Benzothieno[3,2-b]thiophene-Based Noncovalent Conformational Lock Achieves Perovskite Solar Cells with Efficiency over 24.

Organic semiconductors with noncovalently conformational locks (OSNCs) are promising building blocks for hole-transporting materials (HTMs). However, lack of satisfied neighboring building blocks negatively impacts the optoelectronic properties of OSNCs-based HTMs and imperils the stability of perovskite solar cells (PSCs). To address this limitation, we introduce the benzothieno[3,2-b]thiophene (BTT) to construct a new OSNC, and the resulting HTM ZS13 shows improved intermolecular charge extraction/transport properties, proper energy level, efficient surface passivation effect. Consequently, the champion devices based on doped ZS13 yield an efficiency of 24.39 % and 20.95 % for aperture areas of 0.1 and 1.01 cm2 , respectively. Furthermore, ZS13 shows good thermal stability and the capability of inhibiting I- ion migration, thus, leading to enhanced device stability. The success in neighboring-group engineering can triggered a strong interest in developing thienoacene-based OSNCs toward efficient and stable PSCs.

A predictive model for optimal continuous positive airway pressure in the treatment of pure moderate to severe obstructive sleep apnea in China.

BACKGROUND: Numerous predictive formulas based on different ethnics have been developed to determine continuous positive airway pressure (CPAP) for patients with obstructive sleep apnea (OSA) without laboratory-based manual titrations. However, few studies have focused on patients with OSA in China. Therefore, this study aimed to develop a predictive equation for determining the optimal value of CPAP for patients with OSA in China. METHODS: 526 pure moderate to severe OSA patients with attended CPAP titrations during overnight polysomnogram were spited into either formula derivation (419 patients) or validation (107 patients) group according to the treatment time. Predictive model was created in the derivation group, and the accuracy of the model was tested in the validation group. RESULTS: Apnea hypopnea index (AHI), body mass index (BMI), longest apnea time (LAT), and minimum percutaneous oxygen saturation (minSpO2) were considered as independent predictors of optimal CPAP through correlation analysis and multiple stepwise regression analysis. The best equation to predict the optimal value of CPAP was: CPAPpred = 7.581 + 0.020*AHI + 0.101*BMI + 0.015*LAT-0.028*minSpO2 (R2 = 27.2%, p < 0.05).The correlation between predictive CPAP and laboratory-determined manual optimal CPAP was significant in the validation group (r = 0.706, p = 0.000). And the pressure determined by the predictive formula did not significantly differ from the manually titrated pressure in the validation cohort (10 ± 1 cmH2O vs. 11 ± 3 cmH2O, p = 0.766). CONCLUSIONS: The predictive formula based on AHI, BMI, LAT, and minSpO2 is useful in calculating the effective CPAP for patients with pure moderate to severe OSA in China to some extent.

Role of Vehicular Catalytic Converter Temperature in Emission of Pollutants: An Assessment Based on Isotopic Analysis of CO2 and N2O.

Vehicular catalytic converters are used to regulate, reduce, and convert toxic and environmentally unfriendly compounds in exhaust gases into relatively inert and less harmful chemical species. The efficiency, however, is largely affected by the operating temperature of the converter which is set by the hot exhaust gas released from the combustion chamber. A major gas released during combustion is CO2, and its multiply substituted isotopocule, namely, 13C16O18O, provides a window of opportunity to probe directly the effective temperature of the converter in operation. Here, we report multiple isotopic measurements in exhaust CO2 (δ13C, δ17O, δ18O, and Δ47) of diesel (trucks and buses) and gasoline (sedans, trucks, and two-wheel motorcycles)-powered vehicles. For investigating the efficiency of a converter in reducing toxic compounds, we studied NOx processes through isotopic analysis of the exhaust N2O. We found that the degree of N2O reduction to N2 in gasoline-powered vehicles is high when the temperature is above 200 °C (inferred by Δ47). In contrast, diesel-powered vehicles produce N2O in abundance, probably a consequence of selective catalytic reduction of NOx, and the reduction efficiency depends on the converter temperature. In other words, the catalytic converters act as sinks and sources of N2O to the atmosphere in gasoline- and diesel-operated vehicles, respectively. We also report a new set of field data by measuring the isotopic compositions of CO2 and N2O in the Hsuehshan tunnel, a ∼13 km long highway tunnel in Taiwan. Elevated N2O concentrations inside the tunnel indicate that the emission of N2O by heavy-duty diesel vehicles is much higher compared to the reduction by gasoline-operated passenger cars, making the vehicular exhausts a net source of N2O to the atmosphere. The combined study of clumped isotopes and N2O concentration in exhaust gases suggests that it is useful to probe the operational temperature of catalytic converters and monitor the pollution level in operation, thus providing an opportunity for manufacturers to optimize the catalytic efficiency to reduce the level of toxic pollutants to the environment.

