Drop attacks

Simultaneous bilateral transient motor or sensory loss is almost always caused by brainstem ischemia. Sudden simultaneous bilateral blindness in elderly patients usually indicates bilateral occipital ischemia. Vertigo, diplopia, dysphagia, unsteadiness, tinnitus, amnesia, drop attacks and dysarthria may be caused by posterior circulation or more global cerebral ischemia, or by non-vascular causes such as motor neuron disease or myesthenia in the case of dysarthria. If these symptoms occur in isolation, the diagnