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A “sieving” algorithm, which gradually removes element candidates in a radio array to fit $u-v$distributions to a predefined shape, is introduced in this paper. The algorithm is applicable for optimizing the configuration of an interferometric array either in snapshot or Earth rotation synthesis observation mode. It has also been enhanced to do global array optimization when objects at different declinations are taken into account. To illustrate its efficiency, the sieving algorithm is employed to configure an optimum 30-element array from 2500 candidates within a circular or donut boundary. A preliminary C++ package implementing the algorithm has been developed for configuration designs and tests. The method is well adapted to general use due to flexibility and rapidity. For example, it has been tentatively applied to the optimization of the KARST array, a Chinese concept of the SKA.

Radiometeric CMB measurements need to be highly stable and this stability is best obtained with differential receivers. The residual 1/fnoise in the differential output is strongly dependent on the radiometer input offset which can be cancelled using various balancing strategies. In this paper we discuss a software method implemented in the PLANCK-LFI pseudo-correlation receivers which uses a tunable gain modulation factor, r, in the sky-load difference. Numerical simulations and experimental data show how proper tuning of the parameter rensures a very stable differential output with knee frequencies of the order of few mHz. Various approaches to calculate rusing the radiometer total power data are discussed with some examples relevant to PLANCK-LFI. Although the paper focuses on pseudo-correlation receivers and the examples are relative to PLANCK-LFI, the proposed method and its analysis is general and can be applied to a large class of differential radiometric receivers.

Major engineering failures act as a catalyst for change in standards of practice and therefore create the opportunity for establishing better ethical practices for the profession. When examining ethics in engineering practice, it is useful to make the distinction between ethics in engineering and ethics of engineering. Ethics in engineering deals with the ethics of actions of individual engineers. Ethics of engineering deals with ethical issues that involve the role of engineers in industry, the ethics of the organizations in which they work and of professional engineering societies, and the ethical responsibilities of the profession. This paper presents case studies of two major structural disasters—the 1907 Quebec Bridge collapse and the 1981 Kansas City, Mo. Hyatt Regency walkway failure. The effect of each failure on engineering ethics is examined from the viewpoint of both ethics in engineering and of ethics of engineering. In response to failures, engineers need to change professional procedures and practices so that they reinforce, rather than place obstacles in the way of, moral action.

V(D)J genomic recombination joins single gene segments to encode an extensive repertoire of antigen receptor specificities in T and B lymphocytes. This process initiates with double-stranded breaks adjacent to conserved recombination signal sequences that contain either 12- or 23-nucleotide spacer regions. Only recombination between signal sequences with unequal spacers results in productive coding genes, a phenomenon known as the “12/23 rule.” Here we present two novel genomic tools that allow the capture and analysis of immune locus rearrangements from whole thymic and splenic tissues using second-generation sequencing. Further, we provide strong evidence that the 12/23 rule of genomic recombination is frequently violated under physiological conditions, resulting in unanticipated hybrid recombinations in ∼10% of Tcraexcision circles. Hence, we demonstrate that strict adherence to the 12/23 rule is intrinsic neither to recombination signal sequences nor to the catalytic process of recombination and propose that nonclassical excision circles are liberated during the formation of antigen receptor diversity.

When low-temperature thin films of either ionic or covalent dinitrogen pentaoxide, N2O5, are exposed to gaseous HCl and water, the only products observed in the solid phase by reflection−absorption infrared spectroscopy (RAIRS) are molecular nitric acid and the oxonium ion. Nitryl chloride, ClNO2, is not detectable. When dinitrogen pentaoxide is co-deposited with hydrogen chloride and water at 85 K and annealed to 140 K, the resultant RAIR spectra indicate that the film is composed of H3O⁺Cl^-, N2O5, HNO3, and D2h-N2O4. When nitryl chloride is co-deposited with either water or HCl/water mixtures, infrared spectra indicative of solid D2h-N2O4 are measured, as well as peaks corresponding to nitrate ions and cis-ClONO (chlorine nitrite). Reaction between ClNO2 and its isomer, cis-ClONO, is proposed as an explanation for the formation of dinitrogen tetraoxide in both systems. The proposed reaction mechanism for this hydrolysis is extended to the N2O5/H2O/HCl deposits in order to explain the lack of observable ClNO2 in such thin films.

