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1.
Appl Opt ; 63(3): 595-603, 2024 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-38294369

RESUMEN

The cost function in the iterative optimization algorithms is one of the sensitive optimization controllers that plays a crucial role in feedback based wavefront shaping for constructing well-resolved complex structured light through scattering media. There has been a trade-off between resolution and the contrast enhancement of the structured light in wavefront shaping. We have developed an ℓ 2-norm based quadratic cost function (L2QN) and proposed a regularized cost function (RCF) for advancing the contrast and maintaining the high resolution of structured light. Both the simulations and experiments have been performed, and it has been found that the proposed RCF significantly advances the contrast and structural uniformity for focusing light through scattering media as well as for diffused reflection mode. The potential applications of the method demonstrated in this study can be extended into holographic displays, structured light illumination microscopy, photo-lithography, photothermal treatments, dosimetry, laser materials processing, and energy control inside and outside an incubation system.

2.
Kardiologiia ; 62(3): 40-48, 2022 Mar 31.
Artículo en Inglés | MEDLINE | ID: mdl-35414360

RESUMEN

Aim    The objective was to assess the correlation of fasting plasma glucose (FPG), HbA1c, and the duration of type 2 diabetes mellitus (T2DM) with SYNTAX score (SS) II in patients with non-ST elevation myocardial infarction (NSTEMI).Material and methods    FPG and HbA1C were measured in 398 patients presenting with NSTEMI at admission. SS II was calculated using an online calculator. Patients were stratified according to SS II (≤21.5, 21.5-30.6, and ≥30.6), defined as SS II low, mid, and high, respectively.Results    37.7 % of subjects were diabetic. Correlations of FPG (R=0.402, R2=0.162, p<0.001) and HbA1c (R=0.359, R2=0.129, p<0.001) with SS II were weak in the overall population. Duration of T2DM showed very strong correlation with SS II (R=0.827, R2=0.347). For the prediction of high SS II in the study population, FPG≥98.5 mg / dl demonstrated a sensitivity of 58 % and a specificity of 60 %, and HbA1c ≥6.05 demonstrated a sensitivity of 63 % and a specificity of 69 %. Duration of T2DM (adjusted odds ratio (OR): 1.182; 95 % confidence interval (CI): 1.185-2.773) and FPG (OR: 0.987; 95 % CI: 0.976-0.9959) were significantly associated with high SS II after controlling for other risk factors. Duration of T2DM (Beta=0.439) contributed strongly to variance of SS II, whereas HbA1c (Beta=0.063) contributed weakly.Conclusion    Duration of T2DM is a very important risk factor for severity of coronary artery disease.


Asunto(s)
Enfermedad de la Arteria Coronaria , Diabetes Mellitus Tipo 2 , Infarto del Miocardio sin Elevación del ST , Glucemia , Enfermedad de la Arteria Coronaria/diagnóstico , Enfermedad de la Arteria Coronaria/etiología , Diabetes Mellitus Tipo 2/complicaciones , Diabetes Mellitus Tipo 2/diagnóstico , Hemoglobina Glucada , Humanos , Infarto del Miocardio sin Elevación del ST/diagnóstico , Infarto del Miocardio sin Elevación del ST/etiología , Factores de Riesgo
3.
Phys Rev Lett ; 126(9): 097201, 2021 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-33750154

RESUMEN

The quasi-two-dimensional Mott insulator α-RuCl_{3} is proximate to the sought-after Kitaev quantum spin liquid (QSL). In a layer of α-RuCl_{3} on graphene, the dominant Kitaev exchange is further enhanced by strain. Recently, quantum oscillation (QO) measurements of such α-RuCl_{3} and graphene heterostructures showed an anomalous temperature dependence beyond the standard Lifshitz-Kosevich (LK) description. Here, we develop a theory of anomalous QO in an effective Kitaev-Kondo lattice model in which the itinerant electrons of the graphene layer interact with the correlated magnetic layer via spin interactions. At low temperatures, a heavy Fermi liquid emerges such that the neutral Majorana fermion excitations of the Kitaev QSL acquire charge by hybridizing with the graphene Dirac band. Using ab initio calculations to determine the parameters of our low-energy model, we provide a microscopic theory of anomalous QOs with a non-LK temperature dependence consistent with our measurements. We show how remnants of fractionalized spin excitations can give rise to characteristic signatures in QO experiments.

