Galactic cosmic ray transport methods: past, present, and future

The development of the theory of high charge and energy (HZE) ion transport is reviewed. The basic solution behavior and approximation techniques will be described. An overview of the HZE transport codes currently available at the Langley Research Center will be given. The near term goal of the Langley program is to produce a complete set of one-dimensional transport codes. The ultimate goal is to produce a set of complete three-dimensional codes which have been validated in the laboratory and can be applied in the engineering design environment. Recent progress toward completing these goals is discussed.

Radiosensitivity parameters for lethal mutagenesis in Caenorhabditis elegans

For the first time track structure theory has been applied to radiobiological effects in a living organism. Data for lethal mutagenesis in Caenorhabditis elegans, obtained after irradiation with nine different types of ions of atomic number 1-57 and gamma rays have yielded radiosensitivity parameters (E0, sigma 0, kappa, m = 68 Gy, 2.5 x 10(-9) cm2, 750, 2) comparable with those found for the transformation of C3HT10 1/2 cells (180 Gy, 1.15 x 10(-10) cm2, 750, 2) but remote from those (E0 and sigma 0 = approximately 2 Gy, approximately 5 x 10(-7) cm2) for mammalian cell survival.

Quantum dynamics as a stochastic process

The quantum Liouville equation is solved in the Wigner representation using generalized Monte Carlo techniques. For small increments of time, the solution is represented as a sequential classical evolution in phase space followed by a quantum "jump" distribution in momentum space, with the latter simulated via a stochastic method. Extending the work initiated by John and Remler [Ann Phys. (N.Y.) 180, 152 (1987)] the technique is developed and validated for higher dimensions. Also, an alternative algorithm is developed and applied to study motion of a quantum system in an anharmonic quartic potential well, with significantly improved results.

Estimates of HZE particle contributions to SPE radiation exposures on interplanetary missions

Estimates of radiation doses resulting from possible HZE (high energy heavy ion) components of solar particle events (SPEs) are presented for crews of manned interplanetary missions. The calculations assume a model spectrum obtained by folding measured solar flare HZE particle abundances with the measured energy spectra of SPE alpha particles. These hypothetical spectra are then transported through aluminum spacecraft shielding. The results, presented as estimates of absorbed dose and dose equivalent, indicate that HZE components by themselves are not a major concern for crew protection but should be included in any overall risk assessment. The predictions are found to be sensitive to the assumed spectral hardness parameters.

Galactic cosmic ray radiation levels in spacecraft on interplanetary missions

Using the Langley Research Center galactic cosmic ray (GCR) transport computer code (HZETRN) and the computerized anatomical man (CAM) model, crew radiation levels inside manned spacecraft on interplanetary missions are estimated. These radiation-level estimates include particle fluxes, LET (linear energy transfer) spectra, absorbed dose, and dose equivalent within various organs of interest in GCR protection studies. Changes in these radiation levels resulting from the use of various different types of shield materials are presented.

NUCFRG2: a semiempirical nuclear fragmentation model

The semiempirical abrasion/ablation model has been successful in generating a large nuclear data base for use in the study of high charge and energy (HZE) ion beams, radiation physics and galactic cosmic ray shielding. The cross sections generated agree with the measured HZE fragmentation data to the degree that different experimental groups agree among themselves. Several improvements in the model have been made including a Coulomb trajectory correction, an improved treatment of nuclear attenuation factors, an improved second order correction to the spectator fragment excitation spectrum, a pre-equilibrium emission process, and competitive equilibrium emission of additional hydrogen and helium isotope fragments.

HZE beam transport in multilayered materials

A nonperturbative analytic solution of the high charge and energy (HZE) Green's function is used to implement a computer code for laboratory ion beam transport in multiple-layered materials. The code is established to operate on the Langley nuclear fragmentation model used in space engineering applications. Computational procedures are established to generate linear energy transfer (LET) distributions for a specified ion beam and target for comparison with experimental measurement. Comparison with 56Fe ion with Pb-Al and Pb-(CH2)x targets shows reasonable agreement.

