Spectrum Of BD Research Articles

On Drazin Spectral Equation for the Operator Products

Let X be a Banach space and A, B, C, D be bounded linear operators on X. In this paper we show that the Drazin (resp. generalized Drazin) spectrum of AC coincides with the Drazin (resp. generalized Drazin) spectrum of BD under certain assumptions. Moreover, several interesting Banach space properties, such as SVEP and polaroidness, are considered.

Theoretical study of the Stark broadening for Mg iv spectral lines of astrophysical interest

Emission lines of Mg IV have been detected in the Far Ultraviolet Spectroscopic Explorer (FUSE) spectrum of LS V +46°21 star and in the Space Telescope Imaging Spectrograph (STIS) spectrum of BD +28°4211 star. This fact justifies our interest in providing spectroscopic parameters of Mg IV. Stark broadening parameters for 169 spectral lines of Mg IV have been calculated by using the Griem semi-empirical approach. The matrix elements used in these calculations has been determined from 13 configurations of Mg IV: 2s¹2p⁶, 2s²2p⁴ns (n=3–5), 2s²2p⁴nd (n=3–5) and 2s²2p⁴5g for even parity and 2s²2p⁵, 2s²2p⁴np (n=3,4) and 2s²2p⁴nf (n=4,5) for odd parity. Our calculations were made by using the Cowan code. Data are presented for an electron density of 10¹⁷ cmˉ³ and temperatures T=1.0–10.0 (10⁴ K). Also we present calculated values of transition probabilities for 30 spectral lines and radiative lifetimes corresponding to its upper levels. These values were analysed using the data found in the literature. Theoretical trends of the Stark broadening parameters versus the temperature for several lines of astrophysical interest are presented.

DETECTION OF PHOSPHORUS, SULPHUR, AND ZINC IN THE CARBON-ENHANCED METAL-POOR STAR BD+44 493*

ABSTRACT The carbon-enhanced metal-poor star BD+44°493 ([Fe/H] = −3.9) has been proposed as a candidate second-generation star enriched by metals from a single Pop III star. We report the first detections of P and S and the second detection of Zn in any extremely metal-poor carbon-enhanced star, using new spectra of BD+44°493 collected by the Cosmic Origins Spectrograph on the Hubble Space Telescope. We derive [P/Fe] = −0.34 ± 0.21, [S/Fe] = +0.07 ± 0.41, and [Zn/Fe] = −0.10 ± 0.24. We increase by 10-fold the number of Si i lines detected in BD+44°493, yielding [Si/Fe] = +0.15 ± 0.22. The [S/Fe] and [Zn/Fe] ratios exclude the hypothesis that the abundance pattern in BD+44°493 results from depletion of refractory elements onto dust grains. Comparison with zero-metallicity supernova (SN) models suggests that the stellar progenitor that enriched BD+44°493 was massive and ejected much less than 0.07 M ⊙ of 56Ni, characteristic of a faint SN.

Behçet's disease in children, an overview.

SummaryBD is a systemic inflammatory disease with a variable vasculitis. Paediatric onset is very rare and carries a strong genetic component. Oral ulcers and fever of unknown origin are frequent at onset and difficult to distinguish from other inflammatory disorders; therefore, expert opinion is still mandatory to recognize the disease early. An international expert consensus has recently proposed new classification criteria for children with BD. The clinical spectrum of BD is heterogeneous and influenced by gender, ethnicity and country of residence. Young males have the worst prognosis with significantly more frequent neurological, ocular and vascular involvement. BD treatment is aimed at alleviating inflammation. Among all drugs, TNFα inhibitors have become a standard to control severe ocular, neurological and digestive system involvement.

Astrophysical parameters and orbital solution of the peculiar X-ray transient IGR J00370+6122