4.
Phys Rev Lett ; 126(13): 132502, 2021 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-33861122

RESUMEN

Isotopic distributions of fragments from fission of the neutron-deficient ^{178}Hg nuclide are reported. This experimental observable is obtained for the first time in the region around lead using an innovative approach based on inverse kinematics and the coincidence between the large acceptance magnetic spectrometer VAMOS++ and a new detection arm close to the target. The average fragment N/Z ratio and prompt neutron M_{n} multiplicity are derived and compared with current knowledge from actinide fission. A striking consistency emerges, revealing the unexpected dominant role of the proton subsystem with atomic number between the Z=28 and 50 magic numbers. The origin of nuclear charge polarization in fission and fragment deformation at scission are discussed.

5.
Phys Rev Lett ; 126(15): 152701, 2021 Apr 16.
Artículo en Inglés | MEDLINE | ID: mdl-33929230

RESUMEN

The discrepancy between observations from γ-ray astronomy of the ^{60}Fe/^{26}Al γ-ray flux ratio and recent calculations is an unresolved puzzle in nuclear astrophysics. The stellar ß-decay rate of ^{59}Fe is one of the major nuclear uncertainties impeding us from a precise prediction. The important Gamow-Teller strengths from the low-lying states in ^{59}Fe to the ^{59}Co ground state are measured for the first time using the exclusive measurement of the ^{59}Co(t,^{3}He+γ)^{59}Fe charge-exchange reaction. The new stellar decay rate of ^{59}Fe is a factor of 3.5±1.1 larger than the currently adopted rate at T=1.2 GK. Stellar evolution calculations show that the ^{60}Fe production yield of an 18 solar mass star is decreased significantly by 40% when using the new rate. Our result eliminates one of the major nuclear uncertainties in the predicted yield of ^{60}Fe and alleviates the existing discrepancy of the ^{60}Fe/^{26}Al ratio.

6.
Pramana ; 95(2): 64, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33897090

RESUMEN

Cosmic ray muon flux is measured by the coincidence technique using plastic scintillation detectors in the High Energy Physics Detector Laboratory at Bose Institute, Kolkata. Due to the COVID-19 outbreak and nationwide complete lockdown, the laboratory was closed from the end of March 2020 till the end of May 2020. After lockdown, although the city is not in its normal state, we still were able to take data on some days. The lockdown imposed a strict restriction on the transport service other than the emergency ones and also most of the industries were shut down in and around the city. This lockdown has significant effect on the atmospheric conditions in terms of change in the concentration of air pollutants. We have measured the cosmic ray flux before and after the lockdown to observe the apparent change if any, due to change in the atmospheric conditions. In this article, we report the measured cosmic ray flux at Kolkata (22.58 ∘ N 88.42 ∘ E and 11 m above the Sea Level) along with the major air pollutants present in the atmosphere before and after the lockdown.

7.
Nanotechnology ; 31(49): 495205, 2020 Dec 04.
Artículo en Inglés | MEDLINE | ID: mdl-32990266

RESUMEN

A set of nanocomposite films of poly-vinyl alcohol (PVA) and 0.1-0.4 wt% CdSe nanoparticles (NPs) were developed by spin coating and their surface resistance (R) was measured as a function of light illumination intensity (IL ) and applied magnetic field (H). The ferromagnetic CdSe NPs were synthesized by a facile chemical method which ensured in situ surface stabilization with a skinny layer of graphitic carbon. The CdSe NPs were uniformly dispersed in an aqueous solution of 2.0 wt% PVA and spin-coated on fluorine-doped tin oxide coated glass substrates. The photoresponse of the nanocomposite films at low H exhibits their efficacy for pertinent applications in optoelectronics.

8.
Phys Rev Lett ; 123(9): 092503, 2019 Aug 30.
Artículo en Inglés | MEDLINE | ID: mdl-31524478

RESUMEN

A direct and complete measurement of isotopic fission-fragment yields of ^{239}U has been performed for the first time. The ^{239}U fissioning system was produced with an average excitation energy of 8.3 MeV in one-neutron transfer reactions between a ^{238}U beam and a ^{9}Be target at Coulomb barrier energies. The fission fragments were detected and isotopically identified using the VAMOS++ spectrometer at the GANIL facility. The measurement allows us to directly evaluate the fission models at excitation energies of fast neutrons, which are relevant for next-generation nuclear reactors. The present data, in agreement with model calculations, do not support the recently reported anomaly in the fission-fragment yields of ^{239}U, and they confirm the persistence of spherical shell effects in the Sn region at excitation energies exceeding the fission barrier by a few mega-electron volts.

