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We show that, for reasonable assumptions, conductively driven and ablation-driven evaporation of clouds in the core of the starburst galaxy M82 lead to a rate of mass injection into the superwind that is several times greater than that due to supernovae. This is in harmony with the results of efforts to construct a global superwind model consistent with the X-ray emission of M82. We examine the possibility that the increase of pressure in a starburst causes the burst to develop by inducing gravitational instability of the clouds.

Staff doses arising from the use of X-rays are principally due to scattered radiation. This is related to the dose received by the patient expressed as the dose-area product (DAP). Doses to patients in interventional radiology are generally higher than for other fluoroscopically guided procedures. Doses to interventional radiologists are, therefore, amongst the highest associated with the use of diagnostic X-rays. The results of staff dose monitoring normalized to DAP should provide an indicator of those procedures which are associated with particularly high radiation exposures to staff, and should help to identify those radiologists whose practice may result in unnecessarily high doses to themselves. A study has been made of patient doses in two X-ray rooms used for interventional procedures associated with vascular and liver diseases. Doses to radiologists in these rooms were normalized to DAP. It was found that the average doses to the body, neck and hands were 0.05, 0.89 and 2.45 microSv/(Gy cm2), respectively for those radiologists with no significant involvement in hepatobiliary procedures. Higher doses were found for one radiologist whose workload included biliary drainage. The whole body dose was 0.17 microSv/(Gy cm2) or 5.8 mSv per year. It was shown that the doses to the neck and hands for the biliary drainage work was 6.59 and 29.0 microSv/(Gy cm2), respectively. This study has demonstrated the value of DAP as a measure of radiologist workload in respect of its significance in terms of staff dose.

The Roads and Traffic Authority of NSW (RTA) (Australia) has developed a high standard of practice in collecting, interpreting and documenting geotechnical information for road construction contracts. In particular high standards have been developed for seismic refraction information and its integration into overall geotechnical information in relation to detailed design, documentation for contract tendering, road construction and its possible use in evaluating contract claims. It is important to treat the seismic information as an independent source of data for an overall geological model that is developed for the site. This model is derived from sources such as geological mapping and surface observations, drilling, pitting and geophysics. Use of this approach has been critical in achieving substantial reductions is cost overruns attributable to geotechnical conditions. The simplistic approach of comparing bulk property information from geophysics with the specific point information from drilling or test pits, and ascribing differences to erroneous geophysical interpretation, or adjusting the geophysics to agree with the drilling can lead to errors in the geological model. This in turn can lead to costly errors in tendering and in construction planning and often to protracted contractual claims.

A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background (CMB), as well as by a nearby active galactic nucleus (AGN). These radiation fields excite atoms and molecules and produce emission in different ways. We revisit the escape probability theorem and derive a novel expression that accounts for the presence of external radiation fields. We show that when the field is isotropic the escape probability is reduced relative to that in the absence of external radiation. This is in agreement with previous results obtained under ad hoc assumptions or with the two-level system, but can be applied to complex many-level models of atoms or molecules. This treatment is in the development version of the spectral synthesis code Cloudy. We examine the spectrum of a Spitzer cloud embedded in the local interstellar radiation field, and show that about 60 percent of its emission lines are sensitive to background subtraction. We argue that this geometric approach could provide an additional tool toward understanding the complex radiation fields of starburst galaxies., 12 pages, 7 figures, accepted for publication to ApJ

Soil erosion is one of the processes responsible for water and soil quality deterioration and is impacted by local soil and land cover conditions. One of the primary functions of land cover is to protect the soil and prevent land degradation by water and wind erosion [1]. Recent interest in biofuel energy production can compromise soil quality due to increased removal of crop residue to be used as source of biofuel feedstocks. Knowledge of the impact of human-induced changes to land cover is critical to developing ecosystem-based management approaches to address these issues.

