Internal Modulator Research Articles

Construction of the mathematical model of magnetic transmission for an autonomous wind power plant

The object of research is electromagnetic and mechanical processes in magnetic transmission for an autonomous wind power plant of small power. The use of magnetic transmission as part of an autonomous wind power plant makes it possible to improve the reliability and efficiency of such a system. In the current work, a study of magnetic transmission as part of an autonomous wind power plant was carried out to investigate the parameters and characteristics of magnetic transmission. This paper reports the construction of a numerical simulation mathematical model of a magnetic reducer operating as part of an autonomous wind power plant with a permanent magnet generator. The model takes into account discrete structure of internal and external rotors and modulator; changes in model parameters when input parameters change. It also takes into account losses, change of load angle and electromagnetic moment; the effect of changing the generator load. The built model of the magnetic reducer system differs in that the change in the generator load leads to a shift of the operating point on the mechanical characteristics of the rotor of the wind power plant (WPP). The model also works in the opposite direction: changes in wind parameters affect power, voltage, current, and electromagnetic moment. With the help of the model built, the parameters and characteristics of not only the magnetic reducer but also other components of the system were investigated. The efficiency at the output of the electric generator was determined, which is ≈75 % at a load of 2.0 kW. The magnetic transmission moment at a wind speed of 7.8 m/s for the high-speed rotor is 0.91 N∙m, and the low-speed rotor is 7.8 N∙m, which corresponds to a transmission ratio of 8.6. This expands opportunities for exploratory research

Interferometer-based chemical sensor on chip with enhanced responsivity and low-cost interrogation

We report experimental results of an interferometric chemical sensor integrated on a silicon chip. The sensor measures refractive index variations of the liquid that contacts exposed spiraled silicon waveguides on one branch of a Mach-Zehnder interferometer. The system requires neither laser tuning nor spectral analysis, but a laser at a fixed wavelength, and a demodulation architecture that includes an internal phase modulator and a real-time processing algorithm based on multitone mixing. Two devices are compared in terms of sensitivity and noise, one at 1550 nm wavelength and TE polarization, and an optimized device at 1310 nm and TM polarization, which shows 3 times higher sensitivity and a limit of detection of 2.24·10−7 RIU.

Resonant Beam SWIPT With Telescope and Second Harmonic

Simultaneous wireless information and power transfer (SWIPT) is a prospective technology that can handle the energy consumption and communication requirements in the Internet of Things. Resonant beam SWIPT (RB-SWIPT) scheme utilizes narrow optical beam as carrier and with spatially separated resonator structure, which can support high power and high rate SWIPT for mobile devices. However, the performance of original RB-SWIPT systems is limited by returning beam interference and transmission loss. In this paper, we propose a RB-SWIPT scheme for transmission-enhanced and anti-interference. The telescope internal modulator (TIM) and second harmonic generator (SHG) are adopted in the proposed system. The TIM can compress beams to reduce the transmission loss. The SHG can generate frequency-doubled beams to avoid interference. To evaluate the proposed system, we establish mathematical models to depict the beam transmission, energy conversion, electric power output and data receiving. Numerical results illustrate that the proposed system can achieve 18 bit/s/Hz spectral efficiency and deliver 8 W power over 100 m distance.

Long-Range Optical Wireless Information and Power Transfer

Simultaneous wireless information and power transfer (SWIPT) is a remarkable technology to support both the data and the energy transfer in the era of Internet of Things (IoT). In this article, we proposed a long-range optical wireless information and power transfer system utilizing retro-reflectors, a gain medium, a telescope internal modulator to form the resonant beam, achieving high-power and high-rate SWIPT. We adopt the transfer matrix, which can depict the beam modulated, resonator stability, transmission loss, and beam distribution. Then, we provide a model for energy harvesting and data receiving, which can evaluate the SWIPT performance. Numerical results illustrate that the proposed system can simultaneously supply 0–9 W electrical power and 18-bit/s/Hz spectral efficiency over 20-m distance.

