The Emergence of Zerovalent Carbon Compounds from Structural Curiosities to Organocatalysts

Low-valent main group compounds have reactivity patterns and properties reminiscent of transition metals. While divalent carbon compounds such as carbenes are widely studied ligands and organocatalysts, zerovalent carbon species have received considerably less attention. This perspective highlights the properties and reactivity of zerovalent carbon compounds, focusing on their first applications as organocatalysts for small molecule reduction and polymerization reactions

The accuracy of frozen section analysis in ultrasound- guided core needle biopsy of breast lesions

<p>Abstract</p> <p>Background</p> <p>Limited data are available to evaluate the accuracy of frozen section analysis and ultrasound- guided core needle biopsy of the breast.</p> <p>Methods</p> <p>In a retrospective analysis data of 120 consecutive handheldultrasound- guided 14- gauge automated core needle biopsies (CNB) in 109 consecutive patients with breast lesions between 2006 and 2007 were evaluated.</p> <p>Results</p> <p>In our outpatient clinic120 CNB were performed. In 59/120 (49.2%) cases we compared histological diagnosis on frozen sections with those on paraffin sections of CNB and finally with the result of open biopsy. Of the cases 42/59 (71.2%) were proved to be malignant and 17/59 (28.8%) to be benign in the definitive histology. 2/59 (3.3%) biopsies had a false negative frozen section result. No false positive results of the intraoperative frozen section analysis were obtained, resulting in a sensitivity, specificity and positive predicting value (PPV) and negative predicting value (NPV) of 95%, 100%, 100% and 90%, respectively. Histological and morphobiological parameters did not show up relevance for correct frozen section analysis. In cases of malignancy time between diagnosis and definitive treatment could not be reduced due to frozen section analysis.</p> <p>Conclusion</p> <p>The frozen section analysis of suspect breast lesions performed by CNB displays good sensitivity/specificity characteristics. Immediate investigations of CNB is an accurate diagnostic tool and an important step in reducing psychological strain by minimizing the period of uncertainty in patients with breast tumor.</p

Education Administration in Federal Indian Law: Learning From A Colonial Project Turned Tool of Liberation

While statistics tend to focus on the difficulties facing tribal education, this article endeavors to look at the matter with fresh eyes. The federal administrative paradigm governing tribal schools has gone from a tool of cultural genocide to a mechanism for empowerment. A survey of recent governmental reforms demonstrates an embrace of the diversity of Indigenous communities, an interest in empowering students through learning, and an acknowledgement of a history of active disenfranchisement. This is ever-evolving federal-tribal relationship shows the administrative state’s capacity for dealing with greatly nuanced community needs and for tailor-making reforms to achieve concrete goals, even if those goals remain to be seen. Based off paradigms of tribal education administration, this article proposes adoption of these governance mechanism into the administration of American public schools, focusing especially on cultivating a community-empowering model that more effectively embraces the textured, diverse needs of students in different living contexts. Centrally, this article calls for us to see our current American public education governance model as disenfranchising rather than empowering and to push for change

BEAMS Lab at MIT: Status report

The Biological Engineering Accelerator Mass Spectrometry (BEAMS) Lab at the Massachusetts Institute of Technology is a facility dedicated to incorporating AMS into life sciences research. As such, it is focused exclusively on radiocarbon and tritium AMS and makes use of a particularly compact instrument of a size compatible with most laboratory space. Recent developments at the BEAMS Lab were aimed to improve different stages of the measurement process, such as the carbon sample injection interface, the simultaneous detection of tritium and hydrogen and finally, the overall operation of the system. Upgrades and results of those efforts are presented here.United States. National Institutes of Health (grant P30-ES02109)United States. National Institutes of Health (grant R42-CA084688)National Institutes of Health. National Center for Research Resources (grant UL1 RR 025005)GlaxoSmithKlin

Invariant metrics and Hamiltonian Systems

Via a non degenerate symmetric bilinear form we identify the coadjoint representation with a new representation and so we induce on the orbits a simplectic form. By considering Hamiltonian systems on the orbits we study some features of them and finally find commuting functions under the corresponding Lie-Poisson bracketComment: 16 pages corrected typos, changed contents (Prop. 3.4 and Theorem in Section 3

On The Discriminative Control Of Concurrent Responses: The Relations Among Response Frequency, Latency, And Topography In Auditory Generalization 1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96671/1/jeab.1962.5-487.pd

Reduction of quantization error in position encoders

The paper describes estimate of the quantization error of a real position encoder taking into account the factors specified above, and the method of minimization of this error by an additional adjustment of the scale is proposed. © Published under licence by IOP Publishing Ltd

Sexual and age characteristics of the parasitofauna of Abramis brama (Cypriniformes, Cyprinidae) of the Lower Irtysh (Russia)

