Room-Temperature Thermoelectric Performance of n-Type Multiphase Pseudobinary Bi2Te3-Bi2S3 Compounds: Synergic Effects of Phonon Scattering and Energy Filtering.

Bismuth telluride-based alloys possess the highest efficiencies for the low-temperature-range (<500 K) applications among thermoelectric materials. Despite significant advances in the efficiency of p-type Bi2Te3-based materials through engineering the electronic band structure by convergence of multiple bands, the n-type pair still suffers from poor efficiency due to a lower number of electron pockets near the conduction band edge than the valence band. To overcome the persistent low efficiency of n-type Bi2Te3-based materials, we have fabricated multiphase pseudobinary Bi2Te3-Bi2S3 compounds to take advantages of phonon scattering and energy filtering at interfaces, enhancing the efficiency of these materials. The energy barrier generated at the interface of the secondary phase of Bi14Te13S8 in the Bi2Te3 matrix resulted in a higher Seebeck coefficient and consequently a higher power factor in multiphase compounds than the single-phase alloys. This effect was combined with low thermal conductivity achieved through phonon scattering at the interfaces of finely structured multiphase compounds and resulted in a relatively high thermoelectric figure of merit of ∼0.7 over the 300-550 K temperature range for the multiphase sample of n-type Bi2Te2.75S0.25, double the efficiency of single-phase Bi2Te3. Our results inform an alternative alloy design to enhance the performance of thermoelectric materials.

Thermoelectric Performance of n-Type Magnetic Element Doped Bi2S3.

Thermoelectric technology offers great potential for converting waste heat into electrical energy and is an emission-free technique for solid-state cooling. Conventional high-performance thermoelectric materials such as Bi2Te3 and PbTe use rare or toxic elements. Sulfur is an inexpensive and nontoxic alternative to tellurium. However, achieving high efficiencies with Bi2S3 is challenging due to its high electrical resistivity that reduces its power factor. Here, we report Bi2S3 codoped with Cr and Cl to enhance its thermoelectric properties. An enhanced conductivity was achieved due to an increase in the carrier concentration by the substitution of S with Cl. High values of the Seebeck coefficients were obtained despite high carrier concentrations; this is attributed to an increase in the effective mass, resulting from the magnetic drag introduced by the magnetic Cr dopant. A peak power factor of 566 µW m-1 K-2 was obtained for a cast sample of Bi2-x/3Cr x/3S3-x Cl x with x = 0.01 at 320 K, as high as the highest values reported in the literature for sintered samples. These results support the success of codoping thermoelectric materials with isovalent magnetic and carrier concentration tuning elements to enhance the thermoelectric properties of eco-friendly materials.

Isfahan Thyroid Cohort Study (ITCS).

BACKGROUND: The Isfahan Thyroid Cohort Study (ITCS) is one of the few population-based epidemiological studies in Iran that investigates the prevalence and incidence of thyroid disorders including hypothyroidism, hyperthyroidism, goiter, nodule, and iodine status. METHODS: This cohort is located in Isfahan, Iran. The first phase was initiated in 2006 with 2523 participants (1275 males, 1248 females). The participants were selected using multi-stage cluster sampling from the general residents of Isfahan, Iran. The study had two phases (2006 and 2011) and its third stage is planned for 2020-2021. RESULTS: The prevalence of thyroid function states was euthyroid (89.3%, 95% CI: 88%-90%), overt hypothyroidism (2.8%, 95% CI: 2%‒3%), subclinical hypothyroidism (5.8%, 95% CI: 4%-6%), overt hyperthyroidism (0.8%, 95% CI: 0.4%‒1%), and subclinical hyperthyroidism (0.99%, 95% CI: 0.6%-1%). Hypothyroidism and hyperthyroidism were significantly associated with goiter. The incidence of thyroid dysfunction was reported as follows: overt hypothyroidism (2.7, 95% CI: 1.6-3.7), subclinical hypothyroidism (20.6, 95% CI: 18-23), overt hyperthyroidism (1.9, 95% CI: 1-2.7) and subclinical hyperthyroidism (2.7, 95% CI: 1.6-3.7) per 1000 (person-year). CONCLUSION: We assessed the prevalence and incidence of thyroid disorders in Isfahan in the first and second phase, respectively. We are conducting the third phase of the ITCS in order to study the associations between thyroid peroxidase antibody (TPOAb) level and environmental factors such as infection.

Recent Progress in Multiphase Thermoelectric Materials.

