A note onR 1-topological spaces

The purpose of the present note is to give a number of characterizations of theR ₁-axiom and to show that theR ₁-axiom is equivalent to the weakly Hausdorff axiom introduced byB. Banaschewski andJ. M. Maranda [2]. In anR ₁-space it is shown that the locally compactness property is also open hereditary and that the closure of an almost compact set is the union of the closures of its points. A necessary and sufficient condition is obtained under which a locally compact set dense in anR ₁-space is open. Finally a variant of a well-known theorem regarding two continuous functions of a topological space into aT ₂-space is formulated forR ₁-spaces.     

Enhanced conductivity and magnetic ordering in isostructural heavy atom radicals

Synthetic methods have been developed to generate the complete series of resonance-stabilized heterocyclic thia/selenazyl radicals 1a-4a. X-ray crystallographic studies confirm that all four radicals are isostructural, belonging to the tetragonal space group P42(1)m. The crystal structures consist of slipped pi-stack arrays of undimerized radicals packed about 4 centers running along the z direction, an arrangement which gives rise to a complex lattice-wide network of close intermolecular E2---E2' contacts. Variable temperature conductivity (sigma) measurements reveal an increase in conductivity with increasing selenium content, particularly so when selenium occupies the E2 position, with sigma(300 K) reaching a maximum (for E1 = E2 = Se) of 3.0 x 10(-4) S cm(-1). Thermal activation energies E(act) follow a similar profile, decreasing with increasing selenium content along the series 1a (0.43 eV), 3a (0.31 eV), 2a (0.27 eV), 4a (0.19 eV). Variable temperature magnetic susceptibility measurements indicate that all four radicals exhibit S = 1/2 Curie-Weiss behavior over the temperature range 20-300 K. At lower temperatures, the three selenium-based radicals display magnetic ordering. Radical 3a, with selenium positioned at the E1 site, undergoes a phase transition at 14 K to a weakly spin-canted (phi = 0.010 degrees) antiferromagnetic state. By contrast, radicals 2a and 4a, which both possess selenium in the E2 position, order ferromagnetically, with Curie temperatures of T(c) = 12.8 and 17.0 K, respectively. The coercive fields H(c) at 2 K of 2a (250 Oe) and 4a (1370 Oe) are much larger than those seen in conventional light atom organic ferromagnets. The transport properties of the entire series 1a-4a are discussed in the light of Extended Hückel Theory band structure calculations.     

Some Notes on <Emphasis Type="Italic">C</Emphasis>- and <Emphasis Type="Italic">C</Emphasis>*-quotients of Frames

We characterise C*-quotients and C-quotients of completely regular frames in terms of ?ech-Stone compactifications and Lindelöfications, respectively. The latter is a frame-theoretic result with no spatial counterpart. We also characterise C*-quotients and dense C-quotients of completely regular frames in terms of normal covers.     

A convenient preparative method for cyclic triphosphenium bromide and chloride salts

Analytically pure chloride and bromide salts of two different cyclic triphosphenium cations are prepared by the reaction of PX3 (X=Cl, Br) in the presence of the halogen-scavenging reagent cyclohexene. For the brominated species, the neutral, volatile 1,2-dibromocyclohexane byproduct is readily removed under reduced pressure, and the desired salts are obtained in high yield. Reactions involving phosphorus trichloride are complicated by the formation of salts containing both chloride and hydrogen dichloride anions. Reactivity experiments on potential undesired halogenated diphosphine byproducts suggest that the formation of such species can be prevented by increasing the concentration of cyclohexene employed in the reaction.     

On the sobriety of the inverse topology

An algebraic frame L with the finite intersection property (FIP) on compact elements is said to be polarised if every minimal prime element in it is complemented. In this note, we give a necessary and sufficient condition for the inverse topology on the set of minimal prime elements of such a frame to be sober. We also establish some sufficient conditions for sobriety when the polarisation condition is relaxed.     

