Multifunctional ytterbium oxide buffer for perovskite solar cells.

Perovskite solar cells (PSCs) comprise a solid perovskite absorber sandwiched between several layers of different charge-selective materials, ensuring unidirectional current flow and high voltage output of the devices1,2. A 'buffer material' between the electron-selective layer and the metal electrode in p-type/intrinsic/n-type (p-i-n) PSCs (also known as inverted PSCs) enables electrons to flow from the electron-selective layer to the electrode3-5. Furthermore, it acts as a barrier inhibiting the inter-diffusion of harmful species into or degradation products out of the perovskite absorber6-8. Thus far, evaporable organic molecules9,10 and atomic-layer-deposited metal oxides11,12 have been successful, but each has specific imperfections. Here we report a chemically stable and multifunctional buffer material, ytterbium oxide (YbOx), for p-i-n PSCs by scalable thermal evaporation deposition. We used this YbOx buffer in the p-i-n PSCs with a narrow-bandgap perovskite absorber, yielding a certified power conversion efficiency of more than 25%. We also demonstrate the broad applicability of YbOx in enabling highly efficient PSCs from various types of perovskite absorber layer, delivering state-of-the-art efficiencies of 20.1% for the wide-bandgap perovskite absorber and 22.1% for the mid-bandgap perovskite absorber, respectively. Moreover, when subjected to ISOS-L-3 accelerated ageing, encapsulated devices with YbOx exhibit markedly enhanced device stability.

Coherent growth of high-Miller-index facets enhances perovskite solar cells.

Obtaining micron-thick perovskite films of high quality is key to realizing efficient and stable positive (p)-intrinsic (i)-negative (n) perovskite solar cells1,2, but it remains a critical challenge. Here, we report an effective method for producing high-quality, micron-thick formamidinium-based perovskite films by forming coherent grain boundaries, where high-Miller-index-oriented grains grow on the low-Miller-index-oriented grains in a stabilized atmosphere. The resulting micron-thick perovskite films, with enhanced grain boundaries and grains, showed stable material properties and outstanding optoelectronic performances. The small-area solar cells achieved efficiencies of 26.1%. The 1-square-centimeter devices and 5 cm × 5 cm minimodules delivered efficiencies of 24.3% and 21.4%, respectively. The devices processed in a stabilized atmosphere presented a high reproducibility across all four seasons. The encapsulated devices exhibited superior long-term stability under both light and thermal stressors in ambient air.

In situcell-scale probing nucleation, growth and evolution of CsPbBr3nanowires by optical absorption spectroscopy.

The growth kinetics of colloidal lead halide perovskite nanomaterials are an integral part of their applications, remains poorly understood due to complex nucleation processes and lack ofin situsize monitoring method. Here we demonstrated that absorption spectra can be used to observein situgrowth processes of ultrathin CsPbBr3nanowires in solution with reference to the effective mass infinite deep square potential well model. By means of this method, we have found that the ultrathin nanowires, fabricated by hot injection method, were firstly formed within one minute. Subsequently, they merge with each other into a thicker structure with increasing reaction time. We revealed that the nucleation, growth, and merging of the CsPbBr3nanowires are determined by the acid concentration and ligand chain length. At lower acidity, the critical nucleation size of the nanowire is smaller, while the shorter the ligand chain length, the faster the merging among the nanowires. Moreover, the merging mode between nanowires changed with their nucleation size. This growth kinetics of CsPbBr3nanowires provides a reference for optimizing the synthesis conditions to obtain the one-dimensional CsPbBr3with desired size, thus enabling accurate control of the nanowire shape.

Solvent-Engineering-Assisted Ligand Exchange Strategy for High-Efficiency AgBiS2 Quantum Dot Solar Cells.

As the initial synthesized colloidal quantum dots (CQDs) are generally capped with insulating ligands, ligand exchange strategies are essential in the fabrication of CQD films for solar cells, which can regulate the surface chemical states of CQDs to make them more suitable for thin-film optoelectronic devices. However, uncontrollable surface adsorption of water molecules during the ligand exchange process introduces new defect sites, thereby impairing the resultant device performance, which attracts more efforts devoted to it but remains a puzzle. Here, we develop a solvent-engineering-assisted ligand exchange strategy to revamp the surface adsorption, improve the exchange efficiency, and modulate the surface chemistry for the environmentally friendly lead-free silver bismuth disulfide (AgBiS2) CQDs. The optimized AgBiS2 CQD solar cells deliver an outstanding champion power conversion efficiency (PCE) of up to 8.95 % and improved long-term stability. Our strategy is less environment-dependent and can produce solar cells with negligible performance variance for several batches across several months. Our work demonstrates the critical role of solvents for ligand exchange in the surface chemistry of CQDs and the realization of high-performance photovoltaic devices in a highly reproducible manner.

