Crystal-to-crystal transition of ultrasoft colloids under shear

Ultrasoft colloids typically do not spontaneously crystallize, but rather vitrify, at high concentrations. Combining in-situ rheo-SANS experiments and numerical simulations we show that shear facilitates crystallization of colloidal star polymers in the vicinity of their glass transition. With increasing shear rate well beyond rheological yielding, a transition is found from an initial bcc-dominated structure to an fcc-dominated one. This crystal-to-crystal transition is not accompanied by intermediate melting but occurs via a sudden reorganization of the crystal structure. Our results provide a new avenue to tailor colloidal crystallization and crystal-to-crystal transition at molecular level by coupling softness and shear

Tuning the rheological behavior of colloidal gels through competing interactions

We study colloidal gels formed by competing electrostatic repulsion and short-range attraction by means of extensive numerical simulations under external shear. We show that, upon varying the repulsion strength, the gel structure and its viscoelastic properties can be largely tuned. In particular, the gel fractal dimension can be either increased or decreased with respect to mechanical equilibrium conditions. Unexpectedly, gels with stronger repulsion, despite being mechanically stiffer, are found to be less viscous with respect to purely attractive ones. We provide a microscopic explanation of these findings in terms of the influence of an underlying phase separation. Our results allow for the design of colloidal gels with desired structure and viscoelastic response by means of additional electrostatic interactions, easily controllable in experiments

Update on field use of the available drugs for the chemotherapy of human African trypanosomiasis

Despite the fact that eflornithine was considered as the safer drug to treat human African trypanosomiasis (HAT) and has been freely available since 2001, the difficulties in logistics and cost burden associated with this drug meant that the toxic melarsoprol remained the drug of choice. The World Health Organization responded to the situation by designing a medical kit containing all the materials needed to use eflornithine, and by implementing a training and drugs distribution programme which has allowed a transition to this much safer treatment. The introduction of the combination of nifurtimox and eflornithine (NECT) has accelerated the shift from melarsoprol to the best treatment available, due to reduced dosage and treatment time for eflornithine that has significantly lessened the cost and improved the burden of logistics encountered during treatment and distribution. The decrease in the use of more dangerous but cheaper melarsoprol has meant a rise in the per patient cost of treating HAT. Although NECT is cheaper than eflornithine monotherapy, an unexpected consequence has been a continuing rise in the per patient cost of treating HAT. The ethical decision of shifting to the best available treatment imposes a financial burden on HAT control programmes that might render long-term application unsustainable. These factors call for continuing research to provide new safer and more effective drugs that are simple to administer and cheaper when compared to current drug

Caracterización preliminar de frutos de granada china (Passiflora ligularis Juss.) en Hueyapan y Teziutlán, Puebla

En la Sierra Nororiental de Puebla, México, los frutos de granada china son muy apreciados por la población local, pero existen pocos datos sobre su calidad hortofrutícola. Con el fin de iniciar la selección de individuos productores de frutos de buena calidad, se tomaron como muestra diez frutos de 20 plantas, cinco de cada localidad, Talzinta, Nexpan, Tanamacoyan y Mexcalcuautla, para analizarlos física (peso, diámetro, color, porcentaje de los componentes del fruto) y bioquímicamente (sólidos solubles totales, pH, acidez titulable, densidad del jugo). El valor medio para peso de frutos varió de 85 a 57 g; el porcentaje de pulpa de 81 a 51%; y el contenido de sólidos solubles totales (SST) fue de 17.5 a 12.2 ºB. El análisis de conglomerados, a una distancia euclidiana de 12.6, formó cinco grupos; en los grupos 2, 3 y 4 se observaron frutos de mayor tamaño (+ 75 g), con altos porcentajes de pulpa (60%) y valores aceptables de SST (14 ºB); éstos fueron los colectados en Talzinta y Nexpan. El análisis de componentes principales (CP) indicó que los primeros cinco CP explicaron el 75% de la variabilidad observada; siendo 25 y 18% la variabilidad que explican los CP 1 y CP 2, respectivamente. CP 1 estuvo altamente influenciado por el diámetro polar (0.900), luminosidad (-0.767) y el peso fresco del fruto (0.750); el CP 2 se relacionó con porcentaje de pulpa (0.866), porcentaje de cáscara (-0.866) y porcentaje de semillas (0.857). Esta información permitirá iniciar la selección de individuos productores de fruto de buena calidad, en la región de Teziutlán, PueblaEn la Sierra Nororiental de Puebla, MÈxico, los frutos de granada china son muy apreciados por la poblaciÛn local, pero existen pocos datos sobre su calidad hortofrutÌcola. Con el fin de iniciar la selecciÛn de individuos productores de frutos de buena calidad, se tomaron como muestra diez frutos de 20 plantas, cinco de cada localidad, Talzinta, Nexpan, Tanamacoyan y Mexcalcuautla, para analizarlos fÌsica (peso, di·metro, color, porcentaje de los componentes del fruto) y bioquÌmicamente (sÛlidos solubles totales, pH, acidez titulable, densidad del jugo). El valor medio para peso de frutos variÛ de 85 a 57 g; el porcentaje de pulpa de 81 a 51%; y el contenido de sÛlidos solubles totales (SST) fue de 17.5 a 12.2 ºB. El an·lisis de conglomerados, a una distancia euclidiana de 12.6, formÛ cinco grupos; en los grupos 2, 3 y 4 se observaron frutos de mayor tamaÒo (+ 75 g), con altos porcentajes de pulpa (60%) y valores aceptables de SST (14 ºB); Èstos fueron los colectados en Talzinta y Nexpan. El an·lisis de componentes principales (CP) indicÛ que los primeros cinco CP explicaron el 75% de la variabilidad observada; siendo 25 y 18% la variabilidad que explican los CP 1 y CP 2, respectivamente. CP 1 estuvo altamente influenciado por el di·metro polar (0.900), luminosidad ( 0.767) y el peso fresco del fruto (0.750); el CP 2 se relacionÛ con porcentaje de pulpa (0.866), porcentaje de c·scara ( 0.866) y porcentaje de semillas (0.857). Esta informaciÛn permitir· iniciar la selecciÛn de individuos productores de fruto de buena calidad, en la regiÛn de Teziutl·n, Puebla

