Creating a baseline radiological standard for the waste isolation pilot plant underground

The Waste Isolation Pilot Plant (WIPP) is a deep underground geological repository for defense transuranic wastes. The creation of a full baseline radiological standard for the WIPP underground is essential in order to evaluate and account for the influence of the naturally occurring radioactive materials, and to prepare for any suspected contamination or the very unlikely event of a real accident scenario. In this report, we describe the establishment of the baseline information using the gamma background dose rate measurements and the salt rib smears of surface removable alpha and beta activities throughout the WIPP underground. The average background gamma dose rate in the WIPP underground is 8.27 x 10(-9) +/- 1.65 x 10(-9) Gy/h while the gamma dose rate on the WIPP surface is 3.46 x 10(-8) +/- 1.65 x 10(-9) Gy/h. The overall surface average alpha activity in the underground is 8.52 x 10(-5) +/- 1.22 x 10(-4) Bq/cm2 (at 1sigma level) with the minimum detectable activity (MDA) of 4.81 x 10(-4) Bq/cm2. The overall surface average beta activity is 8.25 x 10(-4) +/- 8.17 x 10(-4) Bq/cm2 (at 1sigma level) with the MDA of 3.19 x 10(-3) Bq/cm2. This baseline standard will be beneficial to the overall WIPP operational facility, ensuring the worker safety and adding to public confidence in the operation of the WIPP.     

Synthetic models for the zinc sites in the methionine synthases

The syntheses and molecular structures of a series of tetrahedral zinc complexes designed to model the active sites in Escherichia coli methionine synthases are reported. [PhTttBu]ZnBr (PhTttBu = phenyltris((tert-butylthio)-methyl)borate) was prepared and characterized crystallographically to provide entry into [S3]ZnX complexes. Metathesis with KSPh yielded the phenylthiolato complex, [PhTttBu]Zn(SPh), which represents a structural mimic of the homocysteine ligated form of the enzyme. Alternatively, [S2N]ZnX (X = Br, CH3, SPh) species were prepared using the new mixed-donor ligands, [Ph(pz)BttBu] (phenyl(pyrazolyl)bis((tert-butylthio)methyl)borate) and [Ph(pztBu)BttBu] (phenyl(3-tert-butylpyrazolyl)bis((tert- butylthio)methyl)borate). Protonolysis of [Ph(pztBu)-BttBu]Zn(CH3) by PhSH in toluene yielded [Ph(pztBu)BttBu]Zn(SPh), a synthetic analogue of the homocysteine ligated form of cobalamin-independent methionine synthase (Met E). The average Zn-S bond distance in [Ph-(pztBu)BttBu]Zn(SPh) of 2.37 A compares well with the EXAFS-derived distance of 2.31 A found in the homocysteine-bound form of Met E.     

Highly stereoselective ring-opening addition of terminal acetylenes to bicyclic olefins catalyzed by nickel complexes

[reaction: see text] Treatment of 7-oxa- and 7-azabenzonorbornadienes with terminal acetylenes in the presence of Ni(dppe)Cl2, ZnCl2, and Zn powder in toluene at 90 degrees C afforded the corresponding cis-2-alkynyl-1,2-dihydronaphthalene derivatives in moderate to excellent yields with remarkably high stereoselectivity.     

Aromatic polybenzoxazoles containing ether–sulfone linkages

A series of poly(o‐hydroxy amide)s having both ether and sulfone linkages in the main chain were synthesized via the low‐temperature solution polycondensation of 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoyl chloride and 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoyl chloride with three bis(o‐aminophenol)s including 4,4′‐diamino‐3,3′‐dihydroxybiphenyl, 3,3′‐diamino‐4,4′‐dihydroxybiphenyl, and 2,2‐bis(3‐diamino‐4‐hydroxyphenyl)hexafluoropropane. Subsequent thermal cyclodehydration of the poly(o‐hydroxy amide)s afforded polyethersulfone benzoxazoles. Most of the poly(o‐hydroxy amide)s were soluble in polar organic solvents such as N‐methyl‐2‐pyrrolidone; however, the polybenzoxazoles without the hexafluoroisopropylidene group were organic‐insoluble. The polybenzoxazoles exhibited glass‐transition temperatures (T_g) in the range of 219–282 °C by DSC and softening temperatures (T_s) of 242–320 °C by thermomechanical analysis. Thermogravimetric analyses indicated that most polybenzoxazoles were stable up to 450 °C in air or nitrogen. The 10% weight loss temperatures were recorded in the ranges of 474–593 °C in air and 478–643 °C in nitrogen. The methyl‐substituted polybenzoxazoles had higher T_g's but lower T_s's and initial decomposition temperatures compared with the corresponding unsubstituted polybenzoxazoles. For a comparative purpose, the synthesis and characterization of a series of sulfonyl polybenzoxazoles without the ether group that derived from 4,4′‐sulfonyldibenzoyl chloride and bis(o‐aminophenol)s were also reported. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2262–2270, 2001     

