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Continuous System Simulation (CSS) is a powerful way to study the behaviour of differential-algebraic equation models. Differential-algebraic equation modelling goes back to Newton and works well for models of e.g. physical systems where stochasticity plays almost no role, and where only a single attribute of an object is studied over time. However, when results from a deterministic CSS model are compared with results from a Discrete Event Simulation (DES) model, they are often inconsistent. The reasons behind this CSS-DES inconsistency are nowadays well understood. In this paper, we demonstrate that a CSS model can contain both continuous state variables (compartments) that change continuously over time and discrete state variables (also compartments) that model discrete entities and change by integer amounts. In both cases, the time-slicing method is used to advance time. Furthermore, stochasticity can and should play the same role in CSS as it does in DES. This paper first explains how a well-defined conceptual model can be stepwise transformed in a consistent way into a CSS model. These transformation steps provide insights into how to construct a consistent CSS model. In short, this is about preserving uncertainties, attributes and dynamic properties. An additional benefit of this approach is that continuous and discrete sub-models can interact within the same model, without having to combine different types of simulation languages, types of time handling and incongruent concepts. To facilitate the use and understanding of stochastic CSS, this paper is also intended to serve as a guide to performing consistent CSS modelling and simulation. Furthermore, an open source tool for collecting and analyzing the outputs from a stochastic CSS model and analyzing and presenting the results in statistical form is also developed and made available to the reader.

This paper outlines the fundamentals of a consistent theory of numerical modelling of a population system under study. The focus is on the systematic work to construct an executable simulation model. There are six fundamental choices of model category and model constituents to make. These choices have a profound impact on how the model is structured, what can be studied, possible introduction of bias, lucidity and comprehensibility, size, expandability, performance of the model, required information about the system studied and its range of validity. The first choice concerns a discrete versus a continuous description of the population system under study—a choice that leads to different model categories. The second choice is the model representation (based on agents, entities, compartments or situations) used to describe the properties and behaviours of the objects in the studied population. Third, incomplete information about structure, transitions, signals, initial conditions or parameter values in the system under study must be addressed by alternative structures and statistical means. Fourth, the purpose of the study must be explicitly formulated in terms of the quantities used in the model. Fifth, irrespective of the choice of representation, there are three possible types of time handling: Event Scheduling, Time Slicing or Micro Time Slicing. Sixth, start and termination criteria for the simulation must be stated. The termination can be at a fixed end time or determined by a logical condition. Population models can thereby be classified within a unified framework, and population models of one type can be translated into another type in a consistent way. Understanding the pros and cons for different choices of model category, representation, time handling etc. will help the modeller to select the most appropriate type of model for a given purpose and population system under study. By understanding the rules for consistent population modelling, an appropriate model can be created in a systematic way and a number of pitfalls can be avoided.

The ARIANNA experiment seeks to observe the diffuse flux of neutrinos in the 10^8 - 10^10 GeV energy range using a grid of radio detectors at the surface of the Ross Ice Shelf of Antarctica. The detector measures the coherent Cherenkov radiation produced at radio frequencies, from about 100 MHz to 1 GHz, by charged particle showers generated by neutrino interactions in the ice. The ARIANNA Hexagonal Radio Array (HRA) is being constructed as a prototype for the full array. During the 2013-14 austral summer, three HRA stations collected radio data which was wirelessly transmitted off site in nearly real-time. The performance of these stations is described and a simple analysis to search for neutrino signals is presented. The analysis employs a set of three cuts that reject background triggers while preserving 90% of simulated cosmogenic neutrino triggers. No neutrino candidates are found in the data and a model-independent 90% confidence level Neyman upper limit is placed on the all flavor neutrino+antineutrino flux in a sliding decade-wide energy bin. The limit reaches a minimum of 1.9x10^-23 GeV^-1 cm^-2 s^-1 sr^-1 in the 10^8.5 - 10^9.5 GeV energy bin. Simulations of the performance of the full detector are also described. The sensitivity of the full ARIANNA experiment is presented and compared with current neutrino flux models., 22 pages, 22 figures. Published in Astroparticle Physics

