MW Frequencies Research Articles

High quality factor cold sintered Li2MoO4[sbnd]BaFe12O19 composites for microwave applications

Ceramics-ceramic composites in series (1-x)Li2MoO4-xBaFe12O19 (LMO-BF12, 0.00 ≤ x ≤ 0.15) have been cold sintered at 120 °C and their structure and properties characterized. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that compositions were dual phase and had a dense microstructure. Composites in the xBF12-(1-x)LMO (0.0 ≤ x ≤ 0.15) series resonated at MW frequencies (∼6 GHz) with 5.6≤εr ≤ 5.8 and Qf = 16,000–22,000 GHz, despite the black colour of compositions with x > 0. The permeability of the composites was measured in the X band (∼8 GHz) and showed an increase from 0.94 (x = 0.05) to 1.02 (x = 0.15). Finite element modelling revealed that the volume fraction of BF12 dictates the conductivity of the material, with a percolation threshold at 10 vol% BF12 but changes in εr as a function of x were readily explained using a series mixing model. In summary, these composites are considered suitable for the fabrication of dual mode or enhanced bandwidth microstrip patch antennas.

Effect of freezing rate and comminution on dielectric properties of pork

The impact of comminution and the freezing rate on the dielectric properties (ε' and ε'') of meats measured at frequencies used for cooking, i.e. radio frequency, RF (27.12 MHz), and microwave, MW (915 and 2450 MHz), were evaluated. The temperature rises (ΔT) were also measured following standardised RF or MW cooking protocols (90 s at 450 W). A factorially designed experiment was conducted and the results suggested that ε' and ε'' were generally, though not always, significantly lower in more highly comminuted samples. At MW frequencies in meats with added ingredients, the frozen products generally had lower ε' and higher ε'' values, while slowly frozen meats with no added ingredients had higher ε' values at MW frequencies. Overall, the impact of comminution and freezing rate on ΔT was relatively minor.

Dielectric properties of myoglobin at 10 GHz by microwave cavity perturbation measurements

We report on the temperature dependence, at microwave (mw) frequency, of the imaginary part of the dielectric constant (ε″) in myoglobin powder samples with different hydration levels (h). The measurements have been performed by the cavity perturbation technique, in the range of temperature 80–345 K. The sample is located inside a glass capillary along the axis of a cylindrical copper cavity, resonating in the TE011mode at 9.6 GHz, where the mw electric field has a node. By measuring the variation of the quality factor of the resonant cavity, one can extract the imaginary part of the dielectric constant. At temperatures higher than 230 K we observe an evident increase of the dielectric losses with increasing temperature; the effect scales almost linearly with hydration, indicating that it must be attributed to a relaxation of water in the hydration shell of the protein. Furthermore, ath≥0.18, we observe a clear peak in the ε″ vs.Tcurve, that shifts towards lower temperatures upon increasing hydration; this shows that the activation enthalpy of the hydration water relaxation decreases with hydration. More in general, our data show that the technique of microwave cavity perturbation allows one to study the dynamics of water molecules in the hydration shell of proteins and to extend information obtained with dielectric techniques to the mw frequencies.

Dielectric properties of myoglobin at 10 GHz by microwave cavity perturbation measurements

We report on the temperature dependence, at microwave (mw) frequency, of the imaginary part of the dielectric constant (e �� ) in myoglobin powder samples with different hydration levels (h). The measurements have been performed by the cavity perturbation technique, in the range of temperature 80-345 K. The sample is located inside a glass capillary along the axis of a cylindrical copper cavity, resonating in the TE011 mode at 9.6 GHz, where the mw electric field has a node. By measuring the variation of the quality factor of the resonant cavity, one can extract the imaginary part of the dielectric constant. At temperatures higher than 230 K we observe an evident increase of the dielectric losses with increasing temperature; the effect scales almost linearly with hydration, indicating that it must be attributed to a relaxation of water in the hydration shell of the protein. Furthermore, at h 0.18, we observe a clear peak in the e �� vs. T curve, that shifts towards lower temperatures upon increasing hydration; this shows that the activation enthalpy of the hydration water relaxation decreases with hydration. More in general, our data show that the technique of microwave cavity perturbation allows one to study the dynamics of water molecules in the hydration shell of proteins and to extend information obtained with dielectric techniques to the mw frequencies.

Dielectric properties of chicken and fish muscle treated with microbial transglutaminase

Transglutaminase (MTGase) initiates the formation of covalent bonds between glutamine and lysine residues in proteins. Adding MTGase can improve the thermal stability of meat proteins, imparting desirable properties to reconstructed products during heating. In this study, the dielectric constant and loss factor of MTGase (0.5%)-treated chicken, salmon and trout muscle were determined and compared with untreated muscle at RF (27 and 40 MHz) and MW (433, 915, and 1800 MHz) frequencies from 20 to 130 °C. The MTGase-treated chicken muscle tended to have higher dielectric constant and loss values at RF frequencies at all temperatures tested. At MW frequencies, the dielectric constants were similar between the MTGase-treated chicken muscle and the control, but the dielectric loss was higher for the MTGase-treated tissue. Similar trends were observed for salmon or trout tissue for dielectric constant; however, at RF frequencies, the dielectric loss factor for MTGase-treated fish was not consistently higher than that of the control. Dielectric loss factors were higher for salmon or trout at RF frequencies than for chicken muscle at the same temperature. The addition of MTGase promotes cross-linking and stronger gel formation for RF and MW treatment.

