Phase resolved PLIF and chemiluminescence for measuring combustion dynamics

Transient behavior of combustion systems has long been a subject of both fundamental and practical concerns. Extreme cases of very rapid changes include the ignition of reacting mixtures and detonation. At the other extreme is a wide range of quasi-steady changes of behavior, for example adjustments of the operating point of a combustion chamber. Between the limiting cases of 'infinitely fast' and 'infinitesimally slow' lie important fundamental problems of time-dependent behavior and a wide array of practical applications. Among the latter are combustion instabilities and their active control, a primary motivation for the work reported in this paper. Owing to the complicated chemistry, chemical kinetics and flow dynamics of actual combustion systems, numerical simulations of their behavior remains in a relatively primitive state. Even as that situation continually improves, it is an essential part of the field that methods of measuring true dynamical behavior be developed to provide results having both fine spatial resolution and accuracy in time. This paper is a progress report of recent research carried out in the Jet Propulsion Center of the California Institute of Technology

Observations of the Crab Nebula and its pulsar in the far-ultraviolet and in the optical

We present HST/STIS far-UV observations of the Crab nebula and its pulsar. Broad, blueshifted absorption arising in the nebula is seen in C IV 1550, reaching about 2500 km/s. This can be interpreted as evidence for a fast outer shell, and we adopt a spherically symmetric model to constrain the properties of this. We find that the density appears to decrease outward in the shell. A lower limit to the mass is 0.3 solar masses with an accompanying kinetic energy of 1.5EE{49} ergs. A massive 10^{51} erg shell cannot be excluded, but is less likely if the density profile is much steeper than R^{-4} and the velocity is <6000 km/s. The observations cover the region 1140-1720 A. With the time-tag mode of the spectrograph we obtain the pulse profile. It is similar to that in the near-UV, although the primary peak is marginally narrower. Together with the near-UV data, and new optical data from NOT, our spectrum of the pulsar covers the entire region from 1140-9250 A. Dereddening the spectrum gives a flat spectrum for E(B-V)=0.52, R=3.1. This dereddened spectrum of the Crab pulsar can be fitted by a power law with spectral index alpha_{\nu} = 0.11 +/- 0.04. The main uncertainty is the amount and characteristics of the interstel- lar reddening, and we have investigated the dependence of \alpha_{\nu} on E(B-V) and R. In the extended emission covered by our 25" x 0.5" slit in the far-UV, we detect C IV 1550 and He II 1640 emission lines from the Crab nebula. Several interstellar absorption lines are detected toward the pulsar. The Ly alpha absorption indicates a column density of 3.0+/-0.5\EE{21} cm^{-2} of neutral hydrogen, which agrees well with our estimate of E(B-V)=0.52 mag. Other lines show no evidence of severe depletion of metals in atomic gas.Comment: 18 pages emulateapj style, including 10 figures. ApJ, accepte

The Magnetorotational Instability in Core Collapse Supernova Explosions

We investigate the action of the magnetorotational instability (MRI) in the context of iron-core collapse. Exponential growth of the field on the rotation time scale by the MRI will dominate the linear growth process of field line "wrapping" with the same characteristic time. We examine a variety of initial rotation states, with solid body rotation or a gradient in rotational velocity, that correspond to models in the literature. A relatively modest value of the initial rotation, a period of ~ 10 s, will give a very rapidly rotating PNS and hence strong differential rotation with respect to the infalling matter. We assume conservation of angular momentum on spherical shells. Results are discussed for two examples of saturation fields, a fiducial field that corresponds to Alfven velocity = rotational velocity and a field that corresponds to the maximum growing mode of the MRI. Modest initial rotation velocities of the iron core result in sub-Keplerian rotation and a sub-equipartition magnetic field that nevertheless produce substantial MHD luminosity and hoop stresses: saturation fields of order 10^{15} - 10^{16} G develop within 300 msec after bounce with an associated MHD luminosity of about 10^{52} erg/s. Bi-polar flows driven by this MHD power can affect or even cause the explosions associated with core-collapse supernovae.Comment: 42 pages, including 15 figures. Accepted for publication in ApJ. We have revised to include an improved treatment of the convection, and some figures have been update

Determinants of manufacturing strategy formulation: a longitudinal study in Hong Kong

Abstract Recent developments of the World Trade Organisation and other international trade agreements have forced industries worldwide to face a new era of intense global competition. Manufacturers will have to compete effectively not only in the local context, but in wider regional and global marketplaces. Global competition has offered numerous opportunities and problems for the manufacturing industry. This paper investigates the determinants of strategy formulation (SF) in manufacturing enterprises and consolidates the empirical findings of a longitudinal study from 1994-2001 in Hong Kong. It also discusses the experiences from some leading Hong Kong manufacturers in managing the competitive pressures and gaining sustainable competitive advantages. The paper attempts to complement the literature base of SF practices with empirical evidence. The findings presented address the identification of success factors and problematic areas that provide manufacturers with guidance and references for formulating viable strategies to meet their business and operations needs

Circumstellar Na I and Ca II lines in type IIP supernovae and SN 1998S

We study a possibility of detection of circumstellar absorption lines of Na I D$_{1,2}$ and Ca II H,K in spectra of type IIP supernovae at the photospheric epoch. The modelling shows that the circumstellar lines of Na I doublet will not be seen in type IIP supernovae for moderate wind density, e.g., characteristic of SN 1999em, whereas rather pronounced Ca II lines with P Cygni profile should be detectable. A similar model is used to describe Na I and Ca II circumstellar lines seen in SN 1998S, type IIL with a dense wind. We show that line intensities in this supernova are reproduced, if one assumes an ultraviolet excess, which is caused primarily by the comptonization of supernova radiation in the shock wave.Comment: To be published in Astronomy Letter