Ab initio quantum chemical studies of isotopic fractionation during acid digestion reaction of dolomite for clumped isotope application.

RATIONALE: In 'clumped isotope paleothermometry' carbonates are reacted with anhydrous phosphoric acid to extract CO2 that carries the isotopic signature of the reacting carbonates, and the amount of clumping in the product CO2 is measured. Previous theoretical models for determining clumped isotopic fractionation in product CO2 during acid digestion of carbonates are independent of the cations present in the carbonate lattice. Hence further study is required to understand the cationic effect. METHODS: We studied the acid reaction mechanism based on the protonation of carbonates, calculated the acid fractionation factor for dolomite using the partition functions and vibrational frequencies obtained for the transition state structure, and determined the effect of cations on the acid fractionation factor. Experimentally, carbonates are reacted using the modified sealed vessel method and analyzed in the dual inlet of a ThermoFinnigan MAT 253 isotope ratio mass spectrometer. RESULTS: The oretically obtained acid fractionation factor can be expressed as Δ47 acid fractionation in dolomite = -0.28563 + 0.49508 * (105 /T2 ) - 0.08231 * (105 /T2 )2 for a temperature range between 278.15 and 383.15 K. The theoretical slope of the dolomite-acid digestion curve is lower than that of the calcite-acid digestion curve obtained using the identical reaction mechanism. Our theoretical slope is consistent with the result from the common acid bath experiments but higher than the slope obtained in our experimental study using the modified sealed vessel method and in a previous theoretical study using the H2 CO3 model. CONCLUSIONS: The transition state structure, obtained in our study, includes the cations present in the carbonate minerals and provides distinct acid fractionation factors for calcite and dolomite. The observed gentler slope of the theoretically calculated dolomite-acid digestion curve than of the calcite curve is expected considering the stronger Mg-O bond. Our experimental approach invokes post-digestion isotopic exchange and agrees with the previous theoretical estimates where post-digestion isotopic fractionation was considered.

Correlating hysteresis phenomena with interfacial charge accumulation in perovskite solar cells.

The property of charge extraction at the contact between the perovskite and electron selective layer (ESL) is vital to the photovoltaic performance of perovskite solar cells (PSCs). The J-V hysteresis phenomenon is frequently observed when the PSC is limited by inefficient charge transfer across the perovskite/ESL interface. Drift-diffusion simulations are performed so as to correlate the hysteresis with the quality of the perovskite/ESL junction. A generalized charge exchange model is introduced into drift-diffusion equations for describing the dynamics of charge extraction at the perovskite/ESL contact. Our simulations demonstrate that inefficient charge extraction is one of the causes of j-V hysteresis. This is because limited charge transfer gives rise to a depletion domain in the ESL, and hence promotes the interfacial accumulation of charge carriers as well as movable ions. Furthermore, it is found that the incorporation of surface recombination into drift-diffusion simulations enables the loss in open circuit voltage to be simulated in PSCs with different charge transfer properties. The simulation results indicate that j-V hysteresis can be suppressed by improving the charge extraction property and suppressing surface recombination.

