Integrated organic light-emitting device/fluorescence-based chemical sensors

A fluorescent chemical sensor platform, integrating an organic light-emitting device (OLED) light-source with a fluorescent probe, is demonstrated for a subsecond-fast oxygen sensor. The integration results in strong light coupling and negligible heating of the sensor film or analyte. The potential in vivo operation of compact, stand-alone, battery-powered, OLED-based miniaturized sensor arrays for chemical and biological applications is discussed. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69695/2/APPLAB-81-24-4652-1.pd

Tunable perovskite-based photodetectors in optical sensing

Broad- and narrow-band, tunable perovskite photodetectors (PPDs) with size-dependent fast response times are demonstrated for the first time in optical sensing of analytes, including gas-phase and dissolved oxygen (DO), as well as glucose. The sensors included a LED excitation source and a polystyrene film with embedded oxygen-sensitive dyes, PtOEP or PdOEP. The analyte's dose-dependent photoluminescence (PL) intensity I and decay time τ were measured. Using the PPDs enabled monitoring gas-phase O2 at levels of 0 %–100 % with a sensitivity comparable to that of a Si photodiode. A broad dynamic range was similarly observed for DO monitoring and the limit of detection for glucose monitoring was ∼0.02 mM at an initial level of ∼0.26 mM DO. Importantly, the size-dependent fast response time of the PPDs enabled analyte monitoring via the preferred measurement of τ, rather than I, over a broad dynamic range, which was unattainable with organic photodetectors. The use of the narrow-band PPDs eliminated the need for optical filters, which leads to more compact device designs

The validity of police reported accident data

Information theory and signal detection theory techniques were used to assess the validity of police reported traffic accident data. The validity criteria were the data and conclusions of multi-disciplinary accident investigation teams who investigated the same traffic accidents. The results indicated that the accident level variables reported by the police with least reliability were vertical road character, accident severity, and road surface composition. The most reliably reported data were those concerned with the accident location, date, and number of drivers, passengers, and vehicles. The informativeness of the police reports with respect to driver/vehicle characteristics was practically nil, with the exception of driver age, sex and vehicle model for which the police were correct most of the time (but not errorless). It was also found that police reports provided very little information regarding the presence of different human conditions and states, vehicle defects and environmental/road deficiencies. The sensitivity of police investigators to all accident causes was low. When causes were categorized into human direct, human indirect (conditions and states) vehicle, and environmental, police were the most reliable with respect to human direct causes and the least reliable with respect to environmental and human indirect causes. Implications for improvement and use of police data are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25202/1/0000641.pd

Electroluminescence-detected magnetic-resonance study of polyparaphenylenevinylene (PPV)-based light-emitting diodes

The strong electroluminescence (EL)-detected magnetic resonance of PPV-based light emitting diodes is compared to the conductivity (sigma)- and photoluminescence (PL)-detected resonances. It provides direct evidence that polaron-to-singlet exciton conversion is responsible for the EL. In contrast to the narrow PL-enhancing resonance assigned to polaron recombination, strong EL- and sigma-quenching resonances are attributed to the spin-dependent polaron-to-bipolaron decay. The half-field EL- and sigma-detected resonances of two distinct triplet excitons is believed to result from triplet-triplet fusion to singlets

Microelectromagnetic ferrofluid-based actuator

Computer simulations were used to investigate the performance of a microscale ferrofluid-based magnetic actuator developed for liquid dispensing in microfluidic channels. The actuation was based on the movement of a ferrofluid plug in a magnetic field gradient generated by on-chip effectively infinite parallel conductors. The movement, positioning, and retaining of ferrofluid plugs with different lengths at various locations along a microfluidic channel were investigated for two cases. In case (a), the magnetic field gradient was generated by a single conductor; when the ferrofluid reached its equilibrium position, the current was switched off and the nearest neighbor conductor was energized. A similar, consecutive on/off current switching was performed for case (b), where a set of conductors was energized simultaneously

Robust Signal Processing in Living Cells

Cellular signaling networks have evolved an astonishing ability to function reliably and with high fidelity in uncertain environments. A crucial prerequisite for the high precision exhibited by many signaling circuits is their ability to keep the concentrations of active signaling compounds within tightly defined bounds, despite strong stochastic fluctuations in copy numbers and other detrimental influences. Based on a simple mathematical formalism, we identify topological organizing principles that facilitate such robust control of intracellular concentrations in the face of multifarious perturbations. Our framework allows us to judge whether a multiple-input-multiple-output reaction network is robust against large perturbations of network parameters and enables the predictive design of perfectly robust synthetic network architectures. Utilizing the Escherichia coli chemotaxis pathway as a hallmark example, we provide experimental evidence that our framework indeed allows us to unravel the topological organization of robust signaling. We demonstrate that the specific organization of the pathway allows the system to maintain global concentration robustness of the diffusible response regulator CheY with respect to several dominant perturbations. Our framework provides a counterpoint to the hypothesis that cellular function relies on an extensive machinery to fine-tune or control intracellular parameters. Rather, we suggest that for a large class of perturbations, there exists an appropriate topology that renders the network output invariant to the respective perturbations

