140,931 research outputs found
Just Green Transitions: Between Terminological Inexactitudes, Conceptual Fragmentation, and the Exigency for a Theoretical Framework
No full textThe European Green Deal is promoting a twinned transition which is expected to be
just and green. Various related terminologies have gained ground without being precisely defined
or commonly agreed upon. Following an interdisciplinary exploratory approach, this contribution discusses the terminological inexactitudes which could risk a common conceptualisation, operationalisation, and implementation of the so-called Just Green Transitions. Through a critical interpretative literature review, this contribution highlights the conceptual fragmentation of these three dimensions: just as a polylemma of socio-spatial-temporal justice, green as a non-replication of pseudo-fashionable labels, and transitions as meta, multiple, and multilevel paths of institutional and social changes
La Prossimità di una Salute Urbana Inclusiva
No full textL’opportunità per le città di diventare più verdi, più sostenibili, più resilienti contiene il rischio di risolversi in operazioni immobiliari di immagine o di creare nuove disegua- glianze, invece di soddisfare il concetto di “non lasciare indietro nessuno” che è alla ba- se del Green Deal Europeo e degli SDGs delle Nazioni Unite. Le grandi transizioni e trasformazioni verdi richiedono giustizia sociale e spaziale, volontà e sforzi collettivi. Le politiche sostenibili, i modi di governare, gestire, pianificare e costruire le nostre città possono essere efficaci e inclusivi solo nella misura in cui le politiche pubbliche e urbane sono basate su evidenze scientifiche e sono imperniate su una piena partecipazione dei cittadini fin dall’inizio
Mechanical Harvesting of Citrus Fruits for Fresh Market with a Trunk Shaker and a Hand-Held Petrol Shaker
No full textThe original publication is available at www.actahort.orgHarvesting is one of the more expensive tasks in a Spanish citrus crop because it is done manually. Spanish researchers are investigating the possibilities of mechanical harvesting of citrus cultivated under Spanish conditions. This paper compares two different strategies for mechanical harvesting: the use of a trunk shaker and the use of a hand-held petrol shaker. Tests were performed in lemon, orange and mandarin groves. Tree spacing was 6-7 m between rows and 2.5-4.5 m in the row. Trees were 2.5-3 m height and had a 0.35-0.70 m branch-free trunk. The harvesting equipment was (a) an inertial tree trunk shaker that produced displacements of 2-3 cm and frequencies of 10-25 Hz and (b) a hand-held shaker with a stroke of 6 cm and a variable frequency between 10 and 25 Hz. Fruit fell on canvases with different shock-absorbing materials. The overall trunk shaker fruit detachment capacity was 70%. Fruit detachment was influenced more by tree architecture than by fruit attachment force. Trees with a favorable branch disposition allowed fruit detachment percentages up to 90%. The hand-held shaker had higher fruit removal efficiency on shaken branches (76%) but a lower efficiency on the whole tree (63%) because of its low efficiency in transmitting vibration to thin and willowy branches. Since fruit are for the fresh market, two quality parameters were evaluated: a) fruit detachment point and b) fruit damage. The majority of the fruit was detached with calyx or with peduncle attached, which means that fruit was good for the fresh market. Fruit susceptibility to damage mainly depended on the variety.Torregrosa Mira, A.; Ortiz Sánchez, MC.; Martin, B.; Moreno, R.; Molto, E.; Chueca, P. (2012). Mechanical Harvesting of Citrus Fruits for Fresh Market with a Trunk Shaker and a Hand-Held Petrol Shaker. Acta Horticulturae. 965:49-53. doi:10.17660/ActaHortic.2012.965.3S495396
Diseño preliminar de shaker hidráulico de 1 grado de libertad
No full textEl siguiente trabajo presenta el diseño preliminar de un shaker hidráulico de un grado de libertad para análisis de componentes de uso aeroespacial. En el mismo se presentan los análisis estructurales y dinámicos preliminares utilizados para definir los componentes principales del sistema y las capacidades del mismo. El conjunto de análisis fue realizado mediante simulaciones de elementos finitos, las cuales permitieron obtener frecuencias naturales, modos de vibrar y mapas de tensiones de componentes del sistema. Mediante el análisis de los resultados se pretende obtener una configuración mecánica inicial, definir componentes principales y condiciones de operación para luego realizar la ingeniería de detalle y control
Mechanical Thinning of Mandarins with a Branch Shaker
No full text[EN] Thinning is the process of removing some flowers or fruit to increase fruit size at harvest. In the Valencia region of Spain, the thinning operation for citrus fruit (Citreae) is performed for some mandarin varieties. This is always performed manually; however, this method is very expensive. The goal of this research study was to assess the mechanical thinning of mandarin ( Citrus reticulata) using a hand-held branch shaker. Different thinning treatments were conducted over a 3-year period. The gasoline-powered branch shaker was capable of detaching fruit four- to five-times faster than manual thinning. Final fruit size was significantly higher using manual and mechanical thinning compared with a no thinning treatment. Similar final fruit size was obtained with manual and mechanical thinning. However, no significant differences were found in final fruit yield by weight among no thinning, mechanical thinning, and manual thinning treatments. The use of a branch shaker could be recommended for thinning operations to increase efficiency, reduce labor costs, and obtain larger and higher-quality fruit.This work was supported by funding from the Instituto Nacional de Investigaciones Agrarias (INIA) and European FEDER (Project RTA2014-00025-C05-02). Fontestat provided the experimental fields.Ortiz Sánchez, MC.; Torregrosa, A.; Ortí García, E.; Balasch Parisi, S. (2020). Mechanical Thinning of Mandarins with a Branch Shaker. HortTechnology. 30(6):745-750. https://doi.org/10.21273/HORTTECH04451-20S74575030
Technische Maßnahmen zur Verbesserung der Züchtung von Dictyostelium discoideum
No full textLu Y. Technische Maßnahmen zur Verbesserung der Züchtung von Dictyostelium discoideum. Berichte aus der Biotechnologie. Aachen: Shaker; 2002
Das Opfer des Individuums und die Geschichte in den Stücken Bertolt Brechts und Heiner Müllers
