An insulin infusion advisory system for type 1 diabetes patients based on non-linear model predictive control methods

In this paper, an Insulin Infusion Advisory System (IIAS) for Type 1 diabetes patients, which use insulin pumps for the Continuous Subcutaneous Insulin Infusion (CSII) is presented. The purpose of the system is to estimate the appropriate insulin infusion rates. The system is based on a Non-Linear Model Predictive Controller (NMPC) which uses a hybrid model. The model comprises a Compartmental Model (CM), which simulates the absorption of the glucose to the blood due to meal intakes, and a Neural Network (NN), which simulates the glucose-insulin kinetics. The NN is a Recurrent NN (RNN) trained with the Real Time Recurrent Learning (RTRL) algorithm. The output of the model consists of short term glucose predictions and provides input to the NMPC, in order for the latter to estimate the optimum insulin infusion rates. For the development and the evaluation of the IIAS, data generated from a Mathematical Model (MM) of a Type 1 diabetes patient have been used. The proposed control strategy is evaluated at multiple meal disturbances, various noise levels and additional time delays. The results indicate that the implemented IIAS is capable of handling multiple meals, which correspond to realistic meal profiles, large noise levels and time delays.

Calibrating Wireless Sensor Network Simulation Models with Real-World Experiments

This paper studies the energy-efficiency and service characteristics of a recently developed energy-efficient MAC protocol for wireless sensor networks in simulation and on a real sensor hardware testbed. This opportunity is seized to illustrate how simulation models can be verified by cross-comparing simulation results with real-world experiment results. The paper demonstrates that by careful calibration of simulation model parameters, the inevitable gap between simulation models and real-world conditions can be reduced. It concludes with guidelines for a methodology for model calibration and validation of sensor network simulation models.

Effect of initial treatment strategy on survival of patients with advanced-stage Hodgkin's lymphoma: a systematic review and network meta-analysis

BACKGROUND Several treatment strategies are available for adults with advanced-stage Hodgkin's lymphoma, but studies assessing two alternative standards of care-increased dose bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPPescalated), and doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD)-were not powered to test differences in overall survival. To guide treatment decisions in this population of patients, we did a systematic review and network meta-analysis to identify the best initial treatment strategy. METHODS We searched the Cochrane Library, Medline, and conference proceedings for randomised controlled trials published between January, 1980, and June, 2013, that assessed overall survival in patients with advanced-stage Hodgkin's lymphoma given BEACOPPbaseline, BEACOPPescalated, BEACOPP variants, ABVD, cyclophosphamide (mechlorethamine), vincristine, procarbazine, and prednisone (C[M]OPP), hybrid or alternating chemotherapy regimens with ABVD as the backbone (eg, COPP/ABVD, MOPP/ABVD), or doxorubicin, vinblastine, mechlorethamine, vincristine, bleomycin, etoposide, and prednisone combined with radiation therapy (the Stanford V regimen). We assessed studies for eligibility, extracted data, and assessed their quality. We then pooled the data and used a Bayesian random-effects model to combine direct comparisons with indirect evidence. We also reconstructed individual patient survival data from published Kaplan-Meier curves and did standard random-effects Poisson regression. Results are reported relative to ABVD. The primary outcome was overall survival. FINDINGS We screened 2055 records and identified 75 papers covering 14 eligible trials that assessed 11 different regimens in 9993 patients, providing 59 651 patient-years of follow-up. 1189 patients died, and the median follow-up was 5·9 years (IQR 4·9-6·7). Included studies were of high methodological quality, and between-trial heterogeneity was negligible (τ(2)=0·01). Overall survival was highest in patients who received six cycles of BEACOPPescalated (HR 0·38, 95% credibility interval [CrI] 0·20-0·75). Compared with a 5 year survival of 88% for ABVD, the survival benefit for six cycles of BEACOPPescalated is 7% (95% CrI 3-10)-ie, a 5 year survival of 95%. Reconstructed individual survival data showed that, at 5 years, BEACOPPescalated has a 10% (95% CI 3-15) advantage over ABVD in overall survival. INTERPRETATION Six cycles of BEACOPPescalated significantly improves overall survival compared with ABVD and other regimens, and thus we recommend this treatment strategy as standard of care for patients with access to the appropriate supportive care.

