Stable relativistic/charge-displacement channels in ultrahigh power density (approximately 10(21 W/cm3) plasmas

Robust stability is a chief characteristic of relativistic/charge-displacement self-channeling. Theoretical analysis of the dynamics of this stability (i) reveals a leading role for the eigenmodes in the development of stable channels, (ii) suggests a technique using a simple longitudinal gradient in the electron density to extend the zone of stability into the high electron density/high power density regime, (iii) indicates that a situation approaching unconditional stability can be achieved, (iv) demonstrates the efficacy of the stable dynamics in trapping severely perturbed beams in single uniform channels, and (v) predicts that approximately 10(4) critical powers can be trapped in a single stable channel. The scaling of the maximum power density with the propagating wavelength lambda is shown to be proportional to lambda-4 for a given propagating power and a fixed ratio of the electron plasma density to the critical plasma density. An estimate of the maximum power density that can be achieved in these channels with a power of approximately 2 TW at a UV (248 nm) wavelength gives a value of approximately 10(21) W/cm3 with a corresponding atomic specific magnitude of approximately 60 W/atom. The characteristic intensity propagating in the channel under these conditions exceeds 10(21) W/cm2.

Characteristics of patients receiving or foregoing resuscitation at the time of cardiopulmonary arrest

OBJECTIVE

To compare clinical, functional and social characteristics of DNR patients at the time of their cardiopulmonary arrest with characteristics of patients who receive cardiopulmonary resuscitation.

DESIGN

Retrospective chart review of all 261 patients who had a cardiopulmonary arrest during a 6-month period in an academic institution.

SETTING

Teaching Veterans Affairs Medical Center serving a large metropolitan area.

MEASUREMENTS

Demographic characteristics, medical diagnoses, and measures of functional status were collected when DNR orders were initiated and at the time of cardiopulmonary arrest.

RESULTS

The mean age of the studied group was 62 years. Ninety-nine percent were males, and the majority were non-Hispanic white men. One hundred ninety-eight (76%) patients/proxies elected for limiting treatment. Most (85%) elected a DNR order only. Patients were the most frequently documented participants in advance directive decisions in the DNR group. At the time of cardiopulmonary arrest, a higher proportion of the CPR group had coronary artery disease or chronic renal failure, and a higher proportion of the DNR group had cancer or AIDS. The functional status of the DNR group deteriorated from the time of DNR order to death. At the time of cardiopulmonary arrest, the majority of both groups were dependent in all functional domains, and 70% of the DNR group were stuporous or comatose compared with 47% of the CPR group (P = .05). DNR patients were hospitalized for an average of 13.7 +/- 29.5 days after a DNR order was initiated. Six of the 81 patients who received CPR (7.4%) were alive at discharge.

CONCLUSIONS

Patients and physicians deciding to implement a DNR order may be overly focused on medical diagnoses and less so on functional status. A significant proportion of patients with clinical characteristics associated with poor CPR outcome are electing for CPR.

Measurement of 160-fs, 248-nm pulses by two-photon fluorescence in fused-silica crystals

Measurements of 160-fs, 248-nm ultrashort pulses are obtained through a two-photon fluorescence measurement based on the two-photon-induced color-center fluorescence in fused-silica crystals. The method proved to be reliable and advantageous in comparison with two-photon fluorescence techniques employing other materials, both solid state and gaseous.

Congenital toxoplasmosis transmitted from an immunologically competent mother infected before conception

Congenital transmission of Toxoplasma gondii from a mother who was apparently immunologically competent and who had toxoplasmic lymphadenitis 2 months before conception is described. Since no T. gondii-specific serological data were available for this mother from the time her lymph node biopsy specimen was obtained, the specimen was studied by polymerase chain reaction (PCR) to determine whether the T. gondii B1 gene was present. The predictive diagnostic value of histologic findings previously considered to be classic signs of T. gondii lymphadenitis also was studied. This was done by correlation of serological tests diagnostic of acute acquired T. gondii infection and presence of characteristic findings in biopsy specimens from persons without known immunocompromise. Both PCR and review of the characteristic features of her lymph node biopsy specimen confirmed the diagnosis of preconceptual infection in the mother. We also discuss two other cases in which apparently immunologically competent mothers with preconceptually acquired infection transmitted this parasite to their fetuses.

