Plant size,flowering synchrony and edge effects: What,how and where they affect the reproductive success of a Neotropical tree species

Plant reproductive success is supposedly influenced by phenology and individual size, which may be modified under edge effects. We tested if reproductive success, estimated by fruit set, in Senefeldera verticillata (Euphorbiaceae) is related to flowering synchrony and tree size, including plant height and circumference at breast height. The study was carried out in the interior and in edges of clearings for gas pipelines and electric lines of a lowland rainforest in south‐eastern Brazil. Monthly observations were performed during one reproductive season, of 19 individuals that grew at edges of electric lines and gas pipelines and at forest interior. Reproductive success was significantly higher at forest interior than at gas pipeline area; there was no significant difference between gas pipeline and electric line areas or between forest interior and electric line area. In the forest edges, only plant height was positively related to plant reproductive success. This is probably related to crown exposure to sunlight, which enhances flower production. At forest interior, reproductive success was positively influenced by the synchrony of flowering activity among neighbouring individuals. In contrast, flowering synchrony based on phenophase intensity negatively impacted reproductive success. Senefeldera verticillata shows temporal dioecy and is mainly pollinated by small social bees, and the high degree of flowering synchrony at low intensity may increase the number of mating partners and therefore enhance its reproductive success. Inside the forest fragments, individuals with thicker trunks showed lower reproductive success, which may be related to a loss of reproductive capacity of older individuals. Our results evidenced the complexity of responses experienced by tropical plants subjected to forest fragmentation because of linear clearings.     

Alkaline Fuel Cells with Novel Gortex‐Based Electrodes are Powered Remarkably Efficiently by Methane Containing 5% Hydrogen

Numerous electric and gas utilities are actively pursuing “power‐to‐gas” technology, which involves using unwanted, excess renewable energy to manufacture hydrogen gas (H₂) that is then injected into the existing natural gas pipeline network in 5–10% by volume. This work reports an alkaline fuel cell that has the potential to harness such gas mixtures for downstream generation of electric power. The fuel cell, which employs novel Gortex‐based electrodes layered with Pd/Pt catalysts, generates electricity remarkably efficiently when fuelled with methane (CH₄) containing 5% hydrogen. Methane constitutes the major component of natural gas. The fuel cell has been studied over a range of hydrogen to methane ratios using Tafel plots and electrochemical impedance spectroscopy. These show that, in terms of fundamental operation, there is, astonishingly, almost no difference between using pure hydrogen and 5% hydrogen in methane, as the fuel. The Gortex electrodes and alkaline electrolyte are clearly able to utilize the dilute hydrogen as a fuel with remarkable efficiency. The methane acts as an inert carrier gas and is not consumed.     

Assessment of exposure to intermediate frequency electric fields and contact currents from a plasma ball

While electric fields at intermediate frequencies are not widely utilized for industrial technologies, surprisingly, certain toys emit the highest electric fields found in our living environment. These toys, plasma balls, are devices that use high voltage to create ionized light discharges. In this study, we assessed exposure to electric fields and contact/induced current from a recreational plasma ball device. The electric field strength was measured as a function of distance from the device, and the contact/induced current was measured with a current clamp in different exposure situations with point or grasping contact. The characteristic spectra of the electric field and contact current were measured, and both the multiple frequency rule and weighting of the spectra were applied according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 1998 and 2010 guidelines. The results indicate that the recommended reference levels for the general public are exceeded at distances <1.2 m, and that the contact currents in the hand may be twice higher than recommended by the general public guidelines.     