International audience; Silicon tracking detectors operated at high luminosity collider experiments pose a challenge for current and future readout systems regarding bandwidth, radiation, space and power constraints. With the latest developments in wireless communications, wireless readout systems might be an attractive alternative to commonly used wired optical and copper based readout architectures.The WADAPT group (Wireless Allowing Data and Power Transmission) has been formed to study the feasibility of wireless data transmission for future tracking detectors. These proceedings cover current developments focused on communication in the 60 GHz band. This frequency band offers a high bandwidth, a small form factor and an already mature technology. Motivation for wireless data transmission for high energy physics application and the developments towards a demonstrator prototype are summarized. Feasibility studies concerning the construction and operation of a wireless transceiver system have been performed. Data transmission tests with a transceiver prototype operating at even higher frequencies in the 240 GHz band are described. Data transmission at rates up to 10 Gb/s have been obtained successfully using binary phase shift keying.

A dynamic population system is often modelled by a deterministic difference equation model to obtain average estimates. However, there is a risk of the results being distorted because unexplained (random) variations are left out and because entities in the population are described by continuous quantities of an infinitely divisible population so that irregularly occurring events are described by smooth flows. These distortions have many aspects that cannot be understood by only regarding a deterministic approach. However, the reasons why a deterministic model may behave differently and produce biased results become visible when the deterministic model is compared with a stochastic model of the same structure. This paper focuses first on demographic stochasticity, i.e. stochasticity that refers to random variations in the occurrence of events affecting the state of an individual, and investigates the consequences of omitting this by deterministic modelling. These investigations reveal that bias may be strongly influenced by the type of question to be answered and by the stopping criterion ending the analysis or simulation run. Two cases are identified where deterministic models produce unbiased state variables: (1) Dynamic systems with stable local linear dynamics produce unbiased state variables asymptotically, in the limit of large flows; and (2) linear dynamic systems produce unbiased state variables as long as all state variables remain non-negative in both the deterministic and the stochastic models. Both cases also require the question under study to be compatible with a solution over a fixed time interval. Stochastic variability of initial values between simulation runs because of uncertainty or lack of information about the initial situation is denoted initial value stochasticity. Elimination of initial value stochasticity causes bias unless the model is linear. It may also considerably enlarge bias from other sources. Unknown or unexplained variations from the environment (i.e. from outside the borders of the studied system) enter the model in the form of stochastic parameters. The omission of this environmental stochasticity almost always creates biased state variables. Finally, even when a deterministic model produces unbiased state variables, the results will be biased if the output functions are not linear functions of the state variables.

Exclusive measurements of the pp -> pp pi(0)pi(0) reaction have been performed at CELSIUS/WASA at energies from threshold up to T-p = 1.3 GeV. Total and differential cross sections have been obt ...

The cross sections of the pd -> 3He eta, pd -> 3He pi0 pi0 pi0 and pd -> 3He pi+ pi- pi0 reactions have been measured at beam kinetic energies T_p= 1360 MeV and T_p= 1450 MeV using the CELSIUS/WASA detector setup. At both energies, the differential cross section dsigma/dOmega of the eta meson in the pd -> 3He eta reaction shows a strong forward-backward asymmetry in the CMS. The ratio between the pd -> 3He pi+ pi- pi0 and the pd -> 3He pi0 pi0 pi0 cross sections has been analysed in terms of isospin amplitudes. The reconstructed invariant mass distributions of the pi-pi, 3He-pi and 3He-2pi systems provide hints on the role of nucleon resonances in the 3pi production process.

Exclusive measurements of the reaction pp -> d pi(+)pi(0) have been carried out at T-p = 1.1 GeV at the CELSIUS storage ring using the WASA detector. The isovector pi(+)pi(0) channel exhibits no ...

The cross section for the pd -> He-3 eta pi(0) reaction has been measured at a beam energy of 1450 MeV using the WASA detector at the CELSIUS storage ring. The He-3 was detected in coincidence with four photons from the decays of the two mesons. The data indicate that the production mechanism involves the formation of the Delta(1232) isobar. Although the beam energy does not allow the full peak of this resonance to be seen, the invariant mass distributions Of all three pairs of final particles are well reproduced by a phase space Monte Carlo simulation weighted with the p-wave factor of the square of the pi(0) momentum in the He-3 pi(0) system.

