Deep modeling of plasma and neutral fluctuations from gas puff turbulence imaging.

The role of turbulence in setting boundary plasma conditions is presently a key uncertainty in projecting to fusion energy reactors. To robustly diagnose edge turbulence, we develop and demonstrate a technique to translate brightness measurements of HeI line radiation into local plasma fluctuations via a novel integrated deep learning framework that combines neutral transport physics and collisional radiative theory for the 33D - 23P transition in atomic helium with unbounded correlation constraints between the electron density and temperature. The tenets for experimental validity are reviewed, illustrating that this turbulence analysis for ionized gases is transferable to both magnetized and unmagnetized environments with arbitrary geometries. Based on fast camera data on the Alcator C-Mod tokamak, we present the first two-dimensional time-dependent experimental measurements of the turbulent electron density, electron temperature, and neutral density, revealing shadowing effects in a fusion plasma using a single spectral line.

Association of glucose metabolism and blood pressure during pregnancy with subsequent maternal blood pressure.

The goal of this study was to examine associations of measures of maternal glucose metabolism and blood pressure during pregnancy with blood pressure at follow-up in the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) cohort. The HAPO Follow-Up Study included 4747 women who had a 75-g oral glucose tolerance test (OGTT) at ~28 weeks' gestation. Of these, 4572 women who did not have chronic hypertension during their pregnancy or other excluding factors, had blood pressure evaluation 10-14 years after the birth of their HAPO child. Primary outcomes were systolic blood pressure (SBP), diastolic blood pressure (DBP), and hypertension (SBP ≥ 140 and/or DBP ≥ 90 or treatment for hypertension) at follow-up. Blood pressure during pregnancy was associated with all blood pressure outcomes at follow-up independent of glucose and insulin sensitivity during pregnancy. The sum of glucose z-scores was associated with blood pressure outcomes at follow-up but associations were attenuated in models that included pregnancy blood pressure measures. Associations with SBP were significant in adjusted models, while associations with DBP and hypertension were not. Insulin sensitivity during pregnancy was associated with all blood pressure outcomes at follow-up, and although attenuated after adjustments, remained statistically significant (hypertension OR 0.79, 95%CI 0.68-0.92; SBP beta -0.91, 95% CI -1.34 to -0.49; DBP beta -0.50, 95% CI -0.81 to -0.19). In conclusion, maternal glucose values at the pregnancy OGTT were not independently associated with maternal blood pressure outcomes 10-14 years postpartum; however, insulin sensitivity during pregnancy was associated independently of blood pressure, BMI, and other covariates measured during pregnancy.

First application of a digital mirror Langmuir probe for real-time plasma diagnosis.

For the first time, a digital Mirror Langmuir Probe (MLP) has successfully sampled plasma temperature, ion saturation current, and floating potential together on a single probe tip in real time in a radio-frequency driven helicon linear plasma device. This is accomplished by feedback control of the bias sweep to ensure a good fit to I-V characteristics with a high frequency, high power digital amplifier, and field-programmable gate array controller. Measurements taken by the MLP were validated by a low speed I-V characteristic manually collected during static plasma conditions. Plasma fluctuations, induced by varying the axial magnetic field (f̃ = 10 Hz), were also successfully monitored with the MLP. Further refinement of the digital MLP pushes it toward a turn-key system that minimizes the time to deployment and lessens the learning curve, positioning the digital MLP as a capable diagnostic for the study of low radio-frequency plasma physics. These demonstrations bolster confidence in fielding such digital MLP diagnostics in magnetic confinement experiments with high spatial and adequate temporal resolution, such as edge plasma, scrape-off layer, and divertor probes.

The digital mirror Langmuir probe: Field programmable gate array implementation of real-time Langmuir probe biasing.