Identifying plants under natural gas micro-leakage stress using hyperspectral remote sensing

Natural gas is an important clean energy source. The demand for, and consumption of, natural gas have been increasing in recent years. Slight natural gas leakage can occur during transportation, which can have a negative impact on the environment, economy, and safety. However, it is relatively difficult to directly detect natural gas microleakage. Hyperspectral remote sensing technology is useful for analyzing the spectral characteristics of vegetation near leakage areas, thereby indirectly obtaining leakage information. In this study, a field experiment was designed to simulate natural gas leakage from an underground pipeline and gas stress on three plant species. The canopy spectral reflectance of the vegetation throughout the growth period of the plants was collected and analyzed. Variational mode decomposition was then used to decompose the spectra. Based on the stress distance (SD) and intrinsic mode functions, it was found that the second intrinsic mode function, with a decomposition scale of 32, was sensitive to gas stress. According to the results of SD, the bands (616 and 829 nm) sensitive to natural gas stress for the three plant species were extracted, and the variational mode decomposition index (VMDI) was constructed. The Jeffries–Matusita distance (JMD) was used to quantitatively evaluate the VMDI index and three indices were used to evaluate the ability to recognize stress. It was found that the index proposed in this study could identify stressed wheat and grass one week earlier than other indices and could better identify stressed vegetation throughout the phenological cycle (JMD > 1.8). The results show that the proposed index can be used as a reliable method to identify natural gas-stressed plants, and that hyperspectral technology is promising for detecting the location of natural gas leaks from underground pipelines.     

Theoretical evaluation of voltage inducement on internal membranes of biological cells exposed to electric fields

Several reports have recently been published on effects of very short and intense electric pulses on cellular organelles; in a number of cases, the cell plasma membrane appeared to be affected less than certain organelle membranes, whereas with longer and less intense pulses the opposite is the case. The effects are the consequence of the voltages induced on the membranes, and in this article we investigate the conditions under which the induced voltage on an organelle membrane could exceed its counterpart on the cell membrane. This would provide a possible explanation of the observed effects of very short pulses. Frequency-domain analysis yields an insight into the dependence of the voltage inducement on the electric and geometric parameters characterizing the cell and its vicinity. We show that at sufficiently high field frequencies, for a range of parameter values the voltage induced on the organelle membrane can indeed exceed the voltage induced on the cell membrane. Particularly, this can occur if the organelle interior is electrically more conductive than the cytosol, or if the organelle membrane has a lower dielectric permittivity than the cell membrane, and we discuss the plausibility of these conditions. Time-domain analysis is then used to determine the courses of the voltage induced on the membranes by pulses with risetimes and durations in the nanosecond range. The particularly high resting voltage in mitochondria, to which the induced voltage superimposes, could contribute to the explanation why these organelles are the primary target of many observed effects.     

Influence of a transverse magnetic field on the characteristics of a dc gas discharge

The influence of a transverse magnetic field and the working-gas pressure on the rotation frequency of the current channel, as well as on the electric field in the positive column and the cathode voltage drop in a dc gas discharge, was studied experimentally. The working gases were pure hydrogen and hydrogen-methane, hydrogen-argon, and hydrogen-argon-methane mixtures. It is shown that a transverse (with respect to the discharge current) magnetic field stabilizes a normal glow discharge against a transition to an arc discharge at specific absorbed powers above 300 W/cm³. The cathode voltage drop and the electric field in the positive column are measured. It is shown that the electric field does not depend on the magnetic field strength, whereas the cathode voltage drop increases with increasing magnetic field. It is found that the rotation frequency of the current channel is a complicated function of the discharge parameters and attains 400 Hz.     

Inactivation of E. coli in Cranberry Juice by a High Voltage Pulsed Electric Field

The aim of this work was to study the effect of a high voltage pulsed electric field (PEF) on the inactivation of E. coli in cranberry juice to achieve the regulatory requirement of a 5‐log reduction in the microbial count. PEF processing involved the application of high voltage pulses to liquid or semi‐solid materials, placed between two electrodes at ambient, sub‐ambient, or supra‐ambient temperature. In this work, cranberry juice, inoculated with E. coli was subjected to 60 pulses in the voltage range of 5 to 40 kV/cm. The experiments were carried out at 20 °C. The temperature rise was less than 2 °C at the average treatment time of 80 s. PEF is an emerging non‐thermal technology for food preservation that retains the natural taste of food. It has mainly been applied to improve the shelf life of such foods as milk, liquid eggs and fruit juices.     