Simple Construction of Multistage Stable Silicon-Graphite Hybrid Granules for Lithium-Ion Batteries.

Because of its high specific capacity, the silicon-graphite composite (SGC) is regarded as a promising anode for new-generation lithium-ion batteries. However, the frequently employed two-section preparation process, including the modification of silicon seed and followed mixture with graphite, cannot ensure the uniform dispersion of silicon in the graphite matrix, resulting in a stress concentration of aggregated silicon domains and cracks in composite electrodes during cycling. Herein, inspired by powder engineering, the two independent sections are integrated to construct multistage stable silicon-graphite hybrid granules (SGHGs) through wet granulation and carbonization. This method assembles silicon nanoparticles (Si NPs) and graphite and improves compatibility between them, addressing the issue of severe stress concentration caused by uncombined residue of Si NPs. The optimal SGHG prepared with 20% pitch content exhibits a highly reversible specific capacity of 560.0 mAh g-1 at a current density of 200 mA g-1 and a considerable stability retention of 86.1% after 1000 cycles at 1 A g-1 . Moreover, as a practical application, the full cell delivers an outstanding capacity retention of 85.7% after 400 cycles at 2 C. The multistage stable structure constructed by simple wet granulation and carbonization provides theoretical guidance for the preparation of commercial SGC anodes.

Influence of Volatile Organic Compound Adsorption on the Characteristics of Organic Field-Effect Transistors and Rules for Gas-Sensing Measurements.

Owing to the advantages of organic field-effect transistors (OFETs) in the versatility of organic synthesis, multiparameter measurement, and signal amplification, sensors based on OFETs have received increasing attention for detecting volatile organic compounds (VOCs). However, false device operation and gas-sensing measurements often occur to vitiate the advantages of OFETs and even output error gas-sensing signals. In this work, by experimentally and theoretically studying the effects of VOC adsorption on the operational characteristics of the OFET, the proper operations of OFETs in gas-sensing measurements were clarified. The multiparameter measurements of OFETs showed that the source-drain current was the optimized parameter for achieving high responsivity, and other OFET parameters could be used for fingerprint analysis. By operating OFETs in the near-threshold region, the amplification effect was switched to enhance the responsivity by orders of magnitude to VOCs, while in the overthreshold region, the OFETs had a low signal-to-noise ratio. Besides, a counteraction effect and an uncertainty effect were discovered, leading to error gas-sensing signals. A theoretical study was carried out to reveal the dependency of the gas-sensing properties of OFETs on VOC adsorption. A series of rules were proposed for guiding the measurements of OFET sensors by taking full advantage of transistors in gas-sensing applications.

A General Multi-Interface Strategy toward Densified Carbon Materials with Enhanced Comprehensive Electrochemical Performance for Li/Na-Ion Batteries.

Fast charging rate and large energy storage are key requirements for lithium-ion batteries (LIBs) in electric vehicles. Developing electrode materials with high volumetric and gravimetric capacity that could be operated at a high rate is the most challenging problem. In this work, a general multi-interface strategy toward densified carbon materials with enhanced comprehensive electrochemical performance for Li/Na-ion batteries is proposed. The mixture of graphene oxide and sucrose solution is sprayed into a water/oil system and furtherly carbonized to get graphene/hard carbon spheres (GHSs). In this material, abundant ingenious internal interfaces between the crystalline graphene and the carbon matrix are created inside the hard carbon spheres. The constructed interfaces can not only work as a pathway for the escape of volatile gas generated during sucrose pyrolysis to prevent the formation of abundant pores, which leads high packing density of 0.910 g cm-3 and low surface area of 13.3 m2  g-1 , but can also provide a conductive "highway" for ions and electrons. When used as the anode material for both LIBs and sodium-ion batteries (SIBs), the GHS shows the high gravimetric/volumetric reversible capacities, high-rate performance, and low temperature properties simultaneously, implying the great potential application in practical LIBs and SIBs.

