bluuebunny/crossref_metadata_2025 huggingface dataset:
Kα X-ray emission spectra from highly charged Fe ions in EBIT
Authors: Jacobs V L , Beiersdorfer P
Published: March 2008

A detailed spectral model has been developed for the computer simulation of the 2p → 1s Kα X-ray emission from highly charged Fe ions in the electron beam ion trap (EBIT). The spectral features of interest occur in the range 1.84–1.94 Å. The fundamental radiative emission processes associated with radiationless electron capture or dielectronic recombination, inner-shell electron collisional excitation, and inner-shell-electron collisional ionization are taken in account. For comparison, spectral observations and simulations for high-temperature magnetic-fusion (tokamak) plasmas are reviewed. In these plasmas, small departures from steady-state corona-model charge-state distributions can occur because of ion transport processes, while the assumption of equilibrium (Maxwellian) electron energy distributions is expected to be valid. Our investigations for EBIT have been directed at the identification of spectral features that can serve as diagnostics of extreme nonequilibrium or transient ionization conditions, and allowance has been made for general (non-Maxwellian) electron energy distributions. For the precise interpretation of the high-resolution X-ray observations, which may involve the analysis of blended spectral features composed of many lines, it has been necessary to take into account the multitude of individual fine-structure components of the Kα radiative transitions in the ions from Fe XVIII to Fe XXV. At electron densities higher than the validity range of the corona-model approximation, collisionally induced transitions among low-lying excited states can play an important role. It is found that inner-shell-electron excitation and ionization processes involving the complex intermediate ions from Fe XVIII to Fe XXI produce spectral features, in the wavelength range from 1.89 to 1.94 Å, which are particularly sensitive to density variations and transient ionization conditions. PACS Nos.: 52.72.+v, 32.80.Dz, 32.70.Fw, 32.30.Rj
X-ray wavelength survey of iron and nickel L-shell emission and resonance contributions to their intensities
Authors: Gu M F
Published: March 2008

As part of the laboratory astrophysics program at the electron beam ion traps of the Lawrence Livermore National Laboratory, L-shell X-ray emission of Fe and Ni ions have been studied extensively in the past decade. In this paper, we review these experimental efforts in line identification and wavelength surveys of Fe and Ni L-shell emission and resonance contributions to their intensities. PACS Nos.: 52.72.+v, 52.20.–j, 34.80.Kw
Non π/N scattering of CP1 solitons
Authors: Cova R J , Amundsen D , Zakrzewski W J
Published: March 2008

Using numerical simulations we investigate topological charge N = 3, 4 soliton head-on collisions in the CP1 model on a flat torus T2. We observe dual-polygon scattering π/N except for configurations of three solitons starting far away from each other.

PACS Nos.: 11.10.–z; 02.60.–x; 03.50.Kk
Atoms through the looking glass – a relativistic challenge
Authors: Mårtensson-Pendrill A.-M.
Published: March 2008

The search for weak-interaction-induced atomic parity nonconservation, initiated in the 1970s, challenges both theory and experiment. Since the weak interaction is very short range, the atomic effects increase rapidly with nuclear charge, as Z3. The focus has thus been on heavy atoms, where relativistic effects are essential, and nuclear size must be taken into account. The generalization of atomic many-body methods to relativistic systems involved both computational and formal difficulties, incorporating methods developed in quantum electrodynamics. Twenty years ago, the ability to treat atomic pair correlation in a relativistic framework was emerging. The application to many-electron systems opened up for comparison with experiment for many atomic properties, such as isotope shifts, hyperfine structure, and hyperfine anomalies, which reflect nuclear properties. In addition, the search for simultaneous violation of both parity- and time-reversal symmetry involves different types of effects, including nuclear “Schiff moments”. Comparison between computed and experimental results for highly charged hydrogen-like systems provides a test of the theoretical and numerical treatment of the electron–nucleus interaction and of the description of nuclear distributions.PACS Nos.: 31.15.Dv, 31.25.–v, 31.30.Gs, 21.10.Ft, 21.10.Ky, 32.80.Ys, 11.30.Er
High-resolution spectroscopy of K-shell praseodymium with a high-energy microcalorimeter
Authors: Thorn D B , Brown G V , Clementson J H.T. , Chen H , Chen M , Beiersdorfer P , Boyce K R , Kilbourne C A , Porter F S , Kelley R L
Published: March 2008

We present a measurement of the K-shell spectrum of He-like through Be-like praseodymium ions trapped in the Livermore SuperEBIT electron beam ion trap using a bismuth absorber pixel on the XRS/EBIT microcalorimeter. This measurement is the first of its kind where the n = 2 to n = 1 transitions of the various charge states are spectroscopically resolved. The measured transition energies are compared with theoretical calculations from several atomic codes.PACS Nos.: 32.30.–r, 32.30.Rj, 39.30.+w
Measuring the ionization balance of gold in a low-density plasma ofimportance to inertial confinement fusion
Authors: May M J , Beiersdorfer P , Brown G V , Fournier K B , Gu M , Hansen S B , Schneider M , Scofield J H , Terracol S , Reed K J , Wilson B , Wong K L , Boyce K R , Kelley R , Kilbourne C A , Porter F S
Published: March 2008

