The Land Question in Zimbabwe

A ZJE article discussing the re-distribution of land in Zimbabwe (Rhodesia) prior to the attainment of majority rule.The question of the redistribution of land in Zimbabwe has been receiving increasing attention during the last few years, but many of the suggestions made in this connection do not provide a satisfactory solution to a state of affairs which all but a few agree exists - namely, that the tribal area is overpopulated. The reason is that the problem is defined and referred to as a land-use or land distribution problem, and that discussion of the relative merits of rural development models is obscuring the fundamental issue. In reality the question is a population distribution problem

Multidimensional scaling reveals a color dimension unique to 'color-deficient' observers

Normal color vision depends on the relative rates at which photons are absorbed in three types of retinal cone:short-wave (S), middle-wave (M) and long-wave (L) cones, maximally sensitive near 430, 530 and 560nm, respectively. But 6% of men exhibit an X-linked variant form of color vision called deuteranomaly [1]. Their color vision is thought to depend on S cones and two forms of long-wave cone (L, L′) [2,3]. The two types of L cone contain photopigments that are maximally sensitive near 560nm, but their spectral sensitivities are different enough that the ratio of their activations gives a useful chromatic signal

Thermal Evaluation of High Voltage Hermetic Motors Experiencing Recurrent Insulation Failures

A high voltage hermetic compressor motor design developed for chiller applications has shown recurrent insulation failures in certain stator end-turn regions. Initial investigations found discoloration of failed coil insulation and suggested that the stator coils over heated during operation at rated load. Thermal modeling was conducted to develop an understanding of the causes of the unacceptably high motor failure rate so that corrective actions could be taken for future motor designs. This paper presents thermal modeling efforts for predicting steady-state temperature distributions within the stator coil in the end-turn region under full-load electrical heating and a refrigerant cooling environment. Insulation thermal conductivity and coil surface convection heat transfer coefficient were identified as two critical heat transfer parameters which dictate the effectiveness of coil heat dissipation. Thermal analysis results have been correlated with measured temperature dependent insulation thermal conductivities and stator coil surface temperatures measured in motor cooling tests. The results of thermal evaluation indicate that the premature motor failures are likely caused by excessive conductor heating due to high operating current density in a non-uniform coolant distribution.Center for Electromechanic

Fine-structure constant variability, equivalence principle and cosmology

It has been widely believed that variability of the fine-structure constant alpha would imply detectable violations of the weak equivalence principle. This belief is not justified in general. It is put to rest here in the context of the general framework for alpha variability [J. D. Bekenstein, Phys. Rev. D 25, 1527 (1982)] in which the exponent of a scalar field plays the role of the permittivity and inverse permeability of the vacuum. The coupling of particles to the scalar field is necessarily such that the anomalous force acting on a charged particle by virtue of its mass's dependence on the scalar field is cancelled by terms modifying the usual Coulomb force. As a consequence a particle's acceleration in external fields depends only on its charge to mass ratio, in accordance with the principle. And the center of mass acceleration of a composite object can be proved to be independent of the object's internal constitution, as the weak equivalence principle requires. Likewise the widely employed assumption that the Coulomb energy of matter is the principal source of the scalar field proves wrong; Coulomb energy effectively cancels out in the continuum description of the scalar field's dynamics. This cancellation resolves a cosmological conundrum: with Coulomb energy as source of the scalar field, the framework would predict a decrease of alpha with cosmological expansion, whereas an increase is claimed to be observed. Because of the said cancellation, magnetic energy of cosmological baryonic matter is the main source of the scalar field. Consequently the expansion is accompanied by an increase in alpha; for reasonable values of the framework's sole parameter, this occurs at a rate consistent with the observers' claims.Comment: RevTeX-4, 22 pages, no figures, added a section on caveats as well as several new references with discussion of them in body. To appear in Phys. Rev.

Cell division in apicomplexan parasites is organized by a homolog of the striated rootlet fiber of algal flagella

Apicomplexa are intracellular parasites that cause important human diseases including malaria and toxoplasmosis. During host cell infection new parasites are formed through a budding process that parcels out nuclei and organelles into multiple daughters. Budding is remarkably flexible in output and can produce two to thousands of progeny cells. How genomes and daughters are counted and coordinated is unknown. Apicomplexa evolved from single celled flagellated algae, but with the exception of the gametes, lack flagella. Here we demonstrate that a structure that in the algal ancestor served as the rootlet of the flagellar basal bodies is required for parasite cell division. Parasite striated fiber assemblins (SFA) polymerize into a dynamic fiber that emerges from the centrosomes immediately after their duplication. The fiber grows in a polarized fashion and daughter cells form at its distal tip. As the daughter cell is further elaborated it remains physically tethered at its apical end, the conoid and polar ring. Genetic experiments in Toxoplasma gondii demonstrate two essential components of the fiber, TgSFA2 and 3. In the absence of either of these proteins cytokinesis is blocked at its earliest point, the initiation of the daughter microtubule organizing center (MTOC). Mitosis remains unimpeded and mutant cells accumulate numerous nuclei but fail to form daughter cells. The SFA fiber provides a robust spatial and temporal organizer of parasite cell division, a process that appears hard-wired to the centrosome by multiple tethers. Our findings have broader evolutionary implications. We propose that Apicomplexa abandoned flagella for most stages yet retained the organizing principle of the flagellar MTOC. Instead of ensuring appropriate numbers of flagella, the system now positions the apical invasion complexes. This suggests that elements of the invasion apparatus may be derived from flagella or flagellum associated structures

