Dimension from covariance matrices

We describe a method to estimate embedding dimension from a time series. This method includes an estimate of the probability that the dimension estimate is valid. Such validity estimates are not common in algorithms for calculating the properties of dynamical systems. The algorithm described here compares the eigenvalues of covariance matrices created from an embedded signal to the eigenvalues for a covariance matrix of a Gaussian random process with the same dimension and number of points. A statistical test gives the probability that the eigenvalues for the embedded signal did not come from the Gaussian random process.

Grid-based partitioning for comparing attractors

Stationary dynamical systems have invariant measures (or densities) that are characteristic of the particular dynamical system. We develop a method to characterize this density by partitioning the attractor into the smallest regions in phase space that contain information about the structure of the attractor. To accomplish this, we develop a statistic that tells us if we get more information about our data by dividing a set of data points into partitions rather than just lumping all the points together. We use this method to show that not only can we detect small changes in an attractor from a circuit experiment, but we can also distinguish between a large set of numerically generated chaotic attractors designed by Sprott. These comparisons are not limited to chaotic attractors-they should work for signals from any finite-dimensional dynamical system.

Determination of the spin polarization of half-metallic CrO(2) by point contact Andreev reflection

Andreev reflection at a Pb/CrO(2) point contact has been used to determine the spin polarization of single-crystal CrO(2) films made by chemical vapor deposition. The spin polarization is found to be 0.96 +/- 0.01, which confirms that CrO(2) is a half-metallic ferromagnet, as theoretically predicted.

Spin diffusion in semiconductors

The behavior of spin diffusion in doped semiconductors is shown to be qualitatively different than in undoped (intrinsic) ones. Whereas a spin packet in an intrinsic semiconductor must be a multiple-band disturbance, involving inhomogeneous distributions of both electrons and holes, in a doped semiconductor a single-band disturbance is possible. For n-doped nonmagnetic semiconductors the enhancement of diffusion due to a degenerate electron sea in the conduction band is much larger for these single-band spin packets than for charge packets-this explains the anomalously large spin diffusion recently observed in n-doped GaAs at 1.6 K. In n-doped ferromagnetic and semimagnetic semiconductors the motion of spin packets polarized antiparallel to the equilibrium carrier spin polarization is predicted to be an order of magnitude faster than for parallel polarized spin packets. These results are reversed for p-doped semiconductors.

Measuring the spin polarization of a metal with a superconducting point contact

A superconducting point contact is used to determine the spin polarization at the Fermi energy of several metals. Because the process of supercurrent conversion at a superconductor-metal interface (Andreev reflection) is limited by the minority spin population near the Fermi surface, the differential conductance of the point contact can reveal the spin polarization of the metal. This technique has been applied to a variety of metals where the spin polarization ranges from 35 to 90 percent: Ni0.8Fe0.2, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2.

Effect of pulsed electromagnetic stimulation on facial nerve regeneration

OBJECTIVE

To determine if exposure to electromagnetic fields influences regeneration of the transected facial nerve in the rat.

DESIGN AND METHODS

The left facial nerve was transected in the tympanic section of the fallopian canal in 24 rats randomly assigned to 2 groups. The cut ends of the facial nerve were reapproximated without sutures within the fallopian canal to maximize the potential for regeneration. Rats in the experimental group (n= 12) were then exposed to pulsed electromagnetic stimulation (0.4 millitesla at 120 Hz) for 4 hours per day, 5 days per week, for 8 weeks. Rats in the control group (n=12) were handled in an identical manner without pulsed electromagnetic stimulation. Four other rats were given sham operations in which all surgical procedures were carried out except for the actual nerve transection. Two of these rats were placed in each group. Nerve regeneration was evaluated using electroneurography (compound action potentials), force of whisker and eyelid movements, and voluntary facial movements before and at 2-week intervals after transection. Histological evaluation was performed at 10 weeks after transection. Each dependent variable was analyzed using a 2-way analysis of variance with 1 between variable (groups) and 1 within repeated measures variable (days after transection).

RESULTS

Statistical analysis indicated that N1 (the negative deflection of depolarization phase of the muscle and/or nerve fibers) area, N1 amplitude, and N1 duration, as well as absolute amplitude of the compound action potentials, were all significantly greater 2 weeks after transection in the experimental than in the control group of rats. The force of eye and whisker movements after electrical stimulation was statistically greater in the experimental group of rats 4 weeks after transection. Voluntary eye movements in the experimental group were significantly better at 5 and 10 weeks, while whisker movements were better at 3 and 10 weeks. There was no statistical difference between the 2 groups for any histological variable.

CONCLUSION

Results of this study indicate that pulsed electromagnetic stimulation enhances early regeneration of the transected facial nerve in rats.

