On the cognitive structure of basic arithmetic skills: Operation, order, and symbol transfer effects.

In 2 experiments, 24 college students practiced extensively on single-digit multiplication and division problems (e.g.,?=?6?×?9; 42?×?6) and were tested on both practice problems and several altered versions of those problems, which were constructed by changing the required operation, operand order, or arithmetic symbol. There was strong positive transfer to test problems that had exactly the same elements (the numbers and the required operation) as a practice problem, regardless of whether other factors such as operand order or symbol were changed, but little if any positive transfer to test problems that did not have the same elements as a practice problem. An identical elements framework is used to interpret these results and implications for existing computational models of arithmetic fact retrieval and for the development of arithmetic skill are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of inhibin immunoreactivity in post-menopausal women with ovarian tumours

We report on three patients who presented with a cerebellar medulloblastoma at age 48, 53, and 59 years. Histopathology showed typical features of medulloblastoma, in one case with marked neuronal differentiation. In addition, all neoplasms contained focal accumulations of mature fat cells. Immunoreactivity of adipocytes for S-100 protein, neuron-specific enolase, synaptophysin, microtubule-associated protein-2, and glial fibrillary acidic protein and the lack of immunoreactivity to type IV collagen suggest lipomatous differentiation of neoplastic primitive neuroectodermal cells rather than an admixture of mesenchymal elements. Mitotic activity was low and the growth faction, as determined by the MIB-1 labeling index, was less than 5%. All patients are alive with a recurrence-free interval ranging from 3.5 to 12 years. These three patients and five similar previously reported cases all fit into the concept of the lipomatous medulloblastoma as a new clinicopathological entity characterized by (a) typical features of a cerebellar medulloblastoma with advanced neuronal differentiation, (b) areas of lipomatous differentiation, (c) low proliferative potential, (d) manifestation in adults (mean age, 50 years), and (e) apparent favorable clinical prognosis.     

Proteolysis of bovine alpha s2-casein by chymosin

Proteolysis of bovine alpha s2-casein by chymosin (E. C. 3.4.23.4) in solution in 100 mM Na phosphate buffer, pH 6.5, at 30 degrees C was studied by reversed-phase (RP)-HPLC and urea-polyacrylamide gel electrophoresis (PAGE). Chymosin hydrolyzed alpha s2-casein in solution to eight peptides detectable by urea-PAGE. Peptides soluble in acetate buffer, pH 4.6, were isolated by RP-HPLC on a C18 column using an acetonitrile/water gradient and identified from their N-terminal amino acid sequence. The chymosin cleavage sites were at the bonds Phe88-Tyr89, Tyr95-Leu96, Gln97-Tyr98, Tyr98-Leu99, Phe163-Leu164, Phe174-Ala175 and Tyr179-Leu180. Chymosin cleavage sites were restricted to the hydrophobic regions of the molecule. The bond-type in alpha s2-casein cleaved by chymosin was in agreement with that found to be susceptible to chymosin in other caseins. The primary site of chymosin action on alpha s2-casein appeared to be at Phe88-Tyr89.     

Postembolic colonic infarction

From a total of 23 cases from five hospitals, acute colonic mucosal necrosis developed in three patients following transcatheter embolotherapy for colonic hemorrhage. Although embolic therapy for lower gastrointestinal bleeding is associated with appreciable risk, these risks are less than those of emergency operation for hemorrhage. The alternative transcatheter therapeutic modality, vasopressin infusion, is often associated with continued or recurrent hemorrhage, is relatively contraindicated in patients with coronary disease, and produces numerous complications. Transcatheter embolotherapy is recommended for patients with colonic bleeding who have a contraindication to vasopressin administration, who are refractory to vasopressin, or who rebleed following treatment with vasopressin.     

Rate characteristics for the reaction of carboxyl-modified polyamide with potassium hydroxide

Nylon 66 fiber, carrying 2.0 meq/g of carboxyl groups from radiation grafting of acrylic acid, was found to display chemical kinetics strongly first order with respect to the potassium hydroxide. The apparent rate constant k' remains nearly unchanged as the initial bath pH is varied from 8.3 to 10.5. At this point, the value of k' drops sharply, and continues to drop as the initial pH is increased. This discontinuity is attributed to a previously reported morphological transition indicated by a break in titration data at the corresponding equilibrium point of pH 9.2.     

