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We describe a ‘clock control unit’ based on a dual-axis cubic cavity (DACC) for the frequency stabilisation of lasers involved in a strontium optical lattice clock. The DACC, which ultimately targets deployment in space applications, provides a short-term stable reference for all auxiliary lasers—i.e. cooling, clear-out, and optical lattice—in a single multi-band cavity. Long-term cavity drift is compensated by a feed-forward scheme exploiting a fixed physical relation to an orthogonal second cavity axis; either by reference to an ultrastable 698 nm clock laser, or by exploiting the differential drift between orthogonal axes extracted by a single laser in common view. Via a change of mirror set in the cavity axis accessed by the clock laser, the system could also provide stabilisation for sub-Hz linewidths at the 698 nm clock wavelength, fulfilling all stabilisation requirements of the clock.

The QSNET consortium is building a UK network of next-generation atomic and molecular clocks that will achieve unprecedented sensitivity in testing variations of the fine structure constant, $\alpha$, and the electron-to-proton mass ratio, $\mu$. This in turn will provide more stringent constraints on a wide range of fundamental and phenomenological theories beyond the Standard Model and on dark matter models.

Quantum nondemolition (QND) measurement is a remarkable tool for the manipulation of quantum systems. It allows specific information to be extracted while still preserving fragile quantum observables of the system. Here we apply cavity-based QND measurement to an optical lattice clock—a type of atomic clock with unrivaled frequency precision—preserving the quantum coherence of the atoms after readout with 80% fidelity. We apply this technique to stabilize the phase of an ultrastable laser to a coherent atomic state via a series of repeated QND measurements. We exploit the improved phase coherence of the ultrastable laser to interrogate a separate optical lattice clock, using a Ramsey spectroscopy time extended from 300 ms to 2 s. With this technique we maintain 95% contrast and observe a sevenfold increase in the clock’s Q factor to 1.7×10^{15}.

Over the past five years many field aquatic mesocosm studies have been conducted or are under way to meet regulatory requirements of the U.S. Environmental Protection Agency (EPA). Mesocosm studies as an ecosystem-level test are still developing, and, consequently, considerable variations are evident in study design and data analyses. In addition, experimental design often does not properly address crucial points at the study outset, e.g., defining estimated entry rates (EER) for spray drift and/or runoff into aquatic environments and what are the ecologically important effects. Study endpoints need to be carefully selected relative to the test chemical, to avoid pointless and tedious measurements of a generic list of parameters that are not pertinent to the study objectives. This paper delineates criteria to be considered in mesocosm study design and then discusses the uses of one-way analysis of variance (ANOVA), where specific hypotheses are tested, and non-hypothesis testing regression methods. Conventionally in hypothesis testing, data have been tested against the null hypothesis of “no difference between treatment and control means” using Student’s t-test. A new method has been proposed by the EPA that reverses this approach and tests a null hypothesis of “a difference between treatment and control means which is greater than a specific amount”. These two methods of statistical analyses are compared.

We report on the realization of a magneto-optical trap (MOT) for metastable strontium operating on the 2.92-$\ensuremath{\mu}\mathrm{m}$ transition between the energy levels $5s5p{\phantom{\rule{0.16em}{0ex}}}^{3}{P}_{2}$ and $5s4d{\phantom{\rule{0.16em}{0ex}}}^{3}{D}_{3}$. The strontium atoms are initially captured in a MOT operating on the 461-nm transition between the energy levels $5{s}^{2}{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ and $5s5p{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}$, prior to being transferred into the metastable MOT and cooled to a final temperature of 6 $\ensuremath{\mu}\mathrm{K}$. Challenges arising from aligning the midinfrared and 461-nm light are mitigated by employing the same pyramid reflector to realize both MOTs. Finally, the 2.92-$\ensuremath{\mu}\mathrm{m}$ transition is used to realize a full cooling sequence for an optical lattice clock, in which cold samples of $^{87}\mathrm{Sr}$ are loaded into a magic-wavelength optical lattice and initialized in a spin-polarized state to allow high-precision spectroscopy of the $5{s}^{2}{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ to $5s5p{\phantom{\rule{0.16em}{0ex}}}^{3}{P}_{0}$ clock transition.

