Fractionation in radiation treatment planning

Radiotherapy treatment is often delivered in a fractionated manner over a period of time. Emerging delivery devices are able to determine the actual dose that has been delivered at each stage facilitating the use of adaptive treatment plans that compensate for errors in delivery. We formulate a model of the day-to-day planning problem as a stochastic program and exhibit the gains that can be achieved by incorporating uncertainty about errors during treatment into the planning process. Due to size and time restrictions, the model becomes intractable for realistic instances. We show how heuristics and neuro-dynamic programming can be used to approximate the stochastic solution, and derive results from our models for realistic time periods. These results allow us to generate practical rules of thumb that can be immediately implemented in current planning technologies.     

Addition of lithiated C-nucleophiles to 2,3-O-isopropylidene-D-erythronolactone: stereoselective formation of a furanose C-disaccharide

Addition of PhLi and lithiated dithianes to 2,3-O-isopropylidene-D-erythronolactone affords lactols, which are reduced with Et3SiH to the corresponding C-glycosides, the structures of two of which have been solved by X-ray diffraction. The use of a d-ribose-derived lithiated dithiane nucleophile in this chemistry allows for the convenient construction of a furanose C-disaccharide.     

Crystal structures of caesium and rubidium chlorochromates,CsCrO3Cl and RbCrO3Cl

The crystal structures of CsCrO₃Cl and RbCrO₃Cl have been determined from MoK₁diffractometer data and refined anisotropically toR = 0.029 andR = 0.033 respectively for 769 and 590 statistically significant reflections. CsCrO₃Cl, which has a structure of the BaSO₄ type, crystallizes in the orthorhombic space groupPnma, witha = 9.928,b = 6.043,c = 8.712 Å andZ = 4. RbCrO₃Cl is isostructural with KCrO₃C1 and NH₄CrO₃Cl and crystallizes in the monoclinic space groupP2₁/c witha = 7.857,b = 7.711,c = 8.055 Å, = 90.43 ° andZ = 4. The geometry of the approximately tetrahedral CrO₃Cl^– groups is very similar in both structures, and the Cr-Cl and average Cr-O bond distances, corrected for thermal vibration of the terminal atoms, are 2.197 and 1.612 Å in CsCrO₃Cl and 2.194 and 1.606 Å in RbCrO₃Cl. Caesium ions are in 12-fold coordination and rubidium ions in irregular 11-fold coordination to chlorine and oxygen.     

Crystal and molecular structure of a root inhibitor fromEucalyptus grandis, 4-ethyl-1-hydroxy-4,8,8,10,10-pentamethyl-7,9-dioxo-2,3-dioxabicyclo [4.4.0]decene-5

The crystal structure of C₁₅H₂₂O₅, a root inhibitor isolated from adult leaves ofEucalyptus grandis, has been determined by direct methods with Cuk diffractometer data and refined by full-matrix least-squares calculations toR = 0·046 for 1829 statistically significant reflexions. The compound, a racemate, crystallizes in the monoclinic space groupP2₁/c, with unit cell dimensionsa = 11·767,b = 12·063,c = 10·906 Å, = 103·2° andZ = 4. The molecular skeleton consists of a 2,3-dioxabicyclo[4.4.0]decene system with one hydroxyl, two carbonyl, one ethyl and five methyl side groups. The dihedral angle at the peroxide bond is 76·8° and the O-O bond distance is 1·480 Å. The molecules are linked in the c direction by hydrogen bonds between the hydroxyl group and one of the carbonyl oxygen atoms.The author is grateful to Professor W. D. Crow for suggesting the problem and for crystals ofG1, to Dr A. McL. Mathieson (Division of Chemical Physics, C.S.I.R.O.), in whose laboratory the data were collected, and Mr J. Fridrichsons for their advice and continued interest, to Dr W. A. Denne (Division of Chemical Physics, C.S.I.R.O.) and Mr B. J. Poppleton (Division of Forest Products, C.S.I.R.O.) for help and advice in the data collection and for the use of data reduction programs and to Dr D. A. Wright (Chemical Physics Group, Department of Supply) for several computer programs used in this work.     

Poly(cyclic imino ether)s Beyond 2‐Substituted‐2‐oxazolines

2‐Oxazolines (2‐OZO) are 5‐membered cyclic imino ethers whose cationic ring‐opening polymerization (CROP) mechanism and resulting polymer properties are extensively studied. However, also 6‐ and 7‐membered cyclic imino ethers can be polymerized via CROP. Together with the much less studied 4‐ and 5‐substituted main‐chain chiral poly(2‐oxazoline)s (P‐2‐OZO), these compounds are interesting monomers to enhance the versatility of (co)poly(cyclic imino ether)s. To emphasize the potential of such alternative cyclic imino ether monomers, we provide an overview on the polymerizations of 2‐oxazine (2‐OZI) and chiral 4‐ and 5‐substituted 2‐OZO as well as of selected properties of the resulting polymers. In addition, the hydrolysis of these polymers into the corresponding poly(alkylene imine)s will be addressed.