Thermoelectric materials, which directly convert thermal energy to electricity and vice versa, are considered a viable source of renewable energy. However, the enhancement of conversion efficiency in these materials is very challenging. Recently, multiphase thermoelectric materials have presented themselves as the most promising materials to achieve higher thermoelectric efficiencies than single-phase compounds. These materials provide higher degrees of freedom to design new compounds and adopt new approaches to enhance the electronic transport properties of thermoelectric materials. Here, we have summarised the current developments in multiphase thermoelectric materials, exploiting the beneficial effects of secondary phases, and reviewed the principal mechanisms explaining the enhanced conversion efficiency in these materials. This includes energy filtering, modulation doping, phonon scattering, and magnetic effects. This work assists researchers to design new high-performance thermoelectric materials by providing common concepts.

Prevalence and predictors of prediabetes and its coexistence with high blood pressure in first-degree relatives of patients with type 2 diabetes: A 9-year cohort study.

BACKGROUND: Prediabetes is strongly associated with high blood pressure; however, a little is known about prediabetes and high blood pressure comorbidity in the high-risk individuals. This is the first study in the world to assess the long-term effects of risk factors associated with high blood pressure and prediabetes comorbidity in the first-degree relatives (FDRs) of type 2 diabetes mellitus (T2DM) patients. MATERIALS AND METHODS: The longitudinal data obtained from 1388 nondiabetic FDRs of T2DM patients with at least two visits between 2003 and 2011. We used univariate and bivariate mixed-effects logistic regressions with a Bayesian approach to identify longitudinal predictors of high blood pressure and prediabetes separately and simultaneously. RESULTS: The baseline prevalence of high blood pressure, prediabetes, and the coexistence of both was 27.4%, 19.1%, and 29.8%, respectively. The risks of high blood pressure and prediabetes were increased by one-unit raise in the age (odds ratio [OR] of high blood pressure: 1.419 (95% credible intervals [CI], 1.077-1.877), prediabetes: 1.055 (95% CI: 1.040-1.068)) and one-unit raise in remnant-cholesterol (OR of high blood pressure: 1.093 (95%CI, 1.067-1.121), and prediabetes: 1.086 (95% CI, 1.043-1.119)). Obese participants were more likely to have high blood pressure (OR: 2.443 [95% CI, 1.978-3.031]) and prediabetes (OR: 1.399 [95% CI, 1.129-1.730]) than other participants. CONCLUSION: We have introduced remnant-cholesterol, along with obesity and age, as a significant predictor of prediabetes, high blood pressure, and the coexistence of both in the FDRs of diabetic patients. Obesity index and remnant-cholesterol showed the stronger effects on high blood pressure and prediabetes comorbidity than on each condition separately.

Diabetes and all-cause mortality, a 18-year follow-up study.

This study compared mortality rates and decline in life expectancy of Iranian patients with type 2 diabetes (T2DM) with the general population. A retrospective study of 2451 patients with T2DM was conducted in the Isfahan Endocrine and Metabolism Research Center, Iran, between 1992 and 2010. The mean (SD) of diabetes duration and median (Q1,Q3) of follow-up period were 15.5(8.0) and 8(5, 10) years. The main outcome was all-cause mortality. 732(29.87%) of patients died during the follow-up. Overall mortality rates (95%CI) per 1000 person-years in men and women were 56.3(52.0-62.1) and 27.3(24.5-30.4), respectively. The relative risks (95%CI) of all-cause mortality in males vs. females with T2DM aged 45-49, 50-54, 55-59, 60-64, 65-69, 70-74 were [3.02(1.49-6.11) vs. 2.09(0.96-4.57)], [4.05(2.73-6.01) vs. 2.29(1.52-3.45)], [4.13(3.26-5.24) vs. 1.70(1.23-2.35)], [2.42(1.90-3.07) vs. 1.82(1.46-2.27)], [2.36(2.02-2.76) vs. 1.49(1.25-1.78)] and [1.71(1.50-1.95) vs. 1.04(0.88-1.23)] times more than the general population, respectively. Men and women living with diabetes lost an average of 13.2(6.3) and 13.9(6.0) life-years from the year of diagnosis, respectively (p = 0.101). The estimated life-years lost were greater in younger patients and a gradual decline was observed with increasing the age at diagnosis. In conclusion, Iranians with diabetes had higher risk of death and lower life expectancy compared to the general population.

