Application of Mathematical Programming to the Plywood Design and Manufacturing Problem

Plywood manufacture includes two fundamental stages. The first is to peel or separate logs into veneer sheets of different thicknesses. The second is to assemble veneer sheets into finished plywood products. At the first stage a decision must be made as to the number of different veneer thicknesses to be peeled and what these thicknesses should be. At the second stage, choices must be made as to how these veneers will be assembled into final products to meet certain constraints while minimizing wood loss. These decisions present a fundamental management dilemma. Costs of peeling, drying, storage, handling, etc. can be reduced by decreasing the number of veneer thicknesses peeled. However, a reduced set of thickness options may make it infeasible to produce the variety of products demanded by the market or increase wood loss by requiring less efficient selection of thicknesses for assembly. In this paper the joint problem of veneer choice and plywood construction is formulated as a nonlinear integer programming problem. A relatively simple optimal solution procedure is developed that exploits special problem structure. This procedure is examined on data from a British Columbia plywood mill. Restricted to the existing set of veneer thicknesses and plywood designs used by that mill, the procedure generated a solution that reduced wood loss by 79 percent, thereby increasing net revenue by 6.86 percent. Additional experiments were performed that examined the consequences of changing the number of veneer thicknesses used. Extensions are discussed that permit the consideration of more than one wood species.

CSSI-PRO: a method for secondary structure type editing, assignment and estimation in proteins using linear combination of backbone chemical shifts

Estimation of secondary structure in polypeptides is important for studying their structure, folding and dynamics. In NMR spectroscopy, such information is generally obtained after sequence specific resonance assignments are completed. We present here a new methodology for assignment of secondary structure type to spin systems in proteins directly from NMR spectra, without prior knowledge of resonance assignments. The methodology, named Combination of Shifts for Secondary Structure Identification in Proteins (CSSI-PRO), involves detection of specific linear combination of backbone H-1(alpha) and C-13' chemical shifts in a two-dimensional (2D) NMR experiment based on G-matrix Fourier transform (GFT) NMR spectroscopy. Such linear combinations of shifts facilitate editing of residues belonging to alpha-helical/beta-strand regions into distinct spectral regions nearly independent of the amino acid type, thereby allowing the estimation of overall secondary structure content of the protein. Comparison of the predicted secondary structure content with those estimated based on their respective 3D structures and/or the method of Chemical Shift Index for 237 proteins gives a correlation of more than 90% and an overall rmsd of 7.0%, which is comparable to other biophysical techniques used for structural characterization of proteins. Taken together, this methodology has a wide range of applications in NMR spectroscopy such as rapid protein structure determination, monitoring conformational changes in protein-folding/ligand-binding studies and automated resonance assignment.

The Structure Of 2',3'-O-Isopropylideneuridine

C12HI6N206 is orthorhombic, P2x2121, with a = 19.890 (5), b = 12.789 (2), c = 5.236 (1) A, Z = 4, U = 1331.9/~ 3, F(000) = 600. Mo Ka (/~ = 0.123 mm -1) intensities for 940 unique reflections up to sin 0/2 = 0.538/k -1 were collected on a CAD-4 diffractometer. Final R = 0.034. The glycosidic torsion angle 2~CN is 3"4 °, significantly smaller than that (56.5 °) in 2',3'- -methoxymethyleneuridine (MMU). The ribose moiety has a C(3')-exo-C(4')-endo twist conformation, in contrast to the C(2')-endo conformation in MMU. However, the maximum amplitudes of pucker for the ribose and dioxolane rings are very nearly the same for the two structures. The conformation about C(4')-C(5') is gauche-gauche (~0oo = -68-4, Ooc = 51.3°).

Heat balance analysis of single stage Gifford-McMahon cycle cryorefrigerator

A heat balance analysis of single stage Gifford-McMahon cycle cryorefrigerator is presented. Ideal refrigeration, actual refrigeration, net refrigeration and the various losses are tabulated. It is observed that pressure-volume losses account for a major fraction of the total losses.

Acyclic peptides as conformational models Crystal structure of Boc-Aib-Leu-Pro-NHMe± 2H2O

The tripeptide Boc-Aib-Leu-Pro-NHMe crystallizes in the orthorhombic space group P212121 with a = 9.542, b = 15.200, c = 18.256 Å and Z = 4. Each peptide is associated wth two water molecules in the asymmetric unit of the crystal. The structure has been solved by direct methods and refined to an R-value of 0.069. The peptide adopts a structure without any intramolecular hydrogen bond. The three residues occupy distinctly different regions of the Ramachandran map: Aib in the left-handed 310-helical region (± = 67°, ± = 23°), Leu in the β-sheet region (± = - 133°, ± = 142°) and Pro in the poly (Pro) II region (± = - 69°, ± = 151°). An interesting observation is that each water molecule participates in four hydrogen bonds with distorted tetrahedral coordination about the oxygen atom.

Computer-aided analysis of the structure of kinematic chains

Using the link-link incidence matrix to represent a simple-jointed kinematic chain algebraic procedures have been developed to determine its structural characteristics such as the type of freedom of the chain, the number of distinct mechanisms and driving mechanisms that can be derived from the chain. A computer program incorporating these graph theory based procedures has been applied successfully for the structural analysis of several typical chains.