We present a measurement of the absolute frequency of the 5s$^2$ $^1$S$_0$ to 5s5p $^3$P$_0$ transition in $^{87}$Sr, which is a secondary representation of the SI second. We describe the optical lattice clock apparatus used for the measurement, and we focus in detail on how its systematic frequency shifts are evaluated with a total fractional uncertainty of $1 \times 10^{-17}$. Traceability to the International System of Units is provided via comparison to International Atomic Time (TAI). Gathering data over 5- and 15-day periods, with the lattice clock operating on average 74$\%$ of the time, we measure the frequency of the transition to be 429228004229873.1(5) Hz, which corresponds to a fractional uncertainty of $1 \times 10^{-15}$. We describe in detail how this uncertainty arises from the intermediate steps linking the optical frequency standard, through our local time scale UTC(NPL), to an ensemble of primary and secondary frequency standards which steer TAI. The calculated absolute frequency of the transition is in good agreement with recent measurements carried out in other laboratories around the world.

We present a field-programmable gate array (FPGA) based control system that has been implemented to control a strontium optical lattice clock at the National Physical Laboratory, UK. Bespoke printed circuit boards have been designed and manufactured, including an 8-channel, 16-bit digital to analog converter board with a 2 μs update rate and a 4-channel direct-digital synthesis board clocked at 1 GHz. Each board includes its own FPGA with 28 digital output lines available alongside the specialized analog or radio frequency outputs. The system is scalable to a large number of control lines by stacking the individual boards in a master-slave arrangement. The timing of the digital and analog outputs is based on the FPGA clock and is thus very predictable and exhibits low jitter. A particular advantage of our hardware is its large data buffers that, when combined with a pseudoclock structure, allow complex waveforms to be created. A high reliability of the system has been demonstrated during extended atomic clock frequency comparisons.

The development of a portable strontium lattice clock is discussed. Solutions to many of the engineering challenges required to build the next generation of portable and ultraprecise clocks will be presented. In particular, a) the realisation of a compact laser module which produces multiple stable laser frequencies required for the experiment and b) the progress made in the development of the atomics module.

We demonstrate a new method of cavity-enhanced non-destructive detection of atoms for a strontium optical lattice clock. The detection scheme is shown to be linear in atom number up to at least 10,000 atoms, to reject technical noise sources, to achieve signal to noise ratio close to the photon shot noise limit, to provide spatially uniform atom-cavity coupling, and to minimize inhomogeneous ac Stark shifts. These features enable detection of atoms with minimal perturbation to the atomic state, a critical step towards realizing an ultra-high-stability, quantum-enhanced optical lattice clock.

The effects of lambda-cyhalothrin on aquatic ecosystems has been studied under field conditions in the Philippines, USA and UK. In the Philippines, lambda-cyhalothrin was applied at field rate and 2× field rate to rice paddies and the effects on Tilapia nilotica in rice-fish culture studied. There were no effects on fish survival, growth rate or production. Lambda-cyhalothrin was applied directly to replicated pond mesocosms in trials in the USA and UK. USA mesocosms (450 m3) were treated at 3 rates. The mid-rate, representing the typical maximum estimated entry rate (from aerial applications to US cotton), was multiple applications of simulated spray-drift at 0.38% of field rate and simulated run-off applications at 1.1% field-rate. High and low-rates were 10× and 0.1× the mid-rate, respectively. The UK mesocosms (25 m3) were treated with 4 applications of simulated spray-drift at 0.38% and 3.8% field rate. Mesocosms were monitored prior to and for up to 6 months after application. In the US mesocosms there were no effects, at any treatment rate, on hydrosoil microbes, phytoplankton, periphyton or filamentous algae. At the low rate there were negligible effects on macroinvertebrate populations. The mid-rate had transient effects on some groups, notably the Hemiptera and Ephemeroptera, and the high rate showed more severe effects on macroinvertebrates and also reduced zooplankton populations. UK mesocosms gave similar results with little or no effects at the lower rate and more pronounced effects on certain sensitive groups at the high rate.