Indeno[1,2-b]carbazole as Methoxy-Free Donor Group: Constructing Efficient and Stable Hole-Transporting Materials for Perovskite Solar Cells.

With perovskite-based solar cells (PSCs) now reaching efficiencies of greater than 20 %, the stability of PSC devices has become a critical challenge for commercialization. However, most efficient hole-transporting materials (HTMs) thus far still rely on the state-of-the-art methoxy triphenylamine (MOTPA) donor unit in which methoxy groups usually reduce the device stability. Herein, a carbazole-fluorene hybrid has been employed as a methoxy-free donor to construct organic HTMs. The indeno[1,2-b]carbazole group not only inherits the characteristics of carbazole and fluorene, but also exhibits additional advantages arising from the bulky planar structure. Consequently, M129, endowed with indeno[1,2-b]carbazole simultaneously exhibits a promising efficiency of over 20 % and superior long-term stability. The hybrid strategy toward the methoxy-free donor opens a new avenue for developing efficient and stable HTMs.

NANOG Reverses the Myogenic Differentiation Potential of Senescent Stem Cells by Restoring ACTIN Filamentous Organization and SRF-Dependent Gene Expression.

Cellular senescence as a result of organismal aging or progeroid diseases leads to stem cell pool exhaustion hindering tissue regeneration and contributing to the progression of age related disorders. Here we discovered that ectopic expression of the pluripotent factor NANOG in senescent or progeroid myogenic progenitors reversed cellular aging and restored completely the ability to generate contractile force. To elicit its effects, NANOG enabled reactivation of the ROCK and Transforming Growth Factor (TGF)-ß pathways-both of which were impaired in senescent cells-leading to ACTIN polymerization, MRTF-A translocation into the nucleus and serum response factor (SRF)-dependent myogenic gene expression. Collectively our data reveal that cellular senescence can be reversed and provide a novel strategy to regain the lost function of aged stem cells without reprogramming to the pluripotent state. Stem Cells 2017;35:207-221.

Comparison of outcomes between postpartum and non-postpartum women with stress urinary incontinence treated with conservative therapy: A prospective cohort study.

AIM: This study aimed to compare the outcomes of pelvic floor muscle training (PFMT) between postpartum and non-postpartum women with stress urinary incontinence (SUI) and to detect potential factors that may influence these outcomes. METHODS: A total of 54 and 79 participants were recruited into postpartum (PP group) and non-postpartum (non-PP group) groups, respectively. A physiotherapist treated the participants twice a week for 6-8 weeks. At baseline and 6 and 12 months after treatment, the 1-h pad weight test (PWT), vaginal contraction pressure (VCP), and Incontinence Impact Questionnaire Short Form (IIQ-7) were assessed by an evaluator or physiotherapist. The primary outcome was PWT improvement. The participants whose PWT improvement reached a >50% reduction relative to baseline were considered responders. Secondary outcomes included VCP, IIQ-7 score, and patient satisfaction rate. RESULTS: The PWT improvement was 87.04% (95%CI: 0.78, 0.96) in the PP group at 1-year follow-up, which was significantly better than the 72.15% improvement (95%CI: 0.62, 0.82) in the non-PP group (OR = 2.591, 95%CI: 1.018, 6.595, P = 0.041). Changes in VCP and BMI were significant predictors of responders in the regression analysis. As the change in VCP increased by 1 cmH2 O, the efficiency increased by 4.2% (OR = 1.042, 95%CI: 1.010, 1.070). The change in BMI increased by 1 kg/m2 , and the efficiency decreased 23.0% (OR = 0.770, 95%CI: 0.633, 0.937). CONCLUSIONS: The outcome of PFMT in postpartum participants with SUI was better than that in non-postpartum participants. Women with more improvements in VCP and weight loss showed better amelioration of SUI symptoms after PFMT.

Probing energy losses from dye desorption in cobalt complex-based dye-sensitized solar cells.

