Models Needed to Assist in the Development of a National Fiber Supply Strategy for the 21st Century: Report of a Workshop

This discussion paper reports on a Workshop on Wood Fiber Supply Modeling held October 3-4, 1996 in Washington, DC. The purpose of this discussion paper is to provide an overview of some of the modeling work being done related to timber supply modeling and some of the issues related to the more useful application of wood fiber supply and projections models. This paper includes brief presentations of three commonly used long-term timber projections and forecasting models: the Timber Assessment Market Model (TAMM) of the Forest Service; the Cintrafor Global Trade Model (CGTM) of the University of Washington; and the Timber Supply Model (TSM) of Resources for the Future. Also, issues related to the useful of the models are addressed as well as a discussion of some applications of other timber or fiber projection models. The usefulness of the models are addressed from both a technical perspective and also from the perspective of their usefulness to various model users.

Role of Pure Technetium Chemistry: Are There Still Links to Applications in Imaging?

The discovery and development of new 99mTc-based radiopharmaceuticals or labeled drugs in general is based on innovative, pure chemistry and subsequent, application-targeted research. This was the case for all currently clinically applied imaging agents. Most of them were market-introduced some 20 years ago, and the few more recent ones are based on even older chemistry, albeit technetium chemistry has made substantial progress over the last 20 years. This progress though is not mirrored by new molecular imaging agents and is even accompanied by a steady decrease in the number of groups active in pure and applied technetium chemistry, a contrast to the trends in most other fields in which d-elements play a central role. The decrease in research with technetium has been partly counterbalanced by a strong increase of research activities with homologous, cold rhenium compounds for therapy, disclosing in the future eventually a quite unique opportunity for theranostics. This Viewpoint analyzes the pathways that led to radiopharmaceuticals in the past and their underlying fundamental contributions. It attempts to tackle the question of why new chemistry still does not lead to new imaging agents, i.e., the question of whether pure technetium chemistry is still needed at all

Magnetically-induced ferroelectricity in the (ND4)2[FeCl5(D2O)] molecular compound

The number of magnetoelectric multiferroic materials reported to date is scarce, as magnetic structures that break inversion symmetry and induce an improper ferroelectric polarization typically arise through subtle competition between different magnetic interactions. The (NH4)2[FeCl5(H2O)] compound is a rare case where such improper ferroelectricity has been observed in a molecular material. We have used single crystal and powder neutron diffraction to obtain detailed solutions for the crystal and magnetic structures of (NH4)2[FeCl5(H2O)], from which we determined the mechanism of multiferroicity. From the crystal structure analysis, we observed an order-disorder phase transition related to the ordering of the ammonium counterion. We have determined the magnetic structure below TN, at 2K and zero magnetic field, which corresponds to a cycloidal spin arrangement with magnetic moments contained in the ac-plane, propagating parallel to the c-axis. The observed ferroelectricity can be explained, from the obtained magnetic structure, via the inverse Dzyaloshinskii-Moriya mechanism

Multifunctional Cyclopentadienes as a Scaffold for Combinatorial Bioorganometallics in [(η5-C5H2R1R2R3)M(CO)3] (M=Re, 99mTc) Piano-Stool Complexes

Multifunctional cyclopentadiene (Cp) ligands and their rhenium and 99mTc complexes were prepared by a versatile synthetic route. The properties of these Cp ligands can be tuned on demand, either during their synthesis (variation of R1) or through post-synthetic functionalization with two equal or different vectors (V1 and V2). Variation of these groups enables a combinatorial approach in the synthesis of bioorganometallic complexes. This is demonstrated by the preparation of Cp ligands containing both electron-donating and electron-withdrawing groups at the R1 position and their subsequent homo- or heterofunctionalization with biovector models (benzylamine and phenylalanine) under standard amide bond-formation conditions. All ligands can be coordinated to the fac-[Re(CO)3]+ and fac-[99mTc(CO)3]+ cores to give tetrafunctional complexes in straightforward and functional-group-tolerant procedures. The 99mTc complexes were prepared in one step, in 30 min, and under aqueous conditions from generator-eluted [99mTcO4]-

The crystal structure of cis-diaqua-bis (N-butyl-N-(pyridin-2-yl)pyridin-2-amine-κ2N,N′)cobalt(II)] dichloride trihydrate, C28H44Cl2N6O5Co

C28H44Cl2N6O5Co, triclinic, P 1 ‾ (no. 2), a = 11.20(2) Å, b = 12.70(3) Å, c = 12.80(4) Å, α = 100.30(12)°, β = 103.18(9)°, γ = 106.77(6)°, V = 1638(8) Å3, Z = 2, R gt (F) = 0.0372, wR ref (F2) = 0.0890, T = 100 K. CCDC no.: 2086847 The molecular structure is shown in figure (the chloride counter anions and uncoordinated water molecules are omitted for clarity). Table 1 contains crystallographic data and Table 2 contains the list of the atoms including atomic coordinates and displacement parameters

Medición de la capacidad de los procesos productivos a través del peso en la fabricaciónde mortero, en la empresa PECASA, Managua comprendido entre el periodo Octubre-Diciembre 2014

