Optimization of an innovative approach involving mechanical activation and acid digestion for the extraction of lithium from lepidolite

The recovery of lithium from hard rock minerals has received increased attention given the high demand for this element. Therefore, this study optimized an innovative process, which does not require a high-temperature calcination step, for lithium extraction from lepidolite. Mechanical activation and acid digestion were suggested as crucial process parameters, and experimental design and response-surface methodology were applied to model and optimize the proposed lithium extraction process. The promoting effect of amorphization and the formation of lithium sulfate hydrate on lithium extraction yield were assessed. Several factor combinations led to extraction yields that exceeded 90%, indicating that the proposed process is an effective approach for lithium recovery.     

The molecular architecture of cadherins in native epidermal desmosomes

Desmosomes are cadherin-based adhesive intercellular junctions, which are present in tissues such as heart and skin. Despite considerable efforts, the molecular interfaces that mediate adhesion remain obscure. Here we apply cryo-electron tomography of vitreous sections from human epidermis to visualize the three-dimensional molecular architecture of desmosomal cadherins at close-to-native conditions. The three-dimensional reconstructions show a regular array of densities at approximately 70 A intervals along the midline, with a curved shape resembling the X-ray structure of C-cadherin, a representative 'classical' cadherin. Model-independent three-dimensional image processing of extracted sub-tomograms reveals the cadherin organization. After fitting the C-cadherin atomic structure into the averaged sub-tomograms, we see a periodic arrangement of a trans W-like and a cis V-like interaction corresponding to molecules from opposing membranes and the same cell membrane, respectively. The resulting model of cadherin organization explains existing two-dimensional data and yields insights into a possible mechanism of cadherin-based cell adhesion.     

新型钢管混凝土柱-平板节点轴压性能研究(Ⅰ)——试验概况及结果分析

通过两组共15个试件的轴压试验，对节点区柱钢管不连通式钢管混凝土柱－平板节点的轴压性能进行了较为详尽的研究。介绍了试验的概况及主要的试验结果，并对影响该节点轴压承载力的因素进行了探讨，为该节点轴压承载力计算公式的建立提供了基础数据。     

Rip it up and start again: The rejection of a characterization of a phenomenon

In this paper, I investigate the nature of empirical findings that provide evidence for the characterization of a scientific phenomenon, and the defeasible nature of this evidence. To do so, I explore an exemplary instance of the rejection of a characterization of a scientific phenomenon: memory transfer. I examine the reason why the characterization of memory transfer was rejected, and analyze how this rejection tied to researchers’ failures to resolve experimental issues relating to replication and confounds. I criticize the presentation of the case by Harry Collins and Trevor Pinch, who claim that no sufficient reason was provided to abandon research on memory transfer. I argue that skeptics about memory transfer adopted what I call a defeater strategy, in which researchers exploit the defeasibility of the evidence for a characterization of a phenomenon.     

Carapace ontogeny of the bromeliad dwelling ostracod Elpidium bromeliarum Müller, 1880 (Crustacea: Ostracoda)

Ostracods have discontinuous development, marked by ecdyses, and determinate growth. Ontogenetic studies have suggested a pattern of nine postembryonic stages (eight juvenile phases and the adult) for the main freshwater ostracod superfamilies Cypridoidea, Cytheroidea and Darwinuloidea. However, cases of a supposed extra moult in the adult stage have been proposed for some ostracod species, which would amount to 10 postembryonic growth stages. One such example is Elpidium bromeliarum Müller, 1880, a cytheroidean that inhabits tank-bromeliads. The present study is aimed at investigating the ontogenetic development of E. bromeliarum using width and length measurements, as well as carapace and appendage morphology in order to test the existing hypothesis of an additional growth stage in adults of this species. Our results revealed nine postembryonic growth stages (eight juvenile and the adult), with sexual dimorphism beginning its expression in the last juvenile stage. Thus, the ontogenetic development of E. bromeliarum agrees with the overall pattern observed for podocopid ostracods and the hypothesis of 10 postembryonic growth stages was not corroborated. We argue that the inability to differentiate juveniles from adults, or different species from one another, may have misled to the assumption of an additional moult in E. bromeliarum.     

Discrimination between alternate membrane protein topologies in living cells using GFP/YFP tagging and pH exchange

Membrane protein function is determined by the relative organization of the protein domains with respect to the membrane. We have experimentally verified the topology of a protein with diverse orientations arising from a single primary sequence (the cellular prion protein, PrP^C), a novel somatostatin truncated receptor, and the Golgi-associated protein GPBP₉₁. Tagging with fluorescent proteins (FP) allows location of their expression at the plasma membrane or at endomembranes, but does not inform about their orientation. Exploiting the pH dependency of some FPs, we developed a pH exchange assay in which extracellularly exposed FPs are quenched by application of low pH buffer. We constructed standards to demonstrate and calibrate the assay, and the method was adapted for acidic organelle membrane proteins. This method can serve as a proof of concept, experimentally confirming and/or discriminating in living cells among theoretical topology predictions, providing the proportion of inside/outside orientation for proteins with multiple forms.     

cAMP in spermatozoa taken from different segments of rat epididymis.

Experimental evidence conclusively indicates that the epididymis is under endocrine control and plays an active role in the process of spermatic maturation.