OBJECTIVE: To compare the potential cost effectiveness of vaccination against hepatitis B virus (HBV) targeted at genitourinary clinic (GU) attendees with that of universal infant vaccination. DESIGN: A mathematical model of sexual and perinatal transmission of HBV was used to compare the effectiveness among heterosexual and homosexual populations of programmes of mass infant vaccination and targeted immunisation of genitourinary medicine (GU) clinic attendees. Each was applied to 90% of the eligible population with differing assumptions about rates of compliance and seroconversion - problems of delivery (obtaining high compliance) was considered a significant drawback of targeted vaccination. Observed relationships between GU clinic attendance and sex partner change rates for heterosexuals and for homosexuals were used to define the rates of vaccination uptake within sexual activity risk groups. SETTING: England and Wales. RESULTS: Model results showed that for heterosexuals universal infant vaccination became more effective than clinic based vaccination only approximately 40 years after the start of the programme and that the predicted cost effectiveness of GU clinic vaccination was greater at all times. For homosexuals, clinic vaccination was always more effective over the time frame considered, but by 50 years if it were carried out without prior screening it had become appreciably less cost effective than a mass infant programme. With prior screening in GU clinics this cost effectiveness deficit was only marginal. CONCLUSIONS: Targeted vaccination might have a much greater potential than is realised at present, particularly if it were possible to improve compliance of clinic attendees. A fuller comparison between mass infant and targeted vaccination must await the specific inclusion in the model of other risk groups such as intravenous drug users. An important determinant of the relative merits of the two approaches is the relationship between rates of attendance and of changing sexual partners. Further research on this is required.

Scatter dose as a function of dose-area product (DAP) has been studied over a range of tube potentials and scattering angles. Data are presented to permit the calculation of scatter dose from DAP at distances of 1 m or more from the patient. This method has been used to calculate absorbed dose to the walls of six existing X-ray rooms which are used for interventional radiology, angiography or barium contrast studies. These calculations have been compared with measurements using thermoluminescent dosemeters. The median ratio of measured to calculated dose was 0.50 and the maximum value was 1.26. It was concluded that the calculation of scatter dose from DAP using the factors derived in this report can be used as the basis for the specification of radiation protection barriers. The busiest room in this study in terms of DAP had a DAP rate of 224 Gy cm2 per day. From the scatter factors presented here, it was shown that the room walls did not need to have more than 1.2 mm of lead equivalence.

SUMMARYIn order to construct an analytical model of onchocerciasis transmission, it is necessary to elucidate the functional relationships of the various population rate processes taking place within the human and vector hosts. Two previous papers have explored the evidence for density-dependent regulation in relation to microfilarial intake by, and larval development within, theSimulium host. This paper investigates the survivorship of wild-caught blackfly samples fed on subjects with different intensities ofOnchocerca volvulusmicrofilarial infection. Analyses were based on data for GuatemalanS. ochraceum s.l.(possessing a well-developed cibarial armature), West AfricanS. damnosum s.l.(forest species), and South VenezuelanS. guianense(the latter two lacking a toothed cibarium). The mean survival times of samples of the 3 species, kept under laboratory conditions, decreased as parasite intake increased, the rate of mortality being dependent on the fly’s age (measured as time post-feeding) and on the worm load acquired. An empirical, timedependent hazard function was fitted to observed death rates/fly/day which rose very shortly after engorgement, declined subsequently, and rose again throughout the extrinsic incubation period of the parasite. The parameters of this hazard model were all positively correlated with the density of microfilariae in the bloodmeal. Expressions of survivorship and life-expectancy as explicit functions of time post-feeding and mean parasite intake were derived. The average expectation of life at engorgement for uninfected flies in the laboratory was estimated to be around 1 week for both, armed and unarmed blackflies. Residual life-expectancy decreased with time post-feeding and microfilarial load in both categories of vectors. This decline (resulting from age- and parasite-dependent mortality rates) was much more pronounced in those species lacking a toothed fore-gut. Whilst a fraction of heavily infectedS. ochraceumwas able to survive the latent period of the parasite, being therefore potentially capable of transmitting the infection, equivalent worm loads inS. guianenseresulted in a drastic reduction of the expectation of infective life. These results provide additional evidence to support the hypothesis that, in the case of intrinsically susceptible vectors, unarmed simuliids are more efficient at low microfilarial loads, when the transmission rate from human to vector host is higher, and parasite-induced fly mortality is negligible. The opposite takes place in armed flies, which perform poorly at low parasite burdens and better at heavier loads, with little parasite-induced vector death.

Study objective : To determine if albuterol delivery by the combination of a metered-dose inhaler (MDI) with a spacer is equal in effectiveness to nebulization in a pediatric emergency department setting. Design : Prospective series. Setting : Urban children's hospital emergency department. Participants : Patients ≥six years of age with the diagnosis of acute asthma exacerbation. Exclusion criteria consisted of impending respiratory failure and corticosteroid administration within the preceding seven days. Interventions : Patients were randomized into either the nebulizer treatment group or one of two MDI-spacer treatment groups (two spacers were evaluated). Each patient received three albuterol treatments administered evenly over one hour. The dose ratio for albuterol by nebulizer versus MDI-spacer was 6.9 :1. Outcome was assessed by comparing the pre- and posttreatment percent predicted respiratory rate and percent predicted peak expiratory flow rate (PEFR) for each patient. Results : Sixty patients were enrolled in the study. All three treatment groups showed significant improvement following albuterol therapy in both percent predicted respiratory rate and percent predicted PEFR. When comparing the three groups against each other in regard to outcome, no significant differences were found in improvement of percent predicted respiratory rate (P = 0.3258) or percent predicted PEFR (P = 0.9362). Conclusion : In a pediatric emergency department setting, aerosolized albuterol delivered by MDI-spacer was equal in effectiveness to nebulization in the acute asthma management of children ≥six years of age.

