Atomic-scale electron-beam sculpting of near-defect-free graphene nanostructures

In order to harvest the many promising properties of graphene in (electronic) applications, a technique is required to cut, shape, or sculpt the material on the nanoscale without inducing damage to its atomic structure, as this drastically influences the electronic properties of the nanostructure. Here, we reveal a temperature-dependent self-repair mechanism that allows near-damage-free atomic-scale sculpting of graphene using a focused electron beam. We demonstrate that by sculpting at temperatures above 600 °C, an intrinsic self-repair mechanism keeps the graphene in a single-crystalline state during cutting, even though the electron beam induces considerable damage. Self-repair is mediated by mobile carbon ad-atoms that constantly repair the defects caused by the electron beam. Our technique allows reproducible fabrication and simultaneous imaging of single-crystalline free-standing nanoribbons, nanotubes, nanopores, and single carbon chains.     

Differential mobility spectrometry of isomeric protonated dipeptides: modifier and field effects on ion mobility and stability

The ability to resolve isomeric protonated dipeptides was investigated with the new technique of differential ion mobility mass spectrometry that uses "modifier" molecules to enhance differential mobility. Two pairs of protonated peptides [glycine-alanine (GlyAla) and alanine-glycine (AlaGly), glycine-serine (GlySer) and serine-glycine (SerGly)] and eight different modifiers (water, 2-propanol, 1,5-hexadiene, 2-chloropropane, chlorobenzene, dichloromethane, acetonitrile, and cyclohexane) were used in the initial study. Separation of the protonated peptides was found to be dependent on the mass and proton affinity of the modifier and combinations of functionalities present in the modifier and the analyte ion. Six of the eight modifiers (water, 2-propanol, chlorobenzene, cyclohexane, dichloromethane, and acetonitrile) were able to separate the protonated isomeric peptide pairs, and generally, modifiers with electron-rich groups performed the best. In the presence of some modifiers, a reduction of ion current was observed under the highest field conditions (>115 Td). Dopant-catalyzed isomerization, likely by proton-transport catalysis, and field-induced fragmentation may have contributed to these losses. Two high vapor pressure modifiers, 1,5-hexadiene and 2-chloropropane, significantly influenced ion formation leading to the formation of stable cluster populations that could be observed in the mass spectrometer. Although not a major concern, both fragmentation and influence of modifier evaporation warrant further studies in order to fully understand and possibly eliminate them.     

Further Validity Evidence for the Teacher Version of the Child Symptom lnventory-4.

The reliability and validity of the teacher version of the Child Symptom Inventory-4 (CSI-4) was examined in 248 boys referred for evaluation of behavioral and emotional problems. The CSI-4 is a behavior rating scale whose items correspond to the symptoms of DSM-IV-defined disorders. The results indicated satisfactory internal consistency reliabilities for most symptom categories, and CSI-4 scores converged and diverged in a theoretically consistent manner with respective scales of the Teacher's Report Form (Achenbach, 1991), the IOWA Conners Teacher's Rating Scale (Loney & Milich, 1982), and the Diagnostic Interview for Children and Adolescents-Revised Parent Version (DICA-P; Reich, Shayka, & Taibleson, 1991). Correlations between teacher and parent CSI-4 ratings were low to moderate, whereas all correlations between teacher ratings and child self report were very low (rs     

Domain-specific knowledge and memory performance: A comparison of high- and low-aptitude children.

Two studies compared memory performance and text comprehension of groups that were equivalent on domain-specific knowledge but differed in overall aptitude, to investigate whether prior knowledge about a particular domain or overall aptitude level was more important when the task was to acquire and use new information in the domain of interest. Both studies dealt with third-, fifth-, and seventh-grade soccer experts' and novices' memory and comprehension of a story dealing with a soccer game. Several measures of memory performance, memory monitoring, and text comprehension were used. Levels of soccer knowledge and of overall aptitude were varied in a factorial design. Neither study detected significant differences between high-aptitude and low-aptitude experts, regardless of their ages. Low aptitude experts outperformed high-aptitude novices on all memory and comprehension measures. The results indicate that domain-specific knowledge can compensate for low overall aptitude on domain-related cognitive tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CD4-CD8-C.B-17 SCID thymocytes enter the CD4+CD8+ stage in the presence of neonatally grafted T cells

Our previous studies in iron-loaded rat heart cells showed that in vitro iron loading results in peroxidative injury, manifested in a marked decrease in rate and amplitude of heart cell contractility and rhythmicity, which is correctable by treatment with deferoxamine (DF). In the present studies we explored the role of mitochondrial damage in myocardial iron toxicity. Iron loading by 24-hour incubation with 0.36 mmol/L ferric ammonium citrate resulted in a decrease in the activity of nicotinamide adenine dinucleotide (NADH)-cytochrome c oxidoreductase (complex I+III) to 35.3%+/-11.2% of the value in untreated controls; of succinate-cytochrome c oxidoreductase (complex II+III) to 57.4%+/-3.1%; and of succinate dehydrogenase to 63.5%+/-12.6% (p < 0.001 in all cases). The decrease in activity of other mitochondrial enzymes, including NADH-ferricyanide reductase, succinate ubiquinone oxidoreductase (complex II), cytochrome c oxidase (complex IV), and ubiquinol cytochrome c oxidoreductase (complex III), was less impressive and ranged from 71.5%+/-15.8% to 91.5%+/-14.6% of controls. That the observed loss of respiratory enzyme activity was a specific effect of iron toxicity was clearly demonstrated by the complete restoration of enzyme activities by in vitro iron chelation therapy. Sequential treatment with iron and doxorubicin caused a loss of complex I+III and complex II+III activity that was greater than that seen with either agent alone but was only partially correctable by DF treatment. Alterations in cellular adenosine triphosphate measurements paralleled very closely the changes observed in respiratory complex activity. These findings demonstrate for the first time the impairment of cardiac mitochondrial respiratory enzyme activity caused by iron loading at conditions formerly shown to produce severe abnormalities in contractility and rhythmicity.     