The results from the first kinematically complete measurement of the reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar ππ-invariant mass ...

The two-pion production in pp-collisions has been investigated in exclusive measurements from threshold up to Tp = 1.36 GeV . Total and differential cross sections have been obtained for the channels pnπ+π0, ppπ+π-, ppπ0π0 and also nnπ+π+. For intermediate incident energies Tp > 1 GeV , i.e. in the region, which is beyond the Roper excitation but at the onset of ΔΔ excitation the total ppπ0π0 cross section falls behind theoretical predictions by as much as an order of magnitude near 1.2 GeV, whereas the nnπ+π+ cross section is a factor of five larger than predicted. A model-unconstrained isospin decompostion of the cross section points to a significant contribution of an isospin 3/2 resonance other than the Δ(1232). As a possible candidate the Δ(1600) is discussed.

The tensor polarisation of ω mesons produced in the p d → He 3 ω reaction has been studied at two energies near threshold. The He 3 nuclei were detected in coincidence with the π 0 π + π − or π 0 γ decay products of the ω . In contrast to the case of ϕ -meson production, the ω mesons are found to be unpolarised. This brings into question the applicability of the Okubo–Zweig–Iizuka rule when comparing the production of vector mesons in low energy hadronic reactions.

Population models concern collections of discrete entities such as atoms, cells, humans, animals, etc., where the focus is on the number of entities in a population. Because of the complexity of such models, simulation is usually needed to reproduce their complete dynamic and stochastic behaviour. Two main types of simulation models are used for different purposes, namely micro-simulation models, where each individual is described with its particular attributes and behaviour, and macro-simulation models based on stochastic differential equations, where the population is described in aggregated terms by the number of individuals in different states. Consistency between micro- and macro-models is a crucial but often neglected aspect. This paper demonstrates how the Poisson Simulation technique can be used to produce a population macro-model consistent with the corresponding micro-model. This is accomplished by defining Poisson Simulation in strictly mathematical terms as a series of Poisson processes that generate sequences of Poisson distributions with dynamically varying parameters. The method can be applied to any population model. It provides the unique stochastic and dynamic macro-model consistent with a correct micro-model. The paper also presents a general macro form for stochastic and dynamic population models. In an appendix Poisson Simulation is compared with Markov Simulation showing a number of advantages. Especially aggregation into state variables and aggregation of many events per time-step makes Poisson Simulation orders of magnitude faster than Markov Simulation. Furthermore, you can build and execute much larger and more complicated models with Poisson Simulation than is possible with the Markov approach.

The cross section for direct neutral and charged three pion production in pp interactions was measured at excess energies in the range 160–216 MeV. That comprises the first measurement of the pp→ppπ0π0π0 reaction and the direct comparison with the pp→ppπ+π−π0 process. The experiment was performed above the η meson production threshold and the cross section could be directly normalized to the cross section of the pp→ppη reaction, with the η decaying into 3 pions. Since the same final states are selected, the measurement has a low systematical error. The measured cross section ratio σ(pp→ppπ+π−π0)/σ(pp→ppπ0π0π0) is compared to predictions of dominance of different isobars in the intermediate state.

The reaction pn → dπ0π0 constitutes the most fundamental system for the study of the ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of the ππ system in double-pionic fusion to nuclear bound states. The first exclusive measurements of this reaction have now been carried out at CELSIUS-WASA. They exhibit a striking low-mass enhancement in the ππ invariant mass spectrum, prove it to be a σ-channel phenomenon and falsify conventional theoretical models, which predict an associated high-mass enhancement not present in the new exclusive data. In the kinematically complete data sample we observe a ΔΔ excitation, where the interaction between the two Δ obviously plays a crucial role for the generation of the ππ low-mass enhancement.

At CELSIUS-WASA the two-pion production in proton-proton collisisons has been measured exclusively from threshold up to the energy regime, where both of the collision partners are expected to be excited to the Δ state. The measurements constitute the first kinematically complete data samples of solid statistics in this energy range. Most of the data have been obtained for the π+π- and π0π0channels. Whereas at near-threshold energies the differential distributions can be succesfully explained by chiral dynamics and Roper excitation, respectively, the data for the π+π- channel in the ΔΔ region can be described only, if the special configuration (ΔΔ)0+ is assumed. The data for the π0π0 channel moreover exhibit a low-mass enhancement in the π0π0 invariant mass spectrum, which is reminiscent of the ABC-effect found in double-pionic fusion to light nuclei.

