High-Intensity Discharge Lamp and Duffing Oscillator - Similarities and Differences

The processes inside the arc tube of high-intensity discharge lamps are investigated by finite element simulations. The behavior of the gas mixture inside the arc tube is governed by differential equations describing mass, energy and charge conservation as well as the Helmholtz equation for the acoustic pressure and the Navier-Stokes equation for the flow driven by the buoyancy and the acoustic streaming force. The model is highly nonlinear and requires a recursion procedure to account for the impact of acoustic streaming on the temperature and other fields. The investigations reveal the presence of a hysteresis and the corresponding jump phenomenon, quite similar to a Duffing oscillator. The similarities and, in particular, the differences of the nonlinear behavior of the high-intensity discharge lamp to that of a Duffing oscillator are discussed. For large amplitudes the high-intensity discharge lamp exhibits a stiffening effect in contrast to the Duffing oscillator.Comment: 14 pages, 8 figure

Botulinum Toxin as Preventive Treatment for Migraine: A Randomized Double-Blind Study

Aim: To determine if botulinum toxin type A (BoNT-A) injections can reduce the frequency and severity of migraines. Methods: Patients (n = 127) were randomized to receive placebo or two doses of BoNT-A (Dysport (R)). The primary endpoint was reduction in number of migraine attacks up to week 8 and between weeks 8 and 12 after injection. Patient diaries were used to record secondary endpoints, including frequency, severity and duration of migraine attacks. Results: There was a mean reduction of 0.54 and 0.94 attacks/month with placebo and BoNT-A, respectively, and absolute attack count was less in the verum group (3.6 vs. 4.2 attacks/month), but this was not statistically significant. The patients' global assessment of efficacy was significantly better than placebo in the high-dose group (p = 0.02) but no effects were seen for the other secondary efficacy parameters. Conclusion: Our study showed a trend towards a reduced attack rate with verum but did not show any statistically significant efficacy of BoNT-A in the prophylactic treatment of migraine. Copyright (C) 2009 S. Karger AG, Base

An efficient one-step site-directed and site-saturation mutagenesis protocol

We have developed a new primer design method based on the QuickChange™ site-directed mutagenesis protocol, which significantly improves the PCR amplification efficiency. This design method minimizes primer dimerization and ensures the priority of primer-template annealing over primer self-pairing during the PCR. Several different multiple mutations (up to 7 bases) were successfully performed with this partial overlapping primer design in a variety of vectors ranging from 4 to 12 kb in length. In comparison, all attempts failed when using complete-overlapping primer pairs as recommended in the standard QuickChange™ protocol. Our protocol was further extended to site-saturation mutagenesis by introducing randomized codons. Our data indicated no specific sequence selection during library construction, with the randomized positions resulting in average occurrence of each base in each position. This method should be useful to facilitate the preparation of high-quality site saturation librarie

Production of a Functional Catalytic Antibody ScFv-NusA Fusion Protein in Bacterial Cytoplasm

Functional expression of catalytic antibodies in the cytoplasm of E. coli is potentially of great interest in searching for new catalysts by genetic selection. Herein, a catalytic antibody single chain Fv (ScFv) 14D9, which catalyzes a highly enantioselective protonation, was expressed as a NusA fusion protein under the T7 promoter. A functional disulfide-containing ScFv fusion protein was obtained in the oxidizing environment of bacterial cytoplasm. The 14D9 ScFv could not be overexpressed alone without NusA fusion. The highly soluble NusA protein most likely retards aggregate formation of ScFv and indirectly supports correct folding and disulfide bridge formation in the fusion construct ScFv-NusA. The ScFv-NusA fusion product shows highly enantioselective, specific, hapten inhibited catalytic activity comparable to its parent monoclonal antibody, 14D9. The NusA fusion method might be generally helpful for functional antibody expression in vivo and for the new development of biocatalysts by genetic selectio

Acoustic behavior of melon-headed whales varies on a diel cycle.

Many terrestrial and marine species have a diel activity pattern, and their acoustic signaling follows their current behavioral state. Whistles and echolocation clicks on long-term recordings produced by melon-headed whales (Peponocephala electra) at Palmyra Atoll indicated that these signals were used selectively during different phases of the day, strengthening the idea of nighttime foraging and daytime resting with afternoon socializing for this species. Spectral features of their echolocation clicks changed from day to night, shifting the median center frequency up. Additionally, click received levels increased with increasing ambient noise during both day and night. Ambient noise over a wide frequency band was on average higher at night. The diel adjustment of click features might be a reaction to acoustic masking caused by these nighttime sounds. Similar adaptations have been documented for numerous taxa in response to noise. Or it could be, unrelated, an increase in biosonar source levels and with it a shift in center frequency to enhance detection distances during foraging at night. Call modifications in intensity, directionality, frequency, and duration according to echolocation task are well established for bats. This finding indicates that melon-headed whales have flexibility in their acoustic behavior, and they collectively and repeatedly adapt their signals from day- to nighttime circumstances