High bandwidth, high spatial resolution measurements of electron temperature, density, and plasma potential are valuable for resolving turbulence in the boundary plasma of tokamaks. While conventional Langmuir probes can provide such measurements, either their temporal or spatial resolution is limited: the former by the sweep rate necessary for obtaining I-V characteristics and the latter by the need to use multiple electrodes, as is the case in triple and double probe configurations. The Mirror Langmuir Probe (MLP) bias technique overcomes these limitations by rapidly switching the voltage on a single electrode cycling between three bias states, each dynamically optimized for the local plasma conditions. The MLP system on Alcator C-Mod used analog circuitry to perform this function, measuring Te, VF, and Isat at 1.1 MSPS. Recently, a new prototype digital MLP controller has been implemented on a Red Pitaya Field Programmable Gate Array (FPGA) board which reproduces the functionality of the original controller and performs all data acquisition. There is also the potential to provide the plasma parameters externally for use with feedback control systems. The use of FPGA technology means the system is readily customizable at a fraction of the development time and implementation cost. A second Red Pitaya was used to test the MLP by simulating the current response of a physical probe using C-Mod experimental measurements. This project is available as a git repository to facilitate extensibility (e.g., real-time control outputs and more voltage states) and scalability through collaboration.

Density functional theory calculations for magnetic properties of Co3W systems.

Cheaper permanent magnetic nanostructures with magnetic properties equivalent to those of noble-metal or rare-earth nanomagnets have been experimentally developed for their potential applications in ultrahigh storage densities in magnetic memory. To date, their intrinsic magnetic properties are not well understood under the micro-level of local atomic arrangements and electronic structures. In this work, we performed theoretical investigations on the Co3W bulk, the clean surface, nanoclusters, and the Co|Co3W bilayers and superlattices for their geometrical structures, magnetic moments, and magnetic anisotropy energies (MAEs). We found that the Co3W nanostructures we constructed are stable and have the local minima in the energetic landscape, whose stabilities increase with increasing proportion of W and cluster size. The Co and W atoms in clusters are antiferromagnetically coupled, and their local magnetic moments decrease with increasing proportion of W. The breakdown of the Hund's third rule in W atoms observed in experiment can be interpreted as the competition between the intra-atomic spin-orbit coupling in W atoms and interatomic Co-W hybridizations. The highest MAE of about a few tens of meV is obtained in small cluster sizes, whereas it is an order of magnitude reduction in large cluster sizes. The magnetic systems of Co3W clean surface, Co|Co3W bilayer and superlattice can present large MAEs, and their easy-axes of magnetization are perpendicular to the (001) surface. Our calculated MAEs are of the same order of magnitude as that of the experimental measurements, and the electronic origin is revealed through the second-order perturbation method.

The flush-mounted rail Langmuir probe array designed for the Alcator C-Mod vertical target plate divertor.

An array of flush-mounted and toroidally elongated Langmuir probes (henceforth called rail probes) have been specifically designed for the Alcator C-Mod's vertical target plate divertor and operated over multiple campaigns. The "flush" geometry enables the tungsten electrodes to survive high heat flux conditions in which traditional "proud" tungsten electrodes suffer damage from melting. The toroidally elongated rail-like geometry reduces the influence of sheath expansion, which is an important effect to consider in the design and interpretation of flush-mounted Langmuir probes. The new rail probes successfully operated during C-Mod's FY2015 and FY2016 experimental campaigns with no evidence of damage, despite being regularly subjected to heat flux densities parallel to the magnetic field exceeding ∼1 GW m-2 for short periods of time. A comparison between rail and proud probe data indicates that sheath expansion effects were successfully mitigated by the rail design, extending the use of these Langmuir probes to incident magnetic field line angles as low as 0.5°.

[Comparison of the NoSAS score with four different questionnaires as screening tools for obstructive sleep apnea-hypopnea syndrome].