Intussusceptive angiogenesis: its role in embryonic vascular network formation

Intussusceptive angiogenesis is a novel mode of blood vessel formation and remodeling, which occurs by internal division of the preexisting capillary plexus without sprouting. In this study, the process is demonstrated in developing chicken eye vasculature and in the chorioallantoic membrane by methylmethacrylate (Mercox) casting, transmission electron microscopy, and in vivo observation. In a first step of intussusceptive angiogenesis, the capillary plexus expands by insertion of numerous transcapillary tissue pillars, ie, by intussusceptive microvascular growth. In a subsequent step, a vascular tree arises from the primitive capillary plexus as a result of intussusceptive pillar formation and pillar fusions, a process we termed "intussusceptive arborization." On the basis of the morphological observations, a 4-step model for intussusceptive arborization is proposed, as follows: phase I, numerous circular pillars are formed in rows, thus demarcating future vessels; phase II, formation of narrow tissue septa by pillar reshaping and pillar fusions; phase III, delineation, segregation, growth, and extraction of the new vascular entity by merging of septa; and phase IV, formation of new branching generations by successively repeating the process, complemented by growth and maturation of all components. In contrast to sprouting, intussusceptive angiogenesis does not require intense local endothelial cell proliferation; it is implemented primarily by rearrangement and attenuation of the endothelial cell plates. In summary, transcapillary pillar formation, ie, intussusception, is a central and probably widespread process, which plays a role not only in capillary network growth and expansion (intussusceptive microvascular growth), but also in vascular plexus remodeling and tree formation (intussusceptive arborization).

Functional regeneration of intraspinal connections in a new in vitro model

Abstract—Regeneration in the adult mammalian spinal cord is limited due to intrinsic properties of mature neurons and a hostile environment, mainly provided by central nervous system myelin and reactive astrocytes. Recent results indicate that propriospinal connections are a promising target for intervention to improve functional recovery. To study this functional regeneration in vitro we developed a model consisting of two organotypic spinal cord slices placed adjacently on multi-electrode arrays. The electrodes allow us to record the spontaneously occurring neuronal activity, which is often organized in network bursts. Within a few days in vitro (DIV), these bursts become synchronized between the two slices due to the formation of axonal connections. We cut them with a scalpel at different time points in vitro and record the neuronal activity 3 weeks later. The functional recovery ability was assessed by calculating the percentage of synchronized bursts between the two slices. We found that cultures lesioned at a young age (7–9 DIV) retained the high regeneration ability of embryonic tissue. However, cultures lesioned at older ages (>19 DIV) displayed a distinct reduction of synchronized activity. This reduction was not accompanied by an inability for axons to cross the lesion site. We show that functional regeneration in these old cultures can be improved by increasing the intracellular cAMP level with Rolipram or by placing a young slice next to an old one directly after the lesion. We conclude that co-cultures of two spinal cord slices are an appropriate model to study functional regeneration of intraspinal connections.

Approximate decoding approaches for network coded correlated data

This paper considers a framework where data from correlated sources are transmitted with the help of network coding in ad hoc network topologies. The correlated data are encoded independently at sensors and network coding is employed in the intermediate nodes in order to improve the data delivery performance. In such settings, we focus on the problem of reconstructing the sources at decoder when perfect decoding is not possible due to losses or bandwidth variations. We show that the source data similarity can be used at decoder to permit decoding based on a novel and simple approximate decoding scheme. We analyze the influence of the network coding parameters and in particular the size of finite coding fields on the decoding performance. We further determine the optimal field size that maximizes the expected decoding performance as a trade-off between information loss incurred by limiting the resolution of the source data and the error probability in the reconstructed data. Moreover, we show that the performance of the approximate decoding improves when the accuracy of the source model increases even with simple approximate decoding techniques. We provide illustrative examples showing how the proposed algorithm can be deployed in sensor networks and distributed imaging applications.