Following a random block experimental design in each case, three repeated measurement studies were carried out in three different groups of conscious rabbits, to investigate the renal effects of increasing doses of intravenous calcium chloride (CaCl2) and bovine parathyroid hormone (PTH). In the first study, each rabbit received either CaCl2 (0.15, 0.3, 0.5 or 1.0 mg kg‐1 min‐1) or vehicle alone (control) for 160 min. In the second study, rabbits were given either PTH (0.15 microgram kg‐1 min‐1), CaCl2 (1.0 mg kg‐1 min‐1), PTH plus CaCl2 (0.15 microgram kg‐1 min‐1 and 1.0 mg kg‐1 min‐1, respectively) or vehicle alone; PTH was infused for just over 60 min. In the third study, a much smaller dose (0.05 mg kg‐1 min‐1) of CaCl2 was infused for 100 min. CaCl2 infusion produced a striking fall in fractional excretion of sodium of at least 50% (P less than 0.01), but this was not dose related, being almost maximal at the smaller doses infused. Although this effect was evident in the absence of any changes in total plasma calcium concentration at the lower doses of CaCl2, renal calcium excretion was increased between 2‐ and 20‐fold (P less than 0.01) at all doses infused. Fractional excretion of chloride doubled at the two higher doses of CaCl2 (P less than 0.01), but potassium excretion was unchanged. There were no consistent alterations in mean arterial blood pressure, effective renal plasma flow, glomerular filtration rate or plasma renin activity (PRA); total plasma calcium concentration was consistently elevated only during infusion of the high dose by just under 1 mmol l‐1. PTH infusion had no measured effect on fractional excretion of sodium or renal calcium excretion, but doubled fractional potassium excretion (P less than 0.05). Heart rate and PRA increased (P less than 0.01 and less than 0.05, respectively), the latter by 50%, but systemic pressure and renal haemodynamics were not significantly affected. By contrast, PTH infused with CaCl2 produced a 4‐fold rise in fractional sodium excretion and although renal calcium excretion remained increased, it was reduced by ca. 80% when compared with renal calcium excretion during infusion of CaCl2 alone. Infusion of PTH alone increased PRA, but when PTH and CaCl2 were infused together, PRA did not change.(ABSTRACT TRUNCATED AT 400 WORDS)

The ability to communicate clearly is vital to any quality engineered project. Because of the high degree of interdependency among activities in the concurrent design of complex engineering systems, the ability to coordinate and synchronize communication among design team members is crucial. The computer-based tool, SteelTeam, is under development and integrates knowledge-based expert systems with a computer-aided design and drafting environment to create a system that helps bridge communication gaps in the steel building industry. SteelTeam makes design, fabrication, and construction knowledge available to each of the parties involved in the steel building design. In addition, SteelTeam provides a standard format for the design information that is passed between parties during the design process. The completeness of this information is crucial to the generation of design alternatives, which are necessary to ensure that the optimum product is developed. By looking at the issues involved in concurrent engineering, it is possible to identify areas whose improvement leads to faster product development, lower cost, and improved productivity. These issues are addressed by SteelTeam through improved communication between the parties involved in the design of the steel building.

The interactions of HOCl and ClONO2 with pure and HCl-doped water ice have been reinvestigated using infrared spectroscopy in conjunction with static and thermal desorption mass spectrometry in the temperature range 140−180 K to probe the detailed mechanisms of their heterogeneous atmospheric reactions. In agreement with earlier studies, HOCl was found to react with hydroxonium chloride species to directly produce molecular chlorine. This molecular chlorine desorbed from the surface above ca. 155 K either directly or in subsequent thermal desorption experiments, depending upon substrate temperature at the time of reaction. ClONO2 was observed to heterogeneously hydrolyze upon water ice to produce HOCl and hydrated H3O⁺NO3^-. Below ca. 155 K, HOCl remains adsorbed on the ice surface, while above ca. 155 K, it desorbs directly into the gas phase. These results suggest that a long-lived, adsorbed state of HOCl is unlikely to play a direct role in heterogeneous chemistry at stratospheric temperatures. The direct reaction of ClONO2 with an ice surface saturated with ionic hydrates of HCl was observed to result in the production of molecular chlorine, which, as for the HOCl reaction, either remained adsorbed or desorbed from the surface depending upon temperature. This provides convincing evidence for the direct heterogeneous reaction of Cl^- with ClONO2 under stratospheric conditions. A novel explanation for the enhanced reactivity of ClONO2 toward atmospherically relevant substrates is presented, in which a partially ionized precursor state is formed. Partial ionization of ClONO2 along the Cl−O bond serves to increase the electrophilicity of the chlorine atom, making the site highly prone to nucleophilic attack by either water or adsorbed chloride ions.

