Faster, more accurate, stack-flow measurements.

Exhaust flows from coal-fired electricity-generating plants are determined by averaging flue gas velocities measured at prescribed points in the stack cross section. These velocity measurements are made using EPA-approved differential pressure probes such as the 2-hole S-probe or the 5-hole spherical probe. Measurements using the more accurate 5-hole spherical probes require a time-consuming rotation (or nulling) of the probe to find the yaw angle. We developed a time-saving non-nulling technique using a spherical probe that measures all 3 components of velocity and therefore provides better accuracy than an S-probe. We compared the non-nulling technique with the EPA Method 2F nulling technique at both high (16 m/s) and low (7 m/s) loads in a coal-fired powerplant smokestack. Their excellent mutual agreement (within 0.3% of the flow) demonstrates that the non-nulling technique accurately measures flue gas flows.Implications: Accurate flow measurements are critical for quantifying the levels of greenhouse gases emitted from coal-fired power plant smokestacks. Flow measurement accuracy derives from the annual calibration of stack flow monitors. Calibrations are performed using EPA sanctioned pitot traverse methods called the flow relative accuracy test audit (RATA). This study demonstrates the viability of a new pitot traverse method, herein called the Non-Nulling Method. Testing in a coal-fired power plant stack showed that the new method is 5 times faster to implement than the most accurate EPA pitot traverse method (i.e., Method 2F), yet gives the same or better accuracy.

p21-activated kinase 1 (Pak1) regulates cell motility in mammalian fibroblasts.

The p21 (Cdc42/Rac) activated kinase Pak1 regulates cell morphology and polarity in most, if not all, eukaryotic cells. We and others have established that Pak's effects on these parameters are mediated by changes in the organization of cortical actin. Because cell motility requires polarized rearrangements of the actin/myosin cytoskeleton, we examined the role of Pak1 in regulating cell movement. We established clonal tetracycline-regulated NIH-3T3 cell lines that inducibly express either wild-type Pak1, a kinase-dead, or constitutively-active forms of this enzyme, and examined the morphology, F-actin organization, and motility of these cells. Expression of any of these forms of Pak1 induced dramatic changes in actin organization which were not inhibited by coexpression of a dominant-negative form of Rac1. Cells inducibly expressing wild-type or constitutively-active Pak1 had large, polarized lamellipodia at the leading edge, were more motile than their normal counterparts when plated on a fibronectin-coated surface, and displayed enhanced directional movement in response to an immobilized collagen gradient. In contrast, cells expressing a kinase-dead form of Pak1 projected multiple lamellipodia emerging from different parts of the cell simultaneously. These cells, though highly motile, displayed reduced persistence of movement when plated on a fibronectin-coated surface and had defects in directed motility toward immobilized collagen. Expression of constitutively activated Pak1 was accompanied by increased myosin light chain (MLC) phosphorylation, whereas expression of kinase-dead Pak1 had no effect on MLC. These results suggest that Pak1 affects the phosphorylation state of MLC, thus linking this kinase to a molecule that directly affects cell movement.

Search for the rare decay B-->pil+ l-.

We have performed a search for the flavor-changing neutral-current decays B-->pil+ l-, where l+ l- is either e+ e- or mu+ mu-, using a sample of 230 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector. We observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be B(B-->pil+ l-)<9.1 x 10(-8) at 90% confidence level. We also search for the lepton-flavor-violating decays B-->pie+/- mu-/+ and measure an upper limit on the isospin-averaged branching fraction of B(B-->pie+/- mu-/+)<9.2 x 10(-8) at 90% confidence level.

Amplification of the ATP-binding cassette 2 transporter gene is functionally linked with enhanced efflux of estramustine in ovarian carcinoma cells.

An estramustine-resistant human ovarian carcinoma cell line, SKEM, was generated to explore resistance mechanisms associated with this agent. Cytogenetic analysis revealed that SKEM cells have a homogeneously staining region (hsr) at chromosome 9q34. Microdissection of the hsr, followed by fluorescence in situ hybridization to SKEM and normal metaphase spreads, confirmed that the amplified region was derived from sequences from 9q34. In situ hybridization with a probe specific for ABC2, a gene located at 9q34 that encodes an ATP-binding cassette 2 (ABC2) transporter, indicated that this gene is amplified approximately 6-fold in the estramustine-resistant cells. Southern analysis confirmed that ABC2 was amplified in SKEM, and Northern analysis indicated that the ABC2 transcript was overexpressed approximately 5-fold. The ABC1 gene located at 9q22-31 was not amplified in the resistant cells, and mRNA levels of several other ABC transporter genes were unaltered. Consistent with the concept that increased ABC2 expression contributes to the resistant phenotype, we observed that the rate of efflux of dansylated estramustine was increased in SKEM compared with control cells. In addition, antisense treatment directed toward ABC2 mRNA sensitized the resistant cells to estramustine. Together, these results suggest that amplification and overexpression of ABC2 contributes to estramustine resistance and provides the first indication of a potential cellular function for this product.

