Magnification of starting torques of dc motors by maximum power point trackers in photovoltaic systems

Direct current (dc) motors are used in terrestrial photovoltaic (PV) systems such as in water-pumping systems for irrigation and water supply. Direct current motors may also be used for space applications. Simple and low weight systems including dc motors may be of special interest in space where the motors are directly coupled to the solar cell array (with no storage). The system will operate only during times when sufficient insolation is available. An important performance characteristic of electric motors is the starting to rated torque ratio. Different types of dc motors have different starting torque ratios. These ratios are dictated by the size of solar cell array, and the developed motor torque may not be sufficient to overcome the load starting torque. By including a maximum power point tracker (MPPT) in the PV system, the starting to rated torque ratio will increase, the amount of which depends on the motor type. The starting torque ratio is calculated for the permanent magnet, series and shunt excited dc motors when powered by solar cell arrays for two cases: with and without MPPT's. Defining a motor torque magnification by the ratio of the motor torque with an MPPT to the motor torque without an MPPT, a magnification of 3 was obtained for the permanent magnet motor and a magnification of 7 for both the series and shunt motors. The effect of the variation of solar insolation on the motor starting torque was covered. All motor types are less sensitive to insolation variation in systems including MPPT's as compared to systems with MPPT's. The analysis of this paper will assist the PV system designed to determine whether or not to include an MPPT in the system for a specific motor type

Starting characteristics of direct current motors powered by solar cells

Direct current motors are used in photovoltaic systems. Important characteristics of electric motors are the starting to rated current and torque ratios. These ratios are dictated by the size of the solar cell array and are different for the various dc motor types. Discussed here is the calculation of the starting to rated current ratio and starting to rated torque ratio of the permanent magnet, and series and shunt excited motors when powered by solar cells for two cases: with and without a maximum-power-point-tracker (MPPT) included in the system. Comparing these two cases, one gets a torque magnification of about 3 for the permanent magnet motor and about 7 for other motor types. The calculation of the torques may assist the PV system designer to determine whether or not to include an MPPT in the system

Proposal for a Topological Plasmon Spin Rectifier

We propose a device in which the spin-polarized AC plasmon mode in the surface state of a topological insulator nanostructure induces a static spin accumulation in a resonant, normal metal structure coupled to it. Using a finite-difference time-domain model, we simulate this spin-pump mechanism with drift, diffusion, relaxation, and precession in a magnetic field. This optically-driven system can serve as a DC "spin battery" for spintronic devices.Comment: Eq. 1 corrected; Figs 3 and 4 update

Calculation of the Self-energy of Open Quantum Systems

We propose an easy method of calculating the self-energy of semi-infinite leads attached to a mesoscopic system.Comment: 6 pages, 2 figures, published in J. Phys. Soc. Jp

Harnessing the power of fusion? A valiant but flawed effort to obviate the need for a distinct mental health law

When it comes to involuntary interventions, the notion that people with mental disorders should be treated identically to persons with general medical disorders has an undoubted appeal. As Dawson and Szmukler have argued previously, principles of fairness and non-discrimination would appear to be well served by basing involuntary hospitalization and treatment in both contexts on incapacity to provide consent. In this commentary, I take note of some of the intellectual forebears of the Szmukler, Daw, and Dawson proposal, and ask why – despite the formidable intellects that have lined up behind similar approaches in the past – they have not been adopted. I also consider some aspects of the current proposal itself, including the unresolved tensions between equal and differential treatment of persons with mental disorders, and the potential practical consequences, especially for persons with general medical disorders. I conclude that the rationale for fusing two disparate bodies of law may itself be irremediably flawed, and the undesirable consequences significant. 

Discrete arginine topologies guide escape of miniature proteins from early endosomes to the cytoplasm

Polypeptides and peptide mimetics sample a wide chemical space with broad potential to modulate cellular function, but their application to cytoplasmic targets is limited because when added to cells their cytosolic concentration remains low. This limitation is due to a diffusion barrier (the plasma membrane) and absence of dedicated import machinery. Highly cationic peptides and proteins sometimes gain cytosolic access, but how they do so is not well understood. Using a small library of cationic miniature proteins, I probe the influence of positive charge number and orientation on the ability the miniature protein to access the cytoplasm. Using a novel assay, I identify a cationic miniature protein, which we called 5·3, that carries a discrete arginine motif and efficiently reaches the cytoplasm. Database searches find that the precise motif identified (an arginine present in positions i, i + 4, i + 7, i + 10, and i + 11 of an alpha-helix) is not present in nature, but that similar motifs are present in natural proteins that interact with cellular membranes. Finally, I examine the cellular pathway by which 5·3 reaches the cytoplasm. I find that this miniature protein enters the cell via a dynamin and cholesterol dependent endocytic mechanism and is delivered to Rab5+ early endosomes. In contrast to the shiga-like toxins, and many non-enveloped viruses (which escape to the cytoplasm from the endoplasmic reticulum) as well as other peptides previously identified as \u27cell penetrating\u27, only 5·3 escapes from early endosomes. These findings should enable the future dissection of the precise molecular events underlying cytoplasmic access of peptides and proteins, and may illuminate principles for the engineering of peptides and peptidomimetics that access cytoplasmic targets

Balancing autonomy and beneficence at the time of psychiatric discharge

As in much of the world, mental health law in Israel has evolved over the past half-century toward greater protection of patients’ liberty and an increased emphasis on due process. Part of that process in Israel involved taking decisions about prolonged involuntary hospitalization out of the hands of treating psychiatrists and turning them over to independent review panels. Argo and colleagues examined outcomes of discharge decisions made by these panels compared with treating psychiatrists. In this brief commentary, we describe related trends in mental health law in other countries, especially the U.S., consider countervailing perspectives on the role of review panels, and suggest how the Argo et al. study might be followed up with additional research