In vitro activity of photoactivated disinfection using a diode laser in infected root canals

OBJECTIVE To investigate the lethal activity of photoactivated disinfection (PAD) on Enterococcus faecalis (ATCC 29212) and mixed populations of aerobic or anaerobic bacteria in infected root canals using a diode laser after the application of a photosensitizer (PS). MATERIALS AND METHODS First, the bactericidal activity of a low power diode laser (200 mW) against E. faecalis ATCC 29212 pre-treated with a PS (toluidine blue) for 2 min were examined after different irradiation times (30 s, 60 s and 90 s). The bactericidal activity in the presence of human serum or human serum albumin (HSA) was also examined. Second, root canals were infected with E. faecalis or with mixed aerobic or anaerobic microbial populations for 3 days and then irrigated with 1.5% sodium hypochlorite and exposed to PAD for 60 s. RESULTS Photosensitization followed by laser irradiation for 60 s was sufficient to kill E. faecalis. Bacteria suspended in human serum (25% v/v) were totally eradicated after 30 s of irradiation. The addition of HSA (25 mg/ml or 50 mg/ml) to bacterial suspensions increased the antimicrobial efficacy of PAD after an irradiation time of 30 s, but no longer. The bactericidal effect of sodium hypochlorite was only enhanced by PAD during the early stages of treatment. PAD did not enhance the activity of sodium hypochlorite against a mixture of anaerobic bacteria. CONCLUSIONS The bactericidal activity of PAD appears to be enhanced by serum proteins in vitro, but is limited to bacteria present within the root canal.

EMI filter design of a three-phase buck-type rectifier for aircraft applications

An EMI filter for a three-phase buck-type medium power pulse-width modulation rectifier is designed. This filter considers differential mode noise and complies with MIL-STD- 461E for the frequency range of 10kHz to 10MHz. In industrial applications, the frequency range of the standard starts at 150kHz and the designer typically uses a switching frequency of 28kHz because the fifth harmonic is out of the range. This approach is not valid for aircraft applications. In order to design the switching frequency in aircraft applications, the power losses in the semiconductors and the weight of the reactive components should be considered. The proposed design is based on a harmonic analysis of the rectifier input current and an analytical study of the input filter. The classical industrial design does not consider the inductive effect in the filter design because the grid frequency is 50/60Hz. However, in the aircraft applications, the grid frequency is 400Hz and the inductance cannot be neglected. The proposed design considers the inductance and the capacitance effect of the filter in order to obtain unitary power factor at full power. In the optimization process, several filters are designed for different switching frequencies of the converter. In addition, designs from single to five stages are considered. The power losses of the converter plus the EMI filter are estimated at these switching frequencies. Considering overall losses and minimal filter volume, the optimal switching frequency is selected

New Considerations in the Input Filter Design of a Three-Phase Buck-Type PWM Rectifier for Aircraft Applications

An EMI filter for a three-phase buck-type medium power pulse-width modulation rectifier is designed. This filter considers differential mode noise and complies with MIL-STD-461E for the frequency range of 10kHz to 10MHz. In industrial applications, the frequency range of the standard starts at 150kHz and the designer typically uses a switching frequency of 28kHz because the fifth harmonic is out of the range. This approach is not valid for aircraft applications. In order to design the switching frequency in aircraft applications, the power losses in the semiconductors and the weight of the reactive components should be considered. The proposed design is based on a harmonic analysis of the rectifier input current and an analytical study of the input filter. The classical industrial design does not consider the inductive effect in the filter design because the grid frequency is 50/60Hz. However, in the aircraft applications, the grid frequency is 400Hz and the inductance cannot be neglected. The proposed design considers the inductance and the capacitance effect of the filter in order to obtain unitary power factor at full power. In the optimization process, several filters are designed for different switching frequencies of the converter. In addition, designs from single to five stages are considered. The power losses of the converter plus the EMI filter are estimated at these switching frequencies. Considering overall losses and minimal filter volume, the optimal switching frequency is selected.

