In Escherichia coli, the let locus at min 80 on the chromosome map is associated with ability to grow on L-lactate and to synthesize a substrate-inducible flavin-linked dehydrogenase. Similar to that of the glpD-encoded aerobic glycerol-3-phosphate dehydrogenase, the level of induced enzyme activity is elevated by aerobiosis. Both of these controls are mediated by the two-component signal transduction system ArcB/ArcA, although sensitivity to the control is much more striking for L-lactate dehydrogenase. This study disclosed that the kct locus contained three overlapping genes in the clockwise order of lktD (encoding a flavin mononucleotide-dependent dehydrogenase), IctR (encoding a putative regulator), and kctP (encoding a permease) on the chromosomal map. These genes, however, are transcribed in the counterclockwise direction. No homology in amino acid sequence was found between aerobic glycerol-3-phosphate dehydrogenase and L-lactate dehydrogenase. A F(kctD-lac) mutant was inducible by L-lactate but not D-lactate. Although the mutant lost the ability to grow on L-lactate, growth on D-lactate, known to depend on a different enzyme, remained normal.Growth of Escherichia coli on L-lactate results in the induction of a flavin-linked L-lactate dehydrogenase (9,13,29), and this trait is associated with the Ict locus at min 80.8 on the chromosome map (3,19,31 Bacterial strains, phages, and plasmids. All strains used were E. coli K-12 derivatives. The genotypes and sources of the bacterial strains, phages, and plasmids are given in Table 1.Growth conditions. Overnight cultures were grown in LB medium (28). Minimal agar media (38) were supplemented with thiamine. When used, the following compounds were added to the media at the following concentrations unless otherwise specified: D-or L-lactate, 20 mM; D-xylose, 10 mM; CAA, 1%; thiamine, 2 ug/ml; kanamycin (kan), 40 ,ug/ml; and ampicillin, 100 ,ug/ml. Mannitol (1%)-MacConkey agar plates were used for screening the inheritance of the mtl allele.Cultures for enzyme and permease assays were grown in 300-ml flasks containing 10 ml of MOPS (0.1 M) mineral medium at pH 7.6 with appropriate supplements (15). Ample aeration was ensured by vigorous agitation, and cells were harvested when growth reached the mid-exponential phase.Enzyme and permease assays. For L-and D-lactate dehydrogenase assays, cells were harvested by centrifugation at 5,000 x g for 15 min and washed once in cold 10 mM potassium phosphate buffer (pH 7.0). The pellet was weighed and suspended in 4 volumes of the same buffer. The suspended cells were lysed for 1 min/ml in a model 60 W ultrasonic disintegrator (MSE) at 1.5 A while being chilled in a dry ice-ethanol bath. Lysates were cleared by centrifugation for 30 min at 10,000 x g. Enzyme assays were performed in a manner similar to that for glycerol-3-phosphate dehydrogenase by measuring the reduction of 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyl-tetrazolium bromide mediated by phenazine methosulfate (20)

The proton radioactivity half-lives of spherical proton emitters are investigated theoretically. The potential barriers preventing the emission of proton are determined in the quasimolecular shape path within a generalized liquid drop model (GLDM) including the proximity effects between nuclei in a neck and the mass and charge asymmetry. The penetrability is calculated in the WKB approximation. The spectroscopic factor has been taken into account in half-life calculation, which is obtained by employing the relativistic mean field (RMF) theory combined with the BCS method with the force NL3. The half-lives within the GLDM are compared with the experimental data and other theoretical values. GLDM works quite well for spherical proton emitters when the spectroscopic factors are considered, indicating the necessity of introducing the spectroscopic factor and the success of the GLDM for proton emission. Finally, we present two formulae for proton emission half-life similar to the Viola-Seaborg formulae and Royer's formulae of α-decay.

