Quasi-local energy and microcanonical entropy in two-dimensional nearly de Sitter gravity

We study the semi-classical thermodynamics of two-dimensional de Sitter space ($\text{dS}_{2}$) in Jackiw-Teitelboim (JT) gravity coupled to conformal matter. We extend the quasi-local formalism of Brown and York to $\text{dS}_{2}$, where a timelike boundary is introduced in the static patch to uniquely define conserved charges, including quasi-local energy. The boundary divides the static patch into two systems, a cosmological system and a black hole system, the former being unstable under thermal fluctuations while the latter is stable. A semi-classical quasi-local first law is derived, where the Gibbons--Hawking entropy is replaced by the generalized entropy. In the microcanonical ensemble the generalized entropy is stationary. Further, we show the on-shell Euclidean microcanonical action of a causal diamond in semi-classical JT gravity equals minus the generalized entropy of the diamond, hence extremization of the entropy follows from minimizing the action. Thus, we provide a first principles derivation of the island rule for $U(1)$ symmetric $\text{dS}_{2}$ backgrounds, without invoking the replica trick. We discuss the implications of our findings for static patch de Sitter holography.Comment: 48 pages + 4 appendices, 13 figure

On Scattering of Electromagnetic Waves by a Wormhole

We consider scattering of a plane electromagnetic wave by a wormhole. It is found that the scattered wave is partially depolarized and has a specific interference picture depending on parameters of the wormhole and the distance to the observer. It is proposed that such features can be important in the direct search of wormholes

Surface water sanitation and biomass production in a large constructed wetland in the Netherlands

In Western-Europe, agricultural practices have contributed to environmental problems such as eutrophication of surface and ground water, flooding, drought and desiccation of surrounding natural habitats. Solutions that reduce the impact of these problems are urgently needed. Common reed (Phragmites australis) is capable of sanitizing surface water and may function as green energy source because of its high productivity. Here, the results of an experiment in a constructed wetland in the Netherlands are presented where two different sanitation treatments were compared. Depending on the residence time and volume per unit area, reed is capable to reduce the total amount of nitrogen in the water with average efficiencies from 32 to 47% and the total amount of phosphorous with 27–45%. Although biomass production still varies largely between different parts of the constructed wetland, a rapid increase in biomass was observed since planting. Constructed wetlands with reed provide opportunities to improve water quality and reed produces enough biomass to serve as green energy source. Moreover, these wetlands also function as a flood water reservoir and are possibly advantageous for biodiversity. The optimal moment of reed harvesting depends on the goal of the owner. This moment should be chosen wisely, as it may have consequences for reed filter regeneration, biomass production, biodiversity, methane emission and water sanitation efficiency

The fate of phonons in freely expanding Bose-Einstein condensates

Phonon-like excitations can be imprinted into a trapped Bose-Einstein condensate of cold atoms using light scattering. If the condensate is suddenly let to freely expand, the initial phonons lose their collective character by transferring their energy and momentum to the motion of individual atoms. The basic mechanisms of this evaporation process are investigated by using the Gross-Pitaevskii theory and dynamically rescaled Bogoliubov equations. Different regimes of evaporation are shown to occur depending on the phonon wavelength. Distinctive signatures of the evaporated phonons are visible in the density distribution of the expanded gas, thus providing a new type of spectroscopy of Bogoliubov excitations.Comment: 13 pages, 16 figure

