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At least 883 records · Page 49Linked to original sources
PubMed1982

Statistical discrimination among vocalizations of individual squirrel monkeys (Saimiri sciureus).

Discriminant analysis was used to distinguish statistically between the chuck vocalizations of individual squirrel monkeys. A unique combination of values of six structural parameters characterized the chucks of each of 5 individuals, permitting reliable identification of sources of chuck vocalizations on the basis of chuck structures alone. Certain parameters were found to be nearly invariant within individual monkeys, while others were quite variable within and between individuals. We propose that this technique be used in retrospective classification of vocalizations by source, when observational identification of the sources of all vocalizations in a rapid sequence is not possible.

Animals↗
PubMed1988

Trading relations in the perception of /r/-/l/ by Japanese learners of English.

The role of language-specific factors in phonetically based trading relations was examined by assessing the ability of 20 native Japanese speakers to identify and discriminate stimuli of two synthetic /r/-/l/ series that varied temporal and spectral parameters independently. Results of forced-choice identification and oddity discrimination tasks showed that the nine Japanese subjects who were able to identify /r/ and /l/ reliably demonstrated a trading relation similar to that of Americans. Discrimination results reflected the perceptual equivalence of temporal and spectral parameters. Discrimination by the 11 Japanese subjects who were unable to identify the /r/-/l/ series differed significantly from the skilled Japanese subjects and native English speakers. However, their performance could not be predicted on the basis of acoustic dissimilarity alone. These results provide evidence that the trading relation between temporal and spectral cues for the /r/-/l/ contrast is not solely attributable to general auditory or language-universal phonetic processing constraints, but rather is also a function of phonemic processes that can be modified in the course of learning a second language.

Adolescent↗
PubMed1999

Rectal dosimetric analysis following prostate brachytherapy.

PURPOSE: To retrospectively assess the rectal tolerance dose in transperineal ultrasound-guided prostate brachytherapy using easily measured point doses. METHODS AND MATERIALS: Forty-five consecutive patients who underwent prostate seed implantation from January 1996 to October 1996, using either 125I or 103Pd as monotherapy or as a boost following 45 Gy of external beam radiotherapy (XRT), were evaluated. For monotherapy using 125I, the minimal peripheral dose (mPD) was 160 Gy, utilizing dosimetry parameters which are equivalent to 144 Gy under the American Association of Physicists in Medicine Task Group 43 (AAPM TG43) recommendations. Computed tomography (CT)-based dosimetry was performed within 9 days of the implant, with a urinary catheter in place for identification of the urethra, and a rectal obturator positioned prior to the CT scan for identification of the anterior rectal mucosa. Dosimetric parameters relevant to this study were the average, maximal and minimal anterior rectal mucosal dose, and the surface area and length of the anterior rectal mucosa irradiated to 50%, 75%, 90%, 100%, and 120% of the prescribed dose. Rectal complications were determined by patient reporting during office visits and telephone follow-up. Follow-up ranged from 19 to 28 months (median 23). RESULTS: Among the four cohorts, the average anterior rectal mucosal dose as a percent of the prescribed mPD was 82.5% +/- 14.1% (standard deviation, SD), and the average maximum was 120% +/- 35%. The length of the rectum receiving a given dose was found to be correlated with the rectal surface area receiving that dose (r2 = 0.82 - 0.93 over the dose range 0.5-1.2 mPD). Rectal complications occurred in only four patients, and consisted of mild, self-limited proctitis. Three of the four were in the top quartile of average and maximal rectal dose and length of rectum receiving > or = 100% of mPD, while the fourth was in the bottom quartile of these parameters. In terms of surface area, all four patients were in the upper half of the study group, with > or = 90 mm2 at dose levels > or = 100% of mPD. CONCLUSION: Our results indicate that in an implant program which maintains the anterior rectal mucosa point dose averages to about 85% of the prescribed dose (regardless of the choice of isotope or the treatment approach), the average maximum to 120% of mPD, and the length of the anterior rectal mucosa receiving 100% and 120% of the prescribed dose at approximately 10 mm and 5 mm, respectively, the incidence of mild self-limited proctitis will be in the range of approximately 9%, without incidence of rectal ulceration and/or fistula formation.

