Age determination of sediment cores off western Spitsbergen

The Late Weichselian glacial history of the continental shelf off western Spitsbergen is discussed, based on acoustic sub-bottom records and sediment cores. The outer part of Isfjorden and the inner shelf to the west of this fjord are characterized by a thin veneer (10-20 m) of glacigenic sediments and absence of ice-marginal features. Towards the outer shelf the sediment thickness increases significantly, and exceeds 500 m at the shelf edge. Possible moraine complexes were identified in this outer part. Sediment cores from the inner shelf sampled a firm diamicton, interpreted as till, beneath soft glaciomarine sediments. Radiocarbon dates on shells from the clay resting directly on the till, suggest an age of around 12,500 yrs B.P. for the base of the marine sequence. We argue that grounded ice covered the sites shortly before. In contrast to suggestions that the fjords and coast were partly ice free during the Late Weischselian, we conclude that the ice must have reached out onto the continental shelf.

Age determination of sediments off western Svalbard

Late Quaternary sediment yields from the Isfjorden drainage area (7327 km**2), a high arctic region on Svalbard characterized by an alpine landscape, have been reconstructed by using seismic stratigraphy supported by sediment core analysis. The sediments that accumulated in the fjord during and since deglaciation can be divided into three stratigraphic units. The volumes of these units were determined and converted into sediment yield rates averaged over the drainage basin. During deglaciation, 13 to 10 ka, the sediment yield was ~860 tons(t)/km**2/yr. In the early Holocene it decreased to 190 t/km**2/yr, and then increased to 390t/km**2/yr during the late Holocene Little Ice Age. When normalized to the approximate glacierized area, these rates correspond to a sediment yield of ~800 t/km**2/yr . Sediment yield from non-glacierized parts of the drainage is estimated to be 35 t/km**2/yr. At times when ice advanced to the shelf edge, sediment was scoured from the fjord and deposited on the outer shelf and in a well-defined deep sea fan. Between 200 ka and 13 ka, 328 km**3 of sediment accumulated here, corresponding to a mean sediment yield rate of 335 t/km**2/yr. This is broadly consistent with calculations based on the above rates of sediment yield in glacierized and non-glacierized areas, and on estimates, based on glacial geology, of the temporal variation in degree of glacierization over the past 200 kyr. These figures indicate that much of the glacigenic sediment on the shelf and slope was eroded from the uplands of Svalbard by small glaciers during interstadials and interglacials. The sediments were temporarily stored in the fjord prior to redeposition on the shelf and slope during ice sheet advance. Taken into consideration, such redisposition of pre-eroded material will reduce estimates of primary ice sheet erosion rate.

Hydrogen bonding in the water stabilized structure of the modified unsymmetrically substituted viologen chromophore, N-ethyl-N'-(2-phosphonomethyl)-4,4'-bipyridylium dichloride

The crystal structure of the modified unsymmetrically N, N'-substituted viologen chromophore, N-ethyl- N'-(2-phosphonoethyl)-4, 4'-bipyridinium dichloride 0.75 hydrate. (1) has been determined. Crystals are triclinic, space group P-1 with Z = 2 in a cell with a = 7.2550(1), b = 13.2038(5), c = 18.5752(7) Å, α = 86.495(3), β = 83.527(2), γ = 88.921(2)o. The two independent but pseudo-symmetrically related cations in the asymmetric unit form one-dimensional hydrogen-bonded chains through short homomeric phosphonic acid O-H...O links [2.455(4), 2.464(4)A] while two of the chloride anions are similarly strongly linked to phosphonic acid groups [O-H…Cl, 2.889(4), 2.896(4)Å]. The other two chloride anions together with the two water molecules of solvation (one with partial occupancy) form unusual cyclic hydrogen-bonded bis(Cl...water) dianion units which lie between the layers of bipyridylium rings of the cation chain structures with which they are weakly associated.

