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Human eyes possess exceptional image-sensing characteristics such as an extremely wide field of view, high resolution and sensitivity with low aberration1. Biomimetic eyes with such characteristics are highly desirable, especially in robotics and visual prostheses. However, the spherical shape and the retina of the biological eye pose an enormous fabrication challenge for biomimetic devices2,3. Here we present an electrochemical eye with a hemispherical retina made of a high-density array of nanowires mimicking the photoreceptors on a human retina. The device design has a high degree of structural similarity to a human eye with the potential to achieve high imaging resolution when individual nanowires are electrically addressed. Additionally, we demonstrate the image-sensing function of our biomimetic device by reconstructing the optical patterns projected onto the device. This work may lead to biomimetic photosensing devices that could find use in a wide spectrum of technological applications.
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Materiales Biomiméticos , Biomimética/instrumentación , Compuestos de Calcio , Nanocables , Óxidos , Retina , Titanio , Diseño de Equipo , Humanos , Robótica/instrumentación , Visión OcularRESUMEN
Photothermal catalysis exhibits promising prospects to overcome the shortcomings of high-energy consumption of traditional thermal catalysis and the low efficiency of photocatalysis. However, there is still a challenge to develop catalysts with outstanding light absorption capability and photothermal conversion efficiency for the degradation of atmospheric pollutants. Herein, we introduced the Co3O4 layer and Pt nanoclusters into the three-dimensional (3D) porous membrane through the atomic layer deposition (ALD) technique, leading to a Pt/Co3O4/AAO monolithic catalyst. The 3D ordered nanochannel structure can significantly enhance the solar absorption capacity through the light-trapping effect. Therefore, the embedded Pt/Co3O4 catalyst can be rapidly heated and the O2 adsorbed on the Pt clusters can be activated to generate sufficient O2- species, exhibiting outstanding activity for the diverse VOCs (toluene, acetone, and formaldehyde) degradation. Optical characterization and simulation calculation confirmed that Pt/Co3O4/AAO exhibited state-of-the-art light absorption and a notable localized surface plasmon resonance (LSPR) effect. In situ diffuse reflectance infrared Fourier transform spectrometry (in situ DRIFTS) studies demonstrated that light irradiation can accelerate the conversion of intermediates during toluene and acetone oxidation, thereby inhibiting byproduct accumulation. Our finding extends the application of AAO's optical properties in photothermal catalytic degradation of air pollutants.
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Acetona , Cobalto , Óxidos , Tolueno , Oxidación-Reducción , Catálisis , Tolueno/análisis , Tolueno/químicaRESUMEN
Atomically thin monolayer two-dimensional (2D) semiconductors with natural immunity to short channel effects are promising candidates for sub-10 nm very large-scale integration technologies. Herein, the ultimate limit in optoelectronic performances of monolayer WSe2 field-effect transistors (FETs) is examined by constructing a sloping channel down to 6 nm. Using a simple scaling method compatible with current micro/nanofabrication technologies, we achieve a record high saturation current up to 1.3 mA/µm at room temperature, surpassing any reported monolayer 2D semiconductor transistors. Meanwhile, quasi-ballistic transport in WSe2 FETs is first demonstrated; the extracted high saturation velocity of 4.2 × 106 cm/s makes it suitable for extremely sensitive photodetectors. Furthermore, the photoresponse speed can be improved by reducing channel length due to an electric field-assisted detrapping process of photogenerated carriers in localized states. As a result, the sloping-channel device exhibits a faster response, higher detectivity, and additional polarization resolution ability compared to planar micrometer-scale devices.
