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1.
Pak J Med Sci ; 40(6): 1180-1184, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38952518

RESUMEN

Objective: To prove that the "sports rehabilitation bed" is a device aimed at improving the precision of stretching, which can help to reduce the difficulty of rehabilitation therapy, cut down the manpower input of rehabilitation therapy, and shorten the therapy duration as well. Methods: This was a clinical comparative study. Twenty patients who underwent stretching therapy in Sichuan Province Orthopedic Hospital from June 2020 to August 2020 were randomly selected to carry out a control study on both lower extremities. The experimental group was given sports rehabilitation bed to assist rehabilitation therapy, while the control group was given conventional bare-handed stretching rehabilitation therapy. The stretching angle, stretching value, and the effective rate of stretching therapy between the two groups to analyze the clinical value of the new sports rehabilitation therapy bed. Results: The stretching angle in the experimental group when using the sports rehabilitation therapy bed for stretching was lower than the conventional bare-handed stretching in the control group (T<0, P=0.05), with a statistically significant difference; the stretching values of the experimental group were lower than those of the control group(P<0.01), with a statistically significant difference. Moreover, the response rate of stretching therapy in the experimental group was lower than that in the control group(P<0.05), with a statistically significant difference. Conclusion: Sports rehabilitation therapy beds can results in the advantages of effectively preventing iatrogenic injury in the process of stretching, and providing a more accurate and convenient stretching therapy method than the current commonly used bare-handed stretching for sports rehabilitation and intervention.

2.
Nanotechnology ; 34(48)2023 Sep 14.
Artículo en Inglés | MEDLINE | ID: mdl-37647874

RESUMEN

Isotope engineering has been shown to be an effective means of regulating thermal conductivity. In this work, we studied the isotope engineering of thermal conductivity in bulk and 2D GaN, and diametrically opposite atom isotope dependence is found. That is, Ga isotope has a large effect (77%) on bulk GaN, while the effect of N isotope on the thermal conductivity is negligible. In 2D GaN, however, N isotope effect (20%) is more significant than that of Ga. Understanding of the different isotope dependence is achieved by deeper insight. Due to the relative magnitude of scattering rate, isotopic scattering influences the thermal conductivity of bulk and 2D GaN in different frequency regions, leading to the opposite atom dependence.

3.
Nature ; 541(7637): 371-375, 2017 01 19.
Artículo en Inglés | MEDLINE | ID: mdl-28002401

RESUMEN

Internal bases in mRNA can be subjected to modifications that influence the fate of mRNA in cells. One of the most prevalent modified bases is found at the 5' end of mRNA, at the first encoded nucleotide adjacent to the 7-methylguanosine cap. Here we show that this nucleotide, N6,2'-O-dimethyladenosine (m6Am), is a reversible modification that influences cellular mRNA fate. Using a transcriptome-wide map of m6Am we find that m6Am-initiated transcripts are markedly more stable than mRNAs that begin with other nucleotides. We show that the enhanced stability of m6Am-initiated transcripts is due to resistance to the mRNA-decapping enzyme DCP2. Moreover, we find that m6Am is selectively demethylated by fat mass and obesity-associated protein (FTO). FTO preferentially demethylates m6Am rather than N6-methyladenosine (m6A), and reduces the stability of m6Am mRNAs. Together, these findings show that the methylation status of m6Am in the 5' cap is a dynamic and reversible epitranscriptomic modification that determines mRNA stability.