Electrosynthesis in systems of two immiscible liquids and a phase transfer catalyst. VI. The influence of zinc chloride on the chlorination of naphthalene

The influence of zinc chloride on the chlorination of naphthalene by electrolysis in a water-methylene chloride emulsion and using tetrabutylammonium ion as a phase transfer catalyst is described. It is shown that when the aqueous medium contains both NaCl and ZnCl₂ it is the anion ZnCl ₄ ^2– which transfers into the organic phase and it is confirmed that the presence of ZnCl₂ in the electrolyte is, indeed, beneficial. The electrolyses have been carried out in both divided and undivided cells and in both the organic yield of 1-chloronaphthalene can exceed 80% but the former is better from the viewpoint of speed of electrolysis; in the divided cell, the conversion was 85% (cf. typically 60% in the undivided cell) after the passage of 2.3 F mol^–1 of naphthalene. Possible mechanisms for the effect of ZnCl[in2] are discussed.On leave of absence from the Faculty of Technology, University of Banja Luka, Yugoslavia.     

Effects of cuing on short-term retention of order information.

In two experiments, subjects recalled one of two letter sequences following a digit-filled retention interval. Recall performance was increased by precues informing subjects which letter sequence would be tested, and the cuing advantage remained throughout 60-digit retention intervals. No improvement was found, however, for cues occurring after the letters but before the digits. The cuing effects were attributed to encoding, not rehearsal, processes and were explained by a version of the Estes perturbation model, which included a long-term storage component and a fixed perturbation probability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitating text memory with additional processing opportunities in rapid sequential reading.

Previous research indicates that during conventional reading, readers pause at particular loci within a text, presumably for the purpose of higher level processing and integration. If such pausing is necessary for efficient text comprehension and memory, then providing readers with equivalent processing opportunities with strategically placed pauses in rapid sequential visual presentation (RSVP) text displays should facilitate comprehension and memory. Three experiments are reported in which various time parameters of RSVP displays are manipulated. The results indicate that memory for specific text is facilitated when additional processing time is provided. However, how and where the additional time is distributed within a text, over broad limits, is not important. We use a method of text memory assessment that is not typically used in RSVP research and that is more sensitive to text presentation manipulations than the commonly used multiple-choice questions. The fill-in-the-blank technique also provides evidence that memory representations for texts are structured as meaningful subsentence units. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proteolytic specificity of cathepsin D on bovine F-actin

Proteolysis of bovine F-actin by cathepsin D (E.C. 3.4.23.5) in 50 mM Na acetate buffer, pH 5.5, at 37°C was investigated using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and reverse-phase high performance liquid chromatography (RP-HPLC). Actin was hydrolyzed by cathepsin D during incubation to peptides detectable by RP-HPLC, although no degradation products were detected by SDS-PAGE. Peptides (2% trichloroacetic acid-soluble) from the hydrolyzate were isolated by RP-HPLC on a C(18) column using an acetonitrile/water gradient and identified from their N-terminal sequence and mass. Cathepsin D cleavage sites were identified at Cys(12)-Asp(13), Gly(22)-Phe(23), Arg(30)-Ala(31), Thr(79)-Asn(80), Ile(87)-Trp(88), Thr(91)-Phe(92), Phe(92)-Tyr(93), Arg(97)-Val(98), His(103)-Pro(104), Leu(107)-Thr(108), Thr(108)-Glu(109), Lys(120)-Met(121), Leu(144)-Tyr(145), Ile(153)-Val(154), Leu(155)-Asp(156), Ile(167)-Tyr(168), Leu(180)-Asp(181), Met(192)-Lys(193), Leu(195)-Thr(196), Arg(208)-Glu(209), Arg(212)-Asp(213), Leu(223)-Asp(224), Lys(240)-Ser(241), Thr(262)-Leu(263), Trp(342)-Ile(343), Arg(349)-Ser(350), Trp(358)-Ile(359), and Lys(375)-Cys(376). In general, cathepsin D preferentially cleaved bonds containing at least one hydrophobic amino acid residue. The results of this study showed that actin was degraded extensively by cathepsin D with peptides released from numerous locations in the protein molecule.