Analysis and optimized design of a distributed multi-stage EMC filter for an interleaved three-phase PWM-rectifier system for aircraft applications

Different possible input filter configurations for a modular three-phase PWM rectifier system consisting of three interleaved converter cells are studied. The system is designed for an aircraft application where MIL-STD-461E conducted EMI standards have to be met and system weight is a critical design issue. The importance of a LISN model on the simulated noise levels and the effect of interleaving and power unbalance between the different converter modules is discussed. The effect of the number of filter stages and the degree of distribution of the filter stages among the individual converter modules on the weight and losses of the input filter is studied and optimal filter structures are proposed.

Temperature controlled light-emitting diode lamp for photovoltaic rural applications

In recent years, interest in light-emitting diode (LED) lighting has been growing because of its high efficacy, lifetime and ruggedness. This paper proposes a better adaptation of LED lamps to the technical requirements of photovoltaic lighting domestic systems, whose main quality criteria are reliability and that behave as voltage power supplies. As the key element of reliability in LED lamps is temperature, a solution is proposed for driving LED lamps using voltage sources, such as photovoltaic system batteries, with a control architecture based on pulse width modulation signal that regulates the current applied according to the LED lamp temperature. A prototype of the LED lamp has been implemented and tested to show its good performance at different temperatures and at different battery voltages.

Boolean logic device done with DFB laser diode

We present simulation results on how power output-input characteristic Instability in Distributed FeedBack -DFB semiconductor laser diode SLA can be employed to implemented Boolean logic device. Two configurations of DFB Laser diode under external optical injection, either in the transmission or in the reflective mode of operation, is used to implement different Optical Logic Cells (OLCs), called the Q- and the P-Device OLCs. The external optical injection correspond to two inputs data plus a cw control signal that allows to choose the Boolean logic function to be implement. DFB laser diode parameters are choosing to obtain an output-input characteristic with the values desired. The desired values are mainly the on-off contrast and switching power, conforming shape of hysteretic cycle. Two DFB lasers in cascade, one working in transmission operation and the other one in reflective operation, allows designing an inputoutput characteristic based on the same respond of a self-electrooptic effect device is obtained. Input power for a bit'T' is 35 uW(70uW) and a bit "0" is zero for all the Boolean function to be execute. Device control signal range to choose the logic function is 0-140 uW (280 uW). Q-device (P-device)

Laser diode bistability as sensor of optical signals pameters

Laser Diodes have been employed many times as light sources on different kinds of optical sensors. Their main function in these applications was the emission of an optical radiation impinging onto a certain object and, according to the characteristics of the reflected light, some information about this object was obtained. Laser diodes were acting, in a certain way, just as passive devices where their only function was to provide the adequate radiation to be later measured and analyzed. The objective of this paper is to report a new concept on the use of laser diodes taking into account their optical bistable properties. As it has been shown in several places, different laser diodes as, for example, DFB lasers and FP lasers, offer bistable characteristics being these characteristics a function of different parameters as wavelength, light polarization or temperature. Laser Bistability is strongly dependent on them and any small variation of above parameters gives rise to a strong change in the characteristics of its non-linear properties. These variations are analyzed and their application in sensing reported. The dependence on wavelength, spectral width, input power and phase variations, mainly for a Fabry-Perot Laser structure as basic configuration, is shown in this paper.

3-Phase Rectifier System with very demanding dynamic load: Architecture analysis and control strategy

A distributed power architecture for aerospace application with very restrictive specifications is analyzed. Parameters as volume, weight and losses are analyzed for the considered power architectures. In order to protect the 3 phase generator against high load steps, an intermediate bus (based in a high capacitance) to provide energy to the loads during the high load steps is included. Prototypes of the selected architecture for the rectifier and EMI filter are built and the energy control is validated.

