Frequency, causes, and outcome of home ventilator failure

STUDY OBJECTIVES: The safety of home ventilators has been questioned. We collected data to study the following: frequency of home ventilator failure, apparent causes for the failure or malfunction, and adverse consequences following the failure. STUDY DESIGN: Information on all requests to correct home ventilator failures reported to a home respiratory equipment vendor was collected prospectively between November 1991, and November 1992. PATIENTS: There were 150 ventilator-assisted patients aged 2 to 77 years; 44 were < or = 18 years. They received 841,234 h of home mechanical ventilation (average, 15.4 h/d per ventilator-assisted patient). RESULTS: There were 189 reports of home ventilator failure. Defective equipment or mechanical failure was found in only 39% (73 reports), equivalent to one home ventilator failure for every 1.25 years of continuous use. Other causes of ventilator failure included the following: improper care, damage, or tampering with the ventilator by caregivers (13%), functional equipment improperly used by caregivers (30%), and equipment functional but the patient's condition changed, mimicking ventilator failure (3%). No problem could be identified in 16%. The following actions were required: ventilator replacement (44%), repair of a defective part (6%), replacement of a functioning ventilator for psychological comfort (14%), ventilator adjustments made (21%), caregiver reeducation (7%), caregiver anxiety or distress reduced (3%), and no action required (4%). Hospitalization was required only in two cases (1%). No adverse outcomes, deaths, or serious injuries were associated with home ventilator failure. CONCLUSIONS: We conclude that in 150 patients requiring home mechanical ventilation, ventilator failure occurred relatively infrequently, and there were no adverse outcomes as a result of equipment failure at home. We speculate that equipment failure is not a frequent or serious problem for ventilator-assisted patients treated at home.     

Hidrocolonic ultrasonography in the detection of tumoral processes in the inferior gastrointestinal tract

OBJECTIVES: To determine the value of hidrocolonic ultrasound in the detection of proliferative lesions in the colon and to compare it with other techniques of already proven value. MATERIAL AND METHODS: We performed a prospective blinded trial including 155 patients (82 males and 73 females) with ages ranging from 33 to 94 years (average of 58) and clinical and analytical criteria suggesting the existence of colonic proliferative lesions. Patients with rectal mass or those with deficient bowel preparation were excluded. Ultrasound findings were compared to those obtained by colonoscopy (133 cases) and by Barium RX studies (22 cases) and all diagnoses were always confirmed by histologic exams. RESULTS: 155 patients were studied. 50 of them had cancer and 46 of these 50 were diagnosed by Hidrocolonic Ultrasound (92%); 19 had polyps > 7 mm. and 15 of these (78.9%) were diagnosed by Hidrocolonic Ultrasound. Hidrocolonic Ultrasound failed to detect all the polyps < 7 mm. The overall sensitivity, specificity, positive predictive value and negative predictive value for identifying colon carcinoma were 92%, 98%, 95.8% and 96.2% respectively and for polyps > 7 mm were 78.9%, 100%, 100% and 97.1%, respectively. The mean time for examination was 14 minutes. Tolerance was good in 114 patients (73.5%), 29 showed a slight discomfort (18.7%) and 12 (7.7%) showed a great discomfort. There were no complications. CONCLUSIONS: Hidrocolonic ultrasound is an innocuous, fast, well tolerated technique for detecting colonic proliferative lesions > 7 mm H.U. can be considered as a useful complementary technique to other more expensive and invasive ones, such as barium RX studies and Colonoscopy.     

Ursolic acid from Plantago major, a selective inhibitor of cyclooxygenase-2 catalyzed prostaglandin biosynthesis

A hexane extract of Plantago major was investigated by bioactivity-directed fractionation, using an in vitro cyclooxygenase-2 (COX-2) catalyzed prostaglandin biosynthesis inhibition assay, and resulted in the isolation of ursolic acid (1). This triterpenoid showed a significant COX-2 inhibitory effect, directly on the enzyme activity, with an IC50 value of 130 microM and a COX-2/COX-1 selectivity ratio of 0.6. The structural isomer oleanolic acid (2) was found to be less active than 1, with an IC50 value of 295 microM, but showed a similar selectivity ratio (0.8). Furthermore, no significant inhibition on COX-2 or COX-1 was observed by the triterpenoid, 18beta-glycyrrhetinic acid (3). The direct inhibitory effect of 1 and 2 on COX-2 catalyzed prostaglandin biosynthesis increased with preincubation, indicating a time-dependent inhibition, while the effect on COX-1 was found to be independent of preincubation time.     