Three global regulatory systems, Fnr, NarX/NarL, and ArcB/ArcA, control expression of operons encoding enzymes involved in respiration and fermentation in Escherichia coli (10,25,28,36,38). In general, Fnr anaerobically activates expression of numerous operons involved in fermentation and anaerobic respiration, such as those that encode nitrate, fumarate, and TMAO (trimethylamine N-oxide) reductases. An N-terminal cysteine cluster is known to be the key sensing element of Fnr, although the identity of the signal(s) remains to be established (9,37,43). NarX/NarL belongs to a family of two-component regulatory systems (11,30,41). Upon stimulation by nitrate, the sensor undergoes autophosphorylation and becomes a protein kinase for its cognate regulator, NarL (10,34,38,46). Phosphorylated NarL (NarL-P) is thought to activate critical operons for nitrate respiration, narGHJI (encoding the major nitrate reductase) and fdhGHI (encoding formate dehydrogenase N) (1). In contrast, NarL-P is thought to repress other operons for anaerobic respirations involving electron acceptors with standard oxidation-reduction potentials lower than that of nitrate, i.e., those that are less effective in metabolic energy generation. These operons include frdABCD, encoding fumarate reductase, and dmsABC, encoding dimethyl sulfoxide reductase (10,22,38). The differential behavior of the NarX/ NarL system toward its targets thus allows the cell to carry out the most profitable mode of anaerobic respiration.ArcB/ArcA is another two-component regulatory system. ArcB is the membrane sensor comprising both a transmitter domain and a receiver domain, and ArcA is the cognate regulator. Some metabolites (notably pyruvate, D-lactate, ace-* Corresponding author. Mailing address:

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In 2014, Indo-Pacific humpback dolphins were recorded for the first time in waters southwest of Hainan Island, China. In this paper, the temporal occurrence of Indo-Pacific humpback dolphins in this region was detected by stationary passive acoustic monitoring. During the 130-day observation period (from January to July 2016), 1969 click trains produced by Indo-Pacific humpback dolphins were identified, and 262 ten-minute recording bins contained echolocation click trains of dolphins, of which 70.9% were at night and 29.1% were during the day. A diurnal rhythm with a nighttime peak in acoustic detections was found. Passive acoustic detections indicated that the Indo-Pacific humpback dolphins frequently occurred in this area and were detected mainly at night. This information may be relevant to conservation efforts for these dolphins in the near future.

Branching ratios of α decay to members of the ground state rotational band and excited 0 + states of even-even nuclei are calculated in the framework of the generalized liquid drop model (GLDM) by taking into account the angular momentum of the α particle and the excitation probability of the daughter nucleus. The calculation covers isotopic chains from Hg to Fm in the mass regions 180 < A < 202 and A 224. The calculated branching ratios of the α transitions are in good agreement with the experimental data and some useful predictions are provided for future experiments.

