Detection of hidden model errors by combining single and multi-criteria calibration

Environmental models aim to reproduce landscape processes with mathematical equations. Observations are used for validation. The performance and uncertainties are quantified either by single or multi-criteria model assessment. In a case-study, we combine both approaches. We use a coupled hydro-biogeochemistry landscape-scale model to simulate 14 target values on discharge, stream nitrate as well as soil moisture, soil temperature and trace gas emissions (N₂O, CO₂) from different land uses. We reveal typical mistakes that happen during both, single and multi-criteria model assessment. Such as overestimated uncertainty in multi-criteria and ignored wrong model processes in single-criterion calibration. These mistakes can mislead the development of water quality and in general all environmental models. Only the combination of both approaches reveals the five types of posterior probability distributions for model parameters. Each type allocates a specific type of error. We identify and locate mismatched parameter values, obsolete parameters, flawed model structures and wrong process representations. The presented method can guide model users and developers to the so far hidden errors in their models. We emphasize to include observations from physical, chemical, biological and ecological processes in the model assessment, rather than the typical discipline specific assessments.

Citizen science in hydrological monitoring and ecosystem services management: State of the art and future prospects

Hydrological monitoring is essential to guide evidence-based decision making necessary for sustainable water resource management and governance. Limited hydrometric datasets and the pressure on long-term hydrological monitoring networks make it paramount to explore alternative methods for data collection. This is particularly the case for low-income countries, where data scarcity is more pronounced, and where conventional monitoring methods are expensive and logistically challenging. Citizen science in hydrological research has recently gained popularity and crowdsourced monitoring is a promising cost-effective approach for data collection. Citizen science also has the potential to enhance knowledge co-creation and science-based evidence that underpins the governance and management of water resources. This paper provides a comprehensive review on citizen science and crowdsourced data collection within the context of hydrology, based on a synthesis of 71 articles from 2001 to 2018. Application of citizen science in hydrology is increasing in number and breadth, generating a plethora of scientific data. Citizen science approaches differ in scale, scope and degree of citizen involvement. Most of the programs are found in North America and Europe. Participation mostly comprises a contributory citizen science model, which engages citizens in data collection. In order to leverage the full potential of citizen science in knowledge co-generation, future citizen science projects in hydrology could benefit from more co-created types of projects that establish strong ties between research and public engagement, thereby enhancing the long-term sustainability of monitoring networks.

Citizen science pioneers in Kenya - A crowdsourced approach for hydrological monitoring

Although water is involved in many ecosystem services, the absence of monitoring data restricts the development of effective water management strategies especially in remote regions. Traditional monitoring networks can be expensive, with unaffordable costs in many low-income countries. Involving citizens in monitoring through crowdsourcing has the potential to reduce these costs but remains uncommon in hydrology. This study evaluates the quality and quantity of data generated by citizens in a remote Kenyan basin and assesses whether crowdsourcing is a suitable method to overcome data scarcity. We installed thirteen water level gauges equipped with signboards explaining the monitoring process to passers-by. Results were sent via a text-message-based data collection framework that included an immediate feedback to citizens. A public web interface was used to visualize the data. Within the first year, 124 citizens reported 1175 valid measurements. We identified thirteen citizens as active observers providing more than ten measurements, whereas 57% only sent one record. A comparison between the crowdsourced water level data and an automatic gauging station revealed high data quality. The results of this study indicate that citizens can provide water level data of sufficient quality and with high temporal resolution.

[Telemedicine in stroke care]

Telemedicine is already widely used in many telestroke networks and ensures stroke treatment close to the patient's home in rural and medically underserved areas. This is particularly effective when telemedicine is integrated into a stroke unit concept. While telemedically based thrombolysis therapy has become routine practice for many years, practical implementation of comprehensive mechanical thrombectomy and the related processes remains challenging. The main tasks for the future further include development of a structured stroke aftercare system in neurologically underserved areas and permanent assurance of high-quality stroke care in telemedically connected sites.

