Inhomogeneous soliton ratchets under two ac forces

We extend our previous work on soliton ratchet devices [L. Morales-Molina et al., Eur. Phys. J. B 37, 79 (2004)] to consider the joint effect of two ac forces including non-harmonic drivings, as proposed for particle ratchets by Savele'v et al. [Europhys. Lett. 67}, 179 (2004); Phys. Rev. E {\bf 70} 066109 (2004)]. Current reversals due to the interplay between the phases, frequencies and amplitudes of the harmonics are obtained. An analysis of the effect of the damping coefficient on the dynamics is presented. We show that solitons give rise to non-trivial differences in the phenomenology reported for particle systems that arise from their extended character. A comparison with soliton ratchets in homogeneous systems with biharmonic forces is also presented. This ratchet device may be an ideal candidate for Josephson junction ratchets with intrinsic large damping

Ratchet behavior in nonlinear Klein-Gordon systems with point-like inhomogeneities

We investigate the ratchet dynamics of nonlinear Klein-Gordon kinks in a periodic, asymmetric lattice of point-like inhomogeneities. We explain the underlying rectification mechanism within a collective coordinate framework, which shows that such system behaves as a rocking ratchet for point particles. Careful attention is given to the kink width dynamics and its role in the transport. We also analyze the robustness of our kink rocking ratchet in the presence of noise. We show that the noise activates unidirectional motion in a parameter range where such motion is not observed in the noiseless case. This is subsequently corroborated by the collective variable theory. An explanation for this new phenomenom is given

Internal mode mechanism for collective energy transport in extended systems

We study directed energy transport in homogeneous nonlinear extended systems in the presence of homogeneous ac forces and dissipation. We show that the mechanism responsible for unidirectional motion of topological excitations is the coupling of their internal and translation degrees of freedom. Our results lead to a selection rule for the existence of such motion based on resonances that explains earlier symmetry analysis of this phenomenon. The direction of motion is found to depend both on the initial and the relative phases of the two harmonic drivings, even in the presence of noise.Comment: Final version, to appear in Physical Review Letter

Soliton ratchets in homogeneous nonlinear Klein-Gordon systems

We study in detail the ratchet-like dynamics of topological solitons in homogeneous nonlinear Klein-Gordon systems driven by a bi-harmonic force. By using a collective coordinate approach with two degrees of freedom, namely the center of the soliton, $X(t)$, and its width, $l(t)$, we show, first, that energy is inhomogeneously pumped into the system, generating as result a directed motion; and, second, that the breaking of the time shift symmetry gives rise to a resonance mechanism that takes place whenever the width $l(t)$ oscillates with at least one frequency of the external ac force. In addition, we show that for the appearance of soliton ratchets, it is also necesary to break the time-reversal symmetry. We analyze in detail the effects of dissipation in the system, calculating the average velocity of the soliton as a function of the ac force and the damping. We find current reversal phenomena depending on the parameter choice and discuss the important role played by the phases of the ac force. Our analytical calculations are confirmed by numerical simulations of the full partial differential equations of the sine-Gordon and $\phi^4$ systems, which are seen to exhibit the same qualitative behavior. Our results are in agreement with recent experimental work on dissipation induced symmetry breaking.Comment: Minor corrections, several references added, accepted for publication in Chao

Antioksidativna aktivnost ferementiranih i nefermentiranih esktrakata iz otpada nastalog pri proizvodnji kave

