Biomedical subjects

R Frost

Publications and source records attributed to R Frost.

At least 19 recordsLinked to original sources

PubMed2000

A prospective randomised multicentre trial comparing 10 Fr Teflon Tannenbaum stents with 10 Fr polyethylene Cotton-Leung stents in patients with malignant common duct strictures.

BACKGROUND: Stent blockage is a multifactorial process in which stent design and materials, bacteria, proteins, and bile viscosity play a role. AIMS: To compare the patency of the 10 Fr Teflon Tannenbaum (TT) stent to that of the 10 Fr Cotton-Leung (CL) polyethylene stent with sideholes, in patients with malignant obstructive jaundice. METHODS: Patients were recruited to this prospective multicentre randomised study if they had a newly diagnosed malignant bile duct stricture below the hilum of the liver suitable for stenting with a 10 Fr stent. Data were collected and monitored by a professional monitoring company. Primary patency was the interval between stent placement and first exchange or death without recurrent jaundice. RESULTS: 134 consecutive patients were recruited between November 1994 and June 1997; 65 were randomised to the TT stent and 69 to the CL stent. Median patency and 95% confidence intervals were 181 (59, 303) days for the TT stent and 133 (92, 174) days for the CL stent, with no significant difference between the two stents (p=0.49). Median survival and 95% confidence intervals were 115 (71, 159) days for the TT stent and 151 (112, 190) days for the CL stent, with no significant difference between the two stents (p=0.765). CONCLUSION: Neither Teflon as a stent material nor the Tannenbaum design prolong the patency of plastic stents.

Adult↗

PubMed1998

Biochemical separations by continuous-bed chromatography.

Innovations in column-packing media for biomolecule purification have progressed from large spherical, porous polysaccharide beads to advanced polymeric supports. Continuous-bed technology is a radical new technology for chromatography based on the polymerization of advanced monomers and ionomers directly in the chromatographic column. The polymer chains form aggregates which coalesce into a dense, homogeneous network of interconnected nodules consisting of microparticles with an average diameter of 3000 A. The voids or channels between the nodules are large enough to permit a high hydrodynamic flow. Due to the high cross-linking of the polymer matrix, the surface of each nodule is nonporous yet the polymeric microparticles provide a very large surface area for high binding capacity. This paper will demonstrate the properties and advantages of using a continuous bed support for high resolution biomolecule separations at high flow-rates without sacrificing capacity.

Animals↗

PubMed1998

Verbs and nouns are organized and accessed differently in the mental lexicon: evidence from Hebrew.

A masked priming paradigm was used to examine the role of the root and verbal-pattern morphemes in lexical access within the verbal system of Hebrew. Previous research within the nominal system had showed facilitatory effects from masked primes that shared the same root as the target word, but not when the primes shared the word pattern (R. Frost, K. I. Forster, & A. Deutsch, 1997). In contrast to these findings, facilitatory effects were obtained for both roots and word patterns in the verbal system. In addition, verbal pattern facilitation was obtained even when the primes were pseudoverbs consisting of illegal combinations of roots and verbal patterns. Significant priming was also found when the primes and the targets contained the same root. The results are discussed with reference to the factors that may determine the lexical status of morphological units in lexical organization. A model of morphological processing of Hebrew words is proposed.

Humans↗

PubMed1998

Toward a strong phonological theory of visual word recognition: true issues and false trails.

A strong phonological theory of reading is proposed and discussed. The first claim of this article is that current debates on word recognition are often based on different axioms regarding the cognitive structures of the mental lexicon rather than conflicting empirical evidence. These axioms lead to different interpretations of the same data. It is argued that once the implicit axioms of competing theories in visual word recognition are explicated, a strong phonological model presents a viable and coherent approach. The assumptions underlying a strong phonological theory of reading are outlined, and 4 theoretical questions are examined: Is phonological recoding a mandatory phase of print processing? Is phonology necessary for lexical access? Is phonology necessary for accessing meaning? How can phonology be derived from orthographic structure? These issues are integrated into a general theory that is constrained by all of the findings.

Cross-Cultural Comparison↗

PubMed1998

Fourier transform infrared spectrometry: a versatile technique for real world samples.