硝酸镧与冠醚(2,2)配合物的晶体及电子结构研究

用X-射线单晶衍射法测定了硝酸镧与冠醚(2,2)配合物的晶体结构,发现其具有与报道的Eu(NO_3)_3(2,2)配合物不同的配位方式.晶体属于三斜晶系,空间群P(?),晶胞参数为a=10.312(2)(?);b=12.745(3)(?);c=8.917(2)(?);α=103.79(2)°;β=112.73(2)°;γ=83.68(2)°;V=1049.5(5)(?)~3;F(000)=587.88;Z=2.结构用重原子法解出;R值为0.0292.用INDO法计算了配合物的净电荷分布,电子结构、键级.结果表明,镧与配位原子间的键具有一定程度的共价性.镧的5d轨道对共价性的贡献最大,而4f轨道基本上不参与成键.La-N比La-O(醚)间存在较强的作用,增大了配合物的稳定性.

Dense spectrum of resonances and spin-1/2 particle capture in a near-black-hole metric

We show that a spin-1/2 particle in the gravitational field of a massive body of radius R which slightly exceeds the Schwarzschild radius rs, possesses a dense spectrum of narrow resonances. Their lifetimes and density tend to infinity in the limit R → rs. We determine the cross section of the particle capture into these resonances and show that it is equal to the spin-1/2 absorption cross section for a Schwarzschild black hole. Thus black-hole properties may emerge in a non-singular static metric prior to the formation of a black hole.

Huerta escolar 88-89 : proyecto huerta escolar.

La Asociación para la Investigación y el Estudio de la Deficiencia Mental, CEPRI, crea en el centro un huerto escolar como recurso didáctico y alternativa a la estricta actividad escolar, ya que éste permite no sólo el desarrollo de la Educación Ambiental, sino también la adquisición de habilidades y destrezas de las diferentes áreas (cognitiva, social, lenguaje, sensoriomotriz y plástica). Los objetivos son: trabajar los contenidos y destrezas de las áreas curriculares; conocer el nombre de las plantas y flores y hacer un seguimiento del proceso vegetativo de las mismas; aprender a relacionar los frutos del huerto con los alimentos que ellos consumen; respetar y cuidar la naturaleza; y fomentar el trabajo en equipo, responsabilizándose y compartiendo el material. La experiencia se centra por una parte en las labores normales en el huerto: preparación del terreno, siembra, cultivo, riego, recolección, etc.; y por otra, en la realización de actividades de aula, de carácter complementario, derivadas de los trabajos en el huerto: elaboración de fichas de plantas, recogida de información, dibujos y collages, etc. Además, es importante señalar que a través de estas actividades se ejercitan una serie de técnicas o habilidades que impregnan todo el currículo de Educación Especial (diálogo, conversación, convivencia, habilidades sociales, destrezas básicas, motricidad, etc.). La evaluación de la experiencia se basa en la observación continua (grabación de videos) mediante guías. En la memoria se incluye una valoración individual de cada alumno y un análisis de las tareas realizadas.

Memoria de educación compensatoria : curso 87-88.

Memoria que recoge aquellos aspectos que más destacan como logros de las actuaciones del programa de Educación Compensatoria y resalta los temas pendientes que se considera que necesita de una solución urgente en algunos casos y a medio en otros. El objetivo del programa de Educación Compensatoria es la desaparición de las desigualdades del acceso al sistema educativo por parte de grupos de individuos ya sean estas por razones económicas, sociales o de lugar de residencia. De ahí que se centre en las zonas rurales, en las aulas ocupacionales para jóvenes desescolarizados, minorías culturales y en la población itinerante. Asimismo cabe señalar que en el desarrollo del programa del curso 87-88 influyeron 2 hechos: 1) que el curso 87-88 ha estado marcado por el debate sobre la nueva ordenación del sistema educativo cuyos documentos se difundieron, leyeron y discutieron por el profesorado y por los equipos del programa, y 2) y en la segunda parte del curso por el conflicto del profesorado con la huelga y malestar generado entre el colectivo docente y las autoridades del Ministerio de Educación y Ciencia.