Photophysical properties of [(norharmane)Re(CO)3 (L)]+ complexes (L = bpy, phen or dppz). Redox behavior of the excited states and their interaction with Calf Thymus DNA

The photochemical and photophysical properties of [(nHo)Re(CO)3(L)]+ complexes, where nHo = 9H-pyrido[3,4-b]indole and L = 2,2′ bipyridine (bpy), 1,10 phenantroline (phen) or dipyridil[3,2-a:2′3′-c]phenazine (dppz) were investigated by Laser Flash Photolysis (LFF) and Pulse Radiolysis (PR) techniques. While complexes with L = bpy or phen show absorption transients compatible with MLCTRe→L excited states, [(nHo)Re(CO)3(dppz)]+ showed an excited state assignable to a dppz-centered, 3ππ*dppz. In aqueous solutions, the last complex does not generate any absorption transient. However, when Calf thymus DNA was added, the same absorption spectrum was obtained. These results suggest that this complex can intercalate into DNA. The species generated in either reductive or oxidative conditions in LFF experiments were compared with those obtained in PR. Also, the quenching rate constants (kq) of the excited states with MV2+ were calculated. The intercalation of the [(nHo)Re(CO)3(dppz)]+ into DNA, increases kq ∼100 times. This result is rationalized in terms of the conditions created by the intercalation using the biopolymer as a well-organized matrix.Fil: Maisuls, Iván. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Cabrerizo, Franco Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Lappin, Alexander G.. University of Notre Dame-Indiana; Estados UnidosFil: Ruiz, Gustavo Teodosio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Ferraudi, Guillermo J.. University of Notre Dame-Indiana; Estados Unido

Characterization and distribution of sedimentary facies of Cartagena Bay, Colombia.

En el análisis sedimentológico de 253 muestras de sedimentos de fondo y borde de playa de la Bahía de Cartagena, se identificaron 26 facies sedimentarias. Las muestras fueron tomadas con draga tipo Van Veen para el fondo, multimuestreador de sedimento tipo Beeker y apiques para los bordes de playa. Las muestras fueron tamizadas y se obtuvieron 15 categorías de acuerdo al tamaño de grano, posteriormente se realizó el análisis de carbonato de calcio (CaCO3) usando el calcímetro de Bernard. Los sedimentos fueron clasificados de acuerdo con el tamaño medio de grano y el contenido de CaCO3, para definir las facies sedimentarias existentes, donde la facies lodo litoclástico es la más representativa y se distribuye en la bahía interna y externa; al norte y sur de la Isla de Tierra Bomba. Se encontró que durante los últimos 30 años la distribución de las facies sedimentarias ha experimentado variaciones significativas: en la bahía interna ha disminuido el contenido de CaCO3 y al suroeste ha disminuido el tamaño de grano y el contenido de CaCO3; como resultado del creciente aporte de sedimentos del Canal de Dique y las condiciones oceanográficas presentes. Estas condiciones hidrodinámicas favorecen la meteorización y erosión de las formaciones coralinas presentes en el Caribe Colombiano.In the sedimentological analysis of 253 sediment samples from the edges and the bottom of the Cartagena bay, we identified 26 sedimentary facies. Samples were taken with Van Veen dredge for the bottom sediment Beeker multisampler and test pits for shorelines. Using the Bernard calcimeter we carried out the calcium carbonate (CaCO3) analysis in every sieved sample. Sediments were classified according to the average grain size and content of CaCO3, to define the existing sedimentary facies, where mud litoclast facies was the most representative and distributed to the north and south of the Tierra Bomba in the internal and external bay. We found that during the past 30 years the distribution of sedimentary facies has experienced significant changes: in the inner bay the content of CaCO3 has decreased and in the southwest the grain size and content of CaCO3 have decreased, as a result of the sediments contribution from Canal del Dique and present oceanographic conditions. These hydrodynamic conditions contribute to the weathering and erosion of coral formations present in the Colombian CaribbeanFil: Franco Arias, Diana Aillen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Geológico del Sur; Argentina. Universidad Industrial de Santander; ColombiaFil: Restrepo López, J. C.. Universidad del Norte; ColombiaFil: Sanabria Ruiz, N. Y.. Universidad Industrial de Santander; ColombiaFil: Gutierrez, Julio C.. Centro de Investigaciones Oceanográficas e Hidrográficas; Colombi

