Fluence Rate-Dependent Photobleaching of Intratumorally Administered Pc 4 Does not Predict Tumor Growth Delay

We examined effects of fluence rate on the photobleaching of the photosensitizer Pc 4 during photodynamic therapy (PDT) and the relationship between photobleaching and tumor response to PDT. BALB/c mice with intradermal EMT6 tumors were given 0.03 mg kg^?1 Pc 4 by intratumor injection and irradiated at 667 nm with an irradiance of 50 or 150 mW cm^?2 to a fluence of 100 J cm^?2. While no cures were attained, significant tumor growth delay was demonstrated at both irradiances compared with drug‐only controls. There was no significant difference in tumor responses to these two irradiances (P = 0.857). Fluorescence spectroscopy was used to monitor the bleaching of Pc 4 during irradiation, with more rapid bleaching with respect to fluence shown at the higher irradiance. No significant correlation was found between fluorescence photobleaching and tumor regrowth for the data interpreted as a whole. Within each treatment group, weak associations between photobleaching and outcome were observed. In the 50 mW cm^?2 group, enhanced photobleaching was associated with prolonged growth delay (P = 0.188), while at 150 mW cm^?2 this trend was reversed (P = 0.308). Thus, it appears that Pc 4 photobleaching is not a strong predictor of individual tumor response to Pc 4‐PDT under these treatment conditions.     

Photochemical oxygen consumption, oxygen evolution and spectral changes during UVA irradiation of EMT6 spheroids.

Remarkable rates of oxygen consumption are observed via microelectrode measurements immediately upon the onset of 325 nm irradiation of multicell tumor spheroids. Consumption is irradiance dependent over the range 20-200 mW cm-2, and its magnitude is comparable to that observed previously in the same system using exogenous photosensitizers. Oscillations in the oxygen concentrations suggest that oxygen is also being evolved during irradiation. Oxygen evolution is likely the result of enzymatic dissociation of hydrogen peroxide, which is formed through UV-induced photochemistry. Irradiation of spheroids at 442 and at 514 nm produces a much more modest but detectable oxygen consumption. The dynamics of oxygen concentration changes are quite different at these wavelengths, suggesting a different photochemical mechanism. In these cases, initial oxygen depletion is followed immediately by a more gradual, monotonic increase in the oxygen concentration, consistent with irreversible photobleaching. No oscillations in the oxygen concentration are detectable. At 662 nm, no oxygen consumption was observed over the range of irradiances studied. Fluorescence spectra of cells prior to irradiation include contributions from anthranilic acid and reduced nicotinamide adenine dinucleotide (NADH). During 325 nm irradiation, anthranilic acid is rapidly and irreversibly bleached, while NADH emission undergoes only modest reduction.     

The 2-Pebbling Property and a Conjecture of Graham's

The pebbling number of a graph G, f(G), is the least m such that, however m pebbles are placed on the vertices of G, we can move a pebble to any vertex by a sequence of moves, each move taking two pebbles off one vertex and placing one on an adjacent vertex. It is conjectured that for all graphs G and H, f(G 2H)hf(G)f(H).¶Let C_m and C_n be cycles. We prove that f(C_m 2C_n)hf(C_m) f(C_n) for all but a finite number of possible cases. We also prove that f(G2T)hf(G) f(T) when G has the 2-pebbling property and T is any tree.     

Complexes of pyrene with 2,4,6-trinitroanisole. Studies of association in solution and the crystal structure of the 1:1 complex