Asunto(s)
Adenosina/análogos & derivados , Caperuzas de ARN/química , Caperuzas de ARN/metabolismo , Estabilidad del ARN , Adenosina/química , Adenosina/metabolismo , Dioxigenasa FTO Dependiente de Alfa-Cetoglutarato/metabolismo , Animales , Endorribonucleasas/metabolismo , Epigénesis Genética , Guanosina/análogos & derivados , Guanosina/metabolismo , Células HEK293 , Semivida , Humanos , Masculino , Metilación , Ratones , MicroARNs/genética , MicroARNs/metabolismo , Especificidad por Sustrato , Sitio de Iniciación de la Transcripción , Transcriptoma
4.
Cereb Cortex ; 32(7): 1494-1507, 2022 03 30.
Artículo en Inglés | MEDLINE | ID: mdl-34467373

RESUMEN

Homozygous mutations in the gene encoding the scavenger mRNA-decapping enzyme, DcpS, have been shown to underlie developmental delay and intellectual disability. Intellectual disability is associated with both abnormal neocortical development and mRNA metabolism. However, the role of DcpS and its scavenger decapping activity in neuronal development is unknown. Here, we show that human neurons derived from patients with a DcpS mutation have compromised differentiation and neurite outgrowth. Moreover, in the developing mouse neocortex, DcpS is required for the radial migration, polarity, neurite outgrowth, and identity of developing glutamatergic neurons. Collectively, these findings demonstrate that the scavenger mRNA decapping activity contributes to multiple pivotal roles in neural development and further corroborate that mRNA metabolism and neocortical pathologies are associated with intellectual disability.


Asunto(s)
Endorribonucleasas , Neurogénesis , Animales , Humanos , Ratones , Proyección Neuronal , ARN Mensajero
5.
Med Sci Monit ; 29: e939309, 2023 May 28.
Artículo en Inglés | MEDLINE | ID: mdl-37245072

RESUMEN

BACKGROUND Lateral epicondylitis is a common clinical disease characterized by lateral elbow pain, seriously affecting patients' daily life and work. There is a lack of comprehensive and systematic visual analysis of the literature in this field. Therefore, we analyzed the literature on lateral epicondylitis in the past 30 years and summarized the hot spots and frontiers of research in this field to provide ideas and references for subsequent researchers. MATERIAL AND METHODS CiteSpace, VOSviewer, and R-Bibliometrix tools were primarily used to collect, visualize, and analyze data from the literature on lateral epicondylitis in the Web of Science database's core dataset from 1990 to 2022. RESULTS There were altogether 1556 items in the literature. Recent years have seen a noticeable development trend in the volume of pertinent literature that is published annually. The United States took first place with 447 papers. Univ Queensland ranked first with 42 papers. Vicenzino B, an academic at the University of Queensland, Australia, ranked first, with 48 papers. CONCLUSIONS Yearly volumes and forecasts suggest the USA will continue to lead the world in publications on lateral epicondylitis, with extensive collaboration among authors. More collaboration is still needed in various nations and organizations, according to an analysis of the research literature from the previous 30 years. The mechanism of action of different injectable preparations, such as corticosteroids for the treatment of LE is still unclear, as well as the cellular transduction pathways through which PRP affects LE.


Asunto(s)
Codo de Tenista , Humanos , Bibliometría , Artralgia , Australia , Dolor
6.
BMC Musculoskelet Disord ; 24(1): 896, 2023 Nov 18.
Artículo en Inglés | MEDLINE | ID: mdl-37980477