Thermoelectric Performance of Single-Phase Tellurium-Reduced Quaternary (PbTe)0.55(PbS)0.1(PbSe)0.35.

Lead chalcogenide quaternary systems have been shown to provide high thermoelectric (TE) efficiency superior to those of binary and ternary lead chalcogenides, arising from both altered electronic band structures and a reduction in lattice thermal conductivity. Here, we have synthesized single-phase samples of the quaternary compound (PbTe)0.55(PbS)0.1(PbSe)0.35 doped with Na and characterized their TE properties. We show that the dopant solubility is limited to 1 at. %. A very low lattice thermal conductivity of ∼0.6 W m-1 K-1 at 850 K is achieved at all dopant concentrations because of phonon scattering from point defects associated with solute atoms with high contrast atomic mass. As a result, a high TE figure of merit of approximately 1.5 is achieved at 823 K in heavily doped samples. Moreover, the figure of merit is greater than 1 over a wide temperature range above 675 K.

Cross-sectional and longitudinal assessments of risk factors associated with hypertension and moderately increased albuminuria comorbidity in patients with type 2 diabetes: a 9-year open cohort study.

BACKGROUND: Moderately increased albuminuria (MIA) is strongly associated with hypertension (HTN) in patients with type 2 diabetic mellitus (T2DM). However, the association between risk factors and coexisting HTN and MIA remains unassessed. OBJECTIVES: This study aimed to determine both cross-sectional and longitudinal associations of risk factors with HTN and MIA comorbidity in patients with T2DM. METHODS: A total of 1,600 patients with T2DM were examined at baseline and longitudinal data were obtained from 1,337 T2DM patients with at least 2 follow-up visits to assess the presence of HTN alone (yes/no), MIA alone (yes/no) and the coexistence of both (yes/no) in a 9-year open cohort study between 2004 and 2013. Bivariate mixed-effects logistic regression with a Bayesian approach was employed to evaluate associations of risk factors with HTN and MIA comorbidity in the longitudinal assessment. RESULTS: After adjustment for age and BMI, patients with uncontrolled plasma glucose, as a combined index of the glucose profile, were more likely to have HTN [odds ratio (OR): 1.73 with 95% Bayesian credible intervals (BCI) 1.29-2.20] and MIA [OR: 1.34 ( 95% BCI 1.13-1.62)]. The risks of having HTN and MIA were increased by a one-year raise in diabetes duration [with 0.89 (95% BCI 0.84-0.96) and 0.81 (95% BCI 0.73-0.92) ORs, respectively] and a one-unit increase in non-high-density lipoprotein-cholesterol (Non-HDL-C) [with 1.30 (95% BCI 1.23-1.34) and 1.24 (95% BCI 1.14-1.33) ORs, respectively]. CONCLUSIONS: T2DM patients with HTN, MIA, and the coexistence of both had uncontrolled plasma glucose, significantly higher Non-HDL-C, and shorter diabetes duration than the other T2DM patients. Duration of diabetes and uncontrolled plasma glucose index showed the stronger effects on HTN and MIA comorbidity than on each condition separately.

Thyroid-stimulating hormone (TSH) serum levels and risk of spontaneous abortion: A prospective population-based cohort study.

OBJECTIVE: Thyroid dysfunction, a common complication of pregnancy, is associated with adverse obstetric and neonatal consequences. This study aimed to determine the effect of TSH levels on early pregnancy outcome in a prospective population-based cohort study. DESIGN AND METHODS: The serum TSH, free thyroxine, free triiodothyronine, thyroid peroxidase antibody levels and urinary iodine concentration of 418 pregnant women in their first trimester of pregnancy were measured. According to the American Thyroid Association (ATA) and the local reference ranges for TSH, women were divided into two groups of 0.1-2.5, >2.5 mIU/L and 0.2-4.6, >4.6 mIU/L. The risk of spontaneous abortion (SA) was calculated for each group. RESULTS: Spontaneous abortion was detected in 7.2% (n = 30) of total 418 pregnancies. Women with TSH levels > 2.5 mIU/L had an increased risk of SA, compared to women with TSH levels of 0.1-2.5 mIU/L (relative risk [RR] 3.719, 95% confidence interval [CI]:1.713-8.074). The risk of SA was increased in women with TSH levels > 4.6 mIU/L (RR 5.939, 95% CI: 1.711-20.620). The rate of SA was increased by 78% for every unit increase in standard deviation of TSH concentration (RR 1.35, 95% CI: 1.09-1.70). The rate of miscarriages in the treated group by levothyroxine was 9.8% (n = 6) compared to 28.6% (n = 8) in the untreated group (P = 0.024). CONCLUSIONS: Our finding suggests that the upper limit for the TSH normal range should be redefined to <2.5 mIU/L during the first trimester of gestation. The local upper limit was 4.6 mIU/L, consistent with 4.0 mIU/L cut-off value recommended by the ATA.

