Radioisotope Tracer Method Research Articles

Characterisation of soil phosphorus forms in the soil-plant system using radioisotopic tracer method

Soil incubation and pot experiments were conducted to follow the sorption processes of added phosphorus (P) fertiliser using the radioisotope tracer technique. Increasing doses of P fertiliser (40, 80, 160, 320 mg P/kg soil) were added to Chernozem and Arenosol and incubated for 1, 3, and 13 weeks. After incubation, perennial ryegrass (Lolium perenne L.) was sown in one group of pots, and the experiment had been continuing for another 9 weeks. The yield, grass P uptake, isotopically exchangeable (P<sub>IE</sub>), water-soluble (P<sub>W</sub>), and ammonium lactate soluble phosphorus (P<sub>AL</sub>) fractions of soils were measured. On Chernozem, plant P uptake, P<sub>IE</sub>, P<sub>W</sub> and P<sub>AL</sub> were significantly less in the case of the longest incubation period compared to shorter incubations. This suggests a transformation of P into tightly sorbed form. On Arenosol, there were only small changes in the parameters as the incubation period increased, suggesting less intense P transformation to tightly sorbed form. The P<sub>W</sub>/P<sub>IE</sub> ratio enhanced with increasing P-doses, and the ratios were higher on Arenosol. On Arenosol, the higher P doses caused a greater increase of P<sub>W</sub> than on Chernozem. The P<sub>IE</sub> + P<sub>W</sub> showed a good correlation with plant P uptake proving this value can be a good indicator of plant-available phosphorus.

Study of fast and slow consecutive processes by heterogeneous isotope exchange using P-32 radiotracer

The sorption of phosphate on soils is studied by radioisotopic tracer method. Two consecutive processes with rather different rates were differentiated: namely the heterogeneous isotope exchange between the phosphate in the soil solution and the weakly sorbed phosphate (fast reaction), and the transformation of weakly sorbed phosphate to tightly sorbed phosphate (slow reaction). In this paper, it is shown how the rate constants of these two processes can be determined by a radiotracer with a relatively short half-life.

Sentinel lymph node navigation surgery for early stage gastric cancer.

We attempted to evaluate the history of sentinel node navigation surgery (SNNS), technical aspects, tracers, and clinical applications of SNNS using Infrared Ray Electronic Endoscopes (IREE) combined with Indocyanine Green (ICG). The sentinel lymph node (SLN) is defined as a first lymph node (LN) which receives cancer cells from a primary tumor. Reports on clinical application of SNNS for gastric cancers started to appear since early 2000s. Two prospective multicenter trials of SNNS for gastric cancer have also been accomplished in Japan. Kitagawa et al reported that the endoscopic dual (dye and radioisotope) tracer method for SN biopsy was confirmed acceptable and effective when applied to the early-stage gastric cancer (EGC). We have previously reported the usefulness of SNNS in gastrointestinal cancer using ICG as a tracer, combined with IREE (Olympus Optical, Tokyo, Japan) to detect SLN. LN metastasis rate of EGC is low. Hence, clinical application of SNNS for EGC might lead us to avoid unnecessary LN dissection, which could preserve the patient's quality of life after operation. The most ideal method of SNNS should allow secure and accurate detection of SLN, and real time observation of lymphatic flow during operation.

A prospective comparative study to assess the contribution of radioisotope tracer method to dye-only method in the detection of sentinel lymph node in breast cancer

