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Papers by Peter Johnson

Research paper thumbnail of Resume Peter Ralph Johnson

Research paper thumbnail of Elevated platelet factor 4 and β-thromboglobulin plasma levels in depressed patients with ischemic heart disease

Biological Psychiatry, 1997

Clinical depression has recently been recognized as an independent risk factor for cardiac mortal... more Clinical depression has recently been recognized as an independent risk factor for cardiac mortality in patients after myocardial infarction. The underlying mechanisms of this increased mortality remain unclear. This study investigated the hypothesis that patients suffering from ischemic heart disease (IHD) and depression concurrently may have abnormal platelet activation resulting in an increased risk of thrombosis. Platelet factor 4 (PF4) and fS-thromboglobulin (fA-TG) were measured in young healthy control subjects, in nondepressed patients with IHD, and in depressed patients with IHD. Mean PF4 and ~-TG plasma levels in the IHD group with depression were found to be significantly higher than those of the control and IHD groups. This increase was not related to age, gender, racial difference, aspirin use, or severity of cardiac disease. This finding suggests that in depressed patients with IHD there is greater platelet activation, and may indicate an increased risk of thrombotic complications.

Research paper thumbnail of Heparin-coated cardiopulmonary bypass circuits: Hemostatic alterations and postoperative blood loss

Annals of Thoracic Surgery, 1994

Research paper thumbnail of Asbru: A Task-Specific, Intention-Based, and Time-Oriented Language for Representing Skeletal Plans

Abstract: Skeletal plans are a powerful way to reuse existing domain-specific procedural knowledg... more Abstract: Skeletal plans are a powerful way to reuse existing domain-specific procedural knowledge. They are instantiated and refined dynamically over time. In the Asgaard project, we are investigating a set of tasks that support the design and the execution of skeletal plans ...

Research paper thumbnail of Comparing Computer-Interpretable Guideline Models: A CaseStudy Approach

Many groups are developing computer-interpretable clinical guidelines (CIGs) for use during clini... more Many groups are developing computer-interpretable clinical guidelines (CIGs) for use during clinical encounters. CIGs use "Task-Network Models" for representation but differ in their approaches to addressing particular modeling challenges. We have studied similarities and differences between CIGs in order to identify issues that must be resolved before a consensus on a set of common components can be developed.

Research paper thumbnail of The Asgaard project: a task-specific framework for the application and critiquing of time-oriented clinical guidelines

Artificial Intelligence in Medicine, 1998

Clinical guidelines can be viewed as generic skeletal-plan schemata that represent clinical proce... more Clinical guidelines can be viewed as generic skeletal-plan schemata that represent clinical procedural knowledge and that are instantiated and refined dynamically by care providers over significant time periods. In the Asgaard project, we are investigating a set of tasks that support the application of clinical guidelines by a care provider other than the guideline's designer. We are focusing on application of the guideline, recognition of care providers' intentions from their actions, and critique of care providers' actions given the guideline and the patient's medical record. We are developing methods that perform these tasks in multiple clinical domains, given an instance of a properly represented clinical guideline and an electronic medical patient record. In this paper, we point out the precise domain-specific knowledge required by each method, such as the explicit intentions of the guideline designer (represented as temporal patterns to be achieved or avoided). We present a machine-readable language, called Asbru, to represent and to annotate guidelines based on the task-specific ontology. We also introduce an automated tool for acquisition of clinical guidelines based on the same ontology, developed using the PROTÉGÉ-II framework.

Research paper thumbnail of Comparing Computer-interpretable Guideline Models: A Casestudy Approach

Journal of The American Medical Informatics Association, 2003

Objectives: Computer-interpretable clinical guidelines (CIGs) are being developed to support deci... more Objectives: Computer-interpretable clinical guidelines (CIGs) are being developed to support decisionmaking during clinical encounters. CIGs use "Task-Network Models" for representation but differ in their approaches to addressing particular modeling challenges. Our purpose has been to understand commonalitie s and differences, so as to identify issues to be resolved if a consensus on a set of common components is to be developed.

Research paper thumbnail of Differing emotional response from right and left hemispheres

Research paper thumbnail of Validation of highly discriminating multiplex short tandem repeat amplification systems for individual identification

Electrophoresis, 1996

Short tandem repeat (STR) loci are routinely employed for individual identification. We have exam... more Short tandem repeat (STR) loci are routinely employed for individual identification. We have examined the performance and reproductibility of a highly informative co-amplification system containing the tetranucleotide STR loci: HUMVWFA31/A, HUMTH01, D20S85, D8S1179, HUMFIBRA, D21S11, and D18S51, in conjunction with the amelogenin sex test, in addition to a modified system omitting the locus D20S85. Polymerase chain reaction (PCR) products were fluorescently detected on an automated sequencer and automatically sized against an internal size standard by Genescan software. Both systems were routinely able to type 500 pg of undegraded DNA. At DNA concentrations between 50–500 pg, partial profiles were produced, but no allelic drop-out was observed. Balanced amplification of all loci occurred over a wide range of DNA concentrations from 50 pg to 10 ng. Alteration of reagent concentrations and cycling parameters from optimal resulted in variation in the efficiency of individual locus amplification relative to the other loci within the system. This was also observed at high ionic strength or extreme pH. However, at all reagent concentrations and conditions, allelic drop-out was not observed. These multiplex systems have potential in both routine forensic and intelligence database applications.