El objetivo principal de esta investigación es realizar un análisis de la fabricación del mortero, a través del peso del producto terminado en dos de los cuatro tipos de materiales producidos en la empresa Pegamento Centro Americano S.A, PECASA, con el propósito de mejorar la producción. En la actualidad el proceso de producción se realiza en base a decisiones tomadas por el personal que labora en la empresa, las cuales se basan por conocimientos propios de los trabajadores que poseen mayor experiencia, lo cual induce a una variabilidad en el peso de la bolsa del material y problemas críticos en las diferentes operaciones del proceso de producción. Se analizó la línea de producción perteneciente a la actividad de llenado de la bolsa en la empresa y la toma de tiempo de llenado que va ligado con el peso de cada una de ellas, a través de un muestreo para evaluar el comportamiento del peso, la muestra se seleccionó por medio de los días que se producían dichos materiales dado a que esta empresa fabrica en su mayoría solo por pedido. Los métodos empleados para describir el proceso de producción, material, evaluar el comportamiento del peso y determinar los puntos vulnerables en el proceso de fabricación son herramientas estadísticas de control y la observación directa. Referente a las conclusiones del trabajo se observó que se necesita establecer controles en el procedimiento del llenado de la bolsa para reducir la variabilidad del peso, dado a que el peso se encuentra fuera de control a través del análisis de capacidad constatamos que el peso no es capaz, es decir que no cumplen con las especificaciones establecidas por el fabricante. Así mismo se recomienda establecer un control rígido en el proceso de llenado de la bolsa, como también establecer un programa de mantenimiento continuo de las maquinas involucradas en todo el proceso de producción y aplicaciones por medio de controles estadísticos de calidad para evaluar el estado del proces

Application of technetium and rhenium carbonyl chemistry to nuclear medicine. Preparation of [NEt4]2[TcCl3(CO)3] from [NBu4][TcO4] and structure of [NEt4][Tc2(μ-Cl)3(CO)6]; structures of the model complexes [NEt4][Re2(μ-OEt)2(μ-OAc)(CO)6] and [ReBr({-CH2S(CH2)2Cl}2)(CO)3]

A detailed investigation of the one-pot synthesis of [NEt4]2[MX3(CO)3] [M=Tc (1a) or Re (1b); X= Cl−, Br−] is presented. The intermediates [NEt4][Tc2-(μ-Cl)3(CO)6] (2a), [NBu4][Tc3(μ3-H)(μ-H)3(CO)9] (3) and [Tc3(μ-H)3(CO)12] (4) have been isolated and characterized. The X-ray structure of (2a) is described. Complex (2a) crystallizes in the monoclinic space group P21/c with a=19.491(6), b=18.323(2) and c=17.497(9)AÅ, and β=97.59(2)°. Quantitative conversion of (2a), (3) and (4) into the aqua-ion [M(OH2)3(CO)3]+ [M=Tc (5a) or Re (5b)] is described. To evaluate an optimal and simple chelating group for the "fac-M(CO)3” moiety, the reaction with the bidentate thioether ligand Cl(CH2)2S(CH2)2S(CH2)2Cl (qyp) has been investigated and the structure of the neutral complex [ReBr(qyp)(CO)3] (6) is described. Complex (6) crystallizes in the monoclinic space group P21/c with a=15.935(6), b=2.788(4) and c= 7.955(10)AÅ, and β=98.57(1)°. To extend the knowledge about substitution chemistry of organometallic complexes in aqueous solution, the acetato ligand [OOCCH3]− has been reacted with (1b), resulting in the formation of the dinuclear, acetato-bridged complex [NEt4][Re2(μ-OH)2(μ-OAc)(CO)6], which converted into [Re2(μ-OEt)2(μ-OAc)(CO)6]− (7) after recrystallization from EtOH. The X-ray structure of (7) has been determined. Complex (7) crystallizes in the monoclinic space group P21/c with a=16.288(3), b=12.4272(10) and c=13.620(3)AÅ, and β=76.63(1)°. For a future application of the small "fac-M(CO)3” moiety, it seems thus advantageous to combine these two ligand groups in one simple chelating functio

One Electron Changes Everything: Synthesis, Characterization, and Reactivity Studies of [Re(NCCH3)6]3+

Oxidation of [Re(NCCH3)6]2+ with the thianthrene radical cation results in the formation of [Re(NCCH3)6]3+, one of the very rare cases of a fully solvated +3 complex. It was fully characterized by spectroscopy and X-ray structure analysis. In contrast to its reduced analogue, [Re(NCCH3)6]3+ exhibits a much faster CH3CN exchange. Hence, substitution reactions proceed at 20 °C within minutes. Its potential as a versatile precursor for ReIII chemistry was examined with a series of substitution reactions. The more lipophilic analogue [Re(NCPh)6]3+ was synthesized by nitrile exchange in benzonitrile (NCPh). The Re(II) analogue of [Re(NCPh)6]3+, [Re(NCPh)6]2+, forms by AgI-mediated oxidation of in situ formed [Re(η6-C6H6)(NCPh3)3]+ in NCPh. The same synthetic strategy is feasible for the synthesis of [Re(NCCH3)6]2+ as well. [Re(NCCH3)6]3+ reacts with 1,4,7-trithiacyclononane (C6H12S3) to yield sevenfold-coordinated [Re(κ3-C6H12S3)2(NCCH3)]3+. The reaction of [Re(NCCH3)6]3+ with 1 equiv of (NBu4)X produces the ReIII monohalide complexes [ReX(NCCH3)5]2+ (X = Cl, Br, I). Mixed ReIII dihalides (trans-[ReXY(NCCH3)4]+) were obtained by treating [ReX(NCCH3)5]2+ with a second equivalent of (NBu4)Y (if X = Cl, Y = Br, I; if X = Br, Y = I). Because of this fast CH3CN exchange, [Re(NCCH3)6]3+ is a very suitable precursor for new ReIII complexes