Self-assembly of organic sensitizer layers in cobalt complex-based DSCs was studied to elucidate its role in reducing the loss of charge recombination. DSCs with various dye loadings were fabricated by dye desorption without the aid of basic solvent. The FT-IR and UV results indicate the deprotonation of the anchoring organic sensitizers, which influences the conduction band of TiO2 remarkably by changing the surface potential. Positive band edge shifts and a decrease of the recombination rate constant are demonstrated to be the main factors affecting energy loss at open circuit. In contrast, absorbed photon conversion efficiency (APCE) analyses illuminate the crucial role of the packing of the anchoring sensitizer in reducing recombination loss at short circuit. This is further supported by numerical simulations, which show that APCE is primarily dependent on the recombination rate constant rather than the band edge shift at short circuit. These results highlight the importance of self-assembly of sensitizers with insulating groups in retarding charge recombination by forming overlapping molecular layers.

Preparation of Silver Nanowires with High Aspect Ratio and Influence of Reaction Conditions on the Morphology Size.

Silver nanowires with high yield, uniform size and high aspect ratio were successfully synthesized by a simple and effective polyol method under low temperature and quiescent conditions, adopting CuCl2·2H2O as the nucleation control agent for the first time. The synthesized silver nanowires were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis diffuse reflectance spectroscopy (DRS). The results indicate that the silver nanowires were composed of face-centered cubic structure of pure metallic silver with high crystallinity. And the silver nanowires have an average length of 80~100 µm and an average diameter of 40~80 nm. Thus, the aspect ratio of the nanowires was greater than 1000. In addition, the influence on the morphology and structure of the silver nanowires were investigated for reaction temperature, mole ratio of PVP:AgNO3, molecular weight of PVP and mole ratio of control agent CuCl2 · 2H2O:AgNO3. Finally, the optimum reaction condition were obtained for the preparation of the silver nanowires with high aspect ratio.

[Determination of 5-hydroxytryptamine,Adrenalin and Noradrenalin in Human Plasma by Pre-column Derivatization HPLC-MS/MS].

OBJECTIVE: To establish a method for the determination of 5-hydroxy tryptamine (5-HT),adrenalin (AD) and noradrenalin (NA) in human plasma using pre-column derivatization HPLC-MS/MS. Methods Derivatives of the plasma samples were produced with dansyl chloride under pH 10.5,and then extracted and enriched with ethyl acetate. The detected chemicals were separated using Ultimate C18 (50 mm×4.6 mm,5 µm) with acetonitrile-water-formic acid=95∶5∶0.05 (V∶V∶V) at 0.2 mL/min. The HPLC-MS//MS system was operated under a multiple reaction monitoring mode (MRM) using the electrospray ionization technique in positive mode. RESULTS: Linear range of the calibration curve appeared in 250-2.5 ng/mL. The method had a less than 9% intra- and inter-assay relative standard deviation (RSD),95.44%-109.71% recoveries,and 4.86%-12.81% matrix effects. CONCLUSION: This method is simple,accurate,and suitable for detection of 5-HT,AD and NA in human plasma.

[Determination of Voriconazole in Human Plasma and Its Bioequivalence by HPLC-MS/MS].

OBJECTIVE: To develop a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the determination of voriconazole in human plasma and its bioequivalence. METHODS: 48 healthy male volunteers received a single dose of 200 mg voriconazole tablets in a two period (with two preparations) and randomized crossover bioequivalence study. Their plasma voriconazole was determined using HPLC-MS/MS. The pharmacokinetic parameters and bioequivalence of the two preparations were calculated with WinNonlin®6.1. RESULTS: The calibration curve of voriconazole ranged from 1 to 5 000 ng/mL. The HPLC-MS/MS method had less than 11% intra- and inter-day relative standard deviation (RSD),with 100.00% to 109.73% accuracies. The RSD of the matrix effect of voriconazole adjusted with internal standard was less than 15%. The extract recoveries exceeded 50% with good stability. The 90% confidence intervals for the peak concentration (Cmax) and the area under the curve (AUC0-t and AUC0-∞)of voriconazole fell into the bioequivalence range of 80.00%-125.00%. There was no significant difference in peak time (Tmax) between the two preparations. CONCLUSION: HPLC-MS/MS can be used for determination of voriconazole in human plasma. The two tested preparations of voriconazole are bioequivalent.

