A pulsed positronium beam using a positron buffer gas trap.

We describe the operation of a pulsed positronium beam based on a two-stage buffer gas positron trap (BGT) or a Surko trap. The BGT allows the areal density and temporal spread of the positron beam to be tailored. This tailored positron beam is used to form a positronium beam via charge exchange with an atomic or molecular gas. The resulting positronium beam is energy tunable, and the collimated beam relies on the angular differential positronium production cross section of the atomic or molecular gas used.

Positron scattering from pyridine.

We present a range of cross section measurements for the low-energy scattering of positrons from pyridine, for incident positron energies of less than 20 eV, as well as the independent atom model with the screening corrected additivity rule including interference effects calculation, of positron scattering from pyridine, with dipole rotational excitations accounted for using the Born approximation. Comparisons are made between the experimental measurements and theoretical calculations. For the positronium formation cross section, we also compare with results from a recent empirical model. In general, quite good agreement is seen between the calculations and measurements although some discrepancies remain which may require further investigation. It is hoped that the present study will stimulate development of ab initio level theoretical methods to be applied to this important scattering system.

Near-Threshold Ionization of Argon by Positron Impact.

The direct single-ionization cross section for Ar by positron impact has been measured in the region above the first ionization threshold. These measurements are compared to semiclassical calculations which give rise to a power law variation of the cross section in the threshold region. The experimental results appear to be in disagreement with extensions to the Wannier theory applied to positron impact ionization, with a smaller exponent than that calculated by most previous works. In fact, in this work, we see no difference in threshold behavior between the positron and electron cases. Possible reasons for this discrepancy are discussed.

Low energy positron interactions with uracil--total scattering, positronium formation, and differential elastic scattering cross sections.

Measurements of the grand total and total positronium formation cross sections for positron scattering from uracil have been performed for energies between 1 and 180 eV, using a trap-based beam apparatus. Angular, quasi-elastic differential cross section measurements at 1, 3, 5, 10, and 20 eV are also presented and discussed. These measurements are compared to existing experimental results and theoretical calculations, including our own calculations using a variant of the independent atom approach.

Positron interactions with water-total elastic, total inelastic, and elastic differential cross section measurements.

Utilising a high-resolution, trap-based positron beam, we have measured both elastic and inelastic scattering of positrons from water vapour. The measurements comprise differential elastic, total elastic, and total inelastic (not including positronium formation) absolute cross sections. The energy range investigated is from 1 eV to 60 eV. Comparison with theory is made with both R-Matrix and distorted wave calculations, and with our own application of the Independent Atom Model for positron interactions.

Total, elastic, and inelastic cross sections for positron and electron collisions with tetrahydrofuran.

We present total, elastic, and inelastic cross sections for positron and electron scattering from tetrahydrofuran (THF) in the energy range between 1 and 5000 eV. Total cross sections (TCS), positronium formation cross sections, the summed inelastic integral cross sections (ICS) for electronic excitations and direct ionization, as well as elastic differential cross sections (DCS) at selected incident energies, have been measured for positron collisions with THF. The positron beam used to carry out these experiments had an energy resolution in the range 40-100 meV (full-width at half-maximum). We also present TCS results for positron and electron scattering from THF computed within the independent atom model using the screening corrected additivity rule approach. In addition, we calculated positron-impact elastic DCS and the sum over all inelastic ICS (except rotations and vibrations). While our integral and differential positron cross sections are the first of their kind, we compare our TCS with previous literature values for this species. We also provide a comparison between positron and electron-impact cross sections, in order to uncover any differences or similarities in the scattering dynamics with these two different projectiles.

Experimental and theoretical cross sections for positron collisions with 3-hydroxy-tetrahydrofuran.

Cross section results from a joint experimental and theoretical investigation into positron scattering from 3-hydroxy-tetrahydrofuran (3H-THF) are presented. Total and positronium (Ps) formation cross sections have been measured from 1 to 190 eV using the positron beamline at the Australian National University, which has an energy resolution between 60 and 100 meV. The total cross section (TCS) and the elastic and total inelastic integral cross sections in the energy range between 1 and 1000 eV have been computed within the Independent Atom Model using the Screening Corrected Additivity Rule approach. In addition, we have calculated elastic differential cross sections at selected incident energies. Our computations represent the first theoretical results reported for this target species, while our measured Ps formation cross sections are also novel. Comparison of the present TCS with the previous results from the University of Trento shows a good level of agreement at the lowest energies. We also provide a comparison between the present cross sections for 3H-THF and those from our earlier study on the parent molecule tetrahydrofuran.

Observation of threshold effects in positron scattering from the noble gases.