The ABC effect - a puzzling threshold enhancement in the ππ invariant mass spectrum of double-pionic fusion to nuclear bound states - has been investigated since 40 years by inclusive measurements without providing a conclusive interpretation. First exclusive measurements to this topic have now been carried out at CELSIUS-WASA. They confirm a huge ππ threshold enhancement, prove it to be of scalar-isoscalar nature, i.e., a σ-channel phenomenon and reveal the theoretically predicted high-mass enhancement in inclusive spectra to be of πππ rather than of ππ nature - falsifying thus corresponding model predictions for the ABC effect. From the kinematically complete data samples we infer that the interaction between the two Δ particles created in this process is of crucial importance.

The reaction pd -> He-3 eta at threshold was used to provide a clean source of eta mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay eta -> pi(+)pi( ...

Exclusive measurements of the reactions p d → He 3 π + π − and p d → He 3 π 0 π 0 have been carried out at T p = 0.893 GeV at the CELSIUS storage ring using the WASA detector. The π + π − channel evidences a pronounced enhancement at low invariant ππ masses—as anticipated from previous inclusive measurements of the ABC effect. This enhancement is seen to be even much larger in the isoscalar π 0 π 0 channel. The differential distributions prove this enhancement to be of scalar–isoscalar nature. ΔΔ calculations give a good description of the data, if a boundstate condition is imposed for the intermediate ΔΔ system.

A simulation tool has been developed for the analysis of the performance of an X-ray imaging hybrid pixel detector. The photon transport and charge collection were simulated with the aid of the Monte Carlo based code GEANT and the readout signal processing was simulated in a program written in the LabView programming environment. Results of the spatial frequency-dependent detective quantum efficiency are presented and the influence of charge sharing, the threshold settings, level of exposure, the noise sources on the detector performance are studied. The detector was found to operate quantum limited down to an exposure of 0.08 μGy, below which it is limited by the readout noise. The threshold setting has a strong influence on both the efficiency and the spatial resolution due to charge sharing, and a compromise between the two is necessary. The optimized threshold value corresponds to half of the mean energy of the input spectrum.

The pp→ppx(x=γγ, π0π0, π+π-) reactions have been measured at CELSIUS in the energy range Tp=775-1360 MeV using the WASA 4π detector with hydrogen pellet target. Close to threshold the ppπ+π- data are in accordance with the Roper resonance concept and/or a dynamic formation of the σ meson. At higher energies the formation of the ΔΔ system becomes increasingly dominant. The ppπ0π0 channel basically shows similar features, however, develops a peculiar enhancement at small invariant masses Mπ0π0 - in resemblance of Bose-Einstein correlations. Alternatively, the enhancement could be also indicative of a (dynamic) isospin breaking due to ππ rescattering in the σ channel. The latter is favored by the results on pd→3 He x (x=π0π0, π+π-), where the observed π0π0 enhancements are still much larger. In the γγ channel a line at Mγγ=2mπ is observed. The possible nature of this line is discussed.

A semiconductor hybrid pixel detector for dynamic X-ray imaging is developed. The detector, called DIXI, consists of a semiconductor sensor mounted onto a readout chip. A detector module with a 500 μm silicon sensor is currently being assembled with the use of anisotropic conductive film as interconnection between the sensor and the readout chip. The basic building block of the detector is 1 cm 2 in size and consists of 992 square pixel cells arranged in 31 columns and 32 rows. The pixels have a side of 270 μm . The readout chip is capable of performing photon counting and has an externally adjustable threshold. The readout chip has been characterised by charge injection in the absence of a sensor. The threshold dispersion is measured to 365 e− for hole collection. Even if the chip was not originally designed for electron collection a threshold dispersion of 1650 e− has been achieved. Two counters are implemented in every single pixel cell and the threshold can be changed from one image to the next in order to select different parts of the X-ray spectrum.

