Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Resultados 1 - 20 de 76
Filtrar
1.
Biochem Biophys Res Commun ; 735: 150489, 2024 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-39096883

RESUMEN

Drought is the primary factor limiting rice production in ecosystems. Wild rice rhizosphere bacteria possess the potential to assist in the stress resistance of cultivated rice. This study examines the impact of wild rice rhizosphere bacteria on cultivated rice under drought conditions. From the rhizosphere soil of wild rice, 20 potential drought-resistant strains were isolated. Subsequent to the screening, the most effective strain b3, was identified as Enterobacter ludwigii. Pot experiments were conducted on the cultivated Changbai 9 rice. It was found that inoculation with the E. ludwigii b3 strain improved the drought resistance of the rice, promotion of rice growth (shoot height increased by 13.47 %), increased chlorophyll content (chlorophyll a, chlorophyll b and carotenoid increased by 168.74 %, 130.68 % and 87.89 %), improved antioxidant system (content of glutathione was increased by 60.35 %), and accumulation of osmotic regulation substances (soluble sugar and soluble protein increased by 70.36 % and 142.03 %). Furthermore, E. ludwigii b3 had a transformative effect on the rhizosphere bacterial community of cultivated rice, increasing its abundance and diversity while simultaneously recruiting beneficial rhizosphere bacteria, resulting in a more complex community. Additionally, E. ludwigii b3 acted directly and indirectly on cultivated rice through its metabolites (organic acids, amino acids, flavonoids and other substances), which helped alleviate drought stress. In conclusion, the E. ludwigii b3 shows promise as a drought-resistant strain and has the potential to improve the growth and productivity of cultivated rice in arid agricultural ecosystems. This study represents the first investigation of E. ludwigii in the rhizosphere of wild rice under drought conditions on cultivated rice.

2.
J Org Chem ; 89(12): 8734-8744, 2024 Jun 21.
Artículo en Inglés | MEDLINE | ID: mdl-38814709

RESUMEN

A gold-catalyzed oxidative rearrangement of propargyl alcohols, derived from commercially available cyclohex-2-en-1-ones and alkynes, was successfully developed for the efficient synthesis of seven-membered rings. Thorough investigations were conducted to optimize the reaction conditions and evaluate its compatibility with various functional groups. Additionally, this methodology was applied to the formal total synthesis of guanacastepene A, demonstrating its practical utility in complex natural product synthesis. This versatile and efficient approach opens up new possibilities for the construction of diverse seven-membered ring systems, providing valuable building blocks for further exploration in drug discovery and the synthesis of intricate molecules.

3.
Inorg Chem ; 63(10): 4707-4715, 2024 Mar 11.
Artículo en Inglés | MEDLINE | ID: mdl-38410082

RESUMEN

A robust, microporous, and photoactive aluminum-based metal-organic framework (Al-MOF, LCU-600) has been assembled by an in situ-formed [Al3O(CO2)6] trinuclear building unit and a tritopic carbazole ligand. LCU-600 shows a high water stability and permanent porosity for N2 and CO2 adsorption. Notably, the incorporation of photoresponsive carbazole moieties into LCU-600 makes it a highly efficient and recyclable photocatalyst for aerobic photo-oxidation of sulfides into sulfoxides under an air atmosphere at room temperature. Mechanism investigations unveil that photogenerated holes (h+), superoxide radical anion (O2•-), and singlet oxygen (1O2) are critical active spices for the photo-oxidation reaction performed in an air atmosphere.

