Forward-backward Procedure Research Articles

Post‐traumatic growth in advanced cancer patients receiving palliative care

To develop the Greek version of the Post-traumatic Growth Inventory (PTGI-Gr), and assess its psychometric properties in a palliative care patient sample. The scale was translated with the forward-backward procedure to Greek. It was administered twice, with a 3-day interval, to 131 eligible patients with advanced cancer. Together with the PTGI, the patients also completed the Greek version of the Impact of Events Scale-Revised scale (IES-R-Gr). The reliability was assessed by the internal consistency (Cronbach's alpha coefficients), test/retest (Spearman's r value), and inter-item correlations. Validity was demonstrated by factor analysis, inter-scale correlations, construct validity with the IES-R-Gr, and combined with the Eastern Cooperative Oncology Group (ECOG) performance status. The PTGI-Gr yielded a five-factor structure, explaining 73.5% of the variance. Cronbach's alphas for the five factors ranged from .66 to .87, respectively. Overall test-retest reliability was satisfactory with a range between .85 and .92 (p<.0005), and inter-item correlations ranged between .47 and .63. Inter-scale correlations were found satisfactory (p<.0005, p<.005, and p<.05). Validity as performed using combined validity analysis showed good results. Satisfactory construct validity was supported by the correlation analysis between the PTGI-Gr and the IES-R-Gr scales. PTGI-Gr is an instrument with satisfactory psychometric properties, and is a valid research tool for the post-traumatic growth of advanced cancer patients.

Deutsche Adaptation der “Activities-Specific Balance Confidence (ABC) Scale„ zur Erfassung der sturzassoziierten Selbstwirksamkeit

The present study investigates the psychometric properties and the factorial structure of the German adaptation of the Activities-Specific Balance Confidence (ABC) scale (Powell & Myers, 1995) for the evaluation of falls-related self-efficacy in community-dwelling older adults. The German adaptation of the ABC using a forward-backward procedure was administered to 113 older adults (age 68.9+/-8.5 years). The following internationally accepted instruments were used for validation: The Short Form Health Survey SF 36, the Geriatric Depression Scale (GDS), the Trail Making Test and the Letter Number Sequencing Test, and motor tests (balance, strength, mobility). The internal consistency (0.91-0.95) as well as the test-retest reliability of the subscales was excellent (0.94-0.98). The correlation coefficients with the validation instruments ranged between 0.33 and 0.58. Significant differences in the ABC-D scores were found in older adults with and without falls. Older adults with a recent fall history scored lower on the ABC-D than older adults without a recent fall history. To conclude, the German version of the ABC has properties analogous to the original English version and is apparently useful in assessing falls-related self-efficacy.

A Japanese version of the Perceived Stress Scale: cross-cultural translation and equivalence assessment

BackgroundThis paper describes the development of a Japanese version of the Perceived Stress Scale (PSS), and examines the equivalence between the original and translated version. The PSS is one of the few instruments to measure a global level of perceived stress, and has been widely used in a range of clinical and research settings. The PSS has already been translated into several languages, but there is no validated Japanese version.MethodsA forward-backward procedure was implemented. Multiple forward and backward translations were produced, and a panel of reviewers verified conceptual and semantic equivalence between the source and final versions. Non-professional translators who were not brought up in bilingual families were used in order to enhance representativeness of language in the target populations. The PSS was administered to 222 native English speakers and the Japanese version (PSS-J) to 1320 native Japanese speakers.ResultsFactor analysis showed similar factor loadings of the items and satisfactory factorial agreement between the PSS and PSS-J. Cronbach's alpha coefficient was high for both versions and for each factor.ConclusionIt is concluded that the PSS and PSS-J are substantially equivalent and suited for use in comparative cross-cultural studies.