高压电场不可逆电穿孔诱发A549肺癌细胞凋亡的实验研究

目的：不可逆电穿孔是治疗肿瘤的新兴技术,本文探讨高压电场引起的不可逆电穿孔诱发A549肺癌细胞凋亡的特点。方法：选择处于生长周期的A549细胞,共分为A—G7个组进行研究,其中A组为不施加电场的空白对照组,B-G组为实验组,B组施加500V／cm强度高压电场,G组施加1750V／cm的高压电场,BG组之间各组的高压电场强度间隔为250V／cm。采取细胞抑制实验、不可逆电穿孔示踪实验、细胞凋亡实验,检验A549细胞细胞凋亡与电场强度的关系。结果：①各实验组与对照组、各实验组之间的细胞抑制率,均存在显著性差异（P〈0．05）;②电场强度≥1000V／cm时,细胞不可逆电穿孔率明显增加,有统计学意义（P〈0．05）;电场强度≥1500V／cm时,细胞不可逆电穿孔率增加不明显,无统计学意义（P〉0．05）;③电场强度≥1250V／cm时,细胞早期凋亡率明显增加,有统计学意义（P〈0．05）。结论：高压电场不可逆电穿孔诱发A549肺癌细胞发生早期凋亡的强度为1250V／cm,发生晚期凋亡的强度为1500V／cm,且凋亡率随着电场强度的增加持续升高。这对于高压电场不可逆电穿孔效应引起的肿瘤细胞凋亡机制的研究具有重要意义。     

Behavioral responses of weakly electric fish to complex impedances

Summary Members of the family of African electric fish, Mormyridae, exhibit a novelty response, consisting of an acceleration in the rate of electric organ discharges (EODs), when faced with changes in feedback arising from their EODs. In this study, the novelty responses of three different species of mormyrids to shunts with different electrical characteristics were noted. The three species differed in the frequency contents of their EODs: two species had relatively high spectral frequencies in their EODs (>10 kHz), while the third species had only lower spectral frequencies (< 10 kHz). Primarily resistive shunts elicited novelty response accelerations in all three species, and the magnitudes of these responses, when normalized to the responses obtained for a shunt with no introduced resistance, were comparable for all three species. For primarily capacitive shunts, however, the magnitudes of the normalized responses were different for the three species: the two species with high spectral frequencies in their EODs showed larger normalized responses than the third species which had only low EOD spectral frequencies.The differences in species responses for capacitive shunts, and the similarities in species responses for resistive shunts, suggest that electric fish detect the complex impedance of objects in their near field environment: a circuit model consisting of a fish emitting discharges into the surrounding water, which can be shunted by a variable complex impedance, conforms well to the data. Thus, electrolocation is a frequency dependent sensory process, and this frequency dependency should be considered in any speculation about the adaptive value of different EOD waveforms.Abbreviation EOD electric organ discharge     

Influence of a period of inactivity on the duration of post-rest action potentials of the mammalian working ventricular myocardium in correlation to the preceding stimulation frequency

Experiments were carried out on the working right ventricular myocardium of adult cats, guinea-pigs and rabbits. Membrane voltage was recorded by the glass microelectrode technique and the preparations were stimulated with frequencies of 5, 1 and 0.2 Hz. After a steady state had been reached, a pause (TP) lasting 10-600 s was interpolated. The influence of TP on the duration (D) of post-rest action potentials (AP) was studied; the effect of the pause was measured at electric zero level (D0) and at further repolarization levels (-20, -40 and -60 mV, given here as D-20, D-40 and D-60). At 1 and 0.2 Hz frequency, the cat myocardium displayed lengthening of the AP proportional to the duration of the pause; at 5 Hz frequency, D0 reacted by lengthening up to TP = 120 s and to further pauses by slight shortening. D-60, at all frequencies, lengthened throughout the whole of the given TP range. The rabbit myocardium, at all the given frequencies, reacted up to TP = 60-120 s by marked shortening of post-rest AP at all repolarization levels; with longer pauses the AP lengthened. At 5 Hz frequency the guinea-pig myocardium reacted similarly to the cat myocardium; at the lower stimulation frequencies, the pause-induced changes in the post-rest AP were less strongly expressed. In all the given types of myocardium, the most pronounced post-rest AP reactions were those at electric zero level (the plateau phase of the AP); towards more negative repolarization values and with lower pre-pause stimulation frequencies they were less strongly expressed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cellular spin resonance of aging yeast and mouse sarcoma cells