BD+6073 is the optical counterpart of the X-ray source IGR J00370+6122, a probable accretion-powered X-ray pulsar. The X-ray light curve of this binary system shows clear periodicity at 15.7 d, which has been interpreted as repeated outbursts around the periastron of an eccentric orbit. We obtained high-resolution spectra of BD+6073 at different epochs. We used the FASTWind code to generate a stellar atmosphere model to fit the observed spectrum and obtain physical magnitudes. The synthetic spectrum was used as a template for cross-correlation with the observed spectra to measure radial velocities. The radial velocity curve provided an orbital solution for the system. We have also analysed the RXTE/ASM and Swift/BAT light curves to confirm the stability of the periodicity. BD +6073 is a BN0.7 Ib low-luminosity supergiant located at an approximate distance of 3.1 kpc, in the CasOB4 association. We derive Teff=24000 K and log gc=3.0, and chemical abundances consistent with a moderately high level of evolution. The spectroscopic and evolutionary masses are consistent at the 1 sigma level with a mass of 15 solar masses. The recurrence time of the X-ray flares is the orbital period of the system. The NS is in a high eccentricity (e=0.56) orbit, and the X-ray emission is strongly peaked around orbital phase 0.2, though the observations are consistent with some level of X-ray activity happening at all orbital phases. The X-ray behaviour of IGR J00370+6122 is reminiscent of intermediate SFXTs, though its peak luminosity is rather low. The orbit is somewhat wider than those of classical persistent supergiant X-ray binaries, which, combined with the low luminosity of the mass donor, explains the low X-ray luminosity. IGR J00370+6122 will likely evolve towards a persistent supergiant system, highlighting the evolutionary connection between different classes of wind-accreting X-ray sources.

Mutation Spectra of S-(2-Hydroxy-3,4-epoxybutyl)glutathione: Comparison with 1,3-Butadiene and Its Metabolites in the Escherichia coli rpoB Gene

S-(2-Hydroxy-3,4-epoxybutyl)glutathione (DEB-GSH conjugate) is formed from the reaction of 1,2:3,4-diepoxybutane (DEB) with glutathione (GSH), and the conjugate is considerably more mutagenic than several other butadiene-derived epoxides-including DEB-in Salmonella typhimurium TA1535 [Cho, S.-H., (2010) Chem. Res. Toxicol. 23, 1544-1546]. We previously identified six DNA adducts in the reaction of the DEB-GSH conjugate with nucleosides and calf thymus DNA and two DNA adducts in livers of mice and rats treated with DEB [Cho, S.-H. and Guengerich, F. P. (2012) Chem. Res. Toxicol. 25, 706-712]. To define the role of GSH conjugation in 1,3-butadiene (BD) metabolism and characterize the mechanism of GSH transferase (GST)-enhanced mutagenicity of DEB, mutation spectra of BD and its metabolites in the absence and presence of GST/GSH and mouse liver microsomes were compared in the rpoB gene of Escherichia coli TRG8. The presence of GST considerably enhanced mutations. The mutation spectra derived from the DEB-GSH conjugate, the DEB/GST/GSH system, and the BD/mouse liver microsomes/GST/GSH system matched each other and were different from those derived from the other systems devoid of GSH. The major adducts in E. coli TRG8 cells treated with the DEB/GST/GSH system, the BD/mouse liver microsomes/GST/GSH system, or the DEB-GSH conjugate were S-[4-(N(7)-guanyl)-2,3-dihydroxybutyl]GSH, S-[4-(N(3)-adenyl)-2,3-dihydroxybutyl]GSH, and S-[4-(N(6)-deoxyadenosinyl)-2,3-dihydroxybutyl]GSH, indicating the presence of the GSH-containing DNA adducts in the systems. These results, along with the strong enhancement of mutagenicity by GST in this system, indicate the relevance of these GSH-containing DNA adducts.

DIOPHANTINE APPROXIMATION IN IMAGINARY QUADRATIC FIELDS

Let H3 be the upper half-space model of the three-dimensional hyperbolic space. For certain cocompact Fuchsian subgroups Γ of an extended Bianchi group Bd, the extremality of the axis of hyperbolic F ∈ Γ in H3 with respect to Γ implies its extremality with respect to Bd. This reduction is used to obtain sharp lower bounds for the Hurwitz constants and lower bounds for the highest limit points in the Markov spectra of Bd for some d < 1000. In particular, such bounds are found for all non-Euclidean class one imaginary quadratic fields. The Hurwitz constants for the imaginary quadratic fields with discriminants -120 and -132 are given. The second minima are also indicated for these fields.

MINIMA OF BINARY INDEFINITE HERMITIAN FORMS

Classification of binary indefinite primitive Hermitian forms modulo the action of the extended Bianchi group (or Hilbert modular group) Bd is given. When the discriminant of the quadratic field [Formula: see text] (and d) is negative, the results obtained can be applied to classify the maximal non-elementary Fuchsian subgroups of Bd, and to find the Hermitian points in the Markov spectrum of Bd. If ν is a Hermitian point in the spectrum, then there is a set of extremal geodesics in H3, the upper half-space model of the three-dimensional hyperbolic space, with diameter 1/ν, which depends on one continuous parameter.