Changes in brainstem calcitonin gene-related peptide after VIIth and VIIIth cranial nerve lesions in guinea pig

The present study investigated the effect of seventh and eight cranial nerve lesions on the prominence of calcitonin gene-related peptide in the hypoglossal (XII), facial (VII), abducens (VI), and oculomotor (III) cranial nerve nuclei. Guinea pigs were anesthetized and subjected to unilateral cochlear removal, vestibular end organ ablation, and seventh nerve transection. After a survival period ranging from 4 h to 5 days, each animal was anesthetized and perfused intracardially. Frozen sections were collected through the brainstem and stained immunohistochemically for calcitonin gene-related peptide using a polyclonal antibody with the Vectastain ABC kit and protocol. Positive cells were counted in each nucleus bilaterally and analyzed for side to side differences. Nuclei XII and III showed no significant difference in the numbers of cells staining positively for calcitonin gene-related peptide between the ipsilateral and the contralateral sides to the lesion. However, nuclei VII and VI showed elevated numbers ipsilateral to the lesion on some days, but not all. For VII, there was no significant difference before 24 h, but there were significant differences 1-5 days after the lesion. Similarly, in VI, there was no difference before 24 h, but differences were significant beginning with day 1 and continuing through day 3, and finally disappearing by day 4. Changes in the numbers of CGRP positive cells in VII measurable 24 h after the lesion and continuing for at least 5 days afterward indicate a central nervous system retrograde response to peripheral motor nerve injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Paranasal sinus infection due to atypical mycobacteria in two patients with AIDS

Atypical mycobacteria, which are common opportunistic pathogens in patients with AIDS, have not been previously implicated in the pathogenesis of paranasal sinus infections; we describe two such patients. Clinical and radiographic evidence of bilateral maxillary and ethmoid sinusitis was observed for one patient; his infection proved resistant to therapy with conventional antimicrobials and decongestants. Endoscopic ethmoid sinus biopsy yielded a specimen containing acid-fast bacilli (AFB) that were later identified as Mycobacterium kansasii. Antimycobacterial therapy had not resulted in amelioration of the sinusitis > 2 months later, at which time he died of cerebral toxoplasmosis. The second patient presented with a tender right frontotemporal soft-tissue mass; a computed tomogram disclosed that it extended through the frontal bone to the frontal sinus. Inflamed tissue debrided from the sinus contained AFB; cultures first yielded M. kansasii and later Mycobacterium avium complex. Bacteremia due to both organisms was also demonstrated. Infection progressed despite therapy.

Repair of parastomal hernias using polypropylene mesh

Parastomal hernias are a common complication of ostomy construction. We have developed a method of repair that uses two strips of polypropylene prosthetic mesh through a midline incision. The medical records of 19 patients who underwent parastomal hernia repair were retrospectively reviewed. All nine patients operated on for this condition by the senior author (R.G.P.) (group 1) underwent repairs with this technique. All ten patients operated on by other surgeons in our center (group 2) underwent repairs in which the stoma was moved, the fascia was directly repaired through a parastomal incision, or the fascia was repaired via a midline incision. No patients in group 1 had recurrences while five patients in group 2 had recurrences. Neither group developed strictures or stomal prolapse. Our method of repair is technically easy and has excellent results. It is especially suitable in very large hernias in which incisional hernia is likely in the original stoma site if the stoma is moved.

Rudolf Virchow--father of cellular pathology

Rudolf Virchow, the famous German physician-scientist-statesman and social activist of nineteenth century Berlin, contributed greatly to the science of pathology by his teaching, research, and publishing. He consolidated the idea of cellular changes as the basis of disease and introduced many modern concepts and terms into medical science. He led in defining orderly, methodical procedures for the autopsy and emphasized its importance to medicine. Virchow's life and work fundamentally influenced and altered modern medical concepts of disease.

An analysis of toxic deaths, 1982 to 1985, Pima County, Arizona

Toxic deaths in Pima County, Arizona, were studied over a four-year period. The deaths were analyzed according to cause and manner of death, toxic substance, and demographic data. The age group 40 to 49 years had the highest rate of suicide from toxic substances. The accident death rate was highest for ages 20 to 29 years. Carbon monoxide was most often found to be the cause of deaths in this study. The most prevalent drugs were narcotics followed by antidepressants, cocaine, and barbiturates. Comparisons are made with similar studies.

Cocaine-related deaths in Pima County, Arizona, 1982-1984

A three-year review of toxicology data from medical examiner autopsies in Pima County, Arizona, has demonstrated that cocaine has rapidly become a leading substance of abuse, second only to alcohol in the frequency of drugs detected by toxicologic analysis of all suspicious deaths, motor vehicle accident fatalities, homicides, and suicides. Gastric contents and urine were analyzed by thin-layer chromatography, and nasal swabs, blood, and urine were tested for the combination of cocaine and its metabolite benzoylecgonine by quantitative radioimmunoassay. A total of seventy-two deaths in Pima County from 1982 to 1984 have involved cocaine. Seventy percent of these have occurred in the last fifteen months. Marked variation in the individual response to cocaine compared to the blood concentration of cocaine/metabolite was noted.

