Information flow, Gating, and Energetics in dimeric molecular motors

Molecular motors belonging to the kinesin and myosin super family hydrolyze ATP by cycling through a sequence of chemical states. These cytoplasmic motors are dimers made up of two linked identical monomeric globular proteins. Fueled by the free energy generated by ATP hydrolysis, the motors walk on polar tracks (microtubule or filamentous actin) processively, which means that only one head detaches and executes a mechanical step while the other stays bound to the track. Thus, the one motor head must regulate chemical state of the other, referred to as "gating", a concept that is not fully understood. Inspired by experiments, showing that only a fraction of the energy from ATP hydrolysis is used to advance the kinesin motors against load, we demonstrate that additional energy is used for coordinating the chemical cycles of the two heads in the dimer - a feature that characterizes gating. To this end, we develop a general framework based on information theory and stochastic thermodynamics, and establish that gating could be quantified in terms of information flow between the motor heads. Applications of the theory to kinesin-1 and Myosin V show that information flow occurs, with positive cooperativity, at external resistive loads that are less than a critical value, Fc. When force exceeds Fc, effective information flow ceases. Interestingly, Fc, which is independent of the input energy generated through ATP hydrolysis, coincides with force at which the probability of backward steps starts to increase. Our findings suggest that transport efficiency is optimal only at forces less than Fc, which implies that these motors must operate at low loads under in vivo conditions.

Comparative Analysis of a Three Phase Inverter with Different Loads

DC–AC inverters play a crucial factor in the modern era to satisfying the demand of energy conversion, which is definitely for a better lifestyle and developing smart facilities. In this paper a deeper study has been taken place to understand the behavior of the inverter base on three phase bridge inverters. The scenarios for the inverters respectively with pure resistive loads R and inductive resistive loads RL are both discussed. The term load is referring to the brushless DC motor (BLDC) which is more reliable than regular or permanent magnet DC motors, this study will help to understand the effect of these components in the inverters. These effects could be related to friction and other electrical problem such as spark which they are associated with the DC components’ operation. Moreover, solving differential equations numerically using powerful software such as MTLAB, which certainly solidify the comprehension of the system operation. The inverter was simulated using MATLAB as a variable DC and AC power supply to in investigate the effect of varying the parameters of the reference input signals such as carrier frequency, duty cycle and the output load such as inductance. Finally, a flowchart of the system is included described both hardware and software.

Getting Ready for Beyond-5G, Super-IoT and 6G at Hardware Passive Components Level – A Multi-State RF-MEMS Monolithic Step Attenuator Analyzed up to 60 GHz

Looking at 2030, the landscape of technology will be dominated by paradigms like 6G, Super-IoT (Internet of Things) and Tactile Internet (TI). From the perspective of Hardware (HW) components technologies, the turning into reality of such scenarios will demand for a radical reconceptualization of devices, sub-systems and systems, probably modifying the concept of HW itself. Driven by the target of taking initial steps in the direction of such future applications, this work discusses a 4 bit RF power step attenuator entirely realized in RF-MEMS technology. Physical samples are fabricated in a surface micromachining technology and rely on electrostatically actuated cantilevered MEMS ohmic switches to select or short resistive loads placed along the RF line. Fabricated devices are tested and validated up to 30 GHz, while simulations are discussed up to 60 GHz for the full set of allowed configurations. Despite a few technology non-idealities, the network shows levels of attenuation with a flatness as good as 1 dB over 60 GHz frequency span. The measured and simulated data reported in this work offer important indications on how to improve the network concept, both at technology and design level.

Sensorless Adaptive Voltage Control for Classical DC-DC Converters Feeding Unknown Loads: A Generalized PI Passivity-Based Approach

The problem of voltage regulation in unknown constant resistive loads is addressed in this paper from the nonlinear control point of view for second-order DC-DC converters. The converters’ topologies analyzed are: (i) buck converter, (ii) boost converter, (iii) buck-boost converter, and (iv) non-inverting buck-boost converter. The averaging modeling method is used to model these converters, representing all these converter topologies with a generalized port-Controlled Hamiltonian (PCH) representation. The PCH representation shows that the second-order DC-DC converters exhibit a general bilinear structure which permits to design of a passivity-based controller with PI actions that ensures the asymptotic stability in the sense of Lyapunov. A linear estimator based on an integral estimator that allows reducing the number of current sensors required in the control implementation stage is used to determine the value of the unknown resistive load. The main advantage of this load estimator is that it ensures exponential convergence to the estimated variable. Numerical simulations and experimental validations show that the PI passivity-based control allows voltage regulation with first-order behavior, while the classical PI controller produces oscillations in the controlled variable, significantly when the load varies.

Efficient Power Response Characteristics of 2KVA Low Cost Inverter under Resistive Loads and Inductive Loads

The paper discussed the design of low cost inverter using SG3525A IC and IRF3205 MOSFET in H-Bridge configuration. The implementation of the real construction involved the use of IC SG3525A for generation of output pulses; the totem pole arrangement of transistors was used in the driver section of the inverter to boost signals as well as switching purposes. The H-bridge configuration was employed to effectively switch the four MOSFETs, this switching produced an alternating potential of 220V. Pre-set conditions such as load condition, low battery cut, overcharge cut and constant output were set at 1700W, 10V, 13.3V and 220V respectively so as to ensure effective and long lasting usage of the inverter. The battery used for the operation of the inverter was 12V maintenance free battery in order to reduce the cost of using the inverter. The various tests carried out on this inverter were tests on inductive loads, resistive loads, home appliances, overload condition, low battery and charging control. The aim of this work is to achieve inverter design analysis under resistive loads and inductive loads for efficient power usage at lowest possible cost. This was achieved by connecting various resistive and inductive loads on the inverter. The results show that the system can operate under both the resistive and inductive loads but operates better under resistive loads, the reason for this is that inductive loads always draw large currents during start-ups which always result to power losses. Graphs were plotted and analyzed; the results also showed that this inverter can take up to 1700W of resistive load and inductive load of 1020W. The inverter produced no humming sound from inductive loads and home appliances such as fan, television, refrigerator e.t.c that were within its maximum capacity of 1700W.

