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Biomedical subjects

R M Warren

Publications and source records attributed to R M Warren.

9 recordsLinked to original sources
PubMed1992

Percutaneous photocoagulation of deep vascular lesions using a fiberoptic laser wand.

A new technique is presented for the treatment of deep vascular lesions. A potassium-titanyl-phosphate (KTP), argon, or Nd:YAG laser is attached to a fiberoptic wand, which is passed percutaneously. The laser is activated and coagulates the lesion without direct injury to the skin. Eleven hemangiomas and two lymphangiomas have been treated using this technique. A reduction in size of the lesions was obtained in all patients. Repeat treatments were done to improve results in six patients. Conventional transcutaneous laser therapy was used as an adjunct in four patients. Average patient follow-up was 29 months. No major complications have been noted in this series. Percutaneous fiberoptic photocoagulation has been found to be a safe, long-lasting technique for the treatment of deep vascular lesions.

Adolescent↗
PubMed1992

Increasing the intelligibility of speech through multiple phonemic restorations.

Outside of the laboratory, listening conditions are often less than ideal, and when attending to sounds from a particular source, portions are often obliterated by extraneous noises. However, listeners possess rather elegant reconstructive mechanisms. Restoration can be complete, so that missing segments are indistinguishable from those actually present and the listener is unaware that the signal is fragmented. This phenomenon, called temporal induction (TI), has been studied extensively with nonverbal signals and to a lesser extent with speech. Earlier studies have demonstrated that TI can produce illusory continuity spanning gaps of a few hundred milliseconds when portions of a signal are replaced by a louder sound capable of masking the signal were it actually present. The present study employed various types of speech signals with periodic gaps and measured the effects upon intelligibility produced by filling these gaps with noises. Enhancement of intelligibility through multiple phonemic restoration occurred when the acoustic requirements for TI were met and when sufficient contextual information was available in the remaining speech fragments. It appears that phonemic restoration is a specialized form of TI that uses linguistic skills for the reconstruction of obliterated speech.

Adult↗
PubMed1990

Tweaking the lexicon: organization of vowel sequences into words.

The ability of listeners to distinguish between different arrangements of the same three vowels was investigated for repeating sequences having item durations ranging from 10 msec (single glottal pulses) up to several seconds/vowel. Discrimination was accomplished with ease by untrained subjects at all item durations. From 30 through 100 msec/vowel, an especially interesting phenomenon was encountered: The sequences of steady-state vowels were organized into words, with different words heard for the different arrangements of items. In a second experiment, repeating sequences of random arrangements of 10 40-msec vowels were employed. When sets of four such sequences were presented to listeners, distinctive words were heard, which permitted each arrangement to be discriminated from the others. In addition, minimal differences (reversing the order of a single contiguous pair of vowels) in the 10-item sequences could be detected via verbal mediation. Hypotheses are offered concerning mechanisms responsible for these results.

Adult↗
PubMed1989

Perception of complex tone pairs mistuned from unison.

Periodic sounds mistuned from unison may interact to produce pitch glides: When a broad-spectrum complex tone having a fundamental frequency of 400 Hz or less and containing several harmonics above the 8th is mixed with itself after a slight change in the waveform repetition frequency (1 Hz or less), listeners hear a rising glissando when corresponding portions of the waveforms approach alignment and a falling glissando as they recede from alignment. Glissandi are unimpaired if harmonics below the 8th are absent, but if, instead, harmonics above the 8th are removed, only amplitude fluctuations are heard (not glissandi). When two broad-spectrum complex tones with independent, randomly derived phase spectra are mistuned slightly from unison and mixed, complex repeated patterns other than glissandi are heard. These observations, along with others involving a variety of periodic sounds mistuned from unison, provide information concerning the nature of frequency domain and time domain mechanisms employed for the perception of iterated acoustic patterns.

Acoustic Stimulation↗
PubMed1977

The physical aspects with respect to water and non-enzymatic browning.

Non-enzymatic browning is one of the major probles that occurs during the processing and storage of dehydrated and semi-moist foods. One type of browning is the Maillard reaction between reducing sugars and proteins or free amines. This leads to a darkening of color, protein insolubility with subsequent possible nutrition loss and a bitter off-flavor. The reaction has been extensively researched since the early 1940's. From a storage standpoint, browning rate increases as water activity (aw) increases up to a maximum where reactant dilution causes a subsequent decrease in rate. Use of liquid humectants in high moisture foods increase phase volume and viscosity, thereby lowering the aw of the rate maximum. These humectants thus act as inhibitors at high aw. Sorbitol also decreases the rate by a viscosity effect. Kinetic studies at normal storage conditions show browning to occur by a zero order reaction although the sugar and amine initial reaction occurs by first order. Studies with Tetrahymena show that the initial Schiff's base and reaction products may be partially biologically available although chemical assays show up to 50% loss of protein value. For dehydrated foods the zero order kinetics can be used to predict shelf life under a variable time-temperature-humidity condition.

Cellulose↗
PubMed1976

Auditory perception and speech evolution.

Human speech perception seems to involve the ability to recognize groupings of speech sounds rather than component phonemes, and to distinguish between permuted orders of items within sequences as holistic entities. Humans can use this Holistic Pattern Recognition (HPR) not only with speech and music, but also with sequences of arbitrarily selected sounds after very little practice. Infrahuman primates, cats, chinchillas, and birds also seem to employ HPR with auditory sequences. Further, there is recent evidence that animals unable to produce speech sounds can nevertheless discriminate between closely related phonemes. Thus, it appears that human speech perception employs prelinguistic abilities shared with other animals to distinguish between phonemic groupings. Of course, use of speech for communication also requires establishment of phonemic groupings as symbols, and sequential arrangement of these symbols, by rule, to convey the desired message. Identification of Components and their Order (ICO) for auditory sequences is limited to humans. ICO involves verbal categorization and storage of the names for successive auditory items as they appear, followed by retrieval or the names in the order stored. Thus, direct identification of the order of sounds within auditory sequences rests upon verbal ability, which provides an explanation for the difficulty that aphasics have in identifying order within nonverbal sequences. Much confusion in the literature on auditory sequence perception seems to have resulted from a failure to differentiate between HPR and ICO.

Animals↗