BackgroundMetastasis in the axillary lymph nodes is the most important known prognostic factor for breast cancer. We aimed to investigate the contribution of the radioisotope tracer method to the dye-only method by performing sentinel lymph node biopsy on the same patient group during a single surgical session.MethodsForty-two patients who underwent operations in our clinic from February 2010 to October 2011 and with masses of <5 cm and clinically and radiologicallly negative axilla (T1-2 N0) were prospectively included in this study. After paraffin examination results were obtained, the numbers and metastatic states of the lymph nodes that were unidentifiable during surgery (although they were stained) but were detected by a gamma probe, lymph nodes that were only stained, lymph nodes that were only radioactive (hot), and lymph nodes that were both stained and radioactive (stained-hot) were determined in all patients. In patients who underwent axillary lymph node dissection, the total numbers of lymph nodes removed and their metastatic states were determined separately.ResultsAt least one blue-stained sentinel lymph node was identified in all patients during the blue-stained lymph node detection stage. The average number of sentinel nodes removed at this stage was 2.1 ± 1.1. In the second surgical stage (the stage in which nodes with axillary counts were investigated with the gamma probe) in these 41 patients, at least one additional hot node was removed, or at least one of the nodes that was removed because it was blue was also hot. In addition to the lymph nodes removed in the dye stage, 34 hot lymph nodes were excised from 21 patients. Overall, the average number of hot lymph nodes removed was 2.9 ± 1.5. In all patients, subsequent frozen sections and histopathological examinations were 100% concordant with the sentinel lymph nodes that were removed; the stained sentinel lymph nodes that were removed first did not affect the decision to perform axillary dissection.ConclusionThe results of our study indicate that performing sentinel lymph node biopsy with dye only is sufficient and as effective as the combined method.

Preparation and Biodistribution of Tyrosine Modified Multiwall Carbon Nanotubes

The functional modification of the outer surface of carbon nanotubes (CNTs) is likely to improve their biocompatibility. Therefore, CNTs have attracted great attention not only in electrical, optical and mechanical applications but also in biological and pharmaceutical applications. Thus, it is important to examine the biodistribution and kinetics of the carbon-based nanotubes when they are introduced into living systems. Here, we synthesized and characterized tyrosine-functionalized carbon nanotubes (CNTs-Tyr), and assessed the biodistribution profile of CNTs-Tyr in mice, following three different administrations by the 125I radioisotope tracer method. CNTs-Tyr was delivered quickly around the entire body, and different absorbtion and biodistribution profiles of CNTs-Tyr were observed with different routes of administration. Following intravenous injection, CNTs-Tyr accumulated within 24 h mainly in the lungs and slightly in the spleen and liver, and may be eliminated primarily through the kidneys. After administration via gavage, most of the CNTs-Tyr were eliminated through the intestine, and rarely delivered into the organs. After intraperitoneal injection, CNTs-Tyr accumulated in the spleen and were rapidly eliminated from the other organs within 24 h. The blood circulation half-life of CNTs-Tyr was about 4.4 h. The behavior of CNTs-Tyr in mice is somewhat different from the results reported previously. This suggests that the functionalized group may affect the affinity of carbon nanotubes for particular organs. The results provide basic biological information for the biomedical application and risk assessment of CNTs.

Effects of macronutrient additions on nickel uptake and distribution in the dinoflagellate Prorocentrum donghaiense Lu

The influences of macronutrient additions on nickel (Ni) uptake and distribution in the subcellular structures and macromolecular components of the dinoflagellate Prorocentrum donghaiense Lu were examined using a radioisotope tracer method. The results showed that nitrate addition enhanced the uptake of Ni by P. donghaiense, whereas phosphate addition inhibited Ni uptake at high-Ni concentration. Nitrate or phosphate addition significantly affected Ni distribution in the subcellular structures and components. The majority of Ni was found in the soluble substances (>70%) and in the proteins (55.0–79.6%) of the algal cells. Urea reduced the Ni content in the amino acid-carbohydrate but elevated its content in proteins, and shown significantly correlated with the protein content of the algal cells. Thus, nutrient enrichment could influence both metal uptake and its distribution in the subcellular structures and components of the phytoplankton, as well as its subsequent transfer in marine food chains.

Investigation of sulfur behavior on CoMo-based HDS catalysts supported on high surface area TiO 2 by 35S radioisotope tracer method

