Red blood cell ghosts and intact red blood cells as complementary models in photodynamic cell research

Recent research on erythrocytes as model cells for photodynamic therapy showed differing behaviour of certain photosensitisers in erythrocytes compared to other cells. Differences of dye accumulation in the cell membrane were proposed to be the reason for the distinct photodynamic effects. Using pheophorbide a as an example, the combination of erythrocyte ghosts as models to follow the dye accumulation in the cell membrane and intact erythrocytes as model cells to show the photodynamic damage is provided. Evidence for the correctness of the combination of erythrocyte ghosts and intact erythrocytes as a functioning model system in photodynamic cell research is provided using the confocal laser scanning microscopy on intact, pheophorbide a loaded erythrocytes.     

Fullerenols revisited as stable radical anions

The first exhaustive purification and characterization of the much-studied "fullerenols", prepared by reaction of C(60) in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammonium hydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simply polyhydroxylated C(60) but rather is a structurally and electronically complex C(60) radical anion with a molecular formula of Na(+)(n)[C(60)O(x)(OH)(y)](n)(-) (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical, preparations. Surprisingly, Na(+)-fullerenol is paramagnetic, exhibiting mu(B) values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R(1) proton relaxivities of 0.55-0.77 mM(-1)s(-1) at 20 MHz and 40 degrees C, values both slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2D nutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na(+)-fullerenol is mainly S = 1/2 with a minor, but significant, component of S = 1. Thus, this is the first report to characterize these widely studied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na(+)-fullerenol radical is likely due to a highly derivatized C(60) surface that protects a cyclopentadienyl radical center on the fullerene.     

A new general-purpose isothermal microcalorimeter for use at temperatures up to 200 °C

The design and some properties of a new general-purpose isothermal microcalorimeter are reported. The instrument is a twin thermopile heat conduction calorimeter, which is designed for use up to 200 °C. The calorimetric units and surrounding heat sink are suspended inside a hollow aluminium construction, which is thermostated. Above that unit a second thermostated block is positioned and the whole assembly is suspended inside a Dewar vessel. When the instrument is used at room temperature and below, the thermostated units are cooled by use of an insertion Peltier effect cooler. The instrument can be used with a wide range of different reaction vessels (diameter 14 mm). Baseline experiments have been conducted in the temperature range 15-200 °C. Typical values obtained during 10 h periods at 200 °C are ±3 and ±10 nW for the baseline drift and baseline fluctuations, respectively. The heat detection limit, determined by release of electrical energy, is about 2 μJ. Preliminary stability measurements have been conducted at 100 °C on samples of stabilised and non-stabilised polyamide film.     

"Dimers" and "trimers" of tetrahydroindenes and hexahydroazulenes, respectively generated from [2-(1-cycloalkenyl)ethynyl]carbene complexes (M = W, Cr) by cascade cyclization/cycloaddition reactions

A cascade of cyclization/cycloaddition reactions was triggered by addition of protic oxygen nucleophiles ROH 2 (RO = CH3CO2, PhCO2, PhO) to [2-(1-cyclohexenyl)ethynyl]carbene complexes 1b and 1c (M=W, Cr, respectively), affording highly strained "dimers" 11/11' and "trimers" 12 of the carbene ligand. The first reaction step involved the formation of 1-metalla1,3,5-hexatrienes 7, which readily gave tetrahydroindenes 8 by pi cyclization and extrusion of the metal unit. "Dimers" 11/11' were generated from tetrahydroindenes 8 by a highly exo selective [4+2] cycloaddition of compounds 1b and 1c to afford 1-metalla-1,3,5-hexatriene intermediates 9, and a spontaneous pi cyclization of the latter compounds involving the disengagement of the metal unit. Propenylidene cyclohexenes 13/13' were formed in "ene"-type side reactions to the pi cyclization of 1-metalla-1,3,5-hexatrienes 7, by loss of the metal unit. "Dimers" 11 were transformed into "trimers" 12 by a [4+2] cycloaddition and subsequent pi-cyclization of the resulting 1-metalla-1,3,5-hexatriene system. The course of the reaction was elucidated by means of model reactions with (2-phenylethynyl)carbene complex 14, in which 1-metalla-1,3,5-hexatriene intermediates 16 and 17 were isolated and characterized. Alkynyl benzene derivatives 19 were obtained by an unprecedented ring-expansion of a cyclopentadiene unit of "dimers" 11a and 11c, involving the insertion of a carbene carbon atom of compound 14 into a C=C bond. A reaction cascade leading to "dimers" 24/24' could also be triggered by treatment of compounds 2 with [2-(1-cycloheptenyl)ethynyl]carbene tungsten complex 1d.     

Optimizing pig marketing decisions under price fluctuations

In the manufacturing of fattening pigs, pig marketing refers to a sequence of culling decisions until the production unit is empty. The profit of a production unit is highly dependent on the price of pork, the cost of feeding and the cost of buying piglets. Price fluctuations in the market consequently influence the profit, and the optimal marketing decisions may change under different price conditions. Most studies have considered pig marketing under constant price conditions. However, because price fluctuations have an influence on profit and optimal marketing decisions it is relevant to consider pig marketing under price fluctuations. In this paper we formulate a hierarchical Markov decision process with two levels which model sequential marketing decisions under price fluctuations in a pig pen. The state of the system is based on information about pork, piglet and feed prices. Moreover, the information is updated using a Bayesian approach and embedded into the hierarchical Markov decision process. The optimal policy is analyzed under different patterns of price fluctuations. We also assess the value of including price information into the model.

