In the spring of 1854 the Russians again advanced, crossing the Danube River into the Turkish province of Dobruja. By April 1854, the Russians had reached the lines of Trajan's Wall where they were finally halted. In the center, the Russian forces crossed the Danube and laid siege to Silistra from 14 April with 60,000 troops, the defenders with 15,000 had supplies for three months.:415 The siege was lifted on 23 June 1854. The English and French forces at this time were unable to take the field for lack of equipment.:415
When did the siege of Silistra end?
23 June 1854

Another extreme case of impedance matching occurs when using a small loop antenna (usually, but not always, for receiving) at a relatively low frequency where it appears almost as a pure inductor. Resonating such an inductor with a capacitor at the frequency of operation not only cancels the reactance but greatly magnifies the very small radiation resistance of such a loop.[citation needed] This is implemented in most AM broadcast receivers, with a small ferrite loop antenna resonated by a capacitor which is varied along with the receiver tuning in order to maintain resonance over the AM broadcast band
What magnifies the small radiation resistance of a loop?
a capacitor at the frequency of operation

In order to reduce negative impacts, it is desirable that pesticides be degradable or at least quickly deactivated in the environment. Such loss of activity or toxicity of pesticides is due to both innate chemical properties of the compounds and environmental processes or conditions. For example, the presence of halogens within a chemical structure often slows down degradation in an aerobic environment. Adsorption to soil may retard pesticide movement, but also may reduce bioavailability to microbial degraders.
What feature is wanted to assist with reducing negative impacts of pesticides?
that pesticides be degradable