Channel coupling is a phenomenon that has been investigated for many scattering processes, and is responsible for the formation of cusps or steps in the cross sections for open scattering channels at, or near, the onset of a new scattering channel. It has long been speculated that the opening of the positronium formation channel may lead to the formation of such cusp features in the elastic positron scattering cross section. In this work, elastic scattering of positrons has been measured in the region of the positronium formation threshold for the noble gases He-Xe. Cusplike behavior is observed and, while the features which are observed appear broad, they represent a magnitude of between 4 and 15% of the total elastic cross section. No evidence is found of any other features in this region, at least within the uncertainty of the present data, discounting the possibility of scattering resonances.

[Tamoxifen or tamoxifen in combination with chemotherapy in adjuvant therapy of breast carcinoma. Results of a multicenter randomized study]. / Tamoxifen nebo tamoxifen v kombinaci s chemoterapií v adjuvantní lécbe karcinomu prsu. Výsledky multicentrické randomizované studie.

UNLABELLED: Between April 1994 and May 1997 103 breast cancer patients (pts), pT1c-3a, pN0-1, M0, were randomised after surgery to adjuvant tamoxifen (20 mg per day) or to tamoxifen plus CMF (C 500 mg/m2, M 40 mg/m2 and F 600 mg/m2 on days 1st and 8th q 28 day) in 6 cycles. The median age (49-72 years, median 58), tumour size, number of involved lymphnodes (0-3), estrogens receptor status, grade (I-III) and type of operation were well balanced among the 50 pts on tamoxifen and the 53 pts on tamoxifen plus CMF pts, preferably postmenopausal. RESULTS: Grade of toxicity according to WHO criteria was not higher then two in both arms. Toxicity both haematological and non-haematological was higher in the group treated with chemotherapy (0 vs 32 resp. 20%) except weight gain (52% in both group). After median follow-up of 42 mos five recurrences in tamoxifen and seven in tamoxifen plus CMF pts were observed (p = NS). The projected 3-y DFS is 92% for tamoxifen and 88% for tamoxifen plus CMF (p = NS). The 3-y OS is 88% for tamoxifen and 80% for tamoxifen plus CMF pts (p = NS). CONCLUSIONS: Both regimens are equally effective with higher toxicity in the group with combined chemo- and hormonal therapy.

[Comparison of adjuvant chemotherapy in breast carcinoma with a combination of cyclophosphamide, methotrexate, 5-fluorouracil (CMF) and AC (doxorubicin, cyclophosphamide). Initial results of a national cooperative study]. / Srovnání adjuvantní chemoterapie karcinomu prsu kombinací cyklofosfamid, metotrexat, 5-fluorouracil (CMF) a AC (doxorubicin, cyklofosfamid). První výsledky národní kooperativní studie.

The aim of this multicentric, prospective randomized trial is to evaluate and to compare, effects and toxicities of two chemotherapeutic combinations (AC and CMF) in adjuvant treatment of breast cancer. Both combinations were given in equitoxic doses and number of cycles was only four. There are 106 women treated for breast cancer T1c-3a, N0-1, M0 in the study. After surgery the patients were randomized, 54 for AC combination and 52 for CMF. We evaluate toxicity of this treatment in all patients in the study. Hematological and nonhematological side effects were comparable in both groups except alopecia (in the group AC was 100%). The study is not finished yet. Preliminary analysis does not show any difference between these two groups.

Beclomethasone relative availability of oral versus inhaled beclomethasone dipropionate from an HFA-134A metered dose inhaler.

3M has formulated a new chlorofluorocarbon-free (CFC-free) beclomethasone dipropionate (BDP) metered-dose inhaler (MDI) with the use of the propellant HFA-134a (HFA). Lung deposition studies demonstrated that the HFA BDP MDI delivers to the lungs approximately 56% of the BDP dose (ex-adaptor), a substantially higher percentage than the 5-30% delivered by conventional CFC BDP MDIs. As new sensitive bioanalytical methods are becoming available to quantitate systemic levels of inhaled corticosteroids, pharmacokinetic evaluations are emerging as sensitive and reproducible methods that can be used as a complement to the data obtained from lung deposition studies to assess and compare the performance of MDIs. The present study was designed to determine the beclomethasone (BOH) availability of oral BDP relative to inhaled HFA BDP as a first step to alloy MDI product comparisons in the future. Forty mild asthmatic patients completed this open-label, randomized, single-dose, two-period crossover study. Each patient received an oral dose of BDP (0.2, 0.5, 1, 2 or 5 mg) in one period and an inhaled dose of BDP (0.2 or 0.8 mg) in the other period, with four patients allocated to each of ten different treatment sequences. The BOH availability of orally administered BDP was approximately 40% relative to inhaled HFA BDP. In addition, the fraction of an oral dose that reaches the systemic circulation was estimated from the 40% relative availability and previous lung deposition data to be 0.26. These estimated pharmacokinetic parameters will be used in the future to further characterize the pharmacokinetics of inhaled BDP and to compare the performance of different MDI products.

