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1.
Nature ; 630(8015): 96-101, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38750361

RESUMEN

Chemical doping is an important approach to manipulating charge-carrier concentration and transport in organic semiconductors (OSCs)1-3 and ultimately enhances device performance4-7. However, conventional doping strategies often rely on the use of highly reactive (strong) dopants8-10, which are consumed during the doping process. Achieving efficient doping with weak and/or widely accessible dopants under mild conditions remains a considerable challenge. Here, we report a previously undescribed concept for the photocatalytic doping of OSCs that uses air as a weak oxidant (p-dopant) and operates at room temperature. This is a general approach that can be applied to various OSCs and photocatalysts, yielding electrical conductivities that exceed 3,000 S cm-1. We also demonstrate the successful photocatalytic reduction (n-doping) and simultaneous p-doping and n-doping of OSCs in which the organic salt used to maintain charge neutrality is the only chemical consumed. Our photocatalytic doping method offers great potential for advancing OSC doping and developing next-generation organic electronic devices.

2.
Nat Methods ; 21(5): 908-913, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38514779

RESUMEN

Mapping neuronal networks from three-dimensional electron microscopy (3D-EM) data still poses substantial reconstruction challenges, in particular for thin axons. Currently available automated image segmentation methods require manual proofreading for many types of connectomic analysis. Here we introduce RoboEM, an artificial intelligence-based self-steering 3D 'flight' system trained to navigate along neurites using only 3D-EM data as input. Applied to 3D-EM data from mouse and human cortex, RoboEM substantially improves automated state-of-the-art segmentations and can replace manual proofreading for more complex connectomic analysis problems, yielding computational annotation cost for cortical connectomes about 400-fold lower than the cost of manual error correction.


Asunto(s)
Conectoma , Imagenología Tridimensional , Sinapsis , Conectoma/métodos , Animales , Ratones , Humanos , Imagenología Tridimensional/métodos , Sinapsis/fisiología , Sinapsis/ultraestructura , Microscopía Electrónica/métodos , Inteligencia Artificial , Algoritmos , Procesamiento de Imagen Asistido por Computador/métodos , Corteza Cerebral/citología
3.
Nature ; 599(7883): 67-73, 2021 11.
Artículo en Inglés | MEDLINE | ID: mdl-34732866

RESUMEN

Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices1-9. N(electron)-doping is fundamentally more challenging than p(hole)-doping and typically achieves a very low doping efficiency (η) of less than 10%1,10. An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability1,5,6,9,11, which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal (for example, Pt, Au, Pd) as vapour-deposited nanoparticles or solution-processable organometallic complexes (for example, Pd2(dba)3) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling greatly increased η in a much shorter doping time and high electrical conductivities (above 100 S cm-1; ref. 12). This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants and semiconductors, thus opening new opportunities in n-doping research and applications12, 13.

4.
Proc Natl Acad Sci U S A ; 120(13): e2218847120, 2023 03 28.
Artículo en Inglés | MEDLINE | ID: mdl-36940339

RESUMEN

Surface tension provides microbubbles (MB) with a perfect spherical shape. Here, we demonstrate that MB can be engineered to be nonspherical, endowing them with unique features for biomedical applications. Anisotropic MB were generated via one-dimensionally stretching spherical poly(butyl cyanoacrylate) MB above their glass transition temperature. Compared to their spherical counterparts, nonspherical polymeric MB displayed superior performance in multiple ways, including i) increased margination behavior in blood vessel-like flow chambers, ii) reduced macrophage uptake in vitro, iii) prolonged circulation time in vivo, and iv) enhanced blood-brain barrier (BBB) permeation in vivo upon combination with transcranial focused ultrasound (FUS). Our studies identify shape as a design parameter in the MB landscape, and they provide a rational and robust framework for further exploring the application of anisotropic MB for ultrasound-enhanced drug delivery and imaging applications.