We exploit a generic instability in the integration of steady, sonic, near-isothermal flows to find the complete transition diagram for recombination fronts (for a model system of equations). The instability requires the integration of the flow equations for speeds between the isothermal and adiabatic sound speeds to be performed with particular care. As a result of this, the previous work of Newman & Axford on the structure of recombination fronts neglected an important class of solution, that of transonic fronts; our method is readily extensible to a more complete treatment of the ionization structure. Future papers will apply these results in models of the structure of ultracompact HII regions., Accepted for publication in MNRAS. LaTeX, 7 pages, 6 Postscript figures. Also available at http://axp2.ast.man.ac.uk:8000/Preprints.html

We showed in earlier work that a clump embedded in tenuous plasma, which is flowing subsonically relative to the clump, will develop a long thin tail whether the gas in the tail behaves adiabatically or isothermally. This paper presents a criterion for determining if viscous dissipation in a tail with result in heating that will cause such a tail to be wide.

Shrinking and swelling clay soils are dominant in the Blackland Prairie of Central Texas and comprise a vast majority of agricultural production land in the area. An agricultural field scale simulation model (EPIC) was applied on six small watersheds located in Riesel, Texas. A non-calibrated model performance evaluation of the runoff, sediment yield, nutrient transport, and crop growth components was completed. Management practices included no-till and conventional till systems. Annual and monthly predicted parameter values were compared with measured data for a 5-year period. Annual comparisons indicate close agreement between means and standard deviations for runoff, erosion, and nitrate-nitrogen. Significant correlation existed between monthly measured and simulated runoff and erosion. Significant correlation for nitrate-nitrogen was present in a majority of the cases studied. Prediction efficiency was significant for all elements except nitrate-nitrogen on two watersheds. The results of this study indicate EPIC’s ability to simulate natural processes without calibration on shrinking and swelling clay soils with varying management practices.

In India, the identity of men who have sex with men (MSM) is closely related to the role taken in anal sex (insertive, receptive or both), but little is known about sexual mixing between identity groups. Both role segregation (taking only the insertive or receptive role) and the extent of assortative (within-group) mixing are known to affect HIV epidemic size in other settings and populations. This study explores how different possible mixing scenarios, consistent with behavioural data collected in Bangalore, south India, affect both the HIV epidemic, and the impact of a targeted intervention. Deterministic models describing HIV transmission between three MSM identity groups (mostly insertive Panthis/Bisexuals, mostly receptive Kothis/Hijras and versatile Double Deckers), were parameterised with behavioural data from Bangalore. We extended previous models of MSM role segregation to allow each of the identity groups to have both insertive and receptive acts, in differing ratios, in line with field data. The models were used to explore four different mixing scenarios ranging from assortative (maximising within-group mixing) to disassortative (minimising within-group mixing). A simple model was used to obtain insights into the relationship between the degree of within-group mixing, R0 and equilibrium HIV prevalence under different mixing scenarios. A more complex, extended version of the model was used to compare the predicted HIV prevalence trends and impact of an HIV intervention when fitted to data from Bangalore. With the simple model, mixing scenarios with increased amounts of assortative (within-group) mixing tended to give rise to a higher R0 and increased the likelihood that an epidemic would occur. When the complex model was fit to HIV prevalence data, large differences in the level of assortative mixing were seen between the fits identified using different mixing scenarios, but little difference was projected in future HIV prevalence trends. An oral pre-exposure prophylaxis (PrEP) intervention was modelled, targeted at the different identity groups. For intervention strategies targeting the receptive or receptive and versatile MSM together, the overall impact was very similar for different mixing patterns. However, for PrEP scenarios targeting insertive or versatile MSM alone, the overall impact varied considerably for different mixing scenarios; more impact was achieved with greater levels of disassortative mixing., Highlights • Different mixing scenarios are explored for 3 groups of role-segregated MSM. • Models show that the mixing scenario affects both R0 and endemic HIV prevalence. • When models are fit to data, predicted HIV trends are unaffected by mixing. • Impact of targeted (but not non-targeted) interventions can be affected by mixing.