We report on progress in the development of subsystem-level devices which serve as building blocks for the next generation of portable atomic clocks. Specifically, we discuss the engineering of small, low-power, low-temperature strontium vapour dispensers and a compact optical resonator useful for the stabilisation of multiple lasers.

Details of the NPL Sr optical lattice clock activity are presented, including a full systematic evaluation of NPL's first lattice clock, Sr1, and progress of a second system, Sr2. We will focus discussion of the systematic evaluation on novel methods, such as a Rydberg spectroscopy scheme for determination of the DC Stark shift.

The DC Stark shift resulting from uncharacterized electric fields can compromise the accuracy of optical lattice clocks. We report on a new method to characterize these residual electric fields using Rydberg states. By performing electromagnetically induced transparency (EIT) spectroscopy to measure the quadratic Stark shifts of the 5s75d 1D 2 m J = 0, ±1, ±2 states in strontium, we constrain the DC Stark shift of the clock transition to below 1 × 10−18.

Electrometry is performed using Rydberg states to evaluate the quadratic Stark shift of the $5s^2$ $^1\textrm{S}_0-5s5p$ $^3\textrm{P}_0$ clock transition in strontium. By measuring the Stark shift of the highly excited $5s75d\;^1\textrm{D}_2$ state using electromagnetically induced transparency, we characterize the electric field with sufficient precision to provide tight constraints on the systematic shift to the clock transition. Using the theoretically derived, and experimentally verified, polarizability for this Rydberg state we can measure the residual field with an uncertainty well below $1 \textrm{V} \textrm{m}^{-1}$. This resolution allows us to constrain the fractional frequency uncertainty of the quadratic Stark shift of the clock transition to $2\times10^{-20}$., 7 pages, 5 figures

The UK National Quantum Technology Hub in Sensors and Metrology is one of four flagship initiatives in the UK National of Quantum Technology Program. As part of a 20-year vision it translates laboratory demonstrations to deployable practical devices, with game-changing miniaturized components and prototypes that transform the state-of-the-art for quantum sensors and metrology. It brings together experts from the Universities of Birmingham, Glasgow, Nottingham, Southampton, Strathclyde and Sussex, NPL and currently links to over 15 leading international academic institutions and over 70 companies to build the supply chains and routes to market needed to bring 10–1000x improvements in sensing applications. It seeks, and is open to, additional partners for new application development and creates a point of easy open access to the facilities and supply chains that it stimulates or nurtures.

We report the design and characterization of an optical shutter based on a piezoelectric cantilever. Compared to conventional electro-magnetic shutters, the device is intrinsically low power and acoustically quiet. The cantilever position is controlled by a high-voltage op-amp circuit for easy tuning of the range of travel, and mechanical slew rate, which enables a factor of 30 reduction in mechanical noise compared to a rapidly switched device. We achieve shuttering rise and fall times of 11 $\mu$s, corresponding to mechanical slew rates of 1.3 $\textrm{ ms}^{-1}$, with an timing jitter of less than 1 $\mu$s. When used to create optical pulses, we achieve minimum pulse durations of 250 $\mu$s. The reliability of the shutter was investigated by operating continuously for one week at 10 Hz switching rate. After this period, neither the shutter delay or actuation speed had changed by a notable amount. We also show that the high-voltage electronics can be easily configured as a versatile low-noise, high-bandwidth piezo driver, well-suited to applications in laser frequency control., Comment: 5 pages, 6 figures

We develop a method of modified hyper-Ramsey spectroscopy in optical clocks, achieving complete immunity to the frequency shifts induced by the probing fields themselves. Using particular pulse sequences with tailored phases, frequencies, and durations, we can derive an error signal centered exactly at the unperturbed atomic resonance with a steep discriminant which is robust against variations in the probe shift. We experimentally investigate the scheme using the magnetically-induced $^1$S$_0- ^3$P$_0$ transition in $^{88}$Sr, demonstrating automatic suppression of a sizeable \num{2e-13} probe Stark shift to below \num{1e-16} even with very large errors in shift compensation., Comment: 5 pages, 4 figures

