Optimization of a low-energy, high brightness electron gun for inverse photoemission spectrometers

Availability of a low-energy, high current electron gun delivering a well-focused spot on the sample is essential for the inverse photoelectron spectroscopy. We have optimized an electron gun to obtain the maximum beam current at all electron kinetic energies of relevance with a reasonably small focus spot. Here we present the design, the procedure for the optimization, as well as the resulting characteristics of the electron gun

Stress versus temperature dependent activation energies in creep

The activation energy for creep at low stresses and elevated temperatures is lattice diffusion, where the rate controlling mechanism for deformation is dislocation climb. At higher stresses and intermediate temperatures, the rate controlling mechanism changes from that of dislocation climb to one of obstacle-controlled dislocation glide. Along with this change, there occurs a change in the activation energy. It is shown that a temperature-dependent Gibbs free energy does a good job of correlating steady-state creep data, while a stress-dependent Gibbs free energy does a less desirable job of correlating the same data. Applications are made to copper and a LiF-22 mol. percent CaF2 hypereutectic salt

Hospitality Education and Industry Linkages: A Systematic Literature Network Analysis

The purpose of the study was to identify key themes, research gaps, and influential authors, as well as to examine the evolution of research and the quality and rigor of existing literature on hospitality education and its industry linkage. For this, a systematic literature network analysis, comprising a systematic literature review using the PRISMA framework, bibliometric analysis using R programming, network analysis, and thematic analysis was performed. The findings revealed that the most important clusters of research in this area are related to curriculum development, work-integrated learning, and industry partnerships. The review explored the importance of industry-academic collaboration, challenges, curriculum development, and employability as four main themes in the area of industrial linkage in hospitality education. As indicated by researchers, the review suggests the effectiveness of different approaches to industry-academia collaboration in hospitality education, the impact of industrial linkage on the quality of hospitality education in several regions, the role of technologies in enhancing the collaboration between academia and industry in hospitality education, and the development of a sustainable curriculum that incorporates environmental, social, and economic sustainability in hospitality education as future research areas

EFFECT OF VARIOUS IRRIGANTS ON DENTAL BIOFILM: A REVIEW

ABSTRACTObjective: The objective of the article is to describe in brief the various endodontic irrigants on dental biofilm.Method: Articles based on various endodontic irrigants and dental biofilm were searched in an iterative manner from journals,books and sites suchas PubMed.Result: It was found out that sodium hypochlorite is more effective on dental biofilms than chlorhexidine, MTAD, EDTA, herbal irrigants and newirrigants such as Qmix and tetraclean.Conclusion: Disinfection of root canal system is done using mechanical instrumentation,chemical irrigation along with medication.Sodiumhypochlorite an excellent antibacterial agent,is the most commonly used and is more effective than other irrigants on dental biofilm.Keywords: Irrigants, Dental biofilm, Antimicrobial resistance, Sodium hypochlorite, Chlorhexidine, Tetraclean, Herbal irrigants

Effects of certain growth substances and boric acid on germination, tube growth and storage of grape pollen (Vitis ssp.)

Investigations on the ,effects of growth substances (GA, IAA and IBA) and boric acid on grape pollen have shown that maximum germination and tube growth was obtained rwith boric acid at lower concentrations (5, 10 and 20 ppm) as compared to GA, IAA, IBA and control. Although GA showed lesser pollen germination, pollen tube growth was enhanced at 5, 10 and 20 ppm in the grape cultivars under study. Pollen grains of Pusa Seedless were stored for 12 months and Pearl of Csaba for four months at different combinations of temperature and ihumidity. The pollen viability was highest when sfored at -12° to -10° C with 25 per cent R.H. which was followed by 4° to 8° C ,and 25 per cent R.H. The pollen germination increased throughout the storage period by boric acid at 5, 10 and 20 ppm

Low Temperature Creep of Hot-Extruded Near-Stoichiometric NiTi Shape Memory Alloy

This two-part paper is the first published report on the long term, low temperature creep of hot-extruded near-stoichiometric NiTi. Constant load tensile creep tests were conducted on hot-extruded near-stoichiometric NiTi at 300, 373 and 473 K under initial applied stresses varying between 200 and 350 MPa as long as 15 months. These temperatures corresponded to the martensitic, two-phase and austenitic phase regions, respectively. Normal primary creep lasting several months was observed under all conditions indicating dislocation activity. Although steady-state creep was not observed under these conditions, the estimated creep rates varied between 10(exp -10) and 10(exp -9)/s. The creep behavior of the two phases showed significant differences. The martensitic phase exhibited a large strain on loading followed by a primary creep region accumulating a small amount of strain over a period of several months. The loading strain was attributed to the detwinning of the martensitic phase whereas the subsequent strain accumulation was attributed to dislocation glide-controlled creep. An "incubation period" was observed before the occurrence of detwinning. In contrast, the austenitic phase exhibited a relatively smaller loading strain followed by a primary creep region, where the creep strain continued to increase over several months. It is concluded that the creep of the austenitic phase occurs by a dislocation glide-controlled creep mechanism as well as by the nucleation and growth of deformation twins

Low Temperature Creep of Hot-Extruded Near-Stoichiometric NiTi Shape Memory Alloy

This paper is the first report on the effect prior low temperature creep on the thermal cycling behavior of NiTi. The isothermal low temperature creep behavior of near-stoichiometric NiTi between 300 and 473 K was discussed in Part I. The effect of temperature cycling on its creep behavior is reported in the present paper (Part II). Temperature cycling tests were conducted between either 300 or 373 K and 473 K under a constant applied stress of either 250 or 350 MPa with hold times lasting at each temperature varying between 300 and 700 h. Each specimen was pre-crept either at 300 or at 473 K for several months under an identical applied stress as that used in the subsequent thermal cycling tests. Irrespective of the initial pre-crept microstructures, the specimens exhibited a considerable increase in strain with each thermal cycle so that the total strain continued to build-up to 15 to 20 percent after only 5 cycles. Creep strains were immeasurably small during the hold periods. It is demonstrated that the strains in the austenite and martensite are linearly correlated. Interestingly, the differential irrecoverable strain, in the material measured in either phase decreases with increasing number of cycles, similar to the well-known Manson-Coffin relation in low cycle fatigue. Both phases are shown to undergo strain hardening due to the development of residual stresses. Plots of true creep rate against absolute temperature showed distinct peaks and valleys during the cool-down and heat-up portions of the thermal cycles, respectively. Transformation temperatures determined from the creep data revealed that the austenitic start and finish temperatures were more sensitive to the pre-crept martensitic phase than to the pre-crept austenitic phase. The results are discussed in terms of a phenomenological model, where it is suggested that thermal cycling between the austenitic and martensitic phase temperatures or vice versa results in the deformation of the austenite and a corresponding development of a back stress due to a significant increase in the dislocation density during thermal cycling