Pharmacokinetics and dose proportionality of beclomethasone from three strengths of a CFC-free beclomethasone dipropionate metered-dose inhaler.

As part of a development program to offer alternatives to chlorofluorocarbon (CFC) containing metered-dose inhalers, beclomethasone dipropionate has been formulated in a CFC-free system at three strengths: 50, 100, and 200 micrograms/actuation ex valve. To measure serum levels and dose proportionality of the beclomethasone derived from beclomethasone dipropionate, 13 mild to moderate asthmatic patients received a single dose of eight inhalations from each strength according to a double-blind crossover design. Seven patients were studied over 4 h and six patients over 12 h. For the total doses of 400, 800, and 1600 micrograms studied over 12 h, Cmax and AUC increased in a ratio of 1:1.8:3.1. A good correlation was seen between the fine-particle mass delivered and the in vivo performance of the three strengths. From a clinical point of view, the predictable increases in serum levels with an increase in dose will permit the clinician to effectively titrate a patient with this product.

The role of fear in diagnosing cancer in time.

The causes of the relatively frequent late discovery of the breast cancer (40-60%) in Czech republic are numerous. One of them is the attitude of the patient herself to the disease. Fear and anxiety play are important role in seeing her doctor too late. Beliefs feelings and attitudes to treatment have been formed in potential patients mostly by negative experience and information. It is necessary to impress to the female population the idea that breast cancer can be curable and that the degree of successful treatment depends on early diagnosis and that fear and anxiety delaying the therapy are dangerous. The sources of fear are as follows: false image of incurable disease an idea of subsequent loss of an organs--the symbols of womanhood and sex-appeal physical and psychical degradation subsequent fears of losing a partner loss of social prestige and position at work considerable change in hitherto lifestyle. Own knowledge that these negative ideas are not quite true must be accepted not only by these who have been treated but first of all by those who could find themselves in such a difficult situation. Many other potential sources of fear and worries concern health care. Apart from the lack of interest reluctance and rudeness of hospital staff it is a chronic shortcoming of positive information and intensive health education. In authors group of 120 patients has been proved that mental feelings, fear and anxiety significantly influence the timeliness of diagnosing an illness and its whole course. It is the physicians foremost task to look for any possible ways of overcoming the sources of fear and anxiety and thus to help women to see a doctor as soon as possible. It would be a significant contribution to decreasing the number of advanced stages of breast cancer.

Radio-chemotherapy in the treatment of advanced cancer.

Tests in vitro and first clinical studies proved a radiosensitizing effect of cisplatin. In our study 40 patients with advanced resistant cancer of head, neck, lungs and rectum were treated by conventional radiotherapy and cisplatin. The drug was administrated in 10 mg after each irradiation. The tumor dose varied between 30-50 Gy in 3-5 weeks, within the total dose cisplatin 150-250 mg. In more than 70% of cases remarkable retreat of tumors, in some cases even a complete regression, were observed. Adverse reactions and toxicity often associated with administration of platin were very mild, so that even patients in rather poor physical condition could have been treated. Having performed no special hydratation serious nephrotoxicity was never observed. The potentiation of radiation by cisplatin can be therefore considered a relatively harmless treatment of inoperable advanced cancers useful especially in cases where other forms of palliative treatment have been exhausted or not feasible.

[Half-body irradiation in the palliative treatment of multiple bone metastases]. / Prínos pultelového ozárení k paliativní lécbe mnohocetných kostních metastáz.

The authors used as palliative analgetic treatment half-body irradiation in 13 patients with dissemination of a malignant tumour into bones. In six patients both halves of the body were irradiated. A long-term analgetic effect was observed in five patients (in one female patient more than 400 days, four patients 100-150 days), a short-term effect up to 100 days was recorded in six patients. The pain was not influenced in two patients. Mitigation of pain increased the patients' performance: according to the WHO scale in one case by 3 grades, in three patients by 2 grades, in six patients by 1 grade. The performance of three patients was not affected by irradiation. Side-effects of treatment were controlled by means of supporting treatment. They did not threaten life in any of the patients. The authors consider half-body irradiation an effective and useful analgetic treatment of multiple metastases into the bones.