Unit Charge Research Articles

Degradable cationic polyesters via ring-opening copolymerization of valerolactones as nanocarriers for the gene delivery

The development of cationic polymers as non-viral gene vectors has been hurdled by their high toxicity, thus degradable and biocompatible polymers are urgently demanded. Herein, five polyesters (B3a-B3e) were synthesized based on the ring-opening copolymerization between α-allyl-δ-valerolactone and δ-valerolactone derivatives decorated with alkyl or alkoxyl chains of different lengths, followed by the modification with 1,5,9-triazacyclododecyl ([12]aneN3) through thiol-ene click reactions. The five polyesters effectively condensed DNA into nanoparticles. Of them, B3a with a shorter alkyl chain and B3d with more positive charged units showed stronger DNA condensing performance and can completely retard the migration of DNA at N/P = 1.6 in the presence of DOPE. B3b/DOPE with a longer alkyl chain exhibited the highest transfection efficiency in HeLa cells with 1.8 times of 25 kDa PEI, while B3d/DOPE with more positive charged units exhibited highest transfection efficiency in A549 cells with 2.3 times of 25 kDa PEI. B3b/DOPE and B3d/DOPE successfully delivered pEGFP into zebrafish, which was superior to 25 kDa PEI (1.5 folds and 1.1 folds, respectively). The cytotoxicity measurements proved that the biocompatibility of these polyesters was better than 25 kDa PEI, due to their degradable property in acid environment. The results indicated that these cationic polyesters can be developed as potential non-viral gene vectors for DNA delivery.

Robust integral backstepping controller for energy management in plugin hybrid electric vehicles

Plugin hybrid electric vehicles (PHEVs) are a suitable choice to achieve enhanced performance and reduced toxic gases. The considered PHEV consists of an integrated charging unit and a hybrid energy storage system (HESS). The proposed HESS comprises of a battery with high energy density and a supercapacitor with high power density coupled together to fulfill the load demands of the vehicle. A DC–DC buck converter with an uncontrolled rectifier has been used for an on-board and balanced charging and two bi-directional DC–DC buck-boost converters have been incorporated to ensure a smooth transition of energy. A rule-based algorithm has been employed as a supervisory controller by incorporating total power inflow and state of charge of the power sources to fulfill the load demands. Moreover, a robust integral backstepping-based nonlinear controller has been designed for the smooth execution and energy management of PHEV in terms of output voltage regulation, reference generation, and smooth tracking of current. Lyapunov stability theory has been used to ensure asymptotic stability of the PHEV. The performance of the proposed controller has been validated using simulations on MATLAB/Simulink by comparing it with the Lyapunov redesign and backstepping controllers already proposed in the literature. The robustness of the proposed controller has been verified by introducing uncertainty in the state model. Finally, the real-time applicability and effectiveness of the proposed work have been ensured using controller hardware in loop (C-HIL) test bench.

Development and Implementation of an Inpatient CAMEO© Staffing Algorithm to Inform Nurse- Patient Assignments in a Pediatric Cardiac Inpatient Unit

BackgroundNursing workload measurement systems are vital to determine nurse staffing for safe care. The Inpatient Complexity and Assessment and Monitoring to Ensure Optimal Outcomes (CAMEO©) acuity tool provides a standardized language to communicate the acuity and complexity of nursing care in the pediatric inpatient setting. Design and methodsA process improvement project was implemented on a pediatric cardiac inpatient unit to utilize the Inpatient CAMEO© tool to inform nurse-patient assignments. Development of the Inpatient CAMEO© Staffing Algorithm utilized a modified Delphi methodology. Six Delphi rounds were performed for algorithm development, addressing potential implementation barriers, educating nursing staff, piloting feasibility, and final full implementation. ResultsThe cardiac inpatient unit's charge nurses' algorithm utilization was 86% (n = 12) during the feasibility pilot. The algorithm impacted and changed 28% (n = 4) of the shifts' assignments. One-year post algorithm implementation, CAMEO© documentation rates increased from 25 to 30% to >60%. A retrospective, two-week point-prevalence analysis one-year post-implementation described adherence to the Inpatient CAMEO© Staffing Algorithm for 87% (n = 375) of the nurses' patient assignments. ConclusionsThe Inpatient CAMEO© Staffing Algorithm was developed based upon the Inpatient CAMEO© tool and the Inpatient CAMEO© Complexity Classification System to inform nurse-patient assignments and allocate nursing resources. The Inpatient CAMEO© Staffing Algorithm was feasible and sustainable for over one year following implementation at a single center's pediatric cardiac inpatient unit.