4.
J Card Surg ; 37(6): 1479-1485, 2022 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-35355334

RESUMEN

BACKGROUND AND AIM: The objective of this study was to understand the clinical efficacy and application of the percutaneous left atrial appendage occlusion (PLAAO) guided only by the transesophageal echocardiography (TEE) in patients with nonvalvular atrial fibrillation (NVAF), without using the fluoroscopy and angiography. METHODS: During the time period of this study from June 2020 to June 2021, 32 patients underwent PLAAO and all underwent a TEE guided approach. The anatomical features of the left atrial appendage (LAA) were evaluated and observed by TEE before and during the procedure. LAA occluder device was selected for the appropriate size. Intraoperative TEE guided and monitored the process of PLAAO in real-time, and also evaluated the stability and tightness of the occluder device, following monitored postoperative complications. RESULTS: The PLAAO procedure was successful in all the patients. No serious complications like dislocation of the occluder and embolism were seen. Postoperative TEE demonstrated that the PLAAO occluder devices were in a good position without residual shunting. CONCLUSIONS: PLAAO only guided by TEE may become a safe and reliable surgical procedure, which can protect surgeons and patients from radiation, and can gradually become a novel surgical method of PLAAO with the practical application value.


Asunto(s)
Apéndice Atrial , Fibrilación Atrial , Angiografía , Apéndice Atrial/diagnóstico por imagen , Apéndice Atrial/cirugía , Fibrilación Atrial/complicaciones , Fibrilación Atrial/cirugía , Cateterismo Cardíaco , Ecocardiografía Transesofágica/métodos , Fluoroscopía , Humanos , Resultado del Tratamiento
5.
Heart Surg Forum ; 25(5): E638-E644, 2022 Sep 12.
Artículo en Inglés | MEDLINE | ID: mdl-36317916

RESUMEN

BACKGROUND: Ventricular septal defect (VSD) and atrial septal defect (ASD) are congenital heart diseases. The techniques of transthoracic closure (TC) and percutaneous closure (PC) for the treatment of VSD and ASD have continuously improved and matured. This study aimed to retrospectively analyze the therapeutic effects of TC and PC on VSD and ASD patients. METHODS: We retrospectively reviewed 928 patients (552 VSD and 376 ASD) who had undergone TC or PC guided by transesophageal ultrasound at the Department of Cardiac Macrovascular Surgery of the First Affiliated Hospital of Nanchang University between August 2010 and August 2020. We collected and evaluated the clinical data of the patients, including age, gender, weight, inlet and outlet diameters of defect, and the operation results of TC and PC. Descriptive statistics were used to analyze means and standard deviations (SD), and the Chi-square test was used to evaluate the difference between groups. RESULTS: Among the 928 patients who were treated with the closure operation, there were no casualties, with 907 patients (97.7%) showing successful closure. Among the 552 VSD patients who were treated with TC, 540 showed successful close, while 12 cases required extracorporeal circulation after the failure of TC. Among the 376 patients with ASD, 256 patients were treated with TC, of which 251 were successful, and five were failures, including three shedding cases. In addition, among the 120 patients who were treated with PC, 116 were successful, and four were failures, including two shedding cases. Postoperative follow up for patients with successful closure operations demonstrated that the complications of aortic and tricuspid regurgitation, hydro-pericardium, III° atrioventricular block, shedding of closure umbrella, hemolysis, and thrombosis had not occurred. CONCLUSION: Closure operation of VSD and ASD by esophageal ultrasound has the advantages of lower trauma and blood loss, shorter hospital stay, simple operation, fewer postoperative complications, and significant therapeutic efficacy.


Asunto(s)
Defectos del Tabique Interatrial , Defectos del Tabique Interventricular , Humanos , Estudios Retrospectivos , Resultado del Tratamiento , Defectos del Tabique Interventricular/cirugía , Defectos del Tabique Interatrial/cirugía , Ultrasonografía Intervencional
6.
Biochem Biophys Res Commun ; 567: 79-85, 2021 08 27.
Artículo en Inglés | MEDLINE | ID: mdl-34144504