Low‐Intensity Electromagnetic Millimeter Waves for Pain Therapy

Millimeter wave therapy (MWT), a non-invasive complementary therapeutic technique is claimed to possess analgesic properties. We reviewed the clinical studies describing the pain-relief effect of MWT. Medline-based search according to review criteria and evaluation of methodological quality of the retrieved studies was performed. Of 13 studies, 9 of them were randomized controlled trials (RCTs), only three studies yielded more than 3 points on the Oxford scale of methodological quality of RCTs. MWT was reported to be effective in the treatment of headache, arthritic, neuropathic and acute postoperative pain. The rapid onset of pain relief during MWT lasting hours to days after, remote to the site of exposure (acupuncture points), was the most characteristic feature in MWT application for pain relief. The most commonly used parameters of MWT were the MW frequencies between 30 and 70 GHz and power density up to 10 mW cm−2. The promising results from pilot case series studies and small-size RCTs for analgesic/hypoalgesic effects of MWT should be verified in large-scale RCTs on the effectiveness of this treatment method.

Submillimeter-wave spectrum of H 2Se. Analysis of rotational spectra of all selenium isotopomers in the ground state

Submillimeter rotational spectra of all selenium modifications of H 2Se in the ground vibrational state were investigated. The number of MW data increased three times and the H 2 74Se rotational spectrum was measured for the first time. The data were analyzed using the modified Watson Hamiltonian, enabling us to reduce the number of parameters and to determine them more accurately compared to a conventional Hamiltonian. A combined analysis of MW frequencies and IR ground state combination differences yields rotational and centrifugal H 2Se constants.

Improved analysis of the experimental data on the H 2D + and D 2H + absorption spectra

An improved analysis of the ν 1 fundamental bands of the molecular ions H 2D + and D 2H + has been carried out with two MW frequencies of H 2D + and combination differences from the ν 2 and ν 3 bands of H 2D + and D 2H +. It is shown that the previous analysis of the ν 1 bands was poor because of misassignments. The following reassignments are made: for H 2D +, the line 3168.702 cm −1 is assigned to 5 05-4 04; for D 2H +, the line 2990.154 cm −1 is assigned to 4 41-3 30; the assignments of the lines 2899.242 and 2899.362 cm −1 are interchanged (this interchange was confirmed independently (S. C. Foster, A. R. W. McKellar, and J. K. G. Watson, J. Chem. Phys. 85, 664, 1986)); the line 2832.859 cm −1 is presumably due to the 5 15-5 14 transition of H 2D +. This reassignment results in a fit that is about five times better than that in the previous model of up to J 4 for H 2D + and up to J 6 for D 2H +. A Padé model of a one-dimensional approximation of Watson's Hamiltonian is used in both cases.

Precision absolute measurements of strong and highly inhomogeneous magnetic fields

The low-temperature ([similar or less than]4 K) dependence of the photoconductance in n-type silicon on the conduction electron and bound donor electron spin state serves as the basis of a high-precision, wide-range magnetic field measuring probe, which by virtue of its very small dimensions is well suited for spatial mapping of highly inhomogeneous fields produced by superconducting magnets. The probe may also be adapted to power and frequency measurement of microwave sources operating at approximately mW power levels and frequencies up to approximately 500 GHz.

Effects of Laser Radiation on Biological Systems.

s1 April 1964Effects of Laser Radiation on Biological Systems.Edmund Klein, M.D., Elias Cohen, M.D., Julian Ambrus, M.D., Samuel Fine, M.S.Edmund Klein, M.D.Search for more papers by this author, Elias Cohen, M.D.Search for more papers by this author, Julian Ambrus, M.D.Search for more papers by this author, Samuel Fine, M.S.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-60-4-725_3 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptStudies on the effects of laser radiation in normal and tumor bearing animals and on isolated biological systems have been carried out. Animals included hamsters, mice, rats, and monkeys. The in vitro systems included viable mammalian cells, unicellular organisms and macromolecular preparations of biological origin. Our studies were carried out at 10,600 Å, 6943 Å and 6328 Å, at energy levels from the millijoule region to more than 500 joules, peak power levels exceeding 100 Mw and pulse repetition frequencies of 1/sec. The qualitative and quantitative aspects of the biological effects varied with the characteristics of the radiation. Effects on... This content is PDF only. To continue reading please click on the PDF icon. Author, Article, and Disclosure InformationAffiliations: PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics 1 April 1964Volume 60, Issue 4Page: 725-726KeywordsCellsHeart rateSystems biology Issue Published: 1 April 1964 PDF downloadLoading ...