Filament-induced laser machining (FILM)

Laser filamentation provides high intensity plasma strings of micrometric diameters and lengths of tens of centimeters. We demonstrate that these filaments can be used for remotely drilling and cutting metals and biological materials such as flesh and bones. Since no tight focusing is needed, complex 3D shapes can be machined without any adjustment of the laser while processin

Allowable Bending Strength Enhancement of 2 By 4 Lumber By Tension and Compression Proofloading

Simple 5th percentile and reliability analysis methods were used to evaluate increases in allowable bending strength from proofloading in tension and compression. The analysis included the use of realistic load data for residential roof and floor trusses, and combined stress present in truss chords was given consideration as part of the reliability analysis. Proofloading in tension or in compression both produced significant increases in allowable bending strength for 2 by 4 1650f-1.5E hem-fir. Proofloading in tension to a target 15% breakage level, or 2,838 psi, yielded for the survivors an increase of 72% in allowable bending strength. The allowable bending strength increased 60% because of compressive proofloading to a target 15% breakage level. Since relatively small sample sizes were used, the results are not definitive but provide justification for a comprehensive study

Replicate Fire Endurance Tests of an Unprotected Wood Joist Floor Assembly

To encourage new developments in building technology, a solid basis for building code requirements is needed. Fire endurance is a code requirement, yet no objective procedure exists for computing a structure's chances of failing (degree of risk) in a fire. However, a model for predicting the fire endurance of part of a structure, a conventional unprotected wood joist floor, is available. The aim of this study was to determine the fire endurance performance of an unprotected wood joist floor for use in the model.Eleven ASTM Standard E 119 floor tests were conducted. All the floors were 2 by 10 Douglas-fir wood joists, sixteen inches on center with 23/32-inch-thick plywood as the floor sheathing. In addition to one trial test, five tests were conducted using a live load of 11.35 lb/ft2. For the other five tests, the live load was 79.2 lb/ft2. Twenty joists were tested for modulus of elasticity and modulus of rupture.The joist population had a mean modulus of rupture of 5.280 lb/in.2 and a mean modulus of elasticity of 1,530,000 lb/in.2. For the five floors loaded to 11.35 lb/ft2, the mean time for initial joist failure was 17.9 min with a coefficient of variation (COV) of 3.7%. For the five floors loaded to 79.2 lb/ft2, the mean time was 6.5 min with a COV of 11.6%. Based on linear interpolation of these results, first joist failure would have occurred in 13.1 min if a 40 lb/ft2 live load had been used, which is the typical live loading specified in the building codes for residential one- and two-family dwellings.As a result of this study, fire-resistance performance of a wood floor is known for a specific population of wood joists with known structural properties. These results can be used to verify and revise the model for predicting fire endurance

Exploration of a rare population of Chinese chestnut in North America: stand dynamics, health and genetic relationships

With the transport of plants around the globe, exotic species can readily spread disease to their native relatives; however, they can also provide genetic resistance to those relatives through hybrid breeding programmes. American chestnut (Castanea dentata) was an abundant tree species in North America until its decimation by introduced chestnut blight. To restore chestnut in North America, efforts are ongoing to test putative blight-resistant hybrids of Castanea dentata and Chinese chestnut (Castanea mollissima), but little is known about the ecology of C. mollissima. In a forest in northeastern USA in which C. mollissima has become established, we explored questions of stand dynamics, health and genetic relationships of C. mollissima offspring to an adjacent parent orchard. We found that C. mollissima was adapted and randomly distributed among native species in this relatively young forest. The genetics of the C. mollissima population compared with its parents indicated little effect of selection pressure as each of the parent trees contributed at least one offspring. The ease with which this exotic species proliferated calls to question why C. mollissima is rare elsewhere in forests of North America. It is likely that a time window of low animal predation allowed seedlings to establish, and the shallow soil at this site limited the maximum forest canopy height, permitting the characteristically short-statured C. mollissima to avoid suppression. Our results indicate that because C. mollissima exhibited pioneer species characteristics, hybrids between C. mollissima and C. dentata have the potential to be successful pioneer species of future forests in North America, and we challenge the paradigm that exotic tree species are wholly detrimental to native biodiversity. We contend that exotic tree species should be assessed not only by their level of threat to native species, but also by their potential positive impacts on ecosystems via hybrid breeding programmes

Toward Guidelines for Harvest Intensities and Regeneration Targets with Minimal Impact Upon Retained Genetic Diversity in Central Hardwood Tree Species