Three series of CoMo catalysts (MoO 3: 6, 11, 16 wt.%) with various Co/Mo molar ratios were prepared by successive incipient wetness impregnations of a titania sample previously prepared by the pH swing method, which provides a TiO 2 carrier with a high SSA (134 m 2 g −1) and excellent mechanical properties. DBT HDS activity of the catalysts increased with addition of cobalt up to Co/Mo = 0.4 and then decreased for higher ratios, irrespective of the Mo loading. The results of a [ 35S]DBT HDS method showed that S 0, the amount of labile sulfur atoms, increased in parallel with the activity when adding Co up to a molar ratio of 0.4. In contrast, unlike on CoMo/Al 2O 3 catalysts, only a slight increase in k RE, the H 2S release rate constant, was observed upon Co addition. This was due to formation of the TiMoS phase: while formation of Ti S * Mo bonds favorably induces an increase in sulfur mobility on Mo/TiO 2 catalysts, electronic density on Mo atoms increases, which limits the promoting effect of Co on mobility of S a sulfur atoms bridged between Mo and Co. Further, while the increase in HDS activity upon Co addition on a uniform MoS 2 monolayer on TiO 2 was in rather good agreement with the quantitative and kinetics data of the 35S tracer method, over MoS 2 slabs on TiO 2 this increase was larger than that expected from the results of the 35S tracer method. This was attributed to the presence of □ * and □ a CUS, i.e. catalytic sites that are not replenished with sulfur, at the steady state. A larger number of □ * CUS was present at low Mo wt.% or for low Co/Mo. As these particular catalytic sites are in the form of CUS at the steady state, they are not accounted by the [ 35S] radiotracer method. This explains the differences observed between the experimental DBT HDS promotion and the promotion deduced from the increase in k RE and S 0.

Investigation of Sulfur Behavior on Mo-based Hydrodesulfurization Catalysts Supported on High Surface Area TiO&lt;sub&gt;2&lt;/sub&gt; by &lt;sup&gt;35&lt;/sup&gt;S Radioisotope Tracer Method

Mo catalysts were prepared by impregnation of titania synthesized by the pH swing method which provides a TiO2 carrier with a high specific surface area (134 m2·g−1) and excellent mechanical properties. Dibenzothiophene (DBT) hydrodesulfurization (HDS) activity was estimated over the obtained catalysts under typical HDS reaction conditions for various Mo contents. The activity increased linearly with Mo content up to ca. 16 wt% MoO3 and then decreased for higher Mo loadings. The sulfur behavior on the sulfided Mo/TiO2 catalysts was elucidated under the reaction working conditions using a 35S radioisotope tracer method, or the HDS of 35S-labeled DBT. The results indicated that at a given temperature the H2S release rate constant (kRE) was almost constant irrespective of the Mo content, and the amount of labile sulfur (S0) increased linearly with the Mo content in parallel with the activity up to ca. 16 wt% MoO3. The optimal Mo dispersion was 5.2 atom/nm2, which is higher than the optimal Mo dispersion on 70 m2·g−1 TiO2 (4.2 atom/nm2). Comparison of kRE and S0 of the titania-based catalysts and the alumina-based catalysts suggested that the active phase consists of a 'TiMoS' phase exhibiting a promoting effect similar to the well-known 'CoMoS' phase (promotion of the MoS2 active phase by Ti atoms).

Hydrodesulfurization and hydrogenation reactions on noble metal catalysts: Part II. Effect of partial pressure of hydrogen sulfide on sulfur behavior on alumina-supported platinum and palladium catalysts

Hydrodesulfurization (HDS) reactions of the 35S radioisotope-labeled dibenzothiophene (DBT) were carried out over 10% Pd/Al 2O 3 and 2% Pt–10% Pd/Al 2O 3 catalysts. The total amount of the sulfur ( S total) accommodated on the catalysts and the amount of labile sulfur ( S 0) participating in the HDS reaction were determined using a 35S radioisotope tracer method. The sulfided state of noble metal sulfides on two catalysts changed depending on the partial pressure of H 2S in the reaction atmosphere. Taking into account the amount of the sulfur accommodated on the alumina support, the sulfided Pt or Pd species on the catalysts are presented in the form of PdS x or PtS x ( x=0–0.25) in lower partial pressures of H 2S under 5.2 kPa. At the same time, all the sulfur incorporated into the catalyst were almost the labile sulfur. On the other hand, the sulfur further incorporated into the Pd catalyst with further increasing the partial pressure of H 2S in a reaction system over 5.8 kPa, resulting in the formation of the phase of PdS. In contrast, there was no significant change in both S total and S 0 even though the partial pressure of H 2S in the atmosphere increased into ca. 17 kPa in the case of Pt–Pd catalysts. The structures of PdS 0.25 and PtS 0.25 in the Pt–Pd catalyst remained.

