Boltzmann's equation at 150: Traditional and modern solution techniques for charged particles in neutral gases.

Seminal gas discharge experiments of the late 19th and early 20th centuries laid the foundations of modern physics, and the influence of this "golden era" continues to resonate well into the 21st century through modern technologies, medical applications, and fundamental scientific investigations. Key to this continuing success story has been the kinetic equation formulated by Ludwig Boltzmann in 1872, which provides the theoretical foundations necessary for analyzing such highly non-equilibrium situations. However, as discussed here, the full potential of Boltzmann's equation has been realized only in the past 50 years or so, with modern computing power and analytical techniques facilitating accurate solutions for various types of charged particles (ions, electrons, positrons, and muons) in gases. Our example of thermalization of electrons in xenon gas highlights the need for such accurate methods-the traditional Lorentz approximation is shown to be hopelessly inadequate. We then discuss the emerging role of Boltzmann's equation in determining cross sections by inverting measured swarm experiment transport coefficient data using machine learning with artificial neural networks.

Self-consistency of electron-THF cross sections using electron swarm techniques.

The drift velocity and first Townsend ionization coefficient of electrons in gaseous tetrahydrofuran are measured over the range of reduced electric fields 4-1000 Td using a pulsed-Townsend technique. The measured drift velocities and Townsend ionization coefficients are subsequently used, in conjunction with a multi-term Boltzmann equation analysis, as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-THF vapor cross sections. In addition, the sensitivity of the transport coefficients to uncertainties in the existing cross sections is presented. As a result of that analysis, a refinement of the momentum transfer cross section for electron-THF scattering is presented, along with modifications to the neutral dissociation and dissociative electron attachment cross sections. With these changes to the cross section database, we find relatively good self-consistency between the measured and simulated drift velocities and Townsend coefficients.

Electron scattering and transport in liquid argon.

The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann's equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.

Reduced model of plasma evolution in hydrogen discharge capillary plasmas.

A model describing the evolution of the average plasma temperature inside a discharge capillary device including Ohmic heating, heat loss to the capillary wall, and ionization and recombination effects is developed. Key to this approach is an analytic quasistatic description of the radial temperature variation which, under local thermal equilibrium conditions, allows the radial behavior of both the plasma temperature and the electron density to be specified directly from the average temperature evolution. In this way, the standard set of coupled partial differential equations for magnetohydrodynamic (MHD) simulations is replaced by a single ordinary differential equation, with a corresponding gain in simplicity and computational efficiency. The on-axis plasma temperature and electron density calculations are benchmarked against existing one-dimensional MHD simulations for hydrogen plasmas under a range of discharge conditions and initial gas pressures, and good agreement is demonstrated. The success of this simple model indicates that it can serve as a quick and easy tool for evaluating the plasma conditions in discharge capillary devices, particularly for computationally expensive applications such as simulating long-term plasma evolution, performing detailed input parameter scans, or for optimization using machine-learning techniques.

Combining laser interferometry and plasma spectroscopy for spatially resolved high-sensitivity plasma density measurements in discharge capillaries.

Precise characterization and tailoring of the spatial and temporal evolution of plasma density within plasma sources are critical for realizing high-quality accelerated beams in plasma wakefield accelerators. The simultaneous use of two independent diagnostics allowed the temporally and spatially resolved detection of plasma density with unprecedented sensitivity and enabled the characterization of the plasma temperature in discharge capillaries for times later than 0.5 µs after the initiation of the discharge, at which point the plasma is at local thermodynamic equilibrium. A common-path two-color laser interferometer for obtaining the average plasma density with a sensitivity of 2 × 1015 cm-2 was developed together with a plasma emission spectrometer for analyzing spectral line broadening profiles with a resolution of 5 × 1015 cm-3. Both diagnostics show good agreement when applying the spectral line broadening analysis methodology of Gigosos and Cardeñoso in the temperature range of 0.5 eV-5.0 eV. For plasma with densities of 0.5-2.5 × 1017 cm-3, temperatures of 1 eV-7 eV were indirectly measured by combining the diagnostic information. Measured longitudinally resolved plasma density profiles exhibit a clear temporal evolution from an initial flat-top to a Gaussian-like shape in the first microseconds as material is ejected out from the capillary. These measurements pave the way for highly detailed parameter tuning in plasma sources for particle accelerators and beam optics.

