, as well as perifocal inflammatory and productive reactions in the defects walls. In the continuous mode /4 W/ and frequency modulated mode 2000 x 100 /5 W/ to 10th day of the experiment there was epithelization of mucous defects on thr tongue, cheek and palate. This effect was observed only on day 20 after the frequency modulated mode 1000 x 50 /6 W/. In the control (incisions by radio-wave scalpel) epithelization of oral mucous membrane defects was seen on day 5-10 that was comparable with laser scalpel effects. Thus optimal results (by criterion of oral mucous membrane incisions healing) were received in the continuous mode /4 W/ and frequency modulated mode 2000 x 100 /5 W/.

Animals↗

Use of a pressure-sensitive radiotelemetering capsule to study the canine gastric interdigestive complex.

An inexpensive pressure-sensitive radiotelemetering capsule, transmitting at 100 MHz, was used to study gastric interdigestive complexes. The oscillator was frequency modulated; pressure changes on a rubber diaphragm caused displacements of a ferromagnetic core altering the frequency of oscillation by modifying the inductance in the circuit. The system was linear for applied pressures up to 40 mm of Hg; for 40 mm Hg the frequency decreased by 22 kHz. Three fasted dogs were used; an encapsulated radio pill picked up the presence fluctuations associated with gastric contractions and transmitted these signals as radio waves. An FM receiver intercepted, amplified, and relayed the signals to a chart recorder, which produced a permanent record. During the first part of each 24-hour recording period, cyclical interdigestive patterns consisting of a series of high-amplitude contractions followed by long-lasting quiescence were recorded. Regular outbursts showed mean durations ranging from 11.6 to 17.6 minutes, mean periods from 27 to 51 minutes, and mean amplitudes from 9.9 to 11.1 mm Hg. Noncyclical, irregular recordings were obtained during the last part of each recording period. These results are similar to ones obtained using force transducers.

Animals↗

Advantages of low output mobile communication systems in hospitals.

Mobile telephone systems using radio waves with very low power outputs rarely interfere with electronic medical equipment, which allows them to be safely installed in hospitals. The Personal Handy-phone System, PHS, which was developed and is widely used in Japan, is one such system. It has many useful functions including voice communication, string message transfer, e-mail, an answering system limited to selected persons or groups, paging, automatic call transfer, and handset positioning. In this paper we discuss the benefits of these functions confer to hospital communication systems.

Computer Communication Networks↗

Thermophysiological consequences of whole body resonant RF exposure (100 MHz) in human volunteers.

Thermophysiological responses of heat production and heat loss were measured in seven adult volunteers (six males and one female, aged 31-74 years) during 45 min dorsal exposures of the whole body to 100 MHz continuous wave (CW) radio frequency (RF) energy. Three power densities (PD) (average PD = 4, 6, and 8 mW/cm(2); whole body specific absorption rate [SAR] = 0.068 [W/kg]/[mW/cm(2)]) were tested in each of three ambient temperatures (T(a) = 24, 28, and 31 degrees C), as well as in T(a) controls (no RF). A standardized protocol (30 min baseline, 45 min RF or sham exposure, 10 min baseline) was used. Measured responses included esophageal and seven skin temperatures, metabolic heat production, local sweat rate, and local skin blood flow. No changes in metabolic heat production occurred under any test condition. Unlike published results of similar exposures at 450 and 2450 MHz, local skin temperatures, even those on the back that were irradiated directly, changed little or not at all during 100 MHz exposures. The sole exception was the temperature of the ankle skin, which increased by 3-4 degrees C in some subjects at PD = 8 mW/cm(2). During the 45 min RF exposure, esophageal temperature showed modest changes (range = -0.15 to 0.13 degrees C) and never exceeded 37.2 degrees C. Thermoregulation was principally controlled by appropriate increases in evaporative heat loss (sweating) and, to a lesser extent, by changes in skin blood flow. Because of the deep penetration of RF energy at this frequency, effectively bypassing the skin, these changes must have been stimulated by thermal receptors deep in the body rather than those located in the skin.

Adult↗

Biological dosimetry of magnetic resonance imaging.

PURPOSE: To check the bioeffects of the components of magnetic resonance imaging (MRI). MRI is based on an assumed harmless interaction between certain nuclei in the body when placed in a strong magnetic field and radio wave fields. There are three key factors actuating on the examining body: a powerful static magnetic field (SMF), magnetic gradient fields (MGFs), and pulsed radiofrequency (RF) radiation. MATERIALS AND METHODS: In vitro cells (L-132 cells) were used as biosensors, and different cellular compounds were used as biomarkers (heat shock proteins [HSPs] and their messenger ribonucleic acids [mRNAs], calcium, and adenosine-3',5'-cyclic monophosphate [cAMP]). The biosensors were placed in the bore of a 1.5-T MRI machine and the different electromagnetic fields were operated. RESULTS: HSPs and their mRNAs and cAMP did not respond to SMF, MGFs, or RF radiation. RF radiation increased cytosolic calcium concentration (18%, P < 0.05). CONCLUSION: Although MRI procedures do not induce any cellular stress response, it may cause an unfathomable calcium increase in vitro. Although the in vitro experimental conditions are not totally comparable to clinical situations, the usefulness of the in vivo biological dosimetry, circulating leukocytes as biosensors, and HSPs and/or calcium as biomarkers is suggested.