Online Learning with Hidden Markov Models

We present an online version of the expectation-maximization (EM) algorithm for hidden Markov models (HMMs). The sufficient statistics required for parameters estimation is computed recursively with time, that is, in an online way instead of using the batch forward-backward procedure. This computational scheme is generalized to the case where the model parameters can change with time by introducing a discount factor into the recurrence relations. The resulting algorithm is equivalent to the batch EM algorithm, for appropriate discount factor and scheduling of parameters update. On the other hand, the online algorithm is able to deal with dynamic environments, i.e., when the statistics of the observed data is changing with time. The implications of the online algorithm for probabilistic modeling in neuroscience are briefly discussed.

Translation procedures for standardised quality of life questionnaires: The European Organisation for Research and Treatment of Cancer (EORTC) approach

Background The European Organisation for Research and Treatment of Cancer quality of life (EORTC QL) questionnaires are used in international trials and therefore standardised translation procedures are required. This report summarises the EORTC translation procedure, recent accomplishments and challenges. Methods Translations follow a forward–backward procedure, independently carried out by two native-speakers of the target language. Discrepancies are arbitrated by a third consultant, and solutions are reached by consensus. Translated questionnaires undergo a pilot-testing. Suggestions are incorporated into the final questionnaire. Requests for translations originate from the module developers, physicians or pharmaceutical industry, and most translations are performed by professional translators. The translation procedure is managed and supervised by a Translation Coordinator within the EORTC QL Unit in Brussels. Results To date, the EORTC QLQ-C30 has been translated and validated into more than 60 languages, with further translations in progress. Translations include all major Western, and many African and Asian languages. The following translation problems were encountered: lack of expressions for specific symptoms in various languages, the use of old-fashioned language, recent spelling reforms in several European countries and different priorities of social issues between Western and Eastern cultures. The EORTC measurement system is now registered for use in over 9000 clinical trials worldwide. Conclusions The EORTC provides strong infrastructure and quality control to produce robust translated questionnaires. Nevertheless, translation problems have been identified. The key to improvements may lie in the particular features and strengths of the group, consisting of researchers from 21 countries representing 25 languages and include the development of simple source versions, the use of advanced computerised tools, rigorous pilot-testing, certification procedures and insights from a unique cross-cultural database of nearly 40,000 questionnaire responses.

IDENTIFICATION OF PULSED RADARS USING HIDDEN MARKOV MODEL

In this paper, we propose radar system recognition approach using a HMM. We employ the Baum-Welsh algorithm to search for an HMM which best explains the observed radar signals represented by sequences of 0’s and 1’s. Deterministic periodic sequences (stable PRI radars) are considered. We can obtain an HMM which yields the globally biggest training probability. We can modify the results, to some degree, to create models more robust to observation errors. Preliminary results in combination with either the forward back-ward procedure or the Viterbi algorithm may be adequate for carrying out radar system recognition.

Beck Depression Inventory: exploring its psychometric properties in a palliative care population of advanced cancer patients

To validate the Greek version of the Beck Depression Inventory (BDI)-21 items in advanced cancer patents attending a palliative care unit. The scale was translated with the forward-backward procedure into Greek. It was administered twice, with a 1-week interval, to 105 patients with advanced cancer. The patients also completed the Hospital Anxiety and Depression (HAD) scale, while researchers recorded data on demographic characteristics, disease status and treatment regimen. The Greek version of the BDI had overall Cronbach's alpha 0.906. The most significant correlations were found between BDI and performance status (P < 0.0005), gender (P = 0.031) and family status (P = 0.009). The test-retest reliability in terms of Spearman-rho, Pearson-rho coefficient and Kendall's tau-b was also satisfactory (P < 0.0005). Validity as performed using known-group analysis showed good results. The Inventory discriminated well between subgroups of patients differing in disease severity as defined by the Eastern Cooperative Oncology Group performance status. Correlations between the BDI and the HAD scale was 0.544 for the anxiety subscale and 0.657 for the depression subscale. Multiple regression analysis was conducted and predicted that the contribution of gender, family status and performance status to BDI is high. These psychometric properties of the Greek version of the BDI confirm it as a valid and reliable measure when administered to patients with advanced cancer.