The Queueing Model MAP|PH|1|N with Feedback Operating in a Markovian Random Environment

Queueing systems with feedback are well suited for the description of message transmission and manufacturing processes where a repeated service is required. In the present paper we investigate a rather general single server queue with a Markovian Arrival Process (MAP), Phase-type (PH) service-time distribution, a finite buffer and feedback which operates in a random environment. A finite state Markovian random environment affects the parameters of the input and service processes and the feedback probability. The stationary distribution of the queue and of the sojourn times as well as the loss probability are calculated. Moreover, Little’s law is derived.

A new setup for the investigation of swift heavy ion induced particle emission and surface modifications

The irradiation with fast ions with kinetic energies of >10 MeV leads to the deposition of a high amount of energy along their trajectory (up to several ten keV/nm). The energy is mainly transferred to the electronic subsystem and induces different secondary processes of excitations, which result in significant material modifications. A new setup to study these ion induced effects on surfaces will be described in this paper. The setup combines a variable irradiation chamber with different techniques of surface characterizations like scanning probe microscopy, time-of-flight secondary ion, and neutral mass spectrometry, as well as low energy electron diffraction under ultra high vacuum conditions, and is mounted at a beamline of the universal linear accelerator (UNILAC) of the GSI facility in Darmstadt, Germany. Here, samples can be irradiated with high-energy ions with a total kinetic energy up to several GeVs under different angles of incidence. Our setup enables the preparation and in situ analysis of different types of sample systems ranging from metals to insulators. Time-of-flight secondary ion mass spectrometry enables us to study the chemical composition of the surface, while scanning probe microscopy allows a detailed view into the local electrical and morphological conditions of the sample surface down to atomic scales. With the new setup, particle emission during irradiation as well as persistent modifications of the surface after irradiation can thus be studied. We present first data obtained with the new setup, including a novel measuring protocol for time-of-flight mass spectrometry with the GSI UNILAC accelerator.

Comparison of conventional CTA and volume perfusion CTA in evaluation of cerebral arterial vasculature in acute stroke

BACKGROUND AND PURPOSE

CTA-like datasets can be reconstructed from whole-brain VPCTA. The aim of our study was to compare VPCTA with CTA for detection of intracranial stenosis and occlusion in stroke patients. Omitting CTA from stroke CT could reduce radiation dose.

MATERIALS AND METHODS

One hundred sixty-three patients were included in this retrospective analysis. Inclusion criterion was suspected stroke within 4.5 hours after onset of symptoms. All examinations were performed on a 128-section multidetector CT scanner. Axial, coronal, and sagittal maximum intensity projections were reconstructed from CTA and from peak arterial phase of VPCTA. Images were scored for quality and presence of intracranial stenosis >50% or occlusion. For statistical analysis, the Wilcoxon signed-rank test and Fisher exact test were used, with a 2-tailed P value of .05 or less for statistical significance.

RESULTS

Average image quality was superior in CTA (P < .05). However, image quality dichotomized for diagnostic significance was without difference between CTA and VPCTA (P > .05). Comparative statistical analysis revealed no significant difference for detection of intracranial stenosis and occlusion between CTA and VPCTA (P > .05). Substitution of intracranial CTA by VPCTA would lower radiation dose by 0.5 mSv.

CONCLUSIONS

VPCTA is suited to assess the intracranial vasculature in patients with stroke and might have the potential to decrease radiation dose by substituting for intracranial CTA in stroke CT. Additional studies are necessary to further evaluate potential benefits of the dynamic nature of VPCTA.

Intravenous thrombolysis in posterior cerebral artery infarctions

BACKGROUND

Approximately 5-10% of all acute ischemic strokes (AIS) occur in the territory of the posterior cerebral artery (PCA). Little is known about intravenous thrombolysis (IVT) in this infarct subgroup in terms of outcome and intracerebral hemorrhage rates. The aim of our study was to evaluate differences between supratentorial PCA infarcts and anterior circulation infarcts regarding baseline characteristics, stroke severity, outcome, safety and clinical findings, which would implicate a change in the existing thrombolysis practice in patients with PCA stroke.