[LC-MS/MS Determination of Tenofovir in Human Plasma and Its Bioequivalence].

OBJECTIVE: To develop a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detecting tenofovir in human plasma. METHODS: Twenty four healthy male volunteers received a single oral dose of 300 mg tenofovir disoproxil fumarate tablets under fasting and high-fat diet conditions in a randomized four-way crossover bioequivalence study with two preparations of tablets. Plasma samples were taken and analyzed using the LC-MS/MS method. The pharmacokinetic parameters of the two preparations were calculated and compared statistically to evaluate their bioequivalence using Phoenix Winnonlin6.3. RESULTS: Linear detection responses were obtained for tenofovir at the range from 3.13 to 500 ng/mL. The intra- and inter-day precisions were high,with lower than 5.43% [relative standard deviation (RSD)%],high recovery and good stability. The 90% confidence intervals of peak concentration (Cmax) of tenofovir and its area under the curve (AUC0-t and AUC0-∞ ) all fell within the bioequivalence limit 80.00%-125.00% under both fasting and high-fat diet conditions. No significant difference in peak time (Tmax) was demonstrated between the two preparations (P>0.05) . CONCLUSION: The LC-MS/MS method can be used for simultaneous determination of tenofovir in human plasma. The two preparations of tablets are bioequivalent.

[Pharmacokinetics Study of Phentolamine Mesylate Injection in Healthy Volunteers].

OBJECTIVE: To study the pharmacokinetic profile of phentolamine mesylate injection in healthy Chinese volunteers. METHODS: A total of 16 healthy volunteers were randomly divided into two groups, each receiving anterior teeth submucosal infiltration anesthesia and inferior alveolar nerve block anesthesia, respectively. The participants were injected with 0.9 mL, 1.8 mL, and 3.6 mL of 2% lidocaine HCl with 1∶100 000 epinephrine over three periods sequentially, followed by corresponding sequential injection of 0.2 mg, 0.4 mg, 0.8 mg of phentolamine mesylate at the same sites 30 min later.Blood samples were drawn from 5 min before injection to 15 h post the injection of phentolamine mesylate (16 time points). Adverse events were closely observed all the time. Plasma phentolamine mesylate was detected using UPLC-MS/MS with isotope as internal standard. WinNolin 6.1 software was used to calculate the pharmacokinetic parameters. RESULTS: Time to peak concerntration (Tmax) ranged from 12 to 13 min. Half-time of elimination (t1/2) ranged from 3.84 to 4.07 h, with a clearance (CL) of 190 L/h. Peak concentration (Cmax), area under concentration-time curves from 0 to t hour and from 0 to infinite time (AUC0-t and AUC0-∞) increased proportionally in the dose range of 0.2 mg to 0.8 mg. The results of confidence interval analysis showed nearly linear dynamic characteristics for the injection of phentolamine mesylate. All participants experienced mild adverse events, including pain at the injection point, dizziness, and palpitations. These adverse events disappeared without treatments. CONCLUSIONS: Phentolamine mesylate injection is effective for reversing oral local anesthetic effects.

[Pharmacokinetics of Phosphate Retagliptin Tabletin in Patients with Renal Dysfunction].

