RADIATION MEASUREMENT OF RADIOISOTOPE IN MINERAL DEPOSIT AT SUBDISTRICT OF MIDDLE KUPANG WEST TIMOR ISLAND INDONESIA

The general objective of this work was investigation of radioisotope distribution and accumulation center in mineral deposit at sub-district of Middle Kupang West Timor Island Indonesia. The purposes of research were: to map of radioisotope distribution in the mineral deposit, to estimate area of radioisotope accumulation center in the mineral deposit, to establish range of nuclear radiation counts in the center region of radioisotope content in mineral deposit. The general methods used in this research were observation, survey, mapping, analysis, and interpretation. Procedures detail of research consists of: observe and identify the potential region and plot gridding, calibrate equipment necessary, measure background count in around of survey location and nuclear radiation in the survey location, plot of three dimensions curve and contour after corrected by background count. Based on geology information or geology data (drilling data) three depth levels determined (about 20 m, 40 m and 60 m), Radiation powers were calculated for estimation of accumulation center of radioisotope in deposit mineral, and contour and three dimensions curves of radiation power of radioisotope in deposit mineral were plotted. Results: Based on three dimensional curves and contour map (radiation counts and radiation powers on three levels) of radioisotope in mineral deposit respectively was distributed on area 3.00 x 106 m2, and 1.56 x 104 m2. The interval of radiation counts of radioisotope in mineral deposit was 10 counts per minute-137 counts per minute. Keywords: Radiation, measurement, radioisotope, mineral, deposit

Chemotactic responses of Dictyostelium discoideum amoebae to a cyclic AMP concentration gradient: evidence to support a spatial mechanism for sensing cyclic AMP

The motile responses of Dictyostelium discoideum amoebae to a cyclic AMP (cAMP) concentration gradient were examined using a novel assay system. In this system, a cAMP concentration gradient was generated, while the overall cAMP concentration could be either increased or decreased in a chamber containing amoebae. The chemotactic responses of amoebae were examined immediately after they had been subjected to the cAMP concentration gradient. Amoebae moving in random directions in a reference solution ascended a cAMP concentration gradient after they had been exposed to the gradient irrespective of whether there was an increase or a decrease in the overall cAMP concentration. This strongly supports the idea that D. discoideum amoebae can sense a spatial cAMP gradient around them and that this causes their chemoaccumulation behavior. Ascending locomotion became less conspicuous when the amoebae were treated with a homogeneous cAMP solution for approximately 8 min before exposure to a cAMP gradient. This cAMP pretreatment reduced the sensitivity of the amoeba to a cAMP concentration gradient. The cAMP concentration gradient could be reversed in less than 30 s in this assay system, allowing the generation of a cAMP wave by accumulating amoebae to be mimicked. The ascending amoebae continued to move in the same direction for 1–2 min after the gradient had been reversed. This is consistent with the well-known observation that reversal of a cAMP concentration gradient experienced by the amoebae passing through a cAMP wave does not negate their chemotactic movement towards the accumulation center.