Micro-Ring Resonator-Based Tunable Vortex Beam Emitter

Light beams bearing orbital angular momentum (OAM) are used in various scientific and engineering applications, such as microscopy, laser material processing, and optical tweezers. Precise topological charge control is crucial for efficiently using vortex beams in different fields, such as information encoding in optical communications and sensor systems. This work presents a novel method for optimizing an emitting micro-ring resonator (MRR) for emitting vortex beams with variable orders of OAM. The MRR consists of a ring waveguide with periodic structures side-coupled to a bus waveguide. The resonator is tunable due to the phase change material Sb2Se3 deposited on the ring. This material can change from amorphous to crystalline while changing its refractive index. In the amorphous phase, it is 3.285 + 0i, while in the transition to the crystalline phase, it reaches 4.050 + 0i at emission wavelength 1550 nm. We used this property to control the vortex beam topological charge. In our study, we optimized the distance between the bus waveguide and the ring waveguide, the bending angle, and the width of the bus waveguide. The optimality criterion was chosen to maximize the flux density of the radiated energy emitted by the resonator. The numerical simulation results proved our method. The proposed approach can be used to optimize optical beam emitters carrying OAM for various applications.

Neuromorphic Photonics Circuits: Contemporary Review

Neuromorphic photonics is a cutting-edge fusion of neuroscience-inspired computing and photonics technology to overcome the constraints of conventional computing architectures. Its significance lies in the potential to transform information processing by mimicking the parallelism and efficiency of the human brain. Using optics and photonics principles, neuromorphic devices can execute intricate computations swiftly and with impressive energy efficiency. This innovation holds promise for advancing artificial intelligence and machine learning while addressing the limitations of traditional silicon-based computing. Neuromorphic photonics could herald a new era of computing that is more potent and draws inspiration from cognitive processes, leading to advancements in robotics, pattern recognition, and advanced data processing. This paper reviews the recent developments in neuromorphic photonic integrated circuits, applications, and current challenges.

A Review on Photonic Sensing Technologies: Status and Outlook

In contemporary science and technology, photonic sensors are essential. They may be made to be extremely resistant to some physical parameters while also being extremely sensitive to other physical variables. Most photonic sensors may be incorporated on chips and operate with CMOS technology, making them suitable for use as extremely sensitive, compact, and affordable sensors. Photonic sensors can detect electromagnetic (EM) wave changes and convert them into an electric signal due to the photoelectric effect. Depending on the requirements, scientists have found ways to develop photonic sensors based on several interesting platforms. In this work, we extensively review the most generally utilized photonic sensors for detecting vital environmental parameters and personal health care. These sensing systems include optical waveguides, optical fibers, plasmonics, metasurfaces, and photonic crystals. Various aspects of light are used to investigate the transmission or reflection spectra of photonic sensors. In general, resonant cavity or grating-based sensor configurations that work on wavelength interrogation methods are preferred, so these sensor types are mostly presented. We believe that this paper will provide insight into the novel types of available photonic sensors.

Enhancing the Performance of the Photonic Integrated Sensing System by Applying Frequency Interrogation

Lab-on-a-chip systems are currently one of the most promising areas in the development of ultra-compact sensor systems, used primarily for gas and liquid analysis to determine the concentration of impurities. Integrated photonics is an ideal basis for designing "lab-on-a-chip" systems, advantageous for its compactness, energy efficiency, and low cost in mass production. This paper presents a solution for "lab-on-a-chip" device realization, consisting of a sensor and an interrogator based on a silicon-on-insulator (SOI) integrated photonics platform. The sensor function is performed by an all-pass microring resonator (MRR), installed as a notch filter in the feedback circuit of an optoelectronic oscillator based on an electro-optic phase modulator. This structure realizes the frequency interrogation of the sensor with high accuracy and speed using a conventional single-mode laser source. The system sensitivity for the considered gases is 13,000 GHz/RIU. The results show that the use of frequency interrogation makes it possible to increase the intrinsic LoD by five orders. The proposed solution opens an opportunity for fully integrated implementation of a photonic "laboratory-on-a-chip" unit.

Environmental Monitoring: A Comprehensive Review on Optical Waveguide and Fiber-Based Sensors

Globally, there is active development of photonic sensors incorporating multidisciplinary research. The ultimate objective is to develop small, low-cost, sensitive, selective, quick, durable, remote-controllable sensors that are resistant to electromagnetic interference. Different photonic sensor designs and advances in photonic frameworks have shown the possibility to realize these capabilities. In this review paper, the latest developments in the field of optical waveguide and fiber-based sensors which can serve for environmental monitoring are discussed. Several important topics such as toxic gas, water quality, indoor environment, and natural disaster monitoring are reviewed.