Biomedical three-dimensional holographic microimaging at visible, ultraviolet and X-ray wavelengths

A new imaging technology is under advanced development that has several key advantages over conventional forms of microimaging performed with standard light microscopes, confocal light microscopes, and electron microscopes. The image created by this microscope possesses several unique features: It is intrinsically three-dimensional; it can be formed with very high contrast, a characteristic of the phase-sensitive nature of the recording; the information contained in the image is obtained in a single exposure of the specimen, a feature that eliminates the accumulation of damage to living systems that can occur with techniques utilizing multiple exposures; the method of image construction is fundamentally free from aberration (distortion), thereby obviating the need to employ complex procedures for correction; the exact focal plane of any optical section is digitally determined through computation and is not based on any mechanical adjustments; and the principles of operation, including the computational processes and modalities of image presentation, are uniform over the full range of spectral coverage spanning from the visible (approximately 500 nm) to the X-ray (approximately 0.3 nm) regions. The application of this new technology is expected to open new cost-effective avenues to the understanding, prevention and treatment of broad areas of human disease.

Young children's performance on a task sensitive to the memory functions of the medial temporal lobe in adults--the delayed nonmatching-to-sample task--reveals problems that are due to non-memory-related task demands

Delayed nonmatching-to-sample performance was examined in children and found to be poor from 12 months until almost 2 years even at 5-s delay, although 5 s is well within such children's memory capacity. After 12 months of age, performance did not differ by delay (5 or 30 s). Because children's problems seemed largely unrelated to the task's memory demands, the 2 final studies explored the role of other cognitive abilities (deduction of an abstract rule, speed of processing, and resistance to interference or distraction). Telling children the rule or quadrupling sample presentation time had little effect. Because a salient stimulus (the reward) might interfere with keeping one's attention on the sample, the reward was omitted during initial sample presentation. This helped; at the 5-s delay, 15-month-olds performed at least as well as 21-month-olds in the basic condition, and 12-month-olds performed almost as well. Implications for the cognitive abilities improving during the 2nd year and for the functions of the medial temporal lobe are discussed.

Congenital toxoplasmosis. The Toxoplasmosis Study Group

Congenital toxoplasmosis is a preventable and treatable disease with predominant neurological and ophthalmologic manifestations. These manifestations and approaches to diagnosis, treatment, and prevention of this infection are considered. Outcomes with and without treatment are emphasized. The following also are discussed: recent advances in understanding the organism; its life cycle, epidemiology, pathogenesis, and pathology; and areas in which improvements in diagnosis, treatment, and prevention are needed.

Young children's performance on a task sensitive to the memory functions of the medial temporal lobe in adults--the delayed nonmatching-to-sample task--reveals problems that are due to non-memory-related task demands

Delayed nonmatching-to-sample performance was examined in children and found to be poor from 12 months until almost 2 years even at 5-s delay, although 5 s is well within such children's memory capacity. After 12 months of age, performance did not differ by delay (5 or 30 s). Because children's problems seemed largely unrelated to the task's memory demands, the 2 final studies explored the role of other cognitive abilities (deduction of an abstract rule, speed of processing, and resistance to interference or distraction). Telling children the rule or quadrupling sample presentation time had little effect. Because a salient stimulus (the reward) might interfere with keeping one's attention on the sample, the reward was omitted during initial sample presentation. This helped; at the 5-s delay, 15-month-olds performed at least as well as 21-month-olds in the basic condition, and 12-month-olds performed almost as well. Implications for the cognitive abilities improving during the 2nd year and for the functions of the medial temporal lobe are discussed.

Fourier-transform holographic microscope

We describe a holographic microscope with a spatial resolution approaching the diffraction limit. The instrument uses a tiny drop of glycerol as a lens to create the spherically diverging reference illumination necessary for Fourier-transform holography. Measurement of the point-spread function, which is obtained by imaging a knife edge in dark-field illumination, indicates a transverse resolution of 1.4 microm with wavelength lambda = 514.5 nm. Longitudinal resolution is obtained from the holograms by the numerical equivalent of optical sectioning. We describe the method of reconstruction and demonstrate the microscope's capability with selected biological specimens. The instrument offers two unique capabilities: (1) it can collect three-dimensional information in a single pulse of light, avoiding specimen damage and bleaching; and (2) it can record three-dimensional motion pictures from a series of light pulses. The conceptual design is applicable to a broad range of wavelengths and we discuss extension to the x-ray regime.