Non-intrusive monitoring of the state-of-charge of sealed lead-acid batteries using wire-wound coils is described. Coils were attached to the plastic case of the batteries, adjacent to the negative end plate, and excited using ac current at 10 kHz. As the batteries were cycled, the inductance of the coils tracked the change in metallic content of the end plates. Data is presented for different discharge rates and temperatures. A variation of the technique is also described that uses less expensive equipment to measure the voltage drop across the coil, rather than inductance.

Guidelines have existed in medicine for many centuries. Galen's doctrine of laudable pus sent many to an early grave, but variance in treatment put the practitioner in a difficult position, especially if all did not go well. Currently, guidelines proliferate, allegedly based upon careful evaluation of evidence culled from a variety of sources. However, obedience to guidelines is variable internationally and nationally, thus raising questions about their enforceability. They are, of course, not legally enforceable, but courts may be influenced by them, and variation must be evidence-based. Guidelines cannot logically be regarded as being set in stone; if that were the case, then there could be no innovation and medicine would not advance.

Defence R&D Canada (DRDC) is investigating lithium-ion polymer cells for possible future use in army communications and soldier systems, because of their high specific energy. Military operation requires good performance at −20 °C but the standard commercial lithium-ion polymer cells yield only approximately 30% of their room temperature capacity at this temperature. The standard electrolyte is known to be poorly conducting at −20 °C, so DRDC has been working with a Canadian company to produce a cell containing an electrolyte that gives good low temperature performance. Prototype cells have been built and cycled under various conditions. The performance of these cells and the standard cells is discussed.

We present the design, construction, and characterisation of longitudinal- and transverse-field Zeeman slowers, based on arrays of permanent magnets, for slowing thermal beams of atomic Sr. The slowers are optimised for operation with deceleration related to the local laser intensity (by the parameter $\epsilon$), which uses more effectively the available laser power, in contrast to the usual constant deceleration mode. Slowing efficiencies of up to $\approx$ $18$ $%$ are realised and compared to those predicted by modelling. We highlight the transverse-field slower, which is compact, highly tunable, light-weight, and requires no electrical power, as a simple solution to slowing Sr, well-suited to spaceborne application. For $^{88}$Sr we achieve a slow-atom flux of around $6\times 10^9$ atoms$\,$s$^{-1}$ at $30$ ms$^{-1}$, loading approximately $5\times 10^8$ atoms in to a magneto-optical-trap (MOT), and capture all isotopes in approximate relative natural abundances.

Non-intrusive monitoring of the state-of-charge (SOC) of lead-acid batteries by the use of wire wound coils is described. Coils were attached to the outside case of the battery, adjacent to the negative end plate, and excited using ac current of frequency in the range of 1–40 kHz. The change in inductance of the coils was monitored during battery cycling, as the metallic content of the electrode changed. Following correction for temperature changes, the technique is capable of estimating the SOC of a battery to an accuracy of ±10%. The inductance profiles that were obtained changed shape as the batteries aged and also with the exciting frequency. The origins of these changes are discussed.