Charge state distributions (CSDs) have been determined in low-density (≈1012 cm–3) gold plasmas having either a monoenergetic beam (EBeam = 2.66, 3.53, 4.54, 5.35, 5.85, and 6.35 keV) or experimentally simulated thermal electron distributions (Te = 2.0, 2.5, and 3.0 keV). These plasmas were created in the Livermore electron beam ion traps, EBIT-I and EBIT-II. Line emission and radiative recombination features of K to Kr-like gold ions were recorded in the X-ray region with a crystal spectrometer and a photometrically calibrated microcalorimeter. The CSDs in the experimentally simulated thermal plasmas were inferred by fitting the observed 4f → 3d and 5f → 3d lines with synthetic spectra from the Hebrew University Lawrence Livermore Atomic Code (HULLAC). Additionally, the CSDs in the beam plasmas were inferred both from fitting the line emission and fitting the radiative recombination emission to calculations from the General Relativistic Atomic Structure Program. Despite the relatively simple atomic physics in the low-density plasma, differences existed between the experimental CSDs and the simulations from several available codes (for example, RIGEL). Our experimental CSD relied upon accurate electron impact cross sections provided by HULLAC. To determine their reliability, we have experimentally determined the cross sections for several of the n = 3 → 4 and n = 3 → 5 excitations in Ni to Ga-like Au and compared them to distorted wave calculations. Cross-section calculations by flexible atomic code (FAC) and HULLAC were found to be very consistent. Recent Au spectra recorded during experiments at the OMEGA laser facility are presented and compared with those recorded from EBIT-I and EBIT-II. This comparison shows that spectra from the two sources are surprisingly similar despite a 10 order of magnitude difference in their respective plasma densities. PACS Nos.: 52.50.Fs, 52.25.Jm, 34.80.Kw, 34.80.Lx
The photon clean method: an event-based approach to analyzing X-ray spectra
Authors: Carpenter M H , Jernigan J G , Beiersdorfer P , Brown G V
Published: March 2008

The Photon Clean Method (PCM) is an inverse Monte-Carlo method of spectral fitting that differs from traditional fitting routines found in spectral modeling packages by fitting event lists as opposed to binned spectra. The model spectrum is represented in event form as well. Thus, using this method it is possible to fit data of higher dimensionality than can be fit using binned spectra and standard routines based on Chi-Square statistics, such as event-mode data from electron beam ion traps or satellite observations that are tagged, for example, as a function of time, position, or energy. To demonstrate some of the power of the PCM and aid in its development, we have implemented a simplified one-dimensional version of the PCM algorithm (PCM1D). Using our implementation, which is a command-line program intended for public release, we have performed tests on simulated and observed Chandra ACIS CCD data, and present two examples, one on Cassiopeia A and another on a simulated multitemperature plasma in collisional ionization equilibrium. PACS No.: 52.65.Pp
A brief review of the intensity of lines 3C and 3D in neon-like Fe XVII
Authors: Brown G V
Published: March 2008

X-ray emission from neon-like Fe XVII has been measured with high-resolution spectrometers from laboratory or celestial sources for nearly seven decades. Two of the strongest lines regularly identified in these spectra are the 1P1 → 1S0 resonance and the 3D1 → 1S0 intercombination line, known as 3C and 3D, respectively. This paper gives a brief overview of measurements of the intensities of the lines 3C and 3D from laboratory and celestial sources and their comparison to model calculations, with an emphasis on measurements completed using an electron beam ion trap. It includes a discussion of the measured absolute cross sections compared with results from modern atomic theory calculations as well as the diagnostic utility of the relative intensity, R = I3C/I3CD, as it applies to the interpretation of spectra measured from the Sun and extra-solar sources. PACS Nos.: 32.30.Rj, 32.30.–r, 32.70.Cs, 52.72.+v, 95.85.Nv, 96.60.P–, 97.10.Ex
Applications of EBITs to spectra of multi-electron ions: some solved and some unsolved problems
Authors: Wu S , Hutton R
Published: March 2008

Electron beam ion traps (EBITs) have, and will continue, to play an important role in unraveling spectral features in highly charged ions. In this paper, we will discuss two examples of EBIT-based spectroscopy of multi-electron systems, i.e., spectroscopy of N-, O- and F-like Ba and of Pm-like W. The EBIT work on W will be compared to a spectrum taken at the ASDEX upgrade Tokamak in Garching. PACS Nos.: 32.30.Jc, 32.30.Rj
Monitoring and performance of an earth-fill dam in central Alberta
Authors: Williams D. R. , Balanko L. A. , Martin R. L.
Published: March 2008

Westburne Dam, located near Coronation, Alberta, is a 30 m high earth-fill dam with a crest length of approximately 200 m. It was constructed in 1969, for water storage purposes, inatributary valley of the Battle River. Local geology comprises sand, silt, and glacial clay till overlying sandstone and clay shale of the Bearpaw Formation. A large landslide occurred at the north abutment in 1971. In order to assess the performance of the dam, a monitoring program was initiated in 1972. A total of 28 slope indicators, 30 piezometers, and a number of standpipes were installed in the dam, abutments, and slide area. A ground survey network was established in 1974 and has since been surveyed annually.Cumulative ground movements up to 4 m have been observed in the slide mass adjacent to the dam, at rates as high as 900 mm/year. Movements of up to 20 mm/year have been measured in the dam. Piezometric conditions in the slide have been found to be related to the reservoir level. Boreholes, drilled as part of a stability review in 1979, confirmed a shear surface, previously identified by slope indicators, and showed it to extend beneath the dam. It is thought to be associated with the mechanism of a larger, older, slide underlying the dam site.Remedial action taken in 1980 included lowering the dam crest and the maximum operating reservoir level. Piezometric levels and ground measurements have since declined somewhat; the slide mass has shown rates of movement of 100–200 mm/year. Through implementation of the detailed monitoring program and remedial measures, the dam has been maintained in an operational capacity. The paper presents and discusses the results of the monitoring program, providing a comprehensive 10-year record of dam performance. Keywords: earth-fill dam, landsliding, instrumentation, ground movements, pore pressures, slope stability analysis.
Eastmain River Dam—A case history of mass compaction in earth dam construction
Authors: Rosenberg Peter , Paré J.-Jacques
Published: March 2008