Objective: To evaluate the clinical utility of the NoSAS score in the screening of patients with obstructive sleep apnea-hypopnea syndrome(OSAHS), and to compare the performance of the NoSAS score with other tools including Epworth Sleepiness Scale(ESS), STOP, STOP-Bang(SBQ) and Berlin questionnaires. Methods: A total of 444 consecutive patients(328 males and 116 females) with suspected OSAHS who underwent an overnight polysomnography(PSG) were recruited into this study. Five questionnaires including the NoSAS score, ESS, STOP, SBQ and Berlin were completed. Based on the severity of OSAHS which was determined by apnea-hypopnea index(AHI), the patients were classified into 4 groups: normal(<5 events/h), mild(5-15 events/h), moderate(15-30 events/h) and, severe (≥30 events/h) OSA.Sensitivity, specificity, positive predictive values, negative predictive values and the area under the receiver operating characteristics curve of 5 questionnaires were calculated. Results: With AHI≥5 events/h as the standard diagnosis of OSAHS, the NoSAS score and SBQ questionnaire showed a moderate performance, with the NoSAS score having the largest area under the ROC curve(0.753, P<0.001), followed by the SBQ questionnaire (0.727, P<0.001). The performance of the ESS, Berlin, and the STOP questionnaire was not high. Using mild moderate-severe(≥5 events/h), moderate-severe(≥15 events/h), and severe(≥30 events/h)OSAHS as cutoffs, NoSAS had the highest specificity and positive predictive values(80.2% and 88%, 72% and 69.8%, 66.3% and 50.5%), and the sensitivity and negative predictive values were (51.5% and 36.9%, 56.5% and 59.1%, 66.3% and 74.2%) .SBQ had the highest sensitivity and the negative predictive values(80.2% and 88%, 72% and 69.8%, 66.3% and 50.5%), and the specific and positive predictive values were (45.7% and 81.0%, 39.1% and 61.9%, 34.8% and 44.4%). The NoSAS score ≥ 7 had higher sensitivity and negative predictive value(75.0% and 47.1%, 78.1% and 66.5%, 82.7% and 81.9%)than the NoSAS socre ≥ 8. With AHI≥5 events/h as the standard diagnosis of OSAHS, the NoSAS score and the SBQ questionnaire had a higher accuracy than the other 3 questionnaires as screening questionnaires for diagnosing OSAHS, and the value of DOR were 4.298 and 3.758 respectively. Conclusions: The NoSAS score and the SBQ questionnaire have a moderate performance in diagnosing OSAHS. The NoSAS score is a new screening tool, and it is similar to the SBQ questionnaire, being also simple and effective. While the SBQ questionnaire is more widely used, it is necessary to further evaluate the diagnostic value of NoSAS score.

Magnetic moment and magnetic anisotropy of Ge3Mn5 thinfilms on Ge(111) substrate: A density functional study.

Magnetism and magnetic anisotropy energy (MAE) of the Ge3Mn5 bulk, free-standing surface, and Ge3Mn5(001)|Ge(111) thinfilms and superlattice have been systemically investigated by using the relativistic first-principles electronic structure calculations. For Ge3Mn5 adlayers on Ge(111) substrates within Mn1 termination, the direction of magnetization undergoes a transition from in-plane at 1 monolayer (ML) thickness (MAE = -0.50 meV/ML) to out-of-plane beginning at 3 ML thickness (nearly invariant MAE = 0.16 meV/ML). The surficial/interfacial MAE is extracted to be 1.23/-0.54 meV for Mn1-termination; the corresponding value is 0.19/1.03 meV for Mn2/Ge-termination; the interior MAE is averaged to be 0.09 meV per ML. For various Ge3Mn5 systems, the in-plane lattice expansion and/or interlayer distance contraction would enhance the out-of-plane MAE. Our theoretical magnetic moments and MAEs fit well with the experimental measurements. Finally, the origination of MAE is elucidated under the framework of second-order perturbation with the electronic structure analyses.

Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak.

A new servomotor drive system has been developed for the horizontal reciprocating probe on the Alcator C-Mod tokamak. Real-time measurements of plasma temperature and density-through use of a mirror Langmuir probe bias system-combined with a commercial linear servomotor and controller enable self-adaptive position control. Probe surface temperature and its rate of change are computed in real time and used to control probe insertion depth. It is found that a universal trigger threshold can be defined in terms of these two parameters; if the probe is triggered to retract when crossing the trigger threshold, it will reach the same ultimate surface temperature, independent of velocity, acceleration, or scrape-off layer heat flux scale length. In addition to controlling the probe motion, the controller is used to monitor and control all aspects of the integrated probe drive system.