9.
Nanotechnology ; 30(38): 385203, 2019 Sep 20.
Artículo en Inglés | MEDLINE | ID: mdl-31216518

RESUMEN

Electrostatically actuated nanobeam-based electromechanical switches have shown promise for versatile novel applications, such as low power devices. However, their widespread use is restricted due to poor reliability resulting from high jump-in voltages. This article reports a new method for lowering the jump-in voltage by inducing mechanical oscillations in the active element during the switching ON process, reducing the jump-in voltage by more than three times. Ge0.91Sn0.09 alloy and Bi2Se3 nanowire-based nanoelectromechanical switches were constructed in situ to demonstrate the operation principles and advantages of the proposed method.

10.
Clin Radiol ; 74(1): 78.e1-78.e11, 2019 01.
Artículo en Inglés | MEDLINE | ID: mdl-30274684

RESUMEN

AIM: To evaluate whether a dedicated epilepsy research protocol with expert image re-evaluation can increase identification of patients with lesions and to attempt to ascertain the potential reasons why lesions were not identified previously on earlier clinical magnetic resonance imaging (MRI). MATERIALS AND METHODS: Forty-three patients (26 female) with focal refractory epilepsy who had failed at least two trials of anti-epileptic drug treatments were studied. Patients were recruited prospectively into the study if previous clinical MRI was deemed to be "non-lesional" by the clinicians involved in the initial assessment. Three-dimensional (3D) T1-weighted (T1W), T2-weighted (T2W), T2 fluid-attenuated inversion recovery (T2-FLAIR) sequences, and two-dimensional (2D) coronal T1-/T2W FLAIR were assessed by a neuroradiologist, including the previous clinical MRI of individual patients. RESULTS: Twenty-nine or 43 (67%) patients remained MRI-negative after scanning with the epilepsy-dedicated protocol and image reappraisal by expert consultant neuroradiologists; however, 14/43 (33%) patients were found to have potentially epileptogenic brain lesions. The lesion that most frequently escaped the attention of clinicians was hippocampal sclerosis (nine cases, of which two had an additional focal cortical dysplasia, FCD), followed by single FCDs (two cases), and others including gliosis, encephalocoele, and amygdala enlargement (one case each). Eleven of the 14 (79%) previously "non-lesional" patients had electroencephalogram (EEG) imaging-concordant localisation features, rendering them potential candidates for resective surgery. CONCLUSIONS: The primary factors explaining the newly identified lesions were the choice of MRI sequences, imaging parameters, data quality, lesion not reported (human factor), and loss of information through incomplete documentation. It is important for all clinicians to proceed meticulously in the detailed assessment of epilepsy-dedicated in-vivo MRI and discuss difficult patient cases in multidisciplinary team meetings.


Asunto(s)
Encéfalo/diagnóstico por imagen , Epilepsia Refractaria/diagnóstico por imagen , Epilepsias Parciales/diagnóstico por imagen , Neuroimagen , Adolescente , Adulto , Amígdala del Cerebelo/diagnóstico por imagen , Amígdala del Cerebelo/patología , Encéfalo/patología , Protocolos Clínicos , Epilepsia Refractaria/patología , Electroencefalografía , Epilepsias Parciales/patología , Femenino , Gliosis/diagnóstico por imagen , Gliosis/patología , Hipocampo/diagnóstico por imagen , Hipocampo/patología , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Esclerosis/diagnóstico por imagen , Esclerosis/patología , Adulto Joven
11.
Lett Appl Microbiol ; 69(1): 23-29, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30932223

RESUMEN

The occurrence of Escherichia coli O157 and Salmonella spp. in solid bovine manure was investigated through a multi-county survey in California. Solid bovine manure samples (n = 91) were collected from 13 dairy farms located in multiple counties in California between June 2016 and August 2017. To quantify pathogens, DNA was extracted from bacteria in manure samples. Afterwards, the prevalence and levels of E. coli O157 and Salmonella spp. in solid bovine manure were determined by real-time quantitative PCR (qPCR). The prevalence of E. coli O157 and Salmonella spp. in solid bovine manure was 15·4 and 6·6% respectively. Escherichia coli O157 and Salmonella spp. levels in positive samples ranged from 3·1 to 5·3 log CFU per g and from positive (the population was <3 log CFU per g) to 5·2 log CFU per g respectively. Surface samples of manure piles had higher prevalence and levels of E. coli O157 and Salmonella spp. than subsurface samples, while no seasonal effects on pathogen occurrence were observed. Our results indicated that solid bovine manure is a source of E. coli O157 and Salmonella spp. and the application of untreated manure as biological soil amendments may pose potential risks to public health. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings suggested that the presence of Escherichia coli O157 and Salmonella spp. in solid bovine manure may pose potential risks if untreated manure is applied as biological soil amendments. Considering the large-scale sampling used in this study, the observations provide a holistic assessment in terms of pathogen prevalence in solid bovine manure.