Coffee pulp contains natural antioxidants like hydroxycinnamic acids, most of which are covalently linked to the cell wall. These compounds can be released by fermentation or enzymatic processes. In this study, the antioxidant properties of fermented and nonfermented coffee pulp have been evaluated. Coffee pulp was fermented by solid-state fermentation using the fungus Aspergillus tamarii. Fermented and nonfermented samples of coffee pulp were extracted with aqueous methanol followed by alkaline hydrolysis. In both cases, the total polyphenol concentration was quantified by Folin-Ciocalteu method, then hydroxycinnamic acids were concentrated using ethyl acetate and quantified by HPLC. The antioxidant properties of samples were determined by radical monocation of 2,2’-azinobis-( 3-ethylbenzothiazoline-6-sulphonic acid) [ABTS]·+: the antioxidant activity was determined by kinetic parameters known as ED50, tED50 and antiradical efficiency (AE). Fermented extracts containing free hydroxycinnamic acids showed better antiradical activity against [ABTS]·+ than the other nonfermented ones. There were no significant differences in the total content of polyphenols in fermented and nonfermented coffee pulp, but the content of total hydroxycinnamic acids was higher in the nonfermented coffee pulp extracts (47.1 g/kg) than in the fermented coffee pulp (30.9 g/kg). Nevertheless, the fermentation process increased the fraction of free hydroxycinnamic acids (47 %) and consequently decreased those covalently linked to the cell wall. The results of the antioxidant activity assays could be explained by the presence of free hydroxycinnamic acids. Fermented coffee pulp assays showed that free hydroxycinnamic acids were metabolised by A. tamarii. This study shows the potential of using coffee pulp as a natural source of antioxidants.Otpad nastao pri proizvodnji kave sadržava prirodne antioksidanse, kao što su hidroksicinamične kiseline, od kojih je većina kovalentno vezana za staničnu stijenku. Takvi se spojevi mogu osloboditi fermentacijom ili pomoću enzima. U ovom su radu istražena antioksidativna svojstva fermentiranih i nefermentiranih esktrakata, pri čemu je fermentacija provedena s pomoću plijesni Aspergillus tamarii na čvrstoj podlozi od otpada nastalog pri proizvodnji kave. Fermentirani i nefermentirani spojevi esktrahirani su vodenom otopinom metanola, nakon čega je provedena njihova alkalna hidroliza. U oba je slučaja koncentracija ukupnih polifenola određena Folin-Ciocalteu metodom, a zatim su hidroksicinamične kiseline koncentrirane pomoću etil acetata i analizirane HPLC-om. Antioksidativna su svojstva uzoraka, tj. vrijednosti ED50 i tED50 te antiradikalni učinak, određena pomoću radikala 2,2\u27-azinobis(3-etilbenzotiazolin-6-sulfonske kiseline) [ABTS].+. Fermentirani su ekstrakti sadržavali slobodne hidroksicinamične kiseline i imali su bolju antioksidativnu aktivnost s obzirom na [ABTS].+ od nefermentiranih ekstrakata. Nije bilo bitne razlike u koncentracijama ukupnih polifenola u fermentiranim i nefermentiranim ekstraktima, ali je udio hidroksicinamičnih kiselina bio veći u nefermentiranim (47,1 g/kg) nego u fermentiranim ekstraktima (30,9 g/kg). Fermentacija je povećala udjel slobodnih (na 47 %), a smanjila udjel vezanih hidroksicinamičnih kiselina. Zaključeno je da je antioksidativna aktivnost ekstrakata ovisila o udjelu slobodnih hidroksicinamičnih kiselina, koji se povećao nakon fermentacije otpada nastalog pri proizvodnji kave s pomoću A. tamarii. Time je potvrđeno da se postupak može primijeniti za ekstrakciju prirodnih antioksidanasa

C-S-H seeding activation of Portland and Belite cements: An enlightening in situ synchrotron powder diffraction study

C-S-H seeding in Portland cements is well known from basic scientific works and field applications. Moreover, this activation approach could be beneficial for low-CO2 cements under development where a general drawback is poor mechanical strengths during the first week of hydration. However, a mechanistic understanding of the different processes taking place when seeding is still not developed. Here, we contribute to this knowledge gap by studying one commercial Portland cement and two industrial-trial belite cements. Three different admixtures are employed, viz. two types of commercial C-S-H seeding and triisopropanolamine as a typical alkanolamine. A multitechnique approach is employed including calorimetry, ultrasonic pulse velocity, thermal analysis and Rietveld analysis of laboratory X-ray powder diffraction data. Chiefly, an in situ X-ray synchrotron diffraction study has allowed mapping out the evolution of every crystalline phase. Furthermore, the use of an internal standard permitted to measure the changes in the overall amorphous content. In a nutshell, alite and belite (phases) hydrations are not significantly accelerated by C-S-H seeding for the three studied cements. Conversely, sulphate and aluminate phase dissolutions are enhanced. Faster ettringite crystallisation contributes to the observed improved mechanical properties at early ages. Moreover, a synergistic effect between C-S-H seeding and alkanolamine addition is proved. The importance of these findings for the possible acceleration of low-CO2 cement hydration is discussed.This research has been partly supported by two research grants PID2020-114650RB-I00 (from Spanish Government) and P18-RT-720 (from Junta de Andalucía, Spain), which are co-funded by ERDF. ALBA synchrotron is thanked for granting beamtime at BL04-MSPD beamline. We also thank the assistance of Dr. Oriol Vallcorba during the synchrotron experiment and thorough discussion of this work with Peter Schwesig (Master Builders Solutions). Funding for open access charge: Universidad de Malaga/CBUA