Potentially avoidable 30-day hospital readmissions in medical patients: derivation and validation of a prediction model

IMPORTANCE Because effective interventions to reduce hospital readmissions are often expensive to implement, a score to predict potentially avoidable readmissions may help target the patients most likely to benefit. OBJECTIVE To derive and internally validate a prediction model for potentially avoidable 30-day hospital readmissions in medical patients using administrative and clinical data readily available prior to discharge. DESIGN Retrospective cohort study. SETTING Academic medical center in Boston, Massachusetts. PARTICIPANTS All patient discharges from any medical services between July 1, 2009, and June 30, 2010. MAIN OUTCOME MEASURES Potentially avoidable 30-day readmissions to 3 hospitals of the Partners HealthCare network were identified using a validated computerized algorithm based on administrative data (SQLape). A simple score was developed using multivariable logistic regression, with two-thirds of the sample randomly selected as the derivation cohort and one-third as the validation cohort. RESULTS Among 10 731 eligible discharges, 2398 discharges (22.3%) were followed by a 30-day readmission, of which 879 (8.5% of all discharges) were identified as potentially avoidable. The prediction score identified 7 independent factors, referred to as the HOSPITAL score: h emoglobin at discharge, discharge from an o ncology service, s odium level at discharge, p rocedure during the index admission, i ndex t ype of admission, number of a dmissions during the last 12 months, and l ength of stay. In the validation set, 26.7% of the patients were classified as high risk, with an estimated potentially avoidable readmission risk of 18.0% (observed, 18.2%). The HOSPITAL score had fair discriminatory power (C statistic, 0.71) and had good calibration. CONCLUSIONS AND RELEVANCE This simple prediction model identifies before discharge the risk of potentially avoidable 30-day readmission in medical patients. This score has potential to easily identify patients who may need more intensive transitional care interventions.

Investigation of the Network Construction Behaviour on Social Networking Sites

By enabling connections between individuals, Social Networking Sites, such as Facebook, promise to create significant individual as well as social value. Encouraging connections between users is also crucial for service providers who increasingly rely on social advertising and viral marketing campaigns as important sources of their revenue. Consequently, understanding user’s network construction behavior becomes critical. However, previous studies offer only few scattered insights into this research question. In order to fill this gap, we employ Grounded Theory methodology to derive a comprehensive model of network construction behavior on social networking sites. In the following step we assess two Structural Equation Models to gain refined insights into the motivation to send and accept friendship requests – two network expansion strategies. Based on our findings, we offer recommendations for social network providers.

Solute transport in crystalline rocks at Äspö — I: Geological basis and model calibration

Water-conducting faults and fractures were studied in the granite-hosted A¨ spo¨ Hard Rock Laboratory (SE Sweden). On a scale of decametres and larger, steeply dipping faults dominate and contain a variety of different fault rocks (mylonites, cataclasites, fault gouges). On a smaller scale, somewhat less regular fracture patterns were found. Conceptual models of the fault and fracture geometries and of the properties of rock types adjacent to fractures were derived and used as input for the modelling of in situ dipole tracer tests that were conducted in the framework of the Tracer Retention Understanding Experiment (TRUE-1) on a scale of metres. After the identification of all relevant transport and retardation processes, blind predictions of the breakthroughs of conservative to moderately sorbing tracers were calculated and then compared with the experimental data. This paper provides the geological basis and model calibration, while the predictive and inverse modelling work is the topic of the companion paper [J. Contam. Hydrol. 61 (2003) 175]. The TRUE-1 experimental volume is highly fractured and contains the same types of fault rocks and alterations as on the decametric scale. The experimental flow field was modelled on the basis of a 2D-streamtube formalism with an underlying homogeneous and isotropic transmissivity field. Tracer transport was modelled using the dual porosity medium approach, which is linked to the flow model by the flow porosity. Given the substantial pumping rates in the extraction borehole, the transport domain has a maximum width of a few centimetres only. It is concluded that both the uncertainty with regard to the length of individual fractures and the detailed geometry of the network along the flowpath between injection and extraction boreholes are not critical because flow is largely one-dimensional, whether through a single fracture or a network. Process identification and model calibration were based on a single uranine breakthrough (test PDT3), which clearly showed that matrix diffusion had to be included in the model even over the short experimental time scales, evidenced by a characteristic shape of the trailing edge of the breakthrough curve. Using the geological information and therefore considering limited matrix diffusion into a thin fault gouge horizon resulted in a good fit to the experiment. On the other hand, fresh granite was found not to interact noticeably with the tracers over the time scales of the experiments. While fracture-filling gouge materials are very efficient in retarding tracers over short periods of time (hours–days), their volume is very small and, with time progressing, retardation will be dominated by altered wall rock and, finally, by fresh granite. In such rocks, both porosity (and therefore the effective diffusion coefficient) and sorption Kds are more than one order of magnitude smaller compared to fault gouge, thus indicating that long-term retardation is expected to occur but to be less pronounced.

