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K Weller

Publications and source records attributed to K Weller.

15 recordsLinked to original sources
PubMed2004

Prediction of cardiovascular risk in hemodialysis patients by data mining.

OBJECTIVES: The objective of this work was to contribute to the development, validation and application of data mining methods for prediction in decision support systems in medicine. The particular focus was on the prediction of cardiovascular risk factors in hemodialysis patients, specifically the interventricular septum (IVS) thickness of the heart of individual patients as an important quantitative indicator to diagnose left ventricular hypertrophy. The work was based on data from 63 long-term hemodialysis patients of the KfH Dialysis Centre in Jena, Germany. METHODS: The approach applied is based on data mining methods and involves four major steps: data based clustering, cluster based rule extraction, rulebase construction and cluster and rule based prediction. The methods employed include crisp and fuzzy algorithms. At each step, logical and medical validation of results was carried out. Different sets of randomly selected patient data were used to train, test and optimize the clusterbases and rulebases for prediction. RESULTS: Using the best clusterbase/rulebase combination designed, the IVS thickness cluster ('small' or 'large') was predicted correctly for 30 of the 35 patients with known IVS values in the training data set; no patient was predicted incorrectly and 5 were parity predicted. For the test data set, 4 of the 6 patients with known IVS values were predicted correctly, no patient incorrectly and 2 parity. These results did not substantially differ from those obtained using the second best clusterbase/rulebase combination which was finally recommended for use based on further performance criteria. The prediction of the IVS thickness clusters of the 22 patients with unknown IVS values also yielded good results that were (and could only be) validated by a medical individual risk assessment of these patients. CONCLUSIONS: The approach applied proved successful for the cluster and rule based prediction of a quantitative variable, such as IVS thickness, for individual patients from other variables relevant to the problem. The results obtained demonstrate the high potential of the approach and the methods developed and validated to support decision-making in hemodialysis and other fields of medicine by individual risk prediction.

Algorithms↗
PubMed1999

Avascular necrosis of the femoral head after open reduction and internal fixation of femoral neck fractures: an inevitable complication?

Between 1980 and 1989 71 patients with a femoral neck fracture were treated at the University Hospital of Basel by a Dynamic Hip Screw (n = 54) or by three compression screws (n = 17). Fifty out of 71 patients (70%) were reviewed clinically and radiologically after an average of 116 months. 32/50 fractures (64%) had united. In 18/50 (36%) either avascular necrosis (12) or secondary fracture dislocation (6) had resulted in failure after an average of 29 months following injury. Despite these results, the patients assessment had been very good or good in 44 patients (88%) and fair only in six patients (12%). The cause of secondary dislocation proved to be mainly due to a technical failure at surgery. The incidence of avascular necrosis was significantly higher in displaced fractures compared to non-displaced fractures (p < 0.05), regardless of the quality of the reduction achieved (varus or valgus) or the time delay between accident and operation. However it was interesting to note, that more than one third of all avascular necrosis became apparent more than 3 years (4-10 years) after the accident.

Adult↗
PubMed1994

Promoter strength prediction based on occurrence frequencies of consensus patterns.

A training sample of 14 sequences of E. coli, each 70 or 69 base pairs long, with their (relative) promoter strengths given by Deuschle et al. (1986, EMBO J. 5, 2987-2994), is used to find a relation between the occurrence frequencies of the two consensus patterns and the promoter strength. The approach is restricted to an analysis of purine and pyrimidine organization using the theory of stationary alternate Markov chains of first order. Further, it is shown, both empirically by regression analysis, and by a Markov-chain-oriented statistical analysis, that the difference of occurrence frequencies and the determinant of transition matrix, which was introduced in a previous paper (Recknagel et al., 1993, J. theor. Biol. 162, 75-80), are equivalent measures with respect to the task of promoter strength prediction. An empirical regression equation is given that allows the promoter strength to be forecast from the occurrence frequencies of the canonical hexamers in the consensus boxes. Three E. coli promoters of an examination sample, separated from the training sample, are classified this way, in agreement with the experimental findings.

Bacterial Proteins↗
PubMed1993

A simple method to forecast good promoters of Escherichia coli by means of doublet frequencies.