Cloning and characterization of human adenosine 5'-triphosphate-binding cassette, sub-family A, transporter 2 (ABCA2).

We have isolated the full-length cDNA for human ATP-binding cassette, sub-family A, member 2 transporter (ABCA2). The ORF of this cDNA encodes a protein consisting of 2436 amino acids with apparent molecular weight of M(r) 270,000. Accordingly, ABCA2 is the largest known mammalian ABC transporter described thus far. Analysis of mRNA expression levels indicated that ABCA2 is highest in human brain and has a broad expression pattern in a panel of tumor cell lines. Using specific antibodies to ABCA2 and various organelle marker proteins, ABCA2 was found to colocalize with the lysosomal/endosomal marker LAMP1, forming discrete, punctate intracellular vesicles. In ABCA2-transfected cells, the transporter also colocalized with a fluorescently labeled steroid analogue, estramustine. The sequestration of the steroid into the lysosomal/endosomal compartment indicates a potential substrate specificity for ABCA2. Furthermore, the presence of a lipocalin signature motif in the ABCA2 sequence suggests a possible broad role for this protein in the transport of steroids, lipids, and related molecules.

Chemical agents that promote chromatin compaction radiosensitize tumour cells.

PURPOSE: Previous studies indicated that cells whose chromatin is naturally compacted at the time of radiation are hypersensitive to radiation-induced killing, primarily by single-hit inactivation. Some chemicals that are known to promote chromatin compaction in interphase cells are here investigated for their radiosensitizing potential. MATERIALS AND METHODS: Okadaic acid (OA), a protein phosphatase inhibitor, fostriecin (FC), a topoisomerase II inhibitor and trichostatin A (TSA), a histone deacetylase inhibitor, were reported to promote chromatin compaction in mammalian cells. Asynchronous populations of HT-29 (human colon carcinoma) cells were exposed to various concentrations of OA, FC and TSA for various times before irradiation with various doses of Cs-137 gamma-rays and toxicity and radiosensitization were measured. Induced chromatin compaction was visualized by electron microscopy (EM). Histone 1 (H1) and histone 3 (H3) phosphorylation was measured by Western blotting, whole-cell fluorescence microscopy and confocal microscopy. RESULTS: OA and FC produced significant radiosensitization at 2 Gy after short (2 h) exposures. These chemical treatments also produced increased phosphorylation of H3 and increased chromatin compaction as measured by EM. A 2-h exposure of cells to TSA had no effect on cell radiosensitivity, histone phosphorylation or chromatin condensation. However, a 16-h exposure to TSA produced significant radiosensitization, histone phosphorylation and chromatin condensation, presumably by secondary mechanisms. CONCLUSIONS: These data are consistent with the hypothesis that compacted chromatin is a hypersensitive target for radiation killing. Furthermore, the modulation of chromatin conformation by drugs selectively in tumour cells might radiosensitize tumours whose cells are intrinsically radioresistant.

Amantadine-induced patulous eustachian tubes in Parkinson's disease.

Patulous Eustachian tube (PET) is a common condition that produces symptoms of aural fullness and autophony. We describe a Parkinson's disease (PD) patient that experienced a reversible bilateral patulous (hyperpatent) Eustachian tube syndrome induced by treatment with amantadine hydrochloride. The clinical features, relevant anatomy and physiology, and associated risk factors for PET are reviewed.

Measurement of the Time-Dependent CP Asymmetry in B;{0}-->D_{CP};{(*)}h;{0} Decays.

We report a measurement of the time-dependent CP-asymmetry parameters S and C in color-suppressed B{0}-->D{(*)0}h{0} decays, where h{0} is a pi{0}, eta, or omega meson, and the decays to one of the CP eigenstates K+K-, K{S}{0}pi{0}, or K{S}{0}omega. The data sample consists of 383 x 10{6} Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The results are S=-0.56+/-0.23+/-0.05 and C=-0.23+/-0.16+/-0.04, where the first error is statistical and the second is systematic.

Integrated electrooptic laser deflector.

An integrated optical laser deflector employing the electrooptic effect is analyzed and shown to provide continuous angular deflection in one dimension. The angle of deflection is found to vary linearly with applied voltage. Because of the integrated optical configuration, significant deflection angles can be obtained for relatively low values of applied voltage. The presence of the deflector configuration within a thin-film cavity is shown to reduce the voltage required for a specific deflection. Waveguide mode coupling resulting from the induced refractive index variation is considered and found to be negligible for typical waveguide parameters.

Totally internally reflecting thin-film optical cavities.