     

The determination of oxygen in sulphur-containing organic compounds

Summary The reactions of anhydroiodic acid with CS₂, H₂S, and COS have been quantitatively investigated at 120° C and 170° C. The iodine formed was titrated and the gaseous reaction products determined by gas chromatography. At 170° C, CS₂ and COS are quantitatively oxidized to CO₂ and SO₂, and H₂S is oxidized to water and partially to SO₂ while a stoicheiometric fraction of the sulphur is obtained as elemental S. At 120° C the reactions are the same although in no case is the oxidation completely quantitative at this temperature.

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Zusammenfassung Die Reaktionen der Anhydrojodsäure mit CS₂, H₂S und COS wurden bei 120 und 170° C quantitativ untersucht. Das freigesetzte Jod wurde titriert und die gasförmigen Reaktionsprodukte gaschromatographisch bestimmt. Bei 170° C werden CS₂ und COS quantitativ zu CO₂ und SO₂ oxydiert, H₂S zu Wasser und teilweise zu SO₂, während ein stöhiometrischer Anteil des Schwefels in elementare Form übergeht. Bei 120° C laufen die gleichen Reaktionen ab, aber keinesfalls quantitativ.

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Résumé On a fait l'étude quantitative des réactions de l'acide anhydroiodique avec CS₂, H₃S et COS à 120° C et 170° C. On a titré l'iode formé et réalisé le dosage des produits gazeux de la réaction par Chromatographie en phase gazeuse. A 170° C, CS₂ et COS sont oxydés quantitativement en CO₂ et SO₂; H₂S est oxydé en eau et partiellement en SO₂ et il se forme une fraction stoechiométrique de soufre à l'état élémentaire. A 120° C, les réactions sont les mêmes bien que l'oxydation ne soit jamais quantitative à cette température.

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This work was supported by grants from the Statens Tekniska Forskningsrad (Swedish Technical Research Council).     

Boundary and Lens Rigidity of Lorentzian Surfaces

Let be a Lorentzian metric on the plane that agrees with the standard metric outside a compact set and so that there are no conjugate points along any time-like geodesic of . Then and are isometric. Further, if and are two dimensional compact time oriented Lorentzian manifolds with space--like boundaries and so that all time-like geodesics of maximize the distances between their points and and are ``boundary isometric', then there is a conformal diffeomorphism between and and they have the same areas. Similar results hold in higher dimensions under an extra assumption on the volumes of the manifolds.

     

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis Frequently used abbreviations are defined at the end of the article

In the second half of the twentieth century much effort was invested in the preparation of highly reactive polar organometallic reagents. The high reactivity of these reagents precluded the presence of many functional groups and often good chemoselectivities and stereoselectivities could only by achieved by transmetalation reactions. The synthesis of increasingly complex target molecules and the desire to avoid tedious protection-deprotection steps has led inevitably to the use of functionalized organometallic reagents in retrosynthesis. In the last fifteen years, the generation of organic derivatives of numerous metals and metalloids (Li, Mg, B, Zn, Sn) was investigated. In this review the most important preparations and applications of organometallic reagents in organic synthesis will be covered, with particular emphasis on organozinc reagents.     

Protolytic surface reactions of a fluorapatite-maghemite mixture in aqueous suspension

Synthetically prepared maghemite and fluorapatite, characterized with BET, SEM, XRD, FT-IR, and FT-Raman, are used to investigate the protolytic properties and surface characteristics in a mixed system of maghemite and fluorapatite by means of potentiometric titrations and surface complex modeling. Titrations were performed in the pH range of 7.3-10.5 at 25 +/- 0.2 degrees C in ionic media of 0.10 mol dm(-3) NaNO3 with 0.0100 mol dm(-3) HNO3 and 0.0100 mol dm(-3) NaOH used as titrants. The constant capacitance model (CCM) was applied to interpret the titration data. Two models with different surface equilibria were tested. In the first model, the mixed system was treated as a one-component system with a total surface area of 40.04 +/- 5.2 m2 g(-1) without any consideration to the subsystems. The surface equilibria, triple bond XOH + H+ <==> triple bond XOH2+, beta(s)(-11)(int) = 6.74 +/- 0.07; XOH <==> triple bond XO- + H+, beta(s)(-11)(int) = -7.75 +/- 0.07, were found to represent an accurate model for the system, and the specific capacitance was optimized to 2.0 F m(-2). The number of active surface sites N(s) was found to be 1.2 sites nm(-2). This model has, however, no relation to the subsystems of maghemite and fluorapatite. The second model is related to the subsystems and displays the surface equilibria, triple bond S2OH<==> triple bond S2O- + H+, beta(s)(-101)(int) = -9.12 +/- 0.01; triple bond FeOH + H+<==> triple bond FeOH2+, lg beta(s)(-11)(int) = 6.80 +/- 0.01; triple bond FeOH<==>FeO- + H+, beta(s)(-11)(int) = -7.77 +/- 0.01, where S2OH is related to fluorapatite and FeOH is representing maghemite. Fluorapatite corresponds to the dominating active surface in the system. The specific capacitance was optimized to 18 F m(-2). The N(s) values were found to be 2.27 sites nm(-2) for fluorapatite and 0.80 sites nm(-2) for maghemite. The N(s) values together with evidence from the FT-Raman and SEM investigations reveal that interactions between maghemite and fluorapatite surfaces occur during the titration. The acid-base properties and surface characteristics of the subsystems maghemite-H+ and fluorapatite-OH- using the CCM have been published earlier.