Electric Vehicles Charging Stations’ Architectures, Criteria, Power Converters, and Control Strategies in Microgrids

The usage of electric vehicles (EV) has been increasing over the last few years due to a rise in fossil fuel prices and the rate of increasing carbon dioxide (CO2) emissions. EV-charging stations are powered by existing utility power grid systems, increasing the stress on the utility grid and the load demand at the distribution side. DC grid-based EV charging is more efficient than AC distribution because of its higher reliability, power conversion efficiency, simple interfacing with renewable energy sources (RESs), and integration of energy storage units (ESU). RES-generated power storage in local ESU is an alternative solution for managing the utility grid demand. In addition, to maintain the EV charging demand at the microgrid levels, energy management and control strategies must carefully power the EV battery charging unit. In addition, charging stations require dedicated converter topologies, control strategies, and need to follow set levels and standards. Based on EV, ESU, and RES accessibility, different types of microgrid architecture and control strategies are used to ensure optimum operation at the EV-charging point. Based on the above said merits, this review paper presents different RES-connected architecture and control strategies used in EV-charging stations. It highlights the importance of different charging station architectures with current power converter topologies proposed in the literature. In addition, a comparison of microgrid-based charging station architecture with its energy management, control strategies, and charging converter controls are also presented. The different levels and types of charging stations used for EV charging, in addition to controls and connectors used, are also discussed. An experiment-based energy management strategy was developed to control power flow among the available sources and charging terminals for the effective utilization of generated renewable power. The main motive of the EMS and its control is to maximize the usage of RES consumption. This review also provides the challenges and opportunities in EV-charging, and parameters in selecting appropriate charging stations.

An 18.3-MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF): The subsystem for the magnetosheath coils.

3D asymmetric magnetic reconnection is an important investigation of the Space Plasma Environment Research Facility, which is being built as a user facility at the Harbin Institute of Technology in China. Four magnetosheath coils, which consist of Poloidal Field (labeled PF) coils and Toroidal Field (labeled TF) coils, are used to generate the magnetic field and plasma environment for the reconnecting experiment. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite the magnetosheath coils to generate the required amplitude and duration of the magnetic field. The PPS system includes the PF PPS and TF PPS, which include four sets of PPSs, respectively. Each set of PF PPS and TF PPS consists of nine modules and four modules, respectively, and each module consists of a charge and discharge unit. The PF PPS can provide a pulsed current of no less than 360 kA for the corresponding PF coil at 0.11ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.6ms. The TF PPS can provide a pulsed current of no less than 200 kA for the corresponding TF coil at 0.08ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 1.6ms. The detailed design of the PPS has been discussed in this paper, and the detailed design of the main components in the discharge unit of the PPS is also given in this paper. Finally, the discharge tests of all the PPSs are carried out to verify the design of the PPSs, and the results of the PPSs in discharge tests indicate that all the PPSs meet the design requirements.

Analysis of the Triboelectrostatic Charging Behaviour of a\xa0Synthetic Sulfidic Copper Ore

In this study, several tests were performed to analyse the triboelectrostatic charging behaviour of an artificially mixed sulfidic copper ore consisting of quartz and chalcopyrite. To check the surface charge of the pure mineral samples, they were analysed in a self-developed triboelectrostatic charging unit. After that, the artificially mixed sulfidic copper ore was sorted by using a triboelectrostatic belt separator.The objective of the study is to generate basic knowledge about the triboelectrostatic charge behaviour and furthermore the sortability by using electrostatic separation. All separation tests were carried out under controlled ambient conditions.

