Robust decoupling techniques to extend quantum coherence in diamond

We experimentally demonstrate over 2 orders of magnitude increase in the room-temperature coherence time of nitrogen-vacancy centers in diamond by implementing decoupling techniques. We show that equal pulse spacing decoupling performs just as well as nonperiodic Uhrig decoupling and also allows us to take advantage of revivals in the echo to explore the longest coherence times. At short times, we can extend the coherence of particular quantum states out from T2*=2.7 μs out to an effective T2>340 μs. For preserving arbitrary states we show the experimental importance of using pulse sequences that compensate the imperfections of individual pulses for all input states through judicious choice of the phase of the pulses. We use these compensated sequences to enhance the echo revivals and show a coherence time of over 1.6 ms in ultrapure natural abundance 13C diamond.     

Temperature effects on retention and efficiency of butyl and lauryl acrylate porous polymer monoliths in capillary electrochromatography

The development of organic porous polymer monoliths represents an alternative approach to stationary phase design. The use of these materials has helped to rekindle interest in capillary electrochromatography. Although a large number of investigations have explored different monolith recipes, polymerization conditions, and application challenges, few investigations have addressed the fundamentals of this separation mode with this type of material. This study addresses the thermodynamics of the reversed phase retention mechanism on 100% butyl acrylate and 1:3 butyl:lauryl acrylate (volume/volume ratio) porous polymer monoliths used in a capillary electrochromatography mode. Linear van't Hoff plots yield enthalpies of retention of ?3.9 to ?14.3 kJ/mol on two different, but related columns for five selected hydrophobic analytes across a thirty degree temperature range. Minimum plate heights were only moderately impacted over this temperature range.     

Magnetic polarization of Yb3+ by Cu2+ in Yb2BaCuO5

The magnetic properties of Yb³⁺ in Yb₂BaCuO₅ have been examined using¹⁷⁰Yb Mössbauer spectroscopy. The quadrupole and magnetic hyperfine parameters of the Yb³⁺ ground doublet at each of the two sites have been obtained. The Yb³⁺ magnetic polarization is due uniquely to couplings with the ordered Cu²⁺ moments.     

Comments on “vibration of a rotating beam with tip mass”

In diagnostic applications of machinery vibration or noise data it is convenient to describe the whole process by a set of numbers called discriminants. Five discriminants can be constructed and measured for every vibroacoustical process. Two of them have dimensional natures and give information about process amplitude and frequency. Two others, dimensionless, give information about the amplitude and spectral spread of the process. The last one, also dimensionless, characterizes the time fluctuations of the process, and can be used to detect instability of a running machine. Numerical and experimental examples are presented.     

On uniform distribution of sequences inGF {q,x } and [GFq,x]

Summary Analogs are proved for sequences in Φ=GF[q, x] and Φ′=GF {q, x } of results proved in 1962 by C.L. Vanden Eynden concerning uuiform distribution of sequence of integers related to sequences of real numbers. The concept of uniform distribution (mod m), m an integer, in Vanden Eynden's work is sometimes replaced here by modified forms of uniform distribution (mod M) M ∈ Φ. Supported by NSF Research Grant GP 6515. Entrata in Redazione il 13 giugno 1969.     

HomologyPlot: Searching for homology to a family of proteins using a database of unique conserved patterns

Summary A new database of conserved amino acid residues is derived from the multiple sequence alignment of over 84 families of protein sequences that have been reported in the literature. This database contains sequences of conserved hydrophobic core patterns which are probably important for structure and function, since they are conserved for most sequences in that family. This database differs from other single-motif or signature databases reported previously, since it contains multiple patterns for each family. The new database is used to align a new sequence with the conserved regions of a family. This is analogous to reports in the literature where multiple sequence alignments are used to improve a sequence alignment. A program called Homology-Plot (suitable for IBM or compatible computers) uses this database to find homology of a new sequence to a family of protein sequences. There are several advantages to using multiple patterns. First, the program correctly identifies a new sequence as a member of a known family. Second, the search of the entire database is rapid and requires less than one minute. This is similar to performing a multiple sequence alignment of a new sequence to all of the known protein family sequences. Third, the alignment of a new sequence to family members is reliable and can reproduce the alignment of conserved regions already described in the literature. The speed and efficiency of this method is enhanced, since there is no need to score for insertions or deletions as is done in the more commonly used sequence alignment methods. In this method only the patterns are aligned. HomologyPlot also provides general information on each family, as well as a listing of patterns in a family.     

Dehalogenation of α -haloketones and vic-dibromides with nickel boride

α-Haloketones and $\text{vic}$-dibromides are converted to the corresponding ketones and alkenes respectively with nickel boride generated $\text{in situ}$ from sodium borohydride and nickel chloride.     

Spin dynamics in RENi5 ferromagnets byμSR measurements

We report a zero fieldSR study of single crystals of theRENi ₅ ferromagnets where RE=Gd, Er, Dy or Tm. Our work points out the strong influence of the crystal electric field on the rare earth total momentum dynamics: whereas the spin-lattice relaxation process belowT _c is controlled by a two magnon mechanism for a weakly anisotropic magnet (GdNi ₅), the phonons drive the relaxation for a strongly anisotropic magnet such asErNi ₅. ForTmNi ₅ a comparison is made between the fluctuation time measured bySR and¹⁶⁹ Tm Mössbauer spectroscopy.