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At least 163 records · Page 9Linked to original sources
PubMed2005

An implantable telemetry device to measure intra-articular tibial forces.

Tibial forces are important because they determine polyethylene wear, stress distribution in the implant, and stress transfer to underlying bone. Theoretic estimates of tibiofemoral forces have varied between three and six times the body weight depending on the mathematical models used and the type of activity analyzed. An implantable telemetry system was therefore developed to directly measure tibiofemoral compressive forces. This system was tested in a cadaver knee in a dynamic knee rig. A total knee tibial arthroplasty prosthesis was instrumented with four force transducers located at the four corners of the tibial tray. These transducers measured the total compressive forces on the tibial tray and the location of the center of pressure. A microprocessor performed analog-to-digital signal conversion and performed pulse code modulation of a surface acoustic wave radio frequency oscillator. This signal was then transmitted through a single pin hermetic feed-through tantalum wire antenna located at the tip of the stem. The radio frequency signal was received by an external antenna connected to a receiver and to a computer for data acquisition. The prosthesis was powered by external coil induction. The tibial transducer accurately measured both the magnitude and the location of precisely applied external loads. Successful transmission of the radio frequency signal up to a range of 3m was achieved through cadaveric bone, bone cement, and soft tissue. Reasonable accuracy was obtained in measuring loads applied through a polyethylene insert. The implant was also able to detect unicondylar loading with liftoff.

Cadaver↗
PubMed2004

The use of an intraoral electrolarynx for an edentulous patient: a clinical report.

This clinical report describes the clinical requirements, treatment sequence, and use of a relatively new intraoral electrolarynx for a completely edentulous patient. This device consists of a sound source attached to the maxilla and a hand-held controller unit that controls the pitch and volume of the intraoral sound source via transmitted radio waves.

Aged↗
PubMed2006

The observation of abnormal signals in laser flash photolysis: a type of probable synchronized nuclear spin signals.

In laser flash photolysis (LFP) work, noise-like signals were observed together with transient absorption decay spectra in time domain. Analyzed results show that it is a valuable resonance spectrum of excited state molecules, in which four molecular cases are given here. We proposed that this kind signal might originate from nuclear or nuclear and electron spin resonance features in the excited molecules based on radio wave frequency spectrum levels and the significant interaction with static magnetic field.

Adenine↗
PubMed2005

Heat therapy for cutaneous leishmaniasis elicits a systemic cytokine response similar to that of antimonial (Glucantime) therapy.

Controlled heat delivered as radio waves has been used successfully in the treatment of cutaneous leishmaniasis (CL). Here we investigated whether local heat therapy has systemic effects, as measured by the modulation of cytokine production following heat therapy of CL lesions compared with antimonial (Glucantime) treatment. Patients with CL were randomly assigned into this study. Heat (50 degrees C for 30s) was applied once. The control group received Glucantime therapy for 20 d. Cytokine production by peripheral blood mononuclear cells was assayed on days 0, 14 and 28 after onset of treatment. At the end of 28 d, 75% of lesions were healing or healed in the heat therapy group and 90% in the control group (P=0.1261). There was a decrease in IFN-gamma, IL-5 and TNF-alpha levels comparing day 0 with day 28 in both groups, but no difference between the two therapy groups. In patients with only one of several lesions treated with heat therapy, the untreated lesions also healed. Local heat therapy in CL lesions leads to systemic cytokine responses similar to that induced by systemic Glucantime therapy.

Adolescent↗
PubMed1975

A simple method of checking the ECG paper speed.

A simple method of determining accurate rates on ECG machines has been described. A short-wave radio, capable of tuning station WWV (5, 10 or 15 MHz) and a telephone amplifier may be used to place the precise 1 second intervals pulses on the ECG, from which exact paper speed is determined. This information may then be used to calculate the precise rate of an implanted pacemaker stimulus for evaluating pacemaker battery life.

Electrocardiography↗
PubMed1996

Collecting, archiving, and sharing of digitized medical information.

Telemedicine is the practice of medicine via telephony. Telemedicine has developed into an affordable, indispensable tool for use by frontline veterinary clinicians, hospitals, and clinics. Board certified specialists are available via telemedicine with little more difficulty than making a long distance telephone call. Current technology allows clinicians to refer cases via the Internet, radio waves, satellite, or land lines. Cases may include typed data, audio clips such as cardiac auscultation, high resolution imagery for radiographs, ultrasound, and microscopy. This article is a primer on digitization and transmission of images.

Animals↗
PubMed2003

Gigantic jets between a thundercloud and the ionosphere.