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Quantum dots (QDs) are important frontier luminescent materials for future technology in flexible ultrahigh-definition display, optical information internet, and bioimaging due to their outstanding luminescence efficiency and high color purity. I-III-VI QDs and derivatives demonstrate characteristics of composition-dependent band gap, full visible light coverage, high efficiency, excellent stability, and nontoxicity, and hence are expected to be ideal candidates for environmentally friendly materials replacing traditional Cd and Pb-based QDs. In particular, their compositional flexibility is highly conducive to precise control energy band structure and microstructure. Furthermore, the quantum dot light-emitting diodes (QLEDs) exhibits superior prospects in monochrome display and white illumination. This review summarizes the recent progress of I-III-VI QDs and their application in LEDs. First, the luminescence mechanism is illustrated based on their electronic-band structural characteristics. Second, focusing on the latest progress of I-III-VI QDs, the preparation mechanism, and the regulation of photophysical properties, the corresponding application progress particularly in light-emitting diodes is summarized as well. Finally, we provide perspectives on the overall current status and challenges propose performance improvement strategies in promoting the evolution of QDs and QLEDs, indicating the future directions in this field.
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Herein, we describe an innovative approach to the asymmetric electrochemical α-alkylation of aldehydes facilitated by a newly designed bifunctional chiral electrocatalyst. The highly efficient bifunctional chiral electrocatalyst combines a chiral aminocatalyst with a redox mediator. It plays a dual role as a redox mediator for electrooxidation, while simultaneously providing remarkable asymmetric induction for the stereoselective α-alkylation of aldehydes. Additionally, this novel catalyst exhibits enhanced catalytic activity and excellent stereoselective control comparable to conventional catalytic systems. As a result, this strategy provides a new avenue for versatile asymmetric electrochemistry. The electrooxidation of diverse phenols enables the C-H/C-H oxidative α-alkylation of aldehydes in a highly chemo- and stereoselective fashion. Detailed mechanistic studies by control experiments and cyclic voltammetry analysis demonstrate possible reaction pathways and the origin of enantio-induction.
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Perovskite nanopillars (PNPs) are propitious candidates for solar irradiation harvesting and are potential alternatives to thin films in flexible photovoltaics. To realize efficient daily energy output, photovoltaics must absorb sunlight over a broad range of incident angles and wavelengths congruent with the solar spectrum. Herein, we report highly periodic three-dimensional (3D) PNP-based flexible photovoltaics possessing a core-shell structure. The vertically aligned PNP arrays demonstrate up to 95.70% and 75.10% absorption at peak and under an incident angle of 60°. The efficient absorption and the orthogonal carrier collection facilitate an external quantum efficiency of 84.0%-89.18% for broadband wavelength. PNPs have been successfully implemented in flexible solar cells. The porous alumina membrane protects PNPs against water and oxygen intrusion and thereby imparts robustness to photovoltaic devices. Meanwhile, the excellent tolerance to mechanical stress/strain enables our unique PNP-based device to provide efficient solar-to-electricity conversion while undergoing mechanical bending.
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Charge collection narrowing (CCN) has been reported to be an efficient strategy to achieve optical filter-free narrowband photodetection (NPD) with metal halide perovskite (MHP) single crystals. However, the necessity of utilizing thick crystals in CCN limits their applications in large scale, flexible, self-driven, and high-performance optoelectronics. Here, for the first time, we fabricate vertically integrated MHP quantum wire/nanowire (QW/NW) array based photodetectors in nanoengineered porous alumina membranes (PAMs) showing self-driven broadband photodetection (BPD) and NPD capability simultaneously. Two cutoff detection edges of the NPDs are located at around 770 and 730 nm, with a full-width at half-maxima (fwhm) of around 40 nm. The optical bandgap difference between the NWs and the QWs, in conjunction with the high carrier recombination rate in QWs, contributes to the intriguing NPD performance. Thanks to the excellent mechanical flexibility of the PAMs, a flexible NPD is demonstrated with respectable performance. Our work here opens a new pathway to design and engineer a nanostructured MHP for novel color selective and full color sensing devices.