Degradation of the herbicide acetochlor in the unsaturated zone was quantified using two unique in situ field techniques. The DT50 values generated at two different sites on surface soil and two subsoil depths using these techniques were compared with values generated under aerobic laboratory-incubation conditions (typically 20 degrees C, 40% maximum water holding capacity). Additionally, laboratory-degradation data were generated on surface and subsoils from four other sites. All subsoils were treated with acetochlor at 5% of the surface soil application rate. Acetochlor degradation in both field- and laboratory-incubated subsoils was rapid and often exceeded surface soil rates. Field and laboratory DT50 values from all sites ranged from 2 to 88 days in subsoil, compared with a range of 1 to 18 days in surface soils. The DT50 results from in situ field techniques were comparable with those generated from laboratory incubations in the same soils, confirming the validity of performing laboratory-based degradation studies to determine pesticide DT50 values in subsoils. Microbiological characterisation of selected soils revealed that subsoils had a viable and active population, although direct counts of bacteria were consistently lower in subsoil (10(8)-10(9) g-1 dry soil) compared with surface soils (10(10) g-1 dry soil). The leaching models used to perform groundwater risk assessments (e.g. PELMO, PESTLA, MACRO-DB, PRZM and the FOCUS EU leaching scenarios) have provision for inclusion of subsoil degradation rates. However, conservative default estimates are typically used, as no other alternative is available. Results presented here show that these default values may significantly underestimate true subsoil degradation contributions, and therefore not accurately predict pesticide concentrations in groundwater. The degradation data generated for acetochlor were applied to the mathematical model PELMO to demonstrate the importance of the inclusion of subsoil degradation data in groundwater risk assessment models and thereby in the registration of pesticides in Europe.

Despite the historical record, the United Kingdom, like other countries, was slow to recognize the value of forensic odontology as an adjunct to legal proceedings. Increased recognition of the benefits bestowed by the subject largely results from the efforts of Scandinavian workers and the Federation Dentaire International (FDI). By promoting forensic odontology in the academic environment, the FDI and its contributors did much to underscore its claims to academic respectability. This has led to its acceptance in assisting the legal process in many countries, although it remains a minority speciality. Like other jurisdictions, British courts have recognized that dental expertise can be useful in resolving legal questions. However, it has to be accepted that it is an adjunct to these proceedings, and not a prime mover. Trial by experts is not liked by the courts; they prefer a system in which all of the evidence placed before them is considered in context, and not in isolation. Only in that way can a true determination of the issues be made. It is this dislike, or perhaps concern that experts could usurp the role of the court, that has been an impediment to the acceptance of the expert in trials. However, despite these misgivings, forensic odontology is widely accepted by all of the UK courts. Increasing sophistication in the methodologies available means that the value placed on the subject has increased. The courts have recognized this and are much more demanding of those who would claim that they are experts. This is quite different from some aspects of an editorial in The Lancet for 15 December 1951, which reported that “teeth have often played a distinctive part in reconstructing crime” (Anon 1951).

This study was part of a research program designed to evaluate fathead minnow (Pimephales promelas) reproduction in 17-m 3 outdoor microcosms as a test system to investigate ecosystem-level impacts of toxicants. Sex ratios of fathead minnow (FHM) adults at stocking were manipulated to regulate the biomass and numbers of young-of-the-year (YOY) following reproduction. This study reports the effect of fish densities obtained from six different sex ratios on microcosm ecology that were compared to a fishless control during a 4.5-month period. Fish sampled during the study were representative of the actual population. Taxa collected from FHM stomachs were very diverse (16 groups) representing various communities and trophic levels. Bacillariophyta, filamentous algae, and macrophytes were the dominant food source ; however, Crustacea, rotifers, chironomids, and other macroinvertebrates were also important. Effects on community structure were investigated using multivariate discriminant analysis. There were no fish density effects on zooplankton or benthic macroinvertebrate community structures. Microcosms with high FHM densities had fewer emerging chironomids, and phytoplankton levels were elevated. Phytoplankton taxa, which discriminated phytoplankton community structure differences between fish biomass groups, were also positively correlated with total phosphorus.