The OA-11 dam on the Eastmain River in the James Bay Region of northern Quebec was designed without conventional cofferdams. The river section of the dam was constructed by end-dumping and dozer pushing of granular fill and achieving closure and diversion of the river through a spillway located in a rock abutment on the south bank.The fill was then compacted by using the vibroflotation method. The fill thickness varied from 4.5 to 15 m, the compacted area being 68 000 m2 while the volume was about 725 000 m3.This paper gives the properties of the fill, the equipment used for compaction, the control method used to assure compliance with specifications, and the results of the compaction programme. Keywords: dam construction, compaction, density, vibroflotation, equipment.
Fracture frequency in mudrocks: an example from the Queenston Formation of southern Ontario
Authors: Russell D. J. , Harman J.
Published: March 2008

In weathered surface exposures of the Queenston Formation (a red mudrock of Upper Ordovician age), an important fracture type appears as curved partings of generally low dip. Excavation of these fractures shows them to be continuous (for many metres), contorted, ranging in orientation from horizontal to vertical, and to be closely associated with small-scale slickensided surfaces. Evidence of water movement along these fractures is present. They are considered to be large soft sediment deformation shears, their present aperture being due to stress release.Detailed examination of core samples of the formation reveals numerous small slickensided shears, present throughout the unit but sometimes only revealed by core breakage. The frequency of these slickensides correlates directly with clay content and inversely with calcite content. In addition, their frequency is inversely correlated with point load strength index. Engineering geologists normally would not advocate the prediction of fracture frequency of a geological material from a strength index test or a compositional parameter. However, evidence presented here suggests that such a prediction is possible for certain fracture types in this, and perhaps other, red mudrocks. Key words: red mudrock, slickensided fracture frequency, point load test, calcite content.
Controlling constriction sizes of granular filters
Authors: Kenney T. C. , Chahal R. , Chiu E. , Ofoegbu G. I. , Omange G. N. , Ume C. A.
Published: March 2008

Controlling constriction size Dc* is a size characteristic of the void network in a granular filter and is equal to the diameter of the largest particle that can possibly be transported through the filter by seepage. It provides a quantitative measure of the size of the channels within a granular filter and it is an aid to understanding filtration by drawing attention to processes occurring within the void network. Results of analytical and experimental studies indicate that Dc* is largely independent of the shape of the filter's grain size distribution curve and thickness and can be related to the size of particles in the fine fraction.To transport particles equal in size to Dc* through a granular medium requires mild vibration and seepage velocities corresponding to values of hydrodynamic number R′ ≥ 10. Smaller velocities will only transport particles smaller than Dc*. Filtration capability is thus dependent on both Dc* of the filter and hydrodynamic conditions within the filter.It is shown that knowledge of Dc* can be helpful when designing filters to protect cohesionless and cohesive soils. Key words: filter, constriction size, hydrodynamics, tests, design.
Pénétromètre à chute libre: Impact et pénétration dans des argiles reconstituées
Authors: Levacher D.
Published: March 2008

The use of a free-fall penetrometer for the determination of the in situ mechanical properties of reconstituted clays is presented. The penetrometer is equipped with an accelerometer for measuring continuously the acceleration or the deceleration. The equipment is relatively simple and the test is fast. The usefulness of such a test is demonstrated, and its adaptation to in situ testing is easy to achieve. Laboratory tests indicate that the shear strength can be directly computed as a function of depth. The penetrometer, as developed, can reach a depth of 0.50 m, but it is possible to achieve greater depths with some modifications. The results presented pertain to a few test series on reconstituted clays, with impact velocities up to 8 m/s. Key words: penetrometer, impact, reconstituted clays, tests, dynamic resistance, cohesion. [Journal translation]
Controlled displacement-rate in situ shear tests with pore pressure measurements
Authors: Shuri F. S. , Driscoll D. D. , Garner S. J.
Published: March 2008

Two large-scale in situ shear tests were conducted at a damsite in western Canada. The rock at the site is a Cretaceous shale containing a thin clay seam tentatively identified as a bedding-plane shear zone. The material in this seam is significantly weaker than the intact rock and influences the design of certain features of the dam and structures. In order to provide shear strength data for design, two large blocks of shale were sheared along the clay seam. These tests differed from conventional in situ shear tests in two significant ways: the rate of shear displacement was strictly controlled, and pore pressures (both positive and negative) in the shear zone were carefully monitored throughout the test. This note presents the material properties of the shear zone, describes the test equipment and techniques, and discusses the results obtained. Key words: shear strength, in situ testing, pore pressure, shale.
Co-operative hydration of the carbonyl group — "Bifunctional catalysis" by 2-hydroxypyridine is achieved via a dihydrate of 2-pyridone
Authors: Hsieh Yih-Huang , Weinberg Noham , Wolfe Saul
Published: March 2008