The physical oceanography of the transport of floating marine debris

Marine plastic debris floating on the ocean surface is a major environmental problem. However, its distribution in the ocean is poorly mapped, and most of the plastic waste estimated to have entered the ocean from land is unaccounted for. Better understanding of how plastic debris is transported from coastal and marine sources is crucial to quantify and close the global inventory of marine plastics, which in turn represents critical information for mitigation or policy strategies. At the same time, plastic is a unique tracer that provides an opportunity to learn more about the physics and dynamics of our ocean across multiple scales, from the Ekman convergence in basin-scale gyres to individual waves in the surfzone. In this review, we comprehensively discuss what is known about the different processes that govern the transport of floating marine plastic debris in both the open ocean and the coastal zones, based on the published literature and referring to insights from neighbouring fields such as oil spill dispersion, marine safety recovery, plankton connectivity, and others. We discuss how measurements of marine plastics (both in situ and in the laboratory), remote sensing, and numerical simulations can elucidate these processes and their interactions across spatio-temporal scales

Three-Dimensional Analysis of Spiny Dendrites Using Straightening and Unrolling Transforms

Current understanding of the synaptic organization of the brain depends to a large extent on knowledge about the synaptic inputs to the neurons. Indeed, the dendritic surfaces of pyramidal cells (the most common neuron in the cerebral cortex) are covered by thin protrusions named dendritic spines. These represent the targets of most excitatory synapses in the cerebral cortex and therefore, dendritic spines prove critical in learning, memory and cognition. This paper presents a new method that facilitates the analysis of the 3D structure of spine insertions in dendrites, providing insight on spine distribution patterns. This method is based both on the implementation of straightening and unrolling transformations to move the analysis process to a planar, unfolded arrangement, and on the design of DISPINE, an interactive environment that supports the visual analysis of 3D patterns

Prolonged survival of patients with angioimmunoblastic T-cell lymphoma after high-dose chemotherapy and autologous stem cell transplantation: the GELTAMO experience

Abstract OBJECTIVES: Angioimmunoblastic T-cell lymphoma (AIL) is a rare lymphoma with a poor prognosis and no standard treatment. Here, we report our experiences with 19 patients treated with high-dose chemotherapy and autologous stem cell transplantation (HDC/ASCT) within the GELTAMO co-operative group between 1992 and 2004. METHODS: The median age at transplantation was 46 yr. Fifteen patients underwent the procedure as front-line therapy and four patients as salvage therapy. Most patients received peripheral stem cells (90%) coupled with BEAM or BEAC as conditioning regimen (79%). RESULTS: A 79% of patients achieved complete response, 5% partial response and 16% failed the procedure. After a median follow-up of 25 months, eight patients died (seven of progressive disease and secondary neoplasia), while actuarial overall survival and progression-free survival at 3 yr was 60% and 55%. Prognostic factors associated with a poor outcome included bone marrow involvement, transplantation in refractory disease state, attributing more than one factor of the age-adjusted-International Prognostic Index, Pretransplant peripheral T-cell lymphoma (PTCL) Score or Prognostic Index for PTCL. CONCLUSIONS: More than half of the patients with AIL that display unfavourable prognostic factors at diagnosis or relapse would be expected to be alive and disease-free after 3 yr when treated with HDC/ASCT. Patients who are transplanted in a refractory disease state do not benefit from this procedure