Practice variation in the diagnosis of acute rejection among pediatric heart transplant centers: An analysis of the pediatric heart transplant society (PHTS) registry.

BACKGROUND: Freedom from rejection in pediatric heart transplant recipients is highly variable across centers. This study aimed to assess the center variation in methods used to diagnose rejection in the first-year post-transplant and determine the impact of this variation on patient outcomes. METHODS: The PHTS registry was queried for all rejection episodes in the first-year post-transplant (2010-2019). The primary method for rejection diagnosis was determined for each event as surveillance biopsy, echo diagnosis, or clinical. The percentage of first-year rejection events diagnosed by surveillance biopsy was used to approximate the surveillance strategy across centers. Methods of rejection diagnosis were described and patient outcomes were assessed based on surveillance biopsy utilization among centers. RESULTS: A total of 3985 patients from 56 centers were included. Of this group, 873 (22%) developed rejection within the first-year post-transplant. Surveillance biopsy was the most common method of rejection diagnosis (71.7%), but practices were highly variable across centers. The majority (73.6%) of first rejection events occurred within 3-months of transplantation. Diagnosis modality in the first-year was not independently associated with freedom from rejection, freedom from rejection with hemodynamic compromise, or overall graft survival. CONCLUSIONS: Rejection in the first-year after pediatric heart transplant occurs in 22% of patients and most commonly in the first 3 months post-transplant. Significant variation exists across centers in the methods used to diagnose rejection in pediatric heart transplant recipients, however, these variable strategies are not independently associated with freedom from rejection, rejection with hemodynamic compromise, or overall graft survival.

Monte Carlo study of coherent scattering effects of low-energy charged particle transport in Percus-Yevick liquids.

We generalize a simple Monte Carlo (MC) model for dilute gases to consider the transport behavior of positrons and electrons in Percus-Yevick model liquids under highly nonequilibrium conditions, accounting rigorously for coherent scattering processes. The procedure extends an existing technique [Wojcik and Tachiya, Chem. Phys. Lett. 363, 381 (2002)], using the static structure factor to account for the altered anisotropy of coherent scattering in structured material. We identify the effects of the approximation used in the original method, and we develop a modified method that does not require that approximation. We also present an enhanced MC technique that has been designed to improve the accuracy and flexibility of simulations in spatially varying electric fields. All of the results are found to be in excellent agreement with an independent multiterm Boltzmann equation solution, providing benchmarks for future transport models in liquids and structured systems.

Posttransplant diabetes mellitus in pediatric thoracic organ recipients receiving tacrolimus-based immunosuppression.

BACKGROUND: Posttransplantation diabetes mellitus (PTDM) is a well-known complication of tacrolimus-based immunosuppression in both adult and pediatric solid organ recipients. The "natural history" of diabetes in the pediatric thoracic transplant population has not yet been described. METHODS: We identified all pediatric thoracic transplant patients receiving tacrolimus-based immunosuppression who developed PTDM. Medical records were reviewed, with a particular focus on the clinical course of PTDM and its relationship to drug weaning. RESULTS: Diabetes developed in 24 of 143 (17%) 30-day survivors of heart (12/96, 13%) and heart-lung/lung (12/ 47, 26%) transplantation. In 17 (71%) patients, the immunosuppressive regimen at the onset of PTDM also included maintenance corticosteroids. Seventeen patients demonstrated glucose intolerance before the onset of diabetes. Nine patients (38%) developed diabetes during pulsed corticosteroid therapy. Median time of onset after transplantation was 9.0 months. All patients required s.c. insulin for glucose control. The median follow-up from transplant was 49.9 months. There was a significant decrease in mean tacrolimus dosage (P<0.01), tacrolimus level (P<0.04), and steroid dosage (P<0.02) from onset of PTDM to most recent follow-up. Despite this significant reduction in immunosuppression, only 3/24 (13%) patients were successfully weaned off insulin. CONCLUSIONS: Diabetes mellitus is a common complication in pediatric thoracic transplant patients receiving tacrolimus-based immunosuppression. Insulin dependence in our population rarely resolved, even after lowering tacrolimus and steroid doses. Discontinuation of steroids did not guarantee resolution of diabetes.