Although 2-hydroxypyridine is one thousand times less acidic than its isomer 3-hydroxypyridine and ten million times less acidic than acetic acid, in the aqueous hydration of 1 mol/L acetone at 298 K the catalytic effect of added 2-hydroxypyridine is 600 000 times greater than that of 3-hydroxypyridine and 20 times greater than that of acetic acid. This experimental result is successfully reproduced by a theoretical treatment that assumes that solvent molecules participate in a cyclic cooperative mechanism that avoids the formation of charged intermediates. However, the theoretical treatment does not support the seemingly obvious conclusion that the origin of the enhanced catalytic activity of 2-hydroxypyridine lies in its bifunctional nature. Rather, this enhanced catalytic activity can be traced to the exceptional thermodynamic stability of the principal reactant complex, which contains a dihydrate of 2-pyridone.Key words: hydration, isotope shift, bifunctional, cooperativity, cyclic mechanism, ab initio, SCRF
Ketonization of the unusually acidic elongated enol generated by flash photolytic decarboxylation of p-formylphenylacetic acid in aqueous solution
Authors: Chiang Yvonne , Kolmakov Kirill , Kresge A Jerry
Published: March 2008

Rates of photolysis of p-formylphenylacetic acid were measured flash photoytically in perchloric acid and sodium hydroxide solutions, and also in acetic acid, biphosphate ion, and tris-(hydroxymethyl)methaneammonium ion buffers, using H2O and D2O as solvents. The results provide rate profiles and solvent isotope effects, which indicate that photolysis occurs through an elongated enol intermediate. This enol is unusually strongly acidic, by some two to three pQa units, when compared with simple non-elongated enols.Key words: flash photolysis, elongated enols, rate profiles, solvent isotope effects.
Bismuth(III)-catalyzed rapid and highly efficient synthesis of 2-aryl-1-arylmethyl-1H-benzimidazoles in water
Authors: Yadav J S , Reddy B.V. Subba , Premalatha K , Shankar K Shiva
Published: March 2008

2-Aryl-1-arylmethyl-1H-benzimidazoles are prepared in high yields under extremely mild conditions via the condensation of aryl-1,2-diamines with aromatic aldehydes using 10 mol% of bismuth triflate in water. The use of water and readily available bismuth triflate makes this process quite simple, more convenient, and environment-friendly.Key words: aryl-1,2-diamines, aromatic aldehydes, bismuth catalysis, benzimidazoles.
Prodigiosin synthesis with electron rich 2,2′-bipyrroles
Authors: Jolicoeur Benoit , Lubell William D
Published: March 2008

The prodigiosins possess a linear tripyrrolic scaffold with the A and B pyrrolic rings connected directly in a bipyrrole unit, and the B and C rings joined in a dipyrrin. These red streptomycete metabolites exhibit among other activities, antitumor, antimicrobial, and immunomodulating properties. A new prodigiosin synthesis has been developed that employs electron rich 2,2′-bipyrroles. In particular, undecylprodigiosin and PNU-156804 were synthesized by condensations of 4-methoxy and 4-benzyloxy 2,2′-bipyrroles, 20a and 20b, respectively, with 5-undecylpyrrole-2-carboxaldehyde in 75% and 83% yields. The 4-alkoxy-2,2′-bipyrroles were synthesized from 4-alkoxypyrrolyl butenyl ketones (15a and 15b), which were made by a novel one-pot process from 2-acyl-N-(PhF)pyrrolidin-4-one (13) [PhF = 9-(9-phenylfluorenyl)] using PhFNa in the presence of alkyl halide. A sequence of alkoxy pyrrole 15a and 15b protection, olefin oxidation, Paal–Knorr condensation, and deprotection gave the requisite 4-alkoxy-2,2′-bipyrroles (20). This route offers utility for making 4-alkoxybipyrroles as well as prodigiosins with diversity at the 6-position of the linear tripyrrolic skeleton.Key words: prodigiosin, pyrrole, bipyrrole, PNU-156804, undecylprodigiosin.
Synthesis, characterization, and X-ray structures of three iridium(III)-hydrido-cyclometallated-imine complexes, including the first reported hydrido-(η1-imine)-Ir complex
Authors: Lorenzini Fabio , Marcazzan Paolo , Patrick Brian O , James Brian R
Published: March 2008

Reactions of cis,trans,cis-[Ir(H)2(PPh3)2(solv)2]PF6 (solv = MeOH or Me2CO) with the imines HN=CPh2, (o-HOC6H4)C(Me)=NCH2Ph, and PhC(H)=N(p-F-C6H4) in MeOH or acetone under Ar give the complexes [IrH{NH=C(Ph)(o-C6H4)}(NH=CPh2)(PPh3)2]PF6 (3), [IrH{PhCH2N=C(Me)(o-C6H3OH)}(solv)(PPh3)2]PF6, where solv = MeOH (4) or Me2CO (4a), and [IrH{N(p-F-C6H4)=CH(o-C6H4)}(Me2CO)(PPh3)2]PF6 (5a), which have been isolated and characterized. The imine (C6F5)C(H)=NPh is unreactive toward the Ir precursors. The X-ray structures of 3, 4·2MeOH, and 5a·1/2Me2CO show an η2-N,C-imine moiety coordinated via the N atom and an orthometallated-C atom. Complex 3, which contains both an orthometallated imine and an η1-imine, is the first structurally characterized hydrido-(η1-imine)-Ir complex. Comparisons are made with data for the corresponding Rh systems.Key words: iridium, hydride complexes, imines, fluoroimines, phosphine complexes, orthometallation, crystallography, NMR spectroscopy.
Effect of gap harvesting on epiphytes and bark-dwelling arthropods in the Acadian forest of central Maine
Authors: Miller Kathryn M. , Wagner Robert G. , Woods Stephen A.
Published: March 2008