Tensor effects on the N = 40 gap evolution of N = 40 isotones are studied by employing the SkyrmeHartree-Fock-Bogoliubov (SHFB) and relativistic Hartree-Fock-Bogoliubov (RHFB) theories. The results with and without the inclusion of the tensor components are compared with each other. It is found that when the tensor force is included, both two different approaches present the same trend and qualitatively agree with the experimental one indicated by the β-decay studies, which implies an important role played by the tensor force in the gap evolution of N = 40. Furthermore, it is shown that the gap evolution is dominated by the corresponding tensor contributions from π and ρ-tensor coupling in the relativistic framework. With worldwide development of Radioactive Ion Beam (RIB) facilities, the nuclei far from the valley of β-stability, namely the exotic nuclei, have become more accessible in recent years [1]. The investigations on the shell structures of such nuclei have formed a new frontier in modern nuclear physics due to some novel phenomena discovered timely. The typical examples are the emergence of some new magic numbers [2,3] and the quenching of some conventional shell closures [2, 4, 5] when approaching the isospin limits of the realistic nuclei. As suggested by Otsuka and the collaborators, the tensor force may be one of the crucial physical mechanisms in modeling the shell evolution and the occurrence of magic numbers in the exotic regions [6][7][8]. However, in both non-relativistic and relativistic self-consistent mean-field calculations, the relevant tensor components were dropped up to very recently [9][10][11][12][13][14].Since the magic character of 68 Ni was proposed in the early eighties by Bernas et al. [15], the subshell closure of N = 40 has been devoted more and more efforts from both experimental and theoretical sides due to the significant roles played by the nuclei of N = 40 ∼ 60 in the r-and rp-process paths [16]. In the shell-model picture, the gap of N = 40 is determined by the negative parity f p (2p 1/2 and 1 f 5/2 ) and positive parity 1g 9/2 orbits. Thus, the low-lying structure of 68 Ni might be concerned with the change of parity [17]. On the other hand, due to the opposite tensor effects felt by the 1 f 5/2 (or 2p 1/2 ) and 1g 9/2 states, the tensor force is also expected to play an important role in figuring the N = 40 gap evolution since most of the N = 40 isotones are spin-unsaturated for proton [6,18]. Recently several experiments of β-decay indicate a rapidly weakening of N = 40 gap when removing protons from 68 Ni [19,20], whereas such feature cannot be properly described by the mean-field calculations when the tensor components of the nuclear interaction are excluded [21,22].In this Brief Report, the gap evolution of N = 40 will be explored within the non-relativistic and relativistic mean field theories, specifically the non-relativistic Skyrme-HartreeFock-Bogoliubov (SHFB) [23], the relativistic HartreeBogoliubov (RHB) [24,25], and relativistic Hartree-FockBogoliubov (RHF...

Half-life of proton radioactivity of spherical proton emitters is studied within the scheme of covariant density functional (CDF) theory, and for the first time the potential barrier that prevents the emitted proton is extracted with the similarity renormalization group (SRG) method, in which the spin-orbit potential along with the others that turn out to be non-negligible can be derived automatically. The spectroscopic factor that is significant is also extracted from the CDF calculations. The estimated half-lives are found in good agreement with the experimental values, which not only confirms the validity of the CDF theory in describing the proton-rich nuclei, but also indicates the prediction power of present approach to calculate the half-lives and in turn to extract the structural information of proton emitters. With continuous development of the radioactive ion beam facilities, the exotic nuclei far away from the β-stability line attract extensive interests for the new phenomena they present. One of the typical representatives is the proton radioactivity at the vicinity of proton drip line, firstly observed in an isomeric state of 53 Co in 1970 [1, 2]. Since then more and more proton emitters ranging from Z = 51 to 83 have been identified with nuclear ground states or isomeric states [3]. Essentially, it is significant to study the proton emission which corresponds to the fundamental existence limits of neutron-deficient nuclei, i.e., the proton drip line, and it also can be treated as the inverse reaction of the rapid proton capture process that plays an important role in understanding the origin of the elements in the universe [4]. Moreover specific aspects of nucleonic interactions could be isolated and amplified in the proton emitters due to their extreme proton excess [5]. In particular combined with theoretical analysis, nuclear structural information can be extracted from measurements of half-life, proton branching ratio (fine structure), the energy and angular momentum transfer l carried away by the emitted proton, etc. The fact that the half-life of proton emission is sensitive to the Q-value and angular momentum transfer l, not only helps to determine the orbit of the emitted proton in parent nucleus in experiments, but also provides an efficient way to test theoretical models in exploring the neutron-deficient nuclear systems.Theoretically various methods have been employed in describing the properties of proton emitters, such as the spectroscopic factor and the half-life (for review see Ref.[6]). For the half-life that can be measured experimentally, a semiclassical method is applied by treating the proton emission as quantum tunneling through a potential barrier, which is composed of the Coulomb repulsion, centrifugal barrier and effective nuclear potential. Several approaches have been employed in constructing the effective nuclear potential, e.g., in terms of the density-dependent M3Y effective interaction [7], the effective interaction of Jeukenne, Lejeume, and Mahaux [8], the renormalized...