A novel HD-Zip I/C2H2-ZFP/WD-repeat complex regulates the size of spine base in cucumber.

Fruit spine is an important trait in cucumber, affecting not only commercial quality, but also fruit smoothness, transportation and storage. Spine size is determined by a multi-cellular base. However, the molecular mechanism underlying the regulation of cucumber spine base remains largely unknown. Here, we report map-based cloning and characterization of a spine base size 1 (SBS1) gene, encoding a C2H2 zinc-finger transcription factor. Near-isogenic lines of cucumber were used to map, identify and quantify cucumber spine base size 1 (CsSBS1). Yeast-hybrid, bimolecular fluorescence complementation (BiFC), co-immunoprecipitation (Co-IP) and RNA-sequencing assays were used to explore the molecular mechanism of CsSBS1 in regulating spine base size development. CsSBS1 was specifically expressed in cucumber ovaries with particularly high expression in fruit spines. Overexpression of CsSBS1 resulted in large fruit spine base, while RNA-interference silencing of CsSBS1 inhibited the expansion of fruit spine base. Sequence analysis of natural cucumber accessions revealed that CsSBS1 was lost in small spine base accessions, resulting from a 4895 bp fragment deletion in CsSBS1 locus. CsSBS1 can form a trimeric complex with two positive regulators CsTTG1 and CsGL1 to regulate spine base development through ethylene signaling. A novel regulator network is proposed that the CsGL1/CsSBS1/CsTTG1 complex plays a significant role in regulating spine base formation and size, which offers a strategy for cucumber breeders to develop smooth fruit.

Multiple acid-base and electrolyte disturbances upregulate NBCn1, NBCn2, IRBIT and L-IRBIT in the mTAL.

KEY POINTS: The roles of the Na+ /HCO3- cotransporters NBCn1 and NBCn2 as well as their activators IRBIT and L-IRBIT in the regulation of the mTAL transport of NH4+ , HCO3- , and NaCl are investigated. Dietary challenges of NH4 Cl, NaHCO3 or NaCl all increase the abundance of NBCn1 and NBCn2 in the outer medulla. The three challenges generally produce parallel increases in the abundance of IRBIT and L-IRBIT in the outer medulla. Both IRBIT and L-IRBIT powerfully stimulate the activities of the mTAL isoforms of NBCn1 and NBCn2 as expressed in Xenopus oocytes. Our findings support the hypothesis that NBCn1, NBCn2, IRBIT and L-IRBIT appropriately promote NH4+ shunting but oppose HCO3- and NaCl reabsorption in the mTAL, and thus are at the nexus of the regulation pathways for multiple renal transport processes. ABSTRACT: The medullary thick ascending limb (mTAL) plays a key role in urinary acid and NaCl excretion. NBCn1 and NBCn2 are present in the basolateral mTAL, where NBCn1 promotes NH4+ shunting. IRBIT and L-IRBIT (the IRBITs) are two powerful activators of certain acid-base transporters. Here we use western blotting and immunofluorescence to examine the effects of multiple acid-base and electrolyte disturbances on expression of NBCn1, NBCn2 and the IRBITs in rat kidney. We also use electrophysiology to examine the functional effects of IRBITs on NBCn1 and NBCn2 in Xenopus oocytes. NH4 Cl-induced metabolic acidosis (MAc) substantially increases protein expression of NBCn1 and NBCn2 in the outer medulla (OM) of rat kidney. Surprisingly, NaHCO3 -induced metabolic alkalosis (MAlk) and high-salt diet (HSD) also increase expression of NBCn1 and NBCn2 (effect of NaHCO3  > HSD). Moreover, all three challenges generally increase OM expression of the IRBITs. In Xenopus oocytes, the IRBITs substantially increase the activities of NBCn1 and NBCn2. We propose that upregulation of basolateral NBCn1 and NBCn2 plus the IRBITs in the mTAL: (1) promotes NH4+ shunting by increasing basolateral HCO3- uptake to neutralize apical NH4+ uptake during MAc; (2) inhibits HCO3- reabsorption during MAlk by opposing HCO3- efflux via the basolateral anion exchanger AE2; and (3) inhibits NaCl reabsorption by mediating (with AE2) net NaCl backflux into the mTAL cell during HSD. Thus, NBCn1, NBCn2 and the IRBITs are at the nexus of the regulatory pathways for multiple renal transport processes.