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BACKGROUND: The present study aimed to investigate the effects of low protein diets balanced with four amino acids on growth performance, meat quality and cecal microflora of finishing pigs. Fifty-four healthy hybrid barrows (Duroc × Landrace × Yorkshire) with an average body weight of 70.12 ± 4.03 kg were randomly assigned to one of the three dietary treatments with six replicate pens per treatment (three barrows per pen). The three dietary treatments included a normal protein diet (NP), a low protein diet (LP) and a very low protein diet (VLP). RESULTS: The average daily gain, average daily feed intake and feed conversion ratio of pigs were not significantly changed with the LP and VLP diets compared to the NP diet (P > 0.05). The water holding capacity and shear force of longissimus dorsi muscle were decreased, whereas the intramuscular fat content of the longissimus dorsi muscle was increased (P < 0.05) in pigs fed with the LP and VLP diets compared to the NP diet. The contents of saturated fatty acids in muscle were decreased (P < 0.05), whereas the content of polyunsaturated fatty acids in muscle was increased (P < 0.01) with the VLP diet compared to the NP diet. The contents of histamine, spermidine, spermine and tyramine of muscle were decreased with the VLP diet compared to the NP diet (P < 0.05). The relative abundance of Turicibacter, Terrisporobacter, Clostridium_sensu_stricto_1 and UCG-005 was higher (P < 0.05), whereas the relative abundance of Lactobacillus and Streptococcus was lower (P < 0.05) in pigs fed with the LP and VLP diets compared to the NP diet. Based on the correlation of cecal microbiota and cecal biogenic amine, the contents of tyramine, spermidine and histamine were negatively correlated with the abundance of Terrisporobacter (P < 0.01) and the content of histamine was positively correlated with the abundance of Lactobacillus (P < 0.01). CONCLUSION: Balanced with four essential amino acids, the VLP diet with crude protein levels decreased by > 4% increased the intramuscular fat content, changed the fatty acid and amino acid composition of longissimus dorsi muscle and the profile of cecum microbiota, and reduced the content of cecum bioamine, with no negative effect on the growth performance of pigs. © 2022 Society of Chemical Industry.
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Dieta con Restricción de Proteínas , Microbioma Gastrointestinal , Animales , Aminoácidos/metabolismo , Alimentación Animal/análisis , Fenómenos Fisiológicos Nutricionales de los Animales , Composición Corporal , Ciego/metabolismo , Dieta/veterinaria , Dieta con Restricción de Proteínas/veterinaria , Ácidos Grasos/metabolismo , Histamina , Carne/análisis , Espermidina/farmacología , Porcinos , TiraminaRESUMEN
BACKGROUND: Fiber added to the diet can promote intestinal mucin secretion, relieve intestinal inflammation, and enhance the intestinal barrier function. Glycosylation is the key to mucin function. However, there are few studies on the correlation between dietary fiber and mucin glycosylation, especially two kinds of dietary fiber with different solubility. The aim of this study was to investigate the effects of soluble glucomannan (GM) and insoluble cellulose (CL) treatment on mucin secretion and mucin glycosylation-related gene expression in the colons of mice. RESULTS: The GM group significantly increased the goblet cell number, crypt depth, and the expression of mucin 2 (Muc2) and mucin 3a (Muc3a) genes in the colon. At the same time, the analysis of the colon transcriptome showed that the GM group changed the expression of genes related to the mucin glycosylation process, and the GM group up-regulated the expression of Gcnt3, Gcnt4, St3gal1, Galnt13, and B3gnt6 genes involved in the O-glycosylation process. Similarly, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that differentially glycosylated genes in the GM group were mainly related to the biosynthesis of mucin type O-glycans, while the genes in the CL group were related to the biosynthesis of various types of N-glycans. The correlation analysis between colonic microbes and differentially glycosylated genes also showed that the abundance of Alistipes in the GM group was significantly associated with the expression of Gcnt3, a key glycosylation gene. CONCLUSION: Glucomannan treatment was more favorable for colonic Muc2 and Muc3a secretion and mucin O-glycosylation gene expression. © 2023 Society of Chemical Industry.