Large-scale aquatic mesocosm studies were formerly required by the U.S. Environmental Protection Agency (EPA) for ecological risk assessment in pesticide registration. However, the use of bluegill sunfish (Lepomis macrochirus Rafinesque) to evaluate pesticide effects on fish reproduction in large mesocosms (>300 m3) resulted in over-exploitation of invertebrates by large numbers of young-of-the-year (YOY) bluegill, thus confounding the interpretation of pesticide effects. As an alternative, a reproduction study with fathead minnows (Pimephales promelas Rafinesque) was conducted in 17-m3 outdoor microcosms. The objective of this research was to evaluate the effects of varying sex ratios of 20 adult fathead minnows (FHMs) on their reproduction during a 4.5-month period. The outcome of this study was compared to a bluegill reproduction study in 400-m3 mesocosms conducted synchronously. The logistics of monitoring the microcosms were simpler, and harvesting FHMs from microcosms took considerably less effort in comparison to harvesting bluegills from mesocosms. The FHMs produced a smaller number of larger young in comparison to bluegills, which produced large numbers of less mature YOY. The variability in total fish biomass between replicates was greater in the bluegill study, resulting in less statistical power to detect biomass effects. The FHM sex ratios significantly affected reproduction and growth, thus altering the fish population structure, despite similar stocking densities. Sex ratios with similar numbers of males and females produced a lower total biomass and number of YOY. There was no evidence of system carrying-capacity constraints on FHM growth or reproduction.

The fate and effects of two pyrethroid insecticides (lambda-cyhalothrin and cypermethrin) were investigated in replicated 25 m(3) pond mesocosms. Three pesticide treatments which simulated spray drift deposition were examined: 0.7 g a.i. ha(-1) cypermethrin and 0.17 and 1.7 g a.i. ha(-1) lambda-cyhalothrin. Based on the use rate and pesticidal activity of the chemicals, the cypermethrin and lower lambda-cyhalothrin rates were approximately equivalent. After applications, pyrethroid residues in the water column declined rapidly. Treatment-related effects were observed on some macroinvertebrate taxa, most notably the Asellidae and Gammaridae. Surfacedwelling insects also suffered initial knock-down, particularly in the 1.7 g a.i. ha(-1) lambda-cyhalothrin treatment, but there was recovery after the spray period. No adverse effects occurred on algae, macrophytes or zooplankton, but there were occasional enhancements (e.g. algal biomass and abundances of copepod nauplii and Rotifera) which may have been indirect effects. An overall comparison of the treatments indicated that the higher lambda-cyhalothrin rate had the greatest effects, whilst the cypermethrin application had a somewhat greater impact than the lower lambda-cyhalothrin treatment rate (due to effects on peracarid crustaceans). The study indicated that should spray drift occur at the levels expected for either pyrethroid's normal use patterns, potential impacts on natural aquatic ecosystems would be minor and transient.

We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise the human requirement in its operation. Central to this is a clock-referenced transfer cavity scheme for the stabilisation of cooling and trapping lasers. We highlight several measures to increase the reliability of the clock with a view towards the realisation of an optical time-scale. The clock contributed 502 hours of data over a 25 day period (84% uptime) in a recent measurement campaign with several uninterrupted periods of more than 48 hours. An instability of $2\times10^{-17}$ was reached after $10^5$ s of averaging in an interleaved self-comparison of the clock., 8 pages, 4 figures, to be published in the Proceedings of the 8th Symposium on Frequency Standards and Metrology

We report the successful demonstration and characterisation of a Zeeman slower based on an array of permanent magnets, implemented for atomic Sr on the 1S 0 → 1P 1 transition at 461 nm. Measurements of longitudinal velocity distributions and MOT loading characteristics are presented. In particular, we highlight a simple transverse-field slower, which is both compact and highly tunable, light weight (≤ 2 kg), and with no power load, as a favourable option for space-borne operation. For optimum parameters of this slower we achieve a slow flux of ∼ 3.5 × 109 atom/s at ∼ 30 m/s for 88Sr and load ∼ 2.5 × 107 atoms into a magneto-optical-trap (MOT) operating on the same 1S 0 → 1P 1 transition, which scales approximately with the relative isotopic natural abundances of Sr. With the addition of repumpers at 707 nm and 679 nm, we achieve a factor of ∼ 17 enhancement to MOT number with loading time ∼ 0.5 s.

