Power Density Range Research Articles

Substrate-assisted laser desorption inductively-coupled plasma mass spectrometry for determination of copper in myeloid leukemia cells

This work presents a detailed characterization of substrate-assisted laser desorption inductively coupled plasma mass spectrometry (SALD ICP-MS), a new approach in the determination of trace elements in submicrolitre volumes. SALD ICP-MS allows quantitative analysis of metals in liquid samples with defined volumes deposited onto an absorbing substrate due to complete sample desorption at relatively low laser power density. Analysis of model samples of Cu(II) showed a constant signal over a wide range of laser power density, an independence of signal on desorption modes and a wide linear dynamic range. SALD ICP-MS with its limit of detection for copper below 26 fg in submicrolitre samples was successfully applied to investigate cytotoxic effects of disulfiram in human myeloid leukemia cells U937 depending on intracellular levels of copper.

Mobile Phone Radiation Induces Reactive Oxygen Species Production and DNA Damage in Human Spermatozoa In Vitro

BackgroundIn recent times there has been some controversy over the impact of electromagnetic radiation on human health. The significance of mobile phone radiation on male reproduction is a key element of this debate since several studies have suggested a relationship between mobile phone use and semen quality. The potential mechanisms involved have not been established, however, human spermatozoa are known to be particularly vulnerable to oxidative stress by virtue of the abundant availability of substrates for free radical attack and the lack of cytoplasmic space to accommodate antioxidant enzymes. Moreover, the induction of oxidative stress in these cells not only perturbs their capacity for fertilization but also contributes to sperm DNA damage. The latter has, in turn, been linked with poor fertility, an increased incidence of miscarriage and morbidity in the offspring, including childhood cancer. In light of these associations, we have analyzed the influence of RF-EMR on the cell biology of human spermatozoa in vitro.Principal FindingsPurified human spermatozoa were exposed to radio-frequency electromagnetic radiation (RF-EMR) tuned to 1.8 GHz and covering a range of specific absorption rates (SAR) from 0.4 W/kg to 27.5 W/kg. In step with increasing SAR, motility and vitality were significantly reduced after RF-EMR exposure, while the mitochondrial generation of reactive oxygen species and DNA fragmentation were significantly elevated (P<0.001). Furthermore, we also observed highly significant relationships between SAR, the oxidative DNA damage bio-marker, 8-OH-dG, and DNA fragmentation after RF-EMR exposure.ConclusionsRF-EMR in both the power density and frequency range of mobile phones enhances mitochondrial reactive oxygen species generation by human spermatozoa, decreasing the motility and vitality of these cells while stimulating DNA base adduct formation and, ultimately DNA fragmentation. These findings have clear implications for the safety of extensive mobile phone use by males of reproductive age, potentially affecting both their fertility and the health and wellbeing of their offspring.

In vitro effect of carboplatin, cytarabine, paclitaxel, vincristine, and low‐power laser irradiation on murine mesenchymal stem cells

Mesenchymal stem cells (MSCs) are promising for use in regenerative medicine. Cytostatics can decrease, but low-power laser irradiation (LPLI) can increase the growth of MSCs. The interaction of LPLI, MSCs and cytostatics is not known. This study investigated the effect of four cytostatics (carboplatin, cytarabine, paclitaxel, vincristine), LPLI, and combination of a cytostatic drug and LPLI on murine MSCs (mMSCs). MMSCs were exposed to LPLI (660 nm diode laser; 60 mW output power; range of power density: 76-156 mW/cm(2); range of energy density: 1.9-11.7 J/cm(2)) and/or a cytostatic drug (carboplatin: 2, 10, 50; cytarabine: 0.4, 10, 50; paclitaxel: 0.4, 2, 10; vincristine: 0.02, 0.1, 0.5 microg/ml, respectively). Cell proliferation was measured after 24, 48, or 72 hours incubation. LPLI at 1.9 J/cm(2) dose increased the proliferation rate with 41% after 48 hours. However, 11.7 J/cm(2) LPLI caused 42% inhibition and cytostasis was still detectable after 72 hours. LPLI caused equivalent stimulation in single or in divided doses (3.8 vs. double 1.9 J/cm(2) in a 24-hour period). The cytotoxicity of 50 microg/ml carboplatin was eliminated, the inhibitory power of 0.1 microg/ml vincristine was attenuated by 1.9 J/cm(2) LPLI even 3 days post-treatment (attenuation >10%). The 11.7 J/cm(2) LPLI enhanced the cytotoxicity of 50 microg/ml cytarabine (from 48% to 73%) and 10 microg/ml paclitaxel (from 37% to 78%). Combination of the ineffective 0.4 microg/ml cytarabine or paclitaxel with the inhibitory 11.7 J/cm(2) LPLI exhibited stronger inhibition than the 11.7 J/cm(2) LPLI alone (69% and 69% vs. 42%). Low energy density of LPLI increases and high energy density of LPLI decreases the proliferation of mMSCs. Furthermore, LPLI can prevent or attenuate some drug's cytotoxicity and amplify others'. The result depends on the applied energy density, on the type and concentration of the cytostatics.