Combined cetuximab and trastuzumab are superior to gemcitabine in the treatment of human pancreatic carcinoma xenografts

Background: Pancreatic carcinoma remains a treatment-refractory cancer with a poor prognosis. Here, we compared anti-epidermal growth factor receptor (EGFR) and anti-HER2 monoclonal antibodies (2mAbs) injections with standard gemcitabine treatment on human pancreatic carcinoma xenografts. Materials and methods: Nude mice, bearing human pancreatic carcinoma xenografts, were treated with either combined anti-EGFR (cetuximab) and anti-HER2 (trastuzumab) or gemcitabine, and tumor growth was observed. Results and conclusion: In first-line therapy, mice survival was significantly longer in the 2mAbs group compared with gemcitabine (P < 0.0001 for BxPC-3, P = 0.0679 for MiaPaCa-2 and P = 0.0019 for Capan-1) and with controls (P < 0.0001). In second-line therapy, tumor regressions were observed after replacing gemcitabine by 2mAbs treatment, resulting in significantly longer animal survival compared with mice receiving continuous gemcitabine injections (P = 0.008 for BxPC-3, P = 0.05 for MiaPaCa-2 and P < 0.001 for Capan-1). Therapeutic benefit of 2mAbs was observed despite K-Ras mutation. Interestingly, concerning the mechanism of action, coinjection of F(ab′)2 fragments from 2mAbs induced significant tumor growth inhibition, compared with controls (P = 0.001), indicating that the 2mAbs had an Fc fragment-independent direct action on tumor cells. This preclinical study demonstrated a significant improvement of survival and tumor regression in mice treated with anti-EGFR/anti-HER2 2mAbs in first- and second-line treatments, compared with gemcitabine, independently of the K-Ras statu

The role of ethanol or acetaldehyde in the biosynthesis of ethylene in carnation (Dianthus caryophyllus L.) cv. Yellow Candy

Abstract Carnation (Dianthus caryophyllus L.) cv. Yellow Candy flowers were treated with ethanol solution (4%) in the absence or presence of 1 or 10 mM L-methionine, or ethanol or acetaldehyde solution (0.05%), in the absence or presence of 1 mM aminocyclopropane carboxylic acid (ACC). Spermidine in petals was measured over time in flowers treated with 4% ethanol or distilled water. Ethanol treatment significantly increased vase life by 10 days; methionine had no significant effect. The vase life of ACC-treated flowers was reduced by 4 days, the ethylene climacteric peak advanced by 5 days and ethylene production was increased in comparison with flowers not treated with ACC. In the absence of ACC, ethanol solution significantly increased vase life of carnation cv. Yellow Candy by 5 days and inhibited ethylene production, whereas in the presence of ACC, ethanol neither increased vase life nor inhibited ethylene production. Acetaldehyde also failed to increase vase life of carnation cv. Yellow Candy either in the absence or presence of ACC. There was no difference between spermidine content of ethanol-or distilled water-treated flowers. It was concluded that 4% ethanol failed to inhibit conversion of methionine to S-adenosyl methionine (SAM) because ethanol failed to inhibit production of spermidine. Furthermore, ethanol or acetaldehyde also failed to inhibit conversion of ACC to ethylene

The Hourglass Nebulae of Sher 25 and SN 1987 A: Two of a Kind?

We have performed a detailed study of the morphology and kinematics of the hourglass-shaped nebula around the blue supergiant Sher 25 in the galactic giant HII region NGC 3603. Near-infrared high resolution adaptive optics images in the Br gamma line and HST/NICMOS images in the HeI 1.08mu line were compared with iso-velocity maps in the H alpha and [NII] lines. The adaptive optics observations clearly resolved the width of the ring (0.9", i.e., 0.027 pc), yielding delta R / R = 1:8. We show that the H alpha and [NII] lines trace the entire silhouette of the hourglass. The bipolar lobes of the hourglass expand at 70 km/s, whereas the ring around the waist of the hourglass expands at 30 km/s. Both the ring and the bipolar lobes have about the same dynamical age, indicating a common origin and a major outburst and mass-loss event 6630 yr ago. The ionized mass within the hourglass is between 0.3 Mo and 0.6 Mo - quite comparable to the total mass suggested for the expanding (pre-supernova) shell around SN 1987 A. The hourglass structure around Sher 25 is similar to that of SN 1987 A in spatial extent, mass, and velocities. The major differences between these two nebulae might arise from environmental effects. Both internal and external ionization sources are available for Sher 25's nebula. Furthermore, Sher 25 and its hourglass-shaped nebula appear to be moving to the south-west with respect to the ambient interstellar medium, and ram pressure has apparently deformed the hourglass. We conclude that the circumstellar nebulae around SN 1987 A and Sher 25 are very similar and define a new class of nebulae around blue supergiants in their final evolutionary stage.Comment: 9 pages, Latex, also available at ftp://ftp.astro.uiuc.edu/pub/brandner/sher25_apjl or at http://www.astro.uiuc.edu/~brandner/pub.html , accepted for publication in ApJ Letter

Exploitation and resistance: a comparative analysis of the Chinese cheap labour electronics and high-value added IT sectors.

This article compares the electronics sector in the area of Shenzhen, based on cheap labour assembling goods for export, with the IT sector in the area of Shanghai, relying on a more skilled workforce manufacturing high-value added goods. It is asked in what way these rather different locations within the global political economy condition the form and contents of resistance in these two sectors. The article concludes that industrial relations are more confrontational in the electronics sector with informal labour NGOs supporting workers in getting their individual and collective rights. The IT sector, in contrast, is characterised by consensual relationships. Informal labour NGOs concentrate on organising cultural activities for workers’ free time, performing a mediating role between employers and employees, supported by the government