Optical design of connecting electrodes for tandem organic light-emitting diodes.

Connecting electrodes play a crucial role to assist charge injection into the adjacent electroluminescent units in tandem organic light-emitting diodes (OLEDs). In this study, we demonstrate that Mg:Ag alloy is an effective connecting electrode for bottom- and top-emitting tandem OLEDs. Optical cavity design and simulation are also conducted to predict the luminance of tandem OLEDs. It is found that the theoretical luminance of tandem OLEDs is close to but not higher than twofold enhancement over the luminance of a single OLED optimized to the first resonance mode, which is theoretically higher than high-order resonance modes. It is also found that the optical properties of Mg:Ag connecting electrodes, while having relatively small influence on weak microcavity bottom-emitting tandem OLEDs, have large influence on strong microcavity top-emitting tandem OLEDs.

Na+/HCO3- Cotransporter NBCn2 Mediates HCO3- Reclamation in the Apical Membrane of Renal Proximal Tubules.

The kidney maintains systemic acid-base balance by reclaiming from the renal tubule lumen virtually all HCO3- filtered in glomeruli and by secreting additional H+ to titrate luminal buffers. For proximal tubules, which are responsible for about 80% of this activity, it is believed that HCO3- reclamation depends solely on H+ secretion, mediated by the apical Na+/H+ exchanger NHE3 and the vacuolar proton pump. However, NHE3 and the proton pump cannot account for all HCO3- reclamation. Here, we investigated the potential contribution of two variants of the electroneutral Na+/HCO3- cotransporter NBCn2, the amino termini of which start with the amino acids MCDL (MCDL-NBCn2) and MEIK (MEIK-NBCn2). Western blot analysis and immunocytochemistry revealed that MEIK-NBCn2 predominantly localizes at the basolateral membrane of medullary thick ascending limbs in the rat kidney, whereas MCDL-NBCn2 localizes at the apical membrane of proximal tubules. Notably, NH4Cl-induced systemic metabolic acidosis or hypokalemic alkalosis downregulated the abundance of MCDL-NBCn2 and reciprocally upregulated NHE3 Conversely, NaHCO3-induced metabolic alkalosis upregulated MCDL-NBCn2 and reciprocally downregulated NHE3 We propose that the apical membrane of the proximal tubules has two distinct strategies for HCO3- reclamation: the conventional indirect pathway, in which NHE3 and the proton pump secrete H+ to titrate luminal HCO3-, and the novel direct pathway, in which NBCn2 removes HCO3- from the lumen. The reciprocal regulation of NBCn2 and NHE3 under different physiologic conditions is consistent with our mathematical simulations, which suggest that HCO3- uptake and H+ secretion have reciprocal efficiencies for HCO3- reclamation versus titration of luminal buffers.

Visible-Light Photoreduction of CO2 in a Metal-Organic Framework: Boosting Electron-Hole Separation via Electron Trap States.

It is highly desirable to convert CO2 to valuable fuels or chemicals by means of solar energy, which requires CO2 enrichment around photocatalysts from the atmosphere. Here we demonstrate that a porphyrin-involved metal-organic framework (MOF), PCN-222, can selectively capture and further photoreduce CO2 with high efficiency under visible-light irradiation. Mechanistic information gleaned from ultrafast transient absorption spectroscopy (combined with time-resolved photoluminescence spectroscopy) has elucidated the relationship between the photocatalytic activity and the electron-hole separation efficiency. The presence of a deep electron trap state in PCN-222 effectively inhibits the detrimental, radiative electron-hole recombination. As a direct result, PCN-222 significantly enhances photocatalytic conversion of CO2 into formate anion compared to the corresponding porphyrin ligand itself. This work provides important insights into the design of MOF-based materials for CO2 capture and photoreduction.

Selective Shielding of the (002) Plane Enabling Vertically Oriented Zinc Plating for Dendrite-Free Zinc Anode.

