Microbial fuel cell technology for measurement of microbial respiration of lactate as an example of bioremediation amendment

Microbial fuel cell (MFC) based sensing was explored to provide for the development of an insitu bioremediation monitoring approach for substrate concentrations and microbial respiration rates. MFC systems were examined in column systems where Shewanella oneidensis MR1 used an external electron acceptor (an electrode) to metabolize lactate (a bioremediation additive) to acetate. Column systems were operated with varying influent lactate concentrations (0-41mM) and monitored for current generation (0.01-0.39mA). Biological current generation paralleled bulk phase lactate concentration both in the influent and in the bulk phase at the anode; current values were correlated to lactate concentration at the anode (R 2=0.9), The electrical signal provided real-time information for electron donor availability and biological activity. These results have practical implications for efficient and inexpensive real-time monitoring of insitu bioremediation processes where information on substrate concentrations is often difficult to obtain and where information on the rate and nature of metabolic processes is neede

Differential Response To Tabata Interval Versus Traditional Kettlebell Training Protocol

Please view abstract in the attached PDF file

Cardiovascular and metabolic demands of the kettlebell swing using a Tabata interval versus a traditional resistance protocol

International Journal of Exercise Science 7(3) : 179-185, 2014. Tabata (TAB) training, consisting of eight cycles of 20 seconds of maximal exercise followed by 10 seconds of rest, is time-efficient, with aerobic and anaerobic benefit. This study investigated the cardiovascular and metabolic demands of a TAB versus traditional (TRAD) resistance protocol with the kettlebell swing. Fourteen young (18-25y), non-obese (BMI 25.7±0.8 kg/m2) participants reported on three occasions. All testing incorporated measurements of HR, oxygen consumption, and blood lactate accumulation. Each participant completed Tabata kettlebell swings (male- 8kg, female- 4.5kg; 8 intervals; 20s maximal repetitions, 10s rest). On a subsequent visit (TRAD), the total swings from the TAB protocol were evenly divided into 4 sets, with 90s rest between sets. Outcome measures were compared using paired t-tests. The TAB was completed more quickly than the TRAD protocol (240.0±0.0 v. 521.5±3.3 sec, P\u3c0.01), at a higher perceived exertion (Borg RPE; 15.1±0.7 v. 11.7±0.9, P\u3c0.01). The TAB elicited a higher average VO2 value (33.1±1.5 v. 27.2±1.6 ml/kg/min, P\u3c0.01), percent of VO2peak achieved (71.0±0.3 v. 58.4±0.3%, P\u3c0.01), maximal HR (162.4±4.6 v. 145.6±4.8 bpm, P\u3c0.01), and post-exercise blood lactate concentration (6.4±1.1 v. 3.7±0.5 mmol/L, P\u3c0.01). Conclusion: The kettlebell swing demonstrated significantly greater cardiovascular and metabolic responses within a TAB vs. TRAD framework. Appropriate screening and risk stratification are advised before implementing kettlebell swings

Measurements of Volatile Organic Compounds Using Proton Transfer Reaction - Mass Spectrometry during the MILAGRO 2006 Campaign

Volatile organic compounds (VOCs) were measured by proton transfer reaction – mass spectrometry (PTR-MS) on a rooftop in the urban mixed residential and industrial area North Northeast of downtown Mexico City as part of the Megacity Initiative – Local and Global Research Observations (MILAGRO) 2006 field campaign. Thirty eight individual masses were monitored during the campaign and many species were quantified including methanol, acetaldehyde, toluene, the sum of C2 benzenes, the sum of C3 benzenes, acetone, isoprene, benzene, and ethyl acetate. The VOC measurements were analyzed to gain a better understanding of the type of VOCs present in the MCMA, their diurnal patterns, and their origins. Diurnal profiles of weekday and weekend/holiday aromatic VOC concentrations showed the influence of vehicular traffic during the morning rush hours and during the afternoon hours. Plumes including elevated toluene as high as 216 parts per billion (ppb) and ethyl acetate as high as 183 ppb were frequently observed during the late night and early morning hours, indicating the possibility of significant industrial sources of the two compounds in the region. Wind fields during those peak episodes revealed no specific direction for the majority of the toluene plumes but the ethyl acetate plumes arrived at the site when winds were from the Southwest or West. The PTR-MS measurements combined with other VOC measuring techniques at the field site as well as VOC measurements conducted in other areas of the Mexico City Metropolitan Area (MCMA) will help to develop a better understanding of the spatial pattern of VOCs and its variability in the MCMA. Atmos. Chem. Phys., 9, 467–481, 2009.Robert A. Welch Foundation (Grant A-1417)Texas A & M University. Center for Atmospheric Chemistry and EnvironmentNational Science Foundation (U.S.) (ATM-0528227