Connectivity, neutral theories and the assessment of species vulnerability to global change in temperate estuaries

One of the main adaptation strategies to global change scenarios, aiming to preserve ecosystem functioning and biodiversity, is to maximise ecosystem resilience. The resilience of a species metapopulation can be improved by facilitating connectivity between local populations, which will prevent demographic stochasticity and inbreeding. The objective of this investigation is to estimate the degree of connectivity among estuarine species along the north-eastern Iberian coast, in order to assess community vulnerability to global change scenarios. To address this objective, two connectivity proxy types have been used based upon genetic and ecological drift processes: 1) DNA markers for the bivalve cockle (Cerastoderma edule) and seagrass Zostera noltei, and 2) the decrease in the number of species shared between two sites with geographic distance; neutral biodiversity theory predicts that dispersal limitation modulates this decrease, and this has been explored in estuarine plants and macroinvertebrates. Results indicate dispersal limitation for both saltmarsh plants and seagrass beds community and Z. noltei populations; this suggests they are especially vulnerable to expected climate changes on their habitats. In contrast, unstructured spatial pattern found in macroinvertebrate communities and in C. edule genetic populations in the area suggests that estuarine soft-bottom macroinvertebrates with planktonic larval dispersal strategies may have a high resilience capacity to moderate changes within their habitats. Our findings can help environmental managers to prioritise the most vulnerable species and habitats to be restored

Effect of Chain Polydispersity on the Elasticity of Disordered Polymer Networks

Due to their unique structural and mechanical properties, randomly cross-linked polymer networks play an important role in many different fields, ranging from cellular biology to industrial processes. In order to elucidate how these properties are controlled by the physical details of the network (e.g., chain-length and end-to-end distributions), we generate disordered phantom networks with different cross-linker concentrations C and initial densities ρinit and evaluate their elastic properties. We find that the shear modulus computed at the same strand concentration for networks with the same C, which determines the number of chains and the chain-length distribution, depends strongly on the preparation protocol of the network, here controlled by ρinit. We rationalize this dependence by employing a generic stress-strain relation for polymer networks that does not rely on the specific form of the polymer end-to-end distance distribution. We find that the shear modulus of the networks is a nonmonotonic function of the density of elastically active strands, and that this behavior has a purely entropic origin. Our results show that if short chains are abundant, as it is always the case for randomly cross-linked polymer networks, the knowledge of the exact chain conformation distribution is essential for correctly predicting the elastic properties. Finally, we apply our theoretical approach to literature experimental data, qualitatively confirming our interpretations

Activity/inactivity circadian rhythm shows high similarities between young obesity-induced rats and old rats

The objective of the present study was to compare differences between elderly rats and young obesity-induced rats in their activity/inactivity circadian rhythm. The investigation was motivated by the differences reported previously for the circadian rhythms of both obese and elderly humans (and other animals), and those of healthy, young or mature individuals. Three groups of rats were formed: a young control group which was fed a standard chow for rodents; a young obesity-induced group which was fed a high-fat diet for four months; and an elderly control group with rats aged 2.5 years that was fed a standard chow for rodents. Activity/inactivity data were registered through actimetry using infrared actimeter systems in each cage to detect activity. Data were logged on a computer and chronobiological analysis were performed. The results showed diurnal activity (sleep time), nocturnal activity (awake time), amplitude, acrophase, and interdaily stability to be similar between the young obesity-induced group and the elderly control group, but different in the young control group. We have concluded that obesity leads to a chronodisruption status in the body similar to the circadian rhythm degradation observed in the elderly

A Comprehensive Study of the WRKY Transcription Factor Family in Strawberry

WRKY transcription factors play critical roles in plant growth and development or stress responses. Using up-to-date genomic data, a total of 64 and 257 WRKY genes have been identified in the diploid woodland strawberry, Fragaria vesca, and the more complex allo-octoploid commercial strawberry, Fragaria × ananassa cv. Camarosa, respectively. The completeness of the new genomes and annotations has enabled us to perform a more detailed evolutionary and functional study of the strawberry WRKY family members, particularly in the case of the cultivated hybrid, in which homoeologous and paralogous FaWRKY genes have been characterized. Analysis of the available expression profiles has revealed that many strawberry WRKY genes show preferential or tissue-specific expression. Furthermore, significant differential expression of several FaWRKY genes has been clearly detected in fruit receptacles and achenes during the ripening process and pathogen challenged, supporting a precise functional role of these strawberry genes in such processes. Further, an extensive analysis of predicted development, stress and hormone-responsive cis-acting elements in the strawberry WRKY family is shown. Our results provide a deeper and more comprehensive knowledge of the WRKY gene family in strawberry