Transient luminous events in the atmosphere, such as lighting-induced sprites and upwardly discharging blue jets, were discovered recently in the region between thunderclouds and the ionosphere. In the conventional picture, the main components of Earth's global electric circuit include thunderstorms, the conducting ionosphere, the downward fair-weather currents and the conducting Earth. Thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere, where the electric potential is hundreds of kilovolts higher than Earth's surface. It has not been clear, however, whether all the important components of the global circuit have even been identified. Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude approximately 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites.

Journal Article↗
PubMed2005

Lightning-induced intensification of the ionospheric sporadic E layer.

A connection between thunderstorms and the ionosphere has been hypothesized since the mid-1920s. Several mechanisms have been proposed to explain this connection, and evidence from modelling as well as various types of measurements demonstrate that lightning can interact with the lower ionosphere. It has been proposed, on the basis of a few observed events, that the ionospheric 'sporadic E' layer--transient, localized patches of relatively high electron density in the mid-ionosphere E layer, which significantly affect radio-wave propagation--can be modulated by thunderstorms, but a more formal statistical analysis is still needed. Here we identify a statistically significant intensification and descent in altitude of the mid-latitude sporadic E layer directly above thunderstorms. Because no ionospheric response to low-pressure systems without lightning is detected, we conclude that this localized intensification of the sporadic E layer can be attributed to lightning. We suggest that the co-location of lightning and ionospheric enhancement can be explained by either vertically propagating gravity waves that transfer energy from the site of lightning into the ionosphere, or vertical electrical discharge, or by a combination of these two mechanisms.

Journal Article↗
PubMed2003

Nutrition studies on protein and energy in domestic cats.

The effects of three diets varying in their protein, fat and carbohydrate contents and of physical activity on energy and protein metabolism were investigated in eight domestic cats. The diets were based on canned food with addition either of minced cattle heart, melted swine fat or polenta. The activity-induced heat production was measured in a respiration chamber using the Doppler effect of radio-waves reflected from moving bodies. In the group receiving the high-protein diet, urinary nitrogen concentration was higher which was reflected in higher urinary loss of energy without affecting the amount of energy retained. Nitrogen utilization was not significantly influenced by nitrogen intake. Mean daily total heat production ranged between 163 and 187 kJ/kg BW/day or 215 and 270 kJ/kg BW(0.75)/day. The daily crude protein requirement of adult cats was determined to be 2.7 g/kg BW/day. The daily requirement of metabolizable energy for maintenance was estimated to be 153 kJ/kg BW/day or 226 kJ/kg BW(0.75)/day. The activity-induced heat production was 25.1 kJ/kg BW/day which corresponded to 13.5% of the total daily heat production. The daily requirement for metabolizable energy was thus reduced by 20.9 kJ/kg BW/day or 13.7%. The activity pattern of the cats was not characterized by a circadian rhythm.

Animal Feed↗
PubMedDate not supplied

Biomechanics of the first ray part V: The effect of equinus deformity. A 3-dimensional kinematic study on a cadaver model.

The positional change of the medial column of the foot in closed kinetic chain with variable Achilles tendon tension was investigated in seven fresh frozen cadaver specimens using a 3-dimensional radio wave tracking system. The distal tibia and fibula and the intact ankle and foot and were mounted on a non-metallic loading frame. The frame allowed positioning of the foot to simulate midstance phase of gait while the tibia and fibula were axially loaded to 400 N. To record osseous motion, receiving transducers were attached to the first metatarsal, medial cuneiform, navicular, and talus. Movements of these bones in 3-dimensional space were measured as specimens were axially loaded and midstance motor function was simulated using pneumatic actuators. To simulate a progressive equinus influence, force was applied to the Achilles tendon at tensile loads of 0%, 30%, and 60% of predicted maximum strength during each test trial. Osseous positions and orientations were collected and analyzed in all three cardinal planes utilizing data recorded. As Achilles load increased, the position of the first metatarsal became significantly more inverted ( P < .05). Although not statistically significant, remarkable trends of arch flattening motion were detected in the distal segments of the medial column with varied Achilles load. Increased Achilles load reduced the influence of peroneus longus on the medial column.

Achilles Tendon↗
PubMedDate not supplied

Transcutaneous optical telemetry system with infrared laser diode.