High speed induction motor and inverter drive for flywheel energy storage

The use of flywheels to store energy is a technology which is centuries old. The confluence of several modern technologies has resulted in flywheels becoming a viable solution for the needs of the transportation, electric utility, and aerospace industries. This paper discusses a high-speed induction motor and its associated inverter drive which were developed for the Federal Railroad Administration’s “Advanced Locomotive Propulsion System.” The design of the induction motor provided several significant challenges. A megawatt rated, 12,000 rpm motor operating at a rotor surface velocity speed of 230 m/s required a unique mechanical configuration to withstand the centrifugal forces as well as an electromagnetic design, which produced a high efficiency at 200 Hz. Extending the design practices used in smaller motors would not achieve the goals required for a megawatt size machine. Similarly, the inverter was developed using a soft switching technique in order to meet the demands of high power output in a compact package. Application requirements, electrical and mechanical features of the motor, design strategy for the inverter, and test results are all presented in this paper.Center for Electromechanic

TransverseDiff gravity is to scalar-tensor as unimodular gravity is to General Relativity

Transverse Diffeomorphism (TDiff) theories are well-motivated theories of gravity from the quantum perspective, which are based upon a gauge symmetry principle. The main contribution of this work is to firmly establish a correspondence between TransverseDiff and the better-known scalar-tensor gravity --- in its more general form ---, a relation which is completely analogous to that between unimodular gravity and General Relativity. We then comment on observational aspects of TDiff. In connection with this proof, we derive a very general rule that determines under what conditions the procedure of fixing a gauge symmetry can be equivalently applied before the variational principle leading to the equations of motion, as opposed to the standard procedure, which takes place afterwards; this rule applies to gauge-fixing terms without derivatives.Comment: 10 pages; amsart style; v3: version as appeared in JCAP, redaction improve

2d Stringy Black Holes and Varying Constants

Motivated by the recent interest on models with varying constants and whether black hole physics can constrain such theories, two-dimensional charged stringy black holes are considered. We exploit the role of two-dimensional stringy black holes as toy models for exploring paradoxes which may lead to constrains on a theory. A two-dimensional charged stringy black hole is investigated in two different settings. Firstly, the two-dimensional black hole is treated as an isolated object and secondly, it is contained in a thermal environment. In both cases, it is shown that the temperature and the entropy of the two-dimensional charged stringy black hole are decreased when its electric charge is increased in time. By piecing together our results and previous ones, we conclude that in the context of black hole thermodynamics one cannot derive any model independent constraints for the varying constants. Therefore, it seems that there aren't any varying constant theories that are out of favor with black hole thermodynamics.Comment: 12 pages, LaTeX, to appear in JHE

Restorative Justice Approaches To The Informal Resolution Of Student Sexual Misconduct

This article reviews controversies about campus Title IX adjudication and the recent implementation of restorative justice (or RJ) responses to campus sexual harm. The RJ approach focuses on who has been harmed, what their needs are, and how the person who harmed them can meet those needs. Instead of engaging in adjudication, RJ aims to get an individual who caused harm to understand the impact of and take responsibility for their actions. Part I defines the RJ approach, describes various practices, and details the preparation necessary for a structured informal resolution process. Part II explains why RJ approaches have been limited to date for Title IX cases and outlines evolving guidance in this realm. Part III reviews legal considerations, including compliance requirements from the Department of Education’s 2020 Final Rule and the implications of the approach for concurrent or subsequent civil or criminal proceedings. Part IV offers three case studies of implementation. Part V summarizes evidence of effectiveness and Part VI concludes. By tracing these essential elements, this article moves beyond the philosophical underpinnings of RJ to offer tools and procedures to consider when adopting RJ for student-on-student sexual misconduct

Nucleotide Frequencies in Human Genome and Fibonacci Numbers

This work presents a mathematical model that establishes an interesting connection between nucleotide frequencies in human single-stranded DNA and the famous Fibonacci's numbers. The model relies on two assumptions. First, Chargaff's second parity rule should be valid, and, second, the nucleotide frequencies should approach limit values when the number of bases is sufficiently large. Under these two hypotheses, it is possible to predict the human nucleotide frequencies with accuracy. It is noteworthy, that the predicted values are solutions of an optimization problem, which is commonplace in many nature's phenomena.Comment: 12 pages, 2 figure