A theory of electromagnetic and gravitational fields

Careful calculations using classical field theory show that if a macroscopic ball with uniform surface charge (say, a billiard ball with 1E6 excess electrons) is released near the surface of the earth, it will almost instantaneously accelerate to relativistic speed and blow a hole in the ground. This absurd prediction is just the macroscopic version of the self-force problem for charged particles [1]. Furthermore, if one attempts to develop from electromagnetism a parallel theory for gravitational [2], the result is the same, self-acceleration.

The basis of the new theory is a measure of energy density for any wave equation [3–5]. Given any solution of any four-vector wave equation in spacetime (for example, the potentials (c^-1φA)=(A⁰,A¹,A²,A³) in electromagnetism), one can form the 16th first order partial derivatives of the vector components, with respect to the time and space variables (ct,x) = (x⁰, x¹, x², x³). The sum of the squares of the 16 terms is a natural energy function [6, p. 283] (satisfying a conservation law . Such energy functions are routinely utilized by mathematicians as Lyapunov functions in the theory of stability of waves with boundary conditions. A Lagrangian using this sum leads to a new energy tensor for electromagnetic and gravitational fields, an alternative to that in [7].     

Qualitative stability and solvability of difference equations

We develop sufficient conditions for qualitative stability and solvability of the real discrete time system x_{t+ 1}= A_xi + b. These conditions are a combination of qualitative and quantitative criteria and depend on signed digraphs.     

Mid-infrared laser-absorption diagnostic for vapor-phase fuel mole fraction and liquid fuel film thickness

A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C–H stretching band of vapor n-decane and liquid n-dodecane near 3.4 μm (3000 cm⁻¹). n-Dodecane film thicknesses <20 μm were accurately measured in the absence of vapor, and simultaneous measurements of n-dodecane liquid film thickness and n-decane vapor mole fraction (300 ppm) were measured with <10% uncertainty for film thicknesses <10 μm. A potential application of the measurement technique is to provide accurate values of vapor mole fraction in combustion environments where strong absorption by liquid fuel or oil films on windows make conventional direct absorption measurements of the gas problematic.     

Ozone–isoprene reactions: Product formation and aerosol potential

Dark-phase experiments between isoprene and O₃ are discussed. UNC outdoor chamber experiments have shown that in high-concentration systems of isoprene and O₃ (5 ppm C and 1 ppm) approximately 75% of the reacted carbon can be observed in the product formation of HCHO, CO, methacrolein, methylvinylketone, methylglyoxal, acetaldehyde, and propylene. Mechanisms were developed which gave reasonable fits to dark-phase chamber experiments of MACR, MVK, isoprene, and O₃. Experimental data and modeling results were used to generate O₃ rates of attack on MVK and MACR. An isoprene–O₃ rate of 1.67 × 10^?2 ppm^?1·min^?1 was used and is consistent with other rates reported in the literature. Dark isoprene–O₃ systems appear to form homogeneously nucleated aerosol. Most of these particles appear and remain at diameters well below the optical cutoff region (0.3–0.5 μm), as opposed to the particles from similar α-pinene–O₃ systems, which also form at smaller sizes but then grow into the optical size range (0.5 μm). Lower concentrations of α-pinene and O₃ (0.2 ppm C and 0.12 ppm) still generated substantial aerosol, but by comparison, rapid CN nucleation was not observed during a similar side-by-side system of isoprene and O₃.     

Wavelength modulation absorption spectroscopy with 2 f detection using multiplexed diode lasers for rapid temperature measurements in gaseous flows

Multiplexed fiber-coupled diode lasers are used to probe second-harmonic line shapes of two near-infrared water absorption features, at 1343 nm and 1392 nm, in order to infer temperatures in gases containing water vapor, such as combustion flows. Wavelength modulation is performed at 170 kHz, and is superimposed on 1-kHz wavelength scans in order to recover full second-harmonic line shapes. Digital waveform generation and lock-in detection are performed using a data-acquisition card installed in a PC. An optimal selection of the modulation indices is shown to greatly simplify data interpretation over extended temperature ranges and to minimize the need for calibration when performing 2 f ratio thermometry. A theoretical discussion of this optimized strategy for 2 f ratio thermometry, as well as results from experimental validations in a heated cell, at pressures up to atmospheric, are presented in order to illustrate the utility of this technique for rapid temperature measurements in gaseous flow fields. PACS 42.62.Fi; 42.55.Px; 42.60.Fc; 39.30.+w     

Near-infrared diode laser absorption sensor for rapid measurements of temperature and water vapor in a shock tube

