Large Collective Lamb Shift of Two Distant Superconducting Artificial Atoms.

Virtual photons can mediate interaction between atoms, resulting in an energy shift known as a collective Lamb shift. Observing the collective Lamb shift is challenging, since it can be obscured by radiative decay and direct atom-atom interactions. Here, we place two superconducting qubits in a transmission line terminated by a mirror, which suppresses decay. We measure a collective Lamb shift reaching 0.8% of the qubit transition frequency and twice the transition linewidth. We also show that the qubits can interact via the transmission line even if one of them does not decay into it.

Quantitative elemental analysis of steel using calibration-free laser-induced breakdown spectroscopy.

We report the quantitative elemental analysis of a steel sample using calibration-free laser-induced breakdown spectroscopy (CF-LIBS). A Q-switched Nd:YAG laser (532 nm wavelength) is used to produce a plasma by focusing it onto a steel sample in air at atmospheric pressure. The time-resolved spectra from atomic and ionic emission lines of the steel elements are recorded by an echelle grating spectrograph coupled with a gated intensified CCD camera and are used for the plasma characterization and quantitative analysis of the sample. The time delay at which the plasma is in local thermodynamic equilibrium as well as optically thin, necessary for elemental analysis, is deduced. An algorithm for the CF-LIBS relating the experimentally measured spectral intensity values with the basic physics of the plasma is developed and used for the determination of Fe, Cr, Ni, Mg, and Si concentrations in the steel sample. The analytical results obtained from the CF-LIBS technique agree well with the certified values of the elements in the sample, with relative uncertainties of less than 5%.

Decoupling a Cooper-pair box to enhance the lifetime to 0.2 ms.

We present results on a circuit QED experiment in which a separate transmission line is used to address a quasilumped element superconducting microwave resonator which is in turn coupled to an Al/AlO(x)/Al Cooper-pair box charge qubit. With our device, we find a strong correlation between the lifetime of the qubit and the inverse of the coupling between the qubit and the transmission line. At the smallest coupling we measured, the lifetime of the Cooper-pair box was T1=200 µs, which represents more than a twentyfold improvement in the lifetime of the Cooper-pair box compared with previous results. These results imply that the loss tangent in the AlO(x) junction barrier must be less than about 4×10⁻8 at 4.5 GHz, about 4 orders of magnitude less than reported in larger area Al/AlO(x)/Al tunnel junctions.

EcoA: the first member of a new family of type I restriction modification systems. Gene organization and enzymatic activities.

The characterization of the EcoA restriction-modification enzymes from Escherichia coli 15T- is described. The reactions catalysed by these enzymes are very similar to those catalysed by the classical type I restriction and modification enzymes, a family of genetically related proteins. The detailed mechanisms, particularly for DNA modification, differ. The genetic and transcriptional organizations are also very similar to those of the classical systems, despite the fact that EcoA is not allelic to the others. We demonstrate that the expression of the EcoA genes is controlled following conjugative transfer to other strains in such a way that no lethality is observed, probably because the recipient chromosome is completely modified before restriction activity is expressed.

Type III DNA restriction and modification systems EcoP1 and EcoP15. Nucleotide sequence of the EcoP1 operon, the EcoP15 mod gene and some EcoP1 mod mutants.

This paper presents the nucleotide sequence of the mod-res operon of phage P1, which encodes the two structural genes for the EcoP1 type III restriction and modification system. We have also sequenced the mod gene of the allelic EcoP15 system. The mod gene product is responsible for binding the system-specific DNA recognition sequences in both restriction and modification; it also catalyses the modification reaction. A comparison of the two mod gene product sequences shows that they have conserved amino and carboxyl ends but have completely different sequences in the middle of the molecules. Two alleles of the EcoP1 mod gene that are defective in modification but not in restriction were also sequenced. The mutations in both alleles lie within the non-conserved regions.

The use of heparin-sepharose affinity chromatography to separate two distinct lipoproteins from the low density lipoprotein fraction of rat plasma.

Heparin-Sepharose affinity chromatography resolved rat lipoproteins isolated in the density range 1.019-1.063 g/ml into two distinct fractions. The first, which eluted with 150 mM NaCl, was shown by immunodiffusion and by polyacrylamide gel electrophoresis to contain predominantly apo E. On this basis the major lipoprotein present is identified as high density lipoprotein1 (HDL1). The second, eluted with 325 mM NaCl, contains predominantly apoprotein B by the same techniques. The main lipoprotein present is therefore identified as low density lipoprotein (LDL). The lipid composition of the two lipoproteins is similar. Both are rich in cholesterol ester, with a free to ester cholesterol ratio of about 1 to 2.5. From lipid and protein analyses on the two fractions, the plasma concentrations of HDL1 and LDL can be calculated to be about 14 and 12 mg/100 ml, respectively. Their mean diameters are 13 +/- 2 nm and 18 +/- 5 nm, respectively.

Hormonal influences on women with psoriasis.

Various endogenous factors such as stress and infection are known to influence psoriasis. Previous data suggest that pregnancy has a significant influence on the course of psoriasis. This study explores the effect of pregnancy as well as other hormonal events on psoriasis in women.

The metabolic conversion of very-low-density lipoprotein into low-density lipoprotein by the extrahepatic tissues of the rat.