OBJECTIVE: To compared the differences in pharmacokinetics of phosphate retagliptin tablets in patients with varying degrees of renal dysfunction. METHODS: A total of 32 patients were categorized into five groups according to their renal function: normal,mild dysfunction, moderate dysfunction,severe dysfunction,and end stage renal dysfunction (ESRD). All of the patients took a single dose of 50 mg phosphate retagliptin tablet. Their plasma and urinary concentrations of phosphate retagliptin (SP2086) and phosphate retagliptin acid (SP2086 acid) were determined using LC-MS/MS methods. The plasma pharmacokinetic parameters were calculated using WinNolin 6.1 software. RESULTS: Peak concentrations (Cmax) of SP2086 reached at (1.07±0.35) h in the patients with mild renal dysfunction,(1.50±0.89) h in the patients with moderate renal dysfunction,(1.67±2.16) h in the patients with severe renal dysfunction,(2.42±2.15) h in the patients with ESRD,and (1.75±1.21) h in the normal participants,with a clearance (CL/F) of (23.50±6.01) ,(12.90±4.34) ,(6.70±1.55) ,(3.10±0.48) ,and (30.50±10.70) L/h,respectively. With the increasing damages in renal function presented an incease in Cmax,time to reach Cmax (Tmax),and area under curve (AUC), a decrease in CL/F, of SP2086 and SP2086 acid. The 0-96 hurine cumulative excretion percentage (Ae%) of SP2086 ranged from 0.441% to 4.530%. The Ae% of SP2086 acid reached (71.7±14.3) % in the patients with mild renal dysfunction, (59.5±22.7) % in the patients with moderate renal dysfunction, (63.3±13.9) % in the patients with severe renal dysfunction, (34.1±20.0) % in the patient with ESRD,and (74.2±14.6) % in the normal participants, with a renal clearance (CL/R) of (220.0±51.2),(105.0±64.5),(54.5±7.6),(13.5±7.8),and (289.0±73.7) mL/min,respectively. Compared with the participants with normal renal function,the AUCs of SP2086 and SP2086 acid were 1.44 times and 2.32 times higher in the patients with moderate renal dysfunction,2.20 times and 4.39 times higher in the patients with severe renal dysfunction, and 2.83 times and 9.28 times higher in the patients with ESRD. CONCLUSION: The dosage of phosphate retagliptin tablet is recommended at 100 mg/d for patients with normal renal function and those with mild renal dysfunction,at 50 mg/d for patients with moderate renal dysfunction,and at 25 mg/d for patients with severe renal dysfunction. No phosphate retagliptin tablet is recommended for patients with ESRD.

Organic sensitizers featuring thiophene derivative based donors with improved stability and photovoltaic performance.

Thiophene derivatives, including thieno[3,2-b][1]benzothiophene (TBT), benzo[b]thiophene (BT), 2-phenylthieno[3,2-b]thiophene (PTT) and 2-phenylthiophene (PT), have been introduced as donors for the construction of triarylamine organic dyes (M52, M53, M56, M57 and M52A). The absorption, electrochemical and photovoltaic properties as well as the stabilities of these dyes are systematically investigated and compared with the reference dye (M55), whose donor is composed of the hexyloxybenzene (HOB) unit. It is found that introducing the TBT, BT, PTT or PT donors positively shifted the HOMO and LUMO levels of the organic dyes, providing a larger driving force for regeneration and reducing the energy loss for electron injection. In addition, we found that M52, which contains the TBT unit, exhibited better photovoltaic performance and photostability as compared to the reference dye. In contrast, M53 displayed the lowest efficiency and stability of these dyes, indicating that the BT unit is not a good building block for donors. Interestingly, upon the incorporation of the mixed donor (TBT-HOB), M52A achieved a desirable driving force for regeneration without a loss in light absorption, thus resulting in a further improved photovoltaic performance with respect to that of M52. This work demonstrates that introducing donors based on thiophene derivatives is a good strategy for tuning the energy levels and thereby enhancing the efficiency of the resulting devices.

Kinetics of Iodine-Free Redox Shuttles in Dye-Sensitized Solar Cells: Interfacial Recombination and Dye Regeneration.