[Computer modeling of information processing mechanisms in the olfactory system. III. Reproduction of psychophysical phenomena by the olfactory bulb model]

Psychophysical phenomena typical of olfaction were reproduced using a computer model of olfactory bulb. The procedure of numerical experiments is described. The model reproduces the following phenomena: fusion of odors, strong and weak odors, suppression of weak odors by strong odors, indemnity of odors, changes in odor with time, consecutive olfactory images, sensibilization, consecutive olfactory constrast, and synergims. It was concluded that computer-assisted experimentation in combination with neurophysiological and psychophysical experiments can considerably increase the efficiency of research of odorants and the olfaction process.

[Computer modeling of mechanisms of the information processing in the olfactory bulb. II. Mechanisms of identification and short-term storage in the olfactory bulb: results of the computer experimentation]

The results of experimentation with the computer model of the olfactory bulb are presented. The architecture and scenario of the work of the model were described previously. The dynamic character of the identification process and the mechanism of memorizing short-term of smell stimuli are described. During the identification, a self-adjustment of the olfactory bulb to incoming signals occurs. The self-modification of mitral and tufted cell synapses enhances responses of the cells; upon subsequent presentation of the stimulus, the olfactory bulb responds with a higher activity. The modeling confirmed the validity of the assumption that the functions of mitral and tufted cells are to identify the components of a complex smell and the image of the smell as the whole.

[Computer modeling of mechanisms of the information processing in the olfactory bulb. I. Model of the structure-functional organizations of neuronal elements in the olfactory bulb and receptor epithelium]

A computer model of the olfactory bulb was constructed. The paper describes: 1) the general architecture of a model neuron network that reflects the neurophysiological experimental and theoretical data on the structural and functional organization of the peripheral part of the olfactory system, the olfactory bulb with inputs from olfactory receptor neurons; 2) the organization of each of three levels of the model: receptors, olfactory glomeruli, and basic neurons; and 3) a scenario of the computer model work. In some aspects, in particular, in the principle of information presentation, the treatment of the role of basic neurons (mitral and tufted cells), and their interrelations in modules, the model favorably differs from the available olfactory bulb models. The model is basic and provides further refinement of the architecture, an increase in the number of modules, and the modeling of the learning process.

[Organization of the input influence in a computer model of the olfactory system]

A computer model of the assumed odor environment and an algorithm of simulating the input influence are proposed. Concentration, volume, and quality of odorant are used as the modeling parameters of the olfactory stimulus.

[Chemiluminescence and triboluminescence of the endothelium of the thoracic aorta in gamma-irradiated rabbits with experimental hypercholesterolemia]

A comparative study of chemiluminescence and triboluminescence of endothelium of the thoracic aorta in the intact rabbits and in ones with experimental hypercholesterolemia 3, 6, 24 hours after single total influence of low doses of ionizing radiation allowed us to conclude that higher fluctuation of the examined parameters is characteristic feature of the rabbits with hypercholesterolemia. At the same time it was found that the changes in chemiluminescence and triboluminescence of endothelium of the thoracic aorta three hours after irradiation with a dose of 0.25 Gy were different in the experiments in vitro and in vivo.

[Activation of free-radical processes as a factor of ionizing radiation-induced changes in contractile activity of a vascular wall]

The influence of ionizing irradiation (1, 2 and 4 Gy 137Cs) on both the activity of free-radical processes in plasma, formed elements and aorta wall as well as on the character of contractile vascular reactions of isolated rings of thoracic aorta and carotid artery in rabbits has been studied. The experiments were carried out on the 7th day after the whole-body irradiation. The results indicate that simultaneously with the weakening of antioxidant mechanisms both endothelium-dependent and endothelium-independent vascular wall relaxation slightly decreases after 1 Gy exposure. Noradrenaline and KCI-induced contraction is shown to increase. However, these changes are not statistically significant. Irradiation in dose of 2 and 4 Gy considerably decreases endothelium-dependent relaxation. Nitroglycerin-induced relaxation greatly diminishes, KCI- and noradrenaline-induced constriction considerably increases in these conditions. The level of activation of free-radical processes considerably increases too. Thus, already on the 7th day after irradiation significant changes in reactivity of vascular wall are developed. Radiation injures both endothelium and vascular smooth muscle cells. The free-radical processes seem to be the main cause of radiation vascular damage, so there is a pronounced correlation between the changes of vascular contractile properties and the degree of activation of these processes.

