Impressive abrasion rates of marked pebbles on a coarse-clastic beach within a 13-month timespan

In this paper the abrasion rate on a coarse-clastic beach was evaluated by calculating the volume loss recorded on indigenous pebbles within a 13-month timespan. The experiment was carried out at Marina di Pisa (Italy) on an artificial beach that was built to counteract the erosion processes affecting this sector of the coast. A total of 240 marble pebbles (120 rounded and 120 angular) were marked using the RFID technology and injected on the beach. The volume loss measured after consecutive recovery campaigns was progressively increasing, reaching the maximum value after 13 months (61% overall). The average volume loss is consistent between rounded and angular pebbles at any time (59.3% and 64.2% after 13 months respectively), meaning that the roundness is not a primary control factor on abrasion rate. The pebbles that did not reach such abrasion rates after 8 and 10 months (volume loss less than 20%) were found at heights equal or greater than 2 m above mean sea level, on the crest of the storm berm that formed during the strongest storms. This implies that the highest wearing is achieved in the lower portion of the backshore, which is also the area that underwent major topographic modifications. Here, sea water action might also exert chemical influence on the pebbles, adding to the mechanical abrasion. The main result of this research, indicating an impressive volume loss on beach pebbles in a short timespan, could be of key importance for coastal managers. The optimization of coarse sediment beach nourishments is also relevant, taking into right consideration that the volume loss due to sediment abrasion might exceed 50% of the original fill volume just after 1 year in the most dynamic portion of the beach

Foszforheterociklusok szintézise és hasznosítása = The synthesis and use of phosporus heterocycles

A kutatás három fő szálon futott, egyrészt az 5- és 6-tagú, másrészt a 7- és 8-tagú - ez utóbbi esetben áthidalt - P-heterociklusok területén, harmadrészt egy inverz Wittig-típusú reakció témájában. Újfajta foszfol- és a 3-as helyzetben foszforfunkciót tartalmazó 1,2,3,6-tetra- és 1,2,3,4,5,6-hexahidrofoszfinin P-ligandokat (ill. ez utóbbiak prekurzorait) tettük hozzáférhetővé, amelyeket átmeneti fémkomplexekké is átalakítottunk. A P-ligandok és a komplexek térszerkezetét felderítettük és ez utóbbiak egy részét katalizátorként is kipróbáltuk. Jónéhány dibenzooxafoszforint - közöttük optikai aktivitással rendelkező származékokat is - előállítottunk. A ligandok platina-komplexeit is elkészítettük. A kutatás másik vonalán új 7-foszfanorbornén, ill. 2-foszfabiciklo[2.2.2]oktén 2-oxid származékokat vezettünk be, egyrészt új szubsztituensek, másrészt új dienofilek alkalmazásával. A prekurzorokat reakcióképes intermedierek képzésén át foszforilezési reakciókban hasznosítottuk. Tanulmányoztuk a reakciók mechanizmusát és oxafoszfabiciklookténeket is vizsgáltunk. A harmadik témában a P-aril gyűrűs foszfin-oxidok és a dialkilacetiléndikarboxilát béta-oxofoszforánokat eredményező reakcióinak mechanizmusát derítettük fel és megfontoltuk az oxafoszfetének mint intermedierek lehetőségét. A béta-oxofoszforánokat kerülő szintézissel is hozzáférhetővé tettük és tanulmányoztuk néhány jellemző reakciójukat. | The research was performed in three topics, on one hand in the topic of 5- and 6-membered P-heterocycles, on the other hand in the field of 7- and 8-membered P-cycles including bridged derivatives, and finally in the topic of the inverse Wittig type reaction. New phosphole and 1,2,3,6-tetra- and 1,2,3,4,5,6-hexahydrophosphinine P-ligands - these latter with exocyclic P-function in position three - were made available that were also transformed to transition metal complexes. Stereostructure of the P-ligands and complexes was evaluated and a part of the latter was tested as catalyst. A number of dibenzooxaphosphorines and their platinum complexes were also prepared. In the second line of the research, new 7-phosphanorbornene- and 2-phosphabicyclo[2.2.2]octene 2-oxide derivatives were introduced and utilized in fragmentation related phosphorylation of nucleophiles. Beside the mechanistic studies, oxaphosphabicyclooctenes were also studied. In the third topic, the mechanism of the inverse Wittig type reaction of cyclic phosphine oxides and dialkyl acetylenedicarboxylate resulting in beta-oxophosphoranes was studied. Oxaphosphetes were considered as possible intermediates. The beta-oxophosphoranes were also prepared by an independent synthesis and some of their reactions were investigated