Fast selection of spectral variables with B-spline compression

The large number of spectral variables in most data sets encountered in spectral chemometrics often renders the prediction of a dependent variable uneasy. The number of variables hopefully can be reduced, by using either projection techniques or selection methods; the latter allow for the interpretation of the selected variables. Since the optimal approach of testing all possible subsets of variables with the prediction model is intractable, an incremental selection approach using a nonparametric statistics is a good option, as it avoids the computationally intensive use of the model itself. It has two drawbacks however: the number of groups of variables to test is still huge, and colinearities can make the results unstable. To overcome these limitations, this paper presents a method to select groups of spectral variables. It consists in a forward–backward procedure applied to the coefficients of a B-spline representation of the spectra. The criterion used in the forward–backward procedure is the mutual information, allowing to find nonlinear dependencies between variables, on the contrary of the generally used correlation. The spline representation is used to get interpretability of the results, as groups of consecutive spectral variables will be selected. The experiments conducted on NIR spectra from fescue grass and diesel fuels show that the method provides clearly identified groups of selected variables, making interpretation easy, while keeping a low computational load. The prediction performances obtained using the selected coefficients are higher than those obtained by the same method applied directly to the original variables and similar to those obtained using traditional models, although using significantly less spectral variables.

The European Organisation for Research and Treatment of Cancer (EORTC) translation procedure for standardized quality of life questionnaires

16033 Background: The EORTC Quality of Life (QoL) Group has developed a modular approach to QoL measurement for use in clinical trials in cancer. Questionnaires are used in international trials and standardized translation procedures are therefore required. This report summarizes the EORTC translation procedure, its accomplishments and translation problems. Methods: Translations follow a forward-backward procedure, independently carried out by two native-speakers of the target language. Discrepancies are arbitrated by a third consultant, and solutions are reached by consensus. Translated questionnaires undergo pilot-testing. Suggestions (by patients and users) are incorporated into the final questionnaire version. Most translations are performed by professional translators. The translation procedure is managed and supervised by the Translation Committee within the EORTC QoL Group. Results: To date, the core EORTC QoL questionnaire, the QLQ-C30, has been translated and validated into 62 languages, with a further 12 translations in progress. Translations include all major Western languages, East European languages, Asian languages and also remote languages, such as Xhoza (Africa).The validated, condition-specific questionnaire modules have been translated in up to 37 languages. The following major translation problems were encountered: lack of expressions for specific symptoms in various languages, the quest for formal versus informal versions, recent spelling reforms in several European countries, and different weights of social issues between Western and Eastern cultures. The EORTC measurement system is now registered for use in over 9000 clinical studies in 80 countries worldwide. Conclusions: The EORTC provides a strong infrastructure and methodology to produce high quality translations of their QoL questionnaires for use in international clinical trials. Translation problems have been identified and it will be an important topic for future research to specify whether these problems arise out of procedural/methodological shortcomings or are due to subtle cross-cultural differences in concepts of health, illness and QoL. No significant financial relationships to disclose.

Implementation of a Forward-Backward Procedure for the Fast Analysis of Electromagnetic Radiation/Scattering From Two-Dimensional Large Phased Arrays

Forward-backward method (FBM) was successfully developed for the analysis of electromagnetic radiation/scattering from one-dimensional (1-D) phased array in an efficiency appealing fashion. The FBM applications to treat 2-D array problems are developed in this paper. Acceleration algorithm, performing better than the novel spectrum acceleration algorithm used for 1-D FBM computation, is also developed for this 2-D FBM so the unique advantages of high efficiency and O(N/sub tot/) computational complexity as in the 1-D problems can be retained where N/sub tot/ is the total number of array element. Numerical examples are presented to demonstrate its validity.