NARROW RADIATIVE RECOMBINATION CONTINUA: A SIGNATURE OF IONS CROSSING THE CONTACT DISCONTINUITY OF ASTROPHYSICAL SHOCKS

X-rays from planetary nebulae (PNs) are believed to originate from a shock driven into the fast stellar wind (v ~ 1000 km/s) as it collides with an earlier circumstellar slow wind (v ~ 10 km/s). In theory, the shocked fast wind (hot bubble) and the ambient cold nebula can remain separated by magnetic fields along a surface referred to as the contact discontinuity (CD) that inhibits diffusion and heat conduction. The CD region is extremely difficult to probe directly owing to its small size and faint emission. This has largely left the study of CDs, stellar-shocks, and the associated micro-physics in the realm of theory. This paper presents spectroscopic evidence for ions from the hot bubble (kT ~ 100 eV) crossing the CD and penetrating the cold nebular gas (kT ~ 1 eV). Specifically, a narrow radiative recombination continuum (RRC) emission feature is identified in the high resolution X-ray spectrum of the PN BD+30 3639 indicating bare C VII ions are recombining with cool electrons at kT_e=1.7+-1.3 eV. An upper limit to the flux of the narrow RRC of H-like C VI is obtained as well. The RRCs are interpreted as due to C ions from the hot bubble of BD+30 3639 crossing the CD into the cold nebula, where they ultimately recombine with its cool electrons. The RRC flux ratio of C VII to C VI constrains the temperature jump across the CD to Delta kT > 80 eV, providing for the first time direct evidence for the stark temperature disparity between the two sides of an astrophysical CD, and constraining the role of magnetic fields and heat conduction accordingly. Two colliding-wind binaries are noted to have similar RRCs suggesting a temperature jump and CD crossing by ions may be a common feature of stellar wind shocks.

THE X-RAY SPECTRUM OF A PLANETARY NEBULA AT HIGH RESOLUTION:CHANDRAGRATINGS SPECTROSCOPY OF BD +30°3639

We present the results of the first X-ray gratings spectroscopy observations of a planetary nebula (PN)—the X-ray-bright, young BD +30°3639. We observed BD +30°3639 for a total of ~300 ks with the Chandra X-ray Observatory's Low Energy Transmission Gratings in combination with its Advanced CCD Imaging Spectrometer (LETG/ACIS-S). The LETG/ACIS-S spectrum of BD +30°3639 is dominated by H-like resonance lines of O VIII and C VI and the He-like triplet line complexes of Ne IX and O VII. Other H-like resonance lines, such as N VII, and lines of highly-ionized Fe are weak or absent. Continuum emission is evident over the range 6-18 A. Spectral modeling indicates the presence of a range of plasma temperatures from Tx ~ 1.7 × 106 K to 2.9 × 106 K and an intervening absorbing column NH ~ 2.4 × 1021 cm–2. The same modeling conclusively demonstrates that C and Ne are highly enhanced, with abundance ratios of C/O ~ 15-45 and Ne/O ~ 3.3-5.0 (90% confidence ranges, relative to the solar ratios), while N and Fe are depleted, with abundances N/O ~ 0.0-1.0 and Fe/O ~ 0.1-0.4, respectively. The intrinsic luminosity of the X-ray source determined from the modeling and the measured flux (FX = 4.1 × 10–13 ergs cm–2 s–1) is LX ~ 8.6 × 1032 erg s–1 (assuming D = 1.2 kpc). These gratings spectroscopy results are generally consistent with earlier results obtained from X-ray CCD imaging spectroscopy of BD +30°3639, but are far more precise. Hence, the Chandra/LETG-S results for BD +30°3639 place severe new constraints on models of PN wind-wind interactions in which X-ray emitting gas within PNs is generated via shocks and the plasma temperature is moderated by effects such as heat conduction or rapid evolution of the fast wind. The tight constraints placed on the (nonsolar) abundances directly implicate the present-day central star—hence, ultimately, the intershell region of the progenitor asymptotic giant branch star—as the origin of the shocked plasma now emitting in X-rays.