No full textSuh Y-S. Das Opfer des Individuums und die Geschichte in den Stücken Bertolt Brechts und Heiner Müllers. Aachen: Shaker; 2002
Comparison of a Lightweight Experimental Shaker and an Orchard Tractor Mounted Trunk Shaker for Fresh Market Citrus Harvesting
No full textA designed lightweight experimental shaker successfully used to collect ornamental oranges has been tested to harvest fresh market citrus. The aim of this study was to evaluate the removal efficiency and operational times of this experimental device compared to an orchard trunk shaker. Three different collecting systems were studied. ‘Caracara’ citrus trees were tested. Removal efficiency, vibration parameters, fruit and tree damages, and fruit quality were measured. A high-speed camera was used to record operational times and determine cumulative removal percentage over vibration time. The canvases on the ground reduced the severe fruit damages but were not useful to protect against light damages. The experimental shaker produced a higher percentage of slightly damaged oranges. No significant differences in removal efficiency were found between the two harvesting systems. However, removal efficiency using the experimental device could be reduced by 40 percent and working time increase by more than 50 percent when access to the main branches was difficult. In agreement with previous results, the curve representing the branch cumulative removal percentage in time followed a sigmoidal pattern. A model was built showing that during the first 5 s more than 50 percent of the fruits were detached
Molecular mechanisms of the coupling of gating to voltage sensing in transmembrane proteins
No full textVoltage gated potassium ion (Kv) channels regulate action potentials of the nervous system by responding to changes in transmembrane voltage, enabling K+ transport across the membrane to restore cells to their resting potential. Comprised of four identical subunits, Kv channels contain four voltage sensing domains arranged on the periphery of a central pore domain. Each voltage sensor is comprised of four transmembrane helices, numbered S1 through S4. The S4 helix, containing four to six highly-conserved, positively-charged arginine or lysine residues, is responsible for voltage sensitivity in Kv channels. The pore domain consists of two transmembrane helices, S5 and S6. The S5 helix constitutes the periphery of the pore domain and is believed to be relatively immobile. The S6 helices, lining the interior of the channel, gate the protein and regulate K+ permeation. Because each subunit of Kv channels contains six transmembrane helices, they are often referred to as 6TM Kv channels.
The depolarization of an action potential is initiated as sodium ions enter the cell. At the cellular resting potential of -70 mV, potassium ion channels are closed, and the S4 helix is in its “down” state. As the electrochemical gradient changes, the S4 helices of Kv channels begin to reorient within the membrane. At the peak of the action potential (roughly +20 mV), the S4 helices exist in their “up” state. This conformational transition of the S4 helix is coupled to the pore domain via the S4-S5 linker, a short, amphipathic helix along the intracellular membrane-water interface. By bridging the C-terminus of the voltage sensor to the N-terminus of the pore domain, the S4-S5 linker couples the voltage sensitivity of the voltage sensor to K+ conduction in the pore domain.
Because they begin opening at voltages less than 0 mV, all crystal structures of Kv channels contain an open pore domain. With no structure in the closed conformation, the mechanism of gating in Kv channels remains unclear. Nevertheless, significant biophysical studies have revealed insights into both the closed conformation and the gating transition itself. In this dissertation, I will explore questions relevant to the gating mechanism in voltage gated potassium ion channels through fully-atomistic molecular dynamics (MD) simulations.
First, in Chapter 2, I will address the potential role of the 310 helical conformation found in the C-terminal end of S4 in the crystal structures of Kv channels. Spanning eight or more residues, these 310 helices are both uncharacteristically long and conserved in K+ channel crystal structures. By simulating the Kv1.2/2.1 chimera channel’s voltage sensor embedded in a lipid bilayer, I find that an alpha to 310 helical interconversion of the S4 helix reproduces many experimental measurements of the open and closed states of Kv channels.
In Chapter 3, I perform molecular dynamics simulations of the entire Kv1.2/2.1 chimera channel. First, I examine the impact of an alpha to 310 helical interconversion of the S4 helix on the pore domain of the channel. Though the results are consistent with the results in Chapter 2 (and the corresponding experimental measurements), I find that this secondary structural modification is insufficient to influence the pore domain of the channel on the timescale of my simulations. In the second half of Chapter 3, I use molecular dynamics simulations to generate a closed state model of the Kv1.2/2.1 chimera from luminescence resonance energy transfer (LRET) measurements of the closed conformation of KvAP. The resulting structure is indeed closed, and also recapitulates a number of experimentally determined measurements of the closed channel.
In Chapter 4, I focus on the pore domain. First, using targeted molecular dynamics simulations, I generate a transition between a closed model of the KvAP linker and pore domain to the open conformation. Then, using an umbrella sampling method, I quantify the energetics of the gating transition in KvAP and assess the physiological implications. In agreement with experimental studies of Kv channel energetics, I find that the open pore is roughly 2.7 kcal/mol lower in free energy than the closed conformation. The targeted molecular dynamics and umbrella sampling simulations reveal additional insights into the gating mechanism of KvAP.
Lastly, in Chapter 5, I use MD simulations to gain insights into the binding mechanism of VSTx1, a Kv channel inhibitor. By using the experimentally determined neutron scattering density profile of the VSTx1 toxin bound to a lipid bilayer as a restraint for molecular dynamics simulations, I recreate the experimental scattering density profile, and also offer insight into the binding of VSTx1 to a lipid membrane
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