Brachytherapy↗
PubMed1999

In vivo dynamics of the pentose phosphate pathway in Saccharomyces cerevisiae.

The in vivo dynamics of the pentose phosphate pathway has been studied with transient experiments in continuous culture of Saccharomyces cerevisiae. Rapid sampling was performed with a special sampling device after disturbing the steady state with a pulse of glucose. The time span of observation was 120 s after the pulse. During this short time period the dynamic effect of protein biosynthesis can be neglected. The metabolites of interest (glucose 6-phosphate, NADP, NADPH, 6-phosphogluconate, and MgATP2-) we determined with enzymatic assays and HPLC. The experimental observations were then used for the identification of kinetic rate equations and parameters under in vivo conditions. In accordance with results from in vitro studies the in vivo diagnosis supports an ordered Bi-Bi mechanism with noncompetitive inhibition by MgATP2- for the enzyme glucose-6-phosphate dehydrogenase. In the case of 6-phosphogluconate dehydrogenase an ordered Bi-Ter mechanism with a competitive inhibition by MgATP2- has been found. Because the MgATP2- concentration decreases abruptly after the pulse of glucose the inhibitory effect vanishes and the flux through the pentose phosphate pathway increases. This regulation phenomenon guarantees the balance of fluxes through glycolysis and pentose phosphate pathway during the dynamic time period.

Adenosine Triphosphate↗
PubMed1988

Maximum likelihood identification of neural point process systems.

Using the theory of random point processes, a method is presented whereby functional relationships between neurons can be detected and modeled. The method is based on a point process characterization involving stochastic intensities and an additive rate function model. Estimates are based on the maximum likelihood (ML) principle and asymptotic properties are examined in the absence of a stationarity assumption. An iterative algorithm that computes the ML estimates is presented. It is based on the expectation/maximization (EM) procedure of Dempster et al. (1977) and makes ML identification accessible to models requiring many parameters. Examples illustrating the use of the method are also presented. These examples are derived from simulations of simple neural systems that cannot be identified using correlation techniques. It is shown that the ML method correctly identifies each of these systems.

Action Potentials↗
PubMed1985

Anatomical basis of intervertebral disc puncture with chemonucleolysis.

Transparietal puncture of the lumbar intervertebral discs is done to achieve enzymatic nucleolysis. This technique requires firm understanding of the morphology and topography of the anatomical structures traversed by the needle as well as those to be avoided. Vertebral disc puncture with chemonucleolysis has been done by the author for four years. The aim of this study was to identify the parameters allowing facilitation of this procedure, thereby leading to a decreased X-ray exposure. To achieve this goal an analytical study of the target structure and its neurovascular, osseous and visceral relations was carried out. The results of this study led to practical conclusions regarding especially the parameters of disc puncture, their preoperative identification and the risks encountered in case of erroneous puncture.

Chymopapain↗
PubMed1985

Anatomical and roentgenological basis for the study of the lumbar spine with the body in the suspended position.

Roentgenological investigation of the lumbar spine was done in the standing and suspended position in 100 healthy adult male volunteers. Spinal and external morphology were studied. The aim of this work was to identify eventual correlations between the modifications of shape and size of the suspended lumbar spine and external morphology. Such correlations were sought to establish a functional approach to anthropometry. The results of this study demonstrated that the suspended position led to lengthening of the spine in 70% of the subjects examined, shortening of the spine in 22% and mainly straightening of the spine in 8%. Extension of the lumbar spine resulting from the suspended position is dependent upon tonic muscle activity and the relations between the observed spinal modifications and external morphology are difficult to establish. Nevertheless, anthropometric profiles and spinal features allow identification of certain influential external morphological parameters. Furthermore, the results of this study confirm those of others devoted to elongation of the lumbar spine under horizontal traction or suspension and lead to practical conclusions.

Adolescent↗
PubMed2004

Rate-responsive pacing using the atrio-ventricular conduction time: design and test of a new algorithm.