1. The work reported was designed to provide quantitative information about the capacity of the extrahepatic tissues of the rat to degrade injected VLD lipoproteins (very-low-density lipoproteins, d less than 1.006) to LD lipoproteins (low-density lipoproteins, d 1.006--1.063) and to study the fate of the different VLD-lipoprotein apoproteins during the degradative process. 2. Rat liver VLD lipoproteins, radioactively labelled in their protein moieties, were produced by the perfusion of the organ and were either injected into the circulation of the supradiaphragmatic rats or incubated in rat plasma at 37 degrees C. At a time (75 min) when approx. 90% of the triacylglycerol of the VLD lipoproteins had been hydrolysed the supradiaphragmatic rats were bled and VLD lipoproteins, LD lipoproteins and HD lipoproteins (high-density lipoproteins, d 1.063--1.21) were separated from their plasma and from the plasma incubated in vitro. The apoproteins of each of the lipoprotein classes were resolved by gel-filtration chromatography into three main fractions, designated peaks I, II and III. 3. Incubation of the liver VLD lipoproteins in plasma in vitro led to the transfer of about 30% of the total protein radioactivity to the HD lipoproteins. The transfer mainly involved the peak-II (arginine-rich and/or apo A-I) and peak-III (apo C) proteins. There was also a small transfer of radioactivity (about 5% of the total) to the LD lipoproteins. 4. Injection of the liver VLD lipoproteins into the circulation of the supradiaphragmatic rat resulted in the transfer of about 15% of the total VLD-lipoprotein radioactivity to the LD lipoproteins. The transfer involved mainly the peak-I (apo B) proteins and accounted for about 20% of the total apo B protein radioactivity of the injected VLD lipoproteins. When the endogenous plasma VLD lipoprotein was taken into account the transfer of apo B protein was about 35%. 5. The transfer of peak-II protein radioactivity from the VLD to the HD lipoproteins was greater in the plasma of the supradiaphragmatic rat than in the incubated plasma suggesting that there was a net transfer of peak-II apoproteins during the VLD lipoprotein degradation. The transfer of peak-III protein radioactivity was not greater in the plasma of the supradiaphragmatic rat, but there was a loss of this radioactivity from the circulation.

The EcoA restriction and modification system of Escherichia coli 15T-: enzyme structure and DNA recognition sequence.

The EcoA restriction enzyme from Escherichia coli 15T- has been isolated. It proves to be an unusual enzyme, clearly related functionally to the classical type I restriction enzymes. The basic enzyme is a two subunit modification methylase. Another protein species can be purified which by itself has no enzymatic activities but which converts the modification methylase to an ATP and S-adenosylmethionine-dependent restriction endonuclease. The DNA recognition sequence of EcoA has an overall structure that is very similar to previously determined type I sequences. It is: 5'-GAGNNNNNNNGTCA-3' 3'-CTCNNNNNNNCAGT-5' where N can be any nucleotide. Modification methylates the adenosyl residue in the specific trinucleotide and the adenosyl residue in the lower strand of the specific tetranucleotide.

The removal of partially metabolized very-low-density lipoproteins by the perfused rat liver.

1. Donor perfused rat livers were used to prepare VLD (very-low-density) lipoproteins, labelled in their triacylglycerol and protein components with [1-14C]oleic acid and L-[4,5-3H]leucine respectively. Partially metabolized VLD lipoproteins, similarly labelled, were obtained from supradiaphragmatic rats injected with the parent VLD lipoproteins. 2. The triacylglycerol and protein components of the partially metabolized VLD lipoproteins were removed by recipient perfused rat livers at rates much higher than those of the parent VLD lipoproteins. No degradation of the partially metabolized VLD lipoproteins to LD (low-density) lipoproteins occurred during the perfusions. 3. Removal of hepatic lipase from the livers did not significantly affect the rate of removal of the partially metabolized VLD lipoproteins.

Structural homologies among type I restriction-modification systems.

Structural homologies among different restriction systems of Escherichia coli and several Salmonella species have been investigated by immunological methods using antibodies prepared against two subunits of the E. coli K12 restriction enzyme, and by DNA hybridization experiments using different fragments of the E. coli K12 hsd genes as probes. The results with both techniques show a strong homology between the E. coli K12 and B restriction-modification systems, weaker but nevertheless marked homology between E. coli K12 and the Salmonella systems SB, SP, and SQ and, surprisingly, no homology between the E. coli K12 and A systems.

Variacin, a new lanthionine-containing bacteriocin produced by Micrococcus varians: comparison to lacticin 481 of Lactococcus lactis.

A new lanthionine-containing bacteriocin, variacin, displaying a broad host range of inhibition against gram-positive food spoilage bacteria, has been identified from two strains of Micrococcus varians isolated from meat fermentations. The new bacteriocin was purified, and its amino-terminal end and total amino acid composition were determined. The structural gene was isolated and analyzed. Variacin is resistant to heat and pH conditions from 2 to 10. Its primary sequence shows significant homology to lacticin 481 to Lactococcus lactis, which is more pronounced for the probacteriocin than for the leader sequence. Variacin, like lacticin 481, contains lanthionine and beta-methyllanthionine residues, but its leader sequence clearly resembles nonlantibiotic leader sequences. In particular, the prepeptide contains glycine residues at positions -1 and -2 of the processing site.