Interobserver Agreement in the Diagnosis of Stroke Type

Interobserver Agreement is Essential to the Reliability of Clinical Data from Cooperative Studies and Provides the Foundation for Applying Research Results to Clinical Practice. in the Stroke Data Bank, a Large Cooperative Study of Stroke, We Sought to Establish the Reliability of a Key Aspect of Stroke Diagnosis: The Mechanism of Stroke. Seventeen Patients Were Evaluated by Six Neurologists. Interobserver Agreement Was Measured When Diagnosis Was based on Patient History and Neurologic Examination Only, as Well as When It Was based on Results of a Completed Workup, Including a Computed Tomographic Scan. Initial Clinical Impressions, based Solely on History and One Neurologic Examination, Were Fairly Reliable in Establishing the Mechanism of Stroke (Ie, Distinguishing among Infarcts, Subarachnoid Hemorrhages, and Parenchymatous Hemorrhages). Classification into One of Nine Stroke Subtypes Was Substantially Reliable When Diagnoses Were based on a Completed Workup. Compared with Previous Findings for the Same Physicians and Patients, the Diagnosis of Stroke Type Was Generally More Reliable Than Individual Signs and Symptoms. These Results Suggest that Multicentered Studies Can Rely on the Independent Diagnostic Choices of Several Physicians When Common Definitions Are Employed and Data from a Completed Workup Are Available. Furthermore, Reliability May Be Less for Individual Measurements Such as Signs or Symptoms Than for More-Complex Judgments Such as Diagnoses. © 1986, American Medical Association. All Rights Reserved

Interobserver Reliability in the Interpretation of Computed Tomographic Scans of Stroke Patients

Interobserver Reliability in Interpretation of Computed Tomographic Images Was Studied by Six Senior Neurologists Who Independently Evaluated on a Standardized Stroke Data Bank Form the Brain Lesions of 17 Patients. the Results Analyzed with K Statistics Yielded Moderate to Substantial Agreement on Most Items of Interest Including the Stroke Pathology and Anatomy. in General, the Levels of Agreement Were as High as Previously Reported for the Diagnosis of the Mechanism of the Stroke, and Much Higher Than on Many Stroke History Items and Items of Neurologic Examination. Excellent Agreement Was Obtained for the Detection of Infarcts and Intracerebral Hemorrhage, and Substantial Agreement Was Obtained on Whether the Computed Tomographic Images Were Normal or Indicative of Small Deep Infarcts, Superficial and Deep Infarcts, and Aneurysms. the Level of Agreement on Anatomy of the Lesions Was Best for the Frontal, Parietal, and Temporal Lobes, Putamen, Cerebellum, and Subarachnoid Space. Implications for Clinical Research and Diagnosis Are Discussed. © 1987 American Medical Association All Rights Reserved

Interobserver Variability in the Assessment of Neurologic History and Examination in the Stroke Data Bank

Interobserver Reliability in Obtaining Neurologic Histories and Examinations Was Investigated among Neurologists Collaborating in the Stroke Data Bank (SDB). Seventeen In-Hospital Stroke Patients Were Examined by Six Neurologists Experienced in Stroke over the Course of Three Days. Patients Were Examined Twice a Day for Two Successive Days, with Each Patient Seen by Four Different Neurologists. Data Were Recorded on SDB Forms, According to Definitions and Procedures Established for the SDB. Percent Agreement and Κ Coefficients Were Calculated to Assess the Levels of Agreement for Each Item. Important Differences in Levels of Agreement Were Found among Items on Both Neurologic History and Examination. Agreement among Neurologists Was Higher for Neurologic Examination Than for History. Patterns of Agreement for Items with Low Prevalence or with Numerous Unknown Ratings Are Discussed. Improvement in Interobserver Agreement Due to Data Editing for Intra-Observer Consistency Was Shown. © 1985, American Medical Association. All Rights Reserved

Design of high-magnetic field gradient sources for controlling magnetically induced flow of ferrofluids in microfluidic systems

The use of miniature electromagnets for ferrofluid-actuated liquid dispensing into microfluidic channels has been investigated by numerical simulations using the finite element method and measurements of fluid displacement and flow rate. The simulations illustrate the effect of structural and geometrical parameters of single and paired solenoid coils on the magnetic force experienced by the ferrofluid. Dual solenoids were used for extended fluid displacement. Ferrofluid positioning and flow rates were controlled also by using a solenoid with an iron core. The experimental measurements of fluidflow in capillaries were used to validate the modeling calculations. The results can be used as a basis for the development of on-chip ferrofluid-based devices integrated with microfluidic architectures