Using a long-term silvicultural experiment, we (i) investigated how epiphyte and arthropod communities were affected by height on the stem, bark texture, and stem diameter of red maple ( Acer rubrum L.) trees, (ii) examined how harvest gaps influenced epiphyte and arthropod communities on red maple boles, and (iii) explored whether these effects influenced the relationship between the epiphyte and arthropod communities. Arthropod and epiphyte assemblages dwelling on the bark of red maple trees located in undisturbed forest and harvest gaps varied with height. Bryophytes, Cladonia spp., and cyanolichens were most abundant near the base of the tree, while noncyano, foliose lichens and fruticose lichens were most abundant 4–6 m above the ground. Acari, Araneae, and Collembola were most abundant near the base of the tree, while Diptera were most abundant above 2 m. A previously undocumented assemblage of dipterans (flies), primarily in the suborder Nematocera, was found. Gap harvesting reduced the abundance of bryophytes, Collembola (springtails), Araneae (spiders), and total arthropods on the bark of red maple. Canonical correlation analysis revealed a positive association between bryophytes, Collembola, and Araneae. A strong correlation between Collembola and Araneae suggested a possible trophic interaction that may be affected by gap harvesting through a reduction in bryophyte abundance.
Impacts of elevated ozone and nitrogen on growth and photosynthesis of European aspen (Populus tremula) and hybrid aspen (P. tremula × Populus tremuloides) clones
Authors: Häikiö Elina , Freiwald Vera , Silfver Tarja , Beuker Egbert , Holopainen Toini , Oksanen Elina
Published: March 2008

Impacts of elevated tropospheric ozone and soil nitrogen amendment on two native European aspen ( Populus tremula L.) and eight hybrid aspen (P. tremula L. × Populus tremuloides Michx.) clones were studied in a free-air ozone exposure system. Potted saplings were exposed to ambient (ca. 20 ppb) or 1.5× ambient ozone and two levels of soil nitrogen (39 and 78 kg N·ha–1·year–1 in the first year, 60 and 140 kg N·ha–1·year–1 in the second year for low-nitrogen and high-nitrogen treatments, respectively) over two growing seasons. The plants were measured for photosynthesis, chlorophyll fluorescence, and biomass accumulation. Ozone decreased leaf-level net photosynthesis (Asat) in particular early in the growing season and maximum quantum yield of photosystem II (Fv/Fm) at the end of the growing season. Nitrogen amendment increased the growth of all plant parts and mitigated the adverse ozone effects. There were significant differences in ozone responses among the clones, and we were able to cluster the clones into sensitivity groups based on their growth responses. The most ozone-tolerant genotypes were hybrid aspen clones, indicating that populations that have already experienced selection for ozone-tolerant genotypes should be used to cross-breed with ozone-sensitive populations to achieve tolerance of a climate with increasing tropospheric ozone concentrations.
Estimating optimum sampling size to determine weighted core specific gravity of planted loblolly pine
Authors: Jordan Lewis , Schimleck Laurence R. , Clark Alexander , Hall Daniel B. , Daniels Richard F.
Published: March 2008

Data from a variability study of loblolly pine ( Pinus taeda L.) based on weighted core specific gravity (WCSG) were examined to show how costs and variance estimates are used in designing efficient sampling strategies. Increment cores for the determination of WCSG were taken from 3957 trees across six distinct physiographic regions in the southeastern United States. More variability was found to exist among stands than within stands. This indicates that reducing the variation of the mean of WCSG can be accomplished by sampling more stands and fewer trees in the region of interest. The number of stands and trees to sample is dictated by the maximum allowable cost and the precision required of the sample mean, and formulas are given for such calculations. The estimate of among-stand variability was found to be similar among the regions of interest, whereas larger within-stand variation was found to exist in the South Atlantic and Hilly regions. The standard error of the mean was found to increase with an increase in the age at which the stand was sampled. When sampling across multiple stands (at any age), little if any gain in the precision of the standard error of the mean is gained by sampling more than 15 trees. In the general case where one is interested only in the value of WCSG in one stand and precision or cost–time factors are not of consideration, it would suffice to sample between 45 and 55 trees at any age.
Impacts of postfire salvage logging on understory plant communities of the boreal mixedwood forest 2 and 34 years after disturbance
Authors: Kurulok Stephanie E. , Macdonald S. Ellen
Published: March 2008

We compared understory vegetation composition and richness in aspen-dominated boreal mixedwood forest stands in Alberta, Canada, that had been burned by wildfire with those that burned and were subsequently salvage logged. Stands were examined at early and midsuccessional (2 and 34 years after disturbance(s), respectively) developmental stages. In comparison with wildfire stands, understory communities of early successional salvage-logged stands were characterized by greater species richness, weedy species presence, higher shrub abundance, and lower abundances of fire-specialist seed bank species. In constrained ordination, the understory community of early successional wildfire stands was related to greater canopy cover, sapling density, and moss depth, whereas that of salvage-logged stands was related to greater light, volume of downed deadwood, and litter and organic matter. Longer term effects of salvage logging on the understory community were minimal and, instead, reflected the influence of forest canopy redevelopment. In midsuccessional stands, understory composition was related to conifer density, litter cover, soil moisture, organic layer depth, tall shrub density, and bryophyte-covered microsite cover. Postfire salvage logging can have substantial short-term effects on the postfire understory plant community; in the longer term, effects will depend to a large extent on the influence of harvesting and subsequent management on canopy redevelopment.
Regeneration development under shelterwoods in a lowland red spruce – balsam fir stand
Authors: Pothier David , Prévost Marcel
Published: March 2008