Interleaved multi-cell isolated three-phase PWM rectifier system for aircraft applications

Recently there has been an important increase in electric equipment, as well as, electric power demand in aircrafts applications. This prompts to the necessity of efficient, reliable, and low-weight converters, especially rectifiers from 115VAC to 270VDC because these voltages are used in power distribution. In order to obtain a high efficiency, in aircraft application where the derating in semiconductors is high, normally several semiconductors are used in parallel to decrease the conduction losses. However, this is in conflict with high reliability. To match both goals of high efficiency and reliability, this work proposes an interleaved multi-cell rectifier system, employing several converter cells in parallel instead of parallel-connected semiconductors. In this work a 10kW multi-cell isolated rectifier system has been designed where each cell is composed of a buck type rectifier and a full bridge DC-DC converter. The implemented system exhibits 91% of efficiency, high power density (10kW/10kg), low THD (2.5%), and n−1 fault tolerance which complies, with military aircraft standards.

Power Converter Topologies for a High Performance Transformer Rectifier Unit in Aircraft Applications

This paper presents some power converter architectures and circuit topologies, which can be used to achieve the requirements of the high performance transformer rectifier unit in aircraft applications, mainly as: high power factor with low THD, high efficiency and high power density. The voltage and the power levels demanded for this application are: three-phase line-to-neutral input voltage of 115 or 230V AC rms (360 – 800Hz), output voltage of 28V DC or 270V DC(new grid value) and the output power up to tens of kilowatts.

Transferencia inalámbrica de energía

El trabajo presentado en este documento se centra en la temática de la transferencia inalámbrica de energía, concretamente en aplicaciones de campo lejano, para llevar a cabo dicho trabajo nos centraremos en el diseño, implementación y medición de una rectenna operando en la banda ISM concretamente a una frecuencia de 2.45GHz, el objetivo primordial de este trabajo será analizar que parámetros intervienen en la eficiencia de conversión en la etapa de RF-DC a fin de lograr la máxima eficiencia de conversión posible. Para llevar a cabo dicho análisis se emplearán herramientas informáticas, concretamente se hará uso del software AWR Microwave Office, a través del cual se realizarán simulaciones SourcePull a fin de determinar la impedancia óptima de entrada que se le debe presentar a la etapa rectificadora RF-DC para conseguir la máxima eficiencia de conversión, una vez realizadas dichas pruebas se implementará físicamente un circuito rectenna a través del cual realizar medidas de SourcePull mediante un Wide Matching Range Slide Screw Tuner de MAURY MICROWAVE para cotejar las posibles diferencias con los resultados obtenidos en las simulaciones. Tras la fase de pruebas SourcePull se extrapolará una red de entrada en base a los datos obtenidos en las mediciones anteriores y se diseñará y fabricará un circuito rectenna con máxima eficiencia de conversión para un conjunto de valores de potencia de entrada de RF y carga de DC, tras lo cual se analizará la eficiencia del circuito diseñado para diferentes valores de potencia de RF de entrada y carga de DC. Como elemento rectificador emplearemos en nuestro trabajo el diodo Schottky HSMS-2820, los diodos Schottky se caracterizan por tener tiempos de conmutación relativamente bajos y pérdidas en directa reducidas los cual será fundamental a la hora de trabajar con niveles reducidos de potencia de RF de entrada, para implementar el circuito se empleará un substrato FR4 con espesor de 0.8mm para disminuir en la mayor medida posible las pérdidas introducidas por el dieléctrico, se analizarán diferentes posibilidades a la hora de implementar el filtro de RF a la salida del diodo rectificador y finalmente se optará por el empleo de un stub radial ya que será este el que mejor ancho de banda nos proporcione. Los resultados simulados se compararán con los resultados medidos sobre el circuito rectenna para determinar la similitud entre ambos. ABSTRACT. The work presented in this paper focuses on the issue of wireless transfer of energy, particularly applied to far-field applications, to carry out this work we focus on the design, implementation and measurement of a rectenna operating in the ISM band specifically at a frequency of 2.45GHz, the primary objective of this study is to analyze any parameter involved in the RF-DC conversion efficiency in order to achieve the maximum conversion efficiency as possible. Computer analysis tools will be used, particularly AWR Microwave Office software, in order to carry out SourcePull simulations to determine the optimal input impedance which must be presented to the rectifier stage for maximum conversion efficiency, once obtained, a rectenna circuit will be implemented to compute SourcePull measurements, and finally simulated results will be compared to measured results. Once obtained the result, an input network impedance is extrapolated based on data from previous measurements to design and implement a rectenna circuit with high conversion efficiency for a set of RF input power and DC load values , after that, the designed circuit efficiency will be analyzed for different values of RF input power and DC load. In this work a HSMS-2820 Schottky diode will be used as the rectifier , Schottky diodes are characterized by relatively low switching times and reduced direct losses, that properties will be essential when working with low RF input power levels , to implement the circuit a FR4 substrate with 0.8mm thickness is used to reduce as much as possible the dielectric losses, different possibilities to implement the RF filter to the output of the rectifier diode will be analyzed, finally we will opt for the use of a radial stub as this will provide the best bandwidth possible. The simulated results are compared with the results measured on the rectenna circuit to determine the similarity between them.