Thin-film optical cavities formed by optical waveguides in which end faces are parallel, optically smooth, and perpendicular to waveguide surfaces are analyzed for the possibility of total internal reflection of waveguide mode ray components at the end faces. Conditions for the occurrence of this phenomena in various modes are derived and evaluated for GaAs waveguides using dispersion relations. A refractive index difference between waveguide and surrounding media of at least 4% for GaAs is necessary before total reflection at the end faces can occur. is nearly always expected. For such differences, total reflection in single mode GaAs waveguide is nearly always expected.

Integrated optical silicon photodiode array.

We consider device design, fabrication, and operation of integrated optical photodiode arrays in which p-i-n junction photodiodes are formed in silicon. A SiO(2) layer on silicon serves as the effective substrate for a KPR waveguide. Light is coupled from the waveguide at the detector region either through the evanescent field or by multiple refraction into the detector. The waveguide-photodiode structure is designed so that nearly 100% of the incident optical energy can be absorbed in the photodiode junction depletion region. A device quantum efficiency of 80% is measured compared to a theoretical value of 93%.

Optical coupling from fibers to channel waveguides formed on silicon.

Direct coupling of light from fibers supported in preferentially etched grooves on a silicon surface to channel waveguides formed in the same grooves is demonstrated. Criteria are presented for choosing a groove geometry that matches the center of the fiber to the center of the waveguide and thereby yielding optimum coupling. Channel waveguide tapering and integration of detectors into the channel waveguide termination are demonstrated. A general configuration allowing CCD time multiplexing is introduced.

Distributed-feedback coupling in Ga(1-x)Al(x)As double-heterostructure lasers: effect of aluminum concentration.

The variation of the feedback coupling coefficient in Ga(1-x)Al(x)As distributed-feedback (DFB) lasers as a function of the Al concentration surrounding the GaAs optical confinement waveguide is considered. An optimum thickness for which the feedback coupling is maximum is determined for each transverse mode. The largest such maximum occurs for the lowest order mode. Fractional Al concentrations that yield symmetrical optical waveguides are found to be most effective in minimizing threshold current density, with the maximum Al concentrations being limited by doping and lattice mismatch considerations.

Temperature-independent thin-film optical waveguide.

The concept of having the effective refractive index of an optical waveguide mode be independent of temperature is introduced. It is shown that this concept should be realizable with a Corning 7059 glass thin-film waveguide supported on a SiO(2)-Si substrate for a waveguide thickness of 0.37 microm. Measurements of effective refractive index as a function of temperature confirm this prediction of temperature independence in that they show a very small variation with temperature for a 0.35-microm thick waveguide in comparison with that for a 0.98-microm thick waveguide.

Single-mode fiber coupler.

This paper describes the fabrication process and coupling principle of a single-mode fiber coupler. Precise etching properties of the fibers used are presented. Fiber etching is shown to result in smooth surfaces. Coupling is seen to vary with the refractive index of the material separating the fiber cores. Coupling efficiency is shown to be variable in a controlled and reversible manner after coupler fabrication. For a 3-dB coupling efficiency,

Freestanding, Micromachined, Multimode Silicon Optical Waveguides at lambda = 1.3 mum for Microelectromechanical Systems Technology.

Freestanding, multimode optical channel waveguides formed by micromachining silicon are demonstrated. Fabrication utilizes standard microelectromechanical systems (MEMS) technology. Losses in the 0.57-0.80-dB/cm range are measured for channel waveguides with an air-silicon-air structure, whereas losses in the 1.12-1.52-dB/cm range are measured for channel waveguides with a SiO(2)-silicon-SiO(2) structure. Freestanding channel waveguides, along with optical fibers and other MEMS structures, can readily be mounted on a silicon MEMS platform to provide optimal alignment for maximizing optical coupling, and they are thus expected to be useful in devices that involve light and MEMS structures.

Log-converting processor element for CCD linear imaging arrays.

A photosensor element suitable for incorporation into charge-coupled device (CCD) imaging arrays in which the charge injected into the CCD is proportional to the logarithm of incident light intensity is presented. The photosensor element consists of a photodiode directly coupled to a two-stage MOSFET common source amplifier. This element occupies an area of 25 x 100 microm and is arranged so that it could be incorporated into a linear CCD imaging array having a period of 25 microm. A logarithmic response is measured over a 68.6-dB range of incident light intensity with a sensitivity of 55 mV/decade of light intensity.

Fabrication of optical waveguide taper couplers utilizing SiO(2).

The fabrication of optical waveguide couplers involving tapered layers of SiO(2) is discussed. Details of the photolithographic fabrication processing sequence are presented. This process utilizes carefully controlled etchant undercutting and has been found to be quite reproducible. It has allowed fabrication of tapers having changes in Sio(2) thickness of 1.0,microm over lengths of 55-75 microm. Results are presented which demonstrate taper transverse uniformity for distances of over 600,microm. The smoothness and gradual nature of the tapers are apparent in scanning electron microscope pictures of a taper cross section.