Trap-related frequency dispersion of zero-bias microwave responsivity at low temperature in GaN-based self-switching diodes.

The zero-bias microwave detection capability of self-switching diodes (SSDs) based on AlGaN/GaN is analyzed in a wide temperature range, from 10 K to 300 K. The measured responsivity shows an anomalous enhancement at low temperature, while the detected voltage exhibits a roll-off in frequency, which can be attributed to the presence of surface and bulk traps. To gain a deep insight into this behavior, a systematic DC and AC characterization of the diodes has been carried out in the mentioned temperature range. DC results confirm the existence of traps and AC measurements allow us to identify their properties. In particular, impedance studies enable to distinguish two types of traps: at the lateral surfaces of the channel, with a wide spread of relaxation times, and in the bulk.

Deterministic and time resolved thermo-magnetic switching in a nickel nanowire.

Heating a ferromagnetic material is often perceived as detrimental for most applications. This is indeed the case for modern nano-scaled spintronic devices which are operated solely (at least ideally) by an electric current. Heat is a by-product of the current-driven operation and it deteriorates many functionalities of the device. A large scientific and technological effort is devoted these days to avoid heat in modern magnetic nano devices. Here we show that heat can be used to provide an additional and useful degree of freedom in the control of the local magnetization at the nanoscale. In a ferromagnetic nanowire, temperature is used to induce a magnetic switching through a perfectly deterministic mechanism. The nucleation of the magnetic domain walls that triggers the switching can be achieved at a field considerably smaller than the nucleation field and, importantly, the exact moment of the magnetic switching can be pre-determined with nanosecond precision by controlling the power delivered locally to the switching area. With the help of micromagnetic simulations and a theoretical model, we provide an accurate explanation of how this deterministic thermo-magnetic switching operates. The concepts described in this work may lead to an increased functionality in magnetic nano-devices based on magnetic domain walls.

A unified approach to the design of clinical reporting systems.

Computer-based Clinical Reporting Systems (CRS) for diagnostic departments that use structured data entry have a number of functional and structural affinities suggesting that a common software architecture for CRS may be defined. Such an architecture should allow easy expandability and reusability of a CRS. We report the development methodology and the architecture of SISCOPE, a CRS originally designed for gastrointestinal endoscopy that is expandable and reusable. Its main components are a patient database, a knowledge base, a reports base, and screen and reporting engines. The knowledge base contains the description of the controlled vocabulary and all the information necessary to control the menu system, and is easily accessed and modified with a conventional text editor. The structure of the controlled vocabulary is formally presented as an entity-relationship diagram. The screen engine drives a dynamic user interface and the reporting engine automatically creates a medical report; both engines operate by following a set of rules and the information contained in the knowledge base. Clinical experience has shown this architecture to be highly flexible and to allow frequent modifications of both the vocabulary and the menu system. This structure provided increased collaboration among development teams, insulating the domain expert from the details of the database, and enabling him to modify the system as necessary and to test the changes immediately. The system has also been reused in several different domains.

Modification of the OMED nomenclature: a system approach based on the SISCOPE data model.

The OMED nomenclature represented a turning point in endoscopic computer systems by supplying software developers with an internationally recognized scientific document on which prototypes could be based. The main pitfalls of the OMED system are related to its hierarchical structure, probably not the most effective design to represent endoscopic findings. Based on our experience during the development of SISCOPE, an integrated data management system for endoscopy, an alternative scheme is proposed: Endoscopic descriptions are modeled as a set of objects represented by a data structure whose elements are location, morphology, associated lesions and hemorrhage. 72 objects appear to be sufficient for an accurate representation of all endoscopic scenes and a consistent data model could be created with this approach. Efforts should be made to decrease redundancy in the OMED nomenclature, but extension to other endoscopic data types, such as clinical and pathological diagnosis, is more urgently required. Furthermore, if data exchange between systems is desired, the definition of an Endoscopy Metafile is an absolute requirement.

Longitudinal comparative study on the influence of computers on reporting of clinical data.

The impact of the clinical database system SISCOPE on medical services was evaluated and objective data compiled on the quality of information recording and reporting using a fully structured data entry system compared to traditional free text reporting. 1565 upper endoscopy reports produced with SISCOPE over a period of 12 months were assessed for completeness and compared to 152 and 208 free text reports done 4 months before and 1 month after the study period, respectively. Data on four common gastrointestinal findings (esophageal varices, ulcers, polyps and tumors) were evaluated. Physicians' compliance with the new system was good, as reflected by a constant level of quality of reporting over time, although a very slight decline in the ratio of computer generated reports to the total number of examinations was noted. Structured reports had an 18% missing data rate and contained 60% more relevant information than free text reports, which had a 48% missing data rate. No educational effect of the system was seen as missing data rates returned to pre-computerization levels just one month after the end of the study. It is concluded that menu-driven structured data entry systems result in production of far superior reports as compared to free text systems, probably due to their reminder effect.

SISCOPE: a multiuser information system for gastrointestinal endoscopy.

SISCOPE is an integrated data management system for use in gastrointestinal endoscopy units which operates in the multiuser mode on UNIX minicomputers or MS-DOS personal computers and can be used for patient bookings, endoscopic data entry and retrieval, and automatic report generation in upper gastrointestinal endoscopy, proctologic examinations, colonoscopy and peritoneoscopy. The description of endoscopic findings is remarkably detailed and data entry very rapid due to an advanced design of input screens that incorporates several recent concepts, including windows, menu bars and pull-down menus; typing is eliminated as data is entered with a mouse by pointing at options within menus. Endoscopic findings can be described under eight headings: morphology, topography, qualifiers, modifiers, signs of bleeding, endoscopic diagnosis, pathological diagnosis and etiology. Terminology is based strictly 3on the OMED system. SISCOPE also allows recording of details on endoscopic procedures, indications for the examination, preparation, premedication, complications and late entry of pathology reports. After entering all data, a report in natural language is produced automatically, the entire process taking one minute on average. Data retrieval programs give on-line access to previous examinations of a given patient and automatically generate activity reports. A formal language allows direct queries to the database and transfer of data for statistical analysis or other data processing. The system is simple to learn and use because operation is intuitive and all endoscopic techniques share the same basic menu structure and screen design.

[Structuring a clinical information system for hospital services: BASELINE]. / Estrutura de um sistema de informação clínica para serviços hospitalares: BASELINE.

Clinical database systems have been in use since 1972, but they still fail to meet most of the requirements they were aimed at. This includes not only the management of administrative tasks, but particularly the support of medical activities. Our study presents an experimental model of a clinical database system for general hospitals, mainly dedicated to the support of some basic, fundamental clinical activities, namely the management of baseline patient data. This model is based on a modular concept, and its core is represented by a Minimal Data Base Set designed to meet the specific requirements of each Department and of each distinct area within a Department. The system does not interfere with routine clinical work and tries to offer a high level of services to users. A number of utilitary programs simplify user interaction with the system, such as a menu-driven data-entry program, a semi-automatic codification program that follows the OMS/ICD-9-CM coding system, and a menu-driven program for data retrieval. Basically, this system can be helpful for the automatic edition of clinical reports and the retrieval of patient records meeting conditions specified by the clinician.