The SNARE Machinery in Mast Cell Secretion

Mast cells are known as inflammatory cells which exert their functions in allergic and anaphylactic reactions by secretion of numerous inflammatory mediators. During an allergic response, the high-affinity IgE receptor, FcεRI, becomes cross-linked by receptor-bound IgE and antigen resulting in immediate release of pre-synthesized mediators – stored in granules – as well as in de novo synthesis of various mediators like cytokines and chemokines. Soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptors (SNARE) proteins were found to play a central role in regulating membrane fusion events during exocytosis. In addition, several accessory regulators like Munc13, Munc18, Rab GTPases, secretory carrier membrane proteins, complexins, or synaptotagmins were found to be involved in membrane fusion. In this review we summarize our current knowledge about the SNARE machinery and its mechanism of action in mast cell secretion

Detection of 133^{133}Xe from the Fukushima nuclear power plant in the upper troposphere above Germany

After the accident in the Japanese Fukushima Dai-ichi nuclear power plant in March 2011 large amounts of radioactivity were released and distributed in the atmosphere. Among them were also radioactive noble gas isotopes which can be used as tracers to test global atmospheric circulation models. This work presents unique measurements of the radionuclide $^{133}$Xe from Fukushima in the upper troposphere above Germany. The measurements involve air sampling in a research jet aircraft followed by chromatographic xenon extraction and ultra-low background gas counting with miniaturized proportional counters. With this technique a detection limit of the order of 100 $^{133}$Xe atoms in litre-scale air samples (corresponding to about 100 mBq/m$^3$) is achievable. Our results provide proof that the $^{133}$Xe-rich ground level air layer from Fukushima was lifted up to the tropopause and distributed hemispherically. Moreover, comparisons with ground level air measurements indicate that the arrival of the radioactive plume at high altitude over Germany occurred several days before the ground level plume.Comment: 8 pages, 5 figure

MECHANICAL ENERGY DIFFERENCES BETWEEN WALKING AND RUNNING AT DIFFERENT VELOCITIES ON TREADMILL

INTRODUCTION: Cavanagh (1990) described a variation from 170 to 1700 W in power output for the same movement (running at 3.6 m/s) calculated by six different authors. These differences occurred mainly due to different procedures for energy calculation and generated data that are not comparable. The purpose of this investigation was to describe, analyze, and compare the mechanical energy curves (total, internal and external energies) for six subjects while walking and running on treadmill, by using the same procedure for energy calculation. METHODS: Six male subjects were filmed with two video-cameras (Sony-50Hz) while walking at 1.5 m/s and running at 3.0 and 4.0 m/s on a treadmill. After a manual digitizing process, a 3D analysis was performed from the kinematics. The analysis was based on a 13 segment model. Positions of segmental centers of gravity, segmental weights, and moments of inertia were estimated on the basis of tables devised by Dempster (1955) as revised by Winter (1979). The components of mechanical energy were calculated at each instant of time, using the equations described by Zatsiorsky et al. (1987). RESULTS AND DISCUSSION: In relation to the differences between walking and running, the following observations were made: a) in walking the greatest contribution to the total change derived from the internal energy, while in running it derives from the external energy; b) the internal and external energy were in phase in walking, and in opposition in running. Comparing the variations in the two velocities of running, the following conclusions were drawn: a) the average value of the absolute total energy at 3.0 m/s was 1237.9 J and at 4.0 m/s 1544.2 J; b) there was a linear correlation (r = 0.84) between the change in velocity and the change in total energy; b) with the increase in velocity, the average increase in the total contribution of the change in internal energy was about 72% and of the external energy 36%; c) there was no change in the contribution of the potential energy to the change in external energy; d) the increase in the internal energy was chiefly dependent on the increase in the kinetic energy. CONCLUSION: Although the results related to the shape of the curves for mechanical energy for walking and running are already a matter of consensus in the field of biomechanics, it would appear that the numerical results are still open to broad discussion

Metzincin's canonical methionine is responsible for the structural integrity of the zinc-binding site

The metzincins constitute a subclan of metalloproteases possessing a HEXXHXXGXXH/D zinc-binding consensus sequence where the three histidines are zinc ligands and the glutamic acid is the catalytic base. A completely conserved methionine is located downstream of this motif. Families of the metzincin clan comprise, besides others, astacins, adamalysins proteases, matrix metallo-proteases, and serralysins. The latter are extracellular 50kDa proteases secreted by Gram-negative bacteria via a type I secretion system. While there is a large body of structural and biochemical information available, the function of the conserved methionine has not been convincingly clarified yet. Here, we present the crystal structures of a number of mutants of the serralysin member protease C with the conserved methionine being replaced by Ile, Ala, and His. Together with our former report on the leucine and cysteine mutants, we demonstrate here that replacement of the methionine side chain results in an increasing distortion of the zinc-binding geometry, especially pronounced in the χ2 angles of the first and third histidine of the consensus sequence. This is correlated with an increasing loss of proteolytic activity and a sharp increase of flexibility of large segments of the polypeptide chai