283 research outputs found

    Classical noise assists the flow of quantum energy by `momentum rejuvenation'

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    An important challenge in quantum science is to fully understand the efficiency of energy flow in networks. Here we present a simple and intuitive explanation for the intriguing observation that optimally efficient networks are not purely quantum, but are assisted by some interaction with a `noisy' classical environment. By considering the system's dynamics in both the site-basis and the momentum-basis, we show that the effect of classical noise is to sustain a broad momentum distribution, countering the depletion of high mobility terms which occurs as energy exits from the network. This picture predicts that the optimal level of classical noise is reciprocally related to the linear dimension of the lattice; our numerical simulations verify this prediction to high accuracy for regular 1D and 2D networks over a range of sizes up to thousands of sites. This insight leads to the discovery that dramatic further improvements in performance occur when a driving field targets noise at the low mobility components

    Mathematical Model for finding Locations and Sizes of Company Warehouses

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    A large Canadian company with headquarters in the Greater Toronto area handles approximately 20,000 products provided by about 150 vendors supplying over 200 branches. To minimize transportation and storage costs, this company is planning to open a second warehouse. Decisions like this are often made with the aid of the solution to an mathematical optimization problem. This project will determine the size and location of its next warehouse. In this project, we will formulate and solve this large optimization problem taking into account fixed land and building costs, variable operation costs, and transportation costs. We will suggest the new location and determine which branches will be supplied by the new and existing warehouses. Preliminary research for the model has determined necessary and sufficient variable constraints which will yield an accurate solution

    Evidence of tryglyceride-phase incorporation into artificial bilayers for studying lipid droplets biogenesis

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    Lipid Droplets (LD) are intracelular structures consisting on an apolar lipid core - composed mainly of triglycerides (TG) and steryl esters- which is surrounded by a phospholipid and protein monolayer. LDs originate in the ER bilayer, where TG synthesis concludes. The mechanisms underlying TG nucleation, size maduration and budding-off from the ER membrane are a matter of current investigations and the role of dewetting from cytosolic-bilayer interface appears to play a critical role. In order to contrast the nano-sized "blisters" of TG that some authors predict1, here we formed free-standing bilayers by transferring films of a monolayer of mixed phosphatidylcholine(EPC)/TG in coexistence with TG microlenses (i.e. an excluded TG phase floating in the surface). These membranes were characterized by adding them the solvatochromic fluorescent probe Nile Red (NR) and observing them under spectral confocal microscope. Such bilayers exhibit fluorescence emission spectra comparable of bilayers of vesicles with similar composition (POPC and TO). By comparison with literature data and fluorescence spectra of EPC and TG monolayers, the peaks could be assigned to different phases, namely 1) PC membranes (λemmax=630 nm ) bilayer and bilayer) and 2) TG isotropic phase (λemmax=570 nm ). No microscopic structures could be observed at λ emmax=570 nm. Diffusion of NR under this TG phase was characterized using FRAP analysis yielding values (D=2 μm2s ) typical of model bilayer membranes, suggesting that the probe is diffusing in a 2D structure. This system appears appropiate for describing which is the distribution of the TG phase, that is, homogeneously among the intrabilayer space or in nanoscopic "blisters", by evaluating diffusion times obtained by FCS and FRAP.Fil: Caruso, Benjamin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaFil: Mangiarotti, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Wilke, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Perillo, Maria Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaXLVII Reunión Anual de la Sociedad Argentina de BiofísicaLa PlataArgentinaSociedad Argentina de BiofísicaUniversidad Nacional de La plata. Facultad de Ciencias Médica

    Facilitating Pre-Service Teachers to Engage Emergent Bilinguals in Productive Struggle

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    This study utilized a multiple case study with qualitative research to examine how Pre-service teachers (PSTs) might engage Emergent Bilinguals (EBs) in productive struggle—grappling to solve problems (Warshauer, 2015). The researchers created a rubric based on Warshauer’s (2015) case study to record the types of questions PSTs asked as they tutored fourth grade EBs. Warshauer (2015) claimed PSTs should allow students more wait time and ask questions. She referred to such questions as affordance and probing guidance, which facilitates productive struggle. In order to discover more about the PSTs’ thinking, the researchers interviewed the PSTs before and after their first, third, and seventh lesson. The researchers’ findings are that the PSTs struggled to incorporate more affordance and probing guidance-based questions as the semester progressed. However, PSTs use of telling based questions decreased during the semester. Another finding was two of the EBs spoke only English at the beginning of the semester, but later used code switching during the lessons. Perhaps the students felt more comfortable with their surroundings, and speaking in Spanish helped facilitate them to engage in productive struggle. Furthermore, PSTs utilized culturally relevant teaching strategies during their lessons and created an environment to encourage positive mindsets for learning mathematics. Implications are teacher educators should teach PSTs how to engage all students in productive struggle

    V-shape" molecular configuration of wax esters of jojoba oil in a Langmuir film model