METHODS

All patients with AIS in the supratentorial PCA territory receiving IVT between 01/2006 and 01/2010 were selected from the Erlangen Thrombolysis Database (group 1, n = 21). They were compared to all IVT patients with strokes in other supratentorial vascular territories over the same period of time (group 2, n = 398). Baseline demographic data, as well as clinical and laboratory findings were analyzed. The outcome was assessed using the modified Rankin Scale at 3 months.

RESULTS

Only serum glucose levels at baseline (110.5 ± 36.1 vs. 127.2 ± 48.2 mg/dl; p = 0.036) and the baseline National Institutes of Health Stroke Scale score (median 6.5 vs. 9; p = 0.016) were significantly lower in group 1 compared to group 2. Favorable clinical outcome (57.1 vs. 48.6%; p = 0.445) and intracerebral hemorrhage rates (4.8 vs. 4%; p = 1.000) were comparable in both groups.

CONCLUSIONS

No substantial differences were found between supratentorial PCA and anterior circulation infarcts. Our data on safety and efficacy support the present common thrombolysis practice in supratentorial PCA infarct patients, though an indication for IVT should rather be based on the existence of functionally disabling deficit than merely on the National Institutes of Health Stroke Scale.

Characteristics and Outcome of Patients with Early Complete Neurological Recovery after Thrombolysis for Acute Ischemic Stroke

<i>Background:</i> Recombinant tissue plasminogen activator (rt-PA) is the only approved specific therapy for acute ischemic stroke. This study analyzes demographic and clinical characteristics of patients with early complete neurological recovery after thrombolysis. <i>Methods:</i> Data of 320 consecutive patients treated with rt-PA within 3 h of stroke onset at our facility between April 2006 and March 2009 were extracted from our prospective institutional stroke and thrombolysis database. Baseline demographic parameters, risk factors, clinical characteristics as well as neuroradiologic findings of patients with complete recovery 24 h after treatment and at hospital discharge were analyzed. Outcome was evaluated using the modified Rankin Scale at 90 days. <i>Results:</i> Thirty patients (9.4%) were asymptomatic 24 h after thrombolysis and 70 (22%) at hospital discharge. Patients with complete recovery were younger, more often male, had milder stroke symptoms, less often cardioembolic strokes, fewer bleeding complications and more often normal follow-up imaging. In addition, in-hospital time was shorter and these patients retained a better functional outcome at 90 days. Only 1 patient who had completely recovered at hospital discharge died during the follow-up time. In multivariate regression analysis, only the National Institute of Health Stroke Score (NIHSS) on admission was predictive for complete recovery at both examined time points. <i>Conclusion:</i> Rapid complete recovery can be achieved in up to a fifth of acute stroke patients treated with thrombolysis. These patients are younger and have milder strokes, less often with cardioembolic origin. Better outcome and lower mortality are sustained at 3 months.

Feasibility and safety of magnetic resonance imaging-based thrombolysis in patients with stroke on awakening: initial single-centre experience

BACKGROUND

Up to 25% of all acute ischaemic strokes occur during sleep. Because of the unclear time window, patients with stroke on awakening are usually not considered for acute therapy and excluded from most acute treatment trials.

AIM

To evaluate the feasibility of magnetic resonance imaging-based intravenous thrombolysis in patients with stroke on awakening in a routine clinical setting.

METHODS

Forty-five patients with stroke on awakening clinically qualifying for intravenous thrombolysis and presenting within 6 h after symptom recognition were admitted to our institution between October 2006 and May 2008. Following an institutional protocol, patients received magnetic resonance imaging as a first-line imaging modality and were offered mismatch-based thrombolysis whenever possible. Baseline demographic data, clinical, laboratory and imaging findings were analysed. Outcome was assessed using the modified Rankin Scale score at 3 months.

