Heavy electrons: Electron droplets generated by photogalvanic and pyroelectric effects

Electron clusters, X-rays and nanosecond radio-frequency pulses are produced by 100 mW continuous-wave laser illuminating ferroelectric crystal of LiNbO_3. A long-living stable electron droplet with the size of about 100 mcm has freely moved with the velocity 0.5 cm/s in the air near the surface of the crystal experiencing the Earth gravitational field. The microscopic model of cluster stability, which is based on submicroscopic mechanics developed in the real physical space, is suggested. The role of a restraining force plays the inerton field, a substructure of the particles' matter waves, which a solitary one can elastically withstand the Coulomb repulsion of electrons. It is shown that electrons in the droplet are heavy electrons whose mass at least 1 million of times exceeds the rest mass of free electron. Application for X-ray imaging and lithography is discussed.Comment: 15 p., 3 fig

Engineering novel complement activity into a pulmonary surfactant protein

Complement neutralizes invading pathogens, stimulates inflammatory and adaptive immune responses, and targets non- or altered-self structures for clearance. In the classical and lectin activation pathways, it is initiated when complexes composed of separate recognition and activation subcomponents bind to a pathogen surface. Despite its apparent complexity, recognition-mediated activation has evolved independently in three separate protein families, C1q, mannose-binding lectins (MBLs), and serum ficolins. Although unrelated, all have bouquet-like architectures and associate with complement-specific serine proteases: MBLs and ficolins with MBL-associated serine protease-2 (MASP-2) and C1q with C1r and C1s. To examine the structural requirements for complement activation, we have created a number of novel recombinant rat MBLs in which the position and orientation of the MASP-binding sites have been changed. We have also engineered MASP binding into a pulmonary surfactant protein (SP-A), which has the same domain structure and architecture as MBL but lacks any intrinsic complement activity. The data reveal that complement activity is remarkably tolerant to changes in the size and orientation of the collagenous stalks of MBL, implying considerable rotational and conformational flexibility in unbound MBL. Furthermore, novel complement activity is introduced concurrently with MASP binding in SP-A but is uncontrolled and occurs even in the absence of a carbohydrate target. Thus, the active rather than the zymogen state is default in lectin·MASP complexes and must be inhibited through additional regions in circulating MBLs until triggered by pathogen recognition

Investigation of the dynamic behavior of soybean plants during cutting

Shatter losses of soybeans are still a substantial percentage of potential profits despite extensive research of the problem. Previous efforts have tended to be concerned with the design and operating aspects of harvesting machinery rather than the dynamic characteristics of the plant. In contrast, this study focused on the dynamic behavior of soybean plants during cutting. Mathematical models were developed for the dynamics of the components of the soybean plant: the stalk and pod. The Euler-Bernoulli beam appeared to be a satisfactory model for the stalk, predicting modes of vibration with corresponding natural frequencies. The simple pendulum with a torsional spring was adequate for modeling some aspects of pod motion. The coupled stalk-single pod model showed the effect of the pod on the motion of the stalk to be due to: the added mass of the pod, the motion of the pod, and collisions between the pod and stalk. The model also predicted that the pod and stalk tended to move out of phase for vibration at most frequencies, and that the response of the pod to stalk vibration was frequency dependent, the most significant pod response occurring at lower frequencies. The notion of a cutting function was introduced to represent the aspects of cutting that cause motion of the plant. For the type of cutting device used in this study, a multi-tooth circular saw blade, a sequence of pulses appeared to be an adequate mathematical model cutting function. Experimental determination of cutting functions using stalks with pods attached was hindered by the nonlinearities caused by friction between pods and collisions between pods and the stalk. Data collection was accomplished with accelerometers and an analog-to-digital data acquisition system. The presence of the accelerometers and cables affected the response of the plant and the instrumentation would very likely be damaged by severe plant motion; therefore, another method of sensing plant response would be more appropriate. Digital signal analysis using Fast Fourier Transform methods proved to be an effective method of data analysis. The application of this technology to the study of crop dynamics appears as promising as it has been for other areas of vibration research

Stress-induced Phase Change Sintering: A Novel Approach to the Fabrication of Barium Chloride Transparent Ceramic Scintillators

For the precise in-field identification of dangerous radioisotopes, the desire for higher resolution, cheaper, and more rugged gamma-ray scintillator detectors has pushed the materials science community to investigate new compounds and processing techniques. One particular solution is Eu:BaCl2 transparent ceramics processed by the novel phase-change sintering technique. Typically, optical transparency in BaCl2 would be limited by birefringence scattering at grain boundaries due to mismatch in refractive index. Traditional ceramic processing routes would also predispose this volatile and hygroscopic material to the formation of defects, which interrupt the energy transfer in the scintillation process. Literature shows that these challenges have prevented halide gamma-ray scintillator ceramics, including Ce:LaBr3, Eu:SrI2, and Ce:Cs2LiYCl6, from reaching the performance of their single-crystalline counterparts. The sintering method explored in this thesis utilizes a polymorphic orthorhombic to cubic phase transition followed by plastic deformation. The experimental implementation of this method necessitated the design of a unique airtight hot-pressing device, capable of developing conditions for this phase conversion, and the synthesis of high purity powders. Systematic experiments on powder synthesis and on densification were carried out to demonstrate the feasibility of this approach and understand the conditions for phase-change sintering. These experiments, supported by characterizations including x-ray diffraction, electron microscopy, and thermal analysis, lead to the production of optically isotropic cubic barium chloride ceramic samples. Finally, the optical and scintillation properties of Eu:BaCl2 ceramic samples were investigated, revealing an energy resolution of 6% at 662 keV, an unprecedented value for a halide ceramic scintillator

Postcard from H. C. Shoulders to B. R. Colson

Postcard from H. C. Shoulders to B. R. Colson. The handwritten note is dated 23 February 1910. There is a transcript of the correspondence in the item PDF

Host proteostasis modulates influenza evolution

Predicting and constraining RNA virus evolution require understanding the molecular factors that define the mutational landscape accessible to these pathogens. RNA viruses typically have high mutation rates, resulting in frequent production of protein variants with compromised biophysical properties. Their evolution is necessarily constrained by the consequent challenge to protein folding and function. We hypothesized that host proteostasis mechanisms may be significant determinants of the fitness of viral protein variants, serving as a critical force shaping viral evolution. Here, we test that hypothesis by propagating influenza in host cells displaying chemically-controlled, divergent proteostasis environments. We find that both the nature of selection on the influenza genome and the accessibility of specific mutational trajectories are significantly impacted by host proteostasis. These findings provide new insights into features of host-pathogen interactions that shape viral evolution, and into the potential design of host proteostasis-targeted antiviral therapeutics that are refractory to resistance.National Institutes of Health (U.S.) (Award 1DP2GM119162)National Institutes of Health (U.S.) (Grant P30-ES002109

Letter from H. C. Shoulders to B. R. Colson

Letter from H. C. Shoulders to B. R. Colson. The three-page handwritten note is dated 19 February 1910. There is a transcript of the correspondence in the item PDF