Average motion of emerging solar active region polarities: II. Joy's law.

CONTEXT: The tilt of solar active regions described by Joy's law is essential for converting a toroidal field to a poloidal field in Babcock-Leighton dynamo models. In thin flux tube models the Coriolis force causes what we observe as Joy's law, acting on east-west flows as they rise towards the surface. AIMS: Our goal is to measure the evolution of the average tilt angle of hundreds of active regions as they emerge, so that we can constrain the origins of Joy's law. METHODS: We measured the tilt angle of the primary bipoles in 153 emerging active regions (EARs) in the Solar Dynamics Observatory Helioseismic Emerging Active Region survey. We used line-of-sight magnetic field measurements averaged over 6 h to define the polarities and measure the tilt angle up to four days after emergence. RESULTS: We find that at the time of emergence the polarities are on average aligned east-west, and that neither the separation nor the tilt depends on latitude. We do find, however, that EARs at higher latitudes have a faster north-south separation speed than those closer to the equator at the emergence time. After emergence, the tilt angle increases and Joy's law is evident about two days later. The scatter in the tilt angle is independent of flux until about one day after emergence, when we find that higher-flux regions have a smaller scatter in tilt angle than lower-flux regions. CONCLUSIONS: Our finding that active regions emerge with an east-west alignment is consistent with earlier observations, but is still surprising since thin flux tube models predict that tilt angles of rising flux tubes are generated below the surface. Previously reported tilt angle relaxation of deeply anchored flux tubes can be largely explained by the change in east-west separation. We conclude that Joy's law is caused by an inherent north-south separation speed present when the flux first reaches the surface, and that the scatter in the tilt angle is consistent with buffeting of the polarities by supergranulation.

Penumbral structure and outflows in simulated sunspots.

Sunspots are concentrations of magnetic field on the visible solar surface that strongly affect the convective energy transport in their interior and surroundings. The filamentary outer regions (penumbrae) of sunspots show systematic radial outward flows along channels of nearly horizontal magnetic field. These flows were discovered 100 years ago and are present in all fully developed sunspots. By using a comprehensive numerical simulation of a sunspot pair, we show that penumbral structures with such outflows form when the average magnetic field inclination to the vertical exceeds about 45 degrees. The systematic outflows are a component of the convective flows that provide the upward energy transport and result from anisotropy introduced by the presence of the inclined magnetic field.

Cholinergic modulation of immunoglobulin secretion from avian plasma cells: the role of cyclic mononucleotides.

The chicken Harderian (lacrimal) gland contains an abundance of plasma cells in the interstitium of the gland that secrete IgG, IgM, and IgA. In in vitro preparations of this gland, the cholinergic agonist carbachol causes a transient increase in the secretion rate of IgG above a basal level of secretion. We have investigated the effects of the cyclic mononucleotides cAMP and cGMP on this secretagogue response. Pretreatment with 20 microM forskolin or 1 mM dibutyryl cAMP abolished the carbachol-induced secretory response. When the gland was isolated in normal media and then treated with either forskolin or dibutyryl cAMP, there was no change in the baseline secretion rate. cGMP at either 10 microM or 1.0 mM did not affect the baseline secretion rate, nor did it have an effect on the carbachol response. We postulate that muscarinic receptor activation leads to a calcium influx that in turn leads to an increased secretion rate of IgG. The opposing effects of elevating cAMP and cGMP are discussed in the context of this model of cholinergic activation of avian plasma cells.

Cholinergic modulation of immunoglobulin secretion from avian plasma cells: the role of calcium.

The existence of a functional connection between the nervous and immune systems has long been argued. To determine if such a link exists in the secretory immune system, we have examined the avian lacrimal gland (Harderian gland) which contains large numbers of plasma cells. We have shown that these plasma cells bind an antibody to muscarinic acetylcholine receptor and that carbachol, an acetylcholine agonist, increases the secretion rate of IgG by these cells above a constitutive baseline level. This neurotransmitter-dependent increase of immunoglobulin secretion requires an influx of Ca2+, whereas the constitutive baseline secretion is apparently less dependent on such a flux. Furthermore, the Ca2+ flux appears to be mediated by voltage-dependent calcium channels. These data support the hypothesis that plasma cells can respond to neurotransmitters and, in the case of acetylcholine, increase immunoglobulin secretion.

Fine needle aspiration and computed tomographic scanning in the evaluation of parotid lesions.

The usefulness and limitations of needle aspiration and CT scanning are illustrated in three case reports. In conjunction with the clinical evaluation, these modalities can provide useful information, although no definitive decision should be made on the basis of limited cytopathologic data. The ultimate treatment is better planned when the information provided by CT and needle aspiration are combined with the clinical impression. We advocate the use of fine needle aspiration in conjunction with CT scanning for selected parotid area masses. Readily palpated masses located almost certainly in the substance of the parotid may be appropriately managed without these two modalities. We believe that these tests can greatly help in the planning treatment of less definite lesions.

ESR measurement of dissolved oxygen in 4-day chick embryo blood.

The magnetic interactions between dissolved oxygen molecules and nitroxide radical spin probes lead to broadening of electron spin resonance (ESR) lines. Based on this property we described an ESR methodology to measure PO2 values in 4-day chick embryo and adult human blood. The total blood volume required for the measurement was only 9 microliter. Using this method PO2 for adult human mixed venous blood was found to be 36.7 mmHg. This is within the established clinical range of 25-40 mmHg for mixed venous blood PO2. The range of mean PO2 values for 4-day chick embryo blood was 27.3- 35.0 mmHg. This is the first time that PO2 values have been reported for individual chick embryos at such an early stage.

Elevated blood pressure in the embryonic chick induced by a teratogenic dose of dextroamphetamine sulfate.

Previous work has demonstrated the cardiovascular teratogenicity of dextroamphetamine sulfate (0.25 mg/egg) in the 4-day (stage 24) chick embryo. Our current studies indicate that embryos treated with this teratogenic dose of d-amphetamine exhibit a mean ventricular blood pressure (MVBP) elevation for 1 hour at 4 hours after treatment. The mean MVBP value 4 hours after d-amphetamine treatment significantly exceeded the mean MVBP value for combined untreated and saline controls by 30%. Furthermore, d-amphetamine significantly decreased heart rate relative to controls by 6-9% at 2, 3, and 5 hours after administration. Elevation of embryonic blood pressure (measured by a water manometer system) during a critical period of aortic arch and ventricular septal morphogenesis is suggested as an etiological factor in the genesis of malformations of these structures.

Pharmacology of dextroamphetamine-induced cardiovascular malformations in the chick embryo.

We have observed dextroamphetamine sulfate to cause cardiovascular malformations in the 4-day-old chick embryo. Essentially all malformations were of the heart and great vessels. About one-half of these were the abnormal persistence of the left fourth aortic arch. Ventricular septal defects comprised the vast majority of the other malformations. Since d-amphetamine has both a direct and, more importantly, an indirect mode of alpha and beta adrenergic stimulation, three drugs were used to try to inhibit malformation production: alpha-methyl-p-tyrosine (AMT), a catecholamine synthesis inhibitor; metoprolol, a beta 1 blocker; and phentolamine, an alpha blocker. When given with d-amphetamine, all three drugs significantly reduced the malformation rate resulting from d-amphetamine alone. We speculate that the embryonic chick is capable of responding to the alpha and/or beta properties of dextroamphetamine sulfate. These properties may be causally related to the malformations observed.