PENGEMBANGAN MODUL PRAKTIKUM UNTUK MODULATOR OPTIK INTERNAL DAN EKSTERNAL

The optical modulator is a component used to convert information signals into a carrier signal in theform of a light beam. 3 optical modulators are widely used, namely the internal modulator, the machzehndermodulator (MZM), and the electro-absorption modulator (EAM). Each optical modulator hasadvantages and disadvantages, but in general, the purpose of an optical modulator is to modulatelight beams. The purpose of this study was to determine the performance comparison of the internaland external optical modulator and the feasibility of the practicum module. The method used is tosimulate an optical modulator on a fiber-optic network using Optisystem software. The networkfeasibility parameters analyzed were Q-factor, BER, and eye diagram until performance reached theITU-T G.984.2 standard with a minimum limit of Q-factor = 6 and BER 10-9. The optical modulatorchanges internal and external variables. The feasibility test of the practicum module uses the methodof filling out a questionnaire with a Likert scale of 1–5 and giving pre-test and post-test to thepractitioner. The comparison of optical modulator performance shows that MZM performance is betterthan EAM and internal modulator. In the bit rate test, the transmission distance used is 65 km, andsignal power of +7 dBm MZM is capable of sending bit rates of up to 27 Gbps. In testing thetransmission distance, the bit rate used is 10 Gbps, and signal power of +7 dBm MZM can cover adistance of up to 70 km. In the signal power test, the bit rate used is 10 Gbps and the transmissiondistance is 65 km MZM capable of working at +5 dBm signal power. This practicum module is veryfeasible as teaching material according to the percentage of the practitioner's assessment of 88.2%.

Midkine rewires the melanoma microenvironment toward a tolerogenic and immune-resistant state.

An open question in aggressive cancers such as melanoma is how malignant cells can shift the immune system to pro-tumorigenic functions. Here we identify midkine (MDK) as a melanoma-secreted driver of an inflamed, but immune evasive, microenvironment that defines poor patient prognosis and resistance to immune checkpoint blockade. Mechanistically, MDK was found to control the transcriptome of melanoma cells, allowing for coordinated activation of nuclear factor-κB and downregulation of interferon-associated pathways. The resulting MDK-modulated secretome educated macrophages towards tolerant phenotypes that promoted CD8+ T cell dysfunction. In contrast, genetic targeting of MDK sensitized melanoma cells to anti-PD-1/anti-PD-L1 treatment. Emphasizing the translational relevance of these findings, the expression profile of MDK-depleted tumors was enriched in key indicators of a good response to immune checkpoint blockers in independent patient cohorts. Together, these data reveal that MDK acts as an internal modulator of autocrine and paracrine signals that maintain immune suppression in aggressive melanomas.

Flow-modulated targeted signal enhancement for volatile organic compounds.

Comprehensive two-dimensional gas chromatography is a technique that is becoming more widespread within the analytical community, especially in the separation of complex mixtures. Modulation in comprehensive two-dimensional gas chromatography can be achieved by manipulating temperature or flow and offers many advantages such as increased separation power, but one underutilized advantage is increased detectability due to the reduction of peak width from the use of a modulator. A flow modulator was used to selectively target analytes for increased detectability with a standard flame ionization detector operated at 100 Hz, without the need for cryogens or advanced modulation software. By the collection of the entire peak volume followed by peak transfer rather than further separation, an increase of 12 times in peak height and detectability was realized for the analytes tested using an internal loop modulator configuration. An external loop flow modulator configuration allowed for more volatile analytes (with k < 5), and demonstrated an analyte detectability enhancement factor of at least 6. The collection loop size can be readily increased with an external loop configuration to accommodate for these naturally broader peaks.This novel flow modulated targeted signal enhancement approach was applied to industrially significant analyses like the analysis of methanol in a hydrocarbon streams. Methanol was detected at 7 ppb with a conventional flame ionization detector and without the need for pre-concentration.