Seventy-four primary total hip arthroplasties were performed in sixty-eight patients between August 1990 and September 1991. Clinical assessments were made with use of the Harris hip score and, specifically, the pain component of that score. The preoperative radiographs were digitally quantified for calculation of the so-called canal-to-calcar ratio and the so-called cortical index. The postoperative radiographs were evaluated for the percentage of the cross-sectional area of the femoral canal that was occupied by the prosthesis; subsidence of the prosthesis; and adaptive osseous changes, including hypertrophic cortical remodeling, osteolysis, formation of sclerotic radiolucent lines around the prosthesis, and formation of a pedestal at the tip of the prosthesis. The indication for the arthroplasty was osteoarthrosis in fifty hips (68 per cent), avascular necrosis in fourteen (19 per cent), congenital dysplasia in six (8 per cent), and another diagnosis in four (5 per cent). The average duration of follow-up was thirty-one months (range, eleven to forty-six months). The average Harris hip score (and standard deviation) was 75 +/- 16.8 points (range, 29 to 100 points), and the average score for the pain component was 37 +/- 7.5 points (range, 0 to 44 points). The average canal-to-calcar ratio of the hips was 0.44 (range, 0.32 to 0.74), and the average cortical index was 0.54 (range, 0.33 to 0.66). The average subsidence of the component was 0.6 centimeter (range, 0.0 to 2.3 centimeters). The average fill of the canal was 100 per cent proximally, 97 per cent at the middle of the stem, and 92 per cent distally as measured on the anteroposterior radiographs made immediately postoperatively and 100, 95, and 90 per cent, respectively, as measured on the lateral radiographs. A failure occurred in twenty-one hips (28 per cent) in twenty-one patients, with an average time to failure of 21 +/- 13 months (range, one to forty-four months). The Kaplan-Meier survival estimate (and standard error) for this population was 0.45 +/- 0.11 (confidence interval, 0.67 to 0.23) at forty-four months. The average subsidence of the components that failed was 0.7 centimeter (range, 0.1 to 2.3 centimeters). There was no significant relationship between failure of the component and the age or sex of the patient, the diagnosis, or the side of the operation. Postoperative severity of pain (p = 0.09) or subsidence (p = 0.08) alone did not reach significance for predicting outcome. The Harris hip score alone (p = 0.05), the Harris hip score in combination with subsidence of the femoral component (p = 0.01), and the pain component of the Harris hip score in combination with subsidence of the femoral component (p = 0.01) were all significant for predicting outcome. No other measured radiographic variable was predictive of failure. Despite optimization of the fit of the component within the femoral canal and the percentage of the cross-sectional area of the femoral canal occupied by the component, the clinical results indicated a high rate of failure. Thus, these criteria are not the only requisites for stabilization of these femoral components without cement. On the basis of these data, we have discontinued the use of these intraoperatively customized, non-porous, smooth femoral prosthesis.

Despite an increase in global measles vaccine coverage from under 20% in 1980 to around 80% in 1990, measles remains a major cause of morbidity and mortality world-wide. This paper addresses a number of issues relating to efforts to control measles, namely, (i) at the global level, how might we assess the impact of measles vaccination on the incidence of infection and associated disease, and, (ii), at the strategic level, how can we utilise an understanding of the transmission dynamics of childhood viral infections to aid the design of optimal immunisation programmes? Based on WHO vaccine coverage data, and organising countries according to similarities in demographic and epidemiological parameters, an age-structured model of measles transmission is used to capture the non-linear dynamics of infection and mass vaccination and to generate projections of the impact of measles immunization world-wide. The results provide a crude indication of the percentage reduction in measles cases by year 2000 (compared with no immunization) and suggest an approximately 70% reduction in cases over all ages, and 77% reduction in cases under 5 years (where there is the greatest risk of case fatality); these suggest that WHO targets for 1995 are unlikely to be achieved. In the second part of the paper, examples are given to illustrate the usefulness of a modelling approach in evaluating measles immunization policy. The introduction of MMR vaccine in the UK in 1988 has resulted in measles incidence falling to an all time low and attention has turned to the requirements of elimination. A realistic age structured model, validated using extensive serological data, is used to compare the merits of single or two dose strategies. Based upon recent estimates of vaccine efficacy (90%) and coverage (92% by end of second year of life) it is suggested that a two-dose policy with a pre-school second dose given irrespective of vaccine history is required to prevent the build up of susceptibles to epidemic proportions in the longer term. In a second example, prompted by the success of the campaign approach to polio and measles elimination in Central and South America, simple models are used to explore and quantify the process by which pulse vaccination programmes (i.e. repeated application across a wide age range) act to control transmission.

