Response to Comment on "An excess of massive stars in the local 30 Doradus starburst".

Farr and Mandel reanalyze our data, finding initial mass function slopes for high-mass stars in 30 Doradus that agree with our results. However, their reanalysis appears to underpredict the observed number of massive stars. Their technique results in more precise slopes than in our work, strengthening our conclusion that there is an excess of massive stars (>30 solar masses) in 30 Doradus.

Tuning the thermoelectric properties of A-site deficient SrTiO3 ceramics by vacancies and carrier concentration.

Ceramics based on Sr0.8La0.067Ti0.8Nb0.2O3-δ have been prepared by the mixed oxide route. The La1/3NbO3 component generates ∼13.4% A-site vacancies; this was fixed for all samples. Powders were sintered under air and reducing conditions at 1450 to 1700 K; products were of high density (>90% theoretical). Processing under reducing conditions led to the formation of a Ti1-xNbxO2-y second phase, core-shell structures and oxygen deficiency. X-ray diffraction (XRD) confirmed a simple cubic structure with space group Pm3[combining macron]m. Transmission electron microscopy revealed a high density of dislocations while analytical scanning transmission electron microscopy at atomic resolution demonstrated a uniform distribution of La, Nb and vacancies in the lattice. X-ray photoemission spectroscopy and thermogravimetry showed the oxygen deficiency (δ value) to be ∼0.08 in reduced samples with enhanced carrier concentrations ∼2 × 1021 cm-3. Both carrier concentration and carrier mobility increased with sintering time, giving a maximum figure of merit (ZT) of 0.25. Selective additional doping by La or Nb, with no additional A site vacancies, led to the creation of additional carriers and reduced electrical resistivity. Together these led to enhanced ZT values of 0.345 at 1000 K. The contributions from oxygen vacancies and charge carriers have been investigated independently.

Thermoelectric Power Generation from Lanthanum Strontium Titanium Oxide at Room Temperature through the Addition of Graphene.

The applications of strontium titanium oxide based thermoelectric materials are currently limited by their high operating temperatures of >700 °C. Herein, we show that the thermal operating window of lanthanum strontium titanium oxide (LSTO) can be reduced to room temperature by the addition of a small amount of graphene. This increase in operating performance will enable future applications such as generators in vehicles and other sectors. The LSTO composites incorporated one percent or less of graphene and were sintered under an argon/hydrogen atmosphere. The resultant materials were reduced and possessed a multiphase structure with nanosized grains. The thermal conductivity of the nanocomposites decreased upon the addition of graphene, whereas the electrical conductivity and power factor both increased significantly. These factors, together with a moderate Seebeck coefficient, meant that a high power factor of ∼2500 µWm(-1)K(-2) was reached at room temperature at a loading of 0.6 wt % graphene. The highest thermoelectric figure of merit (ZT) was achieved when 0.6 wt % graphene was added (ZT = 0.42 at room temperature and 0.36 at 750 °C), with >280% enhancement compared to that of pure LSTO. A preliminary 7-couple device was produced using bismuth strontium cobalt oxide/graphene-LSTO pucks. This device had a Seebeck coefficient of ∼1500 µV/K and an open voltage of 600 mV at a mean temperature of 219 °C.

A kiloparsec-scale internal shock collision in the jet of a nearby radio galaxy.

Jets of highly energized plasma with relativistic velocities are associated with black holes ranging in mass from a few times that of the Sun to the billion-solar-mass black holes at the centres of galaxies. A popular but unconfirmed hypothesis to explain how the plasma is energized is the 'internal shock model', in which the relativistic flow is unsteady. Faster components in the jet catch up to and collide with slower ones, leading to internal shocks that accelerate particles and generate magnetic fields. This mechanism can explain the variable, high-energy emission from a diverse set of objects, with the best indirect evidence being the unseen fast relativistic flow inferred to energize slower components in X-ray binary jets. Mapping of the kinematic profiles in resolved jets has revealed precessing and helical patterns in X-ray binaries, apparent superluminal motions, and the ejection of knots (bright components) from standing shocks in the jets of active galaxies. Observations revealing the structure and evolution of an internal shock in action have, however, remained elusive, hindering measurement of the physical parameters and ultimate efficiency of the mechanism. Here we report observations of a collision between two knots in the jet of nearby radio galaxy 3C 264. A bright knot with an apparent speed of (7.0 ± 0.8)c, where c is the speed of light in a vacuum, is in the incipient stages of a collision with a slower-moving knot of speed (1.8 ± 0.5)c just downstream, resulting in brightening of both knots--as seen in the most recent epoch of imaging.