The cardio-circulatory system of chronotropic incompetent patients is unable to adapt heart rate adequately to the level of strain. A common therapy is the implantation of a pacemaker that stimulates the heart at a rate derived from a strain related sensor signal. The paper describes a new pacemaker concept that uses a well-defined time interval in the electrogram as a sensor parameter, the atrioventricular conduction time (AVCT). Identification experiments with patients delivered the stationary and dynamic behaviour of AVCT subject to variations in the exercise rate and the pacing frequency. Furthermore, it was demonstrated that AVCT is perturbed by respiratory activity. The new rate-responsive algorithm, which uses the internal model control principle, explicitly takes into account the closed-loop nature of the underlying system. The major design objectives were: extended range of the individual heart rate; effective attenuation of the respiratory-related disturbance; and stability. Seven patients undergoing incremental exercise were paced with this AVCT-based algorithm. The experiments confirmed the suitability of this concept with respect to the design goals. The patients' peak intrinsic heart rate at exercise was 100 +/- 20min(-1). When paced with the AVCT algorithm, the paced heart rate was 126 +/- 12min(-1). The increase was significant (26 +/- 13min(-1); 15 to 53 min(-1)), which clearly demonstrated the potential of this concept to restore chronotropic competence.

Aged↗
PubMed1987

A 6-hour human parathyroid hormone (1-34) infusion protocol: studies in normal and hypoparathyroid subjects.

Parathyroid hormone (PTH)-resistant states are usually diagnosed by the failure of an acute PTH injection to elicit a rise in urinary cAMP and phosphate or, less commonly, by the failure of repeated PTH injections to raise serum calcium. We have established a 6 hour infusion of human PTH (1-34) which identifies PTH-resistant hypoparathyroid subjects on the basis of serum 1,25-dihydroxyvitamin D (1,25(OH)2D) and calcium responses. 1,25-Dihydroxyvitamin D levels increased by at least 58 pmol/liter and serum calcium by at least 0.1 mmol/liter in PTH-responsive hypoparathyroid subjects (n = 6), whereas in pseudohypoparathyroid subjects (n = 5) these levels rose by less than 22 pmol/liter and 0.06 mmol/liter respectively. The responsiveness of urinary phosphate excretion, expressed as the renal threshold phosphate concentration (TmPO4/GFR), to PTH also clearly separated the pseudohypoparathyroid patients from the other subjects. Differences in urinary calcium responses were observed though this parameter was less reliable in the identification of individual PTH-resistant or PTH-sensitive hypoparathyroid patients. Nephrogenous cAMP did not discriminate between groups when this protocol was used. This test has the potential to facilitate and extend the classification of PTH-resistant states.

Adult↗
PubMed2005

Optimization and scale up of industrial fermentation processes.

To increase product yields and to ensure consistent product quality, key issues of industrial fermentations, process optimization and scale up are aimed at maintaining optimum and homogenous reaction conditions minimizing microbial stress exposure and enhancing metabolic accuracy. For each individual product, process and facility, suitable strategies have to be elaborated by a comprehensive and detailed process characterization, identification of the most relevant process parameters influencing product yield and quality and their establishment as scale-up parameters to be kept constant as far as possible. Physical variables, which can only be restrictedly kept constant as single parameters, may be combined with other pertinent parameters to appropriate mathematical groups or dimensionless terms. Process characterization is preferably based on real-time or near real-time data collected by in situ and on-line measurements and may be facilitated by supportive approaches and tools like neural network based chemometric data analysis and modelling, clarification of the mixing and stream conditions through computational fluid dynamics and scale-down simulations. However, as fermentation facilities usually are not strictly designed according to scale-up criteria and the process conditions in the culture vessels thus may differ significantly and since any strategy and model can only insufficiently consider and reflect the highly complex interdependence and mutual interaction of fermentation parameters, successful scale up in most cases is not the result of a conclusive and straight-lined experimental strategy, but rather will be the outcome of a separate process development and optimization on each scale. This article gives an overview on the problems typically coming along with fermentation process optimization and scale up, and presents currently applied scale-up strategies while considering future technologies, with emphasis on Escherichia coli as one of the most commonly fermented organisms.