Uncontrolled growth of Zn dendrites hinders the future development of aqueous Zn-ion batteries. Despite that the (100) plane possesses better zincophilic ability and fast kinetics, dendrites are generally suppressed via (002) plane-oriented Zn deposition in previous reports; the ordered (100) plane-dominant Zn deposition, especially under high current density has not yet been realized. Herein, vertically-oriented Zn plating with preferential growth of (100) plane is reported using disodium lauryl phosphate (DLP) as an electrolyte additive. DLP is preferentially anchored on the Zn (002) crystal plane via the polar phosphate group, then the deposition of Zn atoms on the (002) plane is retarded by the long alkyl chain, finally promoting the preferred growth of the (100) plane. This unique growth pattern results in ultrastable Zn plating/stripping at a super-high current density of 50 mA cm-2 , with a cumulative capacity of 8500 mAh cm-2 . The Zn//Zn symmetric cell also cycles steadily for 700 h with a large areal capacity of 10 mAh cm-2 at a current density of 10 mA cm-2 . This study provides new insights into the realization of dendrite-free Zn anodes by crystal plane modulation.

Selective anchoring of Pt NPs on covalent triazine-based frameworks via in situ derived bridging ligands for boosting photocatalytic hydrogen evolution.

The efficient and stable production of hydrogen (H2) through Pt-containing photocatalysts remains a great challenge. Herein, we develop an effective strategy to selectively and uniformly anchor Pt NPs (∼1.2 nm) on a covalent triazine-based framework photocatalyst via in situ derived bridging ligands. Compared to Pt/CTF-1, the obtained Pt/AT-CTF-1 exhibits a considerable photocatalytic H2 evolution rate of 562.9 µmol g-1 h-1 under visible light irradiation. Additionally, the strong interaction between the Pt NPs and in situ derived bridging ligands provides remarkable stability to Pt/AT-CTF-1. Experimental investigations and photo/chemical characterization reveal the synergy of the in situ derived bridging ligands in Pt/AT-CTF-1, which can selectively anchor the Pt NPs with homogeneous sizes and efficiently improve the transmission of charge carriers. This work provides a new perspective toward stabilizing ultrasmall nanoclusters and facilitating electron transfer in photocatalytic H2 evolution materials.

Effect of vane angle on turbulence-chemistry interactions, temperature, flow field, burnout, and NOx emissions in swirling flames fueled by semicoke mixtures.

To enhance the combustion efficiency and reduce NOx emissions in large-scale semicoke and bituminous coal blends, an extensive numerical study was conducted. The focus of this study was to optimize the quaternary air vane angle (αv) through detailed analysis of the temperature and flow fields, turbulence-chemistry interactions, char burnout, and NOx formation in a carefully scaled 1:5 dual-swirl burner. The results showed that with increasing αv, the high-temperature flame region was narrowed and the peak temperature was reduced along with the broadened inner recirculation zone and the shrunken external recirculation zone due to better pulverized fuel-oxidant blending and reinforced convective heat transfer. The peak turbulent Damköhler number Dat evidently increased from 197.5 to 496 with increasing αv, which implied a strengthened homogeneous combustion. Additionally, the corresponding mixing time scales increased while the chemical kinetics time scales decreased, which denoted that an intense diffusing flame was generated with a strong turbulent intensity. The peak heterogeneous Damköhler number Das-O2 showed a reduction from 2.54 to 2.27, while the peak values of Das-CO2 and Das-H2O decreased from 0.1 to 0.077 and from 0.02 to 0.015, respectively. The char-O2 reaction was controlled by diffusion/kinetics; both char-CO2 and char-H2O reactions were determined by kinetics, and all gas‒solid reactions showed a kinetically controlled regime. With increasing αv, the enlarged inner recirculation region increased the residence time, and a higher dilution level lessened the peak temperature, which led to reductions in fuel-NOx and the thermal-NOx. The αv range of 30-45° (or swirl number Sn = 0.55-0.95) was suggested by taking the high burnout and low-NOx formation into account.

Ion migration in p-type perovskite MAPbI3 films under an electric field and thin-film transistor device failure.

This study demonstrated a dynamic analysis to investigate the ion migration in p-type perovskite MAPbI3 films under an electric field, revealing its detrimental effects on the electrical performance of MAPbI3-based devices. An additive strategy was proposed to suppress ion migration, thereby facilitating the fabrication of high-performance MAPbI3-based devices.

Interfacial Heterojunction Enables High Efficient PbS Quantum Dot Solar Cells.

