Fasting induces modifications of the endoplasmic reticulum in intestinal cells

The polymorphism of the endoplasmic reticulum (ER) in epithelial cells with different transport functions such as the enterocyte suggests that the ER may be involved in some way in molecular transport. To further access this possibility, we examined the ER from the intestine of winter flounder, Pseudopleuronectes americanus, a species which undergoes an annual fast of approximately 6 months' duration, a time during which previous work indicates nutrient carrier number does not change. Fish from June (feeding) and January (8–10 weeks fasted) were sampled. Tissues from the pyloric caeca, foregut, midgut, and hindgut were prepared for electron microscopy using two techniques of staining. Cell height was unaltered in any section, although microvillar length shortened variably. Cellular organization, including position of nuclei, number and distribution of mitochondria, and presence of basolateral membranes, did not change. The ER appeared equally abundant in June and January. However, use of the osmium impregnation technique, which is specific for ER cisternal contents, revealed a change in the impregnation of ER, from a heavily impregnated network in summer to little or no impregnation in winter. These results suggest that a shift in function of the ER had occurred when nutrient transport ceased, and supports a role of the ER in nutrient transport.     

Influence of the insecticide pyriproxyfen on the flight muscle differentiation of Apis mellifera (Hymenoptera, Apidae)

The Brazilian africanized Apis mellifera is currently considered as one of the most important pollinators threatened by the use of insecticides due to its frequent exposition to their toxic action while foraging in the crops it pollinated. Among the insecticides, the most used in the control of insect pragues has as active agent the pyriproxyfen, analogous to the juvenile hormone (JH). Unfortunately the insecticides used in agriculture affect not only the target insects but also beneficial nontarget ones as bees compromising therefore, the growth rate of their colonies at the boundaries of crop fields. Workers that forage for provisions in contaminated areas can introduce contaminated pollen or/and nectar inside the beehives. As analogous to JH the insecticide pyriproxyfen acts in the bee's larval growth and differentiation during pupation or metamorphosis timing. The flighty muscle is not present in the larvae wingless organisms, but differentiates during pupation/metamorphosis. This work aimed to investigate the effect of pyriproxyfen insecticide on differentiation of such musculature in workers of Brazilian africanized honey bees fed with artificial diet containing the pesticide. The results show that the bees fed with contaminated diet, independent of the insecticide concentration used, show a delay in flight muscle differentiation when compared to the control.     

CBED and LACBED: characterization of antiphase boundaries

Convergent-beam electron diffraction (CBED) and large-angle convergent-beam electron diffraction (LACBED) techniques are well adapted to the characterization of several types of crystal defects. In fact, dislocations, grain boundaries and stacking faults have already been successfully characterized with these methods. In the present paper, we describe the CBED and LACBED characterization of another type of crystal defect showing a special interest in materials science: antiphase boundaries (APBs). The first part of the paper is devoted to the determination of the effects of antiphase boundaries on CBED and LACBED patterns that could be expected from a theoretical point of view. It indicates that the superlattice excess lines present on these patterns are split into two lines with equal intensity when the incident beam is located on an APB. In the second part, we experimentally test these theoretical predictions on a specimen showing two different known types of antiphase boundaries. In a third part we indicate how these methods could be used to identify unknown APBs in a specimen. Finally, the advantages and disadvantages of both methods for the characterization of antiphase boundaries are discussed.     

Diamonds are a cryosectioner's best friend

High-pressure frozen Golden Delicious apple leaves were cryosectioned at low temperature with diamond knives. Good cryosections were obtained by optimizing the cutting parameters, i.e. sectioning temperature, mechanical stability of the sample, and sectioning velocity. Cutting artefacts were minimized by reducing the electrostatic interactions between the knife surface and the cryosection. This was accomplished by sectioning the sample in the presence of an ionization electrode. The ionization device, with a primary voltage of 7–8 kV, produces positively and negatively charged nitrogen ions which neutralize the surface charges of the knife and the section. This minimizes the friction on the knife surface and results in ultrathin sections without crevasses or knife marks. Compression of the sections could be minimized, but not avoided, by reducing the knife angle to 30°. Improved contrast of the frozen-hydrated sections was obtained with the Zeiss EM 902 energy-filter microscope operated in the zero-loss mode.     

Load balancing routing with queue overflow prediction for WSNs

The ease of deployment of Wireless Sensor Networks (WSNs) makes them very popular and useful for data collection applications. Nodes often use multihop communication to transmit data to a collector node. The next hop selection in order to reach the final destination is done following a routing policy based on a routing metric. The routing metric value is exchanged via control messages. Control messages transmission frequency can reduce the network bandwidth and affect data transmission. Some approaches like trickle algorithm have been proposed to optimize the network control messages transmission. In this paper, we propose a collaborative load balancing algorithm (CoLBA) with a prediction approach to reduce network overhead. CoLBA is a queuing delay based routing protocol that avoids packet queue overflow and uses a prediction approach to optimize control messages transmission. Simulation results on Cooja simulator show that CoLBA outperforms other existing protocols in terms of delivery ratio and queue overflow while maintaining a similar end-to-end delay.