Asunto(s)
Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/veterinaria , Escherichia coli O157/aislamiento & purificación , Estiércol/microbiología , Salmonelosis Animal/epidemiología , Salmonella/aislamiento & purificación , Animales , California/epidemiología , Bovinos , Recuento de Colonia Microbiana , Reacción en Cadena de la Polimerasa , Prevalencia , Suelo , Microbiología del Suelo
12.
J Environ Manage ; 248: 109339, 2019 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-31394477

RESUMEN

In situ moisture conservation practices can conserve fertile topsoil and enhance available water in soil profile. We hypothesised that reclaiming degraded land ecologically through tree + pasture + in situ moisture conservation practices would significantly improve soil organic carbon (SOC) and health. Hence, the objectives were a) to identify changes in nutrient cycling enzymes and SOC status due to different in situ soil moisture conservation options in surface and subsurface soil layers, and b) to test the potentiality of soil enzymes to determine long-term nutrient availability. We conducted a long-term experiment involving aonla (Emblica officinalis) trees + pasture (Cenchrus ciliaris + Stylosanthes seabrana) + in situ soil moisture conservation measures viz. staggered contour trenches (T1), continuous contour trenches (T2), stone mulch (T3), vegetative barriers (T4), control (T5) and fallow land (T6) since 2007. Recommended dose of nitrogen (N), phosphorus (P) and potassium (K) were added to all treatments, except T6. SOC concentration increased by ~51 and 31% in T1 and T2, respectively, over T5 in surface (0-15 cm) soil. Culturable bacterial and fungal populations increased by ~20 and 95% in T1 over T5 in surface soil. Activities of all soil enzymes increased in T1 and T2 (ranging from 42 to 289%) over T5 and T6 in both surface and sub-surface (15-30 cm) layers. However, specific activity of phenol oxidase was ~25% lower for T1 than T6, suggesting more efficient SOC sequestration in T1. Moreover, geometric mean enzyme activity of T1 was ~65 and 33% higher than T5 and T3, respectively, in surface soil. Treated soil quality index (T-SQI) of T1 was ~184% higher than T5. Soil functional diversity was also ~1.24 and 1.22 times higher in T1 and T2 than T5, respectively. Peroxidase was the major C degrading enzyme in this ecosystem. Protease, urease and phosphatase significantly influenced N and P availability along with fruit and pasture yields. Importantly, ~96, 62 and 82% variability of SOC, N and P concentrations, respectively, could be attributed to their corresponding enzyme activities. Principal components analysis (PCA) revealed one-way operational role of soil enzymes. Thus, enzymes are potentially important for recycling nutrients from litters, root biomass of fruit trees and grasses to boost their availability in the long run. Adoption of horti-pasture system combined with moisture conservation practices and staggered contour trenches or continuous contour trenches ensured higher above ground biomass yield, SOC, nutrient availability and soil quality. Thus, long-term use of these practices could be recommended for reclamation and improving soil health and crop productivity of degraded lands of central India.


Asunto(s)
Ecosistema , Suelo , Carbono , Secuestro de Carbono , India
13.
Bioconjug Chem ; 29(10): 3362-3376, 2018 10 17.
Artículo en Inglés | MEDLINE | ID: mdl-30169965

RESUMEN

The impact of influenza virus infection is felt each year on a global scale when approximately 5-10% of adults and 20-30% of children globally are infected. While vaccination is the primary strategy for influenza prevention, there are a number of likely scenarios for which vaccination is inadequate, making the development of effective antiviral agents of utmost importance. Anti-influenza treatments with innovative mechanisms of action are critical in the face of emerging viral resistance to the existing drugs. These new antiviral agents are urgently needed to address future epidemic (or pandemic) influenza and are critical for the immune-compromised cohort who cannot be vaccinated. We have previously shown that lipid tagged peptides derived from the C-terminal region of influenza hemagglutinin (HA) were effective influenza fusion inhibitors. In this study, we modified the influenza fusion inhibitors by adding a cell penetrating peptide sequence to promote intracellular targeting. These fusion-inhibiting peptides self-assemble into ∼15-30 nm nanoparticles (NPs), target relevant infectious tissues in vivo, and reduce viral infectivity upon interaction with the cell membrane. Overall, our data show that the CPP and the lipid moiety are both required for efficient biodistribution, fusion inhibition, and efficacy in vivo.