On the Binary Nature of Dust-encircled BD +20 307

Three epochs of high resolution spectra of the star BD+20 307 show that it is a short period (~3.5 day) spectroscopic binary of two nearly identical stars. Surprisingly, the two stars, though differing in effective temperature by only ~250 K and having a mass ratio of 0.91, show very different Li line equivalent widths. A Li 6707 Angstrom line is only detected from the primary star, and it is weak. This star is therefore likely to be older than 1 Gyr. If so, the large amount of hot circumbinary dust must be from a very large and recent, but very late evolutionarily, collision of planetesimals.

Strong Excitonic Interactions in the Oxygen-Reducing Site of bd-Type Oxidase: The Fe-to-Fe Distance between Hemes d and b595 is 10 Å

Absorption and circular dichroism (CD) spectra of cytochrome bd from Escherichia coli have been compared for the wild type enzyme and an inactive mutant in which a highly conserved E445 in subunit I has been replaced by alanine [Zhang, J., Hellwig, P., Osborne, J. P., Huang, H. W., Moenne-Loccoz, P., Konstantinov, A. A., and Gennis, R. B. (2001) Biochemistry 40, 8548-8556]. The absorption bands of ferrous heme b595 are absent from the spectrum of the dithionite-reduced E445A form of cytochrome bd. The difference between the spectra of the dithionite-reduced WT and E445A enzymes indicates that in the mutant, heme b595 is present but is not reducible by dithionite. Cytochrome bd reveals intense CD signals dominated by heme d, with almost no contribution from heme b595 or heme b558. The CD spectrum of the reduced wild type enzyme in the Soret band indicates strong excitonic interactions between ferrous heme d and ferrous heme b595, and these interactions are not observed in dithionite-reduced E445A mutant, in which heme b595 remains in the ferric state. Modeling the excitonic interactions in both absorption and CD spectra has been carried out, yielding an estimate of the Fe-to-Fe distance between heme d and heme b595 of about 10 A. The physical proximity supports the hypothesis that heme d and heme b595 can form a di-heme oxygen reducing site, a unique structure for respiratory oxidases.

Detailed Far‐Ultraviolet to Optical Analysis of Four [WR] Stars

We present far-UV to optical analyses of four hydrogen-deficient central stars of planetary nebulae: BD +30 3639, NGC 40, NGC 5315, and NGC 6905. Using the radiative transfer code CMFGEN, we determined new physical parameters and chemical abundances for these stars. The results were analyzed in the context of the [WR] → PG 1159 evolution via the transformed radius-temperature (RT × T*) and H-R diagrams. NGC 5315 showed itself as an odd object among the previously analyzed central stars. Its temperature (~76 kK) is considerably lower than other early-type [WR] stars (~120-150 kK). From our models for NGC 5315 and NGC 6905, it is unclear if early-type [WR] stars have smaller C/He mass ratios than other spectral classes, as claimed in the literature. A ratio of ~0.8 is found for NGC 6905. We analyzed FUSE spectra of these stars for the first time and identified phosphorus in the spectra of BD +30 3639, NGC 40, and NGC 5315 through the doublet transition P V λλ1118, 1128 (3p2Po-3s2S). The Fe, Si, P, S, and Ne abundances were analyzed in the context of the nucleosynthesis occurring in previous evolutionary phases. We found evidence for Fe deficiency in BD +30 3639 and NGC 5315, and we determined a solar Si abundance for BD +30 3639 and NGC 40. Regarding P, an oversolar abundance in the NGC 5315 model was preferred. Upper limits for the S abundance were estimated. We found that Ne is overabundant in BD +30 3639. In the other stars, Ne is weak or undetectable. Our results are in agreement with theoretical predictions and show the usefulness of [WR] stars as test beds for nucleosynthesis calculations in the AGB and post-AGB phases.

High-resolution X-ray Spectroscopy of BD +30°3639

We present preliminary results from the first X-ray gratings spectrometer observations of a planetary nebula (PN). We have used the Chandra X-ray Observatory Low Energy Transmission Gratings Spectrometer (LETGS) to observe the bright, diffuse X-ray source within the well-studied BD +30°3639. The LETGS spectrum of BD +30°3639 displays prominent and well-resolved emission lines of H-like C, O, and Ne and He-like O and Ne. Initial modeling indicates a plasma temperature $T_X \sim 2.5\times10^6$ K and abundance ratios of C/O $\sim20$ , N/O $\stackrel{ , Ne/O $\sim4$ , and Fe/O $\stackrel{ . These results suggest that the X-ray-emitting plasma is dominated by the shocked fast wind from the emerging PN core, where this wind gas likely originated from the intershell region of the progenitor asymptotic giant branch star.

