Determination of the uranium content of environmental samples by gamma spectroscopy of the 1.0015 MeV radiation in 234U

A method of determining the uranium content of environmental samples by gamma spectroscopy of the 1.0015 MeV gamma radiation of the 234Pam (beta-) 234U leads to 234U daughter decay is described. The detection limit is 1 nCi/kg sample. The transition probability has been determined to be 0.87 +/- 0.03%.     

Some computational considerations in eddy-current NDE

Theoretical calculations of eddy-current phenomena often involve the numerical evaluation of various integral expressions. A discussion of some of the possible evaluation methods and of the factors to be considered in choosing a method is presented.     

Cardiac surgery in patients with end-stage renal failure

End-stage renal failure is commonly considered a significant factor for an increased risk after coronary artery bypass grafting. This holds true for patients who have received a kidney transplant (NTX group) as well as for patients who require chronic hemodialysis (HD group). To assess the risk in our population we performed a retrospective analysis of 22 patients with end-stage renal failure (HD group: 17, NTX group: 5) who underwent cardiac surgery. The perioperative course was compared to a normal population. In addition to standard data we assessed the following factors: renal failure etiology, risk factors, concurrent diseases, duration of renal failure, function of renal graft, ECG (paying special attention to signs of previous myocardial infarctions and rhythm disorders), results of cardiac catheterization and coronary angiography, NYHA class and urgency of operative intervention. Complications and mortality were the main measures of the perioperative course. We analyzed the hospital charts retrospectively and requested the patients' physicians to complete a questionnaire about the patient's present condition. All HD group patients were dialyzed on the day before surgery. The first postoperative HD was performed for hyperkalemia or signs of volume overload (pulmonary capillary wedge pressure > 20 mmHg) when signs of pulmonary function deterioration were seen. HD was successful in treating these conditions. 3 of the 17 patients on HD expired postoperatively, 4 died within 3 years, all of unrelated diseases. Mortality and morbidity was 0% in the NTX group. In one NTX patient who required intermittent HD preoperatively because of poor renal graft function, renal function improved postoperatively, presumably secondary to better renal perfusion, and he did not require HD after his cardiac surgery. By surgical intervention the NYHA class of all patients improved (by 1.6 on the average) as well as their quality of life. Because of these good short- and long-term results and relatively low operative risk we support an approach of prompt work-up and surgical intervention when necessary in HD and NTX patients.     

Ultramicroscopic studies on the human corpus luteum menstruationis and graviditatis

In high active steroid producing cells of the human corpus luteum we can find in the cytoplasm a well developed smooth endoplasmic reticulum in form of smooth tubules and homogenously spread vesicles resulting from an active metabolic process. We also find specific concertinalike folded membrane complexes which too belong to the endoplasmic reticulum. Numerous mainly tubular mitochondria contain dense lipoid inclusions. Their close conection with the endoplasmic vesicles is expression of a direct interaction of both cell organelles in progesterone production. The transport of the intracellular formed steroid hormones to the capillary takes place via locally enlarged intercellular spaces which communicate with the pericapillary space. On the other hand there are pericellular canaliculi which are coated with a membrane. They have no direct connection to the pericapillar space.     

Equilibrium sampling through membranes of freely dissolved copper concentrations with selective hollow fiber membranes and the spectrophotometric detection of a metal stripping agent

A sensitive spectrophotometric method for the determination of freely dissolved copper concentrations in aqueous samples after preconcentration with hollow fiber membrane extraction has been developed. The method is based on the equilibrium sampling through a selective membrane into an acceptor solution containing 4-(pyridyl-2-azo)resorcinol (PAR), which serves as stripping agent and metal indicator. Negligible extraction of interferences and equilibrium enrichment of copper allowed for selective spectrophotometric determination of the Cu-PAR complex. Some important extraction parameters such as acceptor composition, shaking, equilibrium time, and sample volume were studied. The optimized methodology showed good linearity in the range of 5-100 microg/L, an enrichment factor of 93, good repeatability and reproducibility (RSDs < 6%, n = 6), and a detection limit of 4 microg/L. The cationic metals Ni2+, C(2+, Cd2+, Fe3+, Pb2+, Zn2+, and Mn2+ were shown not to interfere with the measurement of Cu2+. Measurements on samples containing mixtures of various ligands and cations were in good agreement with theoretically calculated concentrations, and the method was also applied to environmental samples. The developed technique requires less labor and less sophisticated equipment than conventional methods typically based on atomic absorption spectrometry or ICP.     

Bounds on the OBDD-size of integer multiplication via universal hashing

Bryant [On the complexity of VLSI implementations and graph representations of boolean functions with applications to integer multiplication, IEEE Trans. Comput. 40 (1991) 205-213] has shown that any OBDD for the function MUL_n-1,n, i.e. the middle bit of the n-bit multiplication, requires at least 2^n/8 nodes. In this paper a stronger lower bound of essentially 2^n/2/61 is proven by a new technique, using a universal family of hash functions. As a consequence, one cannot hope anymore to verify e.g. 128-bit multiplication circuits using OBDD-techniques because the representation of the middle bit of such a multiplier requires more than 3·10¹⁷OBDD-nodes. Further, a first non-trivial upper bound of 7/3·2^4n/3 for the OBDD-size of MUL_n-1,n is provided.     

Sediment dilution method to determine sorption coefficients of hydrophobic organic chemicals

Sorption coefficients of hydrophobic organic chemicals (HOC) to sediments and soils can easily be underestimated in traditional batch experiments, especially because analysis of the aqueous concentration often includes compounds sorbed to colloidal organic matter. In this work, a "sediment dilution approach" has been combined with measurements of freely dissolved concentrations to determine sorption coefficients of five chlorobenzenes and two chloroanilines in spiked sediment and of two unknown chemicals in field-contaminated sediment. A range of sediment suspensions with different sediment-water ratios was made. Freely dissolved concentrations in these suspensions were measured by negligible depletion solid-phase microextraction (nd-SPME). Sediment-water sorption coefficients (KD) were derived from the decrease of the freely dissolved concentrations as a function of the "dilution factor" (DF = volume water/mass sediment). The determined sorption coefficients were very similar to literature values. The experimental setup provides sorption coefficients without the need for total extractions, and the negligible depletion SPME technique does not require phase separation. The proposed method might be an alternative for batch equilibrium experiments to determine sorption coefficients.     

Improvement of utero-placental perfusion by transcutaneous nerve stimulation (author's transl)

A report is given on 37 patients with a diminished utero-placental perfusion. 12 patients underwent only once, 25 patients daily over 2 to 3 weeks a transcutaneous lumbo-sacral electric nerve stimulation. Both, the 12 patients stimulated only once and the 25 patients with daily stimulation, showed a significant increase of utero-placental perfusion measured by the method of radioisotope placental perfusion. Transcutaneous nerve stimulation (TNS) therefore could be used for therapeutic purpose in cases of placental dysfunction.