DNA Condensation Triggered by the Synergistic Self-Assembly of Tetraphenylethylene-Viologen Aggregates and CT-DNA.

Development of small organic chromophores as DNA condensing agents, which explore supramolecular interactions and absorbance or fluorescence-based tracking of condensation and gene delivery processes, is in the initial stages. Herein, we report the synthesis and electrostatic/groove binding interaction–directed synergistic self-assembly of the aggregates of two viologen-functionalized tetraphenylethylene (TPE-V) molecules with CT-DNA and subsequent concentration-dependent DNA condensation process. TPE-V molecules differ in their chemical structure according to the number of viologen units. Photophysical and morphological studies have revealed the interaction of the aggregates of TPE-V in Tris buffer with CT-DNA, which transforms the fibrous network structure of CT-DNA to partially condensed beads-on-a-string-like arrangement with TPE-V aggregates as beads via electrostatic and groove binding interactions. Upon further increasing the concentration of TPE-V, the “beads-on-a-string”-type assembly of TPE-V/CT-DNA complex changes to completely condensed compact structures with 40–50 nm in diameter through the effective charge neutralization process. Enhancement in the melting temperature of CT-DNA, quenching of the fluorescence emission of ethidium bromide/CT-DNA complex, and the formation of induced CD signal in the presence of TPE-V molecules support the observed morphological changes and thereby verify the DNA condensation abilities of TPE-V molecules. Decrease in the hydrodynamic size, increase in the zeta potential value with the addition of TPE-V molecules to CT-DNA, failure of TPE-V/cucurbit(8)uril complex to condense CT-DNA, and the enhanced DNA condensation ability of TPE-V2 with two viologen units compared to TPE-V1 with a single viologen unit confirm the importance of positively charged viologen units in the DNA condensation process. Initial cytotoxicity analysis on A549 cancer and WI-38 normal cells revealed that these DNA condensing agents are non-toxic in nature and hence could be utilized in further cellular delivery studies.

Improved Droop Control Strategy of Multiple Energy Storage Applications in an AC Microgrid Based on the State of Charge

Distributed energy storage technology is used to stabilize the frequency and voltage of the microgrid operating in islanded mode. However, due to the inconsistent state of charge (SoC) of the energy storage unit (ESU), the active power output of the ESU cannot be shared reasonably. On the basis of stabilizing voltage and frequency, this paper presents a power exponential function droop control (PEFDC) strategy considering the SoC. In this control strategy, the ESU is allowed to adjust the output power adaptively according to its own SoC level during discharge and reaches SoC equilibrium. Simulation models are built to compare the PEFDC strategy with conventional droop control (CDC) and power function droop control (PFDC) approaches. The simulation results illustrate the superiority of the proposed control strategy over the other two methods. Finally, the hardware-in-the-loop experiment is conducted to verify the effectiveness of the PEFDC strategy.

Entropy-based theory of thermomagnetic phenomena

We show that in the linear response approximation only entropy provides coupling between thermal and electric phenomena. The dissipationless quantum currents — magnetization, superconducting, persistent and topological edge currents — do not produce and transfer entropy and may be excluded from final formulas for thermomagnetic coefficients. The magnetization energy flux, [Formula: see text], in crossed electric and magnetic fields strongly modifies the Poynting vector in magnetic materials and metamaterials, but do not contribute to the heat current. Calculating entropy fluxes of fluctuating Cooper pairs in pure and disordered superconductors, we obtained the fluctuation Nernst coefficient proportional to [Formula: see text] ([Formula: see text] is the Fermi energy). We also introduce the thermomagnetic entropy per unit charge and derive the Nernst coefficient proportional to the difference of the thermoelectric and thermomagnetic entropies. This explains the Sondheimer cancellation and high sensitivity of thermomagnetic phenomena to correlations. In 2D superconductors, the transport entropy transferred by a vortex moving through the background formed by vortex–antivortex pairs is the configuration entropy of [Formula: see text], which strongly exceeds the intrinsic entropy of vortex core. Beyond the linear response, the nonentropic forces can lead to phenomena unexpected from thermodynamics, such as vortex attraction to the moving hot spot. Quantum currents do not transfer entropy and may be used as ideal connectors to quantum nanodetectors.