Solar modulation and nuclear fragmentation effects in galactic cosmic ray transport through shielding

Crews of manned interplanetary missions may accumulate significant radiation exposures from the galactic cosmic ray (GCR) environment in space. Estimates of how these dose levels are affected by the assumed temporal and spatial variations in the composition of the GCR environment, and by the effects of the spacecraft and body self-shielding on the transported radiation fields are presented. In this work, the physical processes through which shielding alters the transported radiation fields are described. We then present estimates of the effects on model calculations of (1) nuclear fragmentation model uncertainties, (2) solar modulation, (3) variations between solar cycles, and (4) proposed changes to the quality factors which relate dose equivalent to absorbed dose.

Effect of rhinovirus 39 infection on cellular immune parameters in allergic and nonallergic subjects

Patients with allergic rhinitis (AR), compared with nonallergic persons, have been reported to respond differently to a variety of stimuli, some of which are immunologic in nature. This study compared the systemic cellular immune responses to experimental rhinovirus (RV) 39 challenge in RV-39-seronegative AR (n = 20) and nonallergic (n = 18) subjects. Peripheral blood was obtained before, 4 or 7 days after, and 23 days after RV-39 intranasal challenge and assayed for the number and function of various white blood cells. All subjects were infected, as manifested by viral shedding in nasal secretions or seroconversion. RV-39 induced marked changes from baseline values in both immune cell number and functions. Compared with nonallergic subjects, AR subjects manifested different responses for the following parameters: (1) numbers of total white blood cells and lymphocytes (smaller increases on day 4), (2) helper/suppressor T cell ratio (absence of an increase on day 7 and presence of an increase on day 23), (3) number of IL-2 receptor-positive suppressor T cells (presence of a decrease on day 7), (4) natural killer (NK) cell numbers (absence of an increase on day 4 and presence of increases on days 7 and 23), (5) NK/T cell ratio (absence of an increase on day 4 and a decrease on day 7), (6) NK cell activity (a blunted decrease on day 7 and absence of a decrease on day 23), and (7) RV-39-induced lymphocyte proliferation (exaggerated increase on day 4). The results show that intranasal challenge with RV-39 induced RV-39-specific and nonspecific systemic cellular immune responses and a unique immunologic response pattern in AR subjects.

The fragmentation of 670A MeV neon-20 as a function of depth in water. III. Analytical multigeneration transport theory

This is the final report of a detailed study of the interaction of 670A MeV neon ions with water, used as a presumed tissue-equivalent target. A first comparison of the data with theoretical fluence spectra predicted by the one-generation heavy-ion transport code HZESEC was reported previously. In the present article, subsequent nuclear interactions of the fragment are taken into account, using the LBLBEAM multigeneration heavy-ion transport code, which incorporated new features and modifications intended to address some of the approximations made in the previous calculation. The LBLBEAM code uses the method of characteristics and an iterative procedure to solve a one-dimensional Boltzmann transport equation for the first through third successive generations of nuclear reaction products; it includes a recent version of the semiempirical model used to derive nuclear interaction cross sections. The stopping power used for the theory was calculated in the same way that experimental time-of-flight and energy-loss data are converted to obtain a comparison independent of stopping power; accordingly, good agreement was found between calculated and measured neon fluence spectra in the Bragg peak region. Multiple scattering effects were considered separately for each isotope in the present work. Acceptance factors were calculated as previously, assuming that all projectile fragments originate from the first nuclear interaction. The results show that lower-mass isotopes can account for the high-LET portions of the spectrum in measured fluence spectra. Third-generation products become increasingly important as a source of lighter fragments for depths comparable with the primary particle mean free path, accounting for between one-third and one-half of carbon and lighter particles near the Bragg peak; higher-order interactions were negligible for the detector geometry and material thicknesses examined. Agreement between measured and calculated fluence spectra is 30% (20% for integral fluences). Inclusion of hydrogen, helium, and lithium fragments improves agreement between calculated and measured RBE values for spermatogonial cell survival, but tertiary particle acceptance and track structure effects need to be understood in greater detail to predict RBE accurately.

