MF Signals Research Articles

МОДЕРНИЗАЦИЯ СИНТЕЗАТОРОВ ЧАСТОТ РАДИОСТАНЦИИ УКВ РАДИОСВЯЗИ

Trends and prospects for the development of modern systems and complexes of radio communication, features of the use of frequency synthesizers based on the pulse-phase-locked loop in modern radio communications are analyzed. The results of the MF modernization on an integrated circuit HMC704 for transceivers of VHF radio stations are presented. The modeling of the upgraded midrange main units was carried out in the TI PLLatinumSim program. The LPF elements values and power spectral density of the output MF signal phase noise on LMX2594 IC are calculated. Due to the possibility of using a high comparison frequency in a frequency-phase detector, it was possible to improve the weight and size indicators, increase the speed and purity of the output signal spectrum of upgraded MF, which was confirmed by the results of modeling and experimental studies of the current synthesizer layout.

Characterization and expression analysis of seven putative JHBPs in the mud crab Scylla paramamosain: Putative relationship with methyl farnesoate.

Juvenile hormone binding proteins (JHBPs) serve as the carriers that transport juvenile hormone (JH) to target tissues to activate JH signals. In this study, seven JHBPs from mud crab Scylla paramamosain were obtained. All Sp-JHBPs contained one JHBP domain, and Sp-JHBP4, 5, 6 also contained one Grp7_allergen domain. The predicted secondary and 3D structures are conserved among the seven Sp-JHBP domains, but the complete 3D structure of Sp-JHBP4, 5, 6 were more similar to lipopolysaccharide binding protein. Additionally, the potential ligands for Sp-JHBP1, 2, 3, 7 were ubiquinone 8 (UQ8) and JH II or JH III, and the predicted binding location and sites for JHs were similar to the structured known BmJHBP, suggesting that MF is a potential ligand for these Sp-JHBPs. Furthermore, the expression analysis showed that Sp-JHBP1 expression is relatively low in the 14 detected tissues, and Sp-JHBP2 has the highest expression in the ovary, while the other five JHBPs are highly expressed in the hepatopancreas. During larval development, Sp-JHBP2 is highly expressed during the Z1, M and C1 stages, which are three post-metamorphosis stages, while Sp-JHBP3 and 4 expression levels were significantly lower during the Z5 and M stages, which are two pre-metamorphosis stages. Moreover, the in vivo and in vitro study revealed that Sp-JHBP2 expression was reduced by MF, while the in vitro studies showed that Sp-JHBP3, 6, 7 are induced by MF in a concentration-independent manner. Taken together, we hypothesized Sp-JHBP1, 2, 3, 7 has the potential to bind MF and Sp-JHBP2, 3, 7 play a more important roles in MF signal, while Sp-JHBP4, 5, 6 were more likely to participate in immune response.

Lightning and TLE electric fields and their impact on the ionosphere

Abstract This article presents a review of broad band electric field measurements recently performed near thunderstorm areas. It is shown that large lightning pulses propagate up to the upper ionosphere, where they are reflected, producing natural ionograms. Lightning and sprite electric fields are characterised in different frequency bands and localised. The distance between sprite and parent lightning reaches ten kilometres. Transient MF signals are recorded simultaneously with some sprites. In addition short term fading of MF radio link signals are observed after lightning due to an increased absorption in the lower ionosphere induced by thermal electron heating. Their horizontal extension is larger than 200 km which is comparable with the extension of elves which are the luminous counterpart of the effects of lightning in the ionosphere.

Penetration of lightning MF signals to the upper ionosphere over VLF ground‐based transmitters

The MF data recorded by the low‐altitude satellite DEMETER have been used to survey the MF waves around the Earth. A global map of the MF emissions indicates that there exists a wave activity in the frequency range 2–2.5 MHz above the main powerful VLF ground‐based transmitters operating in the frequency range 18–50 kHz. It is shown that this is due to the high‐frequency part of whistlers induced by the thunderstorm activity. They can penetrate trough the ionosphere at the locations of the transmitters because these transmitters induce large ionospheric perturbations. This means that an integrated map over several months is able to show these MF emissions above all main VLF transmitters. The discrepancy between intensities of the emissions in winter and summer (in the Northern Hemisphere) is explained by considering the geographic variations of the plasma frequency below the satellite. It is shown that the MF waves spread in longitude in the hemisphere opposite to the VLF transmitters.

Simultaneous Determination of 2-Furfural and 5-Methyl-2-furfural Using Corona Discharge Ion Mobility Spectrometry

A novel technique, corona discharge ion mobility spectrometry (CD-IMS), was developed for the qualitative and quantitative determination of 2-furfural (F) and 5-methyl-2-furfural (MF) in aqueous solutions. The limits of detection (LODs) were 5.3 x 10(-3) microg/mL for F and 6.7 x 10(-3) microg/mL for MF. The linear dynamic ranges of 1.16 x 10(-2) to 1.04 microg/mL and 2.20 x 10(-2) to 1.10 microg/mL were obtained for F and MF, respectively. The relative standard deviation was below 12% for both compounds. In addition to analysis of the individual compound, simultaneous determination of F and MF was also investigated. It was realized that F imposes a matrix effect on the MF signal and vice versa. The standard addition method was used to deal with the matrix effect. The recovery of the compounds in the synthetic samples validates the capability of the method.