Consumer Estimates of Online Quantity Surcharge Incidence Rates

Quantity surcharges represent situations in which consumers are charged unit prices for buying large packages of a product that exceed the unit prices for smaller packages. This practice challenges the commonly held assumption that discounts rather than surcharges should be associated with larger purchase quantities. While past research has established the prevalence of this pricing practice, the degree by which consumers believe quantity surcharged to be present in the marketplace has not been empirically examined. In this study, consumer estimates of the incidence rate of quantity surcharges in online shopping environments are examined through a national survey of 522 American consumers. The effects of cognitive and demographic factors on consumers' estimates for the incidence rate of quantity surcharges are empirically examined. The findings reveal significant underestimation by consumers of the prevalence of this deceptive pricing practice. Furthermore, consumer estimates are found to be affected by cognitive style, gender, income, and prior exposure to quantity surcharges.

Two Carboxyl-Decorated Anionic Metal-Organic Frameworks as Solid-State Electrolytes Exhibiting High Li+ and Zn2+ Conductivity.

A highly electronegative carboxyl-decorated anionic metal-organic framework (MOF), (Me2NH2)2[In2(THBA)2](CH3CN)9(H2O)21 (InOF; H4THBA = [1,1':4',1″-terphenyl]-2',3,3″,5,5',5″-hexacarboxylic acid), with high-density electronegative functional sites was designed and constructed. One unit cell of InOF possesses 12 negative sites that originate from the negatively charged secondary building unit [In(COO)4]- and exposed carboxyl groups on the ligand. The abundant electronegative sites can facilitate the hopping of ions in channels and thus result in highly efficient ion conductivities for various metal ions. Our results show that Li+-loaded materials have a remarkably high ion conductivity of 1.49 × 10-3 S/cm, an ion transference number of 0.78, and a relatively low activation energy of 0.19 eV. The Na+, K+, and Zn2+ ion conductivities of InOF are 7.97 × 10-4, 7.69 × 10-4, and 1.22 × 10-3 S/cm at 25 °C, respectively.

Nonlinear optical properties of a new panchromatic series of water-soluble bicationic push-pull fluorophores

Six water-soluble bications, characterized by a symmetric A+-π-D-π-A+ structure, were synthesized and comprehensively studied for their absorption and fluorescence properties, and their nonlinear optical response. Generally, the photobehavior exhibited by the six systems was found to be dependent on the molecular dimensionality and conjugation, unveiling the role of different electron-donor (dimethoxy-phenylene vs bithiophene) and electron-acceptor (methyl-pyridinium, methyl-quinolinum, and pyrimidin-pyridinium) substituents bound in different positions (ortho/para). Steady-state measurements revealed this series as a panchromatic family of dyes with noticeable absorption and emission abilities, covering the entire visible spectrum - from the near-ultraviolet to the near-infrared spectral region. Femtosecond-resolved spectroscopy disclosed the presence of ultrafast intramolecular charge transfer processes, as also predicted by TD-DFT calculations, from the central electron-rich moiety of the molecule towards the two lateral positively charged units. Further and for the first time, a solvatochromic method was successfully applied to this kind of quadrupolar double-charged compounds in order to estimate their static and dynamic second-order hyperpolarizability coefficients. Thanks to their appreciable fluorescence capability, significant Two-Photon Absorption cross-sections were also measured for all six dyes by means of the Two-Photon Excited Fluorescence technique. These findings, together with their good water solubility, designate these eye-catching fluorophores as potential candidates for bioimaging applications.