Elucidation of sulfidation state and hydrodesulfurization mechanism on ruthenium–cesium sulfide catalysts using 35S radioisotope tracer methods

Alumina-supported ruthenium–cesium catalysts were presulfided using [ 35S]H 2S pulse tracer method to evaluate their sulfidation state. Subsequently, using these previously 35S-labeled catalysts, HDS reactions of dibenzothiophene (DBT) were performed and the mobility of 35S introduced during the presulfidation stage was investigated. The results showed that the amount of labile sulfur ( S 0) was much smaller than the total amount of sulfur accommodated on the catalyst (S total). DBT conversion and S total increased linearly with Ru content. In a second part, labile sulfur amount was also determined under the catalyst working conditions and different results were obtained. Indeed, when the catalysts were marked with [ 35S] and with [ 35S]DBT under HDS reaction conditions, the obtained labile sulfur quantities (S 0A) were significantly higher than the ones measured during the presulfidation stage ( S 0). These results showed that the labile sulfur is not formed on RuCs catalysts until the HDS reaction proceeds, which is quite different from that reported before for Mo, Pt, or Pd systems.

Characterization of sulfur exchange reaction between polysulfides and elemental sulfur using a 35S radioisotope tracer method.

A sulfur exchange reaction between di-tert-butylpolysulfides and elemental sulfur was examined using a 35S tracer method and the reaction mechanism was discussed.

Elucidation of sulfur behavior in ultra deep hydrodesulfurization using [formula omitted] radioisotope tracer methods : Part I. Hydrodesulfurization of dibenzothiophene with lower concentration over a sulfided Ni-Co-Mo/Al 2O 3 catalyst

In order to investigate the behavior of sulfur on sulfided Ni-Co-Mo/Al 2O 3 catalyst in the ultra deep hydrodesulfurization (HDS), a novel radioactive 35 S tracer method was developed. Both radioactive 35 S -labeled elemental sulfur and dibenzothiophene (DBT) were used to label the catalyst under the practical HDS, and then HDS reactions of DBT of 0.001–1.0 wt.% (content of sulfur: ca. 2–200 ppm) were carried out over the 35 S -labeled catalyst at 260 °C and under 5.00 MPa. By tracing the changes in the radioactivity of formed [ 35 S ]H 2S, the behavior of sulfur on the catalyst was determined. Either [ 35 S ]S or [ 35 S ]DBT can be used to label the catalyst well and the behavior of sulfur on the catalyst did not change with the type of 35 S agent. The release rate of [ 35 S ]H 2S from 35 S -labeled catalyst in the HDS of DBT became remarkably slow when the concentration of DBT decreased to less than 0.01 wt.%. The amount of labile sulfur participating in the HDS of DBT also decreased with decreasing the concentration of DBT. This indicates that the labile sulfur on the catalyst is not uniform and only some part but not all of labile sulfur participates in the ultra deep HDS.

Elucidation of promotion effect of cobalt and nickel on Mo/TiO2 catalyst using a 35S tracer method

Abstract A series of CoMo and NiMo catalysts supported on TiO 2 with various Co/Mo and Ni/Mo molar ratios were prepared to investigate the relationship between the nature of the support and the promotion effect of Co and Ni. The catalytic activities of these catalysts for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) were measured. The HDS activity of CoMo/TiO 2 catalysts increased linearly with the addition of cobalt up to Co/Mo ratio of 0.6 and then decreased slightly above this value. Similarly, the HDS activity of NiMo/TiO 2 catalysts increased linearly with the addition of nickel up to Ni/Mo ratio of 0.6 and remained almost constant above this value. The sulfur mobility on the CoMo/TiO 2 and NiMo/TiO 2 catalysts under the reaction conditions was elucidated by a 35 S radioisotope tracer method using 35 S -labeled DBT. The amount of labile sulfur ( S 0 ) increased linearly with the addition of cobalt or nickel up to molar ratio of 0.6. In contrast, no significant difference in the rate constants of H 2 S release ( k RE ) was observed between Co- or Ni-promoted catalysts and non-promoted Mo catalysts at a given temperature. Therefore, the increase in catalytic activity with the addition of cobalt or nickel can be attributed to an increase in the number of active sites.

