The Role of fast magnetosonic waves in the release and conversion via reconnection of energy stored by a current sheet

Using a simple two-dimensional, zero-beta model, we explore the manner by which reconnection at a current sheet releases and dissipates free magnetic energy. We find that only a small fraction (3%-11% depending on current sheet size) of the energy is stored close enough to the current sheet to be dissipated abruptly by the reconnection process. The remaining energy, stored in the larger-scale field, is converted to kinetic energy in a fast magnetosonic disturbance propagating away from the reconnection site, carrying the initial current and generating reconnection-associated flows (inflow and outflow). Some of this reflects from the lower boundary (the photosphere) and refracts back to the X-point reconnection site. Most of this inward wave energy is reflected back again, and continues to bounce between X-point and photosphere until it is gradually dissipated, over many transits. This phase of the energy dissipation process is thus global and lasts far longer than the initial purely local phase. In the process a significant fraction of the energy (25%-60%) remains as undissipated fast magnetosonic waves propagating away from the reconnection site, primarily upward. This flare-generated wave is initiated by unbalanced Lorentz forces in the reconnection-disrupted current sheet, rather than by dissipation-generated pressure, as some previous models have assumed. Depending on the orientation of the initial current sheet the wave front is either a rarefaction, with backward directed flow, or a compression, with forward directed flow

Environmental Law: Streamlining the Review of Proposed Development Under the Environmental Land and Water Management Act

Examining recent legislative and judicial changes in the law governing proposed developments, the authors find that a predominant trend has been the streamlining of the procedures by which proposed developments are reviewed. Although administrative efficiency and speedy review pose the risk of unchecked development, the authors suggest that the recent changes in the law have adequately accommodated the competing goals of environmental protection and economic growt

Modulation of Asymmetric Division Diversity through Cytokinin and SPEECHLESS Regulatory Interactions in the Arabidopsis Stomatal Lineage

Coordinated growth of organs requires communication among cells within and between tissues. In plants, leaf growth is largely dictated by the epidermis; here, asymmetric and self-renewing divisions of the stomatal lineage create two essential cell types—pavement cells and guard cells—in proportions reflecting inputs from local, systemic, and environmental cues. The transcription factor SPEECHLESS (SPCH) is the prime regulator of divisions, but whether and how it is influenced by external cues to provide flexible development is enigmatic. Here, we show that the phytohormone cytokinin (CK) can act as an endogenous signal to affect the extent and types of stomatal lineage divisions and forms a regulatory circuit with SPCH. Local domains of low CK signaling are created by SPCH-dependent cell-type-specific activity of two repressive type-A ARABIDOPSIS RESPONSE REGULATORs (ARRs), ARR16 and ARR17, and two secreted peptides, CLE9 and CLE10, which, together with SPCH, can customize epidermal cell-type composition

Ovarian function in pony mares undergoing porcine zona pellucida immunocontraception

An advantage of the porcine zona pellucida (pZP) vaccine over other immunocontraceptives is the preservation of reproductive cyclicity and associated behaviors. Few studies have investigated ovarian function following pZP vaccination in the mare despite reported ovarian dysfunction in other species. The objectives of this study were to investigate ovarian function and estrous cyclicity in pony mares during immunocontraception with the conventional pZP vaccine. Fourteen mares were randomized into two groups of seven. Group I received 100 µg of pZP with Freund’s complete modified adjuvant (FCMA; V1), followed after five weeks by booster vaccination with 100 µg of pZP with Freund’s incomplete adjuvant (FIA; V2). Group II (controls) received two treatments five weeks apart of saline with FCMA (V1) and saline with FIA (V2) respectively. Treatments were administered via intramuscular injection into the gluteal muscles. Data were collected by an investigator blinded to treatment group over a period of 24 weeks during the physiological breeding season. All mares underwent estrus monitoring via trans-rectal palpation and ultrasound examination of the internal reproductive tract, on D0 (day of ovulation), D7, and D14 of consecutive estrous cycles, with daily monitoring between D14 and D0 of the following cycle. Artificial insemination was performed using fresh semen for up to two consecutive estrous cycles, commencing five weeks post-V2. Serum samples were collected weekly for the analysis of antibody titres and ovarian steroid (progesterone and estradiol) levels. Data were compared using Mann-Whitney U tests using commercially available software (IBM SPSS Statistics Version 22, International Business Machines Corp., Armonk, NY). Statistical significance was set as P < 0.05. All Group II mares showed normal estrous cyclicity throughout the study. Four Group I mares showed signs of anestrus within seven weeks of V2, characterised by small, inactive ovaries and baseline progesterone and estradiol levels. One Group I mare entered anestrus within 11 weeks of V2 and a second showed estrus with ovulation between variable periods of anestrus. Ovarian volumes, follicle counts and maximal follicle diameters in Group I were significantly lower than Group II. Per-cycle pregnancy proportions in Groups I and II were 0% and 78% respectively. This study demonstrated suppression of ovarian function in six of seven (86%) mares following pZP immunocontraception. Further research into the mechanism of action of zona pellucida-based vaccines is warranted

Plant Stem Cell Signaling Involves Ligand-Dependent Trafficking of the CLAVATA1 Receptor Kinase

Background: Cell numbers in above-ground meristems of plants are thought to be maintained by a feedback loop driven by perception of the glycopeptide ligand CLAVATA3 (CLV3) by the CLAVATA1 (CLV1) receptor kinase and the CLV2/CORYNE (CRN) receptor-like complex [1]. CLV3 produced in the stem cells at the meristem apex limits the expression level of the stem cell-promoting homeodomain protein WUSCHEL (WUS) in the cells beneath, where CLV1 and WUS RNA are localized. WUS downregulation nonautonomously reduces stem cell proliferation. Overexpression of CLV3 eliminates the stem cells, causing meristem termination [2], and loss of CLV3 function allows meristem overproliferation [3]. There are many questions regarding the CLV3/CLV1 interaction, including where in the meristem it occurs, how it is regulated, and how it is that a large range of CLV3 concentrations gives no meristem size phenotype [4]. Results: Here we use genetics and live imaging to examine the cell biology of CLV1 in Arabidopsis meristematic tissue. We demonstrate that plasma membrane-localized CLV1 is reduced in concentration by CLV3, which causes trafficking of CLV1 to lytic vacuoles. We find that changes in CLV2 activity have no detectable effects on CLV1 levels. We also find that CLV3 appears to diffuse broadly in meristems, contrary to a recent sequestration model [5]. Conclusions: This study provides a new model for CLV1 function in plant stem cell maintenance and suggests that downregulation of plasma membrane-localized CLV1 by its CLV3 ligand can account for the buffering of CLV3 signaling in the maintenance of stem cell pools in plants