Alendronate improves fasting plasma glucose and insulin sensitivity, and decreases insulin resistance in prediabetic osteopenic postmenopausal women: A randomized triple-blind clinical trial.

AIMS/INTRODUCTION: Postmenopausal women receive bisphosphonates for osteoporosis treatment. The effect of these medications on developing diabetes mellitus in prediabetic patients is yet to be investigated. We aimed to determine the effect of alendronate on plasma glucose, insulin indices of postmenopausal women with prediabetes and osteopenia. MATERIALS AND METHODS: The present triple-blind randomized controlled clinical trial included 60 postmenopausal women, aged 45-60 years. All patients were vitamin D sufficient. They were randomly enrolled in intervention (70 mg/week alendronate for 12 weeks) and control (placebo tablet per week for 12 weeks) groups. The morning 8-h fasting blood samples were collected at the baseline and follow-up visits to measure the fasting plasma glucose (mg/dL), insulin and hemoglobin A1c (HbA1c). Plasma glucose and insulin concentration were measured 30, 60 and 120 min after the glucose tolerance test. The Matsuda Index, homeostasis model assessment of insulin resistance, homeostasis model assessment of ß-cell function and the area under the curves of glucose and insulin were calculated. RESULTS: The mean (standard deviation) fasting plasma glucose (102.43 [1.46] mg/dL vs 94.23 [1.17] mg/dL, P = 0.001), 120-min insulin concentration (101.86 [15.70] mU/L vs 72.60 [11.36] mU/L, P = 0.026), HbA1c (5.60 [0.06]% vs 5.40 [0.05]%, P = 0.001), homeostasis model assessment of insulin resistance (3.57 [0.45] vs 2.62 [0.24], P = 0.021) and Matsuda Index (7.7 [0.41] vs 9.2 [0.4], P = 0.001) significantly improved in the alendronate-treated group. There were more statistically significant reductions in fasting plasma glucose (-8.2 [8.63] mg/dL vs -2.5 [14.26] mg/dL, P = 0.002) and HbA1c (-0.2 [0.23]% vs -0.09 [0.26]%, P = 0.015) observed in the alendronate-treated group than the placebo group during the study course, respectively. CONCLUSIONS: Administration of 70 mg/week alendronate improves fasting plasma glucose, HbA1c and insulin indices in postmenopausal women.

Thermoelectric performance of n-type Mg2Ge.

Magnesium-based thermoelectric materials (Mg2X, X = Si, Ge, Sn) have received considerable attention due to their availability, low toxicity, and reasonably good thermoelectric performance. The synthesis of these materials with high purity is challenging, however, due to the reactive nature and high vapour pressure of magnesium. In the current study, high purity single phase n-type Mg2Ge has been fabricated through a one-step reaction of MgH2 and elemental Ge, using spark plasma sintering (SPS) to reduce the formation of magnesium oxides due to the liberation of hydrogen. We have found that Bi has a very limited solubility in Mg2Ge and results in the precipitation of Mg2Bi3. Bismuth doping increases the electrical conductivity of Mg2Ge up to its solubility limit, beyond which the variation is minimal. The main improvement in the thermoelectric performance is originated from the significant phonon scattering achieved by the Mg2Bi3 precipitates located mainly at grain boundaries. This reduces the lattice thermal conductivity by ~50% and increases the maximum zT for n-type Mg2Ge to 0.32, compared to previously reported maximum value of 0.2 for Sb-doped Mg2Ge.

Effect of the Fabrication Technique on the Thermoelectric Performance of Mg-Based Compounds-A Case Study of n-Type Mg2Ge.