The lack of distensibility of asthmatic airways

Asthma is characterized by chronic endobronchial inflammation and the deposition of collagen below the epithelial basement membrane. The functional significance of collagen deposition is unknown, but it can lead to loss of airway distensibility and hence to eventual loss of bronchodilator response. In this study we examined the volume of airway dead space by a single-breath, nitrogen-plateau method at a range of lung volumes during inspiration. Participants were 10 asthmatics and 10 control subjects who were matched for lung volumes and age. The asthmatics increased their dead space by 27.0 ml/L compared with 37.3 ml/L in the control subjects (p = 0.014). The dead-space volumes at 50% TLC were no different (29.3 ml/L lung volume in asthma versus 26.9 ml/L in control subjects, p = 0.25). Loss of airway distensibility did not correlate, however, with loss of bronchodilator responsiveness, implying that factors other than mechanical airway distensibility may act to determine pharmacologic reversibility of airflow obstruction.

Apoptotic death in epithelial cells: cleavage of DNA to 300 and/or 50 kb fragments prior to or in the absence of internucleosomal fragmentation

To date, apoptosis has been characterized biochemically by the production of 180-200 bp internucleosomal DNA fragments resulting from the activation of an endonuclease(s). The principal morphological feature of apoptosis is the condensation of chromatin and it has been assumed that this may reflect the oligonucleosomal fragmentation pattern. We have re-examined this dogma by comparing the biochemical and morphological features of cell death in several epithelial cell types (HT-29-I1 colon adenocarcinoma, CC164 mink lung, DU-145 human prostatic carcinoma and MCF-7 human breast adenocarcinoma) and one mesenchymal cell line (H11ras-R3 ras-transformed rat fibroblasts). Cell death was induced either by serum deprivation, TGF-beta 1 or etoposide, or by leaving cells to reach confluence. Cell death was assessed with respect to detachment from monolayers, morphological changes and DNA integrity. The DNA-binding fluorophore Hoechst 33258 revealed chromatin condensation patterns consistent with apoptotic cell death in all cell types except MCF-7 cells. Using field inversion gel electrophoresis in conjunction with conventional 2% agarose gel electrophoresis, cleavage of DNA to 50 kbp fragments was observed in all cases except MCF-7 cells. This preceded the appearance of oligonucleosomal fragments in HT-29-I1, CC164 and H11ras-R3 cells. Although the DNA of DU-145 cells fragmented into 50 kbp units, and although the cells exhibited classical apoptotic morphology, no subsequent internucleosomal cleavage was observed. These results suggest that changes in the integrity of DNA indicative of the release of chromatin loop domains occur before cleavage at internucleosomal sites is initiated and that the latter is not an essential step in the apoptotic process.

Surgical correction of medial luxation of the patella in a Miniature Horse

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Geometric model for nuclear absorption from microscopic theory

A parameter-free geometric model for nuclear absorption is derived from microscopic theory. The expression for the absorption cross section in the eikonal approximation taken in integral form is separated into a geometric contribution, described by an energy-dependent effective radius, and two surface terms which are shown to cancel in an asymptotic series expansion. For collisions of light nuclei, an expression for the effective radius is derived using harmonic-oscillator nuclear density functions. A direct extension to heavy nuclei with Woods-Saxon densities is made by identifying the equivalent half density radius for the harmonic-oscillator functions. Coulomb corrections are incorporated and a simplified geometric form of the Bradt-Peters type obtained. Results spanning the energy range of 1 MeV/nucleon to 1 GeV/nucleon are presented. Good agreement with experimental results are obtained.