[The activity of mitochondrial enzymes in the myocardium in chronic coronary failure during the administration of antianginal agents]

The experiments with Chinchilla rabbits indicated that the activity of mitochondria-associated enzymes changed hetero-directionally in chronic coronary insufficiency. The activity of creatine kinase changed most greatly. Obsidan and finoptin were found to show a different effect on the activity of the tested enzymes in the cardiac mitochondria during experimental coronary insufficiency.

[The data from clinical, instrumental and laboratory studies as markers in the prognosis of the restabilization process in patients with a history of unstable stenocardia]

With the purpose of preventing the development of acute clinical ischemic lesions of the myocardium, and their further progression, regression of coronary atherosclerosis the authors followed up for more than one year 250 patients with unstable stenocardia and singled out two groups of these patients, each group having important differences as to coronary reserve, functional state of the myocardium, lipid spectrum, dynamics of vasoactive substances, immunological reactivity, thrombocytic activity. Early detection of groups with an unfavourable course of IHD in patients with unstable stenocardia will allow to optimize treatment and avoid development of acute coronary catastrophies.

[Creatine kinase in subcellular components of the rabbit myocardium during experimental obstruction of the coronary circulation]

Acute myocardial ischemia (intravenous 0.2 U/kg vasopressin infusion) is shown to cause various changes in the creatine kinase isoenzyme activity: it decreases in mitochondria and sarcoplasmic reticulum and increases in myofibrils and cytosol, no significant alterations taking place in sarcolemma. It may be suggested that the stated changes are important components of the complex adaptational reactions which occur in the ischemic myocardium and support its main contractional function.

Antioxidants as antiarrhythmic drugs

Experiments on rats and rabbits using models of arrhythmias induced by vasopressin, epinephrine, strophanthin, and CaCl2 showed that antioxidants derived from 1,4-dihydropyridines, dibunol, and alpha-tocopherol possessed antiarrhythmic effects. Administration of these antioxidants decreased the occurrence of extrasystoles, disturbances of atrioventricular conductivity and ventricular fibrillation. These drugs also prevented changes in membrane phospholipid composition, inhibited activation of peroxidation, decreased phospholipase activity, prevented a decrease of Ca2+ ATPase and Ca2+ binding and uptake by sarcoplasmic reticulum, and increased sarcolemmal Na+, K+-ATPase, sarcoplasmic reticulum creatine phosphokinase.

[Relation between the impairment of creatine kinase activity and lipid peroxidation in the membranes of heart mitochondria and sarcoplasmic reticulum in experimental ischemia]

Experiments were conducted on rabbits under conditions of acute restriction of coronary blood flow (intravenous injection of vasopressin in a dose of 0.5 U/kg) and preliminary administration (1 h before vasopressin) of PP-256-Na antioxidant preparation. The activity of creatine kinase isoenzymes bound with sarcoplasmic reticulum and mitochondria membranes were studied as well as the content of diene conjugates in these membranes and accumulation of malonic dialdehyde. It is shown that an essential decrease in the enzyme activity in the membranes occurs against a background of a considerable increase in the content of diene conjugates and accumulation of malonic dialdehyde. A preliminary administration of the antioxidant produces a pronounced protective effect on the enzyme activity.

[Incorporation of radioactive phosphorus into creatine phosphate of the rabbit myocardium in experimental coronary insufficiency]

It is shown that under conditions of experimental limitation of coronary blood flow in rabbits the intensity of radioactive label (32P) incorporation into creatine phosphate lowers essentially. This evidences for inhibition of creatine phosphorylation in mitochondria under ischemia due to a decrease in the activity of a mitochondrial isoenzyme of creatine kinase.

[Facilitation phenomenon in the accessory and main olfactory bulbs of the frog Rana temporaria]

It has been demonstrated that facilitation of orthodromic EP by paired electrical stimuli (which was observed earlier in the accessory olfactory bulb of the frog) is also realized in the main olfactory bulb. Facilitation phenomenon in both bulbs is revealed provided the conditioned EP is present before paired stimulation. The accessory olfactory bulb differs from the main one by a longer duration of facilitation. Possible nature of facilitation phenomenon is discussed. It is suggested that differentiation of the olfactory system into the main and accessory ones may be based on differences in the velocity of their activity.

