Solutions of the micromagnetic equations for the equilibrium distribution of magnetization may have singular points, at which no spontaneous magnetization exists, because the limit of the magnetization vector for an approach to this point on different rays has different values. The boundary conditions at these points are considered. The exchange-energy density goes to infinity at such a point, but the condition that its integral should be a minimum leads to no definite boundary condition. For a special class of such singularities, namely those at which every direction of the magnetization is accepted once on a small sphere around it, the conditions for a minimum of the field energy are derived.
W . D6ring. Abhungigkeit des FVidersta?zdes voi.2 Nickelkristallen usw. 259 Xach unseren heutigen Voistellungen ist ein ferroninguetisches B1;tteri;tl bei Temperaturen unterliait des Ckiepunktes stets in eiiizelnen 3ezirlieii s1mnta.n his z u r Syittiguug magnetisieif. Iin p u s c h a l uiiniaguetischeni Ziistaud ist nur die Riclitung der 11%giietisierung ron Rezirk zu Bezirk verschiecleii. Dtas Magnetfelt1 clrsht beini Magnetisieren lediglich clie Tektoren der spontaiteii Magnetisierang iu die Feldrichtung, ohiie Anderung ihres Eetrages. D:t sicli bei deiii ferroinagiietischen Mngiietisierungsrorgti.ng der elektrische IYiderstazld iiiidert, niulS also der M.idei,stand yon cler Richtuug der spout;anen Alagnetisieiulig relntiv zu den Iiiistallachsen und zuni Stroiri nl~h~tngen. Das Ziel aller Uiitersucliuiigen iiber diesen EB'ekt ist es demnach in e r s t~r Iinie, das Gesetz dieser Ahliiingigkeit x u bestimmen, intleui iiian die Widei~standsunterschiede hei Siit,tiguug in ve1,schiedenen IZic,htungen niiBt. Erst in m e i t e r Linie interessiert auch der T'erlauf' des Widerstmdes als b'nnlition des Feldes oder der l~auscclialen Jlagnetisierung. M.euii nilnilich die Abliiiugigkeit des Widerstnndes vou der Rklitung cles 6trouies und tler Magiietisiorung helmint ist: ist der Verlnuf niit tleni Feld berechenbar, sobald die Biclituugsce~teiluiig der Vektoren der spantanen Magnetisieruiig gegeben ist. Das ist also ein Problem wie das der 13ereclinung der illagnet~isierun~sliurven. Der Tergleich zwischeu Kechnung uiid Esperiment lrann als Kontrolle unserer Vorstellungen iilser cleii RIagnetisieruugs~organg lterangezojien werclen.
Chronic alcohol abuse causes severe and persistent alterations in the hormonal regulatory systems of electrolyte and water balance. The suppressed basal secretion of AVP may reflect a dysregulation in the brain that influences the hypothalamic-pituitary-adrenal axis function, mood, memory, addiction behavior, and craving during alcohol abstinence. These findings may provide a ground for future therapeutic approaches to stable abstinence.
Despite their persistently decreased basal AVP plasma levels, long-term abstinent alcoholics have a well preserved AVP response to osmostimulation. This finding indicates a peripheral suppression of AVP levels that is most likely due to a regulatory set-point shift toward hypotonic hyperhydration, rather than to a reduced central capacity of AVP secretion.
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