In the present study, an evaluation was made of the dependence between infections by various types of parasites and the sex and age of the host. The parasitic community of Abramis brama includes 24 species of parasites. We assessed the degree of infestation by parasites in groups of male, female and juvenile specimens. It was established that only male bream were infested with Zschokkella nova (Klokacewa, 1914), Hysteromorpha triloba (Rudolphi, 1819), Allocreadium isoporum (Looss, 1894), Ichthyocotylurus platycephalus (Сrерlin, 1852). The ciliates of Trichodina nigra (Lom, 1960) were noted on the gills and fins of all the examined fish, the extensiveness of infection in the group of juveniles exceeded that of the groups of females and males. Specimens of Myxobolus rotundus (Nemeczek, 1911) were found on the gills and in the kidneys, and M. parviformis only on the gills of the fish. The level of infection in males was three times the EI in females and juvenile fish. The infestation on the fins by the metacercaria of Rhipidocotyle campanula (Dujardin, 1845) in male bream was more than 6 times higher than infection in females and juveniles. An increase in the extensiveness of infection in males by the nematode Philometra ovata (Zeder, 1803) was also noted in comparison with groups of females and juvenile fish. Species-specific monogeneans: Dactylogyrus falcatus (Wedl, 1857), D. wunderi (Bychowsky, 1931), D.&nbsp;zandti (Bychowsky, 1933), Gyrodactylus elegans (Nordmann, 1832); the trematodes Sphaerostomа bramae (Müller, 1776) and Diplostomum chromatophorum (Brown, 1931) infested all individuals of bream in approximately the same proportion, whereas an increase in the EI of the Caryophyllaeus laticeps (Pallas, 1781) cestode in males was observed. Infection with metacercariae Metorchis sp. in males exceeded that in females and juvenile fish. At the same time, only females and juvenile bream were infected by Chilodonella sp., metacercariae Opisthorchis felineus (Rivolta, 1884) and glochidia Unionidae gen. sp. During the studies in females, the following species of parasite were observed singly : Proteocephalus sp., Azygia lucii (Miiller, 1776), Ergasilus sieboldi (Nordmann, 1832). Parasitization by Raphidascaris acus (Bloch, 1779) was recorded only in males and juveniles, whereas in females this parasite was not observed. The dominant parasite in males was G.&nbsp;elegans, in females – the representatives of the genus Dactylogyrus, in the juvenile individuals the trematode S. bramae dominated. Analysis of the parasite fauna in various age groups allowed us to establish that at the age of 5+–6+ bream were infected by 20 species of parasites, in age group 3+–4+ there were 15&nbsp;species, at the age of 7+–8+ the fish were infected only with 11 parasitic species. The fish in all three groups were infected by T.&nbsp;nigra, Dactylogyrus spp., G. elegans, D. chromatophorum, S. bramae, R. acus almost at the same level and had no sharp differences in extensiveness and abundance of infection. Unionidae gen. sp. were observed only in group 3+–4+. Parasitization by Proteocephalus sp., metacercariae H. triloba and I. platycephalus, A. isoporum, and A. lucii was found in bream of age group 5+–6+, the species did not occur in bream at other ages. Nematode P. ovata and crustacean E. sieboldi infested the fish in age groups 3+–4+ and 5+–6+ with a slight increase in the extensiveness of infection at low abundance rates. The same age groups were observed to have decrease in the extensiveness of infection with Chilodonella sp. and metacercariae O. felineus. Myxozoan Z. nova parasitized in age group 5+–6+ and had an increase in extensiveness in age group 7+–8+. In all groups, infection was noted by representatives of the genus Myxobolus, R.&nbsp;campanula and Metorchis sp. with EI increasing with age. The obligate parasite of bream – C. laticeps infested fish the most in age group 3+–4+ in comparison with age groups 5+–6+ and 7+–8+. In the younger age group, the dactylogyruses were dominant parasites, in the age group 5+–6+ Gyrodactylus dominated, in the older age group – Metorchis sp

Group 14 Metallocene Catalysts for Carbonyl Hydroboration and Cyanosilylation

A series of six Group 14 metallocene compounds (M = Ge, Sn, Pb) were studied as catalysts for carbonyl hydroboration and cyanosilylation reactions at room temperature. Both bis(pentamethylcyclopentadienyl) and tetramethyldisiloxa[3]metallocenophane compounds were compared. The tin and lead metallocenophanes exhibited the highest reactivity in hydroboration and cyanosilylation reactions. Hammett analysis of aldehyde hydroboration provided a ρ value of 0.73, suggesting a buildup of negative charge during the turnover-limiting step, consistent with the transition state for hydride transfer to the carbonyl center. NMR studies of Lewis acidity indicate that the Ge, Sn, and Pb tetramethyldisiloxa[3]metallocenophane compounds are weak Lewis acids