Method of concentration of power in materials for x-ray amplification

Recent experimental and theoretical results indicate that a new technique for the controlled concentration of power in materials may be feasible. The power levels that are potentially achievable are sufficient for the generation of amplification of x-ray wavelengths in the kilovolt range. The method of power concentration involves the combination of (1) a new ultrahigh brightness subpicosecond laser technology, (2) multiphoton coupling to atoms and molecules, and (3) a new channeled mode of electromagnetic propagation. The energy scaling of this approach is the most important consideration, and it is shown that the control of the propagation is the key factor that enables high levels of amplification in the kilovolt regime to be achieved with a total excitation energy of ~1 J.

Levels of pyrimethamine in sera and cerebrospinal and ventricular fluids from infants treated for congenital toxoplasmosis. Toxoplasmosis Study Group

Pyrimethamine levels in sera, cerebrospinal fluid (CSF), and ventricular fluid were measured by using reversed-phase high-pressure liquid chromatography. The specimens were from 37 infants receiving pyrimethamine for treatment of suspect or proven congenital toxoplasmosis. Pyrimethamine half-life in serum was 64 +/- 12 h when determined by study of terminal-phase kinetics of samples obtained from nine babies. This half-life was significantly different (P = 0.008) from the pyrimethamine half-life (33 +/- 12 h) determined by terminal-phase kinetics for two babies of the same age taking phenobarbital. Serum pyrimethamine levels at various intervals after dosages of pyrimethamine were also lower for infants receiving phenobarbital. Levels measured in sera from babies taking the same dose of pyrimethamine throughout their first year of life did not appear to vary significantly over time or at different ages (P greater than 0.05). Mean +/- standard deviation serum levels 4 h after a pyrimethamine dose were 1.297 +/- 0.54 micrograms/ml for babies taking 1 mg of pyrimethamine per kg of body weight daily and 0.7 +/- 0.26 microgram/ml for babies taking 1 mg/kg each Monday, Wednesday, and Friday. Levels in CSF were approximately 10 to 25% of concomitant levels in serum. Serum folate levels for infants who took 0.64 to 1.7 mg leukovorin per kg ranged from 33 to 663 ng/ml. To determine whether the levels of pyrimethamine in serum and CSF of treated infants were in a range that affected the most virulent, rapidly replicating, and standard laboratory strain of Toxoplasma gondii, effects of various concentrations of pyrimethamine and sulfadiazine on replication of T. gondii in vitro were assessed. The levels of the antimicrobial agents effective in vitro were in the range of levels of pyrimethamine achieved in sera and CSF. Although folinic acid could inhibit the therapeutic effect of pyrimethamine and sulfadiazine in vitro, inhibition was noted only at levels (> or = 4,800 ng/ml) that were considerably higher than the folate levels found in the treated infants' sera.

Absence of sensorineural hearing loss in treated infants and children with congenital toxoplasmosis

Educationally significant hearing loss has been reported in 10% to 15% of children with congenital toxoplasmosis. As part of a pilot study to assess feasibility and safety of prolonged therapy for congenital toxoplasmosis, 30 congenitally infected infants and children were evaluated for auditory function. Serial testing, beginning within 2 months of birth, was performed. Availability of auditory brainstem response (ABR) testing made evaluation at an earlier age than previously possible. Six (20%) of the 30 infants had mild to moderate conductive type hearing loss associated with otitis media. No infant or child had sensorineural hearing loss. The better outcome we observed compared to previous reports of a 15% to 26% incidence of sensorineural hearing loss and 10% to 15% incidence of educationally significant, bilateral hearing impairment may be related to early initiation and/or prolonged institution of antimicrobial therapy. Continued followup to exclude progressive hearing impairment and study of larger numbers of children are needed to verify these preliminary findings.

Plasma production from ultraviolet-transmitting targets using subpicosecond ultraviolet radiation

Plasma produced from ultraviolet-transmitting solid targets undergoing intense (>10(16) W/cm(2)) subpicosecond (~600 fs) ultraviolet (248 nm) irradiation have been studied under conditions for which no interfering prepulse plasma is generated. Time and spatially integrated measurements of the x-ray emission for H-like and He-like Mg and Si were found to be consistent with LASNEX calculations that model the laser-target interaction.