Ordered Semantic Hyper Tableaux

A family of tableau methods, called i>ordered semantic hyper (i>OSH) i>tableau methods for first-order theories with function symbols, is presented. These methods permit semantic information to guide the search for a proof. They also may make use of orderings on literals, clauses, and interpretations to guide the search. In a typical tableau, the branches represent conjunctions of literals, and the tableau represents the disjunction of the branches. An OSH tableau is as usual except that each branch i>B has an interpretation i>I0[i>B] associated with it, where i>I0 is an interpretation supplied at the beginning and i>I0[i>B] is the interpretation most like i>I0 that satisfies i>B. Only clauses that i>I0[i>B] falsifies may be used to expand the branch i>B, thus restricting the kinds of tableau that can be constructed. This restriction guarantees the i>goal sensitivity of these methods if i>I0 is properly chosen. Certain choices of i>I0 may produce a purely bottom-up tableau construction, while others may result in goal-oriented evaluation for a given query. The choices of which branch is selected for expansion and which clause is used to expand this branch are examined and their effects on the OSH tableau methods considered. A branch reordering method is also studied, as well as a branch pruning technique called i>complement modification, that adds additional literals to branches in a soundness-preserving manner. All members of the family of OSH tableaux are shown to be sound, complete, and proof convergent for refutations. Proof convergence means that any allowable sequence of operations will eventually find a proof, if one exists. OSH tableaux are powerful enough to be treated as a generalization of several classes of tableau discussed in the literature, including forward chaining and backward chaining procedures. Therefore, they can be used for efficient query processing.

Bayesian Restoration of Ion Channel Records using Hidden Markov Models

Hidden Markov models have been used to restore recorded signals of single ion channels buried in background noise. Parameter estimation and signal restoration are usually carried out through likelihood maximization by using variants of the Baum–Welch forward–backward procedures. This paper presents an alternative approach for dealing with this inferential task. The inferences are made by using a combination of the framework provided by Bayesian statistics and numerical methods based on Markov chain Monte Carlo stochastic simulation. The reliability of this approach is tested by using synthetic signals of known characteristics. The expectations of the model parameters estimated here are close to those calculated using the Baum–Welch algorithm, but the present methods also yield estimates of their errors. Comparisons of the results of the Bayesian Markov Chain Monte Carlo approach with those obtained by filtering and thresholding demonstrate clearly the superiority of the new methods.

An Algorithm for Time-Optimal Control Problems

A numerical procedure to compute nonsingular, time-optimal solutions for nonlinear systems, which have fixed initial and final states, and are linear and bounded in control, is presented. Using the Pontryagin’s Minimum Principle, the corresponding nonlinear two-point boundary-value problem is formulated and solved by combination of the forward-backward and the shooting methods. The forward-backward procedure generates a good guess of the initial costates, which is crucial for the convergence of the shooting method. Numerical example of a two-link manipulator illustrates the proposed approach and the convergence of the procedure.

Identification of hidden Markov models for ion channel currents. II. State-dependent excess noise

For pt.I see ibid., vol.46, no.7, p.1901 (1998). Hidden Markov modeling (HMM) techniques have been applied in the past few years to characterize single ion channel current events at low signal-to-noise ratios (SNRs). In this paper, an adaptation of the forward-backward procedure and Baum-Welch algorithm is presented to model ion channel kinetics under conditions of correlated and state-dependent excess noise like that observed in patch-clamp recordings. An autoregressive with additive nonstationary (ARANS) noise model is introduced to model the experimentally observed noise, and an algorithm called the Baum-Welch weighted least squares (BW-WLS) procedure is presented to re-estimate the noise model parameters along with the parameters of the underlying HMM. The performance of the algorithm is demonstrated with simulated data.