RESUMEN

BACKGROUND: Patellofemoral pain (PFP) is one of the most common disorders of the knee joint. Home-based exercise is an effective intervention to achieve self-management for chronic diseases. This study evaluated the effects of home-based exercise and health education in patients with PFP. METHODS: Patients who had PFP were randomly allocated to an intervention group (IG) or control group (CG). Patients in the IG received a 6-week tailored home-based exercise program with health education via remote support, while patients in the CG group only received health education. Clinical outcomes were compared using the Anterior Knee Pain Scale (AKPS) to measure function and the Visual Analog Scale (VAS) to measure "worst pain" and "pain with daily activity". Muscle strength was measured according to the peak torque of the knee muscles using an isokinetic system. RESULTS: Among a total of 112 participants screened for eligibility, 38 were randomized and analyzed, including 19 participants in the intervention group and 19 participants in the control group. There were no significant differences in baseline characteristics between the groups. At 6-week follow-up, the intervention group showed a greater worst pain reduction (between-group difference, -19.3 [95%CI, -23.2 to -15.5]; P < 0.01) and pain with daily activity (between-group difference, -22.9 [95%CI, -28.3 to -17.4]; P < 0.01) than the control group. Similarly, the intervention group had better improvements in AKPS (between-group difference, 9.0 [95%CI, 4.1 to 13.9]; P < 0.01) and knee extensor strength (between-group difference, 20.1 [95%CI, 14.5 to 25.8]; P < 0.01), compared to the control group. No adverse events were reported. CONCLUSION: Home-based exercise and health education resulted in less pain, better function, and higher knee muscle strength compared with no exercise in patients with PFP. A large randomized controlled trial with long-term follow-up is required to confirm these findings. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR2200056224 ( https://www.chictr.org.cn/showproj.aspx?proj=135506 ). Registered on February 1, 2022.


Asunto(s)
Síndrome de Dolor Patelofemoral , Humanos , Síndrome de Dolor Patelofemoral/diagnóstico , Síndrome de Dolor Patelofemoral/terapia , Terapia por Ejercicio/métodos , Articulación de la Rodilla , Rodilla , Dolor
7.
Nanotechnology ; 33(19)2022 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-35086083

RESUMEN

Quantum dot (QD) features many exceptional optical performances but is also vulnerable to moisture which results in structural damage and luminescent decrease. This work provided and fabricated a novel superior hydrophobic methylated core/shell silica-coated QD (MSQ) for high water stability. QD was coated with a silica shell and then surface-methylated by trimethyl silane. Mercaptopropyl trimethoxy silane, tetraethyl orthosilicate, and ethoxy trimethyl silane were utilized as the ligand exchanger, the raw material of silica, and the surface modification, respectively. Characterization results illustrated the core/shell structure of MSQ. In addition, its water contact angle was up to 159.6°. QD-, silica-coated QD(SQ)-, and MSQ-silicone were made and displayed similar absorption, emission, and excitation spectra but different water stabilities. The photoluminescence intensity and photoluminescence quantum yield of MSQ-silicone hardly changed during 15 d of water immersion, in contrast to the dramatical decrease of other two kinds of composite silicone. Specifically, the photoluminescence quantum yield decreases of MSQ-, SQ-, and QD-silicone were 1%, 40%, and 43%, respectively. Therefore, MSQ had a much better water stability. The superior hydrophobic methylated silica-coated QD has a great potential to realize the long-term working stability in a humid environment and the wider application in diverse fields.

8.
Nanotechnology ; 33(46)2022 Aug 30.
Artículo en Inglés | MEDLINE | ID: mdl-35926438

RESUMEN

Quantum dots (QDs) are facing significant photoluminescence degradation in moisture environment. In QDs-silicone composites, the poor water resistance of silicone matrix makes it easy for water and oxygen molecules to erode QDs. To tackle this issue, we proposed a new QDs protection strategy by introducing short-chain silica precursors onto the QDs' surface, so that a dense silica passivation layer could be formed onto the QDs nanoparticles. Sol-gel method based on 3-aminopropyl triethoxysilane (APTES), 3-mercaptopropyl trimethoxysilane (MPTMS), and 3-mercaptopropyl triethoxysilane (MPTES) were adopted to prepare the uniform and crack-free QDs-silica glass (QD-glass). Because of the crosslinking of short-chain precursors, the formed silica glass possesses 38.6% smaller pore width and 68.6% lower pore volume than silicone, indicating its denser cross-linked network surrounding QDs. After 360 h water immersion, the QDs-glass demonstrated a 6% enhancement in red-light peak intensity, and maintained a stable full width at half maximum (FWHM) and peak wavelength, proving its excellent water-resistant ability. However, the conventional QDs-silicone composites not only showed a decrease of 75.3% in red-light peak intensity, but also a broadened FWHM and a redshifted peak wavelength after water immersion. QDs-glass also showed superior photostability after 132 h exposure to blue light. Red-light peak intensity of QDs-glass remained 87.3% of the initial while that of QDs-silicone decreased to 19.8%. And the intensity of QDs-glass dropped to 62.3% of that under 20 °C after thermal treatment of 160 °C. Besides, under increasing driving currents, the light conversion efficiency drop of QDs-glass is only one fifth that of QDs-silicone. Based on the QDs-glass, the white light-emitting diodes was achieved with a high luminous efficiency of 126.5 lm W-1and a high color rendering index of 95.4. Thus, the newly proposed QD-glass has great significance in guaranteeing the working reliability of QDs-converted devices against moisture and high-power environment.