Asunto(s)
Barrera Hematoencefálica , Microburbujas , Barrera Hematoencefálica/diagnóstico por imagen , Ultrasonografía , Transporte Biológico , Sistemas de Liberación de Medicamentos
5.
Angew Chem Int Ed Engl ; : e202407273, 2024 May 21.
Artículo en Inglés | MEDLINE | ID: mdl-38770935

RESUMEN

A new approach to control the n-doping reaction of organic semiconductors is reported using surface-functionalized gold nanoparticles (f-AuNPs) with alkylthiols acting as the catalyst only upon mild thermal activation. To demonstrate the versatility of this methodology, the reaction of the n-type dopant precursor N-DMBI-H with several molecular and polymeric semiconductors at different temperatures with/without f-AuNPs, vis-à-vis the unfunctionalized catalyst AuNPs, was investigated by spectroscopic, morphological, charge transport, and kinetic measurements as well as, computationally, the thermodynamic of catalyst activation. The combined experimental and theoretical data demonstrate that f-AuNPs is inactive at room temperature both in solution and in the solid state, catalyst activation occurs rapidly at mild temperatures (~ 70 °C) and the doping reaction completes in few seconds affording large electrical conductivities (~ 10 - 140 S cm-1). The implementation of this methodology enables the use of semiconductor+dopant+catalyst solutions, will broaden the use of the corresponding n-doped films in opto-electronic devices such as thin-film transistors, electrochemical transistors, solar cells, and thermoelectrics well as guide the design of new catalysts.

6.
Nano Lett ; 22(21): 8626-8632, 2022 11 09.
Artículo en Inglés | MEDLINE | ID: mdl-36256878

RESUMEN

Organometallic sandwich complexes are versatile molecular systems that have been recently employed for single-molecule manipulation and spin sensing experiments. Among related organometallic compounds, the mixed-sandwich S = 1/2 complex (η8-cyclooctatetraene)(η5-cyclopentadienyl)titanium, here [CpTi(cot)], has attracted interest as a spin qubit because of the long coherence time. Here the structural and chemical properties of [CpTi(cot)] on Au(111) are investigated at the monolayer level by experimental and computational methods. Scanning tunneling microscopy suggests that adsorption occurs in two molecular orientations, lying and standing, with a 3:1 ratio. XPS data evidence that a fraction of the molecules undergo partial electron transfer to gold, while our computational analysis suggests that only the standing molecules experience charge delocalization toward the surface. Such a phenomenon depends on intermolecular interactions that stabilize the molecular packing in the monolayer. This orientation-dependent molecule-surface hybridization opens exciting perspectives for selective control of the molecule-substrate spin delocalization in hybrid interfaces.


Asunto(s)
Electrones , Titanio , Propiedades de Superficie , Microscopía de Túnel de Rastreo/métodos , Adsorción
7.
J Am Chem Soc ; 144(37): 17086-17096, 2022 09 21.
Artículo en Inglés | MEDLINE | ID: mdl-36073906

RESUMEN

Chemodivergent synthetic methodologies enable the efficient introduction of structural diversity into high-value organic products via simple chemical alterations. In this regard, C-H activation and functionalization of pyridinoid azines are important transformations in the synthesis of many natural products, pharmaceuticals, and functional materials. Reflecting on azinyl nitrogen lone-pair steric repulsion, its tendency to irreversibly coordinate metal ion catalysts, and the electron deficiency of pyridine, C-H functionalization at the important α-position remains challenging. Thus, developing earth-abundant catalysts for α-selective azine mono-functionalization is an attractive target for chemical synthesis. Here, the selective organolanthanide-catalyzed α-mono-borylation of a diverse series of 18 pyridines is reported using Cp*2LuCH(TMS)2 (Cp* = η5-C5Me5) (TMS = SiMe3) and affording valuable precursors for subsequent functionalization. Experimental and theoretical mechanistic data reported here support the intermediacy of a C-H-activated η2-lanthanide-azine complex, followed by intermolecular α-mono-borylation via σ-bond metathesis. Notably, varying the lanthanide identity and substrate substituent electronic character promotes marked chemodivergence of the catalytic selectivity: smaller/more electrophilic lanthanide3+ ions and electron-rich substrates favor selective α-C-H functionalization, whereas larger/less electrophilic lanthanide3+ ions and electron-poor substrates favor selective B-N bond-forming 1,2-dearomatization. Such lanthanide series catalytic chemodivergence is, to our knowledge, unprecedented.