Cohen-Boyer patent finally issued.

KIE: On 28 August 1984, the Patent Office finally approved a second Cohen-Boyer patent which covers hybrid bacterial plasmids. This patent, together with an earlier one covering methods, provides the University of California, San Francisco, and Stanford University with proprietary control over the basic techniques and tools used in gene splicing. The Patent Office rejected a claim by an alleged third co-inventor because of doubts about whether information in the patent application would enable the plasmids to be duplicated. The universities accepted the patent's restriction to bacterial plasmids and will pursue a separate application for yeast plasmids.^ieng

Melmon resigns Stanford chairmanship.

KIE: The chairman of Stanford Medical School's department of medicine, Kenneth Melmon, has resigned his administrative position after receiving a letter of censure from Stanford president Donald Kennedy. A university ethics committee had found Melmon guilty of negligent scholarship after it was discovered that a textbook chapter authored by him contained unattributed material from a book he had earlier helped edit. Melmon maintained that permission to use the material and its proper attribution had been handled by his editor, but this later proved not to be the case. Stanford plans no further action in the matter, and Melmon will retain his professorship.^ieng

Illmensee faces funding cutoff.

KIE: Based on the findings of an international commission of inquiry, the Swiss national science foundation has withdrawn its financial support of Karl Illmensee, a University of Geneva embryologist who was accused last year of manipulating experimental protocols. The National Institutes of Health is still considering whether to resume funding Illmensee's work. Loss of financial support could make it difficult for Illmensee to carry out the international commission's recommendation that he repeat the challenged experiments.^ieng

Genetically engineered plants get a green light.

KIE: The National Institutes of Health's Recombinant DNA Advisory Committee has given conditional approval to a proposal by the Cetus Madison Corporation to field test plants that have been genetically manipulated to resist some diseases. The committee made no recommendation, however, on another field test proposed by BioTechnica International Inc. Both proposals had been challenged by a coalition of environmental groups led by Jeremy Rifkin, who has now filed a freedom of information request to NIH asking for documents pertaining to their health and safety aspects.^ieng

Legal threat, cold delay UC experiment.

KIE: A controversial University of California, Berkeley, experiment that would have released genetically engineered organisms into the environment has been postponed. Although Steven Lindow and his colleagues received approval for field tests from the National Institutes of Health's Recombinant DNA Advisory Committee, environmental activist Jeremy Rifkin filed suit against NIH, claiming its action violated the National Environmental Policy Act. With one suit pending and another threatened, the decision was made to postpone the tests until spring 1984. The outcome of the Rifkin suit will have an impact on other genetic research with ecological implications.^ieng

Agricultural genetics goes to court.

KIE: A coalition of environmental groups headed by activist Jeremy Rifkin has filed lawsuits to halt experiments that would release genetically engineered organisms into the environment. One suit, filed against the National Institutes of Health on 14 September 1983, would block tests by researchers at the University of California, Berkeley. A second suit, filed 16 September 1983 against Cetus Madison and BioTechnica, seeks to halt field tests that had been approved by NIH's Recombinant DNA Advisory Committee. At issue are NIH's role in evaluating the risks of genetic experimentation, and the public's right of access to proprietary information.^ieng

Ethics panel faces the ax.

KIE: The President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research, scheduled to go out of business on 31 December 1982, requested a three-month extension of its life to complete several reports. This brief news item reports that the requested extension was added as an amendment to a budget bill by the Senate but then stripped from the bill by a House-Senate conference committee.^ieng