High performance, low cost, and low toxicity have been the main characteristics associated with magnesium-based thermoelectric materials. Nevertheless, the high volatility of magnesium creates challenges in the synthesis of these materials. In this work, n-type Mg2Ge is synthesized using a solid-state technique, fully characterized, and compared with Mg2Ge fabricated through different processes. We have found that Bi is an ineffective dopant in Mg2Ge and precipitates into Mg2Bi3. Regardless of the technique used, the loss of Mg by evaporation and formation of precipitates in Bi-doped samples resulted in a low charge carrier concentration and, consequently, a low power factor. The precipitates significantly reduced the lattice thermal conductivity, however, leading to a figure-of-merit, zT, of 0.4 at 725 K, improving the previously reported figure-of-merit, zT, of 0.2 for Sb-doped Mg2Ge. This work highlights the impact of the fabrication technique on the thermoelectric performance of Mg-based compounds.

Band-Gap Nonlinearity in Lead Chalcogenide (PbQ, Q = Te, Se, S) Alloys.

Narrow band-gap lead chalcogenides have been developed for several optical and electronic applications. However, band-gap energies of the ternary and quaternary alloys have received little attention compared with the parent binary phases. Here, we have fabricated single-phase ternary (PbTe)1-x (PbSe) x and quaternary (PbTe)0.9-y (PbSe)0.1(PbS) y and (PbTe)0.65-z (PbSe)0.35(PbS) z alloys and shown that although lattice parameters follow Vegard's law as a function of composition, the band-gap energies exhibit a substantial bowing effect. The ternary (PbTe)1-x (PbSe) x system features a smaller bowing parameter predominantly due to the difference in electronegativity between Se and Te, whereas the larger bowing parameters in quaternary alloys are generated from a larger crystal lattice mismatch and larger miscibility gap. These findings can lead to further advances in tuning the band-gap and lattice parameters for optical and electronic applications of lead chalcogenides.

Thermoelectric Performance of Na-Doped GeSe.

Recently, hole-doped GeSe materials have been predicted to exhibit extraordinary thermoelectric performance owing largely to extremely low thermal conductivity. However, experimental research on the thermoelectric properties of GeSe has received less attention. Here, we have synthesized polycrystalline Na-doped GeSe compounds, characterized their crystal structure, and measured their thermoelectric properties. The Seebeck coefficient decreases with increasing Na content up to x = 0.01 due to an increase in the hole carrier concentration and remains roughly constant at higher concentrations of Na, consistent with the electrical resistivity variation. However, the electrical resistivity is large for all samples, leading to low power factors. Powder X-ray diffraction and scanning electron microscopy/energy-dispersive spectrometry results show the presence of a ternary impurity phase within the GeSe matrix for all doped samples, which suggests that the optimal carrier concentration cannot be reached by doping with Na. Nevertheless, the lattice thermal conductivity and carrier mobility of GeSe is similar to those of polycrystalline samples of the leading thermoelectric material SnSe, leading to quality factors of comparable magnitude. This implies that GeSe shows promise as a thermoelectric material if a more suitable dopant can be found.

Processable 2D materials beyond graphene: MoS2 liquid crystals and fibres.

Herein, we show properly engineered MoS2 crystals can readily form liquid crystalline dispersions in water making them ideal candidates for large-scale manufacturing processes. The guideline provided here can serve as the basis to develop practical protocols to address the long-standing goal of large-scale manufacturing of 2D materials.

High-performance multifunctional graphene yarns: toward wearable all-carbon energy storage textiles.

The successful commercialization of smart wearable garments is hindered by the lack of fully integrated carbon-based energy storage devices into smart wearables. Since electrodes are the active components that determine the performance of energy storage systems, it is important to rationally design and engineer hierarchical architectures atboth the nano- and macroscale that can enjoy all of the necessary requirements for a perfect electrode. Here we demonstrate a large-scale flexible fabrication of highly porous high-performance multifunctional graphene oxide (GO) and rGO fibers and yarns by taking advantage of the intrinsic soft self-assembly behavior of ultralarge graphene oxide liquid crystalline dispersions. The produced yarns, which are the only practical form of these architectures for real-life device applications, were found to be mechanically robust (Young's modulus in excess of 29 GPa) and exhibited high native electrical conductivity (2508 ± 632 S m(-1)) and exceptionally high specific surface area (2605 m(2) g(-1) before reduction and 2210 m(2) g(-1) after reduction). Furthermore, the highly porous nature of these architectures enabled us to translate the superior electrochemical properties of individual graphene sheets into practical everyday use devices with complex geometrical architectures. The as-prepared final architectures exhibited an open network structure with a continuous ion transport network, resulting in unrivaled charge storage capacity (409 F g(-1) at 1 A g(-1)) and rate capability (56 F g(-1) at 100 A g(-1)) while maintaining their strong flexible nature.