9.
Phys Chem Chem Phys ; 24(36): 21638-21644, 2022 Sep 21.
Artículo en Inglés | MEDLINE | ID: mdl-36063076

RESUMEN

Although considered as promising candidates for lithium-ion secondary batteries, spinel LiMn2O4 cathodes suffer from significant capacity decay owing to the Jahn-Teller effect, dissolution of Mn and lattice oxygen loss during the charge/discharge process, preventing their wider use. In this work, we realize that F-doping at small concentrations could improve the battery voltage and reduce the capacity decay using an atomistic model. For voltage, F-doping improves the voltage to about 4.4 eV under large delithiation. For capacity decay, it retards capacity decay owing to the reduced lattice oxygen loss. The larger Gibbs free energy of oxygen release after F-doping indicates harder lattice oxygen loss. In addition, although F-doping makes the average valence of Mn lower, the existence of Mn4+ during delithiation exerts a positive effect by reducing the Jahn-Teller effect. However, since the Mn3+ ions in the spinel structure could induce Jahn-Teller distortion, the effect of F-doping on Jahn-Teller distortion is determined by the competition between Mn4+ and Mn3+. The atomistic mechanism of F-doping in the performance of LiMn2O4 offers new insight in developing spinel lithium manganese oxide cathode materials with superior performance.

10.
Phys Chem Chem Phys ; 24(31): 18722-18728, 2022 Aug 10.
Artículo en Inglés | MEDLINE | ID: mdl-35899833

RESUMEN

We perform a theoretical exploration of quantum coherent control of enantio-selective state transfer (ESST) of chiral molecules with three rotational states connected by the a-type, b-type, and c-type components of the transition dipole moments. A pulse-area theorem based on a closed-loop three-level system is derived without applying the rotating-wave approximation and used to analytically design three linearly polarized microwave pulses with optimal amplitudes and phases. By utilizing two optimized microwaves to mix two excited rotational states into the maximal coherence, we find that the discrimination of enantiomers via ESST for chiral molecules can be achieved by controlling the delay time of the third optimized microwave pulse. We examine the robustness of such control schemes against the Rabi frequency and detuning errors and the environment effect through pure dephasing processes for practical applications. This work provides an alternative approach to analytically designing optimal control fields for quantum control of ESST by using complex pulse areas.