Growth of first generation dendrons on SiO2: controlling chemisorption of transition metal coordination complexes

We have investigated the growth of first generation branched polyamidoamine dendrons on silicon dioxide as a way to tailor and control the subsequent chemisorption of transition metal coordination complexes. Beginning with straight-chain alkyl, amine-terminated self-assembled monolayers as anchors, we find that the efficiency of the dendritic branching step depends on the length of the anchor, it being nearly perfect on a 12-carbon chain anchor. The reaction of these layers, both the anchor layers and the first generation dendrons, with Ta[N(CH3)2]5 and Ti[N(CH3)2]4 have been examined in ultrahigh vacuum using X-ray photoelectron spectroscopy. We find that the saturation coverage increases with the density of terminal -NH2 groups; thus, the branching step has effectively amplified the chemisorptive capacity of the surface. Concerning the spatial extent of reaction we find that it depends on the thickness and structure of the organic layer. The thinnest layer cannot prevent penetration of the metal complex to the organic/SiO2 interface, where it can react with residual -OH, whereas, on the longer straight chain anchor, reaction occurs exclusively at the terminal -NH2 group. On the branched dendrons, the situation is more complex, and reaction occurs not only with the terminal -NH2 group but also likely with functional groups, such as -NH-(C=O)-, on the backbone of the branched dendron.     

5-Aminolevulinic acid-induced protoporphyrin-IX accumulation and associated phototoxicity in macrophages and oral cancer cell lines

Studies were carried out on 5-aminolevulinic acid (ALA)-induced protoporphyrin (PpIX) synthesis in mice peritoneal macrophages and two human oral squamous cell carcinoma (OSCC) cell lines NT8e and 4451. Cells were treated with 200 microg/ml ALA for 15 h and PpIX accumulation was monitored by spectrofluorometry and phototoxicity to red light (630+/-20 nm) was measured by MTT assay. PpIX accumulation was higher in macrophages as compared to OSCC cells under both normal serum concentration (10%) and conditions of serum depletion. The results on phototoxicity measurements correlated well with the levels of PpIX accumulation in both macrophages and cancer cells. While red light caused 20% phototoxicity in macrophages, no phototoxicity was seen in 4451 cells at 10% serum. Decrease in serum concentration to 5% and 1% led to higher phototoxicity corresponding to 40% and 70% in macrophages and 10% and 15% in 4451 cells. Similar results were obtained in NT8e cell line. Propidium iodide staining followed by fluorescence microscopic observations on photodynamically treated co-culture of murine or human macrophages and cancer cells showed selective damage to macrophages. These results suggest that in OSCC, macrophages would contribute more to tumor PpIX level than tumor cells themselves and PDT may lead to selective killing of macrophages at the site of treatment. Since macrophages are responsible for production and secretion of various tumor growth mediators, the effect of selective macrophage killing on the outcome of PDT would be significant.     

Tuning the Ground and Excited State Dynamics of Hemithioindigo Molecular Motors by Changing Substituents

Efficiency and performance of light triggered molecular motors are crucial features that need to be mechanistically understood to improve the performance and enable conscious property tailoring for specific applications. In this work, three different hemithioindigo-based molecular motors are investigated and all four steps in their complete unidirectional rotation are unraveled fully quantitatively. Transient absorption spectroscopy across twelve orders of magnitude in time is used to probe the fs nuclear motions up to the ms thermal kinetics, covering the timeframe of the whole motor rotation. The newly known full mechanisms allow simulation of the motor systems to scrutinize their performance at realistic illumination conditions. This highlights the importance of photoisomerization quantum yields for the rotation speed. The substitution pattern in close proximity to the rotation axle influences the excited and ground state properties. Reduction of electron donation and concomitant increase of steric hindrance leads to faster photoisomerization reactions with quasi-ballistic behavior, but also to a slight decrease in the quantum efficiency. The expected decelerating effects of increased sterics are primarily manifested in the ground state. A promising approach for next-generation hemithioindigo motors is to elevate electron donation at the rotor fragment followed by an increase of steric hindrance.     

A broader view of the almost Lindelöf property

By first finding necessary and sufficient conditions for the realcompact coreflection, νL, and the regular Lindelöf coreflection, λL, of a completely regular frame L to be isomorphic, we define a frame L to be almost Lindelöf if it is Lindelöf or λL → L is a one-point extension. This agrees with the condition “νL is Lindelöf and L is realcompact or νL is a one-point extension”, which would be a frame version of what are called almost Lindelöf spaces. Thus, the condition “νX is Lindelöf”, which is added in the definition of almost Lindelöf spaces, serves only to compensate for the lack of the regular Lindelöf reflection in Top, and can be dispensed with by concentrating on the frame \({\mathfrak {O}X}\) instead of the space X.