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Celulosa , Mucinas , Ratones , Animales , Mucinas/genética , Glicosilación , Celulosa/metabolismo , Colon/metabolismo , Polisacáridos/metabolismo , Fibras de la Dieta/metabolismo , Expresión Génica , Mucosa Intestinal/metabolismoRESUMEN
Semiconductor chemiresistive gas sensors play critical roles in a smart and sustainable city where a safe and healthy environment is the foundation. However, the poor limits of detection and selectivity are the two bottleneck issues limiting their broad applications. Herein, a unique sensor design with a 3D tin oxide (SnO2 ) nanotube array as the sensing layer and platinum (Pt) nanocluster decoration as the catalytic layer, is demonstrated. The Pt/SnO2 sensor significantly enhances the sensitivity and selectivity of NO2 detection by strengthening the adsorption energy and lowering the activation energy toward NO2 . It not only leads to ultrahigh sensitivity to NO2 with a record limit of detection of 107 parts per trillion, but also enables selective NO2 sensing while suppressing the responses to interfering gases. Furthermore, a wireless sensor system integrated with sensors, a microcontroller, and a Bluetooth unit is developed for the practical indoor and on-road NO2 detection applications. The rational design of the sensors and their successful demonstration pave the way for future real-time gas monitoring in smart home and smart city applications.
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Nanotubos , Platino (Metal) , Gases , Dióxido de Nitrógeno , Óxidos , TemperaturaRESUMEN
Hydrogenation is a promising technique to prepare black TiO2 (H-TiO2 ) for solar water splitting, however, there remain limitations such as severe preparation conditions and underexplored hydrogenation mechanisms to inefficient hydrogenation and poor photoelectrochemical (PEC) performance to be overcome for practical applications. Here, a room-temperature and rapid plasma hydrogenation (RRPH) strategy that realizes low-energy hydrogen ions of below 250 eV to fabricate H-TiO2 nanorods with controllable disordered shell, outperforming incumbent hydrogenations, is reported. The mechanisms of efficient RRPH and enhanced PEC activity are experimentally and theoretically unraveled. It is discovered that low-energy hydrogen ions with fast subsurface transport kinetics and shallow penetration depth features, enable them to directly penetrate TiO2 via unique multiple penetration pathways to form controllable disordered shell and suppress bulk defects, ultimately leading to improved PEC performance. Furthermore, the hydrogenation-property experiments reveal that the enhanced PEC activity is mainly ascribed to increasing band bending and bulk defect suppression, compared to reported H-TiO2 , a superior photocurrent density of 2.55 mA cm-2 at 1.23 VRHE is achieved. These findings demonstrate a sustainable strategy which offers great promise of TiO2 and other oxides to achieve further-improved material properties for broad practical applications.
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With strikingly high speed, data retention ability and storage density, resistive RAMs have emerged as a forerunning nonvolatile memory. Here we developed a Re-RAM with ultra-high density array of monocrystalline perovskite quantum wires (QWs) as the switching matrix with a metallic silver conducting pathway. The devices demonstrated high ON/OFF ratio of â¼107 and ultra-fast switching speed of â¼100 ps which is among the fastest in literature. The devices also possess long retention time of over 2 years and record high endurance of â¼6 × 106 cycles for all perovskite Re-RAMs reported. As a concept proof, we have also successfully demonstrated a flexible Re-RAM crossbar array device with a metal-semiconductor-insulator-metal design for sneaky path mitigation, which can store information with long retention. Aggressive downscaling to â¼14 nm lateral dimension produced an ultra-small cell effectively having 76.5 nm2 area for single bit storage. Furthermore, the devices also exhibited unique optical programmability among the low resistance states.
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2D materials, of which the carrier type and concentration are easily tuned, show tremendous superiority in electronic and optoelectronic applications. However, the achievements are still quite far away from practical applications. Much more effort should be made to further improve their performance. Here, p-type MoSe2 is successfully achieved via substitutional doping of Ta atoms, which is confirmed experimentally and theoretically, and outstanding homojunction photodetectors and inverters are fabricated. MoSe2 p-n homojunction device with a low reverse current (300 pA) exhibits a high rectification ratio (104 ). The analysis of dark current reveals the domination of the Shockley-Read-Hall (SRH) and band-to-band tunneling (BTB) current. The homojunction photodetector exhibits a large open-circuit voltage (0.68 V) and short-circuit currents (1 µA), which is suitable for micro-solar cells. Furthermore, it possesses outstanding responsivity (0.28 A W-1 ), large external quantum efficiency (42%), and a high signal-to-noise ratio (≈107 ). Benefiting from the continuous energy band of homojunction, the response speed reaches up to 20 µs. Besides, the Ta-doped MoSe2 inverter exhibits a high voltage gain (34) and low power consumption (127 nW). This work lays a foundation for the practical application of 2D material devices.