A pixel readout chip for medical X-ray imaging has been developed. It is to be used in a hybrid pixel detector, where it is connected to a semiconductor sensor. A single chip consists of 992 square pixels arranged in 31 columns and 32 rows. Each pixel has a side of 270 μm and comprises a preamplifier, shaper, discriminator and two counters. The readout chip operates as a photon counter. The implementation of two counters in every single pixel cell is a design solution that makes it possible to acquire two images very close in time and under different conditions. The readout chip has been characterised in the absence of a sensor by using charge injection. Results are presented on basic functionality, threshold dispersion and the capability to perform photon counting.

Linear systems theory is used for the numerical assessment of the detective quantum efficiency (DQE) of the hybrid semiconductor pixel detector DIXI. The Monte Carlo based code GEANT is used to simulate the photon transport in the sensor, charge transport modeling is treated analytically and the readout chip is simulated using PSPICE. The DQE for two differently shaped X-ray spectra of the same quality and for different operational conditions of the readout chip regarding the discrimination level are computed in order to validate the model. The model described in this paper can be adopted for optimizing the detector.

Poisson simulation is an extension of continuous system simulation whereby randomness is modeled as opposed to just adding noise. This article treats how Poisson simulation can be used for modeling queuing systems. The focus is on the implementation of queues in Poisson simulation and the connections to queuing theory. This approach also has theoretical and practical implications. Dynamic and stochastic systems, especially when queues are involved, are often treated by discrete event simulation using a microscopic view in which individual entities are modeled. Poisson simulation makes it possible to handle many such systems on a macroscopic level using aggregated states. It is therefore interesting to compare these approaches. Parallel approaches can then be sketched with discrete event simulation in one branch and Poisson simulation in the other. A fundamental difference between the approaches is whether one prefers to base a model on individual, distinguishable entities or on lumped entities.

The π0π0 production in pp -collisions has been investigated in exclusive and kinematically complete measurements from threshold up to Tp = 1.4 GeV . For incident energies Tp > 1 GeV , i.e. in the region beyond the Roper excitation, the ΔΔ excitation process takes over. The data are well explained by the t-channel ΔΔ process dominated by pion exchange. There is no low-mass enhancement (ABC effect) in the π0π0-invariant mass distribution beyond that given by the conventional t-channel ΔΔ process. This is also true for the limiting case, where the protons are in the quasi-bound 2 He state.

The discovery of a charged Higgs boson (H±) would be a clear indication for physics beyond the Standard Model. This thesis describes searches for charged Higgs bosons with the ATLAS experiment at CERN’s Large Hadron Collider (LHC). The first data collected during the LHC Run 1 is analysed, searching for a light charged Higgs boson (mH±

The imaging detector DIXI is a solid state hybrid pixel detector for 2D real-time imaging. A prototype detector has been constructed at the Uppsala University. Image quality parameters have been assessed by means of simulations in order to estimate the imaging capabilities of the detector. The MC simulations concern the sensor responses to mono-energetic and poly-energetic X-ray sources in terms of the charge carrier distribution and modulation transfer function. Different sensor materials and pixel sizes are included into the model and compared.

Low-energy spectator protons (p s ) from quasi-free proton–neutron interactions on deuterium have been measured for the pd→dπ 0 p s and pd→pnπ 0 p s reactions at the CELSIUS storage ring of the The Svedberg Laboratory. The experiment used 320 MeV protons incident on a deuterium cluster-jet target. The spectator protons were detected inside the scattering chamber using a silicon detector system which is compatible with a high vacuum. The low target density allows the spectator proton emerge without undergoing significant secondary scattering. Its measurement is therefore a useful tag upon such reactions, allowing cross-sections for quasi-free reactions to be deduced at well-defined centre-of-mass energies. The comparison with the simulation for the pd→dπ 0 p s reaction shows that the energy dependence of the pn→dπ 0 cross-section can be extracted near the threshold. The method greatly improves the experimental resolution achievable in quasi-free p–n reaction studies.