Dye-sensitized solar cells (DSCs) have gained widespread attentions owing to their low production cost, tunable optical response, and high light-to-electricity conversion. In DSCs, the performance of redox mediators with iodide/triiodide or iodine-free redox couples is vital to internal quantum efficiency. For a long time, iodide/triiodide based electrolytes are the most widely used mediators because of their desirable kinetics. Recently, exciting progress has been made with respect to iodine-free metallorganic and pure organic redox shuttles. Their tunable redox potential and diverse electron transfer behaviors enable the rational screening of electrolyte composition for enhancing the light-to-electricity conversion efficiency of DSCs toward the Shockley-Queisser limit. In this Account, we emphasize on current knowledge of two distinct but interrelated interfacial processes (electron recombination and dye regeneration), particularly for DSCs with iodine-free redox couples. We show that a deeper understanding of electron transfer kinetics of the alternative redox couples is fundamental to develop rational strategies for cell optimization. Compared with iodine electrolyte, iodine-free metallorganic redox couples such as iron, cobalt, and nickel complexes display much faster electron transfer kinetics in dye regeneration and interfacial recombination. Evidently, rapid regeneration enables the employment of more positive metal complex for attaining a higher photovoltage. However, severe recombination reactions have to be well controlled by using several effective surface treatments such as the addition of Brönsted bases and atomic layer deposition. Although these methods offer different pathways in surface passivation, a trade-off between charge injection efficiency and electron diffusion length is always observed. It follows that an appropriate LUMO level of sensitizer is essential to ensure efficient electron injection at the passivated TiO2 surface. Apart from fast recombination behavior, bulky metal complexes suffer from inefficient charge transport. Thus, the combination of thinner TiO2 film and sensitizers with high mole extinction coefficient has been employed for both enhancing diffusion-limited current and maintaining light-harvesting efficiency. Unlike metal complexes, most of organic sulfur redox couples in DSCs exhibit slow recombination kinetics. This allows the use of thicker TiO2 film to achieve an optimized light harvesting. However, the concomitant sluggish behavior of dye regeneration requires the use of sensitizers with more positive HOMO level, which is beneficial to efficient regeneration. Moreover, lower level of TiO2 band edge in DSCs based on organic sulfur mediators hinders the achievement of desirable photovoltage, spurring future explorations on this class of redox mediator. Based on the comparison of electron transfer behavior between iodine-free metallorganic complexes and pure organic redox couples, we aim to provide a comprehensive Account of the intriguing interfacial processes in iodine-free DSCs as the key scientific point is linked with the kinetics of interfacial reactions. This demonstrates the advantages as well as disadvantages of each class of iodine-free electrolyte and should shed light on to judicious selection of the energy levels for redox mediators, sensitizers, and the conduction band of TiO2 for DSCs. The knowledge of the reaction kinetics in DSCs should be also beneficial to the interface engineering on recent developed perovskite cells.

An improved method of high-precision determination of Δ(17)O of CO2 by catalyzed exchange with O2 using hot platinum.

RATIONALE: CO2 and O2 can exchange their oxygen isotopes rapidly in the presence of hot (~670 °C) platinum and this has led to a method for determining the δ(17)O value of a CO2 sample. We have improved the method to achieve a precision of 0.008 ‰ (1-σ standard deviation) in the determination of δ(17)O values. Such high precision is essential to identify the stratospheric component in tropospheric CO2 and use it for global carbon flux studies. The crucial issue in the accurate determination of the δ(17)O value is estimation of a correction factor, which depends on the amount ratio CO2/O2. An attempt was also made to investigate the mechanism of exchange with their controlling parameters. METHODS: The oxygen isotopes of a CO2 sample gas are exchanged with those of an appropriate amount of tank O2 in the presence of hot platinum. The pre-exchange CO2 and O2 gas samples as well as the post-exchange O2 sample are analyzed by isotope ratio mass spectrometry. A mixing model was developed involving the δ(18)O value of the CO2 and δ(17)O and δ(18)O values of pre- and post-exchange O2 to obtain the δ(17)O value of the CO2 sample. A correction to the measured value was determined to obtain the actual value with high accuracy and precision. RESULTS: To obtain a precision better than 0.01 ‰ requires the amount ratio CO2/O2 to be controlled to better than ~15 %. We also find that the oxygen isotopes are nearly homogeneously distributed between the O2 and the CO2 molecules. In addition, determination of the (16) O(13)C(18)O/(16)O(12)C(16)O isotopologue ratio in the CO2 shows that the abundance of (16)O(13)C(18)O is close to that expected for random partitioning of the isotopes among the CO2 isotopologues. CONCLUSIONS: The isotopic scrambling between O2 and CO2 that occurs on hot platinum allows one to accurately determine the δ(17)O values of CO2 through isotopic analysis of O2.