Lidocaine elimination: effects of metoprolol and of propranolol

The effects of administration of metoprolol and propranolol on lidocaine elimination were studied in six healthy young men who did not smoke. Each received three single intravenous doses of lidocaine (2.5 to 3.0 mg/kg injected over 10 min): one alone, one after 1 day pretreatment with propranolol (40 mg orally every 6 hr), and one after 1 day pretreatment with metoprolol (50 mg orally every 6 hr). Lidocaine clearance was 0.88 +/- 0.28 l X hr-1 X kg-1 before beta blockade, 0.61 +/- 0.20 l X hr-1 X kg-1 during metoprolol dosing, and 0.47 +/- 0.16 l X hr-1 X kg-1 during propranolol dosing. There was no correlation between the change in lidocaine elimination and the steady-state concentrations of metoprolol or propranolol, nor between the change in lidocaine clearance and the change in resting heart rate produced by either beta blocker. Metoprolol and propranolol reduce lidocaine elimination significantly.

A modified ion-selective electrode method for measurement of chloride in sweat

A modified method of analysis of sweat chloride concentration with an ion-selective electrode is presented. The original method of sweat chloride analysis proposed by the Orion Research Corporation (Cambridge, Massachusetts 02139) is inadequate because it produces erratic and misleading results. The modified method was compared with the reference quantitative method of Gibson and Cooke. In the modified method, individual electrode pads are cut and placed in the electrodes rather than using the pads supplied by the company; pilocarpine nitrate (2,000 mg/l) is used in place of pilocarpine HCl (640 mg/l); sodium bicarbonate as the weak electrolyte is used instead of K2SO4. A 10-minute period for sweat accumulation is employed rather than a zero-time collection as in the original Orion method. The modification has been studied for reproducibility in individuals, reproducibility between right and left arm in individuals; it has been compared extensively with the quantitative method of Gibson and Cooke, both in normal individuals and in patients with cystic fibrosis. There is excellent agreement between the modified method and the quantitative reference method. There appears to be a slight bias toward higher concentrations of chloride from the right arm compared with the left arm, but this difference is not medically significant.

Immunochemical determination of human immunoglobulins with a centrifugal analyzer

We used an unmodified centrifugal analyzer (Aminco "Roto-Chem II") to measure human immunoglobulins IgG, IgA, and IgM in diluted sera, with diluted commercial monospecific antisera. Turbidimetric endpoint readings at 340 nm were taken at 4 min for IgG and 12 min for IgA and IgM, although multiple timed-interval readings were printed so that the kinetics of the reaction could be observed. Polyethylene glycol was used to enhance the antigen--antibody reaction. A wide range of concentrations can be measured: for IgG, 0.1--24 g/liter; for IgA and IgM, 50--4000 mg/liter. Correlation with radial immunodiffusion and automated immunoprecipitin techniques was satisfactory. Precision, accuracy, linearity, and sensitivity were quite acceptable. Day-to-day precision ranged from 2.5% to 5.2%, depending on sample concentration. The technique is more precise than radial immunodiffusion, and is rapid, simple, and reliable.

Immunochemical determination of human immunoglobulins with a centrifugal analyzer

We used an unmodified centrifugal analyzer (Aminco "Roto-Chem II") to measure human immunoglobulins IgG, IgA, and IgM in diluted sera, with diluted commercial monospecific antisera. Turbidimetric endpoint readings at 340 nm were taken at 4 min for IgG and 12 min for IgA and IgM, although multiple timed-interval readings were printed so that the kinetics of the reaction could be observed. Polyethylene glycol was used to enhance the antigen--antibody reaction. A wide range of concentrations can be measured: for IgG, 0.1--24 g/liter; for IgA and IgM, 50--4000 mg/liter. Correlation with radial immunodiffusion and automated immunoprecipitin techniques was satisfactory. Precision, accuracy, linearity, and sensitivity were quite acceptable. Day-to-day precision ranged from 2.5% to 5.2%, depending on sample concentration. The technique is more precise than radial immunodiffusion, and is rapid, simple, and reliable.

Acute pulmonary alveolitis in narcotics abuse

Lungs of 17 narcotic abusers from medical-legal autopsies were studied to determine the pathological basis for regional alterations of ventilation and perfusion. Postmortem pulmonary angiographic and histological techniques demonstrated acute alveolar wall inflammation with exudation of fluid and cells into the alveoli in all eight abusers dying of narcotism and in six of nine dying of other causes. All abusers had extensive focal chronic intersititial inflammatory infiltrates. Vascular obstruction due to foreign material occurred only with intravenous use of oral pharmaceuticals, and then only in the microcirculation. Lungs of ten young adults dying suddenly with no history or evidence of narcotics abuse showed no acute alveolitis or intravascular foreign material. Intravenous narcotics injection produces transient acute alveolar inflammation that may account for respiratory manifestations and death. Permanent injury to the lung parenchyma or larger vessels with the usual forms of narcotic abuse is not common.

Pathologic changes in baboon lung allografts. Comparison of two immunosuppression regimes

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