Magnetic Rotation in the A = 80 Region: M1 Bands in Heavy Rb Isotopes

We have studied the isotopes ⁸²Rb₄₅, ⁸³Rb₄₆, and ⁸⁴Rb₄₇ to search for magnetic rotation which is predicted in the tilted-axis cranking model for a certain mass region around A = 80. Excited states in these nuclei were populated via the reaction ¹¹B + ⁷⁶Ge with E = 50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a γ-coincidence experiment using the spectrometer GASP we have found magnetic dipole bands in each studied nuclide. The regular M1 bands observed in the odd-odd nuclei ⁸²Rb and ⁸⁴Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13⁻ ≤ J^π ≤ 16⁻. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type π(fp)πg9/22νg9/2. This is the first evidence of magnetic rotation in the A ≈ 80 region. In contrast, the M1 sequences in the odd-even nucleus ⁸³Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.     

Animating field lines

The teaching of time-dependent electromagnetic phenomena could be made much easier if the evolution in time of the field lines could be visualized. In principle this can be achieved on a computer screen, but it is not a simple thing to do, since the process of drawing field lines is time consuming, and this rules out interactive animated presentations. In this work we restrict the problem to the representation of a superposition of uniform and dipolar fields and optimize the process making it extremely fast and precise. Special care is taken to ensure that the line density is everywhere proportional to the field intensity. The process is implemented as a Pascal procedure and exemplified by an animated representation of the field lines being expelled from a hollow conducting sphere which is suddenly immersed in a uniform field     

Cryptococcosis in HIV infection of man: an epidemiological and immunological indicator?

Cryptococcosis is an epidemiological and immunological indicator due to the absence of Cryptococcus neoformans as a saprophyte in immunocompetent humans and the advantage of specific C. neoformans culture. On this basis, a report is presented on the CD4 lymphocyte count of 36 AIDS patients suffering from cryptococcosis and other concomitant or missing opportunistic AIDS-defining infections. In 26 out of 36 patients, i.e. 72%, a CD4 lymphocyte count of < or = 50/microL (mean value 39.5%) was found. Cryptococcosis as the sole opportunistic infection was diagnosed in 5 cases (13.9%). In 31 cases, various combinations of AIDS-associated diseases were found: Pneumocystis carinii pneumonia (PCP) (n = 19), cytomegalovirus infection (CMV) (n = 10), Kaposi's sarcoma (n = 6), Mycobacterium avium intracellulare infection (MAI) (n = 5), pneumonia (n = 2), toxoplasmosis (n = 2), Candida esophagitis (n = 1), tuberculosis (n = 1), lambliasis (n = 1), salmonellosis (n = 1) and wasting syndrome (n = 5). The conspicuous simultaneous occurrence or succession of pneumocystosis and cryptococcosis and the contrasting absence of aspergillosis and mucormycosis (zygomycosis) are commented. Based on the present observations in HIV-infected persons in Berlin, a CD4 lymphocyte count of < 150/microL may be used as a parameter indicating a predisposition for cryptococcosis as an airborne AIDS-defining infection. Attention is drawn to bird droppings as the sole habitat of C. neoformans and accidental niche of various other microorganisms.     

Infants communicate in order to be understood.

Infants intentionally communicate with others from before their 1st birthday. But there is some question about how they understand the communicative process. Do they understand that for their request to work the recipient must both understand the request and be cooperatively disposed to fulfill it? On the basis of the study by Shwe and Markman (1997), we developed a new paradigm that tested whether and how 18-, 24-, and 30-month-old children repair a failed request. Children at all ages repaired their requests in the case of a misunderstanding even if they had obtained the requested object already. They also repaired differently depending on the precise reason for the communicative failure (e.g., misunderstanding the referent versus the communicative intent) and did not repair in the case of correct understanding, even if they did not get the requested object. Thus, from very early in their communicative careers, young children operate with a basic understanding of the mental and cooperative nature of human communication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ultrasound monitoring of the influence of different accelerating admixtures and cement types for shotcrete on setting and hardening behaviour

The possible use of ultrasound measurements for monitoring setting and hardening of mortar containing different accelerating admixtures for shotcrete was investigated. The sensitivity to accelerator type (alkaline aluminate or alkali-free) and dosage, and accelerator-cement compatibility were evaluated. Furthermore, a new automatic onset picking algorithm for ultrasound signals was tested. A stepwise increase of the accelerator dosage resulted in increasing values for the ultrasound pulse velocity at early ages. In the accelerated mortar no dormant period could be noticed before the pulse velocity started to increase sharply, indicating a quick change in solid phase connectivity. The alkaline accelerator had a larger effect than the alkali-free accelerator, especially at ages below 90 min. The effect of the alkali-free accelerator was at very early age more pronounced on mortar containing CEM I in comparison with CEM II, while the alkaline accelerator had a larger influence on mortar containing CEM II. The increase of ultrasound energy could be related to the setting phenomenon and the maximum energy was reached when the end of workability was approached. Only the alkaline accelerator caused a significant reduction in compressive strength and this for all the dosages tested.     

Comparison of Different Genotoxic Tests for Biological Monitoring of Coke Oven Workers. Preliminary Results

Chemical by-products of coke production are classified by IARC as carcinogenic in humans. Polycylic aromatic hydrocarbons (PAH) are the main compounds involved in carcinogenic and mutagenic activities of coke oven smokes, but many other compounds are present in emissions and could be involved in these activities. PAH analysis of the atmosphere indicated external contamination, but is not sufficient to evaluate the risk for exposed workers. The aim of this study was to evaluate relationship between atmospheric analysis of PAH and genotoxic markers in coke oven workers'white cells compared to controls. One hundred fifty-five exposed workers'samples were analyzed. They were selected in 5 coke production sites using a complete questionnaire allowing one to exclude all confounding factors. Two equal groups of smokers and nonsmokers were analysed. Analysis of chromosomal aberrations (CA), sister chromatid exchange (SCE), micronucleus (MN) and DNA-adduct formation using ³²P-postlabelling were performed on leucocytes. Each worker was equiped with an individual pump during the shift, for analysis of 16 PAH.

All markers were strongly modified by smoking habits. In smokers, CA, SCE and MN were not influenced by exposure to PAH. The number of DNA-adducts was increased with PAH concentration. In non smokers, we have observed an increaseof breaks / cells and of the percentage of cells with aberrations. Number of MN and SCE were unchanged. The number and the amount of DNA-adducts were strongly increased in exposed workers. DNA-adducts appear to be the best marker for genotoxic risk assessment.