Research paper thumbnail of Resume Peter Ralph Johnson

Research paper thumbnail of Resume Peter Ralph Johnson

Research paper thumbnail of Elevated platelet factor 4 and β-thromboglobulin plasma levels in depressed patients with ischemic heart disease

Biological Psychiatry, 1997

Clinical depression has recently been recognized as an independent risk factor for cardiac mortal... more Clinical depression has recently been recognized as an independent risk factor for cardiac mortality in patients after myocardial infarction. The underlying mechanisms of this increased mortality remain unclear. This study investigated the hypothesis that patients suffering from ischemic heart disease (IHD) and depression concurrently may have abnormal platelet activation resulting in an increased risk of thrombosis. Platelet factor 4 (PF4) and fS-thromboglobulin (fA-TG) were measured in young healthy control subjects, in nondepressed patients with IHD, and in depressed patients with IHD. Mean PF4 and ~-TG plasma levels in the IHD group with depression were found to be significantly higher than those of the control and IHD groups. This increase was not related to age, gender, racial difference, aspirin use, or severity of cardiac disease. This finding suggests that in depressed patients with IHD there is greater platelet activation, and may indicate an increased risk of thrombotic complications.

Research paper thumbnail of Heparin-coated cardiopulmonary bypass circuits: Hemostatic alterations and postoperative blood loss

Annals of Thoracic Surgery, 1994

Research paper thumbnail of Asbru: A Task-Specific, Intention-Based, and Time-Oriented Language for Representing Skeletal Plans

Abstract: Skeletal plans are a powerful way to reuse existing domain-specific procedural knowledg... more Abstract: Skeletal plans are a powerful way to reuse existing domain-specific procedural knowledge. They are instantiated and refined dynamically over time. In the Asgaard project, we are investigating a set of tasks that support the design and the execution of skeletal plans ...

Research paper thumbnail of Comparing Computer-Interpretable Guideline Models: A CaseStudy Approach

Many groups are developing computer-interpretable clinical guidelines (CIGs) for use during clini... more Many groups are developing computer-interpretable clinical guidelines (CIGs) for use during clinical encounters. CIGs use "Task-Network Models" for representation but differ in their approaches to addressing particular modeling challenges. We have studied similarities and differences between CIGs in order to identify issues that must be resolved before a consensus on a set of common components can be developed.

Research paper thumbnail of The Asgaard project: a task-specific framework for the application and critiquing of time-oriented clinical guidelines

Artificial Intelligence in Medicine, 1998

Clinical guidelines can be viewed as generic skeletal-plan schemata that represent clinical proce... more Clinical guidelines can be viewed as generic skeletal-plan schemata that represent clinical procedural knowledge and that are instantiated and refined dynamically by care providers over significant time periods. In the Asgaard project, we are investigating a set of tasks that support the application of clinical guidelines by a care provider other than the guideline's designer. We are focusing on application of the guideline, recognition of care providers' intentions from their actions, and critique of care providers' actions given the guideline and the patient's medical record. We are developing methods that perform these tasks in multiple clinical domains, given an instance of a properly represented clinical guideline and an electronic medical patient record. In this paper, we point out the precise domain-specific knowledge required by each method, such as the explicit intentions of the guideline designer (represented as temporal patterns to be achieved or avoided). We present a machine-readable language, called Asbru, to represent and to annotate guidelines based on the task-specific ontology. We also introduce an automated tool for acquisition of clinical guidelines based on the same ontology, developed using the PROTÉGÉ-II framework.

Research paper thumbnail of Comparing Computer-interpretable Guideline Models: A Casestudy Approach

Journal of The American Medical Informatics Association, 2003

Objectives: Computer-interpretable clinical guidelines (CIGs) are being developed to support deci... more Objectives: Computer-interpretable clinical guidelines (CIGs) are being developed to support decisionmaking during clinical encounters. CIGs use "Task-Network Models" for representation but differ in their approaches to addressing particular modeling challenges. Our purpose has been to understand commonalitie s and differences, so as to identify issues to be resolved if a consensus on a set of common components is to be developed.

Research paper thumbnail of Differing emotional response from right and left hemispheres

Research paper thumbnail of Validation of highly discriminating multiplex short tandem repeat amplification systems for individual identification

Electrophoresis, 1996

Short tandem repeat (STR) loci are routinely employed for individual identification. We have exam... more Short tandem repeat (STR) loci are routinely employed for individual identification. We have examined the performance and reproductibility of a highly informative co-amplification system containing the tetranucleotide STR loci: HUMVWFA31/A, HUMTH01, D20S85, D8S1179, HUMFIBRA, D21S11, and D18S51, in conjunction with the amelogenin sex test, in addition to a modified system omitting the locus D20S85. Polymerase chain reaction (PCR) products were fluorescently detected on an automated sequencer and automatically sized against an internal size standard by Genescan software. Both systems were routinely able to type 500 pg of undegraded DNA. At DNA concentrations between 50–500 pg, partial profiles were produced, but no allelic drop-out was observed. Balanced amplification of all loci occurred over a wide range of DNA concentrations from 50 pg to 10 ng. Alteration of reagent concentrations and cycling parameters from optimal resulted in variation in the efficiency of individual locus amplification relative to the other loci within the system. This was also observed at high ionic strength or extreme pH. However, at all reagent concentrations and conditions, allelic drop-out was not observed. These multiplex systems have potential in both routine forensic and intelligence database applications.

Research paper thumbnail of Resume Peter Ralph Johnson