Rapid sulfation of 3,3',5'-triiodothyronine in native Xenopus laevis oocytes

Sulfation is an important metabolic pathway facilitating the degradation of thyroid hormone by the type I iodothyronine deiodinase. Different human and rat tissues contain cytoplasmic sulfotransferases that show a substrate preference for 3,3'-diiodothyronine (3,3'-T2) > T3 > rT3 > T4. During investigation of the expression of plasma membrane transporters for thyroid hormone by injection of rat liver RNA in Xenopus laevis oocytes, we found uptake and metabolism of iodothyronines by native oocytes. Groups of 10 oocytes were incubated for 20 h at 18 C in 0.1 ml medium containing 500,000 cpm (1-5 nM) [125I]T4, [125I]T3, [125I]rT3, or [125I]3,3'-T2. In addition, cytosol prepared from oocytes was tested for iodothyronine sulfotransferase activity by incubation of 1 mg cytosolic protein/ml for 30 min at 21 C with 1 microM [125I]T4, [125I]T3, [125I]rT3, or [125I]3,3'-T2 and 50 microM 3'-phosphoadenosine-5'-phosphosulfate. Incubation media, oocyte extracts, and assay mixtures were analyzed by Sephadex LH-20 chromatography for production of conjugates and iodide. After 20-h incubation, the percentage of added radioactivity present as conjugates in the media and oocytes amounted to 0.9 +/- 0.2 and 1.0 +/- 0.1 for T4, less than 0.1 and less than 0.1 for T3, 32.5 +/- 0.4 and 29.3 +/- 0.2 for rT3, and 3.8 +/- 0.3 and 2.3 +/- 0.2 for 3,3'-T2, respectively (mean +/- SEM; n = 3). The conjugate produced from rT3 was identified as rT3 sulfate, as it was hydrolyzed by acid treatment. After injection of oocytes with copy RNA coding for rat type I iodothyronine deiodinase, we found an increase in iodide production from rT3 from 2.3% (water-injected oocytes) to 46.2% accompanied by a reciprocal decrease in rT3 sulfate accumulation from 53.7% to 7.1%. After 30-min incubation with cytosol and 3'-phosphoadenosine-5'-phosphosulfate, sulfate formation amounted to 1.8% for T4, less than 0.1% for T3, 77.9% for rT3, and 2.9% for 3,3'-T2. These results show that rT3 is rapidly metabolized in native oocytes by sulfation. The substrate preference of the sulfotransferase activity in oocytes is rT3 >> 3,3'-T2 > T4 > T3. The physiological significance of the high activity for rT3 sulfation in X. laevis oocytes remains to be established

Plasma membrane transport of thyroid hormones and its role in thyroid hormone metabolism and bioavailability

Although it was originally believed that thyroid hormones enter target cells by passive diffusion, it is now clear that cellular uptake is effected by carrier-mediated processes. Two stereospecific binding sites for each T4 and T3 have been detected in c

Thyroid hormone transport by the heterodimeric human system L amino acid transporter

Transport of thyroid hormone across the cell membrane is required for thyroid hormone action and metabolism. We have investigated the possible transport of iodothyronines by the human system L amino acid transporter, a protein consisting of the human 4F2 heavy chain and the human LAT1 light chain. Xenopus oocytes were injected with the cRNAs coding for human 4F2 heavy chain and/or human LAT1 light chain, and after 2 d were incubated at 25 C with 0.01-10 microM [(125)I]T(4), [(125)I]T(3), [(125)I]rT(3), or [(125)I]3,3'-diiodothyronine or with 10-100 microM [(3)H]arginine, [(3)H]leucine, [(3)H]phenylalanine, [(3)H]tyrosine, or [(3)H]tryptophan. Injection of human 4F2 heavy chain cRNA alone stimulated the uptake of leucine and arginine due to dimerization of human 4F2 heavy chain with an endogenous Xenopus light chain, but did not affect the uptake of other ligands. Injection of human LAT1 light chain cRNA alone did not stimulate the uptake of any ligand. Coinjection of cRNAs for human 4F2 heavy chain and human LAT1 light chain stimulated the uptake of phenylalanine > tyrosine > leucine > tryptophan (100 microM) and of 3,3'-diiodothyronine > rT(3) approximately T(3) > T(4) (10 nM), which in all cases was Na(+) independent. Saturation analysis provided apparent Michaelis constant (K(m)) values of 7.9 microM for T(4), 0.8 microM for T(3), 12.5 microM for rT(3), 7.9 microM for 3,3'-diiodothyronine, 46 microM for leucine, and 19 microM for tryptophan. Uptake of leucine, tyrosine, and tryptophan (10 microM) was inhibited by the different iodothyronines (10 microM), in particular T(3). Vice versa, uptake of 0.1 microM T(3) was almost completely blocked by coincubation with 100 microM leucine, tryptophan, tyrosine, or phenylalanine. Our results demonstrate stereospecific Na(+)-independent transport of iodothyronines by the human heterodimeric system L amino acid transporter