Asunto(s)
Productos Biológicos , Elementos de la Serie de los Lantanoides , Catálisis , Nitrógeno , Preparaciones Farmacéuticas , Piridinas/química
8.
Angew Chem Int Ed Engl ; 61(37): e202207316, 2022 Sep 12.
Artículo en Inglés | MEDLINE | ID: mdl-35785426

RESUMEN

Aluminas are strategic materials used in many major industrial processes, either as catalyst supports or as catalysts in their own right. The transition alumina γ-Al2 O3 is a privileged support, whose reactivity can be tuned by thermal activation. This study provides a qualitative and quantitative assessment of the hydroxyl groups present on the surface of γ-Al2 O3 at three different dehydroxylation temperatures. The principal [AlOH] configurations are identified and described in unprecedented detail at the molecular level. The structures were established by combining information from high-field 1 H and 27 Al solid-state NMR, IR spectroscopy and DFT calculations, as well as selective reactivity studies. Finally, the relationship between the hydroxyl structures and the molecular-level structures of the active sites in catalytic alkane metathesis is discussed.

9.
Acta Neurochir (Wien) ; 163(7): 2055-2061, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-32808087

RESUMEN

BACKGROUND AND OBJECTIVE: To describe our single-center experience in the treatment of cavernous internal carotid artery (ICA) acute bleeding with flow diverter stent (FDS), as a single endovascular procedure or combined with an endoscopic endonasal approach. METHODS: We analyze a case series of 5 patients with cavernous ICA acute bleeding, i.e., 3 iatrogenic, 1 post-traumatic, and 1 erosive neoplastic. After an immediate nasal packing to temporarily bleeding control, patients underwent digital subtraction angiography (DSA) to identify the site of the ICA injury. A concomitant balloon occlusion test (BOT) was performed, to exclude post-occlusive ischemic neurological damage. An FDS was placed with parallel intravenous infusion of abciximab in 3 cases and tirofiban in 2 cases. In two patients, an innovative "sandwich technique" combining the endovascular reconstruction with an extracranial intrasphenoidal cavernous ICA resurfacing with autologous flaps or grafts by endoscopic endonasal approach was performed. RESULTS: No patient had periprocedural ischemic-hemorrhagic complications. All patients had a regular clinical evolution, without general complications or new onset of focal neurological deficits. No further bleeding occurred in 3 patients, while 2 cases experienced a mild rebleeding in a period ranging from 5 to 15 days after the endovascular procedure. In these two cases, we proceeded with an endoscopic endonasal procedure to resurface the exposed ICA wall in the sphenoid sinus. CONCLUSIONS: Although the treatment of choice for cavernous ICA acute bleeding remains the occlusion of the injured vessel, in cases of poor hemodynamic compensation at the BTO, the endovascular FDS emergency placement can be effective. A combined endoscopic endonasal technique to support the extracranial side of the vessel using autologous flaps or grafts can be performed to prevent the risk of rebleeding.


Asunto(s)
Arteria Carótida Interna , Anciano , Angiografía de Substracción Digital , Traumatismos de las Arterias Carótidas , Arteria Carótida Interna/diagnóstico por imagen , Arteria Carótida Interna/cirugía , Procedimientos Endovasculares , Femenino , Humanos , Masculino , Persona de Mediana Edad , Stents/efectos adversos , Adulto Joven
10.
J Am Chem Soc ; 142(17): 8019-8028, 2020 04 29.
Artículo en Inglés | MEDLINE | ID: mdl-32250115