Paracetamol toxicity and its prevention by cytoprotection with iloprost

In a well-established two phase model of paracetamol toxicity in hamster hepatocytes cell death was accompanied, but not preceded, by a rise in cytosolic free calcium [Ca2+]i. Cell death appears to involve reversible oxidative damage, possibly to the cytoskeleton or mitochondria. In this model low concentrations (10(-8) to 10(-14) M) of iloprost, a stable analogue of prostacyclin, offered protection against the toxic effects of paracetamol. In preliminary studies with a rat liver epithelial cell line transduced with murine P4501A2 the toxicity of paracetamol was attenuated by iloprost. Inhibition of protein synthesis with cycloheximide had no effect on paracetamol toxicity but abolished the cytoprotective effect of iloprost.

Multiple-scattering effects in quasielastic alpha-4He scattering

A multiple-scattering series for describing the quasielastic peak in nucleus-nucleus collisions is derived using the high-energy optical model. The effects of multiple knockout of target nucleons and internal excitation of the projectile are studied and found to be important for large energy loss and momentum transfers in inclusive alpha-4He scattering at 7 GeV/c. An approximate evaluation of higher-order inelastic collision terms is considered for forward-peaked wave functions and is demonstrated to be accurate.

Paracetamol toxicity in hamster isolated hepatocytes: the increase in cytosolic calcium accompanies, rather than precedes, loss of viability

Paracetamol is cytotoxic to hamster isolated hepatocytes by a mechanism that does not involve an early increase in [Ca2+]i. Although an increase in [Ca2+]i does occur, it accompanies rather than precedes, loss of viability. Studies with the ionophore, 4-bromo-A23187, suggest that although sustained elevations of [Ca2+]i per se can initiate cell death, this occurs at levels of [Ca2+]i only above 500 nM. This concentration was not achieved on exposure of cells to a cytotoxic concentration of paracetamol for 30 min. The [Ca2+]i-response of hepatocytes to vasopressin stimulation was not altered by exposing the cells to toxic concentrations of paracetamol. This demonstrates that paracetamol does not cause any impairment in the mobilisation or redistribution of Ca2+. The role of elevated levels of [Ca2+]i in mediating chemically-induced cell-killing requires re-evaluation.

Stockless inventory systems for the health care provider: three successful applications

Three large hospital-based stockless inventory systems are described. First, the method of stockless inventory is described in some detail and differentiated from the just-in-time (JIT) method of inventory management. Second, three hospital case studies involving successful stockless systems are summarized and evaluated. Finally, some important implications for the implementation of stockless inventory systems are summarized for hospital management.

Production of 3H at large momentum in alpha-12C collisions at 2A GeV

Calculations of the longitudinal and transverse momentum distributions for 3H production at large momentum in alpha-12C collisions near 2 A GeV are compared to experiment. Triton exchange and final-state interactions are shown to represent large corrections to the impulse approximation for proton knockout. A method for calculating interference effects for inelastic fragmentation is discussed. Good agreement with experiment is found using a phenomenological overlap function for 3H-p successful in describing 3H production in pion-induced reactions. Comparisons to momentum distributions obtained through (p, 2p) and (e, ep) reactions on 4He are made.

Bronchial mucosal manifestations of atopy: a comparison of markers of inflammation between atopic asthmatics, atopic nonasthmatics and healthy controls

We studied the role of atopy, as defined by positive skin tests to common inhalant allergens, in allergic bronchial inflammation. Endobronchial biopsies were taken via the fibreoptic bronchoscope in 13 symptomatic atopic asthmatics, 10 atopic nonasthmatics, and 7 normals. The numbers of mast cells, identified in the submucosa by immunohistochemistry using the AA1 monoclonal antibody against tryptase, were no different between the three groups, but electron microscopy showed that mast cell degranulation, although less marked in atopic nonasthmatics, was a feature of atopy in general. The numbers of eosinophils, identified by immunohistochemical staining using the monoclonal anti-eosinophil cationic protein antibody, EG2, were greatest in the asthmatics, low or absent in the normals and intermediate in the atopic nonasthmatics. In both atopic groups eosinophils showed ultrastructural features of degranulation. Measurements of subepithelial basement membrane thickness on electron micrographs showed that the collagen layer was thickest in the asthmatics, intermediate in the atopic nonasthmatics and thinnest in the normals. The results suggest that airways eosinophilia and degranulation of eosinophils and mast cells, as well as increased subepithelial collagen deposition, are a feature of atopy in general and suggest that the degree of change may determine the clinical expression of this immune disorder.