The versatility of FTIR spectrometry was explored by considering a variety of samples drawn from industrial applications, materials science and biomedical research. These samples included polymeric insulators, bauxite ore, clay, human hair and human skin. A range of sampling techniques suitable for these samples is discussed, in particular FTIR microscopy, FTIR emission spectroscopy, attenuated total reflectance and photoacoustic FTIR spectrometry. The power of modern data processing techniques, particularly multivariate analysis, to extract useful information from spectral data is also illustrated.

Hair↗

PubMed1997

What can we learn from the morphology of Hebrew? A masked-priming investigation of morphological representation.

All Hebrew words are composed of 2 interwoven morphemes: a triconsonantal root and a phonological word pattern. the lexical representations of these morphemic units were examined using masked priming. When primes and targets shared an identical word pattern, neither lexical decision nor naming of targets was facilitated. In contrast root primes facilitated both lexical decisions and naming of target words that were derived from these roots. This priming effect proved to be independent of meaning similarity because no priming effects were found when primes and targets were semantically but not morphologically related. These results suggest that Hebrew roots are lexical units whereas word patterns are not. A working model of lexical organization in Hebrew is offered on the basis of these results.

Decision Making↗

PubMed1997

Translation priming with different scripts: masked priming with cognates and noncognates in Hebrew-English bilinguals.

Hebrew-English cognates (translations similar in meaning and form) and noncognates (translations similar in meaning only) were examined in masked translation priming. Enhanced priming for cognates was found with L1 (dominant language) primes, but unlike previous results, it was not found with L2 (nondominant language) primes. Priming was also obtained for noncognates, whereas previous studies showed unstable effects for such stimuli. The authors interpret the results in a dual-lexicon model by suggesting that (a) both orthographic and phonological overlap are needed to establish shared lexical entries for cognates (and hence also symmetric cognate priming), and (b) script differences facilitate rapid access by providing a cue to the lexical processor that directs access to the proper lexicon, thus producing stable noncognate priming. The asymmetrical cognate effect obtained with different scripts may be attributed to an overreliance on phonology in L2 reading.

Adult↗

PubMed1997

The effects of planned duration of residential drug abuse treatment on recovery and HIV risk behavior.

OBJECTIVE: This study assessed the effects of planned duration of residential drug abuse treatment on recovery from drug use and on human immunodeficiency virus (HIV) risk behaviors. METHODS: Two concurrent randomized controlled trials of programs differing in planned duration were conducted: 6-month vs 12-month versions of a traditional therapeutic community program, and 3-month vs 6-month versions of a modified therapeutic community incorporating a relapse prevention and health education program. Outcomes, measured at least 16.5 months after admission, included time from admission to first drug use; severity of drug, alcohol, legal, and employment problems; and risky drug injection and sexual behaviors. RESULTS: Among 539 clients (86% of those enrolled), there were no significant effects of planned duration of treatment upon Addiction Severity Index scores or HIV risk behavior. In the relapse prevention program, clients randomized to the 6-month program had a longer time to first drug use than those in the 3-month program (hazard ratio = 0.74; 95% confidence interval = 0.58, 0.93). Employment problems at follow-up were significantly less severe among clients treated in the therapeutic community than among those in the relapse prevention program. CONCLUSIONS: No overall benefit of extending treatment beyond 6 months was found.

Adult↗

PubMed1997

Planned duration of residential drug abuse treatment: efficacy versus effectiveness.

AIMS: Two randomized controlled trials of residential drug abuse treatment programs found the programs to be equally effective, based on outcomes among those assigned to the treatments. This study aimed to compare the relative efficacy of the programs, based on outcomes among those who received the specific treatment program as planned. DESIGN: Secondary analyses of data from two concurrent randomized controlled trials, with stratification by actual length of stay. SETTING: Two residential drug abuse treatment facilities in the United States. PARTICIPANTS: Six hundred and twenty-eight clients were enrolled over a 2-year period, representing 85% of all clients admitted, 91% of all eligible clients, and 95% of those asked to participate. INTERVENTIONS: At one facility, clients were randomized to 3-month or 6-month versions of a traditional therapeutic community program. At the second facility, clients were randomized to 3-month or 6-month versions of a modified therapeutic community program that emphasized relapse prevention and health education. MEASUREMENTS: Time from admission to first drug use (except alcohol); and Addiction Severity Index (ASI) composite scores for severity of drug, alcohol, legal, and employment problems. FINDINGS: Five hundred and thirty-nine clients (86%) completed a follow-up interview at least 16.5 months after admission. In the relapse prevention trial, benefits of the 6-month program were generally limited to those who stayed at least 40 days. In the therapeutic community trial, among those who stayed at least 171 days, the 12-month program had a beneficial effect on employment. Otherwise, there were inconsistent differences between the 6- and 12-month programs. CONCLUSIONS: On average, clients who stayed in treatment at least 80 days benefited from continuing in treatment for up to 6 months, but not beyond. Conversely, those admitted to programs of longer planned duration who dropped out of treatment early had worse outcomes than those who dropped out of shorter programs. Thus, although longer planned duration of treatment may be efficacious, it is not effective.