RESUMEN

Tris[N,N-bis(trimethylsilyl)amide]lanthanum (LaNTMS) is an efficient and selective homogeneous catalyst for the deoxygenative reduction of tertiary and secondary amides with pinacolborane (HBpin) at mild temperatures (25-60 °C). The reaction, which yields amines and O(Bpin)2, tolerates nitro, halide, and amino functional groups well, and this amide reduction is completely selective, with the exclusion of both competing inter- and intramolecular alkene/alkyne hydroboration. Kinetic studies indicate that amide reduction obeys an unusual mixed-order rate law which is proposed to originate from saturation of the catalyst complex with HBpin. Kinetic and thermodynamic studies, isotopic labeling, and DFT calculations using energetic span analysis suggest the role of a [(Me3Si)2N]2La-OCHR(NR'2)[HBpin] active catalyst, and hydride transfer is proposed to be ligand-centered. These results add to the growing list of transformations that commercially available LaNTMS is competent to catalyze, further underscoring the value and versatility of lanthanide complexes in homogeneous catalysis.

11.
Radiol Med ; 124(5): 438-443, 2019 May.
Artículo en Inglés | MEDLINE | ID: mdl-30600435

RESUMEN

INTRODUCTION: Varicocele is a relatively complex pathology that affects the pampiniform plexus of veins in the spermatic cord. Modern treatment involves both urological/surgical and interventional procedures. Our objective is to compare outcomes of conventional laparoscopic ligation (LL) and occluding balloon embolization (OBE) a percutaneous interventional procedure. MATERIALS AND METHODS: We treated retrospectively a total of 98 patients, divided in two cohorts; arm A with 48 and arm B with 50 patients. Arm A patients underwent LL, while arm B ones were treated in interventional radiology suite, via OBE method. No comorbidities were reported, especially scrotal ones. Hence, all patients have been asked to respect 3 and 6 months' follow-up, clinical examination and ultrasonography were performed. Age range of the entire sample: 15-45 years old, with average of 28 years. The study involved two European centers. We performed a comparative analysis (Fisher's test) of intra-operative time, hospitalization and patient's postoperative recovery time. RESULTS AND LIMITATIONS: Outcomes have been in line with the recent literature ones, allowing the occluding balloon embolization a small advantage for quicker operative average time, hospitalization needed and full recovery to normal activities for the patient. Main limitation was the unfeasibility of cost-effectiveness analysis due to national differences, limited sample and lack of complete semen analysis pre- and postoperative. CONCLUSION: Both OBE and LL are safe and effective procedures in the treatment of varicocele, conceding OBE a slight advantage in terms of hospital stay and full recovery to normal activity of patients.


Asunto(s)
Oclusión con Balón/métodos , Laparoscopía/métodos , Varicocele/terapia , Adolescente , Adulto , Humanos , Tiempo de Internación/estadística & datos numéricos , Ligadura , Masculino , Persona de Mediana Edad , Tempo Operativo , Estudios Retrospectivos , Resultado del Tratamiento
12.
Angew Chem Int Ed Engl ; 58(21): 7030-7034, 2019 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-30913365

RESUMEN

In principal, the direct copolymerization of ethylene with polar comonomers should be the most efficient means to introduce functional groups into conventional polyolefins but remains a formidable challenge. Despite the tremendous advances in group 4-centered catalysis for olefin polymerization, successful examples of ethylene + polar monomer copolymerization are rare, especially without Lewis acidic masking reagents. Here we report that certain group 4 catalysts are very effective for ethylene + CH2 =CH(CH2 )n NR2 copolymerizations with activities up to 3400 Kg copolymer mol-1 -Zr h-1 atm-1 , and with comonomer enchainment up to 5.5 mol % in the absence of masking reagents. Group 4 catalyst-amino-olefin structure-activity-selectivity relationships reflect the preference of olefin activation over free amine coordination, which is supported by mechanistic experiments and DFT analysis. These results illuminate poorly understood facets of d0 metal-catalyzed polar olefin monomer copolymerization processes.