Nonlinear magneto-optical resonances atD1excitation ofR85bandR87bfor partially resolved hyperfineFlevels

Experimental signals of non-linear magneto-optical resonances at D1 excitation of natural rubidium in a vapor cell have been obtained and described with experimental accuracy by a detailed theoretical model based on the optical Bloch equations. The D1 transition of rubidium is a challenging system to analyze theoretically because it contains transitions that are only partially resolved under Doppler broadening. The theoretical model took into account all nearby transitions, the coherence properties of the exciting laser radiation, and the mixing of magnetic sublevels in an external magnetic field and also included averaging over the Doppler profile. Great care was taken to obtain accurate experimental signals and avoid systematic errors. The experimental signals were reproduced very well at each hyperfine transition and over a wide range of laser power densities, beam diameters, and laser detunings from the exact transition frequency. The bright resonance expected at the F_g=1 --> F_e=2 transition of Rb-87 has been observed. A bright resonance was observed at the F_g=2 --> F_e=3 transition of Rb-85, but displaced from the exact position of the transition due to the influence of the nearby F_g=2 --> F_e=2 transition, which is a dark resonance whose contrast is almost two orders of magnitude larger than the contrast of the bright resonance at the F_g=2 --> F_e=3 transition. Even in this very delicate situation, the theoretical model described in detail the experimental signals at different laser detunings.

Study on the electrical properties of ITO films deposited by facing target sputter deposition

This study examined the mechanism for the change in the electrical properties (carrier concentration (n) and mobility (μ)) of tin-doped indium oxide (ITO) films deposited by magnetron sputtering in a confined facing magnetic field. The relationship between the carrier concentration and the mobility was significantly different from the results reported for ITO films deposited by other magnetron sputtering processes. The lowest resistivity obtained for ITO films deposited in a confined facing magnetic field at low substrate temperatures (approximately 120 °C) was 4.26 × 10−4 Ω cm at a power density of 3 W cm−2. Crystalline ITO films were obtained at a low power density range from 3 to 5 W cm−2 due to the increase in the substrate temperature from 120 to 162 °C. This contributed to the increased carrier concentration and decreased electrical resistivity. X-ray photoelectron spectroscopy revealed an increase in the concentration of the Sn4+ states. This was attributed to the formation of a crystalline ITO film, which effectively enhanced the carrier concentration and reduced the carrier mobility.

Comparison Between The Characteristics Of Wind Power Calculation And Solar Radiation At Onne

Data on wind speed and global solar radiation over the period 1985 – 1999 for Onne obtained from the International Institute of Tropical Agriculture (IITA) stationed at Onne, Nigeria have been compiled and evaluated, to determine the wind power which is compared with the global solar radiation energies. Monthly and annual data for global solar radiation energies measured at the station were determined. The monthly average solar radiation energies range from 2777.80 Wm-2 to 4163.92 Wm-2 with an overall average as 3455.58 Wm-2. The derived monthly and annual average wind speeds range from 0.84 ms-1 to 1.09ms-1 and from 0.64ms-1 to 1.28ms-1 respectively. The monthly available wind power density and maximum extractable wind power range from 0.33 Wm-2 to 1.40 Wm-2 and 0.20 Wm-2 to 1.10 Wm-2, respectively. Keywords: Characteristics, wind power, solar radiation.Global Journal or Pure and Applied Sciences Vol. 14 (4) 2008: pp. 463-466

Manganese oxide based materials for supercapacitors

AbstractManganese oxides, as an environmentally friendly material with various oxidation states, have a long history as an electrode material for batteries. Recently, a new energy storage system, supercapacitor, with its unique power density and energy density range, has been put in the focus. With a vast number of ongoing researches in exploring the MnOx as the electrode materials for supercapacitors, this article provides a comprehensive review on the recent findings in this area. Different approaches to synthesise and the electrochemical behaviours of various forms of pure and composite MnOx were presented. Important parameters that can influence the electrochemical behaviour of manganese oxides based materials are summarised. The state of the art of engineering of MnOx into composites or specific nanostructures with improved electrochemical performance is reviewed. A brief survey on the performance of symmetric and hybrid supercapacitors with MnOx as electrode material is given and appropriate cell co...