In continuous systems simulation a model is built as a system of differential equations. An implicit assump tion is that the number of items is so large that the changes can then be regarded as continuous. How ever, many systems can be modeled by differential equations when the numbers involved are moderately large. Such systems show stochastic variations that can be described in terms of events per time unit. If the events happen one at a time, and if the number of events during the interval is independent of both the number of past events and the times these events oc curred, we have a Poisson process. The system's variations can be modeled by replacing the flow to or from a state during the integration step with a Pois son probability. This not only adds variations to the model, but can also reveal system properties not cov ered by continuous system simulation. Furthermore, the "intensity parameter" controlling the flow may vary over time without further problems.

Measurements of the differential cross sections of the pp --> pp pi(0) reaction at 310, 320, 340, 360, 400 and 425 MeV have been carried out at the CELSIUS storage ring in Uppsala. An attempt ha ...

The angular distribution of neutral pions produced in the pp --> pp pi(0) reaction has been measured at a beam energy of 310 MeV. Significant deviations from isotropy are found, which increase f ...

Dibaryons, forbidden by mass to decay into NN π channel and by quantum numbers into NN channel, may still have escaped detection. In fact, recently an observation of a narrow dibaryon (D) with the mass close to 1920 MeV was reported in the process pp → γγ + X . This dibaryon should also appear in the proton-proton bremsstrahlung data from measurements at 200 and 310 MeV, which have been carried out at the CELSIUS storage ring in Uppsala. From these data upper limits of 10 and 3 nb are obtained for the dibaryon production cross section (at 95% confidence level) for the two energies, respectively.

The WASA project at the CELSIUS storage ring is being prepared for high-luminosity experiments to study rare decays of light mesons, in particular the η meson. The CELSIUS ring together with the newly developed pellet target will serve as an efficient η factory.

Monte-Carlo simulations have been performed for the purpose of investigating the energy discriminating feature of a semiconductor hybrid pixel detector at diagnostic energies. Part of the evalution was performed using synthetic images obtained from the simulated data.

Huge differences in incidence rates of invasive cervical cancer occur among populations. These differences reflect the influences of both etiological environmental factors and removal of precursor lesions detected upon screening. The purposes of this article are (i) to describe similarities and differences in the shapes and magnitudes of age-specific incidence rates of invasive cervical cancer before screening had an effect, (ii) to provide baseline data for further global study of screening effects, and (iii) to provide baseline incidence data for the design of optimal screening programs. To eliminate the impact of screening effects, we have selected age-specific incidence rates from times when and from populations in which screening was insignificant. The selected rates were suitably scaled and compared regarding age at onset of increase in incidence, age at peak incidence, and rate of subsequent decline. Despite a 16-fold difference in incidence rates, all curves had the same basic structure, with an increase to a peak followed by a decline or a plateau. Although all populations but one had an onset around age 25, 7 European countries showed an earlier peak age (mean = 46 vs. 59) and a more rapid decline after the peak than most other populations. The common basic shape of the age-specific incidence curve, overall, suggests a relatively similar development of invasive cervical cancer in different populations. These results illustrate the underlying similarities in the markedly different age-specific incidence rates of invasive cervical cancer. They also provide a basis for studying screening effects and for optimizing screening programs in specific geographic areas.

A design of a fast multiplicity trigger system, using programmable logic devices is presented. The system has a pulse width updating feature and the multiplicity threshold level may be set in a wide range (1–120), manually or remotely via an I 2 C link. The total delay is better than 100 ns. The logical algorithms are also described in detail.

The status of the search for NN-decoupled resonances in the πNN-system is reviewed. After a short survey on the history of dibaryon searches reactions suitable for detecting such resonances are discussed. Special emphasis is put on the pionic double charge exchange, where recently evidence for the signature of a narrow πNN resonance, called d ′, with I ( J P ) = even (0 − ) and m = 2.06 GeV has been quoted. Further reactions discussed in this context are the pion photoproduction on the deuteron and the two-pion production in nucleon-nucleon collisions.

The pp → ppη reaction has been measured at six energies close to threshold, from 1258 MeV to 1352 MeV, using an internal cluster gas jet target in the CELSIUS storage ring. The η is detected through its decay photons, in an array of CsI detectors, and the forward-going protons are detected in a plastic scintillator spectrometer. A complete event reconstruction is obtained at the higher energies in the measured interval. The new data, together with earlier data, give an accurate determination of the energy dependence close to threshold. The influence of the η-proton FSI is seen in the total cross section data as well as in a Dalitz plot of the η-p invariant mass distributions.