13.
Radiol Med ; 123(11): 885-889, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30019107

RESUMEN

PURPOSE: The aim of our study is to verify VAS and patient compliance in the immediate post-procedural time, in patients undergoing UAE through radial approach versus femoral procedure. METHODS: Between January and September 2017, 30 consecutive patients (age range 28-47, average 32 years) were enrolled for the study. UAE was performed by two interventional radiologists with more than 10 years of experience and more than 100 cases of UAE done. Patients were divided into two groups: transfemoral approach (group a, n = 15 patients) and transradial approach (group b, n = 15 patients). After procedure, patients were questioned about the compliance using the questionnaire at 24 h and VAS rating at 6, 12, 18 and 24 h. RESULTS: The average of VAS in group b was lower than in group a in each evaluation at 6 h (p < 0.20), 12 h (p < 0.07), 18 h (p < 0.02) and 24 h (p < 0.22) on the basis of Mann-Whitney U test, however, without a clear scientific evidence. Also the compliance score at 24 h had better results in the group b (average 14.0, range 13.0-16.0) in comparison with group a (average 18.0, range 17.0-21.4) (p < 0.001). CONCLUSION: Transradial approach improves the compliance and VAS of patients undergone to UAE.


Asunto(s)
Arteria Femoral , Leiomioma/terapia , Cooperación del Paciente , Cuidados Posoperatorios , Arteria Radial , Embolización de la Arteria Uterina/métodos , Neoplasias Uterinas/terapia , Escala Visual Analógica , Adulto , Femenino , Humanos , Persona de Mediana Edad , Autoinforme , Factores de Tiempo
14.
Proc Natl Acad Sci U S A ; 110(2): 413-8, 2013 Jan 08.
Artículo en Inglés | MEDLINE | ID: mdl-23269836

RESUMEN

Structural characterization of the catalytically significant sites on solid catalyst surfaces is frequently tenuous because their fraction, among all sites, typically is quite low. Here we report the combined application of solid-state (13)C-cross-polarization magic angle spinning nuclear magnetic resonance ((13)C-CPMAS-NMR) spectroscopy, density functional theory (DFT), and Zr X-ray absorption spectroscopy (XAS) to characterize the adsorption products and surface chemistry of the precatalysts (η(5)-C(5)H(5))(2)ZrR(2) (R = H, CH(3)) and [η(5)-C(5)(CH(3))(5)]Zr(CH(3))(3) adsorbed on Brønsted superacidic sulfated alumina (AlS). The latter complex is exceptionally active for benzene hydrogenation, with ~100% of the Zr sites catalytically significant as determined by kinetic poisoning experiments. The (13)C-CPMAS-NMR, DFT, and XAS data indicate formation of organozirconium cations having a largely electrostatic [η(5)-C(5)(CH(3))(5)]Zr(CH(3))(2)(+)· · · AlS(-) interaction with greatly elongated Zr · · · O(AlS) distances of ~2.35(2) Å. The catalytic benzene hydrogenation cycle is stepwise understandable by DFT, and proceeds via turnover-limiting H(2) delivery to surface [η(5)-C(5)(CH(3))(5)]ZrH(2)(benzene)(+)· · · AlS(-) species, observable by solid-state NMR and XAS.


Asunto(s)
Hidrocarburos Aromáticos/química , Modelos Químicos , Modelos Moleculares , Resonancia Magnética Nuclear Biomolecular/métodos , Compuestos Organometálicos/química , Espectroscopía de Absorción de Rayos X/métodos , Adsorción , Óxido de Aluminio , Benceno/química , Isótopos de Carbono/química , Catálisis , Hidrogenación , Cinética , Estructura Molecular , Electricidad Estática , Propiedades de Superficie , Circonio
15.
Angew Chem Int Ed Engl ; 55(17): 5263-7, 2016 Apr 18.
Artículo en Inglés | MEDLINE | ID: mdl-26990244

RESUMEN

The single-site supported organozirconium catalyst Cp*ZrBz2 /ZrS (Cp*=Me5 C5 , Bz=benzyl, ZrS=sulfated zirconia) catalyzes the single-face/all-cis hydrogenation of a large series of alkylated and fused arene derivatives to the corresponding all-cis-cyclohexanes. Kinetic/mechanistic and DFT analysis argue that stereoselection involves rapid, sequential H2 delivery to a single catalyst-bound arene face, versus any competing intramolecular arene π-face interchange.