RESUMEN

circRNAs have been suggested to modulate NSCLC tumorigenesis and drug resistance. Whether circSNX6 affects NSCLC remains unclear. In this study, we aim to investigate the role of circSNX6 in drug resistance of NSCLC exposed to cisplatin. RT-qPCR method was used to investigate expression levels of circSNX6, miR-137 and CXCL12. MTT, cell colony formation and TUNEL assays were utilized to assess cell viability, proliferation, apoptosis, respectively. Xenograft assay was conducted to examinein vivotumor growth. circSNX6 overexpression caused enhanced cell viability and proliferation of H1299 and Calu-1, while it inhibited apoptosis under cisplatin treatment. miR-137 inhibitor greatly rescued cell viability, proliferation and apoptosis of circSNX6 knockdown H1299 cells. miR-137 mimic increased ROS generation, as well as reduced GSH and SOD levels, whereas miR-137 inhibitor exerted opposing effect. circSNX6 knockdown also enhanced ROS generation, as well as decreased GSH and SOD levels. CXCL12 partially restored miR-137 mimic-modulated cell viability, proliferation and apoptosis. Herein, our group proposes circSNX6 as key regulator for drug resistance of NSCLC. The findings provide solid groundings for understanding of NSCLC pathogenesis and development of therapeutics.


Asunto(s)
Carcinoma de Pulmón de Células no Pequeñas/genética , Resistencia a Antineoplásicos , Neoplasias Pulmonares/genética , MicroARNs/genética , ARN Circular/genética , Animales , Antineoplásicos/farmacología , Antineoplásicos/uso terapéutico , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Línea Celular Tumoral , Cisplatino/farmacología , Cisplatino/uso terapéutico , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Masculino , Ratones Endogámicos NOD , Ratones SCID
7.
FASEB J ; 34(6): 8526-8543, 2020 06.
Artículo en Inglés | MEDLINE | ID: mdl-32359120

RESUMEN

Opioid analgesics remain the mainstay for managing intractable chronic pain, but their use is limited by detrimental side effects such as analgesic tolerance and hyperalgesia. Calcium-dependent synaptic plasticity is a key determinant in opiates tolerance and hyperalgesia. However, the exact substrates for this calcium-dependent synaptic plasticity in mediating these maladaptive processes are largely unknown. Canonical transient receptor potential 1, 4, and 5 (TRPC1, 4, 5) proteins assemble into heteromultimeric nonselective cation channels with high Ca2+ permeability and influence various neuronal functions. However, whether and how TRPC1/4/5 channels contribute to the development of opiates tolerance and hyperalgesia remains elusive. Here, we show that TRPC1/4/5 channels contribute to the generation of morphine tolerance and hyperalgesia. Chronic morphine exposure leads to upregulation of TRPC1/4/5 channels in the spinal cord. Spinally expressed TRPC1, TPRC4, and TRPC5 are required for chronic morphine-induced synaptic long-term potentiation (LTP) as well as remodeling of synaptic spines in the dorsal horn, thereby orchestrating functional and structural plasticity during the course of morphine-induced hyperalgesia and tolerance. These effects are attributed to TRPC1/4/5-mediated Ca2+ elevation in the spinal dorsal horn induced by chronic morphine treatment. This study identifies TRPC1/4/5 channels as a promising novel target to prevent the unwanted morphine tolerance and hyperalgesia.


Asunto(s)
Hiperalgesia/inducido químicamente , Hiperalgesia/metabolismo , Morfina/farmacología , Plasticidad Neuronal/fisiología , Médula Espinal/metabolismo , Canales Catiónicos TRPC/metabolismo , Analgésicos/farmacología , Analgésicos Opioides/farmacología , Animales , Tolerancia a Medicamentos/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Plasticidad Neuronal/efectos de los fármacos , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Médula Espinal/efectos de los fármacos , Asta Dorsal de la Médula Espinal/efectos de los fármacos , Asta Dorsal de la Médula Espinal/metabolismo
8.
Hereditas ; 158(1): 3, 2021 Jan 02.
Artículo en Inglés | MEDLINE | ID: mdl-33388093

