Secondary electron emission from oxide-coated cathodes

The secondary electron emission from alkaline-earth oxide-coated cathodes has been investigated under both continuous and pulsed bombardment. Various factors affecting the yield, such as dependence upon primary voltage, collecting voltage, temperature, time, and angle of incidence, are noted, and the present state of the theory is discussed.Experiments have been performed with three types of apparatus. Yield vs. Energy data reveal values of δ of 4–7 at room temperature, with a more or less flat maximum at approximately 1,000 volts primary energy.The yield increases with temperature in an exponential manner, and plots of log Δδ (i.e. δ_K° ? δ_300°K) vs. 1/T give straight lines. Values of Q₁ between 0.9 – 1.5 eV. are generally indicated, and from extrapolation of these curves, yields exceeding 100 at 850° C. are deduced. The secondary emission depends upon the degree of activation, and increases with enhancement of the thermionic emission characteristics. Short-time effects such as growth or decay of secondary current after the onset of primary bombardment or persistence after the cessation of bombardment have not been observed, and values of yield obtained by pulsed methods are in accord with those obtained under D.C. conditions. Tail phenomena reported by J. B. Johnson and interpreted as “enhanced thermionic emission” from oxidecoated cathodes become manifest only under experimental conditions characterized by certain space-charge effects, and have been effectively simulated by bombarding a tantalum target adjacent to an electron-emitting tungsten filament. Various measurements of the energy distribution of secondary electrons as a function of primary voltage and temperature have been obtained. It was observed that the average energy of the secondary electrons decreases with temperature at a rate which more than compensates for the increase in the number of secondaries emitted per incident primary. The mechanism of the observed dependence of yield upon temperature is not well understood. Various alternative explanations are discussed and, in the light of the present state of our knowledge, regarded as untenable.     

Ethical issues of behavior modification research in schools

Behavior modification research in the classroom was examined by the National Commission for the Protection of Human Subjects because of the increasingly widespread use of behavioral procedures in the schools, the effectiveness of these procedures in changing academic and social behavior, and the consequent concern about potential misuse. In order to foster the responsible use of behavior modification procedures in the schools on a practical as well as a research basis, the following ethical issues being considered by researchers and the involved public are discussed: informed consent, determination of classroom goals, legitimacy of rewards and aversive controls in the classroom, conceptions of behavior modification as manipulative and mechanistic, who can implement the procedures, research design, and accountability. The authors conclude that the issues regarding protection of human subjects in behavior modification research are no different from other treatment-oriented research with children. However, the high degree of parental and teacher involvement in both research and practice requires shared responsibility for the prevention of misuse of behavior modification procedures.     

Effects of race and social class on preschool performance on the developmental test of visual-motor integration

The visual-motor integration of preschool children who varied in terms of race, sex, and socioeconomic status was assessed using the Beery-Buktenica Test of Visual-Motor Integration (VMI). An analysis of covariance revealed that there were significant main effects for race, sex, and socioeconomic status. Since, at the three- and four-year level, the VMI was normed only on white suburban children, the results of this study seemed to indicate the need for norms for black children at the preschool level. Thus, the second part of this paper reports normative data for black preschool children on the VMI.     

Arts education partnerships: sources of harmony and dissonance with cultural institutions’ collaborative efforts

ABSTRACT

Due to budget constraints, schools in the United States have increasingly turned to community arts organizations for support. School-community arts partnership stakeholders collaborate because of shared missions to provide students with valuable arts learning experiences. Investigations of these initiatives indicate that these partnerships improve arts learning opportunities and increase public support and resources for arts education. However, not much is known about the experiences and perspectives of the arts organizations that participate in these partnerships. Coordinating collective efforts with a multitude of institutions and interests poses challenges. In this study, we examine survey data collected from arts organization administrators who participated in a large-scale school-community arts partnership initiative. We find that these organizations are generally positive about their impacts on students’ educational outcomes, but there is substantial variation in these views. We also find that organizations differ in their levels of support for these collective efforts. Sources of this variation appear to be attributable to organizations’ preexisting resources and extent to which they are established. While this difference in levels of support is potentially inevitable, we find evidence that the operations handled by the “backbone” organization, i.e. the initiative’s facilitators and overseers, can significantly influence organizations’ levels of support for these efforts. Organizations are more likely to support these collaborative efforts when they believe the backbone organization ensures transparency with initiative operations, provides regular, effective communication, and effectively resolves competing priorities.     

Fantasy,Pragmatism and Journalistic Socialisation: UK Journalism Students’ Aspirations and Motivations

ABSTRACT

Despite the sustained growth in journalism as a choice of degree path for young people, our understanding of students’ aspirations and motivations remains relatively underdeveloped. At the same time, journalism careers appear increasingly uncertain, as the industry responds to digitalisation and convergence. In this mixed-methods study – employing 35 interviews and a survey of 837 UK journalism students – we ask what areas of journalism do students aspire towards, how do they feel about their future career prospects, and what is motivating them to study journalism in the first place? We find that intrinsic motivations (calling and talent, dynamic job) prevail over public service ones, with students drawn to soft news beats over hard news. Aspirations are also strikingly gendered, opening up questions of journalism education in this process. We also find that while students articulate an aspirational career in respected media outlets, they are pragmatic about their immediate career prospects. Here, journalism education appears to play a significant role in socialising students towards careers beyond journalism. Findings are discussed in the light of ongoing debates around journalistic socialisation and the future of journalism.     

Light-induced cracking and abrasion of inkjet prints: Damage and mitigation

This study is part of a larger research project at the Image Permanence Institute dedicated to digital print preservation issues – the Digital Print Preservation Portal (DP3). Previous DP3 studies determined that certain digital print types are prone to cracking and/or abrasion, and that factors such as low relative humidity, pollutants, and light increase the brittleness of the ink-receiving layer of some inkjet papers. The purpose of this investigation was to explore if light also increases the propensity of inkjet prints to abrade, and to examine the potential of framing glazings to mitigate light-induced physical damage (cracking and abrasion) by attenuating some portion of the UV spectrum. Inkjet papers and prints were subjected to xenon lighting (to simulate daylight through window glass) without glazing, or in sealed framing packages with plain framing glass (soda-lime) or UV filtering glass. Before and after light exposure, brittleness, and abrasion resistance were evaluated independently using two tests: ISO 18907 (Imaging materials – Photographic films and papers – Wedge test for brittleness) and a rub test utilizing a Sutherland® Rub Tester. In this study, exposure to light increased the cracking and/or abrasion tendency of some specimens. The use of UV filtering glass reduced this light-induced propensity in all cases. Plain glass protected all samples from at least one of these two types of surface damage, but was less effective than UV glass. Light-induced brittleness and sensitivity to abrasion were mostly, though not exclusively, caused by UV radiation. It was also seen that some prints may become brittle and/or prone to abrasion in the absence of image fade. Budgeting the amount of light these objects can be exposed to, protecting them from UV radiation, and handling prints with caution especially after exhibition, is essential in order to limit physical damage.