16.
J Am Chem Soc ; 137(21): 6770-80, 2015 Jun 03.
Artículo en Inglés | MEDLINE | ID: mdl-25884397

RESUMEN

Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2-WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS ≫ AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3(+)/ZrS(-), 83% > Cp*ZrMe2(+)/ZrS(-), 80% > Cp*ZrBz2(+)/ZrS(-), 67% > Cp*ZrPh2(+)/ZrS(-), 57%. For Cp*ZrBz2(+)/ZrS(-), which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2(+)/AlS(-) vs Cp*ZrMe2(+)/AlS(-). The combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the "cationic" metal center-anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns.

17.
Langmuir ; 31(39): 10693-701, 2015 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-26367250

RESUMEN

Organic thin film transistors (OTFTs) are multilayer field-effect transistors that employ an organic conjugated material as semiconductor. Several experimental groups have recently demonstrated that the insertion of an organic self-assembled monolayer (SAM) between the dielectric and the semiconductive layer is responsible for a sensible improvement of the OTFT performances in terms of an increased charge carrier mobility caused by a higher degree of order in the organic semiconductor layer. Here, we describe a combined periodic density functional theory (DFT) and classical molecular dynamics (MD) protocol applied to four different SAMs and a pentacene monolayer deposited onto their surfaces. In particular, we investigate the morphology and the surface of the four SAMs and the translational, orientational, and nematic order of the monolayer through the calculation of several distribution functions and order parameters pointing out the differences among the systems and relating them to known experimental results. Our calculations also suggest that small differences in the SAM molecular design will produce remarkable differences in the SAM surface and monolayer order. In particular, our simulations explain how a SAM with a bulky terminal group results in an irregular and rough surface that determines the deposition of a disordered semiconductive monolayer. On the contrary, SAMs with a small terminal group generate smooth surfaces with uninterrupted periodicity, thus favoring the formation of an ordered pentacene monolayer that increases the mobility of charge carriers and improves the overall performances of the OTFT devices. Our results clearly point out that the in silico procedure presented here might be of help in tuning the design of SAMs in order to improve the quality of OTFT devices.


Asunto(s)
Semiconductores , Simulación de Dinámica Molecular
18.
Proc Natl Acad Sci U S A ; 109(7): 2263-8, 2012 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-22308349

RESUMEN

A supramolecular approach for the specific detection of sarcosine, recently linked to the occurrence of aggressive prostate cancer forms, has been developed. A hybrid active surface was prepared by the covalent anchoring on Si substrates of a tetraphosphonate cavitand as supramolecular receptor and it was proven able to recognize sarcosine from its nonmethylated precursor, glycine, in water and urine. The entire complexation process has been investigated in the solid state, in solution, and at the solid-liquid interface to determine and weight all the factors responsible of the observed specificity. The final outcome is a Si-based active surface capable of binding exclusively sarcosine. The complete selectivity of the cavitand-decorated surface under these stringent conditions represents a critical step forward in the use of these materials for the specific detection of sarcosine and related metabolites in biological fluids.


Asunto(s)
Sarcosina/análisis , Silicio/química , Modelos Moleculares , Sarcosina/orina , Soluciones , Propiedades de Superficie
19.
J Am Chem Soc ; 136(29): 10460-9, 2014 Jul 23.
Artículo en Inglés | MEDLINE | ID: mdl-24984105