Interrelationship between the polarization moments of different parity upon optical pumping of atoms under the magnetic resonance conditions: I. Experiment on the 133Cs and 4He atoms

In an experiment with an optical pumping of 133Cs atoms in the 62S1/2 ground state, the line shape of the D2f magnetic resonance signal for the transverse alignment component oscillating at a double frequency f of a radio-frequency (RF) magnetic field is found to strongly depend on the polarization of pumping radiation. On passage from a linearly polarized pumping light to a circularly polarized (CP) light with a sufficiently strong RF field the ordinary three-peak line with the highest central peak transforms into a two-peak line with a minimum at the center, so that the D2f signal line resembles the Mf signal line of a transverse orientation oscillating at the RF field frequency f. This suggests that the orientation (the first-rank polarization moment (PM)) arising upon CP pumping affects the alignment (the second-rank PM); i.e., the PMs of Cs atoms with different parities of their ranks become coupled. No influence of the polarization of a pumping radiation on the line shape of the D2f signal is observed in a similar experiment with the 4He atoms in the 23S1 metastable state.

The effects of a triazole fungicide, propiconazole, on pollen germination, tube growth and cytoskeletal distribution in Tradescantia virginiana

The effects of propiconazole on germination and tube growth of Tradescantia virginiana pollen when incorporated in germination media at 0, 102, 136, or 170 μl l−1 were evaluated using light microscopy and immunocytochemistry. Propiconazole inhibited pollen germination, cytoplasmic streaming, and tube elongation. Treatments also induced abnormal tube morphology and cytoskeletal distribution. Tubes treated with propiconazole displayed weaker microfilament (Mf) signals along the pollen tubes, with amorphous staining. Microtubule (Mt) distribution was also severely affected. In treated tubes, the proximal portions had characteristically fragmented Mts. Fewer Mt bundles were seen in the subapical region, and these were located further from the apex. Propiconazole effects were generally concentration dependent. The results indicate that propiconazole affects both Mfs and Mts; however, the effects may be an indirect result of the drug's influence on membranes.

The role of ducted whistlers in the precipitation loss and equilibrium flux of radiation belt electrons

New experimental evidence suggests that every ducted whistler component may precipitate bursts of radiation belt electrons into geomagnetically conjugate ionospheric regions. Strong spatial and temporal associations are seen between transient ionospheric disturbances observed in conjugate regions and ducted whistlers monitored at Palmer Station, Antarctica. The ionospheric disturbances were detected by their characteristic perturbing effects (“Trimpi events”) on subionospheric VLF, LF, and MF signals recorded at Palmer Station and at northern hemisphere sites. Of 74 such events examined on four different days, all were time‐associated with ducted whistlers. In no case was the arrival azimuth or dispersion of the associated whistlers inconsistent with the locations of the conjugate ionospheric disturbances, which were inferred from the configuration of perturbed signal paths. Other whistlers occurring independently of detected disturbances were found to be either weak or to have arrived from regions where a disturbance would not have been detected for lack of monitored signal paths. Signal perturbation onset behavior was consistent with multiple regions of precipitation induced by components of multipath whistlers and with theoretical predictions for ducted whistler‐induced precipitation. The results not only support the hypothesis that ducted whistlers are responsible for burst precipitation of energetic electrons but imply that such bursts may be induced by every ducted whistler component. Since radio energy from a lightning discharge can excite whistler ducts located 2500 km or more away from the flash, every ducted whistler observed at Palmer Station may indicate the presence of precipitation bursts associated one‐to‐one with excited whistler ducts distributed over a 5000‐km‐wide portion of the Earth's surface, and over its geomagnetic conjugate as well. The estimated effect of this precipitation on 70‐ to 200‐keV radiation belt electron populations for 2 < L < 3 is comparable to that predicted as a result of plasmaspheric hiss, indicating that ducted whistlers may contribute as significantly as hiss to radiation belt equilibrium at those electron energies.

Correlation of nighttime MF signal strength with solar activity.

Observations of the signal strength of MF broadcasting signals (774/770kHz) transmitted from Akita, Japan, on board the Japanese antarctic ice breaker Fuji, bound from Japan to Syowa station, Antarctica, have revealed an interesting positive correlation between strengths of long distance signals propagating at night and solar activity. It is already known that MF propagation characteristics in North America show a negative correlation with solar activity. In the present paper, we have tried to interpret the results of the measurements on board Fuji by using the multi-hop method with the full wave analysis. The difference in correlation with solar activity between the results of Fuji and those in North America can be elucidated if we assume that there is a ledge in the electron density profile around an altitude range of 85 to 90km and that the density of the ledge is smaller in the North American region than in the equatorial region.