DIOPHANTINE APPROXIMATION IN $\mathbf{Q}(\sqrt{-5})$ AND $\mathbf{Q}(\sqrt{-6})$

The complete description of the discrete part of the Lagrange and Markov spectra of the imaginary quadratic fields with discriminants -20 and -24 are given. Farey polygons associated with the extended Bianchi groups Bd, d = 5, 6, are used to reduce the problem of finding the discrete part of the Markov spectrum for the group Bd to the corresponding problem for one of its maximal Fuchsian subgroup. Hermitian points in the Markov spectrum of Bd are introduced for any d. Let H3 be the upper half-space model of the three-dimensional hyperbolic space. If ν is a hermitian point in the spectrum, then there is a set of extremal geodesics in H3 with diameter 1/ν, which depends on one continuous parameter. This phenomenon does not take place in the hyperbolic plane.

Line profile variability in the spectra of Oef stars

We report the analysis of a long term observing campaign designed to monitor the spectroscopic variability of the Oef star BD +60° 2522. We find that the double-peaked He ii λ 4686 emission line undergoes strong profile variability on time scales of 2–3 day. However, the time scale as well as the pattern of these variations turn out to be epoch dependent and the phenomenon is thus most likely not ruled by a single stable clock. On the other hand, the absorption lines in the spectrum of BD +60° 2522 display line profile variability on time scales of a few hours that might be related to non-radial pulsations. We tentatively propose that the beating of several non-radial pulsation modes triggers transient large-scale density perturbations in a confined stellar wind that produce the 2–3 day time scale variability.

FTIR spectroscopic evidence for the involvement of an acidic residue in quinone binding in cytochrome bd from Escherichia coli.

In this work, FTIR difference spectroscopy is used to search for possible binding partners and protonable groups involved in the binding of the quinol to cytochrome bd from Escherichia coli. In addition, the electrochemically induced FTIR difference spectra are compared for preparations of the enzyme isolated from cells grown at different oxygen levels in which the quinone content of the membrane is altered. On this basis, difference signals can be tentatively attributed to the vibrational modes of the different quinones types that are associated with the enzyme depending on growth conditions. Furthermore, vibrational modes due to the redox-dependent reorganization of the protein vary depending on the quinone associated with the isolated enzyme. Of particular interest are the observations that a mode at 1738 cm(-1) is decreased and a mode at 1595 cm(-1) is increased as observed in direct comparison to the data obtained from samples grown anaerobically. These signals indicate a change in the protonation state of an aspartic or glutamic acid. Since these changes are observed when the ubiquinone ratio in the preparation increases, the data provide evidence for the modulation of the binding site by the interacting quinone and the involvement of an acidic group in the binding site. The tentative assignments of the vibrational modes are supported by electrochemically induced FTIR difference spectra of cytochrome bd in the presence of the specific quinone binding site inhibitors heptylhydroxyquinoline-N-oxide (HQNO) or 2-methyl-3-undecylquinolone-4. Whereas HQNO leads to strong shifts in the FTIR redox difference spectrum, 2-methyl-3-undecylquinolone-4 induces a specific shift of a mode at 1635 cm(-1), which likely originates from the displacement of the C=O group of the bound quinone.

Mutational spectrum of 1,3-butadiene and metabolites 1,2-epoxybutene and 1,2,3,4-diepoxybutane to assess mutagenic mechanisms