The authors have used Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Rutherford backscattering spectroscopy (RBS) to characterize lead zirconate-lead titanate (PbZrO{sub 3}-PbTiO{sub 3}) of stoichiometry Pb{sub 1}Zr{sub 0.2}Ti{sub 0.8}O{sub 3} prepared by the sol-gel process. The films were deposited on a sputtered film of Pt and annealed at 700 C for 30 min. Dramatic AES and XPS chemical effects are observed in the film due to charge transfer between Ti and Zr and O; the binding energy of the PZT XPS Ti2p{sub 3/2} (Zr3d{sub 5/2}) orbital shifts +5.2 eV (+4.3 eV) compared to the element and substantial shape changes are observed in the AES Ti(LMM) and O(KLL) peaks. Raman spectroscopy at both 300 and 80 K show that mode frequencies shift upward with decreasing temperature in accord with soft mode theory. Rutherford backscattering spectroscopy (RBS) indicates that the stoichiometry of Pb{sub 1}Zr{sub 0.2}Ti{sub 0.8}O{sub 3} on Pt changes little during 700 C thermal annealing in oxygen because the oxygen from the gas phase replaces the oxygen lost to the substrate by thermal diffusion.

Investigations of materials interactions that complicate the integration of PZT ferroelectric capacitors into CMOS technologies are discussed. These include interactions within the Pt/Ti electrodes structure, the reactions of sol-gel deposited PZT during crystallization with various underlying dielectrics (SiO2, Si3N4, Al2O3, and TiO2), and the impact of other integrated circuit processes on fabricated capacitors.

Many-particle optical lattice clocks have the potential for unprecedented measurement precision and stability due to their low quantum projection noise. However, this potential has so far never been realized because clock stability has been limited by frequency noise of optical local oscillators. By synchronously probing two ^{87}Sr lattice systems using a laser with a thermal noise floor of 1×10(-15), we remove classically correlated laser noise from the intercomparison, but this does not demonstrate independent clock performance. With an improved optical oscillator that has a 1×10(-16) thermal noise floor, we demonstrate an order of magnitude improvement over the best reported stability of any independent clock, achieving a fractional instability of 1×10(-17) in 1000 s of averaging time for synchronous or asynchronous comparisons. This result is within a factor of 2 of the combined quantum projection noise limit for a 160 ms probe time with ~10(3) atoms in each clock. We further demonstrate that even at this high precision, the overall systematic uncertainty of our clock is not limited by atomic interactions. For the second Sr clock, which has a cavity-enhanced lattice, the atomic-density-dependent frequency shift is evaluated to be -3.11×10(-17) with an uncertainty of 8.2×10(-19).

Many-particle optical lattice clocks have the potential for unprecedented measurement precision and stability due to their low quantum projection noise. However, this potential has so far never been realized because clock stability has been limited by frequency noise of optical local oscillators. By synchronously probing two ^{87}Sr lattice systems using a laser with a thermal noise floor of 1×10(-15), we remove classically correlated laser noise from the intercomparison, but this does not demonstrate independent clock performance. With an improved optical oscillator that has a 1×10(-16) thermal noise floor, we demonstrate an order of magnitude improvement over the best reported stability of any independent clock, achieving a fractional instability of 1×10(-17) in 1000 s of averaging time for synchronous or asynchronous comparisons. This result is within a factor of 2 of the combined quantum projection noise limit for a 160 ms probe time with ~10(3) atoms in each clock. We further demonstrate that even at this high precision, the overall systematic uncertainty of our clock is not limited by atomic interactions. For the second Sr clock, which has a cavity-enhanced lattice, the atomic-density-dependent frequency shift is evaluated to be -3.11×10(-17) with an uncertainty of 8.2×10(-19).

Computed tomography (CT) scanning rooms and interventional x-ray facilities with heavy workloads may require the installation of shielding to protect against radiation scattered from walls or ceiling slabs. This is particularly important for the protection of those operating x-ray equipment from within control cubicles who may be exposed to radiation scattered from the ceiling over the top of the protective barrier and round the side if a cubicle door is not included. Data available on the magnitude of this tertiary scatter from concrete slabs are limited. Moreover, there is no way in which tertiary scatter levels can be estimated easily for specific facilities. There is a need for a suitable method for quantification of tertiary scatter because of the increases in workloads of complex x-ray facilities. In this study diagnostic x-ray air kerma levels scattered from concrete and brick walls have been measured to verify scatter factors. The results have been used in a simulation of tertiary scatter for x-ray facilities involving summation of scatter contributions from elements across concrete ceiling slabs. The majority of the ceiling scatter air kerma to which staff behind a barrier will be exposed arises from the area between the patient/x-ray tube and the staff. The level depends primarily on the heights of the ceiling and protective barrier. A method has been developed to allow tertiary scatter levels to be calculated using a simple equation based on a standard arrangement for rooms with different ceiling and barrier heights. Coefficients have been derived for a CT facility and an interventional suite to predict tertiary scatter levels from the workload, so that consideration can be given to the protection options available.

