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Spider pulsars are neutron stars that have a companion star in a close orbit. The companion star sheds material to the neutron star, spinning it up to millisecond rotation periods, while the orbit shortens to hours. The companion is eventually ablated and destroyed by the pulsar wind and radiation1,2. Spider pulsars are key for studying the evolutionary link between accreting X-ray pulsars and isolated millisecond pulsars, pulsar irradiation effects and the birth of massive neutron stars3–6. Black widow pulsars in extremely compact orbits (as short as 62 minutes7) have companions with masses much smaller than 0.1 M⊙. They may have evolved from redback pulsars with companion masses of about 0.1–0.4 M⊙and orbital periods of less than 1 day8. If this is true, then there should be a population of millisecond pulsars with moderate-mass companions and very short orbital periods9, but, hitherto, no such system was known. Here we report radio observations of the binary millisecond pulsar PSR J1953+1844 (M71E) that show it to have an orbital period of 53.3 minutes and a companion with a mass of around 0.07 M⊙. It is a faint X-ray source and located 2.5 arcminutes from the centre of the globular cluster M71.

Fast radio bursts (FRBs) are highly dispersed, millisecond-duration radio bursts1–3. Recent observations of a Galactic FRB4–8suggest that at least some FRBs originate from magnetars, but the origin of cosmological FRBs is still not settled. Here we report the detection of 1,863 bursts in 82 h over 54 days from the repeating source FRB 20201124A (ref. 9). These observations show irregular short-time variation of the Faraday rotation measure (RM), which scrutinizes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarization in more than half of the burst sample, including one burst reaching a high fractional circular polarization of 75%. Oscillations in fractional linear and circular polarizations, as well as polarization angle as a function of wavelength, were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit (au; Earth–Sun distance) of the source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy10–12show a barred spiral, with the FRB source residing in a low-stellar-density interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova.

The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4and a compact persistent radio source5. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately 903−111+72parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies2,6, far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications.

Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances1–3. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources4–13, but no convincing evidence has been collected so far14. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft γ-ray bursts15. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft γ-ray/hard-X-ray flare18–21. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-γ-ray repeater (SGR) bursts were detected in γ-ray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB–SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.

Three differently charged nanoscale features were constructed by sequential nanografting of 6-mercaptohexan-1-ol, N-(6-mercapto)hexylpyridinium bromide, and 3-mercaptopropionic acid into a self-assembled monolayer resist of an alkanethiol terminated with a hexa(ethylene glycol) group on an atomically flat template stripped gold surface. The immobilization of three proteins, lysozyme, rabbit IgG, and bovine carbonic anhydrase (II), onto these different charged nanopatches was studied at a variety of pH values. At pH 4.5, all three proteins adsorbed onto the charged nanosurfaces. At higher pH, the proteins behaved differently, depending on the pH and relative surface charge of the nanosurface. A surface charge distribution model was employed to explain the unusual adsorption behavior of carbonic anhydrase. Finally, an approach that combines electrostatic immobilization and specific protein−protein interactions to fabricate multiple-layered (protein G/rabbit IgG/anti-IgG) three-dimensional (3D) protein nanostructures is presented, demonstrating that the combination of nanografting, electrostatic immobilization, and specific protein interaction is a powerful tool for construction of novel 3D protein surface nanostructures.

ABSTRACTGlycine sodium salt reacts with C60to give a water soluble derivative 1, acidification of which produces a less soluble product 2. When compound 2 is treated with Ln(CIO4)3(Ln=La, Y) in several different molar ratios, insoluble rare earth complexes: C60(Gly)xLnx/3(OH)y(H2O)z(x=7-8, y=4-6, z=2-6) were obtained. These new compounds have been characterized by IR.TG-DTA and XPS spectra.