Colloidal quantum dots (CQDs) are promising optoelectronic materials for solution-processed thin film optoelectronic devices. However, the large surface area with abundant surface defects of CQDs and trap-assisted non-radiative recombination losses at the interface between CQDs and charge-transport layer limit their optoelectronic performance. To address this issue, an interface heterojunction strategy is proposed to protect the CQDs interface by incorporating a thin layer of polyethyleneimine (PEIE) to suppress trap-assisted non-radiative recombination losses. This thin layer not only acts as a protective barrier but also modulates carrier recombination and extraction dynamics by forming heterojunctions at the buried interface between CQDs and charge-transport layer, thereby enhancing the interface charge extraction efficiency. This enhancement is demonstrated by the shortened lifetime of carrier extraction from 0.72 to 0.46 ps. As a result, the resultant PbS CQD solar cells achieve a power-conversion-efficiency (PCE) of 13.4% compared to 12.2% without the heterojunction.

Deep Blue CsPbBr3 Quantum Wires with Tailored Shapes.

Low-dimension metal halide perovskites are attractive for bandgap tunable optoelectronic materials. Among them, 1-D CsPbBr3 quantum wires (QWs) are emerging as promising deep-blue luminescent material. However, the growth dynamics of 1-D perovskite QWs are intricate, making the study and control of 1-D QWs highly challenging. In this study, a strategy for controlling both the length and width of the CsPbBr3 QWs was realized. The temperature-dependent isotropic growth mechanism was revealed and employed as the main tool for the oriented growth of 1-D CsPbBr3 QWs for various aspect ratios. Our results pave the way for the controlled synthesis of ultrasmall perovskite nanocrystals.

Buried-Metal-Grid Electrodes for Efficient Parallel-Connected Perovskite Solar Cells.

The limited conductivity of existing transparent conducting oxide (TCO) greatly restricts the further performance improvement of perovskite solar cells (PSCs), especially for large-area devices. Herein, buried-metal-grid tin-doped indium oxide (BMG ITO) electrodes are developed to minimize the power loss caused by the undesirable high sheet resistance of TCOs. By burying 140-nm-thick metal grids into ITO using a photolithography technique, the sheet resistance of ITO is reduced from 15.0 to 2.7 Ω sq-1 . The metal step of BMG over ITO has a huge impact on the charge carrier transport in PSCs. The PSCs using BMG ITO with a low metal step deliver power conversion efficiencies (PCEs) significantly better than that of their counterparts with higher metal steps. Moreover, compared with the pristine ITO-based PSCs, the BMG ITO-based PSCs show a smaller PCE decrease when scaling up the active area of devices. The parallel-connected large-area PSCs with an active area of 102.8 mm2 reach a PCE of 22.5%. The BMG ITO electrodes are also compatible with the fabrication of inverted-structure PSCs and organic solar cells. The work demonstrates the great efficacy of improving the conductivity of TCO by BMG and opens up a promising avenue for constructing highly efficient large-area PSCs.

Effects of optional structural elements, including two alternative amino termini and a new splicing cassette IV, on the function of the sodium-bicarbonate cotransporter NBCn1 (SLC4A7).

The SLC4A7 gene encodes the electroneutral sodium/HCO3 cotransporter NBCn1, which plays important physiological and pathophysiological roles in many cell types. Previous work identified six NBCn1 variants differing in the sequence of the extreme N terminus--MEAD in rat only, MERF in human only--as well as in the optional inclusion of cassettes I, II, and III. Earlier work also left open the question of whether optional structural elements (OSEs) affect surface abundance or intrinsic (per-molecule) transport activity. Here, we demonstrate for the first time that SLC4A7 from one species can express both MEAD- and MERF-NBCn1. We also identify a novel cassette IV of 20 aa, and extend by 10 the number of full-length NBCn1 variants. The alternative N termini and four cassettes could theoretically produce 32 major variants. Moreover, we identify a group of cDNAs predicted to encode just the cytosolic N-terminal domain (Nt) of NBCn1. A combination of electrophysiology and biotinylation shows that the OSEs can affect surface abundance and intrinsic HCO3(-) transport activity of NBCn1, as expressed in Xenopus oocytes. Specifically, MEAD tends to increase whereas novel cassette IV reduces surface abundance. Cassettes II, III and novel cassette IV all appear to increase the intrinsic activity of NBCn1.