The optical [N I] doublet near 5200 {\AA} is anomalously strong in a variety of emission-line objects. We compute a detailed photoionization model and use it to show that pumping by far-ultraviolet (FUV) stellar radiation previously posited as a general explanation applies to the Orion Nebula (M42) and its companion M43; but, it is unlikely to explain planetary nebulae and supernova remnants. Our models establish that the observed nearly constant equivalent width of [N I] with respect to the dust-scattered stellar continuum depends primarily on three factors: the FUV to visual-band flux ratio of the stellar population; the optical properties of the dust; and the line broadening where the pumping occurs. In contrast, the intensity ratio [N I]/H{\beta} depends primarily on the FUV to extreme-ultraviolet ratio, which varies strongly with the spectral type of the exciting star. This is consistent with the observed difference of a factor of five between M42 and M43, which are excited by an O7 and B0.5 star respectively. We derive a non-thermal broadening of order 5 km/s for the [N I] pumping zone and show that the broadening mechanism must be different from the large-scale turbulent motions that have been suggested to explain the line-widths in this H II region. A mechanism is required that operates at scales of a few astronomical units, which may be driven by thermal instabilities of neutral gas in the range 1000 to 3000 K. In an appendix, we describe how collisional and radiative processes are treated in the detailed model N I atom now included in the Cloudy plasma code., Comment: ApJ in press. 8 pages of main paper plus 11 pages of appendices, with 13 figures and 12 tables

As the main power system interconnections in North America have undergone changes toward the market economic structure, ensuring grid reliability has become the responsible of the Regional Transmission Organizations (RTOs). In market economy, operations planning works side-by-side with the market to achieve grid operation reliability. Operations planning identifies reliability requirements to be enforced in the market clearing processes. It also provides outside-the-market mitigation strategies for system conditions that are not effectively addressed by the market clearing process. The RTO must maintain a correct balance to avoid both the “under planning” and the “over planning”. The former jeopardizes the grid reliability. And the latter results in poor market economic efficiency. This paper reviews the Midwest ISO market and operations planning business processes. It also discusses sensitive areas of operation where the correct balance is harder to achieve, but its success would significantly impact the market economics, in terms of both operation cost and pricing.

In order to reliably operate the bulk electric grid generators are expected to meet certain reactive power requirements depending on the system they operate in. In the past reactive power requirements were tailored to the capabilities of synchronous generators. Variable generators such as wind and solar plants were in the past small enough relative to the entire system that they were not required to supply voltage support to the grid. As the penetration of renewable resources have grown beyond insignificance, it is now the trend that variable generators connected to transmission and subtransmission grids should be required to provide reactive power support. The goal of this paper is to educate the reader on the current state of reactive power requirements for variable generation. This paper discusses reactive power requirements from various regions across the world with a focus on those in North America.

We describe recent experimental progress with the JILA Sr optical frequency standard, which has a systematic uncertainty at the 10−16 fractional frequency level, currently limited by frequency shifts due to atomic interactions and room temperature blackbody radiation (BBR). We will discuss systematic measurements of collisional shifts and provide a complete theory to understand these interaction effects at the 10−17 level. We will also discuss plans to interrogate atoms inside a cryogenic shield region to eliminate BBR shifts. We will present our recent successful efforts in improving the laser stability with the aim for the JILA Sr standard to reach the standard quantum measurement limit and achieve record levels of stability. Finally, a second Sr optical lattice clock has been constructed at JILA, and we will discuss the results of intercomparison experiments between the two standards.

The specification of shielding for CT facilities in the UK and many other countries has been based on isodose scatter curves supplied by the manufacturers combined with the scanner's mAs workload. Shielding calculations for radiography and fluoroscopy are linked to a dose measurement of radiation incident on the patient called the kerma-area product (KAP), and a related quantity, the dose-length product (DLP), is now employed for assessment of CT patient doses. In this study the link between scatter air kerma and DLP has been investigated for CT scanners from different manufacturers. Scatter air kerma values have been measured and scatter factors established that can be used to estimate air kerma levels within CT scanning rooms. Factors recommended to derive the scatter air kerma at 1 m from the isocentre are 0.36 µGy (mGy cm)(-1) for the body and 0.14 µGy (mGy cm)(-1) for head scans. The CT scanner gantries only transmit 10% of the scatter air kerma level and this can also be taken into account when designing protection. The factors can be used to predict scatter air kerma levels within a scanner room that might be used in risk assessments relating to personnel whose presence may be required during CT fluoroscopy procedures.