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    The aim of the present work was to understand the interfacial properties of a complex mixture of wax esters (WEs) obtained from Jojoba oil (JO). Previously, on the basis of molecular area measurements, a hairpin structure was proposed as the hypothetical configuration of WEs, allowing their organization as compressible monolayers at the air-water interface. In the present work, we contributed with further experimental evidence by combining surface pressure (π), surface potential (ΔV), and PM-IRRAS measurements of JO monolayers and molecular dynamic simulations (MD) on a modified JO model. WEs were self-assembled in Langmuir films. Compression isotherms exhibited π lift-off at 100 Å 2 /molecule mean molecular area (A lift-off ) and a collapse point at π c ≈ 2.2 mN/m and A c ≈ 77 Å 2 /molecule. The ΔV profile reflected two dipolar reorganizations, with one of them at A > A lift-off due to the release of loosely bound water molecules and another one at A c < A < A lift-off possibly due to reorientations of a more tightly bound water population. This was consistent with the maximal SP value that was calculated according to a model that considered two populations of oriented water and was very close to the experimental value. The orientation of the ester group that was assumed in that calculation was coherent with the PM-IRRAS behavior of the carbonyl group with the C=O oriented toward the water and the C-O oriented parallel to the surface and was in accordance with their orientational angles (∼45 and ∼90°, respectively) determined by MD simulations. Taken together, the present results confirm a V shape rather than a hairpin configuration of WEs at the air-water interface.Fil: Caruso, Benjamin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química. Cátedra de Química Biológica; ArgentinaFil: Martini, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Pickholz, Mónica Andrea. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Perillo, Maria Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química. Cátedra de Química Biológica; Argentin

    Aβ-Amyloid fibrils are self-triggered by the interfacial lipid environment and low peptide content

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    We studied the surface properties of Aβ(1-40) amyloid peptides mixed with 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) (liquid state) or 1,2-disteraoyl-phosphatidylcholine (DSPC) (solid state) phospholipids by using nanostructured lipid/peptide films (Langmuir monolayers). Pure Aβ(1-40) amyloid peptides form insoluble monolayers without forming fibril-like structures. In a lipid environment [phospholipid/Aβ(1-40) peptide mixtures], we observed that both miscibility and stability of the films depend on the peptide content. At low Aβ(1-40) amyloid peptide proportion (from 2.5 to 10% of peptide area proportion), we observed the formation of a fibril-like structure when mixed only with POPC lipids. The stability acquired by these mixed films is within 20-35 mN·m-1 compatible with the equivalent surface pressure postulated for natural biomembranes. Fibrils are clearly evidenced directly from the monolayers by using Brewster angle microscopy. The so-called nanostructured fibrils are thioflavin T positive when observed by fluorescence microscopy. The amyloid fibril network at the surface was also evidenced by atomic force microscopy when the films are transferred onto a mica support. Aβ(1-40) amyloid mixed with the solid DSPC lipid showed an immiscible behavior in all peptide proportions without fibril formation. We postulated that the amyloid fibrillogenesis at the membrane can be dynamically nano-self-triggered at the surface by the quality of the interfacial environment, that is, the physical state of the water-lipid interface and the relative content of amyloid protein present at the interface.Fil: Bolaño Alvarez, Alain. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Caruso, Benjamin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Química. Cátedra de Química Biológica; ArgentinaFil: Rodriguez, Pablo Eduardo Andres. Provincia de Córdoba. Ministerio de Ciencia y Técnica; ArgentinaFil: Petersen, Steffen B.. Aalborg University; DinamarcaFil: Fidelio, Gerardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentin

    Biogenesis and Breakdown of Lipid Droplets in Pathological Conditions

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    Lipid droplets (LD) have long been considered as mere fat drops; however, LD have lately been revealed to be ubiquitous, dynamic and to be present in diverse organelles in which they have a wide range of key functions. Although incompletely understood, the biogenesis of eukaryotic LD initiates with the synthesis of neutral lipids (NL) by enzymes located in the endoplasmic reticulum (ER). The accumulation of NL leads to their segregation into nanometric nuclei which then grow into lenses between the ER leaflets as they are further filled with NL. The lipid composition and interfacial tensions of both ER and the lenses modulate their shape which, together with specific ER proteins, determine the proneness of LD to bud from the ER toward the cytoplasm. The most important function of LD is the buffering of energy. But far beyond this, LD are actively integrated into physiological processes, such as lipid metabolism, control of protein homeostasis, sequestration of toxic lipid metabolic intermediates, protection from stress, and proliferation of tumours. Besides, LD may serve as platforms for pathogen replication and defense. To accomplish these functions, from biogenesis to breakdown, eukaryotic LD have developed mechanisms to travel within the cytoplasm and to establish contact with other organelles. When nutrient deprivation occurs, LD undergo breakdown (lipolysis), which begins with the LD-associated members of the perilipins family PLIN2 and PLIN3 chaperone-mediated autophagy degradation (CMA), a specific type of autophagy that selectively degrades a subset of cytosolic proteins in lysosomes. Indeed, PLINs CMA degradation is a prerequisite for further true lipolysis, which occurs via cytosolic lipases or by lysosome luminal lipases when autophagosomes engulf portions of LD and target them to lysosomes. LD play a crucial role in several pathophysiological processes. Increased accumulation of LD in non-adipose cells is commonly observed in numerous infectious diseases caused by intracellular pathogens including viral, bacterial, and parasite infections, and is gradually recognized as a prominent characteristic in a variety of cancers. This review discusses current evidence related to the modulation of LD biogenesis and breakdown caused by intracellular pathogens and cancer.Fil: Fader Kaiser, Claudio Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Romano, Patricia Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Vanrell, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Pocognoni, Cristián Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Jacob, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Caruso, Benjamin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaFil: Delgui, Laura Ruth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; Argentin

    Generalized dynamical density functional theory for classical fluids and the significance of inertia and hydrodynamic interactions

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    We study the dynamics of a colloidal fluid including inertia and hydrodynamic interactions, two effects which strongly influence the non-equilibrium properties of the system. We derive a general dynamical density functional theory (DDFT) which shows very good agreement with full Langevin dynamics. In suitable limits, we recover existing DDFTs and a Navier-Stokes-like equation with additional non-local terms.Comment: 5 pages, 4 figures, 4 supplementary movie files, I supplementary pd
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