Experience of FK506 immune suppression in pediatric heart transplantation: a study of long-term adverse effects.

BACKGROUND: Immunosuppression with FK506 for pediatric heart transplantation has been used in this institution since 1989. This study reports the unique toxicity of this macrolide agent in these heart transplant recipients. METHODS: Between October 1989 and August 1994, 49 patients were managed with FK506, which was the initial primary agent in 38 patients. The remaining 11 were switched from cyclosporine A because of persistent rejection or side effects from the cyclosporine A or prednisone. Data were obtained retrospectively from medical records. RESULTS: Mean duration of follow-up was 29 months (median 37 months, range 3 to 96 months). Twenty-nine patients (59%) were receiving FK506 alone; 20 patients (41%) were receiving additional treatment with azathioprine, prednisone, or methotrexate. There were seven deaths. Twenty patients (41%) had elevated creatinine levels between 1 to 2 mg/dl. Five patients (11%) had levels greater than 2 mg/dl. Two patients with preexisting renal dysfunction while receiving cyclosporine A had chronic renal failure 32 and 36 months after switching to FK506 and required kidney transplantation. Hyperkalemia was a persistent finding in 26 patients. Of eight patients with hypertension, four had preexisting disease while receiving cyclosporine A; two had impaired renal function, and two were receiving prednisone. Severe anemia developed in eight patients (16%), two of whom had parvovirus. Moderate anemia developed in 21 patients (43%). Eosinophilia occurred in 19 patients; 11 of 19 patients (58%) had allergic symptoms. There was one case of diabetes mellitus. There were 12 significant infections with four infection-related deaths. Lymphoproliferative disease was noted in three patients, two of whom survived. Gastrointestinal symptoms, including chronic diarrhea, recurrent abdominal pain, and reflux esophagitis were present in 10 patients. CONCLUSIONS: In our experience, anemia, renal toxicity, hyperkalemia, chronic diarrhea, and allergies were the most common adverse effects of FK506. Unlike cyclosporine A, hypertension, gingival hyperplasia, coarsening of facial features, and hirsutism were not seen.

Optimal dosing of intravenous tacrolimus following pediatric heart transplantation.

BACKGROUND: Early experience with intravenous tacrolimus at high doses (0.1-0.15 mg/kg/day) was associated with frequent clinical toxicity. The optimal dosing regimen after pediatric heart transplantation is unknown. METHODS: We retrospectively reviewed data on the last 45 pediatric heart transplant recipients to document the time required to achieve therapeutic blood levels and the safety of 2 differing intravenous dosing regimens (tacrolimus 0.03 & 0.05 mg/kg/day as continuous i.v. infusion). Target plasma levels were (1.2-1.7 ng/ml) with levels >2.0 ng/ ml considered toxic, and target whole blood levels were 15-20 ng/ml with levels >25 ng/ml considered toxic. RESULTS: Mean age at transplantation was 7.5 +/- 5.6 years (0.1-18), and 14 were infants. Intravenous tacrolimus was commenced at a mean of 7 +/- 3 hours (range 2-16) after arrival in the ICU. Eight patients were excluded from analysis because of protocol modifications. Of the remaining 37 pts, 9 received initial infusion at 0.03 mg/kg/day; 3 (33%) achieved 'therapeutic' levels within 48 hours and 1 patient had a toxic level (27 ng/ml) at 36 hours. Twenty-eight patients received 0.05 mg/kg/day; 18 (64%) achieved therapeutic levels within 48 hours and 9 (32%) developed toxic levels. Patients with toxic whole blood levels had higher tacrolimus levels on first blood assay compared to those who did not develop toxicity (16.4 +/- 3.4 vs 9.3 +/- 3.9, p < .0001; level >10 ng/ml on first assay in 7/7 toxic patients vs 7/19 without toxicity, p = .004). Patients receiving the higher dose regimen had fewer episodes of moderate or severe rejection (> or =Grade 3A) at first biopsy than those receiving the lower dose infusion (32% vs 75%; p = .046). No patient required renal dialysis. CONCLUSIONS: Dosing below 0.05 mg/kg/day may result in clinically important delay in achieving therapeutic levels. Toxicity may be reduced by frequent monitoring of levels for the first 48 hours after transplantation especially when the initial level is >10 ng/ml.