Associative Memories in Infinite Dimensional Spaces

A generalization of the Little–Hopfield neural network model for associative memories is presented that considers the case of a continuum of processing units. The state space corresponds to an infinite dimensional euclidean space. A dynamics is proposed that minimizes an energy functional that is a natural extension of the discrete case. The case in which the synaptic weight operator is defined through the autocorrelation rule (Hebb rule) with orthogonal memories is analyzed. We also consider the case of memories that are not orthogonal. Finally, we discuss the generalization of the non deterministic, finite temperature dynamics.     

Scalability and robustness of parallel hyperheuristics applied to a multiobjectivised frequency assignment problem

The Frequency Assignment Problem (fap) is one of the key issues in the design of Global System for Mobile Communications (gsm) networks. The formulation of the fap used here focuses on aspects that are relevant to real gsm networks. In this paper, we adapt a parallel model to tackle a multiobjectivised version of the fap. It is a hybrid model which combines an island-based model and a hyperheuristic. The main aim of this paper is to design a strategy that facilitates the application of the current best-behaved algorithm. Specifically, our goal is to decrease the user effort required to set its parameters. At the same time, the usage of such an algorithm in parallel environments was enabled. As a result, the time required to attain high-quality solutions was decreased. We also conduct a robustness analysis of this parallel model. In this analysis we study the relationship between the migration stage of the parallel model and the quality of the resulting solutions. In addition, we also carry out a scalability study of the parallel model. In this case, we analyse the impact that the migration stage has on the scalability of the entire parallel model. Computational results with several real network instances have validated our proposed approach. The best-known frequency plans for two real-world network instances are improved with this strategy.     

Biologically Plausible Associative Memory: Continuous Unit Response + Stochastic Dynamics

A neural network model of associative memory is presented which unifies the two historically more relevant enhancements to the basic Little-Hopfield discrete model: the graded response units approach and the stochastic, Glauber-inspired model with a random field representing thermal fluctuations. This is done by casting the retrieval process of the model with graded response neurons, into the framework of a diffusive process governed by the Fokker-Plank equation, which leads to a Langevin system describing the process at a microscopic level, while the time evolution of the probability density function is governed by a multivariate Fokker Planck equation operating over the space of all possible activation patterns. The present unified approach has two notable features: (i) greater biological plausibility and (ii) ability to escape local minima of energy (associated with spurious memories), which makes it a potential tool for those complex optimization problems for which the previous models failed.     

A scalable architecture for 3D map navigation on mobile devices

Mobile devices such as smart phones or tablets are rapidly increasing their graphics and networking capabilities. However, real-time visualization of 3D maps is still a challenging task to accomplish on such limited devices. In this paper, we describe the principles involved in the design and development of a scalable client–server architecture for delivering 3D maps over wireless networks to mobile devices. We have developed a hybrid adaptive streaming and rendering method that distributes the 3D map rendering task between the mobile clients and a remote server. This architecture provides support for efficient delivery of 3D contents to mobile clients according to their capabilities. As a proof of concept, we have implemented a prototype and carried out exhaustive experiments considering different scenarios and hundreds of concurrent connected clients. The analysis of the server workload and the mobile clients performance show that our architecture achieves a great scalability and performance even when using low-end hardware.     

Typed Mobile Ambients in Maude

Maude has revealed itself as a powerful tool for implementing different kinds of semantics so that quick prototypes are available for trying examples and proving properties. In this paper we show how to define in Maude two semantics for Cardelli and Gordon's Ambient Calculus. The first one is the operational (reduction) semantics which requires the definition of Maude strategies in order to avoid infinite loops. The second one is a type system defined by Cardelli and Gordon to avoid communication errors. The correctness of that system was not formally proved. We enrich the operational semantics with error rules and prove that well-typed processes do not produce such errors. The type system is highly non-deterministic. We show here one possible way of implementing such non-determinism in the rules.     

An empirical analysis of ontology-based query expansion for learning resource searches using MERLOT and the Gene ontology

This paper proposes an expansion of queries based on formal domain ontologies in the context of the search for learning resources in repositories. The expansion process uses the relation types that are represented in these models; common ontological relations, and ontological relations specific to domain and traditional terminology relations, typical of thesauri. The tests were conducted using Gene ontology as the knowledge base and MERLOT is used as the test repository. The results of this study case indicate that, at similar levels of precision, expanded queries improve levels of novelty and coverage compared to the original query (without expansion), i.e. expanded queries allow the user to retrieve relevant objects, which might not be obtained without expansion.