Scanning mutagenesis of the putative transmembrane segments of Kir2.1, an inward rectifier potassium channel

Structural models of inward rectifier K+ channels incorporate four identical or homologous subunits, each of which has two hydrophobic segments (M1 and M2) which are predicted to span the membrane as α helices. Since hydrophobic interactions between proteins and membrane lipids are thought to be generally of a nonspecific nature, we attempted to identify lipid-contacting residues in Kir2.1 as those which tolerate mutation to tryptophan, which has a large hydrophobic side chain. Tolerated mutations were defined as those which produced measurable inwardly rectifying currents in Xenopus oocytes. To distinguish between water-accessible positions and positions adjacent to membrane lipids or within the protein interior we also mutated residues in M1 and M2 individually to aspartate, since an amino acid with a charged side chain should not be tolerated at lipid-facing or interior positions, due to the energy cost of burying a charge in a hydrophobic environment. Surprisingly, 17 out of 20 and 17 out of 22 non-tryptophan residues in M1 and M2, respectively, tolerated being mutated to tryptophan. Moreover, aspartate was tolerated at 15 out of 22 and 15 out of 21 non-aspartate M1 and M2 positions respectively. Periodicity in the pattern of tolerated vs. nontolerated mutations consistent with α helices or β strands did not emerge convincingly from these data. We consider the possibility that parts of M1 and M2 may be in contact with water.

Flexibility of the Kir6.2 inward rectifier K+ channel pore

Interactions of sulfhydryl reagents with introduced cysteines in the pore-forming (Kir6.2) subunits of the KATP channel were examined. 2-Aminoethyl methanethiosulfonate (MTSEA+) failed to modify Cd2+-insensitive control-Kir6.2 channels, but rapidly and irreversibly modified Kir6.2[L164C] (L164C) channels. Although a single Cd2+ ion is coordinated by L164C, four MTSEA+ “hits” can occur, each sequentially reducing the single-channel current. A dimeric fusion of control-Kir6.2 and L164C subunits generates Cd2+-insensitive channels, confirming that at least three cysteines are required for coordination, but MTSEA+ modification of the dimer occurs in two hits. L164C channels were not modified by bromotrimethyl ammoniumbimane (qBBr+), even though qBBr+ caused voltage-dependent block (as opposed to modification) that was comparable to that of MTSEA+ or 3-(triethylammonium)propyl methanethiosulfonate (MTSPTrEA+), implying that qBBr+ can also enter the inner cavity but does not modify L164C residues. The Kir channel pore structure was modeled by homology with the KcsA crystal structure. A stable conformation optimally places the four L164C side chains for coordination of a single Cd2+ ion. Modification of these cysteines by up to four MTSEA+ (or three MTSPTrEA+, or two qBBr+) does not require widening of the cavity to accommodate the derivatives within it. However, like the KcsA crystal structure, the energy-minimized model shows a narrowing at the inner entrance, and in the Kir6.2 model this narrowing excludes all ions. To allow entry of ions as large as MTSPTrEA+ or qBBr+, the entrance must widen to >8 Å, but this widening is readily accomplished by minimal M2 helix motion and side-chain rearrangement.

Beacon: a light emitting diode television display.

"Supported in part by contract no. US AEC AT(11-1) 1469."