The Hamburg-Model of Integrated Care for Patients with Psychosis: Part 1

Objective: The "Hamburg model" designates an integrated care model for severely ill patients with psychotic disorders financed by the health insurance system in accordance with § 140 SGB V.Methods: It comprises comprehensive and long-term treatment within a regional network of the psychosis center of the University Medical Center Hamburg-Eppendorf (UKE) and private psychiatrists. The treatment model consists of therapeutic assertive community treatment (ACT) provided by a highly specialized treatment team and need-adapted in- and outpatient care.Results and conclusions: The present article summarizes the disease- and treatment-specific rationales for the model development as well as the model structure and treatment contents. The article further summarizes the effectiveness and efficiency results of a study comparing the Hamburg model and treatment as usual (without ACT) within a 12-month follow-up study (ACCESS trial).

The craniosacral progression of muscle development influences the emergence of neuromuscular junction alterations in a severe murine model for spinal muscular atrophy.

AIMS As 4-day-old mice of the severe spinal muscular atrophy (SMA) model (dying at 5-8 days) display pronounced neuromuscular changes in the diaphragm but not the soleus muscle, we wanted to gain more insight into the relationship between muscle development and the emergence of pathological changes and additionally to analyse intercostal muscles which are affected in human SMA. METHODS Structures of muscle fibres and neuromuscular junctions (NMJs) of the diaphragm, intercostal and calf muscles of prenatal (E21) and postnatal (P0 and P4) healthy and SMA mice were analysed by light and transmission electron microscopy. NMJ innervation was studied by whole mount immunofluorescence in diaphragms of P4 mice. RESULTS During this period, the investigated muscles still show a significant neck-to-tail developmental gradient. The diaphragm and calf muscles are most and least advanced, respectively, with respect to muscle fibre fusion and differentiation. The number and depth of subsynaptic folds increases, and perisynaptic Schwann cells (PSCs) acquire a basal lamina on their outer surface. Subsynaptic folds are connected to an extensive network of tubules and beaded caveolae, reminiscent of the T system in adult muscle. Interestingly, intercostal muscles from P4 SMA mice show weaker pathological involvement (that is, vacuolization of PSCs and perineurial cells) than those previously described by us for the diaphragm, whereas calf muscles show no pathological changes. CONCLUSION SMA-related alterations appear to occur only when the muscles have reached a certain developmental maturity. Moreover, glial cells, in particular PSCs, play an important role in SMA pathogenesis.

Evidence of an association between sleep and levodopa-induced dyskinesia in an animal model of Parkinson's disease.

Levodopa-induced dyskinesia (LID) represents a major challenge for clinicians treating patients affected by Parkinson's disease (PD). Although levodopa is the most effective treatment for PD, the remodeling effects induced by disease progression and the pharmacologic treatment itself cause a narrowing of the therapeutic window because of the development of LID. Although animal models of PD provide strong evidence that striatal plasticity underlies the development of dyskinetic movements, the pathogenesis of LID is not entirely understood. In recent years, slow homeostatic adjustment of intrinsic excitability occurring during sleep has been considered fundamental for network stabilization by gradually modifying plasticity thresholds. So far, how sleep affects on LID has not been investigated. Therefore, we measured synaptic downscaling across sleep episodes in a parkinsonian animal model showing dyskinetic movements similar to LID. Our electrophysiological, molecular, and behavioral results are consistent with an impaired synaptic homeostasis during sleep in animals showing dyskinesia. Accordingly, sleep deprivation causes an anticipation and worsening of LID supporting a link between sleep and the development of LID.

