Pirna

Pirna is a town in the Free State of Saxony, Germany, capital of the administrative district Sächsische Schweiz-Osterzgebirge. The town's population is over 37,000. Pirna is located near Dresden and is an important district town as well as a Große Kreisstadt. It is also known for the gassing of about 15,000 disabled people in Sonnenstein Castle between June 1940 and August 1941, killings which ceased after pressure was exerted on the authorities by the local population. Today, a small plaque at the base of Sonnenstein Castle and the Sonnenstein Memorial remembers the dead.

Geography

Geographical location

Pirna is located near the Sandstone Mountains in the Elbe valley, where the nearby rivers Wesenitz, in the north, and Gottleuba to the south, flow into the Elbe. Pirna is also called the "gate to the Saxon Switzerland" (Ger: Tor zur Sächsischen Schweiz). The Saxon wine region (Sächsische Weinstraße), stretches from Pirna over Pillnitz, Dresden, and Meissen to Diesbar-Seußlitz, was dedicated in 1992. In August 2002, the town suffered great damage in the widespread flooding in Europe at the time. This was particularly unfortunate as it undid many well-executed restoration schemes carried out post 1990 re-unification.

Pirna 014

The Pirna 014 was an axial turbojet designed in East Germany (or the GDR) in the mid- to late 1950s by former Junkers engineers, who were repatriated to East Germany in 1954 after being held in custody in the Soviet Union following World War II.

Origin

After the remaining groups of German engineers that were not already expatriated to Germany were concentrated in Sawjelowo north of Moscow in December 1953, planning for a civilian airliner that was to be powered by four jet engines started. Head of engine research & development was (then Dipl.-Ing.) Ferdinand Brandner, whereas (then Dipl.-Ing.) Brunolf Baade was given the general project lead.

Before Brandner, after being forced to stay in the Soviet Union for 9 years, finally went back to his family in Austria he selected his deputy (then Dr.-Ing.) Rudolf Scheinost to continue his works and to lead the engine development. The engine project 014, a continuation of the numbering sequence of previous Jumo jet engines, was at this time named Dwigatel 014 (from reactivnyi dvigatel, literally "jet drive") and given the main focus.

Piwi-interacting RNA

Piwi-interacting RNA (piRNA) is the largest class of small non-coding RNA molecules expressed in animal cells. piRNAs form RNA-protein complexes through interactions with piwi proteins. These piRNA complexes have been linked to both epigenetic and post-transcriptional gene silencing of retrotransposons and other genetic elements in germ line cells, particularly those in spermatogenesis. They are distinct from microRNA (miRNA) in size (26–31 nt rather than 21–24 nt), lack of sequence conservation, and increased complexity.

It remains unclear how piRNAs are generated, but potential methods have been suggested, and it is certain their biogenesis pathway is distinct from miRNA and siRNA, while rasiRNAs are a piRNA subspecies.

Characteristics

piRNAs have been identified in both vertebrates and invertebrates, and although biogenesis and modes of action do vary somewhat between species, a number of features are conserved. piRNAs have no clear secondary structure motifs, the length of a piRNA is, by definition, between 26 and 31 nucleotides, and the bias for a 5’ uridine is common to piRNAs in both vertebrates and invertebrates. piRNAs in Caenorhabditis elegans have a 5’ monophosphate and a 3’ modification that acts to block either the 2’ or 3’ oxygen, and this has also been confirmed to exist in Drosophila melanogaster,zebrafish,mice and rats. This 3’ modification is a 2’-O-methylation; the reason for this modification is not clear, but it has been suggested to increase piRNA stability. It is thought that there are many hundreds of thousands of different piRNA species found in mammals. Thus far, over 50,000 unique piRNA sequences have been discovered in mice and more than 13,000 in D. melanogaster.