Iodine-131 labelled octreotide: Not an option for somatostatin receptor therapy

Gamma-emitting radiopeptides are useful for scintigraphy of tumours on the basis of receptor binding. Likewise, β-emitting radiopeptides may be used in radionuclide therapy of such tumours. As iodine-131 suggested to be suitable for this purpose, experiments were performed using three somatostatin analogues, in which the effects of coupling of a therapeutic dose of 131I to such peptides were investigated. This study deals with the radioiodination of very small amounts of peptide on a therapeutic scale, the required purification procedures after radioiodination, and the influence of high beta fluxes from 131I. On a peptide during radioiodination and purification. Based on the regularly used therapeutic doses of 131I in cancer treatment and our previous experience with [111In-DTPA-D-Phe1]-octreotide, it was assumed that a minimal effective therapeutic dose of 3.7 GBq 131I has to be coupled to a maximum of ≃ 100 μg peptide, representing only a slight excess of peptide over 131I. This contrasts with non-peptide radiopharmaceuticals in which high compound to radionuclide ratios are usually used. Labelling at low peptide to radionuclide ratios (low labelling yields) results in the formation of di-iodinated compounds, whereas at high peptide to radionuclide ratios (high labelling yields) mono-iodinated products of low specific activity are formed. Thus, after radioiodination the desired mono-iodinated peptide has to be separated from unreacted iodide, and from di-iodinated and unreacted peptide, as both compounds compete for the receptors. Possible radiolysis of the peptide during labelling and separation steps were investigated by irradiating 30 μg unlabelled peptide with 370 MBq 131I in a small volume. The peptide composition of the incubation mixtures was investigated by high-performance liquid chromatography after irradiation for 30 min to 24 h. The results showed that the peptide was degraded with a half-life of less than 1 h. During the preparation of a real therapeutic dose (at much higher β-flux) the peptide will be degraded even faster during the various steps required. In conclusion, intact mono-iodinated 131I-labelled somatostatin analogues for peptide receptor therapy will be difficult to obtain

Expression of rat liver cell membrane transporters for thyroid hormone in Xenopus laevis oocytes

The present study was conducted to explore the possible use of Xenopus laevis oocytes for the expression cloning of cell membrane transporters for iodothyronines. Injection of stage V-VI X. laevis oocytes with 23 ng Wistar rat liver polyadenylated RNA (mRNA) resulted after 3-4 days in a highly significant increase in [125I]T3 (5 nM) uptake from 6.4 +/- 0.8 fmol/oocyte x h in water-injected oocytes to 9.2 +/- 0.65 fmol/oocyte x h (mean +/- SEM; n = 19). In contrast, [125I]T4 (4 nM) uptake was not significantly stimulated by injection of total liver mRNA. T3 uptake induced by liver mRNA was significantly inhibited by replacement of Na+ in the incubation medium by choline+ or by simultaneous incubation with 1 microM unlabeled T3. In contrast, T3 uptake by water-injected oocytes was not Na+ dependent. Fractionation of liver mRNA on a 6-20% sucrose gradient showed that maximal stimulation of T3 uptake was obtained with mRNA of 0.8-2.1 kilobases (kb). In contrast to unfractionated mRNA, the 0.7- to 2.1-kb fraction also significantly stimulated transport of T4, and it was found to induce uptake of T3 sulfate (T3S). Because T3S is a good substrate for type I deiodinase (D1), 2.3 ng rat D1 complementary RNA (cRNA) were injected either alone or together with 23 ng of the 0.8- to 2.1-kb fraction of rat liver mRNA. Compared with water-injected oocytes, injection of D1 cRNA alone did not stimulate uptake of [125I]T3S (1.25 nM). T3S uptake in liver mRNA and D1 cRNA-injected oocytes was similar to that in oocytes injected with mRNA alone, showing that transport of T3S is independent of the metabolic capacity of the oocyte. Furthermore, coinjection of liver mRNA and D1 cRNA strongly increased the production of 125I-, showing that the T3S taken up by the oocyte is indeed transported to the cell interior. In conclusion, injection of rat liver mRNA into X. laevis oocytes resulted in a stimulation of saturable, Na+-dependent T4, T3 and T3S transport, indicating that rat liver contains mRNA(s) coding for plasma membrane transporters for these iodothyronine derivatives