Understanding Sources of Defects in Polyimide Films Using Aerosol Based Printing

A study of the sources of defects in films of commercially available polyamic acid fabricated using aerosol based printing was carried out. Printing was conducted using a Sono-Tek spray nozzle on multi-modular Direct Write Additive Manufacturing System. The driving force behind this work stemmed from the need to form smooth, defect free films to be used in electronic components. While numerous process conditions give rise to defects such as the obvious substrate cleanliness, efforts here focused on the more subtle conditions such as deposition temperature, deposition speed, nozzle height from the substrate and cure temperature. The results of this study led to the identification of the most critical source of defects and to a set of optimal process conditions in the printing of polyimide films using aerosol based printing.Mechanical Engineerin

Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events

The $B^0$-$\bar B^0$ oscillation frequency has been measured with a sample of 23 million \B\bar B pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives $\Delta m_d = 0.493 \pm 0.012{(stat)}\pm 0.009{(syst)}$ ps$^{-1}$.Comment: 7 pages, 1 figure, submitted to Physical Review Letter

Measurement of the CP-Violating Asymmetry Amplitude sin2β\beta

We present results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0bar from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta = 0.741 +/- 0.067 (stat) +/- 0.033 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/- 0.017 (syst). The magnitude of lambda is consistent with unity, in agreement with the Standard Model expectation of no direct CP violation in these modes

A search for the decay B+→K+ννˉB^+ \to K^+ \nu \bar{\nu}

We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu \bar{\nu}$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ${\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let

High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe

We report on the realization of a high quality distributed Bragg reflector with both high and low refractive index layers lattice matched to ZnTe. Our structure is grown by molecular beam epitaxy and is based on binary compounds only. The high refractive index layer is made of ZnTe, while the low index material is made of a short period triple superlattice containing MgSe, MgTe, and ZnTe. The high refractive index step of Delta_n=0.5 in the structure results in a broad stopband and the reflectivity coefficient exceeding 99% for only 15 Bragg pairs.Comment: 4 pages, 3 figure

Measurement of the electron energy spectrum and its moments in inclusive B -> Xe nu decays

We report a measurement of the inclusive electron energy spectrum for semileptonic decays of B mesons in a data sample of 52 million Y(4S)-->B(B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We determine the branching fraction, first, second, and third moments of the spectrum for lower cutoffs on the electron energy between 0.6 and 1.5 GeV. We measure the partial branching fraction to be B(B-->Xenu,E-e>0.6 GeV)=[10.36+/-0.06(stat.)+/-0.23(sys.)]%

Improved measurement of CP asymmetries in B-0 ->(c(c)over-bar)K0((*)) decays

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227x10(6) Upsilon(4S)-> B (B) over bar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2 beta in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B-0 or (0) from its decay products. We measure sin2 beta=0.722 +/- 0.040(stat)+/- 0.023(syst) in agreement with the standard model expectation

Mechanistic bases for differences in passive absorption

Increasing evidence indicates that small birds have more extensive non-mediated, paracellular intestinal absorption of hydrosoluble compounds than do mammals, although studies have not employed uniform methodologies or demonstrated differences at the tissue level. The mechanistic bases behind apparent species differences are poorly understood. We show using uniform methodology at the whole-animal level that intact, unanesthetized pigeons had significantly higher absorption of L-arabinose and L-rhamnose, two water-soluble compounds used to measure paracellular absorption, than similarly sized laboratory rats. The species differences were also evident using perfused isolated loops of duodenum, showing that the difference in paracellular absorption occurred at the tissue level, even when D-glucose absorption rates (transcellular+paracellular) were similar between the two species. The greater absorption of these probes in pigeons could not be explained by mediated uptake of the putative paracellular probes, or by increased nominal surface area, increased villus area or increased number of tight junctions. Rats and pigeons had comparable absorption of larger probes, which is consistent with similar effective pore size of the tight junction between enterocytes. The elimination of these mechanistic explanations might suggest that pigeon intestine has relatively higher paracellular solvent drag, but pigeon duodenal segments did not have higher net water absorption than rat duodenal segments. Whatever the exact mechanism(s), the paracellular pathway of both species limits substantial (>5%) fractional absorption to molecules smaller than about 4.8 Å (Mr ca. 350), and permeability to smaller molecules at the tissue level is higher in pigeons than in rats