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Osteoarthritis (OA) is a common joint disease characterized by progressive cartilage degradation, in which elevated chondrocyte apoptosis and catabolic activity play an important role. MicroRNA-155 (miR-155) has recently been shown to regulate apoptosis and catabolic activity in some pathological circumstances, yet, whether and how miR-155 is associated with OA pathology remain unexplored. We report here that miR-155 level is significantly up-regulated in human OA cartilage biopsies and also in primary chondrocytes stimulated by interleukin-1ß (IL-1ß), a pivotal pro-catabolic factor promoting cartilage degradation. Moreover, miR-155 inhibition attenuates and its overexpression promotes IL-1ß-induced apoptosis and catabolic activity in chondrocytes in vitro. We also demonstrate that the PIK3R1 (p85α regulatory subunit of phosphoinositide 3-kinase (PI3K)) is a target of miR-155 in chondrocytes, and more importantly, PIK3R1 restoration abrogates miR-155 effects on chondrocyte apoptosis and catabolic activity. Mechanistically, PIK3R1 positively regulates the transduction of PI3K/Akt pathway, and a specific Akt inhibitor reverses miR-155 effects on promoting chondrocyte apoptosis and catabolic activity, phenocopying the results obtained via PIK3R1 knockdown, hence establishing that miR-155 promotes chondrocyte apoptosis and catabolic activity through targeting PIK3R1-mediated PI3K/Akt pathway activation. Altogether, our study discovers novel roles and mechanisms of miR-155 in regulating chondrocyte apoptosis and catabolic activity, providing an implication for therapeutically intervening cartilage degradation and OA progression.
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Condrocitos/metabolismo , Fosfatidilinositol 3-Quinasa Clase Ia/metabolismo , Interleucina-1beta/metabolismo , MicroARNs/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de Señal/fisiología , Apoptosis/fisiología , Cartílago/metabolismo , Células Cultivadas , Matriz Extracelular/metabolismo , Humanos , Osteoartritis/metabolismoRESUMEN
High-photoluminescence quantum yield (PLQY) is required to reach optimal performance in solar cells, lasers, and light-emitting diodes (LEDs). Typically, PLQY can be increased by improving the material quality to reduce the nonradiative recombination rate. It is in principle equally effective to improve the optical design by nanostructuring a material to increase light out-coupling efficiency (OCE) and introduce quantum confinement, both of which can increase the radiative recombination rate. However, increased surface recombination typically minimizes nanostructure gains in PLQY. Here a template-guided vapor phase growth of CH3NH3PbI3 (MAPbI3) nanowire (NW) arrays with unprecedented control of NW diameter from the bulk (250 nm) to the quantum confined regime (5.7 nm) is demonstrated, while simultaneously providing a low surface recombination velocity of 18 cm s-1. This enables a 56-fold increase in the internal PLQY, from 0.81% to 45.1%, and a 2.3-fold increase in OCEy to increase the external PLQY by a factor of 130, from 0.33% up to 42.6%, exclusively using nanophotonic design.
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Levodopa is the standard medication clinically prescribed to patients afflicted with Parkinson's disease. In particular, the monitoring and optimization of levodopa dosage are critical to mitigate the onset of undesired fluctuations in the patients' physical and emotional conditions such as speech function, motor behavior, and mood stability. The traditional approach to optimize levodopa dosage involves evaluating the subjects' motor function, which has many shortcomings due to its subjective and limited quantifiable nature. Here, we present a wearable sweat band on a nanodendritic platform that quantitatively monitors levodopa dynamics in the body. Both stationary iontophoretic induction and physical exercise are utilized as our methods of sweat extraction. The sweat band measures real-time pharmacokinetic profiles of levodopa to track the dynamic response of the drug metabolism. We demonstrated the sweat band's functionalities on multiple subjects with implications toward the systematic administering of levodopa and routine management of Parkinson's disease.