Laser-induced photoprocesses in solutions and films of the CdSe/ZnS nanoparticles

The photophysical properties of solutions and films with relatively high concentrations of CdSe/ZnS nanoparticles are studied in the presence of the visible laser irradiation in a wide range of power densities. The short-wavelength wing detected in the photoluminescence spectra of the solutions of quantum dots is due to the selective laser excitation of small-size nanoparticles. A comprehensive analysis of the anti-Stokes photoluminescence of the nanoparticles in solutions and films indicates the thermal mechanism of this phenomenon. The dimensional quantization effect, narrow spectra, and a relatively high luminescence yield are retained in the films with a high nanoparticle concentration. The luminescence spectra of the films remain unchanged when the laser flux density increases to 1 × 106 W/cm2. The effect of the laser radiation on the nanoparticle films is studied at the flux densities exceeding the damage threshold (5 × 106–1 × 109 W/cm2).

Torque Ripple Reduction of Interior Permanent Magnet Synchronous Motor Using Harmonic Injected Current

Interior permanent magnet synchronous motor (IPMSM) is widely used for many industrial applications such as power train, compressor and home appliances due to its high power density and wide speed range. However, IPMSM have relatively high torque ripple in comparison with surface mounted permanent magnet motor. In case of IPMSM, d-axis current should be fed to use reluctance torque, and the more d-axis current is needed as the motor speed goes up. Therefore, back electromotive force (EMF) of IPMSM contains much harmonics and torque ripple tend to increase as the motor speed increase. This paper proposes a method to reduce torque ripple using harmonic injected current. Firstly dominant harmonic order of back EMF is investigated then under the consideration of harmonics, torque ripple using harmonic injected current will be compared with that of sinusoidal current by finite element analysis.

Resistor Emulation Approach to Low-Power RF Energy Harvesting

This paper presents an approach and associated circuitry for harvesting near maximum output power from electromagnetic waves in the RF/microwave region of the spectrum with variable incident power densities in the range of tens of muW/cm2. It is shown that open loop resistor emulation at the input port of a power converter is a suitable solution for tracking the peak power point of a low-power rectifying antenna source over a wide range of incident RF power densities. A boost converter with a simple low-power control approach for resistor emulation is presented. A hardware design example with detailed efficiency analysis is given using commercially available discrete circuitry. Experimental results are presented for a system harvesting 420 muW to 8 muW from a 6 cm times 6 cm rectifying antenna with incident RF power ranging from 70 muW/cm2 to 30 muW/cm2, respectively. The results demonstrate that resistor emulation is a simple and practical approach to energy harvesting with variable low-power radiative RF sources.

Tin laser-produced plasma source modeling at 13.5nm for extreme ultraviolet lithography

Extreme ultraviolet lithography semiconductor manufacturing requires a 13.5nm light source. Laser-produced plasma emission from Sn V–Sn XIV ions is one proposed industry solution. The effect of laser pulse width and spatial profile on conversion efficiency is analyzed over a range of power densities using a two-dimensional radiative magnetohydrodynamic code and compared to experiment using a 1.064μm, neodymium:yttrium aluminium garnet laser on a planar tin target. The calculated and experimental conversion efficiencies and the effects of self-absorption in the plasma edge are compared. Best agreement between theory and experiment is found for an 8.0ns Gaussian pulse.

10.1007/s11823-008-1003-3

The mechanisms of erosion of metal surfaces under the action of submicrosecond (10−9−10−6 s) ion beams in the power density range of P = 106−109 W/cm2 with a particle energy of 1–2000 keV are considered. It is shown that the collective processes associated with the radiation heating of the surface are of great importance. A model for the erosion is proposed. In accordance with this model, the flow of atoms of the target leaving the surface being irradiated consists of two independent components caused by collisional sputtering and evaporation, respectively. The influence of the irradiation parameters on the erosion coefficient and the ratio between the sputtering and evaporation factors is analyzed.