The shelterwood system can be used to establish regeneration and to improve the growing conditions of seedlings and, thereby, increase their probability of survival after final harvest. To determine the cutting intensity that best promotes the development of red spruce ( Picea rubens Sarg.) regeneration, an experiment, including four repetitions of five treatments (control; low, moderate, and heavy partial cuttings; and clear-cutting), was established in a lowland stand in Quebec, Canada, dominated by red spruce and balsam fir ( Abies balsamea (L.) Mill.). Regeneration development responses to treatments varied according to cutting intensity, species, and position relative to the skidding trails in the residual stands. Ten years after treatment, red spruce seedlings were well established but were smaller than those of balsam fir and deciduous species. Red spruce seedling height was generally greater in partial-cut skidding trails, as was light availability. However, in clearcuts, the size of red spruce seedlings established in skidding trails seemed to be negatively affected by the considerable quantity of woody debris strewn over them. Among the partial-cut treatments, tree regeneration leaf biomass was the highest where 60% of the initial basal area was removed. Thus, this treatment is an attractive alternative to clear-cutting in such lowland stands where watering-up is anticipated after final harvest.
Blocked Autophagy Sensitizes Resistant Carcinoma Cells to Radiation Therapy
Authors: Apel Anja , Herr Ingrid , Schwarz Heinz , Rodemann H. Peter , Mayer Andreas
Published: March 2008

Autophagy or “self eating” is frequently activated in tumor cells treated with chemotherapy or irradiation. Whether autophagy represents a survival mechanism or rather contributes to cell death remains controversial. To address this issue, the role of autophagy in radiosensitive and radioresistant human cancer cell lines in response to γ-irradiation was examined. We found irradiation-induced accumulation of autophagosomes accompanied by strong mRNA induction of the autophagy-related genes beclin 1, atg3, atg4b, atg4c, atg5, and atg12 in each cell line. Transduction of specific target-siRNAs led to down-regulation of these genes for up to 8 days as shown by reverse transcription-PCR and Western blot analysis. Blockade of each autophagy-related gene was associated with strongly diminished accumulation of autophagosomes after irradiation. As shown by clonogenic survival, the majority of inhibited autophagy-related genes, each alone or combined, resulted in sensitization of resistant carcinoma cells to radiation, whereas untreated resistant cells but not sensitive cells survived better when autophagy was inhibited. Similarly, radiosensitization or the opposite was observed in different sensitive carcinoma cells and upon inhibition of different autophagy genes. Mutant p53 had no effect on accumulation of autophagosomes but slightly increased clonogenic survival, as expected, because mutated p53 protects cells by conferring resistance to apoptosis. In our system, short-time inhibition of autophagy along with radiotherapy lead to enhanced cytotoxicity of radiotherapy in resistant cancer cells. [Cancer Res 2008;68(5):1485–94]
A Human Breast Cell Model of Preinvasive to Invasive Transition
Authors: Rizki Aylin , Weaver Valerie M. , Lee Sun-Young , Rozenberg Gabriela I. , Chin Koei , Myers Connie A. , Bascom Jamie L. , Mott Joni D. , Semeiks Jeremy R. , Grate Leslie R. , Mian I. Saira , Borowsky Alexander D. , Jensen Roy A. , Idowu Michael O. , Chen Fanqing , Chen David J. , Petersen Ole W. , Gray Joe W. , Bissell Mina J.
Published: March 2008

A crucial step in human breast cancer progression is the acquisition of invasiveness. There is a distinct lack of human cell culture models to study the transition from preinvasive to invasive phenotype as it may occur “spontaneously” in vivo. To delineate molecular alterations important for this transition, we isolated human breast epithelial cell lines that showed partial loss of tissue polarity in three-dimensional reconstituted basement membrane cultures. These cells remained noninvasive; however, unlike their nonmalignant counterparts, they exhibited a high propensity to acquire invasiveness through basement membrane in culture. The genomic aberrations and gene expression profiles of the cells in this model showed a high degree of similarity to primary breast tumor profiles. The xenograft tumors formed by the cell lines in three different microenvironments in nude mice displayed metaplastic phenotypes, including squamous and basal characteristics, with invasive cells exhibiting features of higher-grade tumors. To find functionally significant changes in transition from preinvasive to invasive phenotype, we performed attribute profile clustering analysis on the list of genes differentially expressed between preinvasive and invasive cells. We found integral membrane proteins, transcription factors, kinases, transport molecules, and chemokines to be highly represented. In addition, expression of matrix metalloproteinases MMP9, MMP13, MMP15, and MMP17 was up-regulated in the invasive cells. Using small interfering RNA–based approaches, we found these MMPs to be required for the invasive phenotype. This model provides a new tool for dissection of mechanisms by which preinvasive breast cells could acquire invasiveness in a metaplastic context. [Cancer Res 2008;68(5):1378–87]
Chromosomal Breakpoints in Primary Colon Cancer Cluster at Sites of Structural Variants in the Genome
Authors: Camps Jordi , Grade Marian , Nguyen Quang Tri , Hörmann Patrick , Becker Sandra , Hummon Amanda B. , Rodriguez Virginia , Chandrasekharappa Settara , Chen Yidong , Difilippantonio Michael J. , Becker Heinz , Ghadimi B. Michael , Ried Thomas
Published: March 2008