Rapid X-Ray Variability of Neutron Stars in Low-Mass Binary Systems

The dramatic discovery with the Rossi X-Ray Timing Explorer satellite of remarkably coherent $\sim$300--1200 Hz oscillations in the X-ray brightness of some sixteen neutron stars in low-mass binary systems has spurred theoretical modeling of these oscillations and investigation of their implications for the neutron stars and accretion flows in these systems. High-frequency oscillations are observed both during thermonuclear X-ray bursts and during intervals of accretion-powered emission and appear to be a characteristic feature of disk-accreting neutron stars with weak magnetic fields. In this review we focus on the high-frequency quasi-periodic oscillations (QPOs) seen in the accretion-powered emission. We first summarize the key properties of these kilohertz QPOs and then describe briefly the models that have been proposed to explain them. The existing evidence strongly favors beat-frequency models. We mention several of the difficulties encountered in applying the magnetospheric beat-frequency model to the kilohertz QPOs. The most fully developed and successful model is the sonic-point beat-frequency model. We describe the work on this model in some detail. We then discuss observations that could help to distinguish between models. We conclude by noting some of the ways in which study of the kilohertz QPOs may advance our understanding of dense matter and strong gravitational fields.Comment: 10 pages LaTeX including six figures, uses espcrc2.sty (included), invited talk at "The Active X-Ray Sky", eds. L. Scarsi, H. Bradt, P. Giommi, and F. Fior

Direct simulation of ion beam induced stressing and amorphization of silicon

Using molecular dynamics (MD) simulation, we investigate the mechanical response of silicon to high dose ion-irradiation. We employ a realistic and efficient model to directly simulate ion beam induced amorphization. Structural properties of the amorphized sample are compared with experimental data and results of other simulation studies. We find the behavior of the irradiated material is related to the rate at which it can relax. Depending upon the ability to deform, we observe either the generation of a high compressive stress and subsequent expansion of the material, or generation of tensile stress and densification. We note that statistical material properties, such as radial distribution functions are not sufficient to differentiate between different densities of amorphous samples. For any reasonable deformation rate, we observe an expansion of the target upon amorphization in agreement with experimental observations. This is in contrast to simulations of quenching which usually result in denser structures relative to crystalline Si. We conclude that although there is substantial agreement between experimental measurements and most simulation results, the amorphous structures being investigated may have fundamental differences; the difference in density can be attributed to local defects within the amorphous network. Finally we show that annealing simulations of our amorphized samples can lead to a reduction of high energy local defects without a large scale rearrangement of the amorphous network. This supports the proposal that defects in amorphous silicon are analogous to those in crystalline silicon.Comment: 13 pages, 12 figure

The Structure, Dynamics and Electronic Structure of Liquid Ag-Se Alloys Investigated by Ab Initio Simulation

Ab initio molecular-dynamics simulations have been used to investigate the structure, dynamics and electronic properties of the liquid alloy Ag(1-x)Se(x) at 1350 K and at the three compositions x=0.33, 0.42 and 0.65. The calculations are based on density-functional theory in the local density approximation and on the pseudopotential plane-wave method. The reliability of the simulations is confirmed by detailed comparisons with very recent neutron diffraction results for the partial structure factors and radial distribution functions (RDF) of the stoichiometric liquid Ag2Se. The simulations show a dramatic change of the Se-Se RDF with increasing Se content. This change is due to the formation of Se clusters bound by covalent bonds, the Se-Se bond length being almost the same as in pure c-Se and l-Se. The clusters are predominantly chain-like, but for higher x a large fraction of 3-fold coordinated Se atoms is also found. It is shown that the equilibrium fractions of Se present as isolated atoms and in clusters can be understood on a simple charge-balance model based on an ionic interpretation. The Ag and Se diffusion coefficients both increase with Se content, in spite of the Se clustering. An analysis of the Se-Se bond dynamics reveals surprisingly short bond lifetimes of less than 1 ps. The changes in the density of states with composition arise directly from the formation of Se-Se covalent bonds. Results for the electronic conductivity obtained using the Kubo-Greenwood approximation are in adequate agreement with experiment for l-Ag2Se, but not for the high Se contents. Possible reasons for this are discussed.Comment: 14 pages, Revtex, 14 Postscript figures embedded in the tex

The X-ray fast-time variability of Sco X-2 (GX 349+2) with RXTE

Sco X-2 (GX 349+2) is a low-mass X-ray binary and Z source. We have analysed 156 ks of Rossi X-ray Timing Explorer data, obtained in 1998 January, on this source. We investigated the fast-time variability as a function of position on the Z track. During these observations, Sco X-2 traced out the most extensive Z track ever reported from this object, making this the most comprehensive study thus far. We found the broad peaked flaring branch noise that is typical of Sco X-2, with a centroid frequency in the range 3.3--5.8 Hz. We also discovered low frequency noise, and a new peaked noise feature, with centroid frequencies in the range 5.4--7.6 Hz and 11--54 Hz, respectively. We discuss the phenomenology of these features, their relationship with the power spectral components found in other low-mass X-ray binaries, and the implications for current models. In particular, the low frequency noise we observed was strongest at intermediate energies, in contrast to the low frequency noise seen in other Z sources. We also detected very low frequency noise, and have calculated complex cross spectra between intensity and hardness. We found that the very low frequency noise is not entirely due to motion along the Z track.Comment: 17 pages, 9 figures, minor improvements, accepted for publication in MNRA