New-onset diabetes mellitus in pediatric thoracic organ recipients receiving tacrolimus-based immunosuppression.

BACKGROUND: Tacrolimus has a negative effect on the pancreatic beta islet cell, and both glucose intolerance and diabetes mellitus are well-recognized complications of tacrolimus-based immunosuppression among adult solid organ transplant recipients. METHODS: To determine the association between tacrolimus and new-onset diabetes mellitus in childhood, we reviewed data on 78 pediatric heart and heart-lung/lung recipients receiving tacrolimus-based immunosuppression. Trough tacrolimus levels, fasting and random blood glucose levels, and corticosteroid requirements were reviewed. Diabetes was defined as glucose intolerance requiring long-term insulin treatment more than 30 days after transplantation. RESULTS: No patient had diabetes before introduction of tacrolimus. In heart-lung/lung recipients, 12 of 28 (43%) had development of diabetes at a median follow-up of 7 months (range 1 to 39). In this group diabetes developed in three of eight (38%) patients with cystic fibrosis and nine of 20 (45%) without (p = NS). In contrast, only two of 50 (4%) heart transplant recipients had development of diabetes. Of the 14 patients with diabetes, 10 had development of diabetes during augmentation of immunosuppression with pulsed corticosteroids. Tacrolimus trough levels were significantly lower in heart compared with heart-lung/lung transplant recipients (9.4 +/- 3.3 versus 15.3 +/- 0.9 ng/ml) (p < 0.01), and at latest follow-up significantly fewer heart transplant recipients were treated with maintenance corticosteroids (28% versus 75%; p < 0.01). In the heart-lung/lung group, no significant difference in tacrolimus levels was found between patients with and without diabetes, nor was there a significant difference in the average corticosteroid dose or number of pulses of corticosteroids per patient. CONCLUSIONS: New-onset diabetes mellitus is rare in pediatric heart transplant recipients receiving tacrolimus-based immunosuppression, but it occurs with a high incidence after pediatric heart-lung/lung transplantation and usually develops during pulsed corticosteroid therapy. However, it is currently not possible to predict which heart-lung/ lung transplant recipients will have development of this serious complication.

Affective and evaluative descriptors of pain in the McGill Pain Questionnaire: reduction and reorganization.

Recent reports indicate that several descriptors of pain sensations in the McGill Pain Questionnaire (MPQ) are difficult to classify within MPQ sensory subcategories because of incomprehension, underuse, or ambiguity of usage. Adopting the same methodology of recent studies, the present investigation focused on the affective and evaluative subcategories of the MPQ. A decision rule revealed that only 6 of 18 words met criteria for the affective category and 5 of 11 words met criteria for the evaluative category, thus warranting a reduced list of words in these categories. This reduction, however, led to negligible loss of information transmitted. Despite notable changes in classification, the intensity ratings of the retained words correlated very highly with those originally reported for the MPQ. In conclusion, although the intensity ratings of MPQ affective and evaluative descriptors need no revision, selective reduction and reorganization of these descriptors can enhance the efficiency of this approach to pain assessment.

Aerobic exercise, mood states and menstrual cycle symptoms.

This study examined the effects of regular, moderate exercise on mood states and menstrual cycle symptoms. A group of female regular exercisers (N = 97), and a second group of female nonexercisers (N = 159), completed the Menstrual Distress Questionnaire (MDQ) and the Differential Emotions Scale (DES-IV) premenstrually, menstrually and intermenstrually. Multivariate analyses of covariance (MANCOVAs) revealed significant effects for exercise on negative mood states and physical symptoms, and significant effects on all measures across menstrual cycle phase. The regular exercisers obtained significantly lower scores on impaired concentration, negative affect, behaviour change and pain. No differences were found between groups on positive affect and other physical symptoms.

Method of test administration as a factor in test validity: the use of a personality questionnaire in the prediction of cancer and coronary heart disease.