In a prospective study, spiral-acquisition computed tomography (SACT) of the thorax was evaluated in 104 patients with extrathoracic malignancy and suspected pulmonary metastases, and was directly compared with conventional computed tomography (CCT) in 23 patients. The following parameters were assessed: lesion detectability; the effect on lesion detectability of reconstruction of scans at 5 mm and 10 mm slice increments; breathing artefact and slice misregistration. The radiation dose of the two techniques was measured using thermoluminescent dosimeters placed within an anthropomorphic chest phantom, and the visibility of simulated metastases inserted into the phantom was also compared using CCT, standard SACT and SACT with pitch greater than 1.0. Where metastases were present, SACT scans showed significantly better lesion detectability than CCT scans (p < 0.001). Image reconstruction of SACT data at 5 mm increments conferred no significant advantage in lesion detectability over 10 mm increment reconstructions. Compared with CCT, SACT scans showed reduced breathing artefact, and a complete absence of slice misregistration (p < 0.01). Phantom measurements of radiation dose and resolution were similar for both techniques. Increasing the pitch of the spiral in SACT caused only a small decrease in phantom resolution, but with the advantage of a reduction in the radiation dose. Spiral-acquisition CT is superior to conventional CT for the assessment of pulmonary metastatic disease.

This paper provides a review and justification of the minimum data needed to characterize soils for hazardous waste site assessments and to comply with the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). Scientists and managers within the regulatory agency and the liable party need to know what are the important soil characteristics needed to make decisions about risk assessment, what areas need remediation and what remediation options are available. If all parties involved in characterizing a hazardous waste site can agree on the required soils data set prior to starting a site investigation, data can be collected in a more efficient and less costly manner. Having the proper data will aid in reaching decisions on how to address concerns at, and close-out, hazardous waste sites. This paper was prepared to address two specific concerns related to soil characterization for CERCLA remedial response. The first concern is the applicability of traditional soil classification methods to CERCLA soil characterization. The second is the identification of soil characterization data type required for CERCLA risk assessment and analysis of remedial alternatives. These concerns are related, in that the Data Quality Objective (DQO) process addresses both. The DQO process was developed in part to assist CERCLA decision-makers in identifying the data types, data quality, and data quantity required to support decisions that must be made during the remedial investigation/feasibility study (RI/FS) process. Data Quality Objectives for Remedial Response Activities: Development Process (US EPA, 1987a) is a guidebook on developing DQOs. This process as it relates to CERCLA soil characterization is discussed in the Data Quality Objective Section of this paper.

The analytical capabilities of ICP-AES (ICP) and deuteron activation (associated with prompt gamma-rays and delayed X-rays) for the determination of certain transition metals, were investigated. The sensitivities of the three methods are given, and the general applicability of each technique is evaluated. In the case of ICP, numerical data were obtained from aqueous solutions containing digested plant material. These experimental results were assessed against minimum detectable limits attained in relevant solid matrices that were subjected to prompt gamma-ray and delayed X-ray spectrometry using 5 MeV 2H+ ions. The analytically useful lines originated mainly from (d,p) and (d,n) reactions. The potential of the three techniques for routine analysis is discussed and detailed methodologies are presented.

The analytical potential of ICP-AES (ICP) and 3He+-activation for the determination of boron was examined. The paper compares ICP-levels of B, obtained from aqueous solutions containing digested plant material, with minimum detectable limits attained in solid matrices that were subjected to prompt gamma-ray analysis using 2 MeV 3He+ ions. The analytically useful gamma-rays originated mainly from (3He,p) and (3He,a) reactions on 11B and Coulomb excitation of 10B. The numerical capabilities of the two techniques for such measurements are discussed, and detailed methodologies and possible difficulties are presented.

This paper presents a numerical study of a reshocked turbulent mixing layer using high-order accurate Implicit Large-Eddy-Simulations (ILES). Existing theoretical approaches are discussed, and the theory of Youngs (detailed in Ref. 1) is extended to predict the behaviour of a reshocked mixing layer formed initially from a shock interacting with a broadband instability. The theory of Mikaelian2 is also extended to account for molecular mixing in the single-shocked layer prior to reshock. Simulations are conducted for broadband and narrowband initial perturbations and results for the growth rate of the reshocked layer and the decay rate of turbulent kinetic energy show excellent agreement with the extended theoretical approach. Reshock causes a marginal decrease in mixing parameters for the narrowband layer, but a significant increase for the broadband initial perturbation. The layer properties are observed to be very similar post-reshock, however, the growth rate exponent for the mixing layer width is higher in the broadband case, indicating that the reshocked layer still has a dependence (although weakened) on the initial conditions. These results have important implications for Unsteady Reynolds Averaged Navier Stokes modelling of such instabilities.