Cervical cancer incidence and mortality can be reduced by removal of precursor lesions detected at cytological screening. Organised screening, i.e. regular invitation of defined target groups, is generally considered more effective than opportunistic screening. The latter method however, is predominant in most settings. There is no scientific basis for advocating one type of screening or the other. Our aim was to compare the two types and to analyse their efficiency. We analysed 466,275 smears taken in an open cohort of 118,890 women during 1969-88. A computerised database permitted standardised classification of all smears and complete ascertainment of cancer in situ through record linkage. The number of in situ cancers detected per 1000 smears, the detection ratio, was used as an outcome measure both in univariate analyses and in multivariate logistic regression models. Cancer in situ was detected in 1076 women in the study cohort, with a detection ratio of 3.0 at organised and 2.1 at opportunistic screening, yielding an unadjusted odds ratio of 0.69 (95% CI 0.61-0.79). After adjustment for age and time period, the probability of detecting cancer in situ was around 25% higher with opportunistic than with organised screening (OR = 1.26; 95% CI 1.09-1.46). This difference in favour of opportunistic screening was most pronounced in the first 10 year period and disappeared during the last decade. The difference in efficiency between organised and opportunistic screening in the detection of cancer in situ was slight, if any. The dogma that organised screening is significantly more efficient than the opportunistic type needs reconsideration.

Supplemental Instruction (SI) is today a well known academic assistance program, providing help for students in “difficult” courses at colleges and universities. Little attention has been paid however to the possibility of also implementing the SI program in upper secondary school. In this study we present qualitative results from such an SI program in a Swedish setting. Here, students from the faculty of engineering at Lund University, act as SI leaders at eleven upper secondary schools in the local region, in subjects such as math, physics and chemistry. The main conclusion is that the SI methodology also seems to work in an upper secondary school environment. The students who attend SI regularly appear to obtain new study strategies to increase their understanding of the subject, besides improving on general skills such as teamwork, communicating on a subject, and making presentations in front of others. There are several advantages for the schools and university involved. For example they gain a formal and an informal link, which can prove useful in many circumstances when an exchange of information is needed, and both can use SI as a means to boost recruitment. For the upper secondary school, the students can get an alternative view on subjects, which hopefully stimulates interest and understanding. The students also get a more mature role model to turn to. For the university an additional advantage is that a more informal view of what it is like to study at university can be provided to upper secondary school students.

The South Pole Acoustic Test Setup (SPATS) was built to evaluate the acoustic characteristics of the South Pole ice in the 10-100 kHz frequency range, for the purpose of assessing the feasibility of an acoustic neutrino detection array at the South Pole. The SPATS hardware consists of four vertical strings deployed in the upper 500 m of the South Pole ice cap. The strings form a trapezoidal array with a maximum baseline of 543 m. Each string has seven stages equipped with one transmitter and one sensor module (glaciophone). Sound is detected or generated by piezoelectric ceramic elements inside the modules. Analogue signals are sent to the surface on electric cables where they are digitized by a PC-based data acquisition system. The data from all strings are collected on a central computer in the IceCube Laboratory from where they are sent to a central data storage facility via a satellite link or stored locally on tape. A technical overview of SPATS and its performance is presented. (C) 2012 Elsevier B.V. All rights reserved.

Background. Cytologic screening can reduce mortality from cervical cancer by detection and removal of premalignant lesions. Conceivably, mortality is further reduced because more women with invasive disease are diagnosed at an earlier. curable stage. This hypothesis can be assessed in Sweden, where population-based screening programs were introduced successively over about a decade starting in 1964. Methods. Record linkages permitted complete follow-up through 1986 of all 17,377 patients with invasive cervical cancer diagnosed in Sweden from 1960 through 1984. We analyzed relative survival rates that describe the survival of patients after elimination of the effects of causes of death other than cancer of the cervix. Results. Prognosis improved substantially in patients younger than age 50 years at diagnosis; from 1960–1964 to 1980–1984, the 5-year relative survival rate increased from 69.8% to 88.8% at age 20–29 years, from 71.7% to 85.5% at age 30–39 years, and from 68.6% to 77.9% at age 40–49 years. The excess mortality was thus reduced by more than half in patients diagnosed when younger than 40 years. In contrast, only slight or no improvement was noted in those diagnosed at older ages when screening was less extensive. In all time periods, a strong association was found between older age at diagnosis and poorer prognosis. Conclusion. Although alternative explanations for our findings must be seriously considered, the most obvious interpretation is that cytologic screening reduces mortality from cervical cancer by earlier diagnosis of invasive disease.