Dynamic structure factor across the liquid-solid interface: appearance of a delta-function elastic peak

We present a theoretical calculation of the dynamic structure factor, S(k, ω), at the liquid-solid interface for large values of the wavevector k. An analytic expression is derived which shows the evolution of the elastic peak as the solid surface is approached from the liquid side.

Study of effects of dopants on structure of vitreous semiconductors (GeSe3.5)100-xMx (M = Bi, Sb) using high pressure techniques

An investigation of the problem of controlled doping of amorphous chalcogenide semiconductors utilizing a Bridgman anvil high pressure technique, has been undertaken. Bulk amorphous semiconducting materials (GeSe3.5)100-x doped with M = Bi (x = 2, 4, 10) and M = Sb (x = 10) respectively are studied up to a pressure of 100 kbar down to liquid nitrogen temperature, with a view to observe the impurity induced modifications. Measurement of the electrical conductivity of the doped samples under quasi-hydrostatic pressure reveals that the pressure induced effects in lightly doped (2 at % Bi) and heavily doped (x = 4, 10) semiconductors are markedly different. The pressure effects in Sb-doped semiconductors are quite different from those in Bi-doped material.

Reinvestigation of the structure of Feist's acid 3-methylene-trans-1,2-cyclopropanedicarboxylic acid

C6H604, Mr = 142, triclinic, P[, a = 4.842(1), b = 7.607(1), c = 9.168 (3) A, ~ = 98.41(2), fl = 99.89(2), y = 77.74(1) ° , V = 320.9/k 3, Z = 2, Dm= 1.45 (flotation), D x = 1.470 g cm -3, p(Mo Ktt, 2 = 0.7107 A) = 0.63 cm -~, F(000) = 148. The structure was solved by direct methods and refined to an R value of 0.038 for 723 intensity measurements. The geometrical changes in the cyclopropane ring are discussed in the light of substituent effects. In the crystal structure the carboxylic groups are disordered.

Ultrafast Raman loss spectroscopy: a new approach to vibrational structure determination

The rapid data acquisition, natural fluorescence rejection and experimental ease are the advantages of the ultra-fast Raman loss scattering (URLS) which makes it a unique and valuable molecular structure-determining technique. URLS is an analogue of stimulated Raman scattering (SRS) but far more sensitive than SRS. It involves the interaction of two laser sources, viz. a picosecond (ps) pulse and white light, with the sample leading to the generation of loss signal on the higher energy (blue) side with respect to the wavelength of the ps pulse, unlike the gain signal observed on the red side in SRS. These loss signals are at least 1.5 times more intense than the SRS signals. Also, the very prerequisite of the experimental protocol for signal detection to be on the higher energy side by design eliminates the interference from fluorescence, which always appears on the red side. Unlike coherent anti-Stokes Raman scattering, URLS signals are not precluded by non-resonant background under resonance condition and also being a self-phase matched process, it is experimentally easier.

Structure of a new crystal form of 2- ([3-(trifluoromethyl)phenyl] amino)benzoic acid (flufenamic acid)

C14Ht0F3NO2, P2.Jc, a = 12.523 (4), b = 7.868(6), c = 12.874 (3)A, fl = 95.2 (2) ° , O,,, = 1.47 (4), D e = 1.47 Mg m -3, Z = 4. Final R = 0.074 for 2255 observed reflections. The carboxyl group and the phenyl ring bearing the carboxyl group are nearly coplanar whereas the two phenyl rings are inclined with respect to each other at 52.8 ° . The difference between the two polymorphs of flufenamic acid lies in the geometrical disposition of the [3-(trifluoromethyl)- phenyl]amino moiety with respect to the benzoic acid moiety. As in other fenamate structures, the carboxyl group and the imino N atom are connected through an intramolecular hydrogen bond; also, pairs of centrosymmetrically related molecules are connected through hydrogen bonds involving carboxyl groups.

Structural studies of analgesics and their interactions. VII. Stereoisomerism and disorder in the structure of oxyphenbutazone monohydrate

Oxyphenbutazone, C19H20N203, a metabolite and perhaps the active form of phenylbutazone, is a widely used non-narcotic analgesic and anti-inflammatory pyrazolidinedione derivative. The monohydrate of the compound crystallizes in the triclinic space group Pi with two molecules in a unit cell of dimensions a -- 9.491 (4), b = 10.261 (5), c = 11.036 (3)A and ¢~ = 72.2 (1), fl = 64.3 (1), 7 = 73.0 (1) °. The structure was solved by direct methods and refined to an R value of 0.107 for 1498 observed reflections. The butyl group in the molecule is disordered. The hydroxyl group occupies two sites with unequal occupancies. On account of the asymmetry at the two N atoms and one of the C atoms in the central five-membered ring, the molecule can exist in eight isomeric states, of which four are sterically unfavourable. The disorder in the position of the hydroxyl group can be readily explained on the basis of the existence, with unequal abundances, of all four sterically favourable isomers.The bond lengths and angles in the molecule are similar to those in phenylbutazone. The crystal structure is stabilized by van der Waals interactions, and O-H... O hydrogen bonds involving the carbonyl and the hydroxyl groups as well as a water molecule.

A neutron diffraction investigation of the structure of PBO-PBCL2 glasses

Neutron diffraction techniques have been employed to investigate the structure of PbO-PbCl2 glasses as a function of composition in the nominal range PbO.PbCl2 to 9PbO.PbCl2. It is concluded that, whereas the first Pb-O distance is well defined, the distribution of Pb-Cl distances is much broader, in agreement with a previous EXAFS study.