Scaling studies of solar pumped lasers

A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow

How Overdrying Wood Reduces Its Bonding to Phenol-Formaldehyde Adhesives: A Critical Review of the Literature. Part I. Physical Responses

This review critically evaluates literature on the ways in which excessive drying (overdrying) inactivates wood surfaces to bonding, primarily for phenolic adhesives. In Part I of a two-part review, three inactivation mechanisms involving physical responses to overdrying are considered: (1) exudation of extractives to the surface, which lowers the wettability or hides the surface; (2) reorientation of wood surface molecules, which reduces wettability or places for bonding; and (3) irreversible closure of large micropores in cell walls. I believe that extensive evidence from wood bonding and paper sizing research supports the mechanism of extractives-induced low wettability as the cause for inactivation of Douglas-fir and southern pines. Molecular reorientation and irreversible micropore closure are proposed wood inactivation mechanisms that involve loss of wettability and bonding sites

A comparison of various methods for determining confidence factors within an expert system

http://www.worldcat.org/oclc/2265261

Improving the fatigue resistance of adhesive joints in laminated wood structures

The premature fatigue failure of a laminated wood/epoxy test beam containing a cross section finger joint was the subject of a multi-disciplinary investigation. The primary objectives were to identify the failure mechanisms which occurred during the finger joint test and to provide avenues for general improvements in the design and fabrication of adhesive joints in laminated wood structures

Cure of Phenol-Formaldehyde Adhesive in the Presence of CCA-Treated Wood by Differential Scanning Calorimetry

Chromated copper arsenate (CCA) preservatives interfere with bond formation of phenolic-based adhesives on CCA-treated southern pine. Ions of chromium (Cr+3) and copper (Cu+2) are known to complex with phenol and formaldehyde, affecting the rate of cure of the resin. Differential scanning calorimetry (DSC) was used to thermally analyze the cure of a commercial phenol-formaldehyde adhesive in the presence or CCA-treated wood, solutions of CCA preservative, and solutions of model compounds containing ions of Cr+6, Cr+3, Cu+2, and As+5. The DSC thermograms indicated that free metallic ions in solution can accelerate the cure of a portion of the adhesive at less than normal temperatures. However, when the CCA preservative was chemically "fixed" within the southern pine wood, accelerated cure of the adhesive did not occur

Book Review

non

FARM POLICY FOR THE 1970'S

Agricultural and Food Policy,

Observation of strongly enhanced photoluminescence from inverted cone-shaped silicon nanostuctures

Silicon nanowires (SiNWs) attached to a wafer substrate are converted to inversely tapered silicon nanocones (SiNCs). After excitation with visible light, individual SiNCs show a 200-fold enhanced integral band-to-band luminescence as compared to a straight SiNW reference. Furthermore, the reverse taper is responsible for multifold emission peaks in addition to the relatively broad near-infrared (NIR) luminescence spectrum. A thorough numerical mode analysis reveals that unlike a SiNW the inverted SiNC sustains a multitude of leaky whispering gallery modes. The modes are unique to this geometry and they are characterized by a relatively high quality factor (Q ~ 1300) and a low mode volume (0.2 < (λ/neff)3 < 4). In addition they show a vertical out coupling of the optically excited NIR luminescence with a numerical aperture as low as 0.22. Estimated Purcell factors Fp ∝ Q/Vm of these modes can explain the enhanced luminescence in individual emission peaks as compared to the SiNW reference. Investigating the relation between the SiNC geometry and the mode formation leads to simple design rules that permit to control the number and wavelength of the hosted modes and therefore the luminescent emission peaks

Probing spacetime foam with extragalactic sources

Due to quantum fluctuations, spacetime is probably ``foamy'' on very small scales. We propose to detect this texture of spacetime foam by looking for core-halo structures in the images of distant quasars. We find that the Very Large Telescope interferometer will be on the verge of being able to probe the fabric of spacetime when it reaches its design performance. Our method also allows us to use spacetime foam physics and physics of computation to infer the existence of dark energy/matter, independent of the evidence from recent cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several references added; very useful comments and suggestions by Eric Perlman incorporate