Fusarium oxysporum f.sp. ciceri race 1 induced redox state alterations are coupled to downstream defense signaling in root tissues of chickpea (Cicer arietinum L.).

Reactive oxygen species are known to play pivotal roles in pathogen perception, recognition and downstream defense signaling. But, how these redox alarms coordinate in planta into a defensive network is still intangible. Present study illustrates the role of Fusarium oxysporum f.sp ciceri Race1 (Foc1) induced redox responsive transcripts in regulating downstream defense signaling in chickpea. Confocal microscopic studies highlighted pathogen invasion and colonization accompanied by tissue damage and deposition of callose degraded products at the xylem vessels of infected roots of chickpea plants. Such depositions led to the clogging of xylem vessels in compatible hosts while the resistant plants were devoid of such obstructions. Lipid peroxidation assays also indicated fungal induced membrane injury. Cell shrinkage and gradual nuclear adpression appeared as interesting features marking fungal ingress. Quantitative real time polymerase chain reaction exhibited differential expression patterns of redox regulators, cellular transporters and transcription factors during Foc1 progression. Network analysis showed redox regulators, cellular transporters and transcription factors to coordinate into a well orchestrated defensive network with sugars acting as internal signal modulators. Respiratory burst oxidase homologue, cationic peroxidase, vacuolar sorting receptor, polyol transporter, sucrose synthase, and zinc finger domain containing transcription factor appeared as key molecular candidates controlling important hubs of the defense network. Functional characterization of these hub controllers may prove to be promising in understanding chickpea–Foc1 interaction and developing the case study as a model for looking into the complexities of wilt diseases of other important crop legumes.

Ultrashort pulse generation using fiber FM laser

Ultrashort optical pulse generation using a fiber FM laser is presented and analyzed in detail. Fiber FM laser operation is realized using a fiber ring with an internal phase modulator and an erbium-doped fiber amplifier. To compress FM laser pulses, an external dispersive single-mode fiber is employed. Furthermore, by external intensity modulation, the pulse background is removed. The background ratio of the generated ultrashort pulse is calculated and compared with the experimental results. The experimental results show an output optical pulse width of 1.77 ps and a spectral bandwidth of 0.5 THz.

The Structure‐Based Design of Mdm2/Mdmx–p53 Inhibitors Gets Serious

The p53 protein is the cell's principal bastion of defense against tumor-associated DNA damage. Commonly referred as a "guardian of the genome", p53 is responsible for determining the fate of the cell when the integrity of its genome is damaged. The development of tumors requires breaching this defense line. All known tumor cells either mutate the p53 gene, or in a similar number of cases, use internal cell p53 modulators, Mdm2 and Mdmx proteins, to disable its function. The release of functional p53 from the inhibition by Mdm2 and Mdmx should in principle provide an efficient, nongenotoxic means of cancer therapy. In recent years substantial progress has been made in developing novel p53-activating molecules thanks to several reported crystal structures of Mdm2/x in complex with p53-mimicking peptides and nonpeptidic drug candidates. Understanding the structural attributes of ligand binding holds the key to developing novel, highly effective, and selective drug candidates. Two low-molecular-weight compounds have just recently progressed into early clinical studies.

Focus on magnetics and electromagnetism

Focus on magnetics and electromagnetism

Optical Pulse Storage, Shaping, and Wavelength Conversion in Resonators With Controllable Input Coupling

By controlling the coupling coefficient into a small optical resonator, the energy of an incoming pulse can be completely captured and stored within the cavity. This paper describes the conditions for complete energy capture and shows that this transfer is relatively robust to various deviations from ideal conditions. Once captured inside the optical resonator, the energy can be released with an arbitrary delay and pulse shape by again controlling the resonator coupling coefficient. In addition, the wavelength of the output pulse can be shifted through the use of an internal cavity-phase modulator. Applications of these effects will be important in the design of future optical storage and buffering devices.