Relative Effectiveness of Concurrent Forward/Backward versus Simple Forward and Simple Backward Pavlovian Conditioning Procedures

Concurrent forward/backward Pavlovian conditioning procedures were compared with simple forward and simple backward procedures for differential excitatory and inhibitory conditioning. Four groups of dogs each received 30 shocks while restrained in a Pavlovian harness. One group of dogs (CON) received concurrent conditioning with a clicker signaling shocks and with a tone following shocks. For another group of dogs (SF), a clicker signaled the shocks, whereas the tone was randomly related to shocks. For a third group (SB), the tone followed shock termination, whereas the clicker was randomly related to shocks. For a fourth group (TRC), both the clicker and the tone were randomly related to shocks. All stimuli were then superimposed on a temporally paced avoidance baseline and their associative properties were assessed relative to the TRC group. Differential excitatory-inhibitory conditioning was significantly reduced in the concurrent procedure relative to that which occurred in the simple conditioning procedures despite exactly equal CS + -US and US-CS-contingencies. These results were interpreted with reference to contextual conditioning effects predicted by the Rescorla-Wagner conditioning model and the theoretical issue of independence vs. interdependence of CS-US associative strengths.

Ranking of liver tests for differential diagnosis of liver parenchymal diseases.

Liver function tests were ranked in the order useful to differentiate 8 liver parenchymal diseases in combination of tests by forward selection and backward elimination procedures in the likelihood method using a microcomputer. The orders were almost same in both procedures: indocyanine green plasma disappearance rate, glutamic pyruvic transaminase (GPT), zinc turbidity test, alkaline phosphatase, age, HBsAg, RA test, glutamic oxaloacetic transaminase (GOT)/GPT ratio, GOT, cholesterol, total protein, total bilirubin, albumin/globulin ratio and gamma-globulin. The first 9 tests had almost all informations of all tests. The first likelihood diagnosis using the 9 tests was correct in 53% and the first or the second diagnosis was correct in 71% of 444 cases of 8 liver parenchymal diseases. A score table of likelihood diagnosis using the 9 tests was presented for manual application to new cases.

Diagnostic accuracy of the conventional 12-lead and the orthogonal frank-lead electrocardiograms in detection of myocardial infarctions with classifiers using continuous and bernoulli features

The performance of ECG classifiers using Bernoulli variables was evaluated in comparison with the same classifiers using an identical set of ECG features measured in continuum. A Bernoulli variable is permitted to take only two states depending on whether its value is below or above a given threshold. A new method was used for discretization threshold optimization. The branch-and-bound algorithm, the sequential forward selection and backward rejection procedures were used for selecting the best subsets of Bernoulli and continuous features out of the primary set of features measured from the conventional 12-lead and the orthogonal Frank-lead ECG. A linear discriminant function was used to estimate the classification accuracy of Bernoulli and continuous features in a test library composed of ECGs of 237 Subjects with old myocardial infarcts and 299 subjects without infarction. The results indicate that while Bernoulli variables perform as well as or better than continuous variables over a wide range of sensitivity and specificity, continuous features appear to yield a higher diagnostic accuracy when a high level of specificity is required. In comparison with the diagnostic accuracy of the Minnesota Code's criteria for myocardial infarction, decision-theoretic classifiers using continuous features yielded an overall improvement in sensitivity from 14 to 20% at a fixed level of specificity. The information content of the conventional 12-lead ECG appeared as good as or better than that of the orthogonal Frank-lead ECG regarding differential diagnosis between myocardial infarction and non-infarction groups when identical statistical procedures were used for the design of the classifiers.

A rapid enzymatic DNA sequencing technique: determination of sequence alterations in early simian virus 40 temperature sensitive and deletion mutants.

We have adapted a rapid sequencing technique from the enzymatic nick-translation method of Maat and Smith. The Forward-Backward procedure employs both synthetic and 3' to 5' exonucleolytic activities of E. coli DNA polymerase I to achieve greater reliability, especially in reading stretches of the same nucleotide. The technique has been employed to determine sequence alterations in four early SV40 temperature-sensitive (tsA) point mutants and five early SV40 viable deletion mutants. The nucleotide sequence of these mutants provides an insight into their biological properties.