RESUMEN

BACKGROUND: Preterm infants are a special population that vulnerable to respiratory syncytial virus (RSV) infection and the lower respiratory tract infections (LRTIs) caused by RSV could be severe and even life-threating. The purpose of the present study was to identify candidate genes of preterm infants who are susceptible to RSV infection and provide a new insight into the pathogenesis of RSV infection. METHODS: Three datasets (GSE77087, GSE69606 and GSE41374) containing 183 blood samples of RSV infected patients and 33 blood samples of healthy controls from Gene Expression Omnibus (GEO) database were downloaded and the differentially expressed genes (DEGs) were screened out. The function and pathway enrichments were analyzed through Database for Annotation, Visualization and Integrated Discovery (DAVID) website. The protein-protein interaction (PPI) network for DEGs was constructed through Search Tool for the Retrieval of Interacting Genes (STRING). The module analysis was performed by Cytoscape software and hub genes were identified. Clinical verification was employed to verify the expression level of top five hub genes among 72 infants including 50 RSV infected patients and 22 non-RSV-infected patients hospitalized in our center. Further, the RSV infected infants with high-expression IFI27 and those with low-expression IFI27 were compared (defined as higher or lower than the median mRNA level). Finally, the gene set enrichment analysis (GSEA) focusing on IFI27 was carried out. RESULTS: Totally, 4028 DEGs were screened out and among which, 131 most significant DEGs were selected. Subsequently, 13 hub genes were identified, and function and pathway enrichments of hub genes mainly were: response to virus, defense response to virus, regulation of viral genome replication and regulation of viral life cycle. Furthermore, IFI27 was confirmed to be the most significantly expressed in clinical verification. Gene sets associated with calcium signaling pathway, arachidonic acid metabolism, extracellular matrix receptor interaction and so on were significantly enriched when IFI27 was highly expressed. Moreover, high-expression IFI27 was associated with more severe cases (p = 0.041), more requirements of mechanical ventilation (p = 0.034), more frequent hospitalization (p < 0.001) and longer cumulative hospital stay (p = 0.012). CONCLUSION: IFI27 might serve to predict RSV infection and evaluate the severity of RSV infection in preterm infants.


Asunto(s)
Recien Nacido Prematuro , Proteínas de la Membrana/genética , Infecciones por Virus Sincitial Respiratorio/genética , Estudios de Casos y Controles , Predisposición Genética a la Enfermedad , Humanos , Recién Nacido , Tiempo de Internación , Mapas de Interacción de Proteínas , Respiración Artificial
9.
J Wound Ostomy Continence Nurs ; 48(6): 568-572, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34781314

RESUMEN

BACKGROUND: Tuberculosis (TB) is a leading infectious disease worldwide. It rarely occurs in the scapula and toe joints and is easily misdiagnosed. Without prompt treatment, the associated lesions can spread to surrounding soft tissues such as joint capsules, muscles, tendons, and fascia. In severe cases, the bones and articular surfaces can become significantly damaged; it is not uncommon for deep skeletal TB wounds with sinus tracts to form, which are very difficult to treat. We report our successful wound care management approach for one patient with multiple skeletal TB complicated with multiple deep sinus tracts. CASE: The patient was treated with anti-TB medications, and wound and bone debridement (sharps, surgical) combined with vacuum-shielded drainage (VSD) (Kula, CG Bio Co Ltd, Gyeonggi-do, South Korea) to fill the sinus tract. We removed the caseous (cheese-like) necrotic tissue, purulent drainage, and necrotic tissue at the base of the wound to ensure optimal wound care. Throughout the course of treatment, we selected different types of dressings to maintain moist wound healing and absorb excessive drainage. After 144 days of treatment, the wound and deep sinus tracts completely healed. CONCLUSIONS: Wounds related to skeletal TB with multiple sinus tracts are difficult to manage and heal. We found our wound protocol that included timely debridement and use of VSD was effective for the management of these complex wounds. Specifically, our approach filled the dead space in the sinus tract, removed excessive drainage, promoted the growth of granulation tissue, and overall promoted tissue healing.