Tuning of a Neuronal Calcium Sensor

Recoverin is a Ca(2+)-regulated signal transduction modulator expressed in the vertebrate retina that has been implicated in visual adaptation. An intriguing feature of recoverin is a cluster of charged residues at its C terminus, the functional significance of which is largely unclear. To elucidate the impact of this segment on recoverin structure and function, we have investigated a mutant lacking the C-terminal 12 amino acids. Whereas in myristoylated recoverin the truncation causes an overall decrease in Ca(2+) sensitivity, results for the non-myristoylated mutant indicate that the truncation primarily affects the high affinity EF-hand 3. The three-dimensional structure of the mutant has been determined by x-ray crystallography. In addition to significant changes in average coordinates compared with wild-type recoverin, the structure provides strong indication of increased conformational flexibility, particularly in the C-terminal domain. Based on these observations, we propose a novel role of the C-terminal segment of recoverin as an internal modulator of Ca(2+) sensitivity.

DRUGS PREVENTING Na+AND Ca2+OVERLOAD

Cardiac intracellular Na+and Ca2+homeostasis is regulated by the concerted action of ion channels, pumps and exchangers. The Na+, K+-ATPase produces the electrochemical concentration gradient for Na+, which is the driving force for Ca2+removal from the cytosol via the Na+/Ca2+exchange. Reduction of this gradient by increased intracellular Na+concentration leads to cellular Ca2+overload resulting in arrhythmias and contractile dysfunction. Na+and Ca2+overload-associated arrhythmias can be produced experimentally by inhibition of Na+efflux (digitalis-induced intoxication) and by abnormal Na+influx via modulated Na+channels (veratridine, DPI 201-106; hypoxia) or via the Na+, H+exchanger. Theoretically, blockers of Na+and Ca2+channels, inhibitors of abnormal oscillatory release of Ca2+from internal stores or modulators of the Na+, Ca2+and Na+, H+exchanger activities could protect against cellular Na+and Ca2+overload.Three exemplary drugs that prevent Na+and Ca2+overload, i.e. the benzothiazolamine R56865, the methylenephenoxydioxy-derivative CP-060S, and the benzoyl-guanidine Hoe 642, a Na+, H+exchange blocker, are briefly reviewed with respect to their efficacy on digitalis-, veratridine- and ischaemia/reperfusion-induced arrhythmias.

Ureogenesis in Indian air-breathing teleosts: adaptation to environmental constraints

Most of the Indian air-breathing teleosts are primarily ammoniotelic, but appear to have retained the genes for the urea cycle enzymes, since a full complement of urea cycle enzymes have been reported for many of them. The ability to synthesize urea by these fish is probably due to their amphibious nature, and their normal habitat of swamps, where the water ammonia level may to be quite high, is uninhabitable to any typical freshwater teleosts. One of these air-breathing species, the singhi catfish ( Heteropneustes fossilis), can tolerate very high ambient total ammonia concentrations (up to 75 mM ammonium chloride) for weeks without any deleterious effects. Transition from ammoniotelism to ureotelism occurs in some of these species of air-breathing fish when exposed to apparently stressful conditions such as higher ambient ammonia, to air, and also when they live in semidry condition inside mud during habitat drying. Although the real mechanism(s) of regulation of ureogenesis is not clear in these fish, given available data, it is hypothesized that the accumulation of ammonia within the body per se under the above stressful conditions is likely the internal modulator for enhanced ureogenesis mainly to avoid any build up of ammonia to a level that can be toxic to these fish. An active urea cycle is believed to predominate over uricolysis as a source of urea, even though both pathways are present in these air-breathing fish. The presence of significant levels of both carbamyl phosphate synthetase (CPS), CPS I-like and CPS III activities, reported in some air-breathing catfishes, may represent intermediate scenarios for a proposed evolutionary transition from CPS III to CPS I, or may play an important physiological adaptive role in the tolerance of these fish to high concentrations of ambient ammonia