A training sample (taken offhand) of 14 promoter sequences, 70 or 69 base pairs in length each, with their (relative) promoter strengths given by Deuschle et al. (1986), is used to find a relation between some sequence characteristics and the promoter strength. The analysis is based on the doublet frequencies of purines and pyrimidines in the promoter sequence under study.

Escherichia coli↗
PubMed1991

Wound management.

Explore the source record for details and available documents.

Clinical Protocols↗
PubMed1988

Phosphate catalyzed exchange rates of NH-N protons of DNA.

We have studied the catalysis of the exchange of the hydrogen-bonded NH-N protons of the short DNA helix (d-CCAAGCTTGG)2 by phosphate addition. The NH exchange rates were monitored by the line widths of the corresponding NH resonances in the 1H nmr spectra. The exchange catalyst phosphate is most effective on the exchange rate of the terminal CG1 base pairs. However, all internal base pairs are also moderately affected by phosphate which suggests an exchange mechanism governed by a fast equilibrium between opened and closed states of the duplex. Within the limits of error the same effectiveness of phosphate on the exchange rate of all internal NH-N protons has been observed. With the exception of the terminal base pairs, no sequence and/or position specificity of the exchange rates of the NH-N protons of the base pairs has been found.

Base Sequence↗
PubMed1980

On the interaction of caffeine with nucleic acids. III. 1H NMR studies of caffeine--5'-adenosine monophosphate and caffeine-poly(riboadenylate) interactions.

1) The self-association of both caffeine (Cf) and 5'-adenosine monophosphate (AMP) in aqueous solution has been reinvestigated by 1H NMR. The self-association process is characterized by an isodesmic model. The apparent self-association constants of the vertical stacking process are KCf = (10.6 +/- 1.0) M-1 and KAMP = (1.67 +/- 0.17) M-1. The arrangement of the monomeric units in the stacked aggregates is discussed in terms of isoshielding curves theoretically calculated by Giessner-Prettre and Pullman. Models are proposed which are consistent with these and further previous NMR data. 2) The interaction of Cf and AMP has been studied by 1H NMR. The apparent association constant of the complex Cf-AMP is KC-A = (7.3 +/- 1.2) M-1. Two models of the mutual arrangement of AMP and Cf in the complex are proposed on the basis of the calculated isoshielding curves considering both ring current and local atomic diamagnetic anisotropy effects. 3) The interaction of Cf and poly(riboadenylate), (rA)n, is indicated by a downfield shift of the H-8 line but an upfield shifts of the H-2 line in the 1H NMR spectra of (rA)n. The concentration dependence of the 1H NMR shifts of both Cf and (rA)n can be explained by the existence of two binding mechanisms. We suggest (i) partial insertion of Cf between adjacent base residues of ordered single-stranded regions of (rA)n and (ii) outside binding of Cf in form of monomeric Cf as well as of self-associated aggregates. The complex geometry of insertion proposed on the basis of the calculated isoshielding curves is characterized by a stronger overlapping of the Cf ring and the H-2 proton of (rA)n as compared to the H-8 proton.

Adenosine Monophosphate↗
PubMed1977

Life events and illness: a three year prospective study.

In an investigation of the relation between life events (stressors) and illness, 87 medical students reported on a prospective basis their health and life events history over a three year period. There were a few positive findings, e.g. that subjects who reported more life events during the period also reported more illnesses during that period. Overall, however, the study showed a lack of statistically significant association between life events and illness.

Adult↗
PubMedDate not supplied

In search of efficacy and efficiency. An alternative to conventional wound cleansing modalities.

Based upon the above results, Dey-Wash was found to be an effective wound cleansing agent. In over 80% of the patients, it cleansed the wound of exudate and debris in less than half the time and without the effort or abundance of materials required by the bulb syringe method. While splashback was reported by some nurses, this risk exists for all methods. Inservicing and protocols based on universal precautions will decrease the occurrence of this problem. As nurses became familiar with the proper angle and distance for applying the Dey-Wash, the problem of splashback became more manageable. Effective wound cleansing is a very necessary step in the wound healing process. The literature clearly describes the importance and variances of this practice in terms of different methodologies. Knowledge of the current literature concerning wound irrigation can guide nursing actions. Emphasis continues to be placed on appropriate utilization of nursing time and materials. Therefore, it is in the best interest of healthcare providers to evaluate new materials and methods in order to maximize care and facilitate optimum wound healing.

Detergents↗