An effect of side chain length on the solution structure of poly(9,9-dialkylfluorene)s in toluene

The effect of side chain length of π-conjugated poly(9,9-dialkylfluorene)s has been studied in semi-dilute (10 mg/mL) toluene solutions using small-angle neutron scattering (SANS) and ¹H and ²H NMR spectroscopies. Under these conditions, SANS data indicate that poly(9,9-dinonylfluorene) and poly(9,9-dioctylfluorene) are dissolved down to the molecule level and appear as elongated one-dimensional chains (length >20-30 nm). In contrast, the shorter side chain polymers exhibit a self-association so that poly(9,9-diheptylfluorene) forms thin sheet-like (∼1 nm) and poly(9,9-dihexylfluorene) thin (∼1 nm) and thick sheet-like (>6 nm) aggregates. ¹H NMR data, together with the density functional theory (DFT) calculations, however, show that this occurs without changes in the conformation of the polymer backbone.     

A unified framework of opening and closure operators with respect to arbitrary fuzzy relations

 This paper is devoted to a general concept of openness and closedness with respect to arbitrary fuzzy relations – along with appropriate opening and closure operators. It is shown that the proposed framework unifies existing concepts, in particular, the one for fuzzy preorderings as well as the triangular norm-based approach to fuzzy mathematical morphology. The author acknowledges support of the K _plus Competence Center Program which is funded by the Austrian Government, the Province of Upper Austria, and the Chamber of Commerce of Upper Austria.     

Notes on waves with negative phase velocity

Negative refraction is a wave phenomenon beyond geometrical optics - it depends on the way waves behave when their phase velocity reaches a zero. Various forms of linear wave processes in media can be concisely described in one wave equation that is inspired by the interpretation of a medium as an effective space-time geometry. Depending on the conformal factor of the effective metric, the waves may show positive or negative refraction. For electromagnetic waves in two-dimensional dielectrics the conformal factor corresponds to the impedance.     

Rates of reinfection with Echinococcus granulosus, Taenia hydatigena, taenia ovis and other cestodes in a rural dog population in Uruguay

Forced thinking is an incompletely understood and rarely described epileptic aura. We studied three patients with forced thinking from left frontal lesions, two neoplastic and one vascular. All three experienced repetitive, intrusive thoughts at the onset of seizures. Their forced thinking was associated with the desire to vocalize, orobuccal movements, and speech arrest. The episodes occurred with other ictal manifestations and responded to antiseizure therapy. These patients suggest that epileptic forced thinking is a heterogeneous phenomenon; forced thinking from left frontal lesions is a manifestation of expressive language and is distinct from experiential thoughts arising from temporal limbic foci.     

Incidence of neoplasms in ages 0-19 y in parts of Sweden with high 137Cs fallout after the Chernobyl accident

An experiment was conducted to elucidate the origin of tetraploids (2n = 4x = 44) of Paragonimus westermani that occur together with diploid (2n = 2x = 22) and triploid (2n = 3x = 33) types in Liaoning Province, the People's Republic of China. Metacercariae of the diploid type, obtained from Hyogo Prefecture, Japan, and those of the triploid type from Tsushima, Nagasaki Prefecture, Japan, were mixed and inoculated into dogs and cats. The following results were obtained. The flukes were found in pairs within cysts in random combinations of 2x + 2x, 2x + 3x, and 3x + 3x (7:15:7). Oocytes in the oviduct were at stages from diplotene to metaphase. In a triploid fluke encysted with a diploid fluke, the primary oocytes were intruded by sperms from the diploid fluke. In the primary oocytes of diploid as well as triploid flukes, from diplotene to diakinesis, the homologues of the nucleolar chromosomes were heteromorphic as far as the size of the short arm was concerned. This implies that the triploid is an autotriploid generated in an ancestral diploid population that was polymorphic for the nucleolar chromosome.     

A comparison between three simple crystallographic principles of precipitate morphology

The connection between the optimum shape and orientation relationship of precipitates in a solid is examined. Three simple criteria for precipitate morphology are compared and illustrated schematically: the principle that precipitate dimensions tend to be inverse to the magnitude of the transformation strain; the postulate that precipitates are bounded by unrotated planes (eigenplanes); and the proposal that interfaces are parallel to the planes of three independent dislocation loop arrays necessary to accommodate the transformation strain completely. These principles are illustrated for different orientation relationships, and it is shown that special features are displayed by invariant-line precipitates. The implications of these criteria for experimental studies of precipitate morphologies are discussed and their predictions compared with results from a recent study of lath-shaped precipitates in Cu-Cr alloys. This article is based on a presentation made at the Pacific Rim Conference on the “Roles of Shear and Diffusion in the Formation of Plate-Shaped Transformation Products,” held December 18-22, 1992, in Kona, Hawaii, under the auspices of ASM INTERNATIONAL’S Phase Transformations Committee.     

Oxygen-haemoglobin dissociation curve in hypoxic rats of first or second generation

1. Albino Wistar rats were raised in a normobaric hypoxic environment (10% O2 in N2). Two generations of hypoxic rats were observed for changes in their haemoglobin-oxygen (Hb-O2) dissociation curves (ODC), 2,3-diphosphoglycerate (2,3-DPG), haemoglobin (Hb), and Hill co-efficients at P50 (n50). The first generation were called (H1) and the second generation (H2). The control group (N) had a normoxic environment. 2. Thirty-five rats (13 N rats, 12 H1 rats and 10 H2 rats) were used. The 2,3-DPG was significantly higher in both hypoxic groups when compared with N rats (2.02 +/- 0.51 mmol/L) but 2,3-DPG of H2 rats was significantly lower than that of H1 rats (H1 = 3.48 +/- 0.58 mmol/L and H2 = 2.76 +/- 0.54 mmol/L). The haemoglobin values were N = 2.00 +/- 0.26, H1 = 2.65 +/- 0.32 and H2 = 2.36 +/- 0.30 mmol/L, respectively. 3. We observed considerable differences in Hb-O2 affinity between the three groups of rats. In standard conditions (pH = 7.400; pCO2 = 40 mmHg at 37 degrees C) the H1 rats showed a significantly decreased Hb-O2 affinity (P50,st = 37.0 +/- 1.3 mmHg) when compared with both H2 and N rats; the H2 rats showed a significantly increased Hb-O2 affinity (P50,st = 31.1 +/- 1.5 mmHg) when compared with controls N (P50,st = 34.7 +/- 2.1 mmHg). There were no significant differences in n50 values: N = 2.88 +/- 0.44; H1 = 2.88 +/- 0.77; and H2 = 2.94 +/- 0.67.(ABSTRACT TRUNCATED AT 400 WORDS)