Using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses, we explore the optical Feshbach resonance effect in an ultracold gas of bosonic $^{88}\mathrm{Sr}$. A systematic measurement of three resonances allows precise determinations of the optical Feshbach resonance strength and scaling law, in agreement with coupled-channel theory. Resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas. Optical Feshbach resonance could be used to control atomic interactions with high spatial and temporal resolution.

Early theories of active galactic nuclei concentrated on the physics of gas in the region dominated by the gravitational potential of a central black hole. Recently, attention has increasingly focussed on the role of individual stars in the environment of an active galactic nucleus. We investigate some aspects of accretion disc structure in active galactic nuclei containing a gravitationally significant stellar component. Because such discs radiate the gravitational binding energy released locally by viscous processes, their spectra probe the mass distributions of the regions where the discs reside

The effect of radiologist grade on patient dose during fluoroscopic barium studies was assessed over a one-year period in a large teaching hospital using area–kerma measurements made with a Diamentor M2 system. The number of studies investigated was 164 for barium swallows, 274 for barium meals and 1288 for barium enemas. The patient's AP thickness was assessed at the abdominal level from a formula combining the patient's estimated height and weight. For each study there was significant change in AP thickness as a function of radiologist grade. For all barium studies there was a trend for both the screening time and the patient dose to fall to a minimum for the grades third-year registrar/first-year senior registrar. From this group to consultant level the dose and screening time rose.

The effect of weather variation on pesticide losses was estimated with the Erosion-Productivity Impact Calculator (EPIC) model. Weather variations had little effect on pesticide loss from a hypothetical site near Memphis, TN, but the effect was more dramatic and in the expected direction at Des Moines, IA. Atrazine losses at Des Moines were reduced by lowering relative humidity or rainfall intensity. Increasing the CO2 level from 300 to 660 ppm slightly increased atrazine losses. Results from these two sites are very limited and only serve to demonstrate modeling potential for addressing weather/pesticide problems. Further, more comprehensive studies are needed to better estimate pesticide loss sensitivity to weather variation.

In order to assess the feasibility and outcome of using prehospital thrombolysis in acute myocardial infarction in a rural community, we performed an open randomized study of patients with symptoms of acute myocardial infarction of less than 6 hours. One hundred and forty-five patients with acute myocardial infarction were allocated to receive IV streptokinase prehospital by means of a mobile coronary care unit (MCCU) (n = 43) or to receive IV streptokinase in hospital (n = 102). The mean delay time to treatment was 138 minutes (MCCU group) and 172 minutes (hospital group) (p less than 0.02). Reperfusion time was 88 minutes for the MCCU group and 92 minutes for the hospital group. Mortality at 14 days was 2.3% for the MCCU group and 11.7% for the hospital group (p less than 0.05). Six month mortality was 4.9% for the MCCU group and 17.3% for the hospital group (p = 0.03). Mortality at 1 year was 6.1% for the MCCU group and 20.0% for the hospital group (p = 0.04). There were no significant adverse events in either treatment group. Thus, prehospital thrombolysis by streptokinase is feasible and allows significant reduction in the delay time to treatment initiation. There are encouraging improvements in both short- and long-term survival with no apparent reduction in safety profile.

This paper is concerned with the question of finding sets of similar micro-level industries that can be grouped to obtain a smaller set of macro-level industries. We argue that factor analysis based on the Leontief inverse is a promising approach when multiple objectives of classification must be taken into account, provided that the cosine, rather than the correlation coefficient, is adopted as the measure of similarity. We apply this approach to the 1967 US input–output table because that table has been used by researchers experimenting with alternative classification methods.

Results of capacitance–voltage measurements are reported for metal–oxide–semiconductor capacitors fabricated using the 4H polytype of silicon carbide doped with either nitrogen (n) or aluminum (p). Annealing in nitric oxide after a standard oxidation/reoxidation process results in a slight increase in the defect state density in the lower portion of the band gap for p-SiC and a significant decrease in the density of states in the upper half of the gap for n-SiC. Theoretical calculations provide an explanation for these results in terms of N passivating C and C clusters at the oxide–semiconductor interface.