The way in which individual cells may be made to spin by the application of alternating electric fields is examined. The spinning of a given living cell is observed to respond rather sharply and in a resonant manner at several frequencies, hence the term "cellular spin resonance" (CSR). The frequencies of the applied field can be orders of magnitude higher than the actual spin rate. The CSR varies with the conductivity of the medium, with the square of the applied field, with the cell type and with the phase of the yeast cell life cycle. Living cells respond readily and individually are sharply resonant. Dead cells show little such response.From the behavior of the CRS in sinusoidal AC, as compared to pulsed DC, it appears likely that one cause of CSR, at least that in high frequency electric fields, is the presence of natural rf oscillations arising from the cells, and modulated by their high polarizability.     

Voltage and frequency dependence of prestin-associated charge transfer

Membrane protein prestin is a critical component of the motor complex that generates forces and dimensional changes in cells in response to changes in the cell membrane potential. In its native cochlear outer hair cell, prestin is crucial to the amplification and frequency selectivity of the mammalian ear up to frequencies of tens of kHz. Other cells transfected with prestin acquire voltage-dependent properties similar to those of the native cell. The protein performance is critically dependent on chloride ions, and intrinsic protein charges also play a role. We propose an electro-diffusion model to reveal the frequency and voltage dependence of electric charge transfer by prestin. The movement of the combined charge (i.e., anion and protein charges) across the membrane is described with a Fokker–Planck equation coupled to a kinetic equation that describes the binding of chloride ions to prestin. We found a voltage- and frequency-dependent phase shift between the transferred charge and the applied electric field that determines capacitive and resistive components of the transferred charge. The phase shift monotonically decreases from zero to −90° as a function of frequency. The capacitive component as a function of voltage is bell-shaped, and decreases with frequency. The resistive component is bell-shaped for both voltage and frequency. The capacitive and resistive components are similar to experimental measurements of charge transfer at high frequencies. The revealed nature of the transferred charge can help reconcile the high-frequency electrical and mechanical observations associated with prestin, and it is important for further analysis of the structure and function of this protein.     

Specificity of probe measurements in diffuse plasmas of dense gases in strong electric fields

The article is devoted to extending the applicability of the probe diagnostics to the range of higher pressures of the plasma-forming gas by taking into account the effect of the probe shadow on the anode. The probe current–voltage characteristic in the diffuse plasma of a dense gas in a strong electric field was measured, and the influence of the probe potential and probe current on the dimensions of the probe shadow on the anode was studied experimentally. The experiments were carried at different currents of a steady-state glow discharge and different velocities of the gas flow through the discharge. The plasma-forming gas was nitrogen at a pressure of P = 100 Torr.     

Microwave processes in the Octupole Galathea

Results are presented from experimental studies of electromagnetic emission and plasma oscillations in the plasma-frequency range in the Octupole Galathea confinement system. Experiments are performed in the electric-discharge mode at low magnetic fields (the barrier field is 0.002–0.01 T); the working gas is argon or hydrogen. It is found that the most intense microwave oscillations at frequencies of 1–5 GHz are excited near the plasma axis and in the magnetic-barrier region. The oscillations are excited by the discharge current and decay after the voltage is switched off. The experiments show that microwave oscillations excited in the magnetic-barrier region are responsible for the small value of the energy confinement time in the system.     