Elucidation of Behavior of Sulfur on Mo Catalysts Supported on TiO2 with Various Surface Areas Using 35S Tracer Methods

A series of Mo catalysts supported on TiO2 with various surface areas were prepared. In hydrodesulfurization (HDS) of dibenzothiophene (DBT) the activities of the series of catalysts were estimated. The results show that the activities of the series of catalysts increased linearly with the surface areas of TiO2 supports. The sulfur mobility on the sulfided Mo/TiO2 catalysts under the reaction conditions was elucidated by a 35S radioisotope tracer method using 35S-labeled DBT. The results suggest that the sulfur exchange rate constants (kRE) were approximately the same for all catalysts at a given temperature and that the amount of labile sulfur (S0) increases linearly with the surface area of TiO2 supports. The sulfidation states of the series of catalysts were also investigated by a 35S radioisotope pulse tracer method using 35S-labeled H2S. The results indicate that in spite of the coverage of Mo species on TiO2 support, the sulfidation of TiO2 support would still occur at 300°C. The sulfided catalysts could be reduced under H2 atmosphere.

Elucidation of dimethylsulfone metabolism in rat using a 35S radioisotope tracer method

The metabolism of dimethylsulfone was quantified for possible medical applications based on the hypothesis that the agent may be metabolized to yield methionine or its metabolites. The 35S-labeled dimethylsulfone and methionine are orally administrated to rat. Over 80% of the administrated dimethylsulfone is metabolized in the rats tissues, and 59.7–79.1% of it is then excreted into the urine as 35S-containing metabolites; 3.5–10.3% of the same remains incorporated in the tissues. The uptake of radioactivity, though different from the quantity of methionine in percentage at the retained site, is observed in the blood, spleen and hair, and over 80% of the administered [ 35S] dimethylsulfone is excreted the same day. Meanwhile, the distribution of the 35S concentrations of both agents in the rat system suggests that this compound had been metabolized to yield certain sulfur-containing compounds.

Elucidation of promotion effect of nickel on Mo/Al 2O 3 and Co-Mo/Al 2O 3 catalysts in hydrodesulfurization using a [formula omitted] radioisotope tracer method

Hydrodesulfurization (HDS) reactions of radioactive 35 S -labeled dibenzothiophene (DBT) were carried out over a series of Ni-promoted Mo/Al 2O 3 and Co-Mo/Al 2O 3 catalysts at temperatures between 220 and 280 °C and under 5.00 MPa pressure. HDS and hydrogenation (HYD) activity of Mo/Al 2O 3 catalyst were remarkably enhanced with the addition of nickel, the maximum promotional effect of Ni occurred with a Ni/Mo ratio of ca. 0.5. The amount of labile sulfur ( S 0) and the release rate constant of [ 35 S ]H 2S ( k RE) increased significantly with the addition of nickel, indicating that nickel makes the sulfur on the catalysts more mobile. The promoting effect of nickel on the activity of Mo/Al 2O 3 catalyst was attributed to the formation of more active sites. Further, the HDS activity of Co-Mo/Al 2O 3 catalyst was also enhanced with the addition of nickel; its maximum promotional effect occurred with a Ni/Mo ratio of ca. 0.2 for Ni-Co-Mo catalysts. Ni-promoted Co-Mo/Al 2O 3 catalysts with lower Ni/Mo ratio had greater S 0 and k RE values than Co-Mo/Al 2O 3 catalyst and resulted in higher HDS activity. This indicates that more active sites were formed with adding Ni to Co-Mo/Al 2O 3 catalyst, although their numbers were limited. On the other hand, the promoting effect of nickel to Mo/Al 2O 3 almost disappeared with adding cobalt into Ni-Mo/Al 2O 3 catalysts, suggesting that cobalt hindered the formation of more active Ni-Mo-S phase or covered the phase.

Elucidation of sulfidation state and hydrodesulfurization mechanism on Mo/TiO2 catalyst using [formula omitted] radioisotope tracer methods

In hydrodesulfurization (HDS) of dibenzothiophene (DBT) the activities on the Mo/TiO2 catalysts with various Mo contents were estimated under the typical HDS reaction conditions. The results show that the activities of the catalysts increased linearly with Mo content up to 6wt.% MoO3, which means that the monolayer dispersion of MoO3 on TiO2 support is maintained up to 6wt.% MoO3. The sulfidation states of MoO3/TiO2 catalysts were investigated using a 35S radioisotope pulse tracer method. The results showed that the sulfidation of TiO2 support would also occur. Moreover, the sulfur mobility on the sulfided 6% MoO3/TiO2 catalyst under the reaction conditions was elucidated by a 35S radioisotope tracer method using 35S-labeled DBT. The results suggested that, compared to Mo/Al2O3 catalyst, Mo/TiO2 catalyst showed a little higher amount of labile sulfur (S0) and about two times higher release rate constant of H2S (kRE), which indicated that higher mobility of sulfur was obtained on sulfided Mo/TiO2 catalyst.