A transcutaneous telemetry system is indispensable when monitoring and controlling the operation of an artificial heart totally implanted inside the body. A telemetry system using light is more useful than radio waves from the viewpoint of electromagnetic interference and power consumption. In this report, a transcutaneous optical coupler consisting of an infrared laser diode (LD) and a PIN photodiode (PINPD) was evaluated, and the transcutaneous optical coupling and information transmission characteristics were evaluated in in vitro experiments. The wavelength and directional angle of the LD used were 830 nm and 9.5 degrees, respectively. With regard to the directional angle of PINPD, the authors found that a PINPD with a larger directional angle allowed for more deviation between the axes optical axes of the LD and the PINPD. It was also found that the transcutaneous coupler had an optimum distance for the permissible deviation to be maximized. The information signals modulated by the phase shift keying (PSK) were transmitted at a rate of 9,600 bps through goat skin 4 mm thick, and demodulated by the phase locked loop (PLL) on the receiving side. As a result, the information signals were demodulated without any errors in deviation within 10.5 mm at a distance of 11 mm. In conclusion, the transcutaneous optical telemetry system using an infrared LD has sufficient characteristics to monitor and control the operation of an artificial heart totally implanted inside the body.

Heart, Artificial↗
PubMed1989

An experimental study of spinal cord evoked potentials and histologic changes following spinal cord heating.

To study the safety of hyperthermia cancer treatment, canine spinal cords were heated with radio waves to between 43 C and 47 C for 30 minutes. Spinal cord evoked potentials (SCEP) studied by epidural recording after epidural stimulation showed shortened latency and unchanged amplitude at 44 C or below. At 45 C or above, reduction of amplitude combined with shortened latency was observed, a phenomenon that has not hitherto been reported. After heating to 45 C, SCEP recovered with the reduction of temperature, but histologic examinations showed pigment exudation, vacuolation, and hemorrhage. These results suggest that tolerable spinal cord temperature should not exceed about 44 C.

Animals↗
PubMed2000

Circular polarization induced by scintillation in a magnetized medium

A theory is presented for the development of circular polarization as radio waves propagate through the turbulent, birefringent interstellar medium. The fourth order moments of the wave field are calculated, and it is shown that unpolarized incident radiation develops a nonzero variance in circular polarization. A magnetized turbulent medium causes the Stokes parameters to scintillate in a nonidentical manner. A specific model for this effect is developed for the case of density fluctuations in a uniform magnetic field.

Journal Article↗
PubMed2005

On the performance of telemedicine system using 17-GHz orthogonally polarized microwave links under the influence of heavy rainfall.

This paper describes the design of a telemedicine system based on next-generation wireless local area networks (WLANs) operating at 17 GHz. Seventeen gigahertz is proposed for next-generation WLAN services offering numerous advantages over traditional IEEE 802.11 networks that operate in the range of 2.4-5 GHz. Orthogonal polarization is often used to increase spectrum efficiency by utilizing signal paths of horizontal and vertical polarization. Radio waves exceeding 10 GHz are particularly vulnerable to signal degradation under the influence of rain which causes an effective reduction in isolation between polarized signal paths. This paper investigates the influence of heavy rain in a tropical region on wide-band microwave signals at 17 GHz using two links provided by a fixed broad-band wireless access system for two-way data exchange between paramedics attending an accident scene and the hospital via microwave equipment installed in the ambulance. We also study the effects of cross polarization and phase rotation due to persistent heavy rainfall in tropical regions.

Computer Communication Networks↗
PubMed2007

Histologic comparison of canine skin biopsies collected using monopolar electrosurgery, CO2 laser, radiowave radiosurgery, skin biopsy punch, and scalpel.

OBJECTIVE: To compare the histologic appearance of canine skin biopsies collected by use of a scalpel, skin biopsy punch, monopolar electrosurgery, CO2 laser, and radio wave radiosurgery in fully rectified wave form (RWRS). STUDY DESIGN: Experimental, randomized design. ANIMALS: Healthy adult grayhounds (n=4). METHODS: Skin biopsies were collected using 5 techniques. Cut margins of biopsy specimens and adjacent peripheral skin were evaluated using light microscopy to compare penetration of the dermis by tissue carbonization (char). RESULTS: No char occurred in skin specimens collected by biopsy punch and scalpel. Char penetration occurred in all specimens collected by electrosurgery, CO2 laser, and RWRS. Mean char penetration in skin biopsies collected by RWRS (0.158 mm) was significantly less than for monopolar electrosurgery (0.223 mm) and CO2 laser (0.215 mm). Mean char penetration in adjacent peripheral skin surrounding biopsies collected by RWRS (0.171 mm) was significantly less than monopolar electrosurgery (0.255 mm) but not less than CO2 laser (0.215 mm, P<.07). CONCLUSIONS: RWRS (blended waves in cut-coagulate mode) caused less lateral thermal damage to canine skin biopsies than monopolar electrosurgery and CO2 laser and less lateral thermal injury to peripheral skin than monopolar electrosurgery. CLINICAL RELEVANCE: Excision of canine skin biopsies with heat-generating devices may not allow reliable histologic interpretation, particularly when assessing margins of small biopsy specimens. RWRS may be less traumatic to canine skin than monopolar electrosurgery and CO2 laser when used to make incisions.