Regulation of androgen biosynthesis - A short review and preliminary results from the hyperandrogenic starvation NCI-H295R cell model

Regulation of androgen production is poorly understood. Adrenarche is the physiologic event in mid-childhood when the adrenal zona reticularis starts to produce androgens through specific expression of genes for enzymes and cofactors necessary for androgen synthesis. Similarly, expression and activities of same genes and products are deregulated in hyperandrogenic disorders such as the polycystic ovary syndrome (PCOS). Numerous studies revealed involvement of several signaling pathways stimulated through G-protein coupled receptors or growth factors transmitting their effects through cAMP- or non-cAMP-dependent signaling. Overall a complex network regulates androgen synthesis targeting involved genes and proteins at the transcriptional and post-translational levels. Newest players in the field are the DENND1A gene identified in PCOS patients and the MAPK14 which is the kinase phosphorylating CYP17 for enhanced lyase activity. Next generation sequencing studies of PCOS patients and transcriptome analysis of androgen producing tissues or cell models provide newer tools to identify modulators of androgen synthesis.

Multi-Model Data Fusion to Improve an Early Warning System for Hypo-/Hyperglycemic Events

Correct predictions of future blood glucose levels in individuals with Type 1 Diabetes (T1D) can be used to provide early warning of upcoming hypo-/hyperglycemic events and thus to improve the patient's safety. To increase prediction accuracy and efficiency, various approaches have been proposed which combine multiple predictors to produce superior results compared to single predictors. Three methods for model fusion are presented and comparatively assessed. Data from 23 T1D subjects under sensor-augmented pump (SAP) therapy were used in two adaptive data-driven models (an autoregressive model with output correction - cARX, and a recurrent neural network - RNN). Data fusion techniques based on i) Dempster-Shafer Evidential Theory (DST), ii) Genetic Algorithms (GA), and iii) Genetic Programming (GP) were used to merge the complimentary performances of the prediction models. The fused output is used in a warning algorithm to issue alarms of upcoming hypo-/hyperglycemic events. The fusion schemes showed improved performance with lower root mean square errors, lower time lags, and higher correlation. In the warning algorithm, median daily false alarms (DFA) of 0.25%, and 100% correct alarms (CA) were obtained for both event types. The detection times (DT) before occurrence of events were 13.0 and 12.1 min respectively for hypo-/hyperglycemic events. Compared to the cARX and RNN models, and a linear fusion of the two, the proposed fusion schemes represents a significant improvement.

A numerical model for inert gas transport in the lung based on fractal airway morphology

Patients suffering from cystic fibrosis (CF) show thick secretions, mucus plugging and bronchiectasis in bronchial and alveolar ducts. This results in substantial structural changes of the airway morphology and heterogeneous ventilation. Disease progression and treatment effects are monitored by so-called gas washout tests, where the change in concentration of an inert gas is measured over a single or multiple breaths. The result of the tests based on the profile of the measured concentration is a marker for the severity of the ventilation inhomogeneity strongly affected by the airway morphology. However, it is hard to localize underlying obstructions to specific parts of the airways, especially if occurring in the lung periphery. In order to support the analysis of lung function tests (e.g. multi-breath washout), we developed a numerical model of the entire airway tree, coupling a lumped parameter model for the lung ventilation with a 4th-order accurate finite difference model of a 1D advection-diffusion equation for the transport of an inert gas. The boundary conditions for the flow problem comprise the pressure and flow profile at the mouth, which is typically known from clinical washout tests. The natural asymmetry of the lung morphology is approximated by a generic, fractal, asymmetric branching scheme which we applied for the conducting airways. A conducting airway ends when its dimension falls below a predefined limit. A model acinus is then connected to each terminal airway. The morphology of an acinus unit comprises a network of expandable cells. A regional, linear constitutive law describes the pressure-volume relation between the pleural gap and the acinus. The cyclic expansion (breathing) of each acinus unit depends on the resistance of the feeding airway and on the flow resistance and stiffness of the cells themselves. Special care was taken in the development of a conservative numerical scheme for the gas transport across bifurcations, handling spatially and temporally varying advective and diffusive fluxes over a wide range of scales. Implicit time integration was applied to account for the numerical stiffness resulting from the discretized transport equation. Local or regional modification of the airway dimension, resistance or tissue stiffness are introduced to mimic pathological airway restrictions typical for CF. This leads to a more heterogeneous ventilation of the model lung. As a result the concentration in some distal parts of the lung model remains increased for a longer duration. The inert gas concentration at the mouth towards the end of the expirations is composed of gas from regions with very different washout efficiency. This results in a steeper slope of the corresponding part of the washout profile.