This study examines the predictive accuracy of four different methods of administration of a questionnaire designed to predict cancer and coronary heart disease (CHD) in healthy probands. The method of administration uses the establishment of trust and the explanation of questions as variables in all four possible combinations, i.e. trust and explanation, trust only, explanation only, and neither, the prediction being that the combination of trust and explanation would produce the most accurate prediction, the treatment using neither the worst prediction, with methods using either trust alone or explanation alone intermediate. The criterion was the successful prediction of cancer and CHD. A total population of 3563 men and women was used, and followed up over 15 years, death certificates being used to establish cause of death. As predicted, the combination of trust and explanation did best, use of neither worst. Explanation seemed more important than trust, and the combination seemed to have a synergistic effect. It is apparent that method of administration had an important effect on the outcome of the experiment.

What does the neuropsychological category test measure?

The Halstead Category Test of brain dysfunction is one of the most sensitive neuropsychological measures currently available. While the instrument has received widespread use, nevertheless, the exact nature of what it measures has been poorly delineated. The present brief report presents the results of separate factor analyses of the Category Test along with other neuropsychological measures from the Halstead-Reitan battery. Despite considerable differences in samples, as well as in the particular neuropsychological measures included in the separate analyses, the Category Test consistently lined-up with general intellectual and memory components, in each instance.

Use of the Booklet Category Test to assess abstract concept formation in schizophrenic disorders.

The relationship of concept formation abilities to the presence or absence of delusions in schizophrenic disorders was investigated. Twenty-six schizophrenic patients and 14 normal individuals were administered a short form of the Booklet Category Test (BCT). Patients were grouped into those with and without delusions. It was hypothesized that the delusional group would perform significantly better on the BCT (obtain lower error scores) than the nondelusional group. Normal and delusional groups obtained significantly lower BCT error scores than the nondelusional group, even when differences in IQ scores were statistically partialled out. The two schizophrenic groups also differed significantly on BCT error scores with the delusional group performing better than the nondelusional group.

Self-report measures of depression: some psychometric considerations.

This paper examines some aspects of the psychometric adequacy of existing self-report depression measures, so that clinicians might better appreciate their reliability and validity. Issues addressed include the desirability of moderate rather than maximum test-retest and item homogeneity/internal consistency estimates; the distinction between measurement at the surface syndrome level vs. that at the fundamental source state/trait level; the importance of appropriate rather than arbitrary factor analytic procedures; and the need for multivariate measures instead of the single-scale instruments so often employed to measure depression in isolation from interacting emotions such as anxiety or stress. Apart from these more general issues, a number of specific criticisms is considered, along with recommendations for better self-report measures of depression.

Effects of menstrual cycle moods and symptoms on academic performance: a study of senior secondary school students.

BACKGROUND: Menstrual cycle moods and symptoms may well play a discernible role in the academic performance of some post-pubescent adolescent female students. AIMS: It was expected that menstrually related moods and symptoms would have both negative and positive influences on academic learning outcomes, and that the magnitude of these effects would be directly proportional to the salience of such moods and symptoms across the monthly cycle. SAMPLES: The sample comprised 427 post-pubescent female students (Years 10, 11, and 12) attending a number of senior secondary schools within the Melbourne metropolitan area, Australia. METHODS: Given the sensitivity of conducting such a study, combined with the logistical difficulties of obtaining prospective data within school settings, retrospective Menstrual Distress Questionnaire (MDQ) scores were related to the previous end-of-year academic grades across a wide range of 18 senior school subjects. Despite the conservative design constraints and associated data analyses (correlations were not corrected for attenuation), some systematic effects were observed. RESULTS: At the premenstrual, menstrual, and intermenstrual phases, moods and symptoms significantly predicted grades in 14 per cent, 7 per cent, and 13 per cent of instances, respectively. Although most significant relationships were negative, scores on the MDQ Arousal scale for the intermenstrual phase positively predicted grades in English Literature, (general) Mathematics, Art and Craft, History, Mathematics 1, and Study of Society. CONCLUSIONS: Evidently, menstrual cycle variables play a small, but discernible role on academic learning outcomes, contributing both positively and negatively to performance. Future, prospective studies are now needed to provide a more definitive account of menstrual cycle influences on academic performance.