The effect of secondary electrons on radiolysis as observed by in liquid TEM: The role of window material and electrical bias

The effect of window material on electron beam induced phenomena in liquid phase electron microscopy (LPEM) is an interesting yet under-explored subject. We have studied the differences of electron beam induced gold nanoparticle (AuNP) growth subject to three encapsulation materials: Silicon Nitride (Si3N4), carbon and formvar. We find Si3N4 liquid cells (LCs) to result in significantly higher AuNP growth yield as compared to LCs employing the other two materials. In all cases, an electrical bias of the entire LC structures significantly affected particle growth. We demonstrate an inverse correlation of the AuNP growth rate with secondary electron (SE) emission from the windows. We attribute these differences at least in part to variations in SE emission dynamics, which is seen as a combination of material and bias dependent SE escape flux (SEEF) and SE return flux (SERF). Furthermore, our model predictions qualitatively match electrochemistry expectations

Serial protein crystallography in an electron microscope

Serial X-ray crystallography at free-electron lasers allows to solve biomolecular structures from sub-micron-sized crystals. However, beam time at these facilities is scarce, and involved sample delivery techniques are required. On the other hand, rotation electron diffraction (MicroED) has shown great potential as an alternative means for protein nano-crystallography. Here, we present a method for serial electron diffraction of protein nanocrystals combining the benefits of both approaches. In a scanning transmission electron microscope, crystals randomly dispersed on a sample grid are automatically mapped, and a diffraction pattern at fixed orientation is recorded from each at a high acquisition rate. Dose fractionation ensures minimal radiation damage effects. We demonstrate the method by solving the structure of granulovirus occlusion bodies and lysozyme to resolutions of 1.55 Å and 1.80 Å, respectively. Our method promises to provide rapid structure determination for many classes of materials with minimal sample consumption, using readily available instrumentation

DIE EFFEKTIWITEIT VAN LANDBOUVOORLIGTING MET VERWYSING NA DIE KOMMERSI~LE LANDBOUSEKTOR IN SUID-AFRIKA

The effectiveness of information can be measured in terms of the extent to which it enables clients to adapt to c_hanging circumst?nccs. The degree of the development of such an adaptation depends on the value of the_ inf?~ation passed on ~o the clients. The provt~1on_of appropriate and relevant information is, besides the conccpt_ua_l framcwo~k on _which II 1s_dcvcloped, als~ mflucnced by the underlying mstitutional and operational frameworks. There arc two distinct paradigms m the agncultural extension sphe~c of the RSA e.g . . the technical-educational and economic, each with their own separate institutions. As a result of the total dominance of th~ tcchni~aleducational paradigm, the economic paradigm has not come into its own with the rc_sultant poor d~velopment of b?th formal information systems and the managerial resource in agriculture. The inc~fectivcncss of the agncultural extens1o_n framework in the RS~ in te_rms of the generation of information is further enhanced by the existence of separate departments of agncul_turc for each parad1~m! ~t~ the result that extension is not being presented in a holistic (systems based) manner. The proposed hohsllc and therefore mult1-d1sc1phnary approach to agricultural extension in the RSA should be viable within the to be instituted regional agricultural development centres under a single department of agriculture