This paper describes the residue analysis of water and hydrosoil samples taken from two separate large-scale aquatic ecotoxicology trials designed to assess the environmental fate and effects of the pyrethroids lambda-cyhalothrin and cypermethrin. Comparison of the results demonstrates the high degree of reproducibility of the chemical residue found the day after treatment using experimental mesocosms (lambda-cyhalothrin) as opposed to an in-use farm pond (cypermethrin). Both studies showed that pyrethroid residues were rapidly lost from the water column: residues of lambda-cyhalothrin were less than 2 ng litre−1 following the final application of a cumulative seasonal exposure equivalent to twelve ‚drift’ and six ‚run-off’ events, each delivering a dose equivalent to that expected from a typical event under field conditions. Hydrosoil appeared to act as a sink for pyrethroid residues and, under the stringent test conditions of the mesocosm study, lambda-cyhalothrin residues reached 3.2 μg kg−1 following the seasonal exposure described above. The cypermethrin farm-pond study illustrated the localised pattern of exposure expected under natural field conditions, with site topography and cultivation practices which represent an average ‚worst case’. Residues in hydrosoil reached a maximum level of approximately 25 μg kg−1 in one sampling zone at one interval, and thereafter declined to a level of < 9 μg kg−1 within four months.

The 1S0 - 3P0 transition at 698 nm in neutral strontium has the potential to be an extremely precise optical frequency standard [1] and is one of several candidates for a future redefinition of the second. Recent measurements of this transition at three national laboratories around the world have fractional frequency uncertainties in the 1015 range and agree to within a hertz [2,3,4]. To realise fully the potential accuracy of this frequency standard, in depth studies of systematic effects need to be performed in order to characterise them at the level necessary for a redefinition of the second. At the National Physical Laboratory we are developing a compact, diode laser based optical lattice clock. We intend to study the clock transition in both 88Sr and 87Sr with focus on the uncertainties in the frequency shifts due to blackbody radiation. The setup incorporates a novel permanent magnet based Zeeman slower [5].

This paper describes the development of methods suitable for the sampling and analysis of the pyrethroid insecticides lambda-cyhalothrin and cypermethrin in natural waters. A solid-phase water-sampling method which avoids the requirement for transport and storage of large volumes of water is described. This method is shown to be capable of extracting trace levels (ng litre−-1) of the title compounds from natural waters with efficiencies of at least 80%. Chromatographic analysis of processed samples by gas chromatography–electron capture detection enables determination of residues at levels of 1–2 ng litre−-1 in water.

Cobalt oxide films, fabricated by reactive sputtering in a 100% pure O 2 plasma are highly nonstoichiometric with a bulk oxygen to cobalt ratio of ∼ 1.15. Conversely, surface XPS studies indicate an oxygen to cobalt ratio ranging from 1.8 to 3.0 and show the presence of Co 3+ only in the surface region of the as formed films. Infrared and Raman spectra however confirm the presence of both Co 3+ and Co 2+ in the bulk and indicate that these highly defective films possess the spinel structure. Photoelectrochemical and impedance studies show that the sputtered oxide is a highly doped p-type semiconductor with an indirect bandgap of E g ∼ 1.50 eV. The electrocatalytic properties of these oxide films for oxygen reduction and evolution are reported.

Improving transport safety has not been easy. Considerable effort was needed to overcome prejudice and entrenched views before the existing achievements could be made. Thus despite the evidence of marked reductions in facilities and serious injuries in car crashes, it took eleven attempts to get seat belt laws through the British Parliament [1]. Many more years were to pass before the legislation was extended to the rear seats of cars, and bus and coach passengers are largely unprotected by seat belts. Many spurious arguments have been used with great facility by the antagonists, ranging from infringements of civil liberties to erroneous claims of dangers, to counter evidence of the benefits achievable by safety measures. These arguments must be remembered and considered in the context of their first use, for derivatives will be deployed in the future.

Smoke is a mixture of particles and gaseous chemicals of varying physical and chemical properties. When inhaled these produce the characteristic features of smoke-inhalational injury. Although heat is produced in fires it is the chemical agents which cause the damage to the airways and the lungs. Mortality and morbidity are closely related to pulmonary injury and thus to the particulate and chemical nature of smoke. Moreover, there seems to be a potentiating effect, in that the particles worsen the toxicity of the chemicals present.