Asunto(s)
Antivirales/farmacología , Péptidos de Penetración Celular/farmacología , Virus de la Influenza A/efectos de los fármacos , Fusión de Membrana/efectos de los fármacos , Administración Intranasal , Secuencia de Aminoácidos , Animales , Antivirales/administración & dosificación , Antivirales/química , Antivirales/farmacocinética , Disponibilidad Biológica , Membrana Celular/metabolismo , Péptidos de Penetración Celular/química , Endocitosis , Glicoproteínas Hemaglutininas del Virus de la Influenza/química , Glicoproteínas Hemaglutininas del Virus de la Influenza/metabolismo , Humanos , Huésped Inmunocomprometido , Nanopartículas/química , Sigmodontinae , Proteínas Virales/química , Productos del Gen tat del Virus de la Inmunodeficiencia Humana/química
14.
Artículo en Inglés | MEDLINE | ID: mdl-29094780

RESUMEN

This systematic review and meta-analysis aimed to evaluate the effectiveness of psychological interventions in improving quality of life for head and neck cancer patients. Five databases were systematically searched in July 2016. Studies were included if they reported original empirical data from intervention studies utilising psychological approaches (excluding psychoeducational-only interventions) and provided data on quality of life outcomes. Six studies, involving 185 participants, fulfilled eligibility criteria. Study designs included a case study, single-group designs, non-randomised controlled trials and one randomised controlled trial. Meta-analysis of two studies did not provide support for the effectiveness of psychological intervention improving total quality of life scores (or subscales) compared to control groups at end of intervention. Intervention studies evaluating psychological interventions for patients with head and neck cancer have produced insufficient data to support their effectiveness for improving quality of life. This review further highlights the limited evidence base within this area. Existing studies are based on small samples and are inconsistent regarding: intervention type, duration and intensity; follow-up measurement periods; and methodological quality. Further research, addressing these limitations, is required for more definitive conclusions to be drawn about the effectiveness of psychological interventions with this population.


Asunto(s)
Neoplasias de Cabeza y Cuello/psicología , Psicoterapia , Calidad de Vida/psicología , Biblioterapia , Terapia Cognitivo-Conductual , Humanos , Atención Plena
15.
J Environ Qual ; 47(1): 185-189, 2018 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-29415095

RESUMEN

Dairy manure is regularly applied to crop fields as a solid or liquid to improve the soil nutrient status. However, pathogens may survive during manure storage and enter the environment during application. In this study, three storage practices were evaluated to understand the survival patterns of O157:H7 and spp. in dairy manure using a culture-based approach. To replicate common farm manure storage techniques, solid manure was stacked as piles with periodic turning or as static piles without turning, whereas liquid manure (feces, urine, and water) was stored as a slurry in small tanks to simulate lagoon conditions. The and levels in the manure samples were determined for 29 wk. Results showed that there was an initial reduction in bacteria levels in the first month; however, both and managed to survive in the solid manure piles for the full study period. In slurry samples, was not detected after 14 wk, but survived until the end of the experiment at relatively lower levels than in the solid manure piles. Ambient weather and pile size were identified as the main reasons for bacteria survival during the course of the experiment. The outcome of this study is important in terms of understanding pathogen survival in manure piles and slurries prior to their application to crop fields.


Asunto(s)
Escherichia coli O157/fisiología , Listeria/fisiología , Estiércol/microbiología , Microbiología del Suelo , Administración de Residuos
16.
Nanotechnology ; 28(13): 135203, 2017 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-28157090

RESUMEN

We report a theoretical and experimental investigation of the hybrid heterostructure interfaces between atomically thin MoS2 nanocrystals (NCs) on Si platform for their potential applications towards next-generation electrical and optical devices. Mie theory-based numerical analysis and COMSOL simulations based on the finite element method have been utilized to study the optical absorption characteristics and light-matter interactions in variable-sized MoS2 NCs. The size-dependent absorption characteristics and the enhancement of electric field of the heterojunction in the UV-visible spectral range agree well with the experimental results. A lithography-free, wafer-scale, 2D material on a 3D substrate hybrid vertical heterostructure has been fabricated using colloidal n-MoS2 NCs on p-Si. The fabricated p-n heterojunction exhibited excellent junction characteristics with a high rectification ratio suitable for voltage clipper and rectifier applications. The current-voltage characteristics of the devices under illumination have been performed in the temperature range of 10-300 K. The device exhibits a high photo-to-dark current ratio of ∼3 × 103 and a responsivity comparable to a commercial Si photodetector. The excellent heterojunction characteristics demonstrate the great potential of MoS2 NC-based hybrid electronic and optoelectronic devices in the near future.

