799 research outputs found
The relative resistance of children to sepsis mortality: from pathways to drug candidates
Attempts to develop drugs that address sepsis based on leads developed in animal models have failed. We sought to identify leads based on human data by exploiting a natural experiment: the relative resistance of children to mortality from severe infections and sepsis. Using public datasets, we identified key differences in pathway activity (Pathprint) in blood transcriptome profiles of septic adults and children. To find drugs that could promote beneficial (child) pathways or inhibit harmful (adult) ones, we built an in silico pathway drug network (PDN) using expression correlation between drug, disease, and pathway gene signatures across 58,475 microarrays. Specific pathway clusters from children or adults were assessed for correlation with drug-based signatures. Validation by literature curation and by direct testing in an endotoxemia model of murine sepsis of the most correlated drug candidates demonstrated that the Pathprint-PDN methodology is more effective at generating positive drug leads than gene-level methods (e.g., CMap). Pathway-centric Pathprint-PDN is a powerful new way to identify drug candidates for intervention against sepsis and provides direct insight into pathways that may determine survival
Development of a Clinical Type 1 Diabetes Metabolic System Model and in Silico Simulation Tool
Invited journal symposium paperObjectives:
To develop a safe and effective protocol for the clinical control of Type 1 diabetes using conventional self-monitoring blood glucose (SMBG) measurements, and multiple daily injection (MDI) with insulin analogues. To develop an in silico simulation tool of Type 1 diabetes to predict long-term glycaemic control outcomes of clinical interventions.
Methods:
The virtual patient method is used to develop a simulation tool for Type 1 diabetes using data from a Type 1 diabetes patient cohort (n=40). The tool is used to test the adaptive protocol (AC) and a conventional intensive insulin therapy (CC) against results from a representative control cohort. Optimal and suboptimal basal insulin replacement are evaluated as a function of self-monitoring blood glucose (SMBG) frequency in conjunction with the (AC and CC) prandial control protocols.
Results:
In long-term glycaemic control, the AC protocol significantly decreases HbA1c in conditions of suboptimal basal insulin replacement for SMBG frequencies =6/day, and reduced the occurrence of mild and severe hypoglycaemia by 86-100% over controls over all SMBG frequencies in conditions of optimal basal insulin.
Conclusions:
A simulation tool to predict long-term glycaemic control outcomes from clinical interventions is developed to test a novel, adaptive control protocol for Type 1 diabetes. The protocol is effective and safe compared to conventional intensive insulin therapy and controls. As fear of hypoglycaemia is a large psychological barrier to glycaemic control, the AC protocol may represent the next evolution of intensive insulin therapy to deliver increased glycaemic control with increased safety. Further clinical or experimental validation is needed to fully prove the concept
Integral-based filtering of continuous glucose sensor measurements for glycaemic control in critical care
Hyperglycaemia is prevalent in critical illness and increases the risk of further
complications and mortality, while tight control can reduce mortality up to 43%.
Adaptive control methods are capable of highly accurate, targeted blood glucose
regulation using limited numbers of manual measurements due to patient discomfort
and labour intensity. Therefore, the option to obtain greater data density using
emerging continuous glucose sensing devices is attractive. However, the few such
systems currently available can have errors in excess of 20-30%. In contrast, typical
bedside testing kits have errors of approximately 7-10%. Despite greater measurement
frequency larger errors significantly impact the resulting glucose and patient specific
parameter estimates, and thus the control actions determined creating an important
safety and performance issue. This paper models the impact of the Continuous
Glucose Monitoring System (CGMS, Medtronic, Northridge, CA) on model-based
parameter identification and glucose prediction. An integral-based fitting and filtering
method is developed to reduce the effect of these errors. A noise model is developed
based on CGMS data reported in the literature, and is slightly conservative with a
mean Clarke Error Grid (CEG) correlation of R=0.81 (range: 0.68-0.88) as compared to a reported value of R=0.82 in a critical care study. Using 17 virtual patient profiles
developed from retrospective clinical data, this noise model was used to test the
methods developed. Monte-Carlo simulation for each patient resulted in an average
absolute one-hour glucose prediction error of 6.20% (range: 4.97-8.06%) with an
average standard deviation per patient of 5.22% (range: 3.26-8.55%). Note that all the
methods and results are generalisable to similar applications outside of critical care,
such as less acute wards and eventually ambulatory individuals. Clinically, the results
show one possible computational method for managing the larger errors encountered
in emerging continuous blood glucose sensors, thus enabling their more effective use
in clinical glucose regulation studies
Overview of Glycemic Control in Critical Care - Relating Performance and Clinical Results
Inagural review article invited for inaugural journalBackground: Hyperglycemia is prevalent in critical care and tight control can save
lives. Current ad-hoc clinical protocols require significant clinical effort and produce
highly variable results. Model-based methods can provide tight, patient specific
control, while addressing practical clinical difficulties and dynamic patient evolution.