Genomic aberrations on chromosome 8 are common in colon cancer, and are associated with lymph node and distant metastases as well as with disease susceptibility. This prompted us to generate a high-resolution map of genomic imbalances of chromosome 8 in 51 primary colon carcinomas using a custom-designed genomic array consisting of a tiling path of BAC clones. This analysis confirmed the dominant role of this chromosome. Unexpectedly, the position of the breakpoints suggested colocalization with structural variants in the human genome. In order to map these sites with increased resolution and to extend the analysis to the entire genome, we analyzed a subset of these tumors (n = 32) by comparative genomic hybridization on a 185K oligonucleotide array platform. Our comprehensive map of the colon cancer genome confirmed recurrent and specific low-level copy number changes of chromosomes 7, 8, 13, 18, and 20, and unveiled additional, novel sites of genomic imbalances including amplification of a histone gene cluster on chromosome 6p21.1-21.33 and deletions on chromosome 4q34-35. The systematic comparison of segments of copy number change with gene expression profiles showed that genomic imbalances directly affect average expression levels. Strikingly, we observed a significant association of chromosomal breakpoints with structural variants in the human genome: 41% of all copy number changes occurred at sites of such copy number variants (P < 2.2e−16). Such an association has not been previously described and reveals a yet underappreciated plasticity of the colon cancer genome; it also points to potential mechanisms for the induction of chromosomal breakage in cancer cells. [Cancer Res 2008;68(5):1284–95]
A Novel RET Kinase–β-Catenin Signaling Pathway Contributes to Tumorigenesis in Thyroid Carcinoma
Authors: Gujral Taranjit S. , van Veelen Wendy , Richardson Douglas S. , Myers Shirley M. , Meens Jalna A. , Acton Dennis S. , Duñach Mireia , Elliott Bruce E. , Höppener Jo W.M. , Mulligan Lois M.
Published: March 2008

The RET receptor tyrosine kinase has essential roles in cell survival, differentiation, and proliferation. Oncogenic activation of RET causes the cancer syndrome multiple endocrine neoplasia type 2 (MEN 2) and is a frequent event in sporadic thyroid carcinomas. However, the molecular mechanisms underlying RET's potent transforming and mitogenic signals are still not clear. Here, we show that nuclear localization of β-catenin is frequent in both thyroid tumors and their metastases from MEN 2 patients, suggesting a novel mechanism of RET-mediated function through the β-catenin signaling pathway. We show that RET binds to, and tyrosine phosphorylates, β-catenin and show that the interaction between RET and β-catenin can be direct and independent of cytoplasmic kinases, such as SRC. As a result of RET-mediated tyrosine phosphorylation, β-catenin escapes cytosolic down-regulation by the adenomatous polyposis coli/Axin/glycogen synthase kinase-3 complex and accumulates in the nucleus, where it can stimulate β-catenin–specific transcriptional programs in a RET-dependent fashion. We show that down-regulation of β-catenin activity decreases RET-mediated cell proliferation, colony formation, and tumor growth in nude mice. Together, our data show that a β-catenin–RET kinase pathway is a critical contributor to the development and metastasis of human thyroid carcinoma. [Cancer Res 2008;68(5):1338–46]
Linking Antibody Fc Domain to Endostatin Significantly Improves Endostatin Half-life and Efficacy
Authors: Lee Tong-Young , Tjin Tham Sjin Robert M. , Movahedi Shahla , Ahmed Bissan , Pravda Elke A. , Lo Kin-Ming , Gillies Stephen D. , Folkman Judah , Javaherian Kashi
Published: March 2008

Purpose: The half-life of the antiangiogenic molecule endostatin that has been used in clinical trial is short (∼2 h). In addition, ∼50% of the clinical grade endostatin molecules lack four amino acids at their NH2 termini. Lack of these amino acids gives rise to a molecule that is devoid of zinc, resulting in no antitumor activity. Our goal was to develop a new version of endostatin that does not show such deficiency.

Experimental Design: A recombinant human endostatin conjugated to the Fc domain of IgG was constructed and expressed in mammalian cell culture. The presence of Fc has been shown by previous investigators to play a major role in increasing the half-life of the molecule. Fc-endostatin was tested in tumor-bearing mice, and its half-life was compared with the clinical grade endostatin.

Results: The antitumor dose of Fc-endostatin was found to be ∼100 times less than the clinical grade endostatin. The half-life of Fc-endostatin in the circulation was found to be weeks rather than hours, as observed for endostatin alone. In addition, a U-shaped curve was observed for antitumor activity of endostatin as a function of endostatin concentration delivered to the animals.

Conclusion: Fc-endostatin is a superior molecule to the original clinical endostatin. Due to its long half-life, the amount of protein required is substantially reduced compared with the clinically tested endostatin. Furthermore, in view of the U-shaped curve of efficacy observed for endostatin, we estimate that the requirement for Fc-endostatin is ∼700-fold less than endostatin alone. The half-life of endostatin is similar to that of vascular endothelial growth factor–Trap and Avastin, two other antiangiogenic reagents. We conclude that a new clinical trial of endostatin, incorporating Fc, may benefit cancer patients.
Immunohistochemical Analysis of Phosphotyrosine Signal Transducer and Activator of Transcription 3 and Epidermal Growth Factor Receptor Autocrine Signaling Pathways in Head and Neck Cancers and Metastatic Lymph Nodes
Authors: Seethala Raja R. , Gooding William E. , Handler Phoebe N. , Collins Bobby , Zhang Qing , Siegfried Jill M. , Grandis Jennifer R.
Published: March 2008

Purpose: To determine the effect of tyrosine-phosphorylated signal transducer and activator of transcription 3 (pSTAT3) immunoexpression on survival in two independent cohorts of patients with squamous cell carcinoma of the head and neck (SCCHN) and to evaluate pSTAT3, transforming growth factor-α (TGF-α), epidermal growth factor receptor (EGFR), and gastrin-releasing peptide receptor (GRPR) expression in matched tumor and lymph node metastases in one of these cohorts.

