Operating and maintenance policies of a service system

In this paper we analyze the effects of various nonoptimal operating maintenance policies on the level of service provided by a system of $\text{N}$ units, $\text{M}$ of which need to be in continuous operation. It is shown that policies that utilize the units' characteristics are more efficient than first in first out (FIFO) or random policies. A comparison between these policies and an optimal one is made with respect to small systems. Furthermore, the problem of assigning priorities in such systems is discussed.     

Nachweis der Behandlung von Hühnerbrust mit ionisierenden Strahlen und Abschätzung der Bestrahlungsdosis mit Hilfe der Headspace-Gaschromatographie und diskriminanzanalytischer Auswertung

Chicken breast was irradiated with doses of 3, 5, and 7 kGy. Headspace gas chromatographical analysis demonstrated the tendency that the amounts of volatile compounds (mainly pentanal, hexanal and heptanal) are higher in irradiated samples in comparison with non irradiated. Statistical evaluation of the gas chromatograms by discriminant analysis enabled the detection of irradiation. Unknown samples could be classified in the groups ?unirradiated“ or ?irradiated in most cases.     

Effect of ammonia content on the stability of the cellulose cuprammonium complex in spinning solution

Conclusions Using a spectrophotometric method of investigation, it has been shown that in cuprammonium spinning solutions the complex compounds of copper, ammonia, and cellulose contain principally the tetraamine ion Cu(NH₃) ₄ ²⁺ .By using the molar value of the NH₃/Cu ratio in CCAC, one can calculate the free ammonia content of the spinning solution and of the precipitation bath.Translated from Khimicheskie Volokna, No. 2, pp. 30–32, March–April, 1987.     

Die Wärmeausdehnung austenitischer Mangan- und Mangan-Chrom-Stähle

Dilatometrische Bestimmung des linearen Wärmeausdehnungskoeffizienten an fünf Manganstählen sowie sechs Mangan-Chrom-Stählen zwischen — 196 und 500°C. Einfluß der magnetischen Ordnung auf das Ausdehnungsverhalten. Ausdehnungsverhalten verschiedener Schmelzen bei vorgegebener Stahlqualität.     

Lower time bounds for integer programming with two variables

In this paper an elementary version of the integer programming problem is considered, namely that of deciding whether a given triangle in the plane contains a point with integer coordinates. We prove two lower bounds for the number of operations necessary to solve this problem: (i) Ω(p) steps are necessary if operations from {+, -,%,, ?} are admissible, (ii) Ω(log p) steps are necessary if operations from {+, -, ?·?, ?} are admissible. Here, p denotes the binary length of the input and ?·? denotes the floor function. New techniques are necessary for relating the bounds to the length of the input—known methods only yield uniform bounds assuming all real inputs to be allowed—and for handling the floor function which prevents us from applying the well-known algebraic arguments.The best known algorithm is due to H.W. Lenstra, Jr. (preprint) and needs O(p) steps over {+, -, 1, %, ?·?, ?} (P. van Emde Boas, 1984).     

Stability of fatty acyl-coenzyme a thioester ligands of hepatocyte nuclear factor-4α and peroxisome proliferator-activated receptor-α

Although long-chain fatty acyl-coenzyme A (LCFA-CoA) thioesters are specific high-affinity ligands for hepatocyte nuclear factor-4α (HNF-4α) and peroxisome proliferator-activated receptor-α (PPARα), X-ray crystals of the respective purified recombinant ligand-binding domains (LBD) do not contain LCFA-CoA, but instead exhibit bound LCFA or have lost all ligands during the purification process, respectively. As shown herein: (i) The acyl chain composition of LCFA bound to recombinant HNF-4α reflected that of the bacterial LCFA-CoA pool, rather than the bacterial LCFA pool. (ii) Bacteria used to produce the respective HNF-4α and PPARα contained nearly 100-fold less LCFA-CoA than LCFA. (iii) Under conditions used to crystallize LBD (at least 3 wk at room temperature in aqueous buffer), 16∶1-CoA was very unstable in buffer alone. (iv) In the presence of the respective nuclear receptor (i.e., HNF-4α and PPARα), LBD 70–75% of 16∶1-CoA was degraded after 1 d at room temperature in the crystallization buffer, whereas as much as 94–97% of 16∶1-CoA was degraded by 3 wk. (v) Cytoplasmic LCFA-CoA binding proteins such as acyl-CoA binding protein, sterol carrier protein-2, and liver-FA binding protein slowed the process of 16∶1-CoA degradation proportional to their respective affinities for this ligand. Taken together, these data for the first time indicated that the absence of LCFA-CoA in the crystallized HNF-4α and PPARα was due to the paucity of LCFA-CoA in bacteria as well as to the instability of LCFA-CoA in aqueous buffers and the conditions used for LBD crystallization. Furthermore, instead of protecting bound LCFA-CoA from autohydrolysis like several cytoplasmic LCFA-CoA binding proteins, these nuclear receptors facilitated LCFA-CoA degradation.