Physiological determinant of hunger, satiation, and satiety

The initiation and cessation of feeding behavior is explained on the basis of the ischymetric hypothesis (from ISCHYROS meaning "Mighty One" or power). Cellular production of power or "Metabolisme de Fond" (MF) is measured continuously in terms of total body metabolism minus the metabolic costs of locomotion. A drop in MF signals the onset of eating. Eating initiates a rise in MF and when this signal peaks, the feeding process stops. Control of satiation is described in terms of recent neurophysiologic and neuroendrologic factors that influence MF.

Perturbations of subionospheric LF and MF signals due to whistler‐induced electron precipitation bursts

First evidence of whistler‐induced burst precipitation effects on subionospherically propagating signals in the LF and MF ranges have been observed at Palmer (L ∼ 2.4) and Siple stations (L ∼ 4.3), Antarctica. The occurrence rate on a 37.2‐kHz LF signal originating in California was usually comparable to that on the more disturbed VLF paths. At Palmer, examples at 37.2 kHz were seen on 70% of the nights during a March‐April 1983 observing period. Perturbations on a ∼1800 km‐long 780‐kHz MF path to Palmer occurred on nights of high activity on VLF paths, but fewer than 10 MF events were usually detected as compared to >50 on the active VLF paths. The MF perturbations were of order 50% in amplitude and were not in general followed by a ∼30‐s decay toward a pre‐event level, as is usually the case for the VLF signals. Test particle modeling of the whistler‐particle interaction supports the idea that the MF signals are affected by ionization extending above the nominal ∼85‐km reflection height for VLF signals and also are consistent with the observed time delay between the 780‐kHz signal perturbation and the whistler‐generating lightning stroke. Fast phase advances correlated with the whistlers were regularly observed on a 12.9‐kHz Omega signal. The data provide a means of inferring the existence of multiple precipitation regions and offer new evidence that whistlers originating in the northern hemisphere can cause significant precipitation in the southern hemisphere, at least in the vicinity of the South Atlantic magnetic anomaly.

Uniformly spaced field‐aligned ionization ducts

MF and HF radio wave signals transmitted from topside sounders can often become trapped in magnetic‐field‐aligned ionization ducts located approximately vertically below the satellite. The resulting traces observed on ionograms are called combination mode traces. A number of cases of combination mode traces observed with the ISIS topside sounders were studied for passes over mid‐ and low‐latitude regions which exhibited distinguishable, nearly uniformly spaced traces on the ionograms typical of this type of propagation in the frequency range above 1 MHz. Associated extraordinary vertical and ducted traces were also evident in all cases. The ducted trace is interpreted as due to propagation in a duct encompassing the satellite at the time of measurement, whereas the combination mode traces are interpreted as due to ducts located well below the satellite. The simultaneous presence of a ducted trace and combination mode traces suggests the presence of a parallel system of ducts that are field aligned. On interpreting the ionograms for events studied by ray tracing, it was found that the ducts are separated by as much as 70 km transverse to their field alignment. The data indicate that, at times, the ducts may exist down to the F peak and may extend into the conjugate region as well. A multiplicity of ducts with such large, relatively uniform separations was not previously appreciated, and the mechanism for creating them in this fashion is not clear. One possibility for the even spacing of these irregularities is that they result from acoustic gravity waves at lower altitudes. Possible relationships to other geophysical phenomena, particularly equatorial phenomena, are discussed.

On the Reception of MF and HF Broadcast Signals in Atmospheric Radio Noise

The problem of estimation of suitable broadcast signal strength in the MF and HF bands for satisfactory reception in the presence of atmospheric radio noise is examined, with specific reference to the tropical problem. Simple procedures are indicated to estimate the required signal strength on the basis of the available noise data, to obtain the specified system performance.

Geomagnetic Influence on Sky Wave Propagation of MF Signals

The sky wave propagation of MF signals is provided by ordinary wave as the extraordinary wave is heavily absorbed. Hence, the efficiency with which this wave is excited determines the additional losses in this process and so the sky wave field at any distance. For any polarization of the incident wave, this efficiency is primarily a function of geomagnetic dip and the direction of propagation. A theoretical study of this aspect shows that in the case of vertical polarization, which is used for MF transmissions, the losses are abnormal in the case of E-W propagation at low latitudes as compared to N-S direction. The losses in N-S direction are in general small and do not vary much with latitude unlike losses in E-W direction. So these directional differences are comparatively small at higher latitudes. Experimental investigation of this phenomenon has been conducted recently in the Research Department of All India Radio at different latitudes and the results are in general agreement with theoretical expect...

Some observations of MF and HF radio signals after mid-pacific high-altitude nuclear explosions

Abstract Observations on certain medium-frequency transmissions after nuclear explosions show that they were affected by both short-term and long-term ionospheric absorption phenomena. Observations on high-frequency radio stations indicate a shorter period of absorption, and in some instances an enhancement in reception at the higher end of the HF spectrum.