Adult↗

PubMed1996

The Yale-Brown Obsessive Compulsive Scale: interview versus self-report.

Several studies have demonstrated the reliability and validity of the Yale-Brown Obsessive Compulsive Scale (YBOCS) conducted by trained interviewers. The present study examined several aspects of a self-report YBOCS version relative to the usual interview format in two non-clinical samples (ns = 46 and 70) and in a clinical OCD sample (n = 36) and a clinical non-OCD group (n = 10). The self-rated instrument showed excellent internal consistency and test-retest reliability, performing somewhat better than the interview. There was good agreement between symptom checklist categories across the two versions, though clinical subjects reported more symptoms on the self-report form than on the interview. Some order effects were evident for non-clinical subjects only: those who received the self-report first scored lower on both self-report and interview than those who received the interview first. No order effects were observed in the clinical sample. The self-report version showed strong convergent validity with the interview, and discriminated well between OCD and non-OCD patients. Although more study is needed, particularly on clinical samples, these findings suggest that the self-report YBOCS may be a time-saving and less costly substitute for the interview format in assessing OCD symptoms.

Adolescent↗

PubMed1996

Changes in HIV risk behavior following alternative residential programs of drug abuse treatment and AIDS education.

We compared the effectiveness in changing human immunodeficiency virus (HIV) risk behavior of two different approaches to acquired immunodeficiency syndrome (AIDS) education given by residential drug abuse treatment programs differing in their planned duration. Two randomized controlled trials compared (a) a 6-month with a 12-month therapeutic community (TC) program, and (b) a 6-month with a 3-month relapse prevention (RP) program. Three composite variables assessing HIV risk (a) drug injection, (b) sexual partners, and (c) condom use-were measured for the 3 months prior to admission and follow-up. The TC program comprised a four-part AIDS information intervention. The RP program comprised a 21- or 42-session small-group program in the principles of RP, 5 skills-building AIDS education sessions, and 6 other health education sessions. Four hundred ninety-five clients were enrolled in the study and completed a follow-up interview within 6 months of exit (79% of those enrolled). Clients in the RP program reduced their drug injection and condom use risk. Female clients in the TC program reduced their condom use risk. There were no differential effects on risk behavior change of either planned duration (randomization assignment) or program type (RP versus TC). Thus, differences in the treatment programs, including AIDS education components, had no apparent effect on HIV risk behavior change. The contribution of residential drug abuse treatment programs to AIDS prevention remains unproved.

Adult↗

PubMed1996

Planned versus actual duration of drug abuse treatment. Reconciling observational and experimental evidence.

The purpose of the study was to evaluate the associations of planned versus actual duration of drug abuse treatment with psychosocial outcomes and drug use at follow-up. A randomized trial was conducted in a modified therapeutic community in which 444 clients were assigned to programs with planned durations of either 3 or 6 months. Outcomes were psychosocial measures assessing changes in mood and in stage of behavior change between admission and exit and return to drug use and patterns of use 2 to 6 months after exit. Planned duration was not associated with any of the outcomes. A longer actual length of stay was, however, associated with greater improvements in the mood variables; lower rates of drug use at follow-up; and, among those using drugs at follow-up, a longer time from exit to first drug use. Intention-to-treat analyses supported these results. Randomized controlled trials are needed to distinguish the effects of planned duration and actual length of stay.

Adult↗

PubMed1996

Is an apple a fruit? Semantic relatedness as reflected by psychophysiological responsivity.