Investigation of Cobalt Promotion on TiO2-supported Mo Catalysts Using a 35S Tracer Method.

A series of CoMo catalysts supported on TiO2 with various Co/Mo molar ratios were prepared to investigate the relationship between the support and the promoting effect of cobalt. The catalytic activities of these catalysts were measured for the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The HDS activity of Mo/TiO2 catalysts increased remarkably with increased addition of cobalt up to Co/Mo ratio of 0.2 and then increased slightly above this value. The HYD activity of these catalysts remained almost constant with increasing Co/Mo ratio. Sulfur mobility on the sulfided CoMo/TiO2 catalysts under the reaction conditions was investigated by a 35S radioisotope tracer method using 35S-labeled DBT. The rate constants of H2S release (kRE) for Co-promoted catalysts were approximately the same as those for non-promoted Mo catalysts at a given temperature, indicating that the addition of cobalt did not affect the mobility of sulfur over Mo/TiO2 catalysts. In contrast, the amount of labile sulfur (S0) increased remarkably with the addition of cobalt up to Co/Mo ratio of 0.2 and then increased slightly above this value. The increase in the catalytic activity with the addition of cobalt is probably due to an increase in the number of active sites.

Elucidation of Sulfidation State and Hydrodesulfurization Mechanism on TiO2 Catalysts Using 35S Radioisotope Tracer Methods

The hydrodesulfurization (HDS) activities of sulfided TiO2 with various surface areas were characterized under the typical HDS reaction conditions. The results showed that HDS activities increased linearly with increasing surface area of TiO2, suggesting that the surface sulfide TiS2 is the active phase of the HDS reaction on sulfided TiO2 catalyst. The sulfidation states of TiO2 with various surface areas were investigated using a 35S radioisotope pulse tracer method. The results showed that the Ti atoms on the surface of TiO2 could be completely sulfided to TiS2 at 400°C, whereas the sulfidation of Ti atoms in the bulk of TiO2 would occur slowly at 500°C. When the sulfided TiO2 was reduced in H2 at 400°C, TiS2 was reduced to the sulfidation state TiS1.5, leading to the formation of Ti3+ ions and sulfur anion vacancies. Moreover, HDS reaction mechanisms on sulfided TiO2 catalysts under the reaction conditions were elucidated by a 35S radioisotope tracer method using 35S-labeled dibenzothiophene (DBT). The results showed that less labile sulfur was detected on the sulfided TiO2 catalysts, suggesting that the HDS mechanism on TiO2 catalysts was very different from that on Mo-based catalysts.

Methods of Activating Catalysts for Hydrodesulfurization of Light Gas Oil. (Part 1). Catalytic Activity of CoMo/Al2O3 Catalyst Presulfided with Polysulfides for Hydrodesulfurization of Dibenzothiophene.

The organic sulfur compound bis-(1, 1, 3, 3-tetramethylbutyl)-polysulfide was investigated as a novel sulfiding agent for hydrodesulfurization (HDS) catalyst by evaluating the conversion of dibenzothiophene (DBT) on a commercial Co-Mo/Al2O3 catalyst. The catalyst presulfided using the polysulfide in situ showed the same or higher activity than those using the conventional sulfiding agents dimethyldisulfide (DMDS) and CS2. The catalytic activity for HDS and hydrogenation depended remarkably on the presulfiding procedure such as type of sulfiding agent, temperature program in the presulfiding procedure, and in situ or ex situ method. The 35S radioisotope tracer method was used to elucidate the effect of various sulfiding operation parameters on sulfur behavior on the sulfided catalyst in the HDS reaction of DBT. The effects of sulfiding agent and temperature program on the catalytic activity mainly originate from differences in the amount of labile sulfur formed in the different sulfiding processes.