There is an urgent need for a coordinated and systematic approach to the in situ conservation of the genetic resources of commercially important forest tree species in the Central Hardwoods. Effective in situ management of genetic resources would benefit from clear guidelines for how many adult trees can be harvested with minimal impact on allelic diversity. We are constructing a computer model for this purpose, and present preliminary results based upon replicate harvests of a virtual forest stand consisting of 200 adult trees. Our model explores how much regeneration is needed so that there is no more than a 10 percent risk of retaining less than 90 percent of the original allelic diversity. In the absence of regeneration, up to 55 percent of the adult trees can be harvested without exceeding the 10 percent risk level. At higher harvest intensities, locally-derived regeneration is needed to replace the alleles removed from the adult population. When all 200 adult trees are harvested, the 10 percent risk level is not exceeded if there are at least 116 regenerants, provided that these are derived from pre-harvest random mating among the adults. In the presence of substantial pollen flow from a genetically differentiated outside pollen source (e.g., 10-20 percent pollen flow), the minimum amount of regeneration needed is reduced. This indicates that outside pollen can be more efficient, relative to pollen from within the stand, at replacing alleles lost from the adult population

Proof Loading to Assure Lumber Strength

The control of within-mill variations in the strength distribution of a given structural grade of lumber is of growing concern to the wood industry. Recent studies have proposed the use of on-line proof loading procedures to maintain quality through the elimination of weak pieces.An experiment was conducted on one thousand two hundred pieces of 2 x 4 No. 2 Dense KD Southern pine to determine the effect of both single and reverse bending proof loads on the strength of lumber tested in both bending and tension parallel-to-grain. The specimens were separated into six groups, each containing two hundred pieces. A pair of control groups, single proof load groups, and reverse proof load groups were tested. One group in each pair was failed in bending, the other was in tension. During the testing, no damage due to the proof loading was detected.Probabilistic analysis of the data indicates that the bending strength of the single proof loaded specimens could be reduced by 12% and still remain as reliable as the control. Reverse proof loaded specimens could tolerate a reduction of 33%. The tensile strength for each single proof loaded member could tolerate a reduction of 13%, while reverse proof loaded specimens could face a decrease of 18% and maintain a level of safety equal to the related control. When using a bending proof load to assure lumber strength, it is necessary to use a higher proof load to assure tensile strength than would be needed just to assure bending strength

SAWA experiment ? properties of mineral dust aerosol as seen by synergic lidar and sun-photometer measurements

International audienceWe propose a method of retrieving basic information on mineral dust aerosol particles from synergic sun-photometer and multi-wavelength lidar measurements as well as from the observations of lidar light depolarisation. We use this method in a case study of mineral dust episode in Central Europe. Lidar signals are inversed with a modified Klett-Fernald algorithm. Aerosol optical depth measured with the sun-photometer allows to reduce uncertainties in the inversion procedure through which we estimate vertical profile of aerosol extinction. Next we assume that aerosol particles may be represented by ensemble of randomly oriented, identical spheroids. Having calculated vertical profiles of aerosol extinction coefficients for lidar wavelengths, we compute the profiles of local Angstrom exponent. We use laser beam depolarisation together with the calculated Angstrom exponents to estimate the shapes (aspect ratios) and sizes of the spheroids. Numerical calculations are performed with the transition matrix (T-matrix) algorithm by M. Mishchenko. The proposed method was first used during SAWA measurement campaign in Warsaw, spring 2005, to characterise the particles of desert dust, drifting over Poland with a southern-eastern wind (13?14 April). Observations and T-matrix calculations show that mode radii of spheroids representative for desert aerosols' particles are in the range of 0.15?0.3 ?m, while their aspect ratios are lower than 0.7 or larger than 1.7

YeATS - a tool suite for analyzing RNA-seq derived transcriptome identifies a highly transcribed putative extensin in heartwood/sapwood transition zone in black walnut [version 2; referees: 3 approved]

The transcriptome provides a functional footprint of the genome by enumerating the molecular components of cells and tissues. The field of transcript discovery has been revolutionized through high-throughput mRNA sequencing (RNA-seq). Here, we present a methodology that replicates and improves existing methodologies, and implements a workflow for error estimation and correction followed by genome annotation and transcript abundance estimation for RNA-seq derived transcriptome sequences (YeATS - Yet Another Tool Suite for analyzing RNA-seq derived transcriptome). A unique feature of YeATS is the upfront determination of the errors in the sequencing or transcript assembly process by analyzing open reading frames of transcripts. YeATS identifies transcripts that have not been merged, result in broken open reading frames or contain long repeats as erroneous transcripts. We present the YeATS workflow using a representative sample of the transcriptome from the tissue at the heartwood/sapwood transition zone in black walnut. A novel feature of the transcriptome that emerged from our analysis was the identification of a highly abundant transcript that had no known homologous genes (GenBank accession: KT023102). The amino acid composition of the longest open reading frame of this gene classifies this as a putative extensin. Also, we corroborated the transcriptional abundance of proline-rich proteins, dehydrins, senescence-associated proteins, and the DNAJ family of chaperone proteins. Thus, YeATS presents a workflow for analyzing RNA-seq data with several innovative features that differentiate it from existing software