Experimental Technique: Immunostaining for pSTAT3, TGF-α, EGFR, and GRPR was done in two SCCHN cohorts (cohort 1, 61 tumors; cohort 2, 69 paired primary tumors and lymph node metastases). Semiquantitative scores derived from the product of staining intensity (scale 0-3) score and percentage of positive tumor cells were correlated with clinical outcome.

Results: Immunoexpression of pSTAT3 did not correlate with clinical outcome in either cohort (cohort 1, P = 0.914; cohort 2, P = 0.312). In cohort 2, TGF-α and EGFR expression in the primary tumors showed some association with decreased disease-free survival (P = 0.0306 and P = 0.0985, respectively). Both pSTAT3 and EGFR showed a correlation of expression between tumor and matched lymph node metastasis (P < 0.0001 and P = 0.0046, respectively). In addition, the expression of EGFR and GRPR in the primary tumors correlated with TGF-α expression in paired nodal metastases (P = 0.0043 and P = 0.0268, respectively). In the nodal metastases, TGF-α expression correlated with EGFR expression (P = 0.0069). In primary tumors, GRPR expression correlated with TGF-α and EGFR expression (P = 0.0378 and P = 0.0026, respectively).

Conclusions: These findings support an autocrine signaling pathway involving TGF-α, EGFR, and pSTAT3 in metastatic SCCHN as well as transactivation of EGFR by GRPR via TGF-α, but fails to identify an independent prognostic role for pSTAT3 immunoexpression.
Quantitative Monitoring of Adenocarcinoma Development in Rodents by Magnetic Resonance Imaging
Authors: Garbow Joel R. , Wang Min , Wang Yian , Lubet Ronald A. , You Ming
Published: March 2008

Purpose: Accurately following the time course of tumor progression and response to therapy in animal models of cancer is key to the development of better chemopreventive and chemotherapeutic agents. The goal of this work was to monitor quantitatively the development and progression of adenocarcinoma in a time course study of mice treated with the carcinogen urethane using in vivo small-animal magnetic resonance imaging (MRI).

Experimental Design: Mice treated with a single dose of urethane were imaged at four time points beginning 8 months after treatment. High-resolution images of mouse lung were obtained in vivo using respiratory-gated MRI methods. Individual tumors were manually segmented and their volumes calculated. At the end of the study, mice were euthanized and MRI tumor quantification was validated by histology and histopathology.

Results: Tumors as small as 0.4 mm in diameter can be detected and quantitatively measured in mice by in vivo MRI. Total tumor burden increased consistently in all mice studied, whereas the growth rate of individual tumors varied widely. The positions and diameters of individual tumors as measured by MRI correlated well with histology results. Histologic study of large, rapidly growing tumors showed that these were adenocarcinomas, whereas small, slowly growing lesions were predominantly adenomas.

Conclusions: Longitudinal in vivo MRI is a powerful modality that can be of great aid in elucidating the factors that control the onset of lung tumors and can serve as a platform for the development and preclinical testing of novel therapies having a high likelihood of efficacy in human clinical trials.
Higher Levels of the Anti-inflammatory Protein CC10 Are Associated with Improvement in Bronchial Dysplasia and Sputum Cytometric Assessment in Individuals at High Risk for Lung Cancer
Authors: Chen Jiping , Lam Stephen , Pilon Aprile , McWilliams Annette , MacAulay Calum , Szabo Eva
Published: March 2008

Purpose: CC10, a 10-kDa anti-inflammatory protein secreted by bronchiolar Clara cells, is infrequently expressed in non–small cell lung cancer and its overexpression in non–small cell lung cancer cell lines results in a less malignant phenotype. Several lines of evidence have shown that bronchial dysplasia and sputum atypia are predictors of lung cancer. We investigated whether changes in CC10 expression correlate with regression of bronchial dysplasia and/or improvement in sputum abnormalities as measured by image cytometry.

Experimental Design: High-risk smokers enrolled in a chemoprevention trial underwent serial bronchoscopies with biopsies and bronchoalveolar lavage (BAL) collection, sputum assessment by image cytometry, and blood collection. CC10 was measured by competitive ELISA in BAL and plasma. Logistic regression analyses were done to determine the associations between CC10 levels and the improvement in bronchial dysplasia and sputum cytometric assessment.

Results: The net change in the BAL CC10 levels in subjects with improved bronchial lesions or improved sputum cytometry assessment was significantly higher than in those without improvement (P < 0.05). The odds ratio (95% confidence interval) associated with 1-unit increase in CC10 was 2.72 (1.31-5.64) for regression of dysplastic lesions and 2.94 (1.22-7.05) for improvement in sputum cytometry assessment after multivariate adjustment. Plasma CC10 was not significantly associated with either outcome.

Conclusions: Higher BAL CC10 levels are significantly correlated with regression of bronchial dysplasia and improvement in sputum cytometry assessment in smokers with high lung cancer risk. Whether CC10 levels can predict clinical outcomes among high-risk populations warrants further investigation.