A Simple Polarimetry Technique for Predicting the Absolute Configuration of the Preferred Enantiomer in Chiral Host-Guest Inclusion Complexes

Amethod for predicting the configuration of the preferred guest enantiomer in an inclusion complex with an optically pure host compound was developed. The method involves simply measuring the optical rotation of the host-guest inclusion complex as a whole, by means of polarimetry, and using this value in a calculation in order to obtain information about the guest configuration. The availability of standard optically pure guest materials is not required, nor is the isolation of the guest species from the hostcrystal, resulting in an attractive, inexpensive, rapid and simple procedure for this purpose.(Graphical Abstract)KEYWORDS Host-guest chemistry, polarimetry, optical rotation, supramolecular chemistry, inclusion chemistry

Minimum and maximum against k lies

A neat 1972 result of Pohl asserts that [3n/2]-2 comparisons are sufficient, and also necessary in the worst case, for finding both the minimum and the maximum of an n-element totally ordered set. The set is accessed via an oracle for pairwise comparisons. More recently, the problem has been studied in the context of the Renyi-Ulam liar games, where the oracle may give up to k false answers. For large k, an upper bound due to Aigner shows that (k+O(\sqrt{k}))n comparisons suffice. We improve on this by providing an algorithm with at most (k+1+C)n+O(k^3) comparisons for some constant C. The known lower bounds are of the form (k+1+c_k)n-D, for some constant D, where c_0=0.5, c_1=23/32=0.71875, and c_k=\Omega(2^{-5k/4}) as k goes to infinity.Comment: 11 pages, 3 figure

Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 2: Advanced energy conversion systems. Part 3: Direct energy conversion cycles

For abstract, see N76-23680

A W:B4C multilayer phase retarder for broadband polarization analysis of soft x-ray radiation \ud

A W:B4C multilayer phase retarder has been designed and characterized which shows a nearly constant phase retardance between 640 and 850 eV photon energies when operated near the Bragg condition. This freestanding transmission multilayer was used successfully to determine, for the first time, the full polarization vector at soft x-ray energies above 600 eV, which was not possible before due to the lack of suitable optical elements. Thus, quantitative polarimetry is now possible at the 2p edges of the magnetic substances Fe, Co, and Ni for the benefit of magnetic circular dichroism spectroscopy employing circularly polarized synchrotron radiatio

Analyzing a Bose polaron across resonant interactions

Recently, two independent experiments reported the observation of long-lived polarons in a Bose-Einstein condensate, providing an excellent setting to study the generic scenario of a mobile impurity interacting with a quantum reservoir. Here, we expand the experimental analysis by disentangling the effects of trap inhomogeneities and the many-body continuum in one of these experiments. This makes it possible to extract the energy of the polaron at a well-defined density as a function of the interaction strength. Comparisons with quantum Monte-Carlo as well as diagrammatic calculations show good agreement, and provide a more detailed picture of the polaron properties at stronger interactions than previously possible. Moreover, we develop a semi-classical theory for the motional dynamics and three-body loss of the polarons, which partly explains a previously unresolved discrepancy between theory and experimental observations for repulsive interactions. Finally, we utilize quantum Monte-Carlo calculations to demonstrate that the findings reported in the two experiments are consistent with each other

Influence of the Madden–Julian Oscillation on Southern African Summer Rainfall

Composite maps of outgoing longwave radiation (OLR) anomalies over the Madden-Julian oscillation (MJO) cycle show marked intraseasonal fluctuations over southern Africa (south of 15°S). Large-scale convective clusters are seen to propagate eastward and then northward over the continent, mainly between 10° and 20°S. The corresponding response of the rainfall field presents the alternation, over the cycle, of dry and humid phases, which are both significant. Moisture flux anomalies indicate an intraseasonal modulation of the midtropospheric easterly flow over the Congo basin at 700 hPa; these fluctuations are coupled to meridional flux anomalies that extend from the tropical to the subtropical austral latitudes, and favor occurrences of wet or dry conditions over the domain. Though statistically significant, the influence of the MJO on southern Africa is however not homogeneous spatially, and only the tropical areas exhibit sharp periodicities in the 30-60-day period range. The OLR dipole observed in previous studies at the interannual and synoptic time scales between the hinterland parts of southern Africa and the southwestern Indian Ocean in the north of Madagascar is investigated next, as it also shows strong fluctuations at the intraseasonal time scale. The study points out that the dipole is partly influenced by the MJO, though the strongest periodicities are found for slightly longer periods (35-80 days) than those typically associated with the oscillation. The forcing of the MJO on the OLR dipole, though significant, remains thus partial

Ureteroscopic and Scanning Electron Microscopical Findings in Ureteral Anastomoses After Segment Resection

In an experimental study on 8 canine ureters, end-to-end anastomoses were performed after segmental resection between 9 and 13 cm, using two different surgical techniques. After 3 months of observation the three-dimensional structure of the anastomosis and the surrounding areas was investigated by ureteroscopy and scanning electron microscopy. 3 types could be differentiated by the morphologic features of the ureteral lumen: normal width, segmental stricture, and circumferential stricture. The results offer a plausible explanation for the occasional discrepancy between histologic findings of relatively normal lumen width, and functional disorders apparently reflecting ureteral stenosis. They further support that excellent functional and morphologic reconstruction can be achieved even under the extreme conditions of 13 cm segmental resection with obligatory anastomosis under tension. The findings connected with dilatations observed distal to the anastomotic site appear rather contradictory, their interpretation is difficult

Urolithiasis in a Patient Ingesting Pure Silica: A Scanning Electron Microscopy Study

A patient who repeatedly produced urinary calculi, had consumed about 3g of cristobalite (SiO2) per day for many years. Investigations using scanning electron microscopy revealed minute particles containing silicon in the core of the stone as well as in urine sediment. A mechanism similar to that proposed for the effect of silicon-containing drugs against gastric ulcer, may play a role in this formation of silicon-containing urinary stones