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Monitoreo de Drogas/instrumentación , Levodopa , Enfermedad de Parkinson , Sudor/metabolismo , Dispositivos Electrónicos Vestibles , Femenino , Humanos , Levodopa/administración & dosificación , Levodopa/farmacocinética , Enfermedad de Parkinson/tratamiento farmacológico , Enfermedad de Parkinson/metabolismoRESUMEN
Although obesity (characterized by high levels of serum leptin) and deregulated expression of miRNAs are both functionally implicated in the pathogenesis of chemoresistance of pancreatic ductal adenocarcinoma (PDAC), the mechanistic link synchronize these two factors remain poorly understood. Here, we show that expression levels of obesity-associated miR-342-3p were significantly upregulated in gemcitabine (GEM)-resistant PDAC tissues and cells, and this upregulation was associated with poor postchemotherapy prognosis. Using pharmacological approaches, we observed that crosstalk between leptin and Notch signaling pathways regulated fundamentally the miR-342-3p expression in GEM-resistant PDAC cells. Functionally, forced expression of miR-342-3p exhibited a prosurvival effect and potentiated GEM resistance, whereas inhibition of miR-342-3p expression noticeably ameliorated chemosensitivity in GEM-resistant PDAC cells. By employing bioinformatics analysis, point mutation and luciferase reporter assays, we further identified the 3'-UTR of tumor suppressor Krüppel-like factor 6 (KLF6) as the direct target of miR-342-3p. Therapeutically, stable expression of the exogenous KLF6 was sufficient to abrogate the pro-survival effects of miR-342-3p in GEM-treated PDAC cells. Taken together, these results suggest that leptin-elicited miR-342-3p upregulation mediates, at least partially, the GEM resistance through inhibition of KLF6 signaling in PDAC. Considering the indispensable function of miR-342-3p during adipogenesis, this obesity-associated miRNA may operate as a novel posttranscriptional integrator linking lipid homeostasis and pancreatic chemoresistance.
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Antimetabolitos Antineoplásicos/farmacología , Carcinoma Ductal Pancreático/tratamiento farmacológico , Desoxicitidina/análogos & derivados , Leptina/genética , MicroARNs/genética , Neoplasias Pancreáticas/tratamiento farmacológico , Animales , Antimetabolitos Antineoplásicos/uso terapéutico , Apoptosis/efectos de los fármacos , Carcinoma Ductal Pancreático/genética , Línea Celular Tumoral , Desoxicitidina/farmacología , Desoxicitidina/uso terapéutico , Resistencia a Antineoplásicos , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Factor 6 Similar a Kruppel/genética , Masculino , Ratones Desnudos , Neoplasias Pancreáticas/genética , Regulación hacia Arriba/efectos de los fármacos , GemcitabinaRESUMEN
BACKGROUND: Nucleotides are key constituents of milk, where they are utilized in cell replication, although there are limited studies for weaned piglets. This study evaluated the effects of uridine monophosphate (UMP) with uridine (UR) feed supplementation on the intestinal development and nucleotide transport in weaned piglets. RESULTS: Supplementation with UMP significantly increased (P < 0.05) plasma glucose, and UR supplementation significantly reduced (0.05 < P < 0.10) the plasma total cholesterol (TC) of piglets when compared with that of the control group, although non-significant difference (P > 0.05) in growth performance was observed among three groups. Piglets fed supplementary UR exhibited greater (P < 0.05) crypt depth in the duodenum and ileum when compared with those in the supplementary UMP and control groups. Real-time quantitative polymerase chain reaction (RT-qPCR) results revealed that UR supplementation increased (P < 0.05) the relative mRNA levels of genes encoding the transmembrane proteins ZO-1 and occludin in the duodenum mucosa, and ZO-1 in the jejunum mucosa (P < 0.05). Similarly, UR supplementation increased (P < 0.05) expression of solute carriers SLC28A1 and SLC29A1 in the duodenum mucosa. Conversely, claudin-1 expression in the duodenum mucosa was inhibited (P < 0.05) by dietary supplementation with UMP or UR. CONCLUSION: Collectively, our data indicated that dietary supplementation with UMP or UR was conducive to stimulating intestinal development and promoting nucleotide transport in weaned piglets. © 2019 Society of Chemical Industry.