11.
J Mater Sci Mater Med ; 33(7): 57, 2022 Jun 23.
Artículo en Inglés | MEDLINE | ID: mdl-35737197

RESUMEN

Antibacterial activity is one of the most vital characteristics for Titanium (Ti) dental implants. Coating antibacterial material onto Ti surfaces is an effective approach to enhance their intrinsic antibacterial ability. However, a cost-effective but efficient coating strategy for realizing this objective still remains challenging. In this study, we proposed a novel implant surface modification strategy for coating silver nanoparticles onto the porous Ti surface via a facile electron beam evaporation (EBE) approach. Porous Ti surfaces were firstly prepared by sand-blasting large grit acid-etching (SLA) process. Then, the silver nanoparticles coating thickness on the porous Ti surface was adjusted and optimized by altering the duration of EBE process. Consequently, composite porous Ti surfaces with different silver thicknesses were synthesized. Polished Ti (PT) surface without SLA or EBE process was also prepared as the controlled blank group. The surface characterizations were analyzed by SEM, AFM, and XPS. After that, the antibacterial properties of all groups were tested with bacteria counting method, bacterial viability test, live/dead bacterial staining, and SEM examination. Results show that silver nanoparticles were uniformly distributed on the porous Ti surfaces after the SLA and EBE processes. After being incorporated with silver nanoparticles, the composite surfaces successfully inhibited the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The antibacterial ratio (AR) values of SLA-Ag groups increased with the increasing silver thickness and are significantly higher than those of PT and SLA groups. Therefore, by the SLA and EBE processes, the composite porous Ti surfaces modified with silver nanoparticles coatings demonstrate superior antibacterial property compared with pure Ti surfaces, which is highly promising for enhancing the antibacterial functions of dental implants. Graphical abstract.


Asunto(s)
Implantes Dentales , Nanopartículas del Metal , Antibacterianos/farmacología , Materiales Biocompatibles Revestidos/farmacología , Electrones , Escherichia coli , Porosidad , Plata/farmacología , Staphylococcus aureus , Propiedades de Superficie , Titanio/farmacología
12.
Opt Lett ; 46(4): 888-891, 2021 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-33577540

RESUMEN

Narrowband mid-infrared emitters, quantified by the Q-factor, have garnered a lot of attention due to their emerging applications from chemical and biosensing to efficient thermal utilization. Previous studies reported high Q-factor emitters within several selected wavelengths, still lacking a large database of emitter structures with very high Q-factors. In this Letter, we utilized the Monte Carlo Tree Search (MCTS) algorithm under the framework of material informatics to optimize the Tamm emitters at the infrared range (from 3 to 10 µm) for achieving a high Q-factor and high emissivity simultaneously, providing a large database of high and sharp emission peaks in the infrared. Through the MCTS algorithm, the structure with a Q-factor of 508 and an emissivity peak of 0.92 at 4.225 µm is obtained, far surpassing the previous results, and the underlying mechanism is discussed by electric field simulations. The high Q-factor emitters in the database show good monochromatism and high emissivity, accelerating the selection of proper perfect emitters for desired wavelengths. This Letter also paves a feasible avenue for the emitter and absorber design with ultrahigh monochromatism.

13.
Langmuir ; 37(44): 13099-13106, 2021 11 09.
Artículo en Inglés | MEDLINE | ID: mdl-34705469

RESUMEN

Multicompartment micelles (MCMs) attracted much attention since they have subdivided domains that could be employed to encapsulate and transport diverse compounds simultaneously. Usually, preparation of MCMs relied on precise synthesis of block copolymers (BCPs) and elegant control of assembly kinetics, making it difficult to successively produce MCMs. Herein, we report a facile yet effective method for preparing MCMs by adjusting the hydrodynamics in microfluidic channels. It was found that well-defined MCMs were formed through hydrodynamics-dependent secondary assembly in microfluidic chips. By adjusting the flow diffusion process by varying the flow rate ratio and total flow rate, both the internal structure and size of MCMs could be effectively changed. A product diagram of micellar morphologies associated to the initial polymer concentration and flow rate ratio of water/BCPs solution was constructed. More interestingly, quantum dots (QDs) could be selectively loaded into different domains of the MCMs. Consequently, the Förster resonance energy transfer among QDs could be effectively suppressed. Thus, the emission spectrum of MCMs/QDs hybrid particles could be easily tuned by changing the ratio of QDs, showing great potential application in photonics and sensors.