Asunto(s)
Terapia de Presión Negativa para Heridas , Tuberculosis , Desbridamiento , Drenaje , Humanos , Trasplante de Piel , Resultado del Tratamiento , Cicatrización de Heridas
10.
Zhongguo Dang Dai Er Ke Za Zhi ; 22(7): 690-695, 2020 Jul.
Artículo en Zh | MEDLINE | ID: mdl-32669162

RESUMEN

OBJECTIVE: To investigate the incidence of severe neonatal hyperbilirubinemia and the management on the treatment and follow-up of this disease in Jiangsu Province, China. METHODS: The neonates with severe hyperbilirubinemia who were admitted to 13 hospitals in Jiangsu Province from January to December, 2018, were enrolled as subjects. A retrospective analysis was performed on their mediacal data and follow-up data. RESULTS: In 2018, 740 neonates with severe hyperbilirubinemia were reported from the 13 hospitals in Jiangsu Province, accounting for 2.70% (740/27 386) of the total number of neonates admitted to the department of neonatology. Among these neonates, 620 (83.8%) had severe hyperbilirubinemia, 106 (14.3%) had extremely severe hyperbilirubinemia, and 14 (1.9%) had hazardous hyperbilirubinemia. Four neonates (0.5%) were diagnosed with acute bilirubin encephalopathy. A total of 484 neonates (65.4%) were readmitted due to severe hyperbilirubinemia after discharge from the delivery institution, with a median age of 7 days, among whom 214 (44.2%) were followed up for jaundice at the outpatient service before readmission, with a median age of 6 days at the first time of outpatient examination. During hospitalization, 211 neonates (28.5%) underwent cranial MRI examinations, among whom 85 (40.3%) had high T1WI signal in the bilateral basal ganglia and the globus pallidus; 238 neonates (32.2%) underwent brainstem auditory evoked potential examinations, among whom 14 (5.9%) passed only at one side and 7 (2.9%) failed at both sides. The 17 neonates with acute bilirubin encephalopathy or hazardous hyperbilirubinemia were followed up. Except one neonate was lost to follow-up, and there were no abnormal neurological symptoms in the other neonates. CONCLUSIONS: Neonates with severe hyperbilirubinemia account for a relatively high proportion of the total number of neonates in the department of neonatology. Jaundice monitoring and management after discharge from delivery institutions need to be strengthened. For neonates with severe hyperbilirubinemia, relevant examinations should be carried out more comprehensively during hospitalization and these neonates should be followed up comprehensively and systematically after discharge.


Asunto(s)
Hiperbilirrubinemia Neonatal , Bilirrubina , China , Potenciales Evocados Auditivos del Tronco Encefálico , Humanos , Recién Nacido , Estudios Retrospectivos
11.
Phys Rev Lett ; 122(15): 153602, 2019 Apr 19.
Artículo en Inglés | MEDLINE | ID: mdl-31050527

RESUMEN

We measure the conductivity of neutral fermions in a cubic optical lattice. Using in situ fluorescence microscopy, we observe the alternating current resultant from a single-frequency uniform force applied by displacement of a weak harmonic trapping potential. In the linear response regime, a neutral-particle analog of Ohm's law gives the conductivity as the ratio of total current to force. For various lattice depths, temperatures, interaction strengths, and fillings, we measure both real and imaginary conductivity, up to a frequency sufficient to capture the transport dynamics within the lowest band. The spectral width of the real conductivity reveals the current dissipation rate in the lattice, and the integrated spectral weight is related to thermodynamic properties of the system through a sum rule. The global conductivity decreases with increased band-averaged effective mass, which at high temperatures approaches a T-linear regime. Relaxation of current is observed to require a finite lattice depth, which breaks Galilean invariance and enables damping through collisions between fermions.