Human respiration at rest in rapid compression and at high pressures and gas densities

Ventilation (V), end-tidal PCO2 (PACO2), and CO2 elimination rate were measured in men at rest breathing CO2-free gas over the pressure range 1-50 ATA and the gas density range 0.4-25 g/l, during slow and rapid compressions, at stable elevated ambient pressures and during slow decompressions in several phases of Predictive Studies III-1971 and Predictive Studies IV-1975. Inspired O2 was at or near natural O2 levels during compressions and at stable high pressures; it was 0.5 ATA during decompressions. Rapid compressions to high pressures did not impair respiratory homeostasis. Progressive increase in pulmonary gas flow resistance due to elevation of ambient pressure and inspired gas density to the He-O2 equivalent of 5,000 feet of seawater was not observed to progressively decrease resting V, or to progressively increase resting PACO2. Rather, a complex pattern of change in PACO2 was seen. As both ambient pressure and pulmonary gas flow resistance were progressively raised, PACO2 at first increased, went through a maximum, and then declined towards values near the 1 ATA level. It is suggested that this pattern of PACO2 change results from interaction on ventilation of 1) increase in pulmonary resistance due to elevation of gas density with 2) increase in respiratory drive postulated as due to generalized CNS excitation associated with exposure to high hydrostatic pressure. There may be a similar interaction between increased gas flow resistance and increase in respiratory drive related to nitrogen partial pressure and the narcosis resulting therefrom.     

Induction of chemiluminescence of peritoneal exudate macrophages after exposure to an electric field

The effect of the external high voltage electric field pulses on the suspension of rat peritoneal phagocytes has been investigated using chemiluminescent and turbodimetric methods. Single electric field pulses were found to activate macrophages, which was accompanied by a "flash" of chemiluminescence. Subthreshold electric field strength up to 0.8 kV/cm failed to alter macrophage activity. Maximum activation was observed at 2.2 kV/cm; with higher electric field intensity the effect diminished to zero. Drastic changes in light-scattering suspension properties at high electric field intensity indicate irreversible alterations of the barrier function of phagocyte membranes.     

Electrorotation of colloidal particles and cells depends on surface charge.

The importance of surface conductivity to the frequency-dependent polarizability and the rotation of particles in circular electric fields (electrorotation) is emphasized by various theoretical and experimental investigations. Although surface conductivity seems to be naturally related to the ionic double layer, there is rare experimental evidence of a direct relationship. To highlight the role of surface charges in electrorotation, an apparatus was developed with a symmetrical three-electrode arrangement for field frequencies between 25 Hz and 80 MHz. The three-dimensional electrostatic field distribution between the electrodes was evaluated numerically. With this device, rotating, gradient, and homogeneous electric fields of defined precision and homogeneity could be applied to slightly conducting suspensions. Surface properties of monodisperse latex particles (O 9.67 microm), carrying weak acid groups, were characterized by suspension conductometric titration. This procedure determined the amount of carboxyl groups and showed that strong acid groups were missing on the surface of these particles. To obtain the electrophoretic mobility, the spheres were separated by free-flow electrophoresis, and the zeta-potential was calculated from these data. Single-particle rotation experiments on fractions of specified electrophoretic mobility were carried out at frequencies between 25 Hz and 20 MHz. By analyzing the pH dependence of the rotation velocity, it could be shown that the rotation rate is determined by surface charges, both at the peak in rotation rate near the Maxwell-Wagner frequency (MWF) and at low frequencies. The inversion of the rotation direction at the MWF peak for vanishing surface charges was demonstrated. An analytical model for the double layer and dissociation on a charged surface was developed that is valid for low and high zeta-potentials. This model could provide convincing evidence of the linear dependence of the MWF rotation velocity on surface charge.     