Asunto(s)
Micelas , Puntos Cuánticos , Hidrodinámica , Microfluídica , Polímeros
14.
Phys Chem Chem Phys ; 23(9): 5431-5437, 2021 Mar 11.
Artículo en Inglés | MEDLINE | ID: mdl-33646234

RESUMEN

Two-dimensional (2D) gallium nitride (GaN) has attracted a lot of attention due to its promising applications in photoelectric nano-devices. Most previous research studies have focused on polar c-plane 2D structures. Here, by employing first principles calculations, we systematically investigate the structural and electronic properties of non-polar m-plane GaN with different numbers of atomic layers. The results show a layer-dependent structure transition and electronic band variation for m-plane GaN. It is found that the monolayer keeps a planar hexagonal structure due to sp2 hybridization, whereas the multilayers are formed by stacking of buckled hexagonal monolayers with unsaturated coordination number at the surface sublayer and bulk-like inner layers. These discrepancies in the structure further induce an indirect to direct transition of the band gap type when the layer number reaches twelve. By carefully examining the relationship between the structure and electronic bandgap, we find that the indirect bandgap comes from the unsaturated surface with a planar like structure. On surface modification, saturation of the surface dangling bonds results in an indirect to direct band gap transition.

15.
Appl Opt ; 60(2): 306-311, 2021 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-33448953

RESUMEN

Lens arrays are introduced to diminish the total internal reflection (TIR) that happens at chip-encapsulant and encapsulant-air interfaces of chip-on-board light-emitting diodes (COB-LEDs), so as to improve the light extraction efficiency (LEE) of the COB-LEDs. However, the LEE of COB-LEDs with lens array depends on the refractive index of the encapsulant layer nencap and lens array nlens, which was rarely concerned so far. Optical simulations based on a Monte Carlo ray tracing method, and experiments were conducted to investigate the effect of nencap and nlens on the LEE of COB-LEDs with millilens array. The simulated results show that the TIR at chip-encapsulant, encapsulant-lens, and lens-air interfaces can be significantly diminished by regulating the nencap and nlens, and the LEE of COB-LEDs decreases as the refractive difference of encapsulant layer and lens array |nlens-nencap| increases. Compared to the COB-LEDs with only a flat encapsulant layer, the LEEs of blue and white COB-LEDs with nlens=nencap=nITO=2 are enhanced by 246.2% and 50.6%, where nITO is the refractive index of the top layer of the conventional LED chip. The experimental results agree well with the simulated results with normalized LEE deviation within 7.3%.

16.
Opt Express ; 28(2): 875-885, 2020 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-32121808

RESUMEN

Thanks to the conductive thermal metamaterials, novel functionalities like thermal cloak, camouflage and illusion have been achieved, but conductive metamaterials can only control the in-plane heat conduction. The radiative thermal metamaterials can control the out-of-plane thermal emission, which are more promising and applicable but have not been studied as comprehensively as the conductive counterparts. In this paper, we theoretically investigate the surface emissivity of metal/insulator/metal (MIM, i.e., Au/Ge/Au here) microstructures, by the rigorous coupled-wave algorithm, and utilize the excitation of the magnetic polaritons to realize thermal camouflage through designing the grating width distribution by minimizing the temperature standard deviation of the overall plate. Through this strategy, the hot spot in the original temperature field is removed and a uniform temperature field is observed in the infrared camera instead, demonstrating the thermal camouflage functionality. Furthermore, thermal illusion and thermal messaging functionalities are also demonstrated by resorting to using such an emissivity-structured radiative metasurface. The present MIM-based radiative metasurface may open avenues for developing novel thermal functionalities via thermal metasurface and metamaterials.

17.
Opt Express ; 28(23): 34167-34179, 2020 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-33182892

RESUMEN

Quantum dot light-emitting diodes (QLEDs) possess huge potential in display due to their outstanding optoelectronic performance; however, serve degradation during operation blocks their practical applications. High temperature is regarded as one of major factors causing degradation. Therefore, a systematical study on the working temperature of QLEDs is very essential and urgent for the development of high stable QLEDs. In this work, different influence factors such as the electro-optic conversion efficiency (EOCE), voltage, current density, active area, substrate size, substrate type and sample contact are discussed in detail on the working temperature of QLEDs. The research results show that the working temperature of general QLEDs under normal operation conditions is usually smaller than 75 °C when the ambient temperature is 25 °C. However, temperature of QLEDs working under extreme conditions, such as high power or small substrate size, will exceed 100 °C, resulting in irreversible damage to the devices. Moreover, some effective measures to reduce the working temperature are also proposed. The analysis and discussion of various influencing factors in this work will provide guidance for the design of stable QLEDs and help them work at a safer temperature.