12.
Med Sci Monit ; 25: 6965-6971, 2019 Sep 16.
Artículo en Inglés | MEDLINE | ID: mdl-31525175

RESUMEN

BACKGROUND Autologous saphenous vein is the most common choice for coronary artery bypass grafting. This study was conducted to identify and characterize differentially expressed genes (DEGs) induced by overexpressing DEPTOR in human saphenous vein endothelial cells (hsVECs) that might play roles in restenosis. MATERIAL AND METHODS hsVECs isolated from the saphenous veins were transfected with DEPTOR overexpression vector and analyzed for mTOR expression. RNA was prepared from the cells and sequenced using high-throughput sequencing technology (RNA-Seq). The DEGs were analyzed based on enrichment scores in GO terms and KEGG pathways. RESULTS The cells had typical hsVEC morphology and characteristics based on the HE staining and immunohistochemical and immunofluorescence assays. The expression of mTOR increased, and 102 genes were upregulated, and 409 genes were downregulated after DEPTOR overexpression. KEGG analysis showed that the DEGs were mainly enriched in 20 signal pathways, such as Focal adhesion and ECM-receptor interaction pathways. The DEGs were enriched in GO terms such as integrin binding and glycosaminoglycan binding. For cellular components, GO analysis revealed that the DEGs were enriched in main axon, plasma membrane part, cell junction, and proteinaceous extracellular matrix. DEGs included many cytokines, such as bone morphogenetic protein-7, interleukin-8, interleukin-1ß, and inhibin, which have important effects on vascular growth and inflammation. CONCLUSIONS The overexpression of DEPTOR in hsVECs results in DEGs that are involved in cell proliferation and differentiation, intercellular junction, and extracellular matrix receptor. These findings may provide valuable molecular information for improving venous permeability through manipulation of DEPTOR and related mTOR pathways.


Asunto(s)
Células Endoteliales/metabolismo , Perfilación de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Vena Safena/citología , Biomarcadores/metabolismo , Células Cultivadas , Regulación de la Expresión Génica , Ontología de Genes , Humanos , RNA-Seq , Serina-Treonina Quinasas TOR/genética , Serina-Treonina Quinasas TOR/metabolismo
13.
Chem Rev ; 116(18): 10888-933, 2016 Sep 28.
Artículo en Inglés | MEDLINE | ID: mdl-26974736

RESUMEN

The solution-liquid-solid (SLS) and related solution-based methods for the synthesis of semiconductor nanowires and nanorods are reviewed. Since its discovery in 1995, the SLS mechanism and its close variants have provided a nearly general strategy for the growth of pseudo-one-dimensional nanocrystals. The various metallic-catalyst nanoparticles employed are summarized, as are the syntheses of III-V, II-VI, IV-VI, group IV, ternary, and other nanorods and nanowires. The formation of axial heterojunctions, core/shell nanowires, and doping are also described. The related supercritical-fluid-liquid-solid (SFLS), electrically controlled SLS, flow-based SLS, and solution-solid-solid (SSS) methods are discussed, and the crystallographic characteristics of the wires and rods grown by these methods are summarized. The presentation of optical and electronic properties emphasizes electronic structures, absorption cross sections, polarization anisotropies, and charge-carrier dynamics, including photoluminescence intermittency (blinking) and photoluminescence modulation by charges and electric fields. Finally, developing applications for the pseudo-one-dimensional nanostructures in field-effect transistors, lithium-ion batteries, photocathodes, photovoltaics, and photodetection are discussed.

14.
Inorg Chem ; 56(21): 12920-12929, 2017 Nov 06.
Artículo en Inglés | MEDLINE | ID: mdl-28984450

RESUMEN

Cadmium bis(phenyldithiocarbamate) [Cd(PTC)2] is prepared and structurally characterized. The compound crystallizes in the monoclinic space group P21/n. A one-dimensional polymeric structure is adopted in the solid state, having bridging PTC ligands and 6-coordinate pseudo-octahedral Cd atoms. The compound is soluble in DMSO, THF, and DMF and insoluble in EtOH, MeOH, CHCl3, CH2Cl2, and toluene. {CdSe[n-octylamine]0.53} quantum belts and Cd(PTC)2 react to deposit epitaxial CdS shells on the nanocrystals. With an excess of Cd(PTC)2, the resulting thick shells contain spiny CdS nodules grown in the Stranski-Krastanov mode. Stoichiometric control affords smooth, monolayer CdS shells. A base-catalyzed reaction pathway is elucidated for the conversion of Cd(PTC)2 to CdS, which includes phenylisothiocyanate and aniline as intermediates, and 1,3-diphenylthiourea as a final product.