Fabrication of Biomimetic Super‐Amphiphobic Surfaces Through Plasma Modification of Benzoxazine Films

Summary: In this study, a method for producing super‐amphiphobic surfaces through plasma modification of benzoxazine films is presented. Microroughening and fluorination of the benzoxazine films occurs during the plasma treatment process and a rugged surface with a micro/nano binary structure is formed. The combined effect of low surface energy and substrate roughness results in high advancing contact angles (157° for water, 152° for diiodomethane) and low contact angle hysteresis.

SEM image of a cross‐linked polybenzoxazine film treated with Ar plasma (7 min) heated to 200 °C (1 h) and treated with CF₄ plasma for 30 s.     

Synthesis of 3,3‐Dimethylglutamic Acid Derivatives as DPP‐IV Inhibitors and Evaluation of Their Chemical Stability

A novel five‐step synthesis of Boc‐3,3‐dimethylglutamic acid α‐ethyl ester 11 is reported. All the steps are high yielding and simple to carry out. By use of the 3,3‐dimethylglutamic acid building block, we successfully discovered a novel class of DPP‐IV inhibitors, Glu‐Pro‐Nitrile dipeptide mimics 2 , with high potency (IC₅₀ < 40 nM). The consequence of 3,3‐dimethyl substituent on the rate of intramolecular cyclization between N‐terminal amine and 5‐position amide bond in different buffer solutions was also evaluated.     

Laminar natural convection over a slender vertical frustum of a cone

The problem of laminar, natural convection flow over a slender frustum of a cone is treated in this paper. The governing differential equations are solved by a combination of quasi-linearization and finite-difference methods. Numerical solutions are obtained for Pr=0.7 and for a range of values of the transverse curvature parameter. It is shown that the effect of transverse curvature is of great significance in such flows.

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Laminare natürliche Konvektion an einem dünnen, senkrechten Kegelstumpf

Zusammenfassung In diesem Bericht ist das Problem der laminaren natürlichen Konvektionsströmung an einem dünnen Kegelstumpf behandelt. Die maßgebliche Differentialgleichung ist durch eine Verbindung von Quasilinearisation und Differenzenverfahren gelöst. Eine numerische Lösung für Pr=0.7 wird für verschiedene Werte eines Krümmungsparameters angegeben. Es ist gezeigt, daß in solchen Strömungen dieser Krümmungsparameter eine große Bedeutung besitzt.

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Nomenclature f dependent variable, defined in Eq. (7) - g dependent variable, defined in Eq. (7) - g_e gravitational acceleration - h heat transfer coefficient, or -grid - k heat conductivity, or -grid - L characteristic length - Nu Nusselt number - Pr Prandtl number - r radial distance from the axis of the cone - R transverse curvature effect ratio, defined in Eq. (23) - Re Reynold number - T temperature - u, v velocity components in the x- and y-directions, respectively - x, y rectangular coordinates Greek letters dimensionless temperature, definedinEq. (4) - bulk modulus - cone angle - dynamic viscosity - stream function - , independent variable, defined in (7) - transverse curvature parameter     

Influences of material source,wafer process and location on silicon die fracture strength

Experimental Techniques -     

Laminar film condensation on a horizontal disk

Heat and Mass Transfer - The problem of two-dimensional, steady film condensation on a finite-size, isothermal horizontal disk is studied for the case in which a cold plate faces upwards. The...