RESUMEN

The heterobimetallic complexes, (η(5)-indenyl)[1-Me2Si((t)BuN)TiCl2]-3-CnH2n-[N,N-bis(2-(ethylthio)ethyl)amine]CrCl3 (n = 0, Ti-C0-Cr(SNS); n = 2, Ti-C2-Cr(SNS); n = 6, Ti-C6-Cr(SNS)), (η(5)-indenyl)[1-Me2Si((t)BuN)TiCl2]-3-C2H4-[N,N-bis((o-OMe-C6H4)2P)amine]CrCl3 (Ti-C2-Cr(PNP)), and (η(5)-indenyl)[1-Me2Si((t)BuN)TiCl2]-3-C2H4-[N,N-bis((diethylamine)ethyl)-amine]CrCl3 (Ti-C2-Cr(NNN)), are synthesized, fully characterized, and employed as olefin polymerization catalysts. With ethylene as the feed and MAO as cocatalyst/activator, SNS-based complexes Ti-C0-Cr(SNS), Ti-C2-Cr(SNS), and Ti-C6-Cr(SNS) afford linear low-density polyethylenes (LLDPEs) with exclusive n-butyl branches (6.8-25.8 branches/1000 C), while under identical polymerization conditions Ti-C2-Cr(PNP) and Ti-C2-Cr(NNN) produce polyethylenes with heterogeneous branching (C2, C4, and C≥6) or negligible branching, respectively. Under identical ethylene polymerization conditions, Ti-C0-Cr(SNS) produces polyethylenes with higher activity (4.5× and 6.1×, respectively), Mn (1.3× and 1.8×, respectively), and branch density (1.4× and 3.8×, respectively), than Ti-C2-Cr(SNS) and Ti-C6-Cr(SNS). Versus a CGC(Et)Ti + SNSCr tandem catalyst, Ti-C0-Cr(SNS) yields polyethylene with somewhat lower activity, but with 22.6× higher Mn and 4.0× greater branching density under identical conditions. In ethylene +1-pentene competition experiments, Ti-C0-Cr(SNS) yields 5.5% n-propyl branches and 94.5% n-butyl branches at [1-pentene] = 0.1 M, and the estimated effective local concentration of 1-hexene is ∼8.6 M. In contrast, the tandem CGC(Et)Ti + SNSCr system yields 91.0% n-propyl branches under identical reaction conditions. The homopolymerization and 1-pentene competition results argue that close Ti···Cr spatial proximity together with weak C-H···Ti and C-H···S interactions significantly influence relative 1-hexene enchainment and chain transfer rates, supported by DFT computation, and that such effects are conversion insensitive but cocatalyst and solvent sensitive.


Asunto(s)
Alquenos/química , Cromo/química , Compuestos Organometálicos/química , Polietilenos/síntesis química , Titanio/química , Catálisis , Etilenos/química , Ligandos , Estructura Molecular , Compuestos Organometálicos/síntesis química , Polietilenos/química , Polimerizacion
20.
J Clin Med ; 13(3)2024 Jan 26.
Artículo en Inglés | MEDLINE | ID: mdl-38337426

RESUMEN

(1) Background: Conventional open surgery is still the gold standard for aortic arch disease, and despite recent developments in optimizing strategies for neuroprotection, distal organ perfusion, and myocardial protection, aortic arch replacement is still associated with high morbidity and mortality rates. (2) Methods: We present our case series of 12 patients undergoing surgical management of multiple cardiac diseases involving the aortic arch. In this single-center study, we report our initial experience over a five-year period (from December 2018 to October 2023) with the use of a "debranching first" technique for the supra-aortic vessels of a beating heart, followed by the cardiac step addressing proximal diseases, and a final distal step treating the aortic arch. This strategy aims to minimize cardiac, cerebral, and peripheral ischemia. (3) Results: Six patients underwent aortic root replacement with either Bentall (n = 4) or valve-sparing aortic root (David procedure) (n = 2). The mean nasopharyngeal temperature was 34 °C and the mean cardiocirculatory arrest was 14.3 min. The early mortality was 8.3% (1 patient); no patient experienced a permanent neurologic event. (4) Conclusions: In patients with complex aortic disease and concomitant cardiac disease, this approach reduces the need for hypothermia and decreases cardiopulmonary bypass time and myocardial arrest time and therefore could represent a valid surgical option, even in high-risk patients.

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