[Activity of several membrane-bound creatine kinase isoenzymes in the rabbit myocardium in experimental disruption of coronary circulation]

Activity of CPK isoenzymes, bound with membranes of mitochondria and sarcoplasmic reticulum, was decreased under conditions of acute limitation of rabbit coronary circulation followed by intravenous administration of vasopressin at a dose of 0.5 un per kg of body mass. As a result of this phenomenon the efficient energy-dependent transport of calcium across the membranes of sarcoplasmic reticulum might be impaired with the subsequent development of complex alterations in functional and metabolic parameters, which are found in ischemic myocardium.

[Creatine phosphokinase activity in myocardial sarcoplasmic reticulum membranes in experimental coronary insufficiency]

Experiments on rats with acute coronary blood flow restriction (intravenous injection of vasopressin in a dose of 0.5 units/kg) have shown a decrease in the activity of creatine phosphokinase (CPK) and activation of lipid peroxidation in sarcoplasmic reticulum (SPR) membranes. These changes were attended by structural abnormalities in the membrane apparatus of the SPR, primarily on the part of the lipid composition. Pretreatment (1 h before vasopressin) of the animals with the antioxidant AV-156Na averted the development in the SPR membranes of the changes described. This evidences that the rate of peroxide reactions in the myocardium might determine in many respects the metabolic and structural supply of the cell apparatus.

[Measurement of the propagation rate of the summation action potential in the vomeronasal and olfactory nerves of Rana temporaria frogs]

It was shown that summation action potential (AP) in various points of the nerve result from summation AP in various bundles of fibres. The rate of propagation of AP in various bundles may differ rather significantly. Propagation of AP from the site of stimulation takes place with acceleration, which is presumably due to the inhibitory effect of the stimulus at the site of its application (together with the excitatory effect as well). Both nerves exhibit also supernormal phenomenon which reveals itself in the increase of the propagation rate of the second AP during stimulation by paired stimuli.

[Components of the creatine kinase system in the myocardium with experimental disturbance of coronary blood flow]

Certain key parameters of energy metabolism in a complex mechanism of energy transport in the myocardium cells were studied in experiments on dogs with dosed limitation of the coronary blood flow (by 90%) as well as in experiments on rabbits with the intravenous injection of vasopressin (0.2 units per 1 kg of mass). Animals of all groups under study revealed essential changes in the content of creatine phosphate and in the activity of creatine phosphokinase as compared with the control groups. A possible role of creatine phosphokinase is discussed in the processes of myocardium function energy supply under conditions of creatine phosphate deficiency during a slightly pronounced ischemia.

[Creatine and phosphocreatine concentrations and creatine phosphokinase activity in the hearts of dogs with restricted coronary blood flow]

Alterations in some patterns of energy metabolism, which are essential for energy transport in myocardial cells, were studied in dogs with local artificial impairment by 70% of coronary circulation. In this case activity of creatine phosphokinase and content of creatine phosphate were decreased, particularly in the ischemic zone, but creatine concentration was unaltered. Possible role of creatine is discussed not only as a regulator of systolic pressure but also as an indicator of the functional state of myocardium.

[Adrenaline and noradrenaline elimination from the blood of rats of different ages]

Elimination of adrenaline and noradrenaline from blood of adult and old rats was studied within different periods after administration of the catecholamines. Adrenaline was eliminated from blood of rats of both age groups with the similar rate; however, the time of elimination of noradrenaline was distinctly longer in old animals are compared with the adult ones. The alterations observed may be due to the effects of sympathetic system on metabolic process in various tissues in the old age.

[Catecholamine concentration and metabolism in old age]

As shown by examination in apparently healthy persons aged from 20 to 100 years and in experiments on 1--28-month-old albino rats there was a significant change with the progress of age in the content and ratio of catecholamines in the blood, various organs and the urine. The blood noradrenaline level fell considerably; Na/A coefficient also dropped sharply. Catecholamine content in the organs changed irregularly: in the kidneys it increased, in the skeletal muscles--remained unchanged, in the adrenal glands, the heart, the spleen and the liver--decreased. There was a significant reduction with the progress of age of the urinary excretion of adrenaline, noradrenaline, DOPA and vanilyl-amygdalic acid. Elemination of the intravenously injected noradrenaline from the blood of old rats was markedly delayed in comparison with that in the young animals. Depression of the COMT activity did not alter the noradrenaline level in the heart of adult and old rats. Administration of ipraside caused an increase in noradrenaline content in the heart of old rats, but failed to alter it in adult animals. It is suggested that in the catecholamine metabolism of old animals prevalence is given to the processes of oxidative desamination.