Immunoelectron microscopic localization of plasminogen activator inhibitor type 1 (PAI-1) in smooth muscle cells from morphologically normal and atherosclerotic human arteries

Vascular wall fibrinolytic system proteins are believed to play a pivotal role in atherogenesis. Tissue-type plasminogen activator (t-PA) and urokinase plasminogen activator (u-PA) influence persistence of luminal thrombi and proteolysis of extracellular matrix, respectively. The major physiologic inhibitor of t-PA and u-PA is plasminogen activator inhibitor type 1 (PAI-1). All three of these fibrinolytic system proteins have been detected in vascular endothelial cells, smooth muscle cells, and macrophages by light microscopic immunohistochemistry. This study was undertaken to delineate, by immunoelectron microscopy, the loci of PAI-1 in smooth muscle cells from intact morphologically normal and atherosclerotic human arteries as well as in isolated and cultured smooth muscle cells from arteries. In intact vessels, PAI-1 immunoreactivity was associated with contractile filaments in cells in both normal and atherosclerotic tissues. Lipid-laden smooth muscle cells in atherosclerotic vessels were mainly of the synthetic phenotype and displayed lesser amounts of PAI-1 associated with rough endoplasmic reticulum and contractile filaments. Isolated smooth muscle cells exhibited either a contractile or synthetic phenotype. In the cells with a contractile phenotype, PAI-1 was associated with the contractile elements, whereas in the cells with a synthetic phenotype, the PAI-1 was associated predominantly with elements of the endoplasmic reticulum. Because PAI-1 is associated predominantly with contractile filaments in smooth muscle cells, the net amount of immunodetectable PAI-1 appears to be greater in contractile compared with synthetic phenotype cells.     

Microprocesses of metal dusting on nickel and Ni-base alloys

Microstructural and microchemical investigations were carried out on nickel and Inconel 600 after exposure to strongly carburizing atmospheres at temperatures of about 600 to 650°C to study their metal dusting behaviour. Contrary to iron and low-alloy steels, where metal dusting proceeds via the formation and disintegration of a metastable carbide M₃C, both nickel and Inconel 600 directly disintegrate. Inside the metal this disintegration proceeds by formation of thin graphite filaments of nearly 10 nm in diameter, the atomic basal planes of which are oriented perpendicular to the surface thus effecting a high reactivity at the growth front. Subsequently, fine particles or larger parts of the metal surface layer are released, which are buried in the deposited graphite layer on the surface. In case of Inconel 600, containing Cr with mass contents of about 15%, the disintegration can be delayed by the formation of a chromium oxide layer, but no safe protection against metal dusting is obtained.     

Questionnaire for Eating Disorder Diagnoses: Reliability and validity of operationalizing DSM—IV criteria into a self-report format: Correction.

Reports an error in the original article by L. B. Mintz et al (Journal of Counseling Psychology, 1997 [Jan], Vol 44[1], 63–79). On page 78, a reference to work by C. G. Fairburn et al was cited incorrectly and is corrected here. Also, there were 3 text citations that contained errors which are corrected here. (The following abstract of this article originally appeared in record 1997-02519-008.) The Questionnaire for Eating Disorder Diagnoses (Q-EDD) operationalizes eating disorder criteria of the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders and differentiates (a) between those with and without an eating disorder diagnosis, (b) among eating-disordered, symptomatic, and asymptomatic individuals, and (c) between those with anorexia and bulimia diagnoses. Three studies examined the Q-EDD's psychometric properties. Convergent validity was supported by correspondence between Q-EDD diagnoses and established inventory scores. Criterion validity was supported by high correspondence between Q-EDD and interview or clinician diagnoses. Incremental validity was supported by greater accuracy of Q-EDD diagnoses than those yielded by an established inventory. Test-retest reliability and interscorer agreement were very good. Future use is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning to be creative.

Comments on R. J. Sternberg and T. I. Lubart's article (see record 83-30546) on the neglect and problems of creativity as a research topic. The original authors suggested a confluence approach to the study of creativity, encompassing contributions both within and without psychology. Schneider agrees with this suggestion, but argues that its success depends on finding and connecting all pertinent links concerning creativity. The integration of a broad range of research with the study of creativity seems likely to increase the chance of progress in understanding and perhaps "teaching" creativity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cellular uptake of saposin (SAP) precursor and lysosomal delivery by the low density lipoprotein receptor-related protein (LRP)

Sphingolipid activator proteins SAP-A, -B, -C and -D (also called saposins) are generated by proteolytic processing from a 73 kDa precursor and function as obligatory activators of lysosomal enzymes involved in glycosphingolipid metabolism. Although the SAP precursor can be recognized by the mannose-6-phosphate (M-6-P) receptor and shuttled directly from the secretory pathway to the lysosome, a substantial fraction of newly synthesized precursor is secreted from the cell where it may participate in sphingolipid transport and signaling events. Re-uptake of the secreted precursor is mediated by high-affinity cell surface receptors that are apparently distinct from the M-6-P receptor. We found that the low density lipoprotein receptor-related protein (LRP), a multifunctional endocytic receptor that is expressed on most cells, can mediate cellular uptake and lysosomal delivery of SAP precursor. Additional in vivo experiments in mice revealed that the mannose receptor system on macrophages also participates in precursor internalization. We conclude that SAP precursor gains entry into cells by at least three independent receptor mechanisms including the M-6-P receptor, the mannose receptor and LRP.