Identification of Anthropogenic CO2 Using Triple Oxygen and Clumped Isotopes.

Quantification of contributions from various sources of CO2 is important for understanding the atmospheric CO2 budget. Considering the number and diversity of sources and sinks, the widely used proxies such as concentration and conventional isotopic compositions (δ13C and δ18O) are not always sufficient to fully constrain the CO2 budget. Additional constraints may help in understanding the mechanisms of CO2 production and consumption. The anomaly in triple oxygen isotopes or 17O excess (denoted by Δ17O) and molecules containing two rare isotopes, called clumped isotopes, are two recently developed tracers with potentials to independently constrain some important processes that regulate CO2 in the atmosphere. The clumped isotope for CO2, denoted by Δ47, is the excess of 13C16O18O over a random distribution of isotopes in a CO2 molecule. We measured the concentrations of δ13C, δ18O, Δ17O, and Δ47 in air CO2 samples collected from the Hsuehshan tunnel (length: 12.9 km), and applied linear and polynomial regressions to obtain the fossil fuel end-members for all these isotope proxies. The other end-members, the values of all these proxies for background air CO2, are either assumed or taken as the values obtained over the tunnel and ocean. The fossil fuel (anthropogenic) CO2 end-member values for δ13C, δ18O, Δ17O, and Δ47 are estimated using the two component mixing approach: the derived values are -26.76 ± 0.25‰, 24.57 ± 0.33‰, -0.219 ± 0.021‰, and 0.267 ± 0.036‰, respectively. These four major CO2 isotope tracers along with the concentration were used to estimate the anthropogenic contribution in the atmospheric CO2 in urban and suburban locations. We demonstrate that Δ17O and Δ47 have the potential to independently estimate anthropogenic contribution, and the advantages of these two over the conventional isotope proxies are discussed.

Midlatitude atmospheric OH response to the most recent 11-y solar cycle.

The hydroxyl radical (OH) plays an important role in middle atmospheric photochemistry, particularly in ozone (O(3)) chemistry. Because it is mainly produced through photolysis and has a short chemical lifetime, OH is expected to show rapid responses to solar forcing [e.g., the 11-y solar cycle (SC)], resulting in variabilities in related middle atmospheric O(3) chemistry. Here, we present an effort to investigate such OH variability using long-term observations (from space and the surface) and model simulations. Ground-based measurements and data from the Microwave Limb Sounder on the National Aeronautics and Space Administration's Aura satellite suggest an ∼7-10% decrease in OH column abundance from solar maximum to solar minimum that is highly correlated with changes in total solar irradiance, solar Mg-II index, and Lyman-α index during SC 23. However, model simulations using a commonly accepted solar UV variability parameterization give much smaller OH variability (∼3%). Although this discrepancy could result partially from the limitations in our current understanding of middle atmospheric chemistry, recently published solar spectral irradiance data from the Solar Radiation and Climate Experiment suggest a solar UV variability that is much larger than previously believed. With a solar forcing derived from the Solar Radiation and Climate Experiment data, modeled OH variability (∼6-7%) agrees much better with observations. Model simulations reveal the detailed chemical mechanisms, suggesting that such OH variability and the corresponding catalytic chemistry may dominate the O(3) SC signal in the upper stratosphere. Continuing measurements through SC 24 are required to understand this OH variability and its impacts on O(3) further.