Economic analysis and configuration design for the energy storage unit of photovoltaic virtual synchronous generator based on the inertia support and primary frequency control

With the increasing proportion of distributed generation (DG) in electrical power systems (EPSs), the lack of grid inertia and damping has posed great challenges to the stability and operation of EPSs. To address these problems, the concept of a virtual synchronous generator (VSG) has been proposed. As the physical basis of virtual inertia, the energy storage unit directly affects the performance and operating cost of the VSG. In this paper, the energy change of the energy storage unit during the frequency control process is calculated. Based on this calculation, the charge and discharge behavior of the energy storage unit can be inferred according to the VSG parameters and the frequency deviation data. Then, combined with the improved battery cycle life model, the operating cost of the energy storage unit when the VSG participates in frequency control can be obtained. Based on the data provided by the British electricity system operator (ESO), a case is studied, and the effects of the control parameters and battery rated capacity on the operating cost is analyzed. The analysis results can provide an economic reference for the parameter selection and energy storage unit capacity configuration of the VSG. Moreover, the simulation results validate the accuracy and efficiency of the proposed method.

Power fluctuation control strategy of ship power system based on hybrid energy storage system

Objective Aiming at the problems of the power quality degradation of the power grid and the power distribution of energy storage devices when the load power of a ship power system fluctuates sharply, a power fluctuation control strategy based on the hybrid energy storage of batteries and supercapacitors is proposed. Methods First, based on the low-pass filtering algorithm, the power fluctuation of the ship's power system is initially allocated to the corresponding energy storage unit according to its fluctuation frequency. Then, based on the droop control strategy, the output current of each energy storage unit is adjusted according to the allocated power. Finally, based on the state of charge of each energy storage unit, the charge and discharge control of the hybrid energy storage system is conducted to smooth out the power fluctuations. Results The simulation results show that this power distribution strategy realizes the reasonable distribution of power between energy storage units and the charge and discharge power control of the energy storage system, which can effectively smooth out the load power fluctuations of the ship's power system. Conclusion The results of this study can provide valuable references for the optimal power quality design of a ship's power grid.

Design and Simulation of a 2KVA Inverter with an Overload Protector

In this research, the design and simulation of 2000VA inverter is presented. The method implemented for the design was the d.c. – a.c. inverter topologies. The d.c. – a.c. inverter circuit made use of a 555 timer, to digitally pulse the transistors on the inverter side, and the oscillating circuit, to drive the inverter. The system consists of the main inverter stage and the charging unit. These units are further subdivided into different stages. The main inverter performs the basic operation of converting the input d.c. voltage from the battery into an a.c voltage. The charging unit contains an automatic switch that charges the battery when it senses no supply from the mains. Each unit of the project was simulated individually at every different stage of the design by using a simulating software (every circuit). The waveform given at the final stage of the simulation shows that it is a modified sine wave inverter, and it successfully converts a 12V d.c. into a 220V a.c. with a load capacity of 2000VA. The inverter should be able to power the electronic device connected for a reasonable amount of hours

Symmetry mode analysis of distorted polar/nonpolar structures in A -site ordered SmBaMn2O6 perovskite

We present a comprehensive structural study of the charge-orbital ordering and magnetic phase transitions observed in the $A$-site ordered $\mathrm{SmBa}{\mathrm{Mn}}_{2}{\mathrm{O}}_{6}$ perovskite combining synchrotron radiation x-ray powder diffraction and symmetry-adapted modes analysis. In $\mathrm{SmBa}{\mathrm{Mn}}_{2}{\mathrm{O}}_{6}$, successive phase transitions in charge, spin, and lattice degrees of freedom take place with decreasing temperature at ${T}_{\mathrm{CO}1}\ensuremath{\approx}380\phantom{\rule{0.16em}{0ex}}\mathrm{K}, {T}_{\mathrm{CO}2}\ensuremath{\approx}190\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and ${T}_{\mathrm{N}}\ensuremath{\approx}250\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The main difference between the two charge-ordered phases concerns the stacking sequence along the $c$ axis, which is double for the high temperature charge-ordered phase and has led to controversy in the literature. We show that both charge-ordered phases are pseudosymmetric with respect to the ideal undistorted tetragonal structure of $A$-site ordered $R\mathrm{Ba}{\mathrm{Mn}}_{2}{\mathrm{O}}_{6}$ perovskites and lead to two nonequivalent Mn sites. However, the charge segregation stabilizes at about $0.35{e}^{\ensuremath{-}}$ in the low temperature charge-ordered phase, clearly below the nominal separation of one charge unit between ${\mathrm{Mn}}^{3+}$ and ${\mathrm{Mn}}^{4+}$ and undergoes a prominent increase in the high temperature charge-ordered phase when warming above $\ensuremath{\approx}250\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The two Mn sites are anisotropic in both charge-ordered phases but the analysis of the active modes discloses that only the low temperature charge-ordered phase displays a Jahn-Teller-like distortion for one of the Mn sites. In addition, this low temperature charge-ordered phase has polar symmetry compatible with ferroelectricity along the $a$ axis.