CONDITIONED REFLEX MECHANISMS OF ADAPTATION TO ADDITIONAL BREATHING RESISTANCE

The problem of adaptation to additional breathing resistance has recently become more urgent due to the growth of bronchopulmonary diseases. Therefore, there is a natural interest in non-drug strategies compensating resistive breathing in humans. The aim of the study was to assess conditioned reflex changes in the functional state of the subjects under additional breathing resistance. Materials and Methods. The work was carried out on 55 practically healthy subjects of both sexes, aged 18–36. Additional breathing resistance was modeled by inspiratory resistive loads of 40, 60, 70, and 80 % of the maximum intraoral pressure. The conditioned respiratory reflex to resistive respiratory load was developed as a short-delayed conditioned signal with a 30-second period of isolated action. The authors examined behavioral, vegetative, gas and energy indicators of the organism before and after the formation of a conditioned reflex. Results. It was observed that conditioned reflex shifts of physiological parameters in the process of adaptation to additional breathing resistance differ significantly from the corresponding unconditioned reflex changes both in nature and in intensity. Conditioned reflex mechanisms reduce the intensity of shifts in the motor component of the external respiration system, which, apparently, is the main reason to decrease the aversive behavior. Conclusion. Behavioral changes after the formation of a conditioned respiratory reflex to additional respiratory resistance are characterized by a decrease in aversive behavior patterns. The conditioned reflex realization of increasing resistive loads is expressed in a lower physiological cost of adaptation to additional respiratory resistance relative to the unconditioned reflex type of realization. Keywords: adaptation, conditioned respiratory reflex, additional breathing resistance. Проблема приспособления к дополнительному респираторному сопротивлению в последнее время становится все более актуальной в связи с ростом бронхолегочных заболеваний. Поэтому естественен интерес к нелекарственным механизмам компенсации резистивного дыхания человека. Целью исследования являлась оценка условно-рефлекторных изменений функционального состояния испытуемых в условиях дополнительного респираторного сопротивления. Материалы и методы. Работа проведена на 55 практически здоровых испытуемых обоего пола в возрасте от 18 до 36 лет. Дополнительное респираторное сопротивление моделировалось инспираторными резистивными нагрузками величиной 40, 60, 70 и 80 % от максимального внутриротового давления. Условный дыхательный рефлекс на резистивные дыхательные нагрузки вырабатывался по типу короткоотставленного с периодом изолированного действия условного сигнала 30 с. Исследовались поведенческие, вегетативные, газовые и энергетические показатели организма до и после формирования условного рефлекса. Результаты. Показано, что условно-рефлекторные сдвиги физиологических показателей в процессе приспособления к дополнительному респираторному сопротивлению существенно отличаются от соответствующих безусловно-рефлекторных изменений как по характеру, так и по интенсивности. Условно-рефлекторные механизмы уменьшают интенсивность сдвигов моторного компонента системы внешнего дыхания, что, по-видимому, является основной причиной снижения вероятности появления аверсивного поведения. Выводы. Поведенческие изменения после формирования условного дыхательного рефлекса на дополнительное респираторное сопротивление характеризуются снижением вероятности появления аверсивных форм поведения. Условно-рефлекторная реализация возрастающих по интенсивности резистивных нагрузок выражается в меньшей физиологической стоимости приспособления к дополнительному респираторному сопротивлению относительно безусловно-рефлекторного типа реализации. Ключевые слова: приспособление, условный дыхательный рефлекс, дополнительное респираторное сопротивление.

Pathophysiological mechanisms of resistive breathing

AIM: This study aimed to explore the pathophysiological mechanisms of resistive breathing by using a model of a conditioned respiratory reflex to external resistance to breathing. MATERIALS AND METHODS: Inspiratory resistive loads were used 11, 28, 54, and 78 cmAq/l/s to model a conditioned respiratory reflex. External respiration was parametrized on the basis of the analysis of motor and ventilatory outputs. Conditioned signals were pure sounds exceeding the threshold of perception by 10 db at 2000 Hz frequency. All the test persons were divided into two groups (large and small groups) according to the initial reinforcement value. (1) In the large group (37 individuals), the conditioned reflex was formed from 11 cmAq/l/s that was subsequently increased stepwise in the load to 76 cmAq/l/s. (2) In the small group (18 individuals), the initial reinforcements were different gradations of resistive loads, with a stepwise transition to the other parameters of an unconditioned stimulus. The period of the isolated application of a conditioned signal (CS) was 20 s, the interval between signals was not fixed, varying from 2 min to 4 min. Six to eight combinations of the conditioned and unconditioned stimuli were used for 1 day of the experiment. RESULTS: The increase in the added respiratory resistance was associated with the pronounced reduction of pulmonary and alveolar ventilation, that is, with the hypoventilation type of resistive load realization. Changes in ventilation during the isolated application of a conditioned signal had an alternative character. In particular, as the reinforcement factor increased, a pronounced shift to hyperventilation was noted. CONCLUSION: The reinforcement value of the conditioned reflex changed stepwise, thereby significantly restructuring the proportion between the effectiveness of the adaptive activity in the realization of external resistance to inspiration (the time of stay under a certain load) and its physiological cost (totalities of the deviations of physiological and energy parameters).