Compounds in the pyrrolo[3,4-d]pyrimidine series. derivatives with 6-aryl substituents

Methods are described for the synthesis of 6,7-dihydro-5H-pyrrolo[3,4-d]pyrimidines having an aryl substituent in the 6-position. 4-Hydroxy-, 4-amino, 2-amino-4-hydroxy and 2,4-diamino derivatives were obtained. The synthetic route involved the preparation of 1-aryl-4-cyano- or 4-carboalkoxy-3-pyrrolidinones and 1-aryl-4-cyano- or 4-carboalkoxy-3-amino-3-pyrrolines as key intermediates.     

Mechanical resonance dispersion in polytetrafluorethylene rods in transverse vibration

Summary Polytetrafluorethylene rods in transverse vibration exhibit sharp non-harmonic resonances when subjected to a static tensile stress during vibration. The extent and location of the resonances are critically dependent on the exact static stress state and history of the rods. Rods under no external tension have no anomalous behavior in the range 100 to 2000 cps, but under static tension varying from 1.5×10⁵ to 3.0×10⁶ dynes/cm² (2.2 to 44 psi) sharp resonances appear in the vicinity of 400 cps. The mechanical resonance dispersions in complex shear compliance previously reported byFitzgerald are thus substantiated by the present work. The failure of certain other investigators to observe the dispersion in polytetrafluorethylene is attributed to the fact that insufficient attention was paid to the static stress conditions in their tests.

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Zusammenfassung Polytetrafluor?thylen-Streifen zeigen bei transversaler Schwingung scharfe nicht-harmonische Resonanzen, wenn sie w?hrend der Vibration einem statischen Zug unterworfen sind. Intensit?t und Lage der Resonanzen h?ngen kritisch vom statischen Spannungszustand und der Geschichte der Proben ab. Proben unter keiner ?u?eren Spannung zeigen im Bereich von 100–200 Hz kein anomales Benehmen, doch erscheinen bei statischer Belastung zwischen 1,5×10⁵ zu 3,0×10⁶ dyn/cm² scharfe Resonanzen in der N?he von 400 Hz. Die mechanische Resonanzdispersion der komplexen Scherungsnachgiebigkeit, früher vonFitzgerald mitgeteilt, werden mit der vorliegenden Arbeit best?tigt. Da? anderen Bearbeitern die Beobachtung der Dispersion bei Polytetrafluor?thylen mi?lungen ist, ist der Tatsache zuzuschreiben, da? den statischen Spannungszust?nden in ihren Proben ungenügende Rechnung zuteil wurde.

     

On the lock-in phase transformation in thiourea

Elastic neutron scattering experiments show clear evidence for the lock-in wave vector being $\text{b}{}^{\mathrm{<mtext>x</mtext><mtext>9</mtext>}}$ in thiourea. A commensurate 9b superstructure is stabilized in the 2 K range just above the ferroelectric transition. A global hysteresis on the wave vector variation is also observed.     

Sun's conjectures on fourth powers in the class group of binary quadratic forms

Text

We prove five of Sun's conjectures on the index of the subgroup of fourth powers in the class group of binary quadratic forms.

Video

For a video summary of this paper, please visit http://www.youtube.com/watch?v=jMuO4RAp1Xw.     

Automated analysis of the architecture of receptors, imaged by atomic force microscopy

Fast neurotransmission involves the operation of ionotropic receptors, which are multi-subunit proteins that respond to activation by opening an integral ion channel. Examples of such channels include the GABA(A) receptor, the 5-HT(3) receptor and the P2X receptor for ATP. These receptors contain more than one type of subunit, although the exact subunit stoichiometry and arrangement around the receptor rosette is often unknown. We are using atomic force microscopy (AFM) of purified receptors to address these issues. Measurement of the molecular volume of the receptor permits the determination of the number of subunits that it contains. Furthermore, analysis of the geometry of complexes between receptors and subunit-specific antibodies reveals the subunit arrangement. Our AFM-based approach has so far been dependent on manual data processing, which is both time-consuming and prone to operator bias. In this study, we set out to develop a novel method capable of automatic segmentation and quantitative analysis of both single receptor particles and receptor-antibody complexes. The method was validated using images of wild type and mutant forms of the P2X(6) receptor. We suggest that the automated method will greatly facilitate further progress in the use of AFM for the determination of receptor and multi-protein architecture.     

Propagation of S-polarized surface polaritons circumferentially around a locally cylindrical surface

The dispersion relation is derived and solved for s-polarized surface polaritons propagating circumferentially around a portion of a cylindrical interface between vacuum and an isotropic dielectric. In the case that the dielectric is convex toward the vacuum these modes are found to be radiative, and consequently are attenuated as they propagate on the cylindrical surface. When the dielectric is concave toward the vacuum the resulting surface polaritons are nonradiative and propagate unattenuated on the cylinder. Such modes do not exist in the case of a planar interface between a homogeneous isotropic dielectric and vacuum.     

Design and fabrication of subwavelength nanogratings based light-emitting diodes

Linearly polarized light from InGaN green light emitting diode grown on (0001) oriented sapphire is demonstrated by using subwavelength metallic nanogratings. Polarization ratio can reach 7:1 (∼88%), the highest ever reported from a single light emitting device. We discuss the design and fabrication of this device in detail.     

‘Good enough’ performance measurement: a trade-off between activity and action

Performance measurement systems along the lines of the EFQM and the balanced scorecard have developed rapidly in recent years, and now occupy much management time and effort. There is limited evidence that performance improvement has received proportionate attention. Six organisations selected for their success were studied using a grounded theory approach based on interviews with management accountants and operations managers in each of the organisations. It is clear that they are all making strenuous efforts to use their performance measurement systems but with a focus on the ‘good enough’ rather than the detail. This gave managers in these organisations the time and space to concentrate on the use of performance measures on forward looking relevance, understanding and action, rather than retrospective and detailed control. This approach was promoted by senior managers and was based on their ability to see the business in simple terms and their understanding of the key drivers of business performance.     

-regular Witt rings

We improve Kula's bounds on the size of possible -regular Witt rings.

     

The Challenge of Functional Magnetic Resonance Imaging

Abstract

Functional magnetic resonance imaging of the human brain in action presents large statistical and computational challenges. Here we describe those challenges and provide references to a number of other papers where detailed methods developed to meet them are reported. The first seven sections of this paper were written in 1995 when our work was in its infancy. The last four sections were written more recently, to update the earlier sections and to show the directions we have gone and the directions we intend to go.