Modulation of residual current in a modulated Bayard-Alpert gauge

The modulation of the residual current in a Bayard-Alpert ion gauge (BAG) was studied in conditions where a positive ion current resulting from the electron bombardement of a gas layer adsorbed on the grid (the ESD-current) was a major component of the residual current. Measurements were carried out with BAG with an internal modulator and a closed grid in a UHV system. The collector current vs emission current curves were measured with the modulator at both the grid and collector potentials separately at a raised pressure of electronically desorbable gases. An analysis, according to Lavson's theory, was used to obtain the ESD-current as a function of the emission current. The modulation factor of the ESD-current computed from these results was found to be as high as 80% of the modulation factor of the gas-phase ion current. Since the modulation factor of the ESD-current is so close to that of the gas-phase ion current the modulated BAG cannot measure pressure reliably when the electronegative gases such as O 2 or CO are present in a vacuum system.

New high accuracy pulse width modulation based digital-to-analogue convertor/power amplifier

A new high accuracy pulse width modulation based digital-to-analogue convertor is presented. It is suitable for high power applications as well as ordinary low power use. While possessing important advantages, previously proposed convertors of this type have been difficult to realise in hardware and/or have exhibited high distortion. In this paper, digital signal processing (DSP) techniques are used to facilitate hardware implementation and increase performance. Specially designed oversampled noise shaping networks allow reductions in internal modulator clock speed large enough to make a 16 bit quality implementation possible. Also, new premodulation, predistortion DSP algorithms of varying complexity and accuracy are employed to reduce the harmonic distortion inherent to the modulation process typically used. Computer simulations are presented to verify the improvements.

Effects of divalent cations on the activation of a calcium-dependent potassium channel in hippocampal neurons.

The activation of a calcium-dependent K+ channel K(Ca) in cultured hippocampal neurons has been studied after the addition, to the internal solution, of the divalent cations magnesium (Mg2+), strontium (Sr2+) or barium (Ba2+). With physiological K+ across inside-out patches and Ca2+ present at 0.2 mM in the bath solution, a 90-pS channel was activated with an open probability in excess of 75%. When the internal Ca2+ was reduced to levels near 5 microM, the channel-open probability was significantly diminished. However, if 0.2 mM concentrations of either Mg2+ or Sr2+ were added to the internal solution, the open probability was increased to a value close to original level. In the presence of internal Ca2+ at 0.1 microM, the K(Ca) channel was not active and was not activated with the addition of 0.2 mM Mg2+ or Sr2+ to the internal solution. Thus, Mg2+ or Sr2+ were not able to active K(Ca) in the absence of Ca2+; however, both of these divalent cations could potentiate the Ca(2+)-induced activation of K(Ca) if internal Ca2+ was near 5 microM. The results indicate that Mg2+ could have a role as an internal modulator of K(Ca) in the Ca(2+)-dependent regulation of excitability in nerve membrane. Replacement of Ca2+ with Ba2+, or addition of Ba2+ to Ca-containing solutions, caused significant decreases in the channel-open probability for K(Ca). The action of Ba2+ was primarily mediated by a decrease in the frequency of channel opening. At a concentration of 5 microM, Ba2+ diminished the channel-open probability by one-half.

High frequency attenuated total internal reflection light modulator

The modulation efficiency and bandwidth limitations of a new type of light modulator, the attenuated total internal reflection modulator (ATRM), are described. The ATRM is based on coupling a light beam to a surface plasmon wave, and its fabrication is compatible with GaAs integrated circuit technology. We demonstrate modulation to 22 GHz (the extrapolated 1.5 dB optical modulation bandwidth is 26 GHz) and show that devices with high modulation index can be built using existing materials.

Thapsigargin: An internal calcium modulator and antiarrhythmic agent in the isolated perfused rat heart

Thapsigargin: An internal calcium modulator and antiarrhythmic agent in the isolated perfused rat heart