Aromatase, a cytochrome P-450, catalyzes the formation of aromatic C18 estrogenic steroids from C19 androgens. Using the x-ray structure of cytochrome P-450cam as the model, seven mutants of human aromatase were designed and expressed in Chinese hamster ovary cells by a stable expression method. They are His-128→Gln, His-128→Ala, Cys-299→Ala, Glu-302→Leu, Asp-309→Asn, Asp-309→Ala, and Ser-312→Cys. The presence of the aromatase mutants in the transfected Chinese hamster ovary cells were confirmed by immunoprecipitation analysis. The kinetic parameters of these mutants using [1 beta,2 beta-3H] androstenedione (or [1 beta-3H]androstenedione), and [1 beta,2 beta-3H]testosterone as substrates were determined. In addition, inhibition profiles for these mutants with two aromatase inhibitors, 4-hydroxyandrostenedione and aminoglutethimide were obtained. Furthermore, the reactions catalyzed by these mutants were examined by evaluating the levels of the product estrone, and two intermediates, 19-hydroxyandrostenedione and 19-oxoandrostenedione by reverse phase high performance liquid chromatography using [7-3H]androstenedione as the substrate. Our results indicate that among the positions we modified, Asp-309 appears to be very important for the enzyme catalysis.

The non-uniform deformation (necking and thinning) development and fracture of superplastic materials under both uniaxial tension and circular sheet bulging are numerically analysed by considering the effects of strain rate sensitivity and cavity growth with superimposed pressure. It is found that the fracture mode, which is controlled by both strain rate sensitivity and cavity growth rate, can be changed by superimposed pressure from fracture without external necking for cavity sensitive alloys at zero pressure to fracture with necking development or extensive thinning at pressure large enough to completely suppress cavity growth. Fracture mechanism diagrams are presented which enable prediction of the fracture mode to be made as a function of material parameters and pressure conditions for uniaxial tension and bulging.MST/724

Aromatase, a cytochrome P450, catalyzes the formation of aromatic C-18 estrogenic steroids from C-19 androgens. Four mutants of human aromatase have been expressed in Chinese hamster ovary cells using a stable expression method. The activities of these mutants were determined using [1 beta,2 beta-3H]androstenedione, [19-14C]androstenedione, and [1 beta,2 beta-3H]testosterone as substrates. The mutant Phe-406----Arg was completely inactive. Since there were only small changes in the Km and Vmax values for all substrates for mutants Tyr-361----Phe and Tyr-361----Leu, the residue Tyr-361 appears not to be directly involved in the substrate binding. The mutant Pro-308----Phe had altered catalytic properties; the Km values for androstenedione, but not testosterone, decreased significantly. These results, along with those obtained from inhibition studies with aromatase inhibitors, 4-hydroxyandrostenedione and aminoglutethimide, suggest that Pro-308 is probably situated in the active site of the enzyme and may be interacting with the D ring of the steroids.

Glycine sodium salt reacts with C60 to give a water soluble derivative 1, acidification of which produces a less soluble product 2. When compound 2 is treated with Ln(CIO4)3 (Ln=La, Y) in several different molar ratios, insoluble rare earth complexes: C60 (Gly)xLnx/3(OH)y(H2O)z (x=7-8, y=4-6, z=2-6) were obtained. These new compounds have been characterized by IR.TG-DTA and XPS spectra.

The relationship between structures and photocurrent generation properties in a series of dye congeners based on a hemicyanine template has been investigated by using their LB film modified ITO electrodes in a traditional three-electrode cell under the same conditions. Experimental data and semipirical quantum calculation results show that the molecular polarity is the key factor for the quantum yield of photocurrent generation in this kind of molecule. The effect of applied bias voltage, addition of electron donors and acceptors, and saturation degree of O2 or N2 on photocurrent generation of the selected one has also been examined.

A cathodic photocurrent was obtained from a hemicyanine dye containing zinc complex; [(CH3)2NC6H4CH&dbd;CHC5H4NC18H37]2Zn(dmit)2 (where dmit = 4,5-dimercapto-1,3-dithiole-2-thione), modified SnO2 electrode by Langmuir−Blodgett (LB) technology in a 1 M KCl electrolyte solution. The action spectrum conforms to the absorption spectrum very well indicating that the monomers on the surface of the electrode are responsible for the photocurrent generation. Some factors which may affect the observed photocurrent such as the bias voltage, the concentration of donor or acceptor in the electrolyte solution, pH value, and light intensity have been investigated. Data show that the quantum yield is 2-fold increased when a conductive zinc complex anion is used with the LB films to replace the I^- in the molecule of (CH3)2NC6H4CH&dbd;CHC5H4NC18H37I, so that this kind of compound can be evaluated as a promising photoelectric conversion material.