Photosensitive properties of Perylene–Oxazine films, solution-deposited on doped silicon

Liquid phase deposition of chlorobenzene solutions containing Perylene and Oxazine, is used to grow films made of quasi-parallel wire-like microstructures. Films form, when deposited on n-doped monocrystalline silicon wafers, photosensitive heterojunctions with a spectral response that closely resembles Perylene–Oxazine absorption. Photoelectric properties of the heterojunctions are investigated employing current versus voltage measurements, which are performed in the dark and under white light with a power density range of 0.1 mW/cm 2 to 1.0 mW/cm 2.

The increase in longitudinally measured sleepiness across adolescence is related to the maturational decline in low-frequency EEG power.

A changing sleep schedule that reduces sleep duration is thought to produce the increasing daytime sleepiness of adolescents. We tested the hypothesis that adolescent daytime sleepiness also results from adolescent brain maturational processes indexed by declining delta electroencephalographic (EEG) activity. Data are from the first 3 years of a semilongitudinal study of EEG changes in adolescence. All-night EEG was recorded semiannually. EEG was recorded with ambulatory recorders in the subjects' homes. Thirty-one subjects were 9 years old (cohort C9), and 38 subjects were 12 years old (cohort C12) at the start of the study. EEG power density (power/minute) was calculated for the first 5 hours of non-rapid eye movement sleep. Subjects rated sleepiness on a modified Epworth Sleepiness Scale. Habitual sleep schedules were assessed with self-reports and actigraphy. In C9 subjects, sleepiness increased slightly and was related only to age. In C12 subjects, the increase in subjective sleepiness was related to changes in age, bedtime, time in bed, and a wide frequency range of EEG power density. Sleepiness was not related to rise time, non-rapid eye movement sleep duration, rapid eye movement sleep duration, or total sleep time. With sleep schedule measures statistically controlled, the increase in sleepiness in the C12 group was strongly related to declining delta power density and, unexpectedly, even more strongly related to declining theta power density. The data support our hypothesis that, independent of sleep schedule changes, increasing adolescent daytime sleepiness is related to brain maturational changes indexed by declining EEG power. Our working hypothesis is that the declines in delta and theta power are correlates of an adolescent synaptic pruning that reduces waking arousal levels.

Optical emission studies of nitrogen plasma generated by IR CO2 laser pulses**In Memoriam: Professor Antonio Pardo Martinez.

Large-scale plasma produced in nitrogen gas at room temperature and pressures ranging from 4 × 103 to 1.2 × 105 Pa by high-power laser-induced dielectric breakdown (LIDB) has been investigated. Time-integrated optical nitrogen gas spectra excited from a CO2 laser have been measured and analysed. The spectrum of the generated plasma is dominated by the emission of strong N+ and N and very weak N2+ atomic lines and molecular features of N+2(B2Σ+u–X2Σ+g), N+2(D2Πg–A2Πu), N2(C3Πu–B3Πg) and very weak N2(B3Πg–A3Σ+u). The relative intensities of the 0–0 band heads in the N2(C–B) and N+2(B–X) systems are very weak as compared with the chemiluminescence spectrum of nitrogen formed in a glow discharge. An excitation temperature Texc = 21 000 ± 1300 K was calculated by means of the relative intensity of ionized nitrogen atomic lines assuming local thermodynamic equilibrium. Optical breakdown threshold intensities in N2 at 9.621 µm have been determined. The physical processes leading to the LIDB of nitrogen in the power density range 0.4 < J < 4.5 GW cm−2 have been analysed. From our experimental observations we can suggest that, although the first electrons must appear via multiphoton ionization or natural ionization, electron cascade is the main mechanism responsible for the LIDB in nitrogen.

Laser-induced breakdown spectroscopy of trisilane using infrared CO2 laser pulses

The plasma produced in trisilane (Si3H8) at room temperature and pressures ranging from 50to103Pa by laser-induced breakdown (LIB) has been investigated. The ultraviolet-visible-near infrared emission generated by high-power IR CO2 laser pulses in Si3H8 has been studied by means of optical emission spectroscopy. Optical breakdown threshold intensities in trisilane at 10.591μm for laser pulse lengths of 100ns have been measured as a function of gas pressure. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited atomic H and Si and ionic fragments Si+, Si2+, and Si3+. An excitation temperature Texc=5600±300K was calculated by means of H atomic lines assuming local thermodynamic equilibrium. The physical processes leading to LIB of trisilane in the power density range 0.28GWcm−2&amp;lt;J&amp;lt;3.99GWcm−2 have been analyzed. From our experimental observations we can propose that, although the first electrons must appear via multiphoton ionization, electron cascade is the main mechanism responsible for the breakdown in trisilane.