In the present study, we investigated orienting response generalization across various types of semantically related stimuli. Four experiments, based on a modified version of the guilty knowledge technique, were designed to examine whether semantic relations based on abstract features are reflected by electrodermal responsivity. No generalization across coordinates was obtained, but a moderate degree of generalization was demonstrated between a word and its superordinate category (e.g., table-furniture) and between a word and its synonym. Complete generalization occurred from a verbal label of an object to its pictorial representation, and vice versa. These results are compatible with our proposal that partial identification of the test stimulus as relevant is a necessary condition for generalization in the guilty knowledge technique.

Adult↗

PubMed1995

Phonological computation and missing vowels: mapping lexical involvement in reading.

The role of assembled versus addressed phonology in reading was investigated by examining the size of the minimal phonological unit that is recovered in the reading process. Readers named words in unpointed Hebrew that had many or few missing vowels in their printed forms. Naming latencies were monotonically related to the number of missing vowels. Missing vowels had no effects on lexical decision latencies. These results support a strong phonological model of naming and suggest that even in deep orthographies, phonology is not retrieved from the mental lexicon as a holistic lexical unit but is initially computed by applying letter-to-phoneme computation rules. The partial phonological representation is shaped and completed through top-down activation.

Adult↗

PubMed1995

Decomposing words into their constituent morphemes: evidence from English and Hebrew.

Participants segmented and shifted a sequence of letters from a source word to a target word and then named the product aloud. Morphemic and nonmorphemic letter sequences (e.g., EN) from phonemically matched words such as HARDEN and GARDEN were compared. In 4 experiments, naming latencies were faster for morphemic sequences than their nonmorphemic controls in both English, in which the morphemic status of the shifted sequence was varied and sequences were appended after the base morpheme (linearly concatenated), and in Hebrew, in which morphological transparency of the root (base morpheme) was varied and 1 morpheme was infixed inside the other (nonconcatenative) so that the phonological and orthographic integrity of the morphemic constituents was disrupted. Moreover, the likelihood with which both affixes and bases combine to form words influenced segment shifting times. In conclusion, skilled readers are sensitive to the morphological components of words whether or not they form contiguous orthographic or phonological units.

Humans↗

PubMed1995

The effectiveness of alternative planned durations of residential drug abuse treatment.

Randomized controlled trials were conducted at two residential drug abuse treatment facilities to compare programs that differed in planned duration. One trial compared a 6-month and a 12-month therapeutic community program (n = 184), and the second compared a 3-month and a 6-month relapse prevention program (n = 444). Retention rates over comparable time periods differed minimally by planned treatment duration, and the longer programs had lower completion rates. There was no effect in either trial of planned treatment duration on changes in psychosocial variables between admission and exit or on rates or patterns of drug use at follow-up between 2 and 6 months after exit.

Follow-Up Studies↗

PubMed1994

The relationships of HIV status and HIV risky behavior with readiness for treatment.

We investigated the associations of self-reported HIV status and risky injection practices with dependent variables measuring readiness and motivation for treatment and depression among 550 clients at two residential drug abuse treatment programs. The results suggest that a positive HIV status may be associated with motivation for treatment independently of and more strongly than risky behavior. In multivariable analyses, HIV status was associated with a scale measuring cons of drug use (P = 0.006). Risky behavior was associated with the dependent variables only in univariate analyses. The univariate association between risky behavior and depression was confounded by social desirability bias. Further research is needed to determine whether HIV-related variables predict retention or outcome of treatment.

AIDS Serodiagnosis↗

PubMed1994

Prelexical and postlexical strategies in reading: evidence from a deep and a shallow orthography.

The validity of the orthographic depth hypothesis (ODH) was examined in Hebrew by employing pointed (shallow) and unpointed (deep) print. Experiments 1 and 2 revealed larger frequency effects and larger semantic priming effects in naming with unpointed print than with pointed print. In Experiments 3 and 4, subjects were presented with Hebrew consonantal strings that were followed by vowel marks appearing at stimulus onset asynchronies ranging from 0 ms (simultaneous presentation) to 300 ms from the onset of consonant presentation. Subjects were inclined to wait for the vowel marks to appear even though the words could be named unequivocally using lexical phonology. These results suggested that prelexical phonology was the default strategy for readers in shallow orthographies, providing strong support for the ODH.

Adult↗