高压电场对A549细胞中ABCG2和V-ATPase的表达及其耐药性的影响

目的:探讨高压电场对A549细胞中ABCG2和V-ATPase表达量的影响;探讨高压电场对A549细胞耐药性的影响。方法:MTT法测细胞生长曲线,明确能导致细胞可逆性电穿孔的最高电场强度。慢病毒构建ABCG2和V-ATPase低表达的A549细胞系,并用电场处理,用q-RT-PCR和Western-blot法检测处理前后ABCG2和V-ATPase的m RNA和蛋白表达量的变化。最适强度的高压电场处理各组细胞,在处理前后的细胞中分别加入阿霉素,用高效液相色谱法检测各组细胞中阿霉素浓度。结果:当电场强度为1500 V/cm时,肿瘤细胞增殖最慢;电场强度为1500 V/cm时,肿瘤细胞中ABCG2和V-ATPase的m RNA和蛋白的表达量分别降至对照组的58%和61%,具有统计学差异;1500 V/cm强度的电场可以提高肿瘤细胞内阿霉素的浓度3-4倍。结论:高压电场可以显著降低肿瘤细胞中V-ATPase和ABCG2的m RNA和蛋白的表达量并降低肿瘤细胞的耐药性。     

Fluctuation and linear analysis of Na-current kinetics in squid axon

The power spectrum of current fluctuations and the complex admittance of squid axon were determined in the frequency range 12.5 to 5,000 Hx during membrane voltage clamps to the same potentials in the same axon during internal perfusion with cesium. The complex admittance was determined rapidly and with high resolution by a fast Fourier transform computation of the current response, acquired after a steady state was attained, to a synthesized signal with predetermined spectral characteristics superposed as a continuous, repetitive, small perturbation on step voltage clamps. Linear conduction parameters were estimated directly from admittance data by fitting an admittance model, derived from the linearized Hodgkin-Huxley equations modified by replacing the membrane capacitance with a "constant-phase-angle" capacitance, to the data. The constant phase angle obtained was approximately 80 degrees. At depolarizations the phase of the admittance was 180 degrees, and the real part of the impedance locus was in the left-half complex plane for frequencies below 1 kHz, which indicates a steady-state negative Na conductance. The fits also yielded estimates of the natural frequencies of Na "activation" and "inactivation" processes. By fitting Na-current noise spectra with a double Lorentzian function, a lower and an upper corner frequency were obtained; these were compared with the two natural frequencies determined from admittance analysis at the corresponding potentials. The frequencies from fluctuation analyses ranged from 1.0 to 10.3 times higher than those from linear (admittance) analysis. This discrepancy is consistent with the concept that the fluctuations reflect a nonlinear rate process that cannot be fully characterized by linear perturbation analysis. Comparison of the real part of the admittance and the current noise spectrum shows that the Nyquist relation, which generally applies to equilibrium conductors, does not hold for the Na process in squid axon. The Na-channel conductance, gamma Na, was found to increase monotonically from 0.1 to 4.8 pS for depolarizations up to 50 mV from a holding potential of -60 mV, with no indication of a maximum value.     

Characterization of microbial communities in gas industry pipelines

Culture-independent techniques, denaturing gradient gel electrophoresis (DGGE) analysis, and random cloning of 16S rRNA gene sequences amplified from community DNA were used to determine the diversity of microbial communities in gas industry pipelines. Samples obtained from natural gas pipelines were used directly for DNA extraction, inoculated into sulfate-reducing bacterium medium, or used to inoculate a reactor that simulated a natural gas pipeline environment. The variable V2-V3 (average size, 384 bp) and V3-V6 (average size, 648 bp) regions of bacterial and archaeal 16S rRNA genes, respectively, were amplified from genomic DNA isolated from nine natural gas pipeline samples and analyzed. A total of 106 bacterial 16S rDNA sequences were derived from DGGE bands, and these formed three major clusters: beta and gamma subdivisions of Proteobacteria and gram-positive bacteria. The most frequently encountered bacterial species was Comamonas denitrificans, which was not previously reported to be associated with microbial communities found in gas pipelines or with microbially influenced corrosion. The 31 archaeal 16S rDNA sequences obtained in this study were all related to those of methanogens and phylogenetically fall into three clusters: order I, Methanobacteriales; order III, Methanomicrobiales; and order IV, Methanosarcinales: Further microbial ecology studies are needed to better understand the relationship among bacterial and archaeal groups and the involvement of these groups in the process of microbially influenced corrosion in order to develop improved ways of monitoring and controlling microbially influenced corrosion.