Heat transport in the XXZXXZ spin chain: from ballistic to diffusive regimes and dephasing enhancement

In this work we study the heat transport in an XXZ spin-1/2 Heisenberg chain with homogeneous magnetic field, incoherently driven out of equilibrium by reservoirs at the boundaries. We focus on the effect of bulk dephasing (energy-dissipative) processes in different parameter regimes of the system. The non-equilibrium steady state of the chain is obtained by simulating its evolution under the corresponding Lindblad master equation, using the time evolving block decimation method. In the absence of dephasing, the heat transport is ballistic for weak interactions, while being diffusive in the strongly-interacting regime, as evidenced by the heat-current scaling with the system size. When bulk dephasing takes place in the system, diffusive transport is induced in the weakly-interacting regime, with the heat current monotonically decreasing with the dephasing rate. In contrast, in the strongly-interacting regime, the heat current can be significantly enhanced by dephasing for systems of small size

Metal-free visible-light-induced dithiol–ene clicking via carbon nitride to valorize 4-pentenoic acid as a functional monomer

The necessity for more bio-based building blocks and processes have led to utilizing new polymerization approaches with a lower carbon footprint. Here, we demonstrate the synthesis of a visible-light-induced dithiol–ene clicking reaction between lignocellulosic biomass-derivable 4-pentenoic acid (4-PEA) and different dithiols, i.e., 1,2-ethanedithiol (EDT), 2,2-(ethylenedioxy)diethanethiol (EDDT), and 1,4-benzenedimethanethiol (BDT), using graphitic carbon nitride (g-CN) as a metal-free photocatalyst. The formation of dicarboxylic acid functional monomers were confirmed using 1H NMR and FT-IR. Furthermore, polyamides were synthesized from the dicarboxylic acid functional monomers to demonstrate the applicability of the monomers yielding new polyamide end polymers

Scattering from supramacromolecular structures

We study theoretically the scattering imprint of a number of branched supramacromolecular architectures, namely, polydisperse stars and dendrimeric, hyperbranched structures. We show that polydispersity and nature of branching highly influence the intermediate wavevector region of the scattering structure factor, thus providing insight into the morphology of different aggregates formed in polymer solutions.Comment: 20 pages, 8 figures To appear in PR

p-Xylene from 2,5-dimethylfuran and acrylic acid using zeolite in continuous flow system

The continuous flow synthesis of p-Xylene (pXL) via Diels-Alder cycloaddition of lignocellulosic biomass-derivable 2,5-dimethylfuran (DMF) and acrylic acid (AA) was performed over different type of zeolites, i.e. Beta, ZSM-5 and Y. Among the tested zeolites, Beta zeolite showed an optimum catalytic performance in pXL synthesis from DMF and AA. In this context, Beta zeolite with a Si/Al molar ratio of 150 which is abbreviated Beta(150), resulted in a complete DMF conversion with a pXL yield of 83, and 2,5-dimethylbenzoic acid (DMBA) with yield of 17 as the second product, at 473 K and 10.1 min residence time (τ) and excess of AA (0.7 M). This high catalytic activity is attributed to the high specific surface area of 1180 m2 g-1 with a three-dimensional porous architecture with pore diameter of (6.6 × 6.7 Å) and an acid sites density above 40 µmol g-1. The utilized Beta(150) showed a very stable performance up to 10 h time on stream with minor deactivation after 8 h of TOS, while pXL yield stayed above 70. The original catalytic performance of Beta(150) in DMF upgrading to pXL was restored by applying a regeneration step for the spent catalyst, which is simple in continuous flow reactors. Finally, this sustainable continuous flow process enables an efficient and selective pXL production from DMF and AA as a dienophile at lower reaction temperature (473 K) and shorter residence time (τ = 10.1 min) with respect to batch fashion

Binding of the five multistate species of the anthocyanin analog 7- β -D-glucopyranosyloxy-4′-hydroxyflavylium to the β -cyclodextrin derivative captisol

The host-guest chemistry of the anthocyanin analog 7-β-D-glucopyranosyloxy-4'-hydroxyflavylium (GHF) was studied in the presence of the β-cyclodextrin derivative captisol by stopped flow, UVevisible spectroscopy, flash photolysis, circular dichroism and isothermal titration calorimetry. The equilibrium and rate constants of the multistate of chemical species derived from the flavylium ion were calculated and compared with those in the absence of the host. A new procedure to obtain the host-guest association constants of the multistate (including the transient species) by superimposing the two energy level diagrams, in the presence and absence of the cyclodextrin, was developed. The results indicate that the magnitude of the association constants follows the order, trans-chalcone = cis-chalcone = hemiketal > quinoidal base > flavylium cation. The hydration equilibrium constant increases ca. 42 times in the presence of captisol as the hydration and dehydration rate constants respectively increases and decreases. The other equilibrium constants are modestly affected: the rate constants of ring closure and opening are significantly decreased in the complex and the isomerization rate constants increase in both directions. The quantum yield of the photochromic system in the presence of captisol is0.3, i.e. 3 times higher than in the absence of the host

Durabilidad del hormigón frente a los ciclos hielo-deshielo. Evaluación de dos tipos de hormigón.