Bioreactors↗
PubMed2005

Early prostate development and its association with late-life prostate disease.

The development of the prostate is an emerging priority area for prostate biologists. Early changes in prostate development permanently alter prostate morphology and function and an understanding of the permanent nature of early events that may influence the onset of late-life disease is vital. Two of the inherent problems involve associating exposure in early life with outcome in late life or maturity and accounting for the influence of genetic, environmental, dietary or metabolic factors during the intervening period. Any one of these factors, alone or in combination, might lead to an explanation of the discrepancies found in the literature regarding the influence of early changes to the prostate in later life. Therefore, it is important to establish a causal link between the hormonal changes that occur during the fetal/neonatal period and that imprint the gland and the onset of late-life pathology. In order to achieve this goal, several technical challenges need to be overcome to permit the objective assessment of prostate branching morphogenesis. Stereological techniques now allow the quantification of several parameters of branching morphogenesis and the identification of specific early changes that are permanent and irreversible with a late-life outcome. This methodology provides the means to determine the action of a range of genes or hormone/growth factors that have been implicated in prostate development and disease.

Fetus↗
PubMed1992

Four-state models and regulation of contraction of smooth muscle. II. Properties of the solutions and identification.

We analyze the behavior and the identification problem of cyclic four-state models. We find that for any state, or a weighted combination of two states, there can be at most one maximum, or one minimum, and two inflection points. We obtain necessary conditions for overshoot and undershoot and give examples. We describe procedures to estimate all the rate constants and discuss certain experimental aspects of the identification problem. Finally, we give an example of identification by obtaining the 10 model parameters from experimental data on skinned fibers from smooth muscle. These results, in conjunction with the results of the previous paper, can help in testing four-state models of regulation of contraction of smooth muscle and of a variety of other physiological and biochemical phenomena.

Animals↗
PubMedDate not supplied

Humoral immunity factors in cynomolgus macaques (Macaca fascicularis) serum: immunoglobulins and total light chains in nursing dams.

This study was aimed at the identification of variations in humoral immunity parameters during the lactation period in macaque females, a recognized model in reproductive physiology and pathology. The importance of such evaluation is evidenced in particular by the central role played by the maternally transferred immunity to the progeny. The trends of serum immunoglobulins and light chains were characterized by immunonephelometry during the 6-months of lactation. The levels attained by nursing females were evaluated against a control group. The main modifications induced by lactation were in the IgM class, whose levels remained constantly lower than in the control group; the other Igs, even if showing different trends, returned to levels comparable to the control group by the end of the sixth month. Light chains quantification evidenced a significant decrease in Kappa levels; Lambda chains showed a similar trend. The variation of the Kappa/Lambda ratio was therefore minimal.

Analysis of Variance↗
PubMed1988

Learning abilities and disabilities: effective diagnosis and treatment.

An integrated theoretical and methodological framework is presented for the effective diagnosis and treatment of varying degrees of learning abilities and disabilities. This methodology is based upon: (1) the degrees of 'analytical-specific perceptual skills' as measured by the Mangina test; (2) the identification of standardized physiological activation level parameters; (3) a standardized psychophysiological therapeutic treatment procedure (Mangina method) of 'optimal' physiological activation simultaneously combined with 'analytical-specific perceptual stimulation'.

Adolescent↗
PubMed1994

Application of backpropagation neural networks to diagnosis of breast and ovarian cancer.

Neural network programs have been developed in an attempt to improve the diagnosis of breast and ovarian cancer using a group of laboratory tests and the age of the patient. The laboratory tests employed in this study include albumin, cholesterol, HDL-cholesterol, triglyceride, apolipoproteins A1 and B, NMR linewidth (the Fossel Index) and a tumor marker (i.e., CA 15-3 or CA 125). The breast cancer study involved 104 patients (45 malignant and 59 benign subjects). The ovarian cancer study involved 98 individuals (35 malignant, 36 benign and 27 control subjects). Methods are outlined for identification of the most influential input parameters and optimization of network structure and training. Network characteristics were contrasted with the test results of the appropriate serum tumor marker assay. For the breast cancer study, the best neural network program, using six input parameters, had a sensitivity of only 55.6% and a specificity of 72.9%. The tumor marker CA 15-3 alone gave results of 61.3% and 64.4%, respectively. For the ovarian cancer study, the best neural network program, using six input parameters, had a sensitivity of 80.6% and a specificity of 85.5%. The tumor marker CA 125 alone gave results of 77.8% and 82.3%, respectively. These methods provide an objective approach to neural network optimization and parameter selection applicable to other data bases of clinical and laboratory data.