Cyclohexane solutions of 2,4,6-trinitroanisole (A) containing excess pyrene (D) can be described in terms of a double equilibrium involving complexes DA and D₂A. Formation constants for these complexes from A and from DA respectively from three independent experiments are in good agreement, the average values being K₁= 9.7 kg mol^-1 and K₂= 1.8 kg mol^-1 at 33.5°. The crystalline complex was obtained by gel diffusion. The mw (C₂₃H₁₅N₃O₇) corresponds to 1:1 stoichiometry C₁₆H₁₀, C₇H₅N₃O₇, X-ray structure data: P2₁/c, a = 10.633(7), b= 16.336(8), c = 11.683(7) Å, β = 94.62(12)°, V = 2023 ų, F₀₀₀ = 924, μ(CuKα) = 8.3 cm^-1, Z = 4. R = 0.091 for 1572 reflexions. The crystal contains extended stacks ADADA, parallel to (101). The pyrene molecules are disordered by rotation over two sites. The majority site has an occupancy factor of 0.544(2). The angle between the normals to the mean planes of A and D is 7.0(4)°, allowing the nitro groups of A to twist out of the plane of the benzene ring by 41.0(1.0), 2.7(5) and 20.7(8)°.     

The application of semiconductor diode lasers to the soldering of electronic components

Work being carried out at the University of Hull into the application of high power laser diodes to the soldering process is described. The commercial availability of semiconductor diode lasers has brought an exciting new soldering tool to the manufacturers of electronics assemblies: trends in electronics assembly are to increasingly high-density interconnections and increasing device functionality. Packages are reducing in size and pin-out counts are increasing. Currently 0.010–0.016 inch lead pitch devices are being introduced by many manufacturers. Lasers can be used with advantage in the soldering of such fine and precise devices and high-power semiconductor laser diodes can be used to build compact, flexible and controllable soldering units. With computer control of the power and duration of the laser energy it is possible to ensure consistent and reliable soldering. To achieve this, however, the various parameters involved in the laser beam-solder assembly interaction need to be carefully defined. This paper reports on our identification of these parameters and the salient design features of an automated diode laser soldering system.     

Pulsed fm NMR/on studies of single crystal54MnNi and125SbFe

Precision field shift studies of B_appl-8T using pulsed FM NMR/ON along hard directions (eg <100>⁵⁴MnNi, <112>¹²⁵SbFe and the easy axis (<111>⁵⁴MnNi, <100>¹²⁵SbFe) yield no measurable Knight shifts within the uncertainty allowed by current accuracy of the nuclear moments. This is in striking contrast to earlier measurements with the same apparatus that yielded K=+1.5 (4)% for⁶⁰CoFe. The modulation frequency dependences of the pulsed FMNMR/ON signals are investigated for a variety of rf parameters and compared with model predictions.     

Pulsed magnetic field exposure during pregnancy and implications for NMR foetal imaging: a study with mice

Following the recent progress in NMR imaging of the foetus in utero an investigation has been made of the effect of exposure to strong pulsed magnetic fields on the pregnancy of mice and the post natal development of their litters. 23 pregnant mice received exposures ranging from 3.5-12kT/s with pulse periods in the range 0.33-0.56ms at various times during gestation. A similar number of pregnant mice served as controls. No adverse effect was observed on the pregnancy. There was no significant difference between the litter numbers and growth rates of the exposed litters compared with controls. The implications of these results are discussed with regard to the safety of NMR imaging during pregnancy.     

Aliphatic–aromatic copolyesters derived from 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol

With the massive changes taking place in the world today, the development of new thermally and mechanically stable polymeric materials is of utmost importance. This article focuses on the synthesis and thermal characterization of a new series of copolyesters that incorporate both aromatic as well as aliphatic diols. This is of interest because most polymer materials that exhibit high thermal and/or mechanical properties contain aromatic monomer units only. These aromatic units usually contribute to either the thermal or mechanical properties but typically not both. An example of this is bisphenol A polycarbonate, which has high mechanical properties but only moderate thermal properties when compared, for example, to polyimides. In recent years there has been an interest in copolyesters that contain 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol (CBDO). This aliphatic monomer imparts some very unique thermal as well as mechanical properties. This article will report the thermal properties of a new series of CBDO‐based copolyesters. These polymers include CBDO, a series of bisphenols, and terephthaloyl chloride. The series of bisphenols discussed here include bisphenol A, AF, F, and HPF. These polymers display glass transition temperatures near 200 °C and decomposition temperatures from 390–420 °C (Argon) and from 385–410 °C (Air). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3473–3478, 2004