[Severe obstructive sleep apnea-hypopnea syndrome with dilated cardiomyopathy leading to pulmonary hypertension: case report and literature review].

Objective: To study the relationship between dilated cardiomyopathy and obstructive sleep apnea-hypopnea syndrome (OSAHS) and to evaluate the curative effects of continuous positive airway pressure (CPAP) in OSAHS complicated with dilated cardiomyopathy. Methods: We reported one case with the symptom of exertional dyspnea for 1 year and aggravating for 1 month. The patient finally was diagnosed with severe OSAHS complicated with dilated cardiomyopathy leading to pulmonary hypertension. A systematic literature review was performed for similar published cases in Pubmed, Wanfang and CNKI database, using the keywords (obstructive sleep apnea) OR(OSA) OR(OSAHS) AND(dilated cardiomyopathy OR DCM)from January 1990 to May 2016. Results: Our patient had no significant improvement after receiving initial treatments, including reducing cardiac preload, improving myocardial metabolism, increasing myocardial contractility, and anticoagulants. After the patient was diagnosed as having severe OSAHS by polysomnography(PSG) and treated with CPAP, his symptoms improved remarkably. The enlarged heart became smaller and the patient had no repeated dyspnea at follow-up examination. By literature review, we found 4 English original articles and 6 Chinese articles (1 review article, 1 expert note, 1 original article and 3 case reports) on OSAHS complicated by DCM.Four Chinese and 1 English articles reported that the symptoms and parameters of OSAHS with DCM was improved remarkably after treatment with CPAP. Conclusion: For patients with dilated cardiomyopathy which fails to conventional therapy, especially those accompanied by obesity, snoring, daytime sleepiness, morning dry mouth and other related symptoms, PSG should be carried out. Early CPAP therapy could improve symptoms and prognosis of OSAHS associated with DCM.

Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak.

Mitigation of the intense heat flux to the divertor is one of the outstanding problems in fusion energy. One technique that has shown promise is impurity seeding, i.e., the injection of low-Z gaseous impurities (typically N2 or Ne) to radiate and dissipate the power before it arrives to the divertor target plate. To this end, the Alcator C-Mod team has created a first-of-its-kind feedback system to control the injection of seed gas based on real-time surface heat flux measurements. Surface thermocouples provide real-time measurements of the surface temperature response to the plasma heat flux. The surface temperature measurements are inputted into an analog computer that "solves" the 1-D heat transport equation to deliver accurate, real-time signals of the surface heat flux. The surface heat flux signals are sent to the C-Mod digital plasma control system, which uses a proportional-integral-derivative (PID) algorithm to control the duty cycle demand to a pulse width modulated piezo valve, which in turn controls the injection of gas into the private flux region of the C-Mod divertor. This paper presents the design and implementation of this new feedback system as well as initial results using it to control divertor heat flux.

Emergence of antiferromagnetic ordering in Tbn (n = 2-33) clusters.

Using the density functional theory (DFT) under both frameworks of the local density approximation (LDA) and the generalized gradient approximation (GGA), we show that the anomalous magnetic moment of Tbn (n = 2-20, 22, 33) clusters found in recent experiment [J. Appl. Phys. 2010, 107, 09B526] is due to the antiferromagnetic or ferromagnetic couplings between Tb atoms in clusters. The local spin magnetic moment of Tb atoms is in the range 5.1-5.7 µ(B), which is faintly influenced by the cluster sizes, geometrical structures, and spin arrangements. Emphasis is made on the Tb13 cluster to eliminate the large magnetic discrepancy between the experiment and calculation. Geometrical evolution shows that the square-antiprism motif with one centered atom is competitive with the icosahedral motif for small Tb clusters n = 9-12, whereas the close packed icosahedral growth is clearly favored for large clusters n = 13-20, 22, 33. The clusters containing 4, 7, 10, 13, and 19 atoms are found to be more stable than their neighboring sizes, in agreement with the early mass spectral measurements. The electronic properties including the HOMO-LUMO energy gaps, ionization potentials, electron affinities, and electric dipole moments are calculated, and more importantly, the variational trends of the magnetic moment and electric dipole moment qualitatively fit well with the experimental observations.