Biomarkers, Tumor↗
PubMed1990

Architecture of selected wrist flexor and extensor muscles.

The architectural features of 25 wrist flexor and extensor muscles were studied. Muscles included the flexor carpi ulnaris, the flexor carpi radialis, the extensor carpi ulnaris, the extensor capri radialis brevis, and the extensor carpi radialis longus. Muscle length, mass, fiber pennation angle, fiber length, and sarcomere length (by use of laser diffraction techniques) were determined. In addition, physiological cross-sectional area and fiber length/muscle length ratio were calculated. The muscles were found to be highly specialized, with architectural features of same muscles very similar. The fiber length/muscle length ratio, muscle length, and pennation angle represented the major differences between muscles. Thus using these parameters in discriminant analysis permitted correct identification of each of the 25 muscles. In terms of size and intrinsic design, these individual muscles were highly specialized for their function.

Forearm↗
PubMed1984

Detection of ectopic pregnancy in an outpatient population: the role of the beta-HCG level.

A retrospective analysis was made of 265 female outpatients who initially presented to an emergency department with a complaint of amenorrhea, vaginal bleeding, or abdominal/pelvic pain. The patients were discharged from the emergency department pending results of a serum pregnancy test. Forty-five of the patients were subsequently found to have an elevated (greater than 5 mIU/mL) beta human chorionic gonadotropin (HCG) level. Six of the patients had an ectopic pregnancy; their beta HCG levels ranged from 19 to 265 mIU/mL. A detectable beta HCG level less than 500 mIU/mL had a 33% probability of an ectopic pregnancy in the study group. Historical features, physical examination, and laboratory parameters were of limited value for identification of minimally symptomatic outpatients at risk for an ectopic pregnancy. No study patient had a systolic blood pressure of less than 86 mm Hg on presentation. A comparison group of 29 patients admitted to the hospital directly from the emergency department with a diagnosis of "rule out ectopic pregnancy" during the same time interval was identified. Nine of the directly admitted patients were found to have ectopic pregnancies. A statistically greater proportion of the directly admitted patients had a hematocrit less than 35% and a positive urine (tube) pregnancy test than that found for the study group. Five of the comparison group patients were noted to have a systolic blood pressure of less than or equal to 80 mm Hg. The beta HCG was found to be an essential tool in the evaluation of potential ectopic pregnancy in patients with minimal symptomatology.

Adult↗
PubMed2005

Mechanics of the taper integrated screwed-in (TIS) abutments used in dental implants.

The tapered implant-abutment interface is becoming more popular due to the mechanical reliability of retention it provides. Consequently, understanding the mechanical properties of the tapered interface with or without a screw at the bottom has been the subject of a considerable amount of studies involving experiments and finite element (FE) analysis. This paper focuses on the tapered implant-abutment interface with a screw integrated at the bottom of the abutment. The tightening and loosening torques are the main factors in determining the reliability and the stability of the attachment. Analytical formulas are developed to predict tightening and loosening torque values by combining the equations related to the tapered interface with screw mechanics equations. This enables the identification of the effects of the parameters such as friction, geometric properties of the screw, the taper angle, and the elastic properties of the materials on the mechanics of the system. In particular, a relation between the tightening torque and the screw pretension is identified. It was shown that the loosening torque is smaller than the tightening torque for typical values of the parameters. Most of the tightening load is carried by the tapered section of the abutment, and in certain combinations of the parameters the pretension in the screw may become zero. The calculations performed to determine the loosening torque as a percentage of tightening torque resulted in the range 85-137%, depending on the values of taper angle and the friction coefficient.

Bone Screws↗