Calcium↗

The quantum origins of the free induction decay signal and spin noise.

Experiments are described that elucidate the quantum mechanical origins of the free induction decay voltage and of spin noise. It is shown that the experimentally measured FID voltage induced in a Hertzian loop receiving coil following a 90 degrees pulse is typically two orders of magnitude too large to be accounted for by the current quantum theory of signal reception-coherent spontaneous emission. An experiment is then presented in which spin noise is easily observed in a circuit with a Q-factor of order unity, thereby undermining a popular hypothesis that such noise is due to spontaneous emission and is only observable because of the enhancement in the density of the radiation field in a high Q-factor tuned circuit, the NMR probe. Both the free induction decay and the spin noise are shown to be accurately predicted by near-field Faraday induction, which is described in the theory of quantum electrodynamics by an exchange of virtual photons. A heuristic approach to understanding the nature and role of virtual photons in the signal reception process is then given. Thus current popular statements that observation of the magnetic resonance phenomenon relies on the absorption and emission of radio waves are shown to be wrong.

Journal Article↗

Centred radio-frequency hyperthermia in solid tumours.

After some notions on the mechanisms of action of radio-waves on solid tumours, the treatise illustrates the results achieved in the first 125 cases of malignant tumours treated with this method, its results are definitely encouraging, even in cases apparently with no hope. It also describes briefly the histologic modifications induced by this therapeutic method on neoplastic masses and discusses the criteria of the directions of thermotherapy, alone or combined, which is obviously the fifth weapon against tumours.

Adult↗

A method to perfuse liver metastases with heated blood (45 degrees C, 45 min).

To heat the livers in ten pigs (20-30 kg) a system of two pumps, both connected to the cannulated A.femoralis and to two radio-wave heating devices, was used. With pump I the arterial vascular system of the liver was perfused for 45 min via the A.gastroduodenalis with a constant volume of 150-200 ml blood/min, heated to 44-45 degrees C. With pump II 50-700 ml/min heated blood was pumped into the portal vein to raise the temperature and oxygen content of the portal flow. During the heating period the A.hepatica was clamped. A temperature of 45 degrees C is a highly toxic for the differentiated liver tissue, but the more simply structured wall of the arteries tolerates this temperature. This difference in heat resistance allows the perfusion of the arterial vascular system of the liver with blood heated to a temperature that is fatal to liver tissues. On the way from the A.gastroduodenalis to the liver periphery the heated blood becomes cooled by the surrounding cooler liver tissues. Finally the supply to the lobules is a mixture of arterial and venous blood, i.e. the highly toxic agent, heat, becomes "detoxified" by cooling before reaching the heat-sensitive liver lobules. Changing flow and temperature in the portal vein allows the temperature of the liver lobules to be kept within a safe range, i.e. below 43 degrees C. The raised oxygen content in the portal flow allows the arterial perfusion to be stopped for 10 min (to subject a heated metastasis to a period of hypoxia). Liver enzymes reached their maximal level 2 days after heating and returned to normal within 1 week. It is supposed that this method allows the temperature in a liver metastasis to be raised to a tumoricidal level.

Animals↗

Biotelemetry: an original approach to experimental models of inflammation.

Biotelemetry is a new biological technology which evaluates continuous spontaneous locomotor activity and body temperature in rodents. The telemetry system comprises a transmitter implanted in the peritoneal cavity of the rodent, and a receiver placed beneath the animal's cage. The receiver detects the radio waves and the activity of the rodents as counts which are registered in the computer system, and the adapter detects the calibrated body temperature. First, we showed that biotelemetric studies of different species (rats, guinea pigs, mice and gerbils) provide substantial information about their circadian rhythms. Second, using the most common examples employed in pharmacology of inflammation (hyperthermia, arthritis, ischemia-reperfusion and so on) biotelemetry has helped us to clarify the pathophysiological significance of the parameters of temperature and mobility in several experimental models in rodents.

Animals↗

Nuclear magnetic resonance imaging. Review of early clinical experience.

Nuclear magnetic resonance tomography is a powerful new imaging modality which produces cross-sectional images similar to those obtained by computerized tomography. However, unlike computerized tomography, nuclear magnetic resonance imaging does not use ionizing radiation but rather utilizes an apparently safe interaction between magnetic fields, radio waves, and atomic nuclei. Basic principles of nuclear magnetic resonance imaging are discussed briefly and promising early clinical applications are reviewed. The two magnetic relaxation times, T1 and T2, provide discrimination between tissues based on differences in fat and water content. Tumors are readily differentiated from normal tissue on the basis of the increased water content, primarily due to edema and hypervascularity. Although nuclear magnetic resonance imaging is very sensitive in the detection of these abnormalities, it is not yet able to provide a specific diagnosis.

Arteriosclerosis↗