Performance of solid alkaline fuel cells employing anion-exchange membranes

For the performances of solid alkaline fuel cells (SAFCs) using anion-exchange membranes (AEMs), anion-exchange membranes were prepared via chloromethylation and amination of polysulfone and membrane-electrode assemblies (MEAs) were fabricated using the AEMs as an electrolyte, the ionomer binder prepared by the AEMs and Pt/C and Ag/C electrocatalysts as an anode and a cathode, respectively. Anion-exchange membranes were aminated by a mixing amine agent of trimethylamine (TMA) as a monoamine and various diamines such as N, N, N′, N′-tetramethylmethanediamine (TMMDA), N, N, N′, N′-tetramethylethylenediamine (TMEDA), N, N, N′, N′-tetramethyl-1,3-propandiamine (TMPDA), N, N, N′, N′-tetramethyl-1,4-butanediamine (TMBDA) and N, N, N′, N′-tetramethyl-1,6-hexanediamine (TMHDA). Amination using various diamines enabled to investigate the effect of the length of alkyl chain of the diamines on membrane properties such as ion conductivity and thermal characteristics. The AEMs aminated by the amination agent of mixing TMA and TMHDA (with longer alkyl chain) showed better hydroxyl ion conductivity and thermal stability than those aminated by a diamine. The H 2/air SAFC performance of the MEA with 0.5 mg cm −2 Pt/C at the anode and the cathode, respectively, was comparable to one with 0.5 mg cm −2 Pt/C at the anode and 2.0 mg cm −2 Ag/C at the cathode, i.e., approximately 28–30 mW cm −2 of the peak power density range.

Energy vs Power Relationship for Lithium Ion Cells over a Broad Range of Temperatures and Power Densities

We provide an analysis of batteries subject to controlled power operation on both charge and discharge over the temperature range of , consistent with vehicle drive events. The method we develop is applied to a high-power lithium ion cell, thereby allowing us to obtain parameters and overall characteristics useful for representing the battery in vehicle models and providing a quantitative means of comparing and classifying battery systems. The current and voltage histories are modeled during the constant power discharge, and Ragone plots (energy vs power) as well as discharge and charge times are analyzed. The equations employed are based on an equivalent circuit comprising a parallel resistor-capacitor combination in series with a resistor and the open-circuit potential source. The circuit element values are dependent on temperature and independent of the current and potential. Model calculations are compared with experimental data. Good agreement is obtained for temperatures ranging from 0 to . More work is needed to clarify phenomena below .

Visible Luminescence Related to Defects in ZnO

AbstractWe studied several photoluminescence (PL) bands in undoped, Li-, Ga-, and N-doped high-quality ZnO bulk crystals and thin films grown by molecular beam epitaxy (MBE). By analyzing PL in a wide range of excitation power densities, sample temperature, and decay time after a laser pulse, we distinguished and analyzed more than 10 broad bands with unique luminescence properties. Among these bands, only the Cu-related green band with a characteristic fine structure and the Li-related orange band were well-studied and reliably identified in the past.

Effects of Thin Film Layers on Actuating Performance of Microheaters

We investigated effects of thin film layers on actuating performance of microheaters. Bubble behaviors on microheaters were observed experimentally, and heat conduction characteristics in thin film layers were analyzed numerically. Nine kinds of tantalum nitride (TaN) microheaters were prepared. Step-stress test showed that voltage limits of nonpassivated heaters were <50% of those of passivated heaters. Open pool bubble test was carried out using deionized water as a working fluid. Nonpassivated heaters produced comparable bubbles with only 20-50% of input energy required for passivated heaters. However, nonpassivated heaters could be operated only in a narrow range of driving voltage. We constructed a hybrid model for bubble nucleation prediction correlating nucleation times with driving powers. Based on work of bubble formation estimated from bubble volume evolution, actuation efficiencies of microheaters were calculated and compared. Efficiencies of nonpassivated heaters were much higher than those of passivated heaters. However, nonpassivated heaters failed to show robust actuating characteristics over a wide range of power density. As promising microactuators, nonpassivated heaters need further investigation from a viewpoint of reliability.