Animals↗
PubMed2006

Tele-education.

Tele-education has been used for many years to deliver continuing education programmes to rural health-care professionals. The main modes are audio, video and computer. Audio technologies involve the transmission of the spoken word (voice) between learners and instructors, either synchronously or asynchronously. Examples of the former include audioconferencing and short-wave radio; examples of the latter include audiotape or audiocassette. Video for distance learning, like audio, can be used in either synchronous or asynchronous fashion. Videoconferencing, or interactive television, are considered synchronous because there is the opportunity for live visual and verbal interaction between instructors and learners. Asynchronous instructional video tools include slow-scan video, interactive videodiscs and videotapes. Computer-assisted learning or instruction can be defined as any learning that is mediated by a computer and which requires no direct interaction between the user and a human instructor in order to run. It is becoming increasingly common. Examples include: the Internet and World Wide Web, email, synchronous and asynchronous computer-mediated communication applications and interactive multimedia applications on CD-ROM. Tele-education technologies have an important role to play in addressing the professional isolation which is experienced by rural and remote health-care professionals.

Audiovisual Aids↗
PubMed2002

Cosmic rays activity and monthly number of deaths: a correlative study.

We studied the relation between the intensity of cosmic rays, the level of solar/geomagnetic activity, and the monthly numbers of deaths in a large hospital in Israel and in all Lithuania. The Israeli data include 30526 hospital deaths, two groups of fatal suicides (2359, 2763), and 15435 suicidal attempts for two periods of 108 and 236 consecutive months. The national data for the entire Republic of Lithuania include 424925 deaths for the period of 120 consecutive months. Cosmic rays intensity was measured by an Apatity neutron monitor. We obtained the data on solar, geomagnetic radiovawe propagation, ionosphere ionization hours, proton flux of two energy levels (>90 and 60 MeV) from the National Geophysical Data Center at Goddard Space Flight Center, National Space Environment Center at Boulder, Colorado, USA, and from the Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Russia. We calculated Pearson coefficients and their probabilities for correlation between monthly space activity level and monthly number of male and female deaths from different causes. Cosmic rays activity revealed significant negative correlation with solar/geomagnetic activity indices and related physical phenomena levels. This activity strongly correlated with flux of protons with the energies >90 MeV proton flux and did not exhibit significant correlation with 60 MeV proton fluxes. Cosmic rays intensity correlation with monthly numbers of deaths was strong for noncardiovascular deaths, suicides, and traffic accidents. The correlation was much weaker for deaths caused by ishemic heart disease and strokes.

Accidents↗
PubMed2006

Survey on cellular phone usage on students in Thailand.

The number of cellular phone subscribers is increasing every year and there have been reports of health disorders related to the high-frequency radio waves. This paper considers the dependence of Thai university and high school students on cellular phones. A survey form (cellular phone dependence questionnaire: CPDQ) was distributed to 181 female and 177 male Thai university students and to 240 female and 140 male Thai high school students. The surveys were collected, Cronbach alpha coefficient was calculated, and a factor analysis was performed using the principal factor method and varimax rotation. The total scores were 16.54 to 20.04 and the Cronbach's alpha coefficients were 0.808 to 0.930. According to a factor analysis of 20 scored items, 4 factors were extracted for both male and female high school students, and the cumulative correlation coefficients of the male and female groups were 64.85% and 62.70%, respectively. Five factors were extracted for male university students and 6 factors were extracted for female university students, and the cumulative correlation coefficients were 58.08% and 57.91%, respectively. The W value results of the Shapiro-Wilk W-test for male university students, female university students, male high school students and female high school students were 0.969, 0.984, 0.964, and 0.913 respectively, thus verifying the normality of the score distributions. The total scores for the Thai university students were higher than the scores for the Thai high school students. The factor analysis of female high school students confirmed a large difference compared to male university students, male high school students, and Japanese female university students. (The Japanese students were surveyed in an earlier study by Toda et al.). Also, the CPDQ total score was high, which indicated a strong tendency toward dependence.

Adolescent↗