El presente trabajo estudia el comportamiento de dos hormigones frente al ensayo de resistencia al hielo-deshielo de hormigones endurecidos. La incorporación de un aditivo aireante mejora de forma sensible el comportamiento del hormigón frente a este ensayo. Sin embargo, en hormigón pretensado con cordón adherente está prohibido el uso de aditivos aireantes. Una estrategia adecuada es emplear humo de sílice para mejorar la impermeabilidad del hormigón. En este trabajo se compara el comportamiento de un hormigón con aditivo aireante y otro con humo de sílice frente al ensayo de resistencia al hielo-deshielo. Además, estudia la viabilidad de emplear técnicas alternativas de medida del deterioro superficial: modificación de la velocidad de pulso ultrasónico y medida de la deformación superficial con galgas extensométricas. Ambas técnicas se muestran viables y aportan ventajas frente al peso de la masa superficial desprendida por descascarillamient

Health-related quality of life in patients with sickle cell disease in Saudi Arabia

Background There is a lack of research concerning health-related quality of life (HRQoL) in Saudi patients with sickle cell disease (SCD), particularly among adult populations. The aim of the current study was to describe the characteristics of SCD patients and their impact on their quality of life (QoL). Methods Six hundred twenty-nine adult SCD patients who attended King Fahad Hospital in Hofuf and King Fahad Central Hospital in Jazan were included in the analysis. Demographic/clinical data were collected and an Arabic version of the Medical Outcomes 36-Item Short-Form Health Survey (SF-36) questionnaire was used to assess QoL. Results SCD patients who hold a university degree reported positive impacts on the following domains of SF-36: physical role function, vitality, emotional well being, social function, pain reduction, and general health (P = .002, P = .001, P = .001, P = .003, P = .004, and P = .001, respectively). In general, patients with fever, skin redness, swelling, or history of blood transfusion tended to impair the health status of the SF-36. A multivariate analysis revealed that patients with a university degree tended to report high scores of physical role functions, emotional role function, and vitality. Patients with regular exercise tend to increase vitality, social function, general health, and reduce pain. Unemployment tends to lessen vitality and worsen pain. On average, pain, social function, and physical function scores tended to worsen in patients with swelling or history of blood transfusion. Conclusions This study highlighted that poor education, fever, skin redness, and swelling were negatively associated with specific components of SF-36. SCD patients with a history of blood transfusion found their QoL poorer, whereas regular exercise tended to improve QoL

The Source of Three-minute Magneto-acoustic Oscillations in Coronal Fans

We use images of high spatial, spectral and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the coupling between wave phenomena observed at numerous heights in the solar atmosphere. Intensity oscillations of 3 minutes are observed to encompass photospheric umbral dot structures, with power at least three orders-of-magnitude higher than the surrounding umbra. Simultaneous chromospheric velocity and intensity time series reveal an 87 \pm 8 degree out-of-phase behavior, implying the presence of standing modes created as a result of partial wave reflection at the transition region boundary. An average blue-shifted Doppler velocity of ~1.5 km/s, in addition to a time lag between photospheric and chromospheric oscillatory phenomena, confirms the presence of upwardly-propagating slow-mode waves in the lower solar atmosphere. Propagating oscillations in EUV intensity are detected in simultaneous coronal fan structures, with a periodicity of 172 \pm 17 s and a propagation velocity of 45 \pm 7 km/s. Numerical simulations reveal that the damping of the magneto-acoustic wave trains is dominated by thermal conduction. The coronal fans are seen to anchor into the photosphere in locations where large-amplitude umbral dot oscillations manifest. Derived kinetic temperature and emission measure time-series display prominent out-of-phase characteristics, and when combined with the previously established sub-sonic wave speeds, we conclude that the observed EUV waves are the coronal counterparts of the upwardly-propagating magneto-acoustic slow-modes detected in the lower solar atmosphere. Thus, for the first time, we reveal how the propagation of 3 minute magneto-acoustic waves in solar coronal structures is a direct result of amplitude enhancements occurring in photospheric umbral dots.Comment: Accepted into ApJ (13 pages and 10 figures

The therapeutic potential of the filarial nematode-derived immunodulator, ES-62 in inflammatory disease

The dramatic recent rise in the incidence of allergic or autoimmune inflammatory diseases in the West has been proposed to reflect the lack of appropriate priming of the immune response by infectious agents such as parasitic worms during childhood. Consistent with this, there is increasing evidence supporting an inverse relationship between worm infection and T helper type 1/17 (Th1/17)-based inflammatory disorders such as rheumatoid arthritis, inflammatory bowel disease, type 1 diabetes and multiple sclerosis. Perhaps more surprisingly, given that such worms often induce strong Th2-type immune responses, there also appears to be an inverse correlation between parasite load and atopy. These findings therefore suggest that the co-evolution of helminths with hosts, which has resulted in the ability of worms to modulate inflammatory responses to promote parasite survival, has also produced the benefit of protecting the host from pathological lesions arising from aggressive proinflammatory responses to infection or, indeed, aberrant inflammatory responses underlying autoimmune and allergic disorders. By focusing upon the properties of the filarial nematode-derived immunomodulatory molecule, ES-62, in this review we shall discuss the potential of exploiting the immunomodulatory products of parasitic worms to identify and develop novel therapeutics for inflammation