A fast-response (100 kHz) tunable diode laser absorption sensor is developed for measurements of temperature and H₂O concentration in shock tubes, e.g. for studies of combustion chemistry. Gas temperature is determined from the ratio of fixed-wavelength laser absorption of two H₂O transitions near 7185.60 cm^-1 and 7154.35 cm^-1, which are selected using design rules for the target temperature range of 1000–2000 K and pressure range of 1–2 atm. Wavelength modulation spectroscopy is employed with second-harmonic detection (WMS-2f) to improve the sensor sensitivity and accuracy. Normalization of the second-harmonic signal by the first-harmonic signal is used to remove the need for calibration and minimize interference from emission, scattering, beam steering, and window fouling. The laser modulation depth for each H₂O transition is optimized to maximize the WMS-2f signal for the target test conditions. The WMS-2f sensor is first validated in mixtures of H₂O and Ar in a heated cell for the temperature range of 500–1200 K (P=1 atm), yielding an accuracy of 1.9% for temperature and 1.4% for H₂O concentration measurements. Shock wave tests with non-reactive H₂O–Ar mixtures are then conducted to demonstrate the sensor accuracy (1.5% for temperature and 1.4% for H₂O concentration) and response time at higher temperatures (1200–1700 K, P=1.3–1.6 atm). PACS 42.62.Fi; 42.55.Px; 42.60.Fc; 07.35.+k     

Detection of chlorinated hydrocarbons via Laser-atomization/Laser-induced fluorescence

Chlorinated hydrocarbons (CHC), photodissociated at 193 nm, are detected with high sensitivity by observing the atomic chlorine fragment via laser-induced fluorescence (LIF). Photofragment emission spectra from CH₃Cl, CH₂Cl₂, CHCl₃, CCl₄, C₂HCl₃, and C₂Cl₄ demonstrate that photofragment fluorescence and chemiluminescence are negligible in the region 700–800 nm where the 3p ⁴4p ⁴ S ⁰ 3p ⁴4s ⁴ P fluorescence from atomic chlorine is detected. There is also negligible interference for photodissociation in Ar, N₂, and air bath gases. Total CHC can be readily detected in air flows at mixing fractions less than 20 ppb and averaging times less than 1 minute. Techniques for considerable improvement in this detection limit are discussed.Supported by the NSF     

Lifetimes and transition probabilities for NH(A3Πi-X3Σ−)

Temporally and spectrally resolved laser-induced fluorescence in the A³Π_i-X³Σ^? system of the NH radical has been measured in a low-pressure flow discharge. The radiative lifetimes of the υ′ = 1 and 0 levels are. respectively, 420 ± 3.5 and 440 ± 15 ns. Relative transition probabilities A_1υ″ for emission from υ′ = 1 are: A₁₀ = 0.030 ± 0.006. A₁₁ = 1.00, A₁₂ = 0.032 ± 0.003 and A₁₃ = 0.0014 ± 0.0002. Calculations of relative A_υ′υ″ using a Morse potential and a previously, calculated ab initio electronic transition moment yield results for this highly diagonal transition which agree with experiment to within a factor of three or better.     

Molecular characterization of a gene for aldose reductase (CbXYL1) from Candida boidinii and its expression in Saccharomyces cerevisiae

Candida boidinii produces significant amounts of xylitol from xylose, and assays of crude homogenates for aldose (xylose) reductase (XYL1p) have been reported to show relatively high activity with NADH as a cofactor even though XYL1p purified from this yeast does not have such activity. A gene coding for XYL1p from C. boidinii (CbXYL1) was isolated by amplifying the central region using primers to conserved domains and by genome walking. CbXYL1 has an open reading frame of 966 bp encoding 321 amino acids. The C. boidinii XYL1p is highly similar to other known yeast aldose reductases and is most closely related to the NAD(P)H-linked XYL1p of Kluyveromyces lactis. Cell homogenates from C. boidinii and recombinant Saccharomyces cerevisiae were tested for XYL1p activity to confirm the previously reported high ratio of NADH:NADPH linked activity. C. boidinii grown under fully aerobic conditions showed an NADH:NADPH activity ratio of 0.76, which was similar to that observed with the XYL1p from Pichia stipitis XYL1, but which is much lower than what was previously reported. Cells grown under low aeration showed an NADH:NADPH activity ratio of 2.13. Recombinant S. cerevisiae expressing CbXYL1 showed only NADH-linked activity in cell homogenates. Southern hybridization did not reveal additional bands. These results imply that a second, unrelated gene for XYL1p is present in C. boidinii.     

Continuous xylose fermentation byCandida shehatae in a two-stage reactor

Recent work has identified ethanol toxicity as a major factor preventing continuous production of ethanol at the concentrations obtainable in batch culture. In this paper we investigate the use of a continuous two-stage bioreactor design to circumvent toxic effects of ethanol. Biomass is produced via continuous culture in the first stage reactor in which ethanol concentrations are either absent or maintained at low levels. The freshly grown cells are fed into the second bioreactor in which high ethanol concentrations are produced. The steady influx of fresh cells and continuous removal of spent cells helps minimize the loss of fermentative activity that results from anaerobiosis and exposure to high ethanol concentrations. A final ethanol concentration of 37 g L⁻¹ and overall yield of .32 g g⁻¹ were obtained with the two-stage reactor as compared to corresponding values of 38 g L⁻¹ and .32 g g⁻¹ obtained in batch. The volumetric rate in the two-state process was .96 g L⁻¹ as compared to .46 g L⁻¹ h⁻¹ in batch. Maintained in cooperation with the University of Wisconsin-Madison. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the US Department of Agriculture of any product or service to the exclusion of others which may be suitable.