Steps towards a practical synthesis of macrocyclic bisbenzylisoquinolines

There are more than 400‐reported bisbenzylisoquinoline alkaloids, many with interesting biological activity, but the reported syntheses are long and low yielding. As a result, there have been no systematic attempts at exploitation of the potential therapeutic applications. The concept of a sulfur ‘stitch’, restricting the conformational freedom of intermediates in the synthesis, will potentially allow analogues of the natural products to be prepared using relatively efficient routes. The synthesis of intermediate sulfur heterocycles is reported, based on 2,8‐dimethylphenoxathiin, leading via 2,8‐bis(bromomethyl)phenoxathiin‐10,10‐dioxide to a synthesis of 3,4,8,9‐tetrahydro‐13‐oxa‐6‐thia‐2,10‐diazapentacene, a key potential intermediate on the route to a variety of macrocyclic bisbenzylisoquinolines.     

C-terminal processing of yeast Spt7 occurs in the absence of functional SAGA complex

Background  

Spt7 is an integral component of the multi-subunit SAGA complex that is required for the expression of ~10% of yeast genes. Two forms of Spt7 have been identified, the second of which is truncated at its C-terminus and found in the SAGA-like (SLIK) complex.     

Can Gravitons be Detected?

Freeman Dyson has questioned whether any conceivable experiment in the real universe can detect a single graviton. If not, is it meaningful to talk about gravitons as physical entities? We attempt to answer Dyson’s question and find it is possible concoct an idealized thought experiment capable of detecting one graviton; however, when anything remotely resembling realistic physics is taken into account, detection becomes impossible, indicating that Dyson’s conjecture is very likely true. We also point out several mistakes in the literature dealing with graviton detection and production.     

Direct synthesis of trimethyl(2-phenoxyethyl)silanes from aromatic fluorides

A direct synthesis of trimethyl(2-phenoxyethyl)silanes from the corresponding aromatic fluorides and 2-(trimethylsilyl)ethanol was developed. A variety of substituents were tolerated and a substitution reaction using 1-bromo-3-chloro-5-fluorobenzene was demonstrated.     

What Children Bring to the Classroom: Learning Science From Experience

Extracurricular science-related experiences of young students were examined. The sample consisted of 539 elementary school students between the ages of 9 and 13. Students completed the Science Experiences Survey (SES) to identify the number of common scientific materials and activities they experienced outside of the classroom. The factor analysis isolated three underlying factors of extracurricular science-related experiences: life science-related experiences, physical science-related experiences, and general learning attributes related to science. Further analysis identified differences in reported experiences by gender. The data indicate that young girls tend to participate in nurturing life science-related activities, and young boys favor hands-on, action-oriented physical science-related experiences. The research suggests that the gender disparity in science follows a continuuum that begins with the experiences of elementary school students.     

Cyclic subsemigroups of symmetric inverse semigroups

A generalization of the cycle notation for permutations is introduced for partial one-one transformations (charts). Notational representation theorems for charts that generalize those of permutations are given. Notational multiplication of charts is developed and then applied to yield a transparent proof of Frobenius' result which bounds the idempotent in the cyclic subsemigroup. Lastly, the well known result that the structure of the cyclic subgroups of the finite symmetric groups is determined from combinations of disjoint cycles is generalized to the cyclic subsemigroups of the finite symmetric inverse semigroups.     

Some Penrose transforms in complex differential geometry

In this article, we review a construction in the complex geometry often known as the Penrose transform. We then present two new applications of this transform. One concerns the construction of symmetries of the massless field equations from mathematical physics. The other concerns obstructions to the embedding of CR structures on the three-sphere. Dedicated to Professor Sheng GONG on the occasion of his 75th birthday     

Development of a micromachined piezoelectric microphone for aeroacoustics applications

This paper describes the design, fabrication, and characterization of a bulk-micromachined piezoelectric microphone for aeroacoustic applications. Microphone design was accomplished through a combination of piezoelectric composite plate theory and lumped element modeling. The device consists of a 1.80-mm-diam, 3-microm-thick, silicon diaphragm with a 267-nm-thick ring of piezoelectric material placed near the boundary of the diaphragm to maximize sensitivity. The microphone was fabricated by combining a sol-gel lead zirconate-titanate deposition process on a silicon-on-insulator wafer with deep-reactive ion etching for the diaphragm release. Experimental characterization indicates a sensitivity of 1.66 microVPa, dynamic range greater than six orders of magnitude (35.7-169 dB, re 20 microPa), a capacitance of 10.8 nF, and a resonant frequency of 59.0 kHz.