Bronchial mucosal manifestations of atopy: a comparison of markers of inflammation between atopic asthmatics, atopic nonasthmatics and healthy controls

We studied the role of atopy, as defined by positive skin tests to common inhalant allergens, in allergic bronchial inflammation. Endobronchial biopsies were taken via the fibreoptic bronchoscope in 13 symptomatic atopic asthmatics, 10 atopic nonasthmatics, and 7 normals. The numbers of mast cells, identified in the submucosa by immunohistochemistry using the AA1 monoclonal antibody against tryptase, were no different between the three groups, but electron microscopy showed that mast cell degranulation, although less marked in atopic nonasthmatics, was a feature of atopy in general. The numbers of eosinophils, identified by immunohistochemical staining using the monoclonal anti-eosinophil cationic protein antibody, EG2, were greatest in the asthmatics, low or absent in the normals and intermediate in the atopic nonasthmatics. In both atopic groups eosinophils showed ultrastructural features of degranulation. Measurements of subepithelial basement membrane thickness on electron micrographs showed that the collagen layer was thickest in the asthmatics, intermediate in the atopic nonasthmatics and thinnest in the normals. The results suggest that airways eosinophilia and degranulation of eosinophils and mast cells, as well as increased subepithelial collagen deposition, are a feature of atopy in general and suggest that the degree of change may determine the clinical expression of this immune disorder.

Dose-response of bacillus Calmette-Guerin in the treatment of superficial bladder cancer

Although bacillus Calmette-Guerin (BCG) has been recognized as an effective therapy for superficial bladder cancer, dose-response studies are not available. Such studies are important because the administration of the vaccine is not devoid of significant side effects when the standard dose of 120 mg. is used. It has been speculated that smaller doses may be equally effective but carry fewer side effects. A controlled study comparing 2 doses of BCG was conducted as an initial step to explore this possibility. A total of 97 patients with a diagnosis of superficial (stages TIS, Ta and T1) bladder cancer was assigned to receive either 60 or 120 mg. BCG intravesically weekly for 6 weeks. The higher dose resulted in a better response for stages TIS, Ta (for prophylaxis of recurrence) and T1. However, the differences were not statistically significant. When stage TIS and Ta tumors coexisted, a significantly better response was recorded for the high dose. The overall success for the 2 treatments was 67% and 37% for the high and low doses, respectively. These differences reached statistical significance (p less than 0.02). Side effects were significantly less in number and severity in patients receiving the smaller dose of the vaccine.

Inclusive inelastic scattering of heavy ions in the independent particle model

We consider the inclusive inelastic scattering of heavy ions using the Glauber model and the independent particle approximation. Inclusive inelastic distributions for projectile excitation of the target and total inelastic scattering, where all projectile and target excited states are summed, are discussed using closure. The total inelastic distribution when integrated is shown to be equivalent to the absorption cross section found from applying the optical theorem to the elastic scattering amplitude in the coherent approximation. Calculations are presented for several heavy-ion pairs using realistic nuclear densities in a large mass number approximation.

Risk analyses for the solar particle events of August through December 1989

The solar particle events of August through December 1989, among the largest ever recorded, are analyzed to assess the potential hazards to humans on interplanetary missions from events of these types. Using the coupled neutron-proton space radiation transport computer code, BRYNTRN, risk estimates for the effects of exposures to the skin, ocular lens, and bone marrow are made for nominal thicknesses of the spacecraft aluminum shielding. Risk assessment in terms of absorbed dose is made for each event. Also presented are estimates of organ absorbed dose and dose equivalent for pairs of events which occurred within 30-day periods, and for the cumulative August through December 1989 period.