However, tight control remains elusive as there is not enough understanding of the
relationship between control performance and clinical outcome.
Methods: The general problem and performance criteria are defined. The clinical
studies performed to date using both ad-hoc titration and model-based methods are
reviewed. Studies reporting mortality outcome are analysed in terms of standardized
mortality ratio (SMR) and a 95th percentile (±2 ) standard error (SE95%) to enable
better comparison across cohorts.
Results: Model-based control trials lower blood glucose into a 72-110mg/dL band
within 10 hours, have target accuracy over 90%, produce fewer hypoglycemic
episodes, and require no additional clinical intervention. Plotting SMR versus SE95%
shows potentially high correlation (r=0.84) between ICU mortality and tightness of
control.
Summary: Model-based methods provide tighter, more adaptable âone method fits
allâ solutions, using methods that enable patient-specific modeling and control.
Correlation between tightness of control and clinical outcome suggests that
performance metrics, such as time in a relevant glycemic band, may provide better
guidelines. Overall, compared to current âone size fits allâ sliding scale and ad-hoc
regimens, patient-specific pharmacodynamic and pharmacokinetic model-based, or
âone method fits allâ, control, utilizing computational and emerging sensor
technologies, offers improved treatment and better potential outcomes when treating
hyperglycemia in the highly dynamic critically ill patient
NEW SEISMIC SOURCE ZONE MODEL FOR PORTUGAL AND AZORES
The development of seismogenic source models is one of the first steps in seismic hazard assessment. In seismic hazard terminology, seismic source zones (SSZ) are polygons (or volumes) that delineate areas with homogeneous characteristics of seismicity. The importance of using knowledge on geology, seismicity and tectonics in the definition of source zones has been recognized for a long time [1]. However, the definition of SSZ tends to be subjective and controversial. Using SSZ based on broad geology, by spreading the seismicity clusters throughout the areal extent of a zone, provides a way to account for possible long-term non-stationary seismicity behavior [2,3]. This approach effectively increases seismicity rates in regions with no significant historical or instrumental seismicity, while decreasing seismicity rates in regions that display higher rates of seismicity. In contrast, the use of SSZ based on concentrations of seismicity or spatial smoothing results in stationary behavior [4]. In the FP7 Project SHARE (Seismic Hazard Harmonization in Europe), seismic hazard will be assessed with a logic tree approach that allows for three types of branches for seismicity models: a) smoothed seismicity, b) SSZ, c) SSZ and faults. In this context, a large-scale zonation model for use in the smoothed seismicity branch, and a new consensus SSZ model for Portugal and Azores have been developed. The new models were achieved with the participation of regional experts by combining and adapting existing models and incorporating new regional knowledge of the earthquake potential. The main criteria used for delineating the SSZ include distribution of seismicity, broad geological architecture, crustal characteristics (oceanic versus continental, tectonically active versus stable, etc.), historical catalogue completeness, and the characteristics of active or potentially-active faults. This model will be integrated into an Iberian model of SSZ to be used in the Project SHARE seismic hazard assessment
Insulin + nutrition control for tight critical care glycaemic regulation
A new insulin and nutrition control method for tight glycaemic control in
critical care is presented from concept to clinical trials to clinical practice change. The
primary results show that the method can provide very tight glycaemic control in critical
care for a very critically ill cohort. More specifically, the final clinical practice change
protocol provided 2100 hours of control with average blood glucose of 5.8 +/- 0.9
mmol/L for an initial 10 patient pilot study. It also used less insulin, while providing the
same or greater nutritional input, as compared to retrospective hospital control for a
relatively very critically ill cohort with high insulin resistance
COMPILATION OF ACTIVE FAULT DATA IN PORTUGAL FOR USE IN SEISMIC HAZARD ANALYSIS