Cobalt oxide films, fabricated by reactive sputtering in a 100% pure O 2 plasma are highly nonstoichiometric with a bulk oxygen to cobalt ratio of ∼ 1.15. Conversely, surface XPS studies indicate an oxygen to cobalt ratio ranging from 1.8 to 3.0 and show the presence of Co 3+ only in the surface region of the as formed films. Infrared and Raman spectra however confirm the presence of both Co 3+ and Co 2+ in the bulk and indicate that these highly defective films possess the spinel structure. Photoelectrochemical and impedance studies show that the sputtered oxide is a highly doped p-type semiconductor with an indirect bandgap of E g ∼ 1.50 eV. The electrocatalytic properties of these oxide films for oxygen reduction and evolution are reported.

Under laboratory conditions, in water without particulate matter, pyrethroid insecticides have a high toxicity to fish and some aquatic invertebrates. The pyrethroids are of very low water solubility/high lipophilicity, and therefore are rapidly and strongly adsorbed to particulate material. In the adsorbed state their bioavailability to aquatic organisms is greatly reduced. Consequently, under field conditions the aquatic impact of these insecticides is likely to be much less than might be predicted by laboratory acute or chronic toxicity test data. Over the past 10 years a large number of aquatic field studies have been carried out with pyrethroids, in natural farm ponds, streams and lakes and also in mesocosms (experimental ponds and enclosures). Recent investigations, to meet the requirements of the United States Environmental Protection Agency, have been most extensive. These studies, done in replicated experimental ponds of at least 0-04 ha, each require at least 20 man-years of effort. Following agricultural applications of the pyrethroid insecticides, spray-drift or run-off may cause minor effects upon some aquatic organisms. Algae, microorganisms, annelids, gastropods and fish are all unaffected, but some impact may occur upon certain zoo-plankton and on aquatic stages of insects. However, with products for which realistic field studies have been reported, the effects are mostly transient and are unlikely to cause adverse changes in the populations or productivity of aquatic ecosystems.

Expressions are derived for the second intensity moments of vibrational bands of symmetric top molecules in the limit of rotational broadening. An expression for the moments for parallel bands agrees, apart from one minor term, with that given by Gordon. First order Coriolis effects are included for perpendicular bands, for which the second moment is given by M(2)=B′2[2kT/Bhc+ 1/3 +B/3A]+A′2[2(1 –ζ)2kT/hc–B2/3A2+(1 – 2ζ)2]+ 2B′A′(1 – 2ζ).The potential and the problems in the use of the formulae are discussed.

Toxicology studies can contribute much to investigations into the causes of accidents. This paper examines toxicological data from 485 fatal aircraft accidents over a 24-year period in terms of relevance to causing accidents and difficulties in procuring samples for analysis.

It is demonstrated that the wings of a vibrational absorption band can be fitted to a function (δμ) 1.5 exp (−|δμ| a ) χ b [1 + exp (− he δμ| kT )] −1 . The Fourier transform of such a function plus a damped lorentzian is indistiguishable from the experimental intensity transform. The renders the matching of the early part of the transform with a free rotor function of dubious validity.

Medicolegal experts are often asked to explain how, why and when facial injuries occurred. This can only be done satisfactorily if they are considered carefully and if all of the associated features are taken into account. One aspect of the topic which has received scant attention in medical and dental texts is Biodynamics, a brief analysis of the principal features of which is reproduced in this paper.

An expression is derived for the distortion of spectral band contours resulting from use of finite slit widths. The leading term is in agreement with a correction proposed by Rayleigh in 1871 and derived from curvature arguments. It is shown that this correction, which is proportional to the second derivative of the observed spectrum, d2ƒ/dν2, allows the true band contour to be recovered to a good approximation provided that the slit width is not greater than the half band width. Loss of resolution due to finite slit widths may also be recovered. Higher power correction terms are also given, but due to the sensitivity of the higher power gradients, dnƒ/dνn, to noise, n even and greater than two, the terms appear to be of little practical importance at the present time.