18.
Langmuir ; 36(19): 5377-5384, 2020 May 19.
Artículo en Inglés | MEDLINE | ID: mdl-32345020

RESUMEN

Self-assembly of block copolymers (BCPs) in microfluidic chips is a versatile yet effective route to produce micellar aggregates with various controllable sizes and morphologies. In this study, the morphological transformation of the BCP of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) assemblies from irregular aggregates to multicompartment micelles and ultimately to ordered spherical micelles is demonstrated in microfluidic chips. Our experimental and computational simulation results indicate that the transverse diffusion of solvents plays an important role in the morphological transformation of PS-b-P4VP assemblies in the confined flow condition. We find that the mixing time (tmix) between a BCP/tetrahydrofuran (THF) solution and water affects the morphological transformation. Micellar morphologies are intended to transform from aggregates to ordered spherical structures under a relatively long mixing time (tmix). In addition, it is observed that the size of the micelles decreases with the increase of the flow velocity ratio by tuning the hydrodynamic conditions of the flows. Moreover, by adjusting the initial polymer solution concentration, temperature, and weight fraction of the introduced homopolystyrene (hPS), which can affect the viscosity of the BCP solution, the flow diffusion in the microfluidic chip and the resulted micellar structures can also be readily adjusted. The current study provides a new flow-driven method to adjust the micellar ordered structural transformation under the nonequilibrium state.

19.
Langmuir ; 35(1): 141-149, 2019 01 08.
Artículo en Inglés | MEDLINE | ID: mdl-30507203

RESUMEN

Kinetically controlled self-assembly of block copolymers (BCPs) in solution is an efficient route to fabricate complex hierarchical colloids which are of great importance for nanoencapsulation, microreactors, and biomimics. Herein, segmented wormlike micelles (SWMs) with controllable size are generated by the self-assembly of polystyrene- block-poly(4-vinyl pyridine) in microfluidic channel. Different from the assembly of BCPs off-chip at the same solution properties, it is found that the fabricated SWMs are kinetically controlled assemblies with thermodynamic metastable structures, which are formed by the orderly aggregation of preformed spherical micelles because of the fast mixing process in microfluidic channels. Moreover, by manipulating the total flow velocity of water and BCPs solution or their flow velocity ratio, both of the percentages of SWMs among the whole assemblies and their sizes can be effectively tuned. On the basis of electron microscopy and dynamic light scatting investigations, a product diagram of micellar morphologies associated to initial polymer concentration and flow velocity ratio of water/BCPs solution was constructed, which is important for the rational design and fabrication of complex hierarchical BCP colloids.

20.
Soft Matter ; 15(21): 4320-4325, 2019 May 29.
Artículo en Inglés | MEDLINE | ID: mdl-31070662

RESUMEN

Droplet impingement on heated surfaces has been investigated by varying the surface textures, temperature, and droplet properties with demonstration of various phenomenological behaviors, such as evaporation, boiling, splashing, and Leidenfrost bouncing. However, the ambient pressure dependence has not been well explored, especially for ambient pressures lower than 5 kPa. By examining the ambient pressure (from 0.2 to 20 kPa) and surface temperature (from 20 to 200 °C) simultaneously, we found a novel explosive bouncing behavior which is different from Leidenfrost bouncing and only occurs at extremely low ambient pressure (≤6 kPa). Through experimental validation and mechanical analysis, we found that the explosive bouncing is caused by the dramatic explosion of the local vapor bubble and reducing the ambient pressure benefits the formation and explosion of the vapor bubble.

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