17.
Mymensingh Med J ; 26(2): 455-458, 2017 04.
Artículo en Inglés | MEDLINE | ID: mdl-28588187

RESUMEN

Primary sclerosing cholangitis (PSC) is a liver disease characterized by inflammation and fibrosis of both intrahepatic and extrahepatic bile ducts resulting in cholestasis. Due to nonspecific symptoms it is difficult to diagnose until complication arises. It is common in male and usually associated with other autoimmune diseases. Here, we report a case of PSC in a young female which was initially thought to be drug induced cholestasis without presence of any other autoimmunity.


Asunto(s)
Colangitis Esclerosante , Conductos Biliares Extrahepáticos/fisiopatología , Colangitis Esclerosante/diagnóstico , Femenino , Humanos
18.
J Fluoresc ; 26(5): 1541-8, 2016 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-27380200

RESUMEN

Here we have demonstrated a novel single step technique of synthesis of highly fluorescent carbon nanoparticles (CNPs) from broth constituent and in vivo bioimaging of Caenorhabditis elegans (C. elegans) with the synthesized CNPs has been presented. The synthesized CNPs has been characterized by the UV-visible (UV-Vis) absorption spectroscopy, transmission electron microscopy (TEM) and Raman studies. The sp (2) cluster size of the synthesized samples has been determined from the measured Raman spectra by fitting it with the theoretical skew Lorentzian (Breit-Wigner- Fano (BWF)) line shape. The synthesised materials are showing excitation wavelength dependent tunable photoluminescence (PL) emission characteristics with a high quantum yield (QY) of 3 % at a very low concentration of CNPs. A remarkable increase in the intensity of PL emission from 16 % to 39 % in C. elegans has also been observed when the feeding concentration of CNPs to C. elegans is increased from 0.025 % to 0.1 % (w/v). The non-toxicity and water solubility of the synthesized material makes it ideal candidate for bioimaging.


Asunto(s)
Caenorhabditis elegans/metabolismo , Carbono/química , Colorantes Fluorescentes/química , Imagen Molecular/métodos , Nanopartículas/química , Animales , Caenorhabditis elegans/química , Microscopía Electrónica de Transmisión
20.
Phys Chem Chem Phys ; 18(34): 23879-87, 2016 Sep 14.
Artículo en Inglés | MEDLINE | ID: mdl-27524510

RESUMEN

Self-assembled Ag-coated multiphasic diluted magnetic chromium oxide nanocomposites were developed by a facile chemical synthesis route involving a reaction of CrO3 in the presence of Ag(+) ions in an aqueous solution of poly-vinyl alcohol (PVA) and sucrose. The tiny ferromagnetic single domains of tetragonal and orthorhombic CrO2 (t-CrO2 and o-CrO2) embedded in a dominantly insulating matrix of antiferromagnetic Cr2O3 and Cr3O8, and paramagnetic CrO3 and Cr2O, with a correlated diamagnetic thin and discontinuous shell layer of Ag efficiently tailor useful magnetic and room-temperature magnetoresistance (RTMR) properties. The t-CrO2, o-CrO2, possible canted ferromagnetism due to spin disorder in the matrix components, and the associated exchange interactions are the elements responsible for the observed ferromagnetism in the composite structure. The chain of ferromagnetic centers embedded in the composite matrix constitutes a type of magnetic tunnel junction through which spin-polarized electrons can effectively move without significant local interruptions. Electrical transport measurements showed that the spin-dependent tunneling (SDT) mechanism in the engineered microstructure of the nanocomposites exists even at room temperature (RT). A typical sample unveils a markedly enhanced RTMR-value, e.g., -80% at an applied field (H) of 3 kOe, compared to the reported values for compacted CrO2 powders or composites. The enhanced RTMR-value observed in the Coulomb blockade regime appears not only due to the considerably suppressed spin flipping at RT but primarily due to a highly effective SDT mechanism through an interlinked structure of Ag-coated multiphasic chromium oxide nanocomposites.

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