First exclusive data for the pp -> nnp(+)pi(+) reaction have been obtained at CELSIUS with the WASA detector setup at a beam energy of T-p - 1.1 GeV. Total and differential cross-sections disagree with theoretical calculations, which predict the Delta Delta excitation to be the dominant process at this beam energy. Instead, the data require the excitation of one of the nucleons to a higher-lying Delta state, preferably the Delta(1600)P-33, to be the leading process.

The pd → npp charge exchange reaction has been studied at 1.15 GeV incident proton energy in a selected kinematical region. The distributions of two-proton invariant mass Mpp, of angle of a single proton and the differential cross section dσ/dt of the (p, n) reaction are presented and compared with model predictions corrected for the acceptance of the experimental apparatus. We see no evidence of narrow (Γ < 30 MeV/c2) peaks in the Mpp interval 2.1-2.3 GeV/c2. The production of an intermediate Δ isobar in the primary (p, n) charge exchange and its subsequent absorption in a final state ΔN → pp process together with the background from quasi-free charge exchange scattering reasonably reproduces the general trends of the data.

The pd→npp reaction has been measured using circulating 1.15 GeV protons, a gas jet target and scintillation detectors selecting scattered protons with energy above 30 MeV. The distribution of the two-proton invariant mass has a maximum at 2.13±0.01 GeV/c2 and a width of 130±10 MeV/c2 (FWHM). We see no evidence of narrow (gG < 30 MeV/c2) peaks in the phase-space region selected. The mass of X, excited in the pN→nX elementary process, is 40 MeV/c2 smaller than the mass of a real Δ isobar.

The aim of this study was to investigate how a screening program interacts with the dynamic natural history of cervical neoplasia in order to learn how screening for cervical cancer should be carried out most cost-effectively. For the purpose of optimization, the fundamental quantities of the natural history are the shape of the curve of age-specific prevalence rates of cancer in situ, and the duration of this stage before progression to invasive cancer. Since these quantities seem similar in different populations, the results probably can be generalized. Simulation studies revealed that optimal screening implies a nonperiodic schedule, and that this schedule is dependent not only on the number of screenings, but also on the efficiency of the screening rounds. With lower efficiency, the schedule should be concentrated into a shorter period. The effect of screening is also especially sensitive to the choice of age at the first and--to a smaller extent--last screening. The results concerning three different objectives also were compared, namely reduction of the cumulative number of invasive cancers, reduction of deaths due to cervical cancer, and reduction of years-of-life lost. The choice of objective also plays a role in the design of an optimal screening program. The theoretical approach in this analysis easily can be developed and accommodated to more complex individual situations such as prior screening histories and differing screening schedules in high- and low-risk women.

A population system can be modelled using a micro model focusing on the individual entities, a macro model where the entities are aggregated into compartments, or a state-based model where each possible discrete state in which the system can exist is represented. However, the concepts, building blocks, procedural mechanisms and the time handling for these approaches are very different. For the results and conclusions from studies based on micro, macro and state-based models to be consistent (contradiction-free), a number of modelling issues must be understood and appropriate modelling procedures be applied. This paper presents a uniform approach to micro, macro and state-based population modelling so that these different types of models produce consistent results and conclusions. In particular, we demonstrate the procedures (distribution, attribute and combinatorial expansions) necessary to keep these three types of models consistent. We also show that the different time handling methods usually used in micro, macro and state-based models can be regarded as different integration methods that can be applied to any of these modelling categories. The result is free choice in selecting the modelling approach and the time handling method most appropriate for the study without distorting the results and conclusions.

The production of omega mesons in the pd -> He-3 omega reaction has been studied at two energies near the kinematic threshold, T-p = 1450 MeV and T-p = 1360 MeV. The differential cross section w ...