To estimate where future earthquakes are likely to occur, it is essential to combine information about past earthquakes with knowledge about the location and seismogenic properties of active faults. For this reason, robust probabilistic seismic hazard analysis (PSHA) integrates seismicity and active fault data. Existing seismic hazard assessments for Portugal rely exclusively on seismicity data and do not incorporate data on active faults. Project SHARE (Seismic Hazard Harmonization in Europe) is an EC-funded initiative (FP7) that aims to evaluate European seismic hazards using an integrated, standardized approach. In the context of SHARE, we are developing a fully-parameterized active fault database for Portugal that incorporates existing compilations, updated according to the most recent publications. The seismogenic source model derived for SHARE will be the first model for Portugal to include fault data and follow an internationally standardized approach. This model can be used to improve both seismic hazard and risk analyses and will be combined with the Spanish database for use in Iberian- and European-scale assessments
Number of distinct sites visited by N random walkers on a Euclidean lattice
The evaluation of the average number S_N(t) of distinct sites visited up to
time t by N independent random walkers all starting from the same origin on an
Euclidean lattice is addressed. We find that, for the nontrivial time regime
and for large N, S_N(t) \approx \hat S_N(t) (1-\Delta), where \hat S_N(t) is
the volume of a hypersphere of radius (4Dt \ln N)^{1/2},
\Delta={1/2}\sum_{n=1}^\infty \ln^{-n} N \sum_{m=0}^n s_m^{(n)} \ln^{m} \ln N,
d is the dimension of the lattice, and the coefficients s_m^{(n)} depend on the
dimension and time. The first three terms of these series are calculated
explicitly and the resulting expressions are compared with other approximations
and with simulation results for dimensions 1, 2, and 3. Some implications of
these results on the geometry of the set of visited sites are discussed.Comment: 15 pages (RevTex), 4 figures (eps); to appear in Phys. Rev.
Understanding the Spatial Clustering of Severe Acute Respiratory Syndrome (SARS) in Hong Kong
We applied cartographic and geostatistical methods in analyzing the patterns of disease spread during the 2003 severe acute respiratory syndrome (SARS) outbreak in Hong Kong using geographic information system (GIS) technology. We analyzed an integrated database that contained clinical and personal details on all 1,755 patients confirmed to have SARS from 15 February to 22 June 2003. Elementary mapping of disease occurrences in space and time simultaneously revealed the geographic extent of spread throughout the territory. Statistical surfaces created by the kernel method confirmed that SARS cases were highly clustered and identified distinct disease âhot spots.â Contextual analysis of mean and standard deviation of different density classes indicated that the period from day 1 (18 February) through day 16 (6 March) was the prodrome of the epidemic, whereas days 86 (15 May) to 106 (4 June) marked the declining phase of the outbreak. Origin-and-destination plots showed the directional bias and radius of spread of superspreading events. Integration of GIS technology into routine field epidemiologic surveillance can offer a real-time quantitative method for identifying and tracking the geospatial spread of infectious diseases, as our experience with SARS has demonstrated
Nonequilibrium relaxation in neutral BCS superconductors: Ginzburg-Landau approach with Landau damping in real time
We present a field-theoretical method to obtain consistently the equations of
motion for small amplitude fluctuations of the order parameter directly in real
time for a homogeneous, neutral BCS superconductor. This method allows to study
the nonequilibrium relaxation of the order parameter as an initial value
problem. We obtain the Ward identities and the effective actions for small
phase the amplitude fluctuations to one-loop order. Focusing on the
long-wavelength, low-frequency limit near the critical point, we obtain the
time-dependent Ginzburg-Landau effective action to one-loop order, which is
nonlocal as a consequence of Landau damping. The nonequilibrium relaxation of
the phase and amplitude fluctuations is studied directly in real time. The
long-wavelength phase fluctuation (Bogoliubov-Anderson-Goldstone mode) is
overdamped by Landau damping and the relaxation time scale diverges at the
critical point, revealing critical slowing down.Comment: 31 pages 14 figs, revised version, to appear in Phys. Rev.
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