     

Study of the reaction between 1,5-naphtalene diisocyanate and polycaprolactone in different solvents

The reaction between polycaprolactone and 1,5-naphtalene diisocyanate has been investigated in solvents with different dielectric constants and hydrogen bonding powers (toluene, ethyl acetate, ethyl methyl ketone), and in the same solvents with the addition of a catalytic amount of dimethyl sulfoxide (DMSO). The reaction was considered to proceed over two steps, the reaction of the first NCO group being faster. The course of the reaction was measured by titration of the unreacted NCO groups, ¹H- and ¹³C-NMR spectroscopy, and size exclusion chromatography. By titration only the overall reaction order and reaction rate constants could be determined. DMSO accelerated the reaction in all three solvents, which was explained by the stabilization of the activation complex by DMSO. Both steps of the reaction could be specified by NMR spectroscopy. The ratio between the reaction rate constants for the first and the second step decreased with the increased hydrogen bonding strength of the solvent and with DMSO. By SEC only the reaction of the first NCO group could be determined due to the low resolution for higher molar mass reaction products with a broad distribution. The values obtained for the first step reaction rate constants were in good agreement with NMR values. © 1995 John Wiley & Sons, Inc.     

Trans-selective conversions of gamma-hydroxy-alpha,beta-alkynoic esters to gamma-hydroxy-alpha,beta-alkenoic esters

Gamma-hydroxy-alpha,beta-acetylenic esters are used as precursors to prepare gamma-hydroxy-alpha,beta-alkenoic esters by means of trans-selective additions of two hydrogen atoms or one hydrogen atom and one iodine atom across the triple bonds. These methods allow for the preparation of beta-substituted and alpha,beta-disubstituted alkenoic esters in highly stereoselective manners. [reaction--see text]     

Growth and production of buckwheat (Fagopyrum esculentum) treated with reduced, ambient, and enhanced UV-B radiation

The effect of enhanced UV-B radiation on buckwheat (Fagopyrum esculentum Moench. variety 'Darja'), an important high elevation crop, was studied in order to estimate its vulnerability in changing UV-B environment. Plants were grown in outdoor experiments from July to October under reduced and ambient UV-B levels, and an UV-B level simulating 17% ozone depletion in Ljubljana. During the development the following parameters were monitored: light saturated photosynthetic activity, transpiration, potential and effective photochemical efficiencies of photosystem II, the contents of photosynthetic pigments and methanol soluble UV-B absorbing compounds. At the end of the experiment, growth rate and production of seeds were estimated. In the following growth season the seeds collected from plants exposed to different UV-B treatments were tested for germination capacity. Total UV-B absorbing compounds during plant development were increased by UV-B radiation, photosynthetic pigments (chlorophyll a and b and carotenoids) decreased. Photosynthetic rate was lowered in an early stage of development. UV-B treatment resulted in the increase in the transpiration rate and consequently the decrease in water use efficiency (WUE). The disturbances in water economy and in photosynthesis affected the reproduction potential negatively; the production of seeds in plants cultivated under ambient and enhanced UV-B was 57 and 39% of the production of specimens treated with reduced UV-B, respectively. The germination of seeds collected from treated plants revealed on average about 95% success, independently of the treatment, but the time needed for germination was the shortest for seeds developed under enhanced UV-B level treatment. Enhanced UV-B radiation affected water relations and production of buckwheat, but not the potential of seeds for germination.     

New Series of Pyrazoles and Imidazo-Pyrazoles Targeting Different Cancer and Inflammation Pathways

(1) Background: different previously synthesized pyrazoles and imidazo-pyrazoles showed interesting anti-angiogenic action, being able to interfere with ERK1/2, AKT and p38MAPK phosphorylation in different manners and with different potency; (2) Methods: here, a new small compound library, endowed with the same differently decorated chemical scaffolds, has been synthetized to obtain new agents able to inhibit different pathways involved in inflammation, cancer and human platelet aggregation. (3) Results: most of the new synthesized derivatives resulted able to block ROS production, platelet aggregation and p38MAPK phosphorylation both in platelets and Human Umbilical Vein Endothelial cells (HUVEC). This paves the way for the development of new agents with anti-angiogenic activity.