Monoxides of small terbium clusters: a density functional theory investigation.

To investigate the effect of oxygen atom on the geometrical structures, electronic, and magnetic properties of small terbium clusters, we carried out the first-principles calculations on TbnO (n = 1-14) clusters. The capping of an oxygen atom on one trigonal-facet of Tbn structures is always favored energetically, which can significantly improve the structural stability. The far-infrared vibrational spectroscopies are found to be different from those of corresponding bare clusters, providing a distinct signal to detect the characteristic structures of TbnO clusters. The primary effect of oxygen atom on magnetic properties is to change the magnetic orderings among Tb atoms and to reduce small of local magnetic moments of the O-coordinated Tb atoms, both of which serve as the key reasons for the experimental magnetic evolution of an oscillating behavior. These calculations are consistent with, and help to account for, the experimentally observed magnetic properties of monoxide TbnO clusters [C. N. Van Dijk et al., J. Appl. Phys. 107, 09B526 (2010)].

Electronic structural and magnetic properties of Mn5Ge3 clusters.

Theoretical understanding of the stability, ferromagnetism, and spin polarization of Mn5Ge3 clusters has been performed by using the density functional theory with generalized gradient approximation for exchange and correlation. The magnetic moments and magnetic anisotropy energy (MAE) have been calculated for both bulk and clusters, and the enhanced magnetic moment as well as the enlarged MAE have been identified in clusters. The most attractive achievement is that Mn5Ge3 clusters show a fine half-metallic character with large energy scales. The present results may have important implications for potential applications of small Mn5Ge3 clusters as both emerging spintronics and next-generation data-storage technologies.

The spin and orbital moment of Fe(n) (n = 2-20) clusters.

Complementary to the recent experimental finding that the orbital magnetic moment is strongly quenched in small Fe clusters [M. Niemeyer, K. Hirsch, V. Zamudio-Bayer, A. Langenberg, M. Vogel, M. Kossick, C. Ebrecht, K. Egashira, A. Terasaki, T. Möller, B. v. Issendorff, and J. T. Lau, Phys. Rev. Lett. 108, 057201 (2012)], we provide the theoretical understanding of the spin and orbital moments as well as the electronic properties of neutral and cation Fen clusters (n = 2-20) by taking into account the effects of strong electronic correlation, spin-orbit coupling, and noncollinearity of inter-atomic magnetization. The generalized gradient approximation (GGA)+U method is used and its effluence on the magnetic moment is emphasized. We find that without inclusion of the Coulomb interaction U, the spin (orbital) moments have an average value between 2.69 and 3.50 µB/atom (0.04 and 0.08 µB/atom). With inclusion of U, the magnetic value is between 2.75 and 3.80 µB/atom (0.10 and 0.30 µB/atom), which provide an excellent agreement with the experimental measurements. Our results confirm that the spin moments are less quenched, while the orbital moments are strongly quenched in small Fe clusters. Both GGA and GGA+U functionals always yield collinear magnetic ground-state solutions for the fully relaxed Fe structures. Geometrical evolution, as a function of cluster size, illustrates that the icosahedral morphology competes with the hexagonal-antiprism morphology for large Fe clusters. In addition, the calculated trends of ionization potentials, electron affinities, fragment energies, and polarizabilities generally agree with respective experimental observations.

Structural and magnetic properties of small 4d transition metal clusters: role of spin-orbit coupling.