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Intestino Delgado/crecimiento & desarrollo , Nucleótidos/metabolismo , Porcinos/crecimiento & desarrollo , Uridina Monofosfato/metabolismo , Uridina/metabolismo , Animales , Transporte Biológico , Claudina-1/genética , Claudina-1/metabolismo , Suplementos Dietéticos/análisis , Femenino , Mucosa Intestinal/crecimiento & desarrollo , Mucosa Intestinal/metabolismo , Intestino Delgado/metabolismo , Masculino , Porcinos/genética , Porcinos/metabolismo , DesteteRESUMEN
Zinc oxide (ZnO) nanosheets have demonstrated outstanding electrical and optical properties, which are well suited for ultraviolet (UV) photodetectors. However, they have a high density of intrinsically unfilled traps, and it is difficult to achieve p-type doping, leading to the poor performance for low light level switching ratio and a high dark current that limit practical applications in UV photodetection. Here, UV photodetectors based on ZnO nanosheets are demonstrated, whose performance is significantly improved by using a ferroelectric localized field. Specifically, the photodetectors have achieved a responsivity of up to 3.8 × 105 A W-1 , a detectivity of 4.4 × 1015 Jones, and a photocurrent gain up to 1.24 × 106 . These device figures of merit are far beyond those of traditional ZnO ultraviolet photodetectors. In addition, the devices' initial dark current can be easily restored after continuous photocurrent measurement by using a positive gate voltage pulse. This study establishes a new approach to produce high-sensitivity and low-dark-current ultraviolet photodetectors and presents a crucial step for further practical applications.
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We demonstrate for the first time the application of p-NiFe2O4/n-Fe2O3 composite thin films as anode materials for light-assisted electrolysis of water. The p-NiFe2O4/n-Fe2O3 composite thin films were deposited on planar fluorinated tin oxide (FTO)-coated glass as well as on 3D array of nanospike (NSP) substrates. The effect of substrate (planar FTO and 3D-NSP) and percentage change of each component (i.e., NiFe2O4 and Fe2O3) of composite was studied on photoelectrochemical (PEC) water oxidation reaction. This work also includes the performance comparison of p-NiFe2O4/n-Fe2O3 composite (planar and NSP) devices with pure hematite for PEC water oxidation. Overall, the nanostructured p-NiFe2O4/n-Fe2O3 device with equal molar 1:1 ratio of NiFe2O4 and Fe2O3 was found to be highly efficient for PEC water oxidation as compared with pure hematite, 1:2 and 1:3 molar ratios of composite. The photocurrent density of 1:1 composite thin film on planar substrate was equal to 1.07 mA/cm2 at 1.23 VRHE, which was 1.7 times higher current density as compared with pure hematite device (0.63 mA/cm2 at 1.23 VRHE). The performance of p-NiFe2O4/n-Fe2O3 composites in PEC water oxidation was further enhanced by their deposition over 3D-NSP substrate. The highest photocurrent density of 2.1 mA/cm2 at 1.23 VRHE was obtained for the 1:1 molar ratio p-NiFe2O4/n-Fe2O3 composite on NSP (NF1-NSP), which was 3.3 times more photocurrent density than pure hematite. The measured applied bias photon-to-current efficiency (ABPE) value of NF1-NSP (0.206%) was found to be 1.87 times higher than that of NF1-P (0.11%) and 4.7 times higher than that of pure hematite deposited on FTO-coated glass (0.044%). The higher PEC water oxidation activity of p-NiFe2O4/n-Fe2O3 composite thin film as compared with pure hematite is attributed to the Z-path scheme and better separation of electrons and holes. The increased surface area and greater light absorption capabilities of 3D-NSP devices result in further improvement in catalytic activities.