     

Tuning Thermal Transport Through Atomically Thin Ti3C2Tz MXene by Current Annealing in Vacuum

Heat transport across vertical interfaces of heterogeneous 2D materials is usually governed by the weak Van der Waals interactions of the surface‐terminating atoms. Such interactions play a significant role in thermal transport across transition metal carbide and nitride (MXene) atomic layers due to their hydrophilic nature and variations in surface terminations. Here, the metallicity of atomically thin Ti₃C₂T_z MXene, which is also verified by scanning tunneling spectroscopy for the first time, is exploited to develop a self‐heating/self‐sensing platform to carry out direct‐current annealing experiments in high (<10^?8 bar) vacuum, while simultaneously evaluating the interfacial heat transport across a Ti₃C₂T_z/SiO₂ interface. At room temperature, the thermal boundary conductance (TBC) of this interface is found, on average, to increase from 10 to 27 MW m^?2 K^?1 upon current annealing up to the breakdown limit. In situ heating X‐ray diffraction and X‐ray photo‐electron spectroscopy reveal that the TBC values are mainly affected by interlayer and interface spacing due to the removal of absorbents, while the effect of surface termination is negligible. This study provides key insights into understanding energy transport in MXene nanostructures and other 2D material systems.     

Theoretical analysis of the frictional losses in magnetohydrodynamic microflows considering slippage

In this article, we study the frictional losses in magnetohydrodynamic (MHD) microflows by analyzing the Poiseuille number defined through the Darcy–Weisbach friction factor. We consider two-dimensional fully developed flow models characteristic of MHD micropumps including the Hartmann braking effect and the existence of slippage. Unlike the purely hydrodynamic case, in MHD flows the Poiseuille number depends not only on the aspect ratio but also on the physical properties of the fluid and the externally applied magnetic field. Three different combinations of boundary conditions (slip and no-slip) are investigated. Calculations show that the Poiseuille number is considerably reduced as the dimensionless slip length is increased, while it increases as Hartmann number does. The obtained results are consistent with previous models and are helpful for the design of magnetohydrodynamic microflow devices.

     

Tuning Memristivity by Varying the Oxygen Content in a Mixed Ionic–Electronic Conductor

The rising interest shown for adaptable electronics and brain‐inspired neuromorphic hardware increases the need for new device architectures and functional materials to build such devices. The rational design of these memory components also benefits the comprehension and thus the control over the microscopic mechanisms at the origin of memristivity. In oxide‐based valence‐change memories, the control of the oxygen drift and diffusion kinetics is a key aspect in obtaining the gradual analog‐type change in resistance required for artificial synapse applications. However, only a few devices are designed with this in mind, as they are commonly built around ionic insulating active materials. This shortcoming is addressed by using a mixed ionic–electronic conductor as functional memristive material. This work demonstrates how the oxygen content in La₂NiO_4+δ (L2NO4), tuned through post‐annealing treatments, has a critical influence on the memory characteristics of L2NO4‐based memristive devices. The presence of interstitial oxygen point defects in L2NO4 affects both its structure and electrical properties. High oxygen stoichiometry in the pristine state leads to an increased electrical conductivity, ultimately resulting in an improved memory window with highly multilevel, analog‐type memory programing capabilities, desirable for analog computing and synaptic applications in particular.     

Unprecedented Improvement of Single Li‐Ion Conductive Solid Polymer Electrolyte Through Salt Additive

Solid‐state lithium metal (Li°) batteries (SSLMBs) are believed to be the most promising technologies to tackle the safety concerns and the insufficient energy density encountered in conventional Li‐ion batteries. Solid polymer electrolytes (SPEs) inherently own good processability and flexibility, enabling large‐scale preparation of SSLMBs. To minimize the growth of Li° dendrites and cell polarization in SPE‐based SSLMBs, an additive‐containing single Li‐ion conductive SPE is reported. The characterization results show that a small dose of electrolyte additive (2 wt%) substantially increases the ionic conductivity of single Li‐ion conductive SPEs as well as the interfacial compatibility between electrode and SPE, allowing the cycling of SPE‐based cells with good electrochemical performance. This work may provide a paradigm shift on the design of highly cationic conductive electrolytes, which are essential for developing safe and high‐performance rechargeable batteries.     

Interactive web interfaces modeling,simulation and analysis using Colored Petri Nets

Software and Systems Modeling - Interaction modeling is a relevant activity during software development processes. Created relying on Petri Nets theory and aiming to represent discrete time events,...