The spin and orbital magnetic moments, as well as the magnetic anisotropy energy (MAE), of small 4d transition metal (TM) clusters are systematically studied by using the spin-orbit coupling (SOC) implementation of the density-functional theory (DFT). The effects of spin-orbit interactions on geometrical structures and spin moments are too weak to alternate relative stabilities of different low-lying isomers. Remarkable orbital contributions to cluster magnetic moments are identified in Ru, Rh, and Pd clusters, in contrast to immediate quenching of the atomic orbital moment at the dimer size in other elemental clusters. More interestingly, there is always collinearity between total spin and orbital moments (antiferromagnetic or ferromagnetic coupling depends on the constituent atoms whose 4d subshell is less or more than half-filled). The clusters preserve the validity of Hund's rules for the sign of orbital moment. The calculations on MAEs reveal the complicated changes of the easy axes in different structures. The perturbation theory and the first-principles calculations are compared to emphasize how MAEs evolve with cluster size. Finally, large orbital moments combined with strong spin-orbit coupling are proposed to account for large MAEs in Ru, Rh, and Pd clusters.

Combining transfer of TTF-1 and Pax-8 gene: a potential strategy to promote radioiodine therapy of thyroid carcinoma.

Cotransfer of thyroid-specific transcription factor (TTF)-1 and Pax-8 gene to tumor cells, resulting in the re-expression of iodide metabolism-associated proteins, such as sodium iodide symporter (NIS), thyroglobulin (Tg), thyroperoxidase (TPO), offers the possibility of radioiodine therapy to non-iodide-concentrating tumor because the expression of iodide metabolism-associated proteins in thyroid are mediated by the thyroid transcription factor TTF-1 and Pax-8. The human TTF-1 and Pax-8 gene were transducted into the human thyroid carcinoma (K1 and F133) cells by the recombinant adenovirus, AdTTF-1 and AdPax-8. Re-expression of NIS mRNA and protein, but not TPO and Tg mRNA and protein, was detected in AdTTF-1-infected F133 cells, following with increasing radioiodine uptake (6.1-7.4 times), scarcely iodide organification and rapid iodide efflux (t(1/2) ≈ 8-min in vitro, t(1/2) ≈ 4.7-h in vivo). On contrast, all of the re-expression of NIS, TPO and Tg mRNA and proteins were detected in F133 cells coinfected with AdTTF-1 and AdPax-8. AdTTF-1- and AdPax-8-coinfected K1 and F133 cells could effectively accumulate radioiodine (6.6-7.5 times) and obviously retarded radioiodine retention (t(1/2) ≈ 25-30-min in vitro, t(1/2) ≈ 12-h in vivo) (P<0.05). Accordingly, the effect of radioiodine therapy of TTF-1 and Pax-8 cotransducted K1 and F133 cells (21-25% survival rate in vitro) was better than that of TTF-1-transducted cells (40% survival rate in vitro) (P<0.05). These results indicate that single TTF-1 gene transfer may have limited efficacy of radioiodine therapy because of rapid radioiodine efflux. The cotransduction of TTF-1 and Pax-8 gene, with resulting NIS-mediated radioiodine accumulation and TPO and Tg-mediated radioiodine organification and intracellular retention, may lead to effective radioiodine therapy of thyroid carcinoma.

Radioiodine therapy of thyroid carcinoma following Pax-8 gene transfer.

The thyroid transcription factor Pax-8 could bind with the promoter/enhancer of thyroid-specific genes such as thyroglobulin (Tg), thyroperoxidase (TPO) and sodium iodide symporter (NIS), and regulate the expression of these proteins in thyrocyte. Promoting iodide accumulation in tumor cells by re-expression of Pax-8 provides a possible strategy for radioiodine therapy of tumor. Therefore, we investigated the effect of Pax-8 gene transfer on radioiodine therapy of thyroid carcinoma. The human Pax-8 gene was transfected into the human thyroid carcinoma (K1 and F133) cells by the recombinant adenovirus vector. Although the NIS mRNA was not detected, the expression of mRNA and proteins of Tg and TPO in AdPax-8-infected F133 cells were activated by Pax-8. Iodide uptake in thyroid carcinoma cells was reactivated by Pax-8 (increasing 3.3-fold in K1 cells and 5.7-fold in F133 cells). Moreover, Pax-8 promoted iodide organification and the retention time of iodine in Pax-8-expressing cells apparently prolonged in vitro and in vivo (P<0.05). Pax-8-expressing thyroid carcinoma cells were selectively killed by radioiodine. The AdPax-8-infected tumors in vivo clearly visualized in scanning images at 12 h after administration of radioiodine. These results indicate that Pax-8 can promote iodide uptake, and specifically prolong the retention time of iodide in thyroid cancer in vitro and in vivo by promoting the expression of TPO and Tg proteins. Pax-8 gene transfection may lead to effective radioiodine therapy of tumor.