•We analyse a large dataset on public attitudes in Great Britain over six years.•We develop and test five hypotheses based on a novel conceptual framework.•We chart spatial and temporal trends in public support for eight energy sources.•We identify a growing divide between support for renewable and non-renewable energy.•Our results help to understand and explain public acceptance at a national scale.

The scientific performance of the Planck Low Frequency Instrument (LFI) after one year of in-orbit operation is presented. We describe the main optical parameters and discuss photometric calibration, white noise sensitivity, and noise properties. A preliminary evaluation of the impact of the main systematic effects is presented. For each of the performance parameters, we outline the methods used to obtain them from the flight data and provide a comparison with pre-launch ground assessments, which are essentially confirmed in flight.

The Low Frequency Instrument (LFI) on-board the ESA Plancksatellite carries eleven radiometer subsystems, called radiometer chain assemblies (RCAs), each composed of a pair of pseudo-correlation receivers. We describe the on-ground calibration campaign performed to qualify the flight model RCAs and to measure their pre-launch performances. Each RCA was calibrated in a dedicated flight-like cryogenic environment with the radiometer front-end cooled to 20 K and the back-end at 300 K, and with an external input load cooled to 4 K. A matched load simulating a blackbody at different temperatures was placed in front of the sky horn to derive basic radiometer properties such as noise temperature, gain, and noise performance, e.g. 1/fnoise. The spectral response of each detector was measured as was their susceptibility to thermal variation. All eleven LFI RCAs were calibrated. Instrumental parameters measured in these tests, such as noise temperature, bandwidth, radiometer isolation, and linearity, provide essential inputs to the Planck-LFI data analysis.

In this paper we present the Low Frequency Instrument (LFI), designed and developed as part of the Planckspace mission, the ESA programme dedicated to precision imaging of the cosmic microwave background (CMB). Planck-LFI will observe the full sky in intensity and polarisation in three frequency bands centred at 30, 44 and 70 GHz, while higher frequencies (100–850 GHz) will be covered by the HFI instrument. The LFI is an array of microwave radiometers based on state-of-the-art indium phosphide cryogenic HEMT amplifiers implemented in a differential system using blackbody loads as reference signals. The front end is cooled to 20 K for optimal sensitivity and the reference loads are cooled to 4 K to minimise low-frequency noise. We provide an overview of the LFI, discuss the leading scientific requirements, and describe the design solutions adopted for the various hardware subsystems. The main drivers of the radiometric, optical, and thermal design are discussed, including the stringent requirements on sensitivity, stability, and rejection of systematic effects. Further details on the key instrument units and the results of ground calibration are provided in a set of companion papers.

This paper provides an overview of the Low Frequency Instrument (LFI) programme within the ESA Planck mission. The LFI instrument has been developed to produce high precision maps of the microwave sky at frequencies in the range 27–77 GHz, below the peak of the cosmic microwave background (CMB) radiation spectrum. The scientific goals are described, ranging from fundamental cosmology to Galactic and extragalactic astrophysics. The instrument design and development are outlined, together with the model philosophy and testing strategy. The instrument is presented in the context of the Planck mission. The LFI approach to ground and inflight calibration is described. We also describe the LFI ground segment. We present the results of a number of tests demonstrating the capability of the LFI data processing centre (DPC) to properly reduce and analyse LFI flight data, from telemetry information to calibrated and cleaned time ordered data, sky maps at each frequency (in temperature and polarization), component emission maps (CMB and diffuse foregrounds), catalogs for various classes of sources (the Early Release Compact Source Catalogue and the Final Compact Source Catalogue). The organization of the LFI consortium is briefly presented as well as the role of the core team in data analysis and scientific exploitation. All tests carried out on the LFI flight model demonstrate the excellent performance of the instrument and its various subunits. The data analysis pipeline has been tested and its main steps verified. In the first three months after launch, the commissioning, calibration, performance, and verification phases will be completed, after which Planck will begin its operational life, in which LFI will have an integral part.

We present the calibration and scientific performance parameters of the PlanckLow Frequency Instrument (LFI) measured during the ground cryogenic test campaign. These parameters characterise the instrument response and constitute our optimal pre-launch knowledge of the LFI scientific performance. The LFI shows excellent 1/fstability and rejection of instrumental systematic effects; its measured noise performance shows that LFI is the most sensitive instrument of its kind. The calibration parameters will be updated during flight operations until the end of the mission.