15.
Nano Lett ; 16(2): 889-94, 2016 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-26731426

RESUMEN

A simple and potentially general means of eliminating the planar defects and phase alternations that typically accompany the growth of semiconductor nanowires by catalyzed methods is reported. Nearly phase-pure, defect-free wurtzite II-VI semiconductor quantum wires are grown from solid rather than liquid catalyst nanoparticles. The solid-catalyst nanoparticles are morphologically stable during growth, which minimizes the spontaneous fluctuations in nucleation barriers between zinc blende and wurtzite phases that are responsible for the defect formation and phase alternations. Growth of single-phase (in our cases the wurtzite phase) nanowires is thus favored.

16.
Acc Chem Res ; 48(1): 13-21, 2015 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-25490745

RESUMEN

CONSPECTUS: Semiconductor nanocrystals having an extended length dimension and capable of efficiently transporting energy and charge would have useful applications in solar-energy conversion and other emerging technologies. Pseudocylindrical semiconductor nanowires and quantum wires are available that could potentially serve in this role. Sadly, however, their defective surfaces contain significant populations of surface trap sites that preclude efficient transport. The very large surface area of long wires is at least part of the problem. As electrons, holes, and excitons migrate along a nanowire or quantum wire, they are exposed to an extensive surface and to potentially large numbers of trap sites. A solution to this dilemma might be found by identifying "long" semiconductor nanocrystals of other morphologies that are better passivated. In this Account, we discuss a newly emerging family of flat semiconductor nanocrystals that have surprising characteristics. These thin, flat nanocrystals have up to micrometer-scale (orthogonal) lateral dimensions and thus very large surface areas. Even so, their typical photoluminescence efficiencies of 30% are astonishingly high and are 2 orders of magnitude higher than those typical of semiconductor quantum wires. The very sharp emission spectra of the pseudo-two-dimensional nanocrystals reflect a remarkable uniformity in their discrete thicknesses. Evidence that excitons are effectively delocalized and hence transported over the full dimensions of these nanocrystals has been obtained. The excellent optical properties of the flat semiconductor nanocrystals confirm that they are exceptionally well passivated. This Account summarizes the two synthetic methods that have been developed for the preparation of pseudo-two-dimensional semiconductor nanocrystals. A discussion of their structural features accounts for their discrete, uniform thicknesses and details the crystal-lattice expansions and contractions they exhibit. An analysis of their optical properties justifies the sharp photoluminescence spectra and high photoluminescence efficiencies. Finally, a bilayer mesophase template pathway is elucidated for the formation of the nanocrystals, explaining their flat morphologies. Magic-size nanocluster intermediates are found to be potent nanocrystal nucleants, allowing the synthesis temperatures to be decreased to as low as room temperature. The potential of these flat semiconductor nanocrystals in the form of nanoribbons or nanosheets for long-range energy and charge transport appears to be high.

17.
Phys Rev Lett ; 116(20): 205303, 2016 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-27258875

RESUMEN

We report the successful production of an ultracold sample of absolute ground-state ^{23}Na^{87}Rb molecules. Starting from weakly bound Feshbach molecules formed via magnetoassociation, the lowest rovibrational and hyperfine level of the electronic ground state is populated following a high-efficiency and high-resolution two-photon Raman process. The high-purity absolute ground-state samples have up to 8000 molecules and densities of over 10^{11} cm^{-3}. By measuring the Stark shifts induced by external electric fields, we determined the permanent electric dipole moment of the absolute ground-state ^{23}Na^{87}Rb and demonstrated the capability of inducing an effective dipole moment over 1 D. Bimolecular reaction between ground-state ^{23}Na^{87}Rb molecules is endothermic, but we still observed a rather fast decay of the molecular sample. Our results pave the way toward investigation of ultracold molecular collisions in a fully controlled manner and possibly to quantum gases of ultracold bosonic molecules with strong dipolar interactions.