Iodine kinetics and dosimetry in the salivary glands during repeated courses of radioiodine therapy for thyroid cancer.

PURPOSE: The present study was conducted to investigate salivary iodine kinetics and dosimetry during repeated courses of radioiodine ((131)I) therapy for differentiated thyroid cancer (DTC). Such data could provide a better understanding of the mechanisms of (131)I induced salivary toxicity and help to develop appropriate methods to reduce this injury. METHODS: Seventy-eight consecutive DTC patients (mean age 45 ± 17 years, 60%, female) undergoing (131)I therapy for remnant ablation or metastatic tumors were prospectively recruited. Planar quantitative scintigraphy of head-neck images was serially acquired after administration of 2.9-7.4 GBq of (131)I to assess kinetics in the salivary glands of patients. Salivary absorbed doses were calculated based on the schema of Medical Internal Radiation Dosimetry. RESULTS: The maximum uptakes in percentage of administered (131)I activity per kilogram of gland tissue (%/kg) were 12.9% ± 6.5%/kg (range, 0.4%-37.3%/kg) and 12.3% ± 6.2%/kg (range, 0.4%-35.1%/kg) for the parotid and submandibular glands, respectively. Statistically significant correlations of maximum uptake versus cumulative activity (r = -0.74, P < 0.01, for the parotid glands; r = -0.71, P < 0.01, for the submandibular glands) and treatment cycle (P < 0.001, for both gland types) were found. The effective half-lives of (131)I in the parotid and submandibular glands were 9.3 ± 3.5 h (range, 1.5-19.8 h) and 8.6 ± 3.2 h (range, 0.8-18.0 h), respectively. A statistically significant correlation was observed between effective half-life with cumulative activity (r = 0.37, P < 0.01) and treatment cycle (P = 0.03) only for the parotid glands. The calculated absorbed doses were 0.20 ± 0.10 mGy/MBq (range, 0.01-0.92 mGy/MBq) and 0.25 ± 0.09 mGy/MBq (range, 0.01-1.52 mGy/MBq) for the parotid and submandibular glands, respectively. The photon contribution to the salivary absorbed dose was minimal in relation to the beta dose contribution. Photon-absorbed dose fractions of total absorbed dose were 4.9% ± 1.3% (range, 1.1%-8.7%) and 3.7% ± 2.5% (range, 0.8%-7.9%) for the parotid and submandibular glands, respectively. CONCLUSIONS: The iodine uptake of salivary glands is continuously reduced during the courses of therapy. The phenomenon of hyper-radiosensitivity may to some extent account for the occurrence of salivary gland hypofunction at very low radiation doses with low dose rates in (131)I therapy. On the other hand, failure to incorporate a nonuniform and preferential uptake by salivary gland ductal cells may result in underestimating the actual dose for the critical tissue. Other methods, including (124)I voxel-based dosimetry, are warranted to further investigate the (131)I-induced salivary gland toxicity.

Geometrical structure and spin order of Gd13 cluster.

The spin-polarized generalized gradient approximation to the density-functional theory has been used to determine the lowest energy structure, electronic structure, and magnetic property of Gd(13) cluster. Our results show that the ionic bonding is combined with the covalent characteristics in stabilizing the Gd cluster. The ferrimagnetic icosahedron is found to be the lowest energy configuration, in which the centered Gd atom couples antiferromagnetically with the rest Gd atoms surrounding it. No spin non-collinear evidence has been detected in our calculations. It is identified that the local magnetic moments of Gd atom are about 8 µ(B) regardless of geometrical structure. Finally, the comprehensive electronic structure analyses show that the indirect long-range magnetic coupling between the polarized 4f is mediated by the polarization of 5d, 6s, and 6p conduction electrons, which is the typical Ruderman-Kittel-Kasuya-Yosida interactions.