RESULTS

Magnetic resonance imaging screening was feasible in 43/45 patients (96%). After screening, 10 patients (22%) were treated with intravenous thrombolysis. There were no differences between treated and untreated patients regarding cardiovascular risk factors, stroke aetiology, previous prophylactic treatment and symptom recognition to door time or door to imaging time. Outcome was comparable in both groups despite a trend towards more severe strokes in the intravenous thrombolysis group. Only one asymptomatic and no symptomatic haemorrhage were observed.

CONCLUSION

Our data demonstrate that magnetic resonance imaging-based thrombolysis is feasible and possibly safe in patients with stroke on awakening (SOA). Randomised clinical trials for patients with stroke on awakening are needed to further test the safety and efficacy of intravenous thrombolysis in this patient group. The results of our study may help to initiate and design such studies.

[Wake up stroke: Overview on diagnostic and therapeutic options for ischemic stroke on awakening]

Up to 25 % of all acute ischemic strokes (AIS) occur during sleep with the patients or relatives becoming aware of their neurological deficits as they wake up. Because of the unclear time of stroke onset patients with stroke on awakening are usually not considered for acute therapies and excluded from most treatment trials. We give an overview of the published data regarding ischemic wake up strokes (WUS). In particular we focused on baseline characteristics, imaging methods and therapy strategies. Comparing WUS patients and patients with known stroke onset there were no major differences found regarding patient characteristics, etiology, clinical and radiological characteristics. Even though there is no existing gold standard multiparametric neuroimaging (CT; MRI) appears to be helpful for decision making whether to treat a WUS patient with thrombolysis or not. Especially multiparametric MRI which proved to be safe in patients within an extended time window might serve as an adequate diagnostic tool. The results of first pilot studies analyzing treatment of WUS demonstrate that a substantial number of these patients can be treated with IV thrombolysis (IVT) successfully. Large randomized, controlled, prospective clinical trials for patients with WUS are needed to test safety and efficacy of IVT and to evaluate the assumed benefit of multiparametric neuroimaging techniques in this patient group. The results of first pilot studies may be instrumental to help plan and design such trials.

[Fritz Flügel (1897-1973). Early research on neuroleptics]

In the early 1950s, Fritz Flügel and his colleagues at the Neurology Clinic of the University of Erlangen in Germany contributed greatly to the clinical introduction of chlorpromazine in German psychiatry. Flügel's clinical work made possible in exemplary fashion the first German psychiatric research on neuroleptics. Between 1953 and 1963, scientists were trying to find a theoretical explanation for the positive psychic effect which had become evident during empirical tests with the new substance. Within a few years, the new drug had its breakthrough, which simply was based on worldwide therapeutical success and good empirical results. That already had happened about 10 years before Carlsson came up with the first plausible theory of neuroleptic function by formulating the dopamine hypothesis in 1963. This brought new energy and developments in psychiatric research in general. Newly developed theses have thoroughly changed the therapeutic approach in psychiatry and the way in which pathophysiological contexts of the brain are understood.

BTX measurements with diffusive samplers in the vicinity of a cokery: comparison between ORSA-type samplers and pumped sampling

In the framework of new European directives in the field of ambient air quality assessment specific requirements for measurement methods for benzene will be defined and have to be met in the future. In a residential area in the vicinity of a cokery a comprehensive monitoring programme for BTX compounds (benzene, toluene, xylenes) was carried out with diffusive samplers. Measurement results from 20 sites show a distinct spatial distribution of benzene concentrations which is caused by the emissions of the plant. Comparisons with two pumped measurement methods reveal excellent agreement in the case of benzene. An assessment of measurement uncertainty for the diffusive method is presented in terms of standard deviations from parallel measurements (precision) and by comparison with a reference method according to national and international standards. Data quality objectives required by an upcoming European directive for benzene can be met by diffusive sampling.