18.
J Am Chem Soc ; 137(48): 15198-208, 2015 Dec 09.
Artículo en Inglés | MEDLINE | ID: mdl-26568026

RESUMEN

Reaction of n-octylamine-passivated {CdSe[n-octylamine](0.53±0.06)} quantum belts with anhydrous metal carboxylates M(oleate)2 (M = Cd, Zn) results in a rapid exchange of the L-type amine passivation for Z-type M(oleate)2 passivation. The cadmium-carboxylate derivative is determined to have the composition {CdSe[Cd(oleate)2](0.19±0.02)}. The morphologies and crystal structures of the quantum belts are largely unaffected by the exchange processes. Addition of n-octylamine or oleylamine to the M(oleate)2-passivated quantum belts removes M(oleate)2 and restores the L-type amine passivation. Analogous, reversible surface exchanges are also demonstrated for CdS quantum platelets. The absorption and emission spectra of the quantum belts and platelets are reversibly shifted to lower energy by M(oleate)2 passivation vs amine passivation. The largest shift of 140 meV is observed for the Cd(oleate)2-passivated CdSe quantum belts. These shifts are attributed entirely to changes in the strain states in the Zn(oleate)2-passivated nanocrystals, whereas changes in strain states and confinement dimensions contribute roughly equally to the shifts in the Cd(oleate)2-passivated nanocrystals. Addition of Cd(oleate)2, which electronically couples to the nanocrystal lattices, increases the effective thickness of the belts and platelets by approximately a half of a monolayer, thus increasing the confinement dimension.

19.
Phys Rev Lett ; 114(25): 255301, 2015 Jun 26.
Artículo en Inglés | MEDLINE | ID: mdl-26197132

RESUMEN

We report the observation of coherent heteronuclear spin dynamics driven by interspecies spin-spin interaction in an ultracold spinor mixture, which manifests as periodical and well-correlated spin oscillations between two atomic species. In particular, we investigate the magnetic field dependence of the oscillations and find a resonance behavior which depends on both the linear and quadratic Zeeman effects and the spin-dependent interaction. We also demonstrate a unique knob for controlling the spin dynamics in the spinor mixture with species-dependent vector light shifts.

20.
Sci Total Environ ; 949: 175184, 2024 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-39089386

RESUMEN

Artificial regulation of plant rhizosphere microbial communities through the synthesis of microbial communities is one of the effective ways to improve plant stress resistance. However, the process of synthesizing stress resistant microbial communities with excellent performance is complex, time-consuming, and costly. To address this issue, we proposed a novel strategy for preparing functional microbial communities. We isolated a cultivable cold tolerant bacterial community (PRCBC) from the rhizosphere of peas, and studied its effectiveness in assisting rice to resist stress. The results indicate that PRCBC can not only improve the ability of rice to resist cold stress, but also promote the increase of rice yield after cold stress relieved. This is partly because PRCBC increases the nitrogen content in the rhizosphere soil, and promotes rice's absorption of nitrogen elements, thereby promoting rice growth and enhancing its ability to resist osmotic stress. More importantly, the application of PRCBC drives the succession of rice rhizosphere microbial communities, and promotes the succession of rice rhizosphere microbial communities towards stress resistance. Surprisingly, PRCBC drives the succession of rice rhizosphere microbial communities towards a composition similar to PRCBC. This provides a feasible novel method for artificially and directionally driving microbial succession. In summary, we not only proposed a novel and efficient strategy for preparing stress resistant microbial communities to promote plant stress resistance, but also unexpectedly discovered a possible directionally driving method for soil microbial community succession.


Asunto(s)
Microbiota , Oryza , Rizosfera , Microbiología del Suelo , Microbiota/fisiología , Oryza/fisiología , Oryza/microbiología , Frío , Respuesta al Choque por Frío/fisiología , Bacterias/metabolismo
SELECCIÓN DE REFERENCIAS
Detalles de la búsqueda