Ideal topological gas in the high temperature phase of SU(3) gauge theory

We show that the nature of the topological fluctuations in $SU(3)$ gauge theory changes drastically at the finite temperature phase transition. Starting from temperatures right above the phase transition topological fluctuations come in well separated lumps of unit charge that form a non-interacting ideal gas. Our analysis is based on a novel method to count not only the net topological charge, but also separately the number of positively and negatively charged lumps in lattice configurations using the spectrum of the overlap Dirac operator. This enables us to determine the joint distribution of the number of positively and negatively charged topological objects, and we find this distribution to be consistent with that of an ideal gas of unit charged topological objects.

Optimization of Static and Dynamic Charging Infrastructure for Electric Buses

The adoption of electric buses in public transport requires careful planning for the bus fleet and charging infrastructure. A mathematical model of an urban bus service was developed to support the deployment of charging infrastructure. The novelty of the model is that it incorporates infrastructure elements for both static and dynamic charging technologies at the same time. The model supports the electrification of the bus lines without route and schedule adjustments. The volume of charged energy at charging units is considered as a variable in the objective function to determine the location of charging units at minimum cost. The model was verified by a case study based on actual bus service data. It was found that the use of static chargers is more favorable if the cost of a static charging unit is less than the cost of a dynamic charger with a length of 1600 m and the charging power of static chargers is three times greater than the charging power of dynamic chargers. The relationship between charging power and the length of the dynamic charging unit was analyzed. It was noted that the use of charging power higher than 162.5 kW at dynamic charging units is not necessary.

A chance constraint approach to peak mitigation in electric vehicle charging stations

The increased penetration of plug-in electric vehicles asks for efficient algorithms to be adopted in parking lots equipped with charging units. In this paper, the peak power minimization problem for a plug-in charging station is addressed. A chance constraint approach is adopted in order to minimize the daily peak power, allowing for a tolerance on the charging service customer satisfaction expressing the probability that a vehicle leaves the station violating the agreed level of charge. Numerical simulations are provided to evaluate the performance of the proposed approach as well as to make a comparison with other techniques.

Developing Psychological Empowerment and Patient Safety Culture: A Pre-experimental Study

Aims: This study aimed to examine the development of the perceptions of the psychological empowerment and patient safety culture among Turkish nurses by implementing a training-based empowerment program for unit charge nurses.
 Methods: A pre-experimental, one-group pretest-posttest test design was used. The sample consisted of (n = 38) unit charge nurses and (n = 174) staff nurses; the program included theoretical components, group work, and individual study assignments. Data was collected using the Demographic Data Sheet, Psychological Empowerment Scale and Hospital Survey on Patient Safety Culture before, immediately after, and four months after the program. Data were analysed by percentages, repeated measures analysis of variance, and the Friedman analysis was used for the abnormally distributed data. The Cochran's Q test was used to analyze the number of events reported.
 Results: There was a statistically significant increase found in the results of the Psychological Empowerment Scale's scores on the competence and meaning subscales, the mean positive response to teamwork within the unit’s composite of Hospital Survey on Patient Safety Culture (p < 0.05), and event reporting (p < 0.001). 
 Conclusion: The results of this study suggest that creating a positive patient safety culture requires a review of the structures and processes of an organization. Creating, maintaining a desirable patient safety culture in health institutions is a long and hard process. The duration of future empowerment programs may be determined to allow for the long-term monitoring of their effects.