1,3-Butadiene (BD) is a multisite carcinogen and is mutagenic in multiple tissues of B6C3F1 mice. BD is bioactivated to at least three directly mutagenic metabolites: 1,2-epoxybutene (EB), 1,2-epoxy-3,4-butanediol (EBD), and 1,2,3,4-diepoxybutane (DEB). However, the contribution of these individual metabolites to the carcinogenicity and in vivo mutatidnal spectrum of BD is uncertain. To assess the role of two BD metabolites EB and DEB in the in vivo mutagenicity of the parent compound BD, we examined the in vitro mutational spectra of EB and DEB in human and rodent cells. We also examined the in vivo mutagenicity and mutational spectrum of inhaled EB in the lung. In the bone marrow and spleen of B6C3F1 laci transgenic mice, BD-induced an increased frequency of the identical class of point mutations at A:T base pairs: AT→GC transitions and AT→TA transversions. BD exposure also induced an increased frequency of GC→AT transitions in the spleen that was not observed in bone marrow, demonstrating tissue-specific differences in mutation spectrum. Exposure of Rat2 laci transgenic cells and human TK6 lymphoblasts to EB-induced an increased frequency of AT→TA transversions. DEB exposure induced an increased frequency of AT→TA transversions and partial deletions at hprt in human cells. In Rat laci transgenic cells, DEB was not mutagenic at laci but induced an increased frequency of micronuclei. In contrast to inhaled BD, inhaled DEB and EB were not mutagenic in the bone marrow or spleen. However, EB was mutagenic in the lungs. In the lung of mice, EB-induced specific increases in GC→AT transitions, AT→TA transversions, and deletion events. AT→TA transversions are the most consistent mutation observed across biological systems following in vivo exposure to BD or in vitro exposures to EB and DEB. Although, BD exposure in mice induces chromosomal alterations and single base substitutions, the specific BD metabolite that induces the genetic events leading to tumors is uncertain. At present, it appears that only DEB can effectively induce this range of mutagenic events at levels of this metabolite that occur in the blood of mice exposed to BD. Detailed investigations to identify relevant biomarkers of BD exposure and response, particularly DNA adducts or lesions, that can be biologically linked to the range of genotoxic events known to occur in mice exposed to BD are needed.

The HMXRB system BD+37° 1160/4U 0515+38

We present new optical data on BD+37° 1160, the optical counterpart of the X-ray source 1H0521+373 (=4U0515+38). The analysis of the stellar spectrum confirms that it is a very high mass object that probably experienced in the past several shell emission episodes. From the present optical data we find clear evidence of a new shell being ejected by the star. The hard spectrum of the X-ray source points to the presence of a compact companion. The similarity of the optical spectrum of BD+37° 1160 in the X-ray active phase with that of X Per strongly suggests that BD+37° 1160 is a BeXRB with a collapsed companion on a very wide orbit.

Lung-specific mutagenicity and mutational spectrum in B6C3F1 lacI transgenic mice following inhalation exposure to 1,2-epoxybutene

1,3-Butadiene (BD) is carcinogenic and mutagenic in B6C3F1 mice. BD inhalation induces an increased frequency of specific base substitution mutations in the bone marrow and spleen of B6C3F1 lacI transgenic mice. BD is bioactivated to at least three mutagenic metabolites: 1,2-epoxybutene (EB), 1,2-epoxy-3,4-butanediol (EBD), and 1,2,3,4-diepoxybutane (DEB), however, the contribution of these individual metabolites to the in vivo mutational spectrum of BD is uncertain. In the present study, lacI transgenic mice were exposed by inhalation (6 h per day, 5 days per week for 2 weeks) to 0 or 29.9 ppm of the BD metabolite, EB to assess its contribution to the in vivo mutational spectrum of BD. No increase in lacI mutant frequency was observed in the bone marrow or spleen of EB-exposed mice. The lack of mutagenicity in the bone marrow or spleen likely relate to insufficient levels of EB reaching these tissues. The lacI mutant frequency was increased 2.7-fold in the lungs of EB-exposed mice (mean±S.D., 9.9±3.0×10 −5) compared to air control mice (3.6±0.7×10 −5). DNA sequence analysis of 65 and 66 mutants from the lungs of air control and EB-exposed mice, respectively, revealed an increase in the frequency of two categories of base substitution mutation and deletions. Like mice exposed to BD, EB-exposed mice had an increased frequency of A:T→T:A transversions. However, in contrast to the BD mutational spectra, G:C→A:T transitions at 5′-CpG-3′ sequences, occurred with increased frequency in the EB-exposed mice. The increased frequency of deletions as well as the induction of two tandem mutations and a tandem deletion in the lungs of EB-exposed mice are also inconsistent with previous mutational spectra from BD-exposed mice or EB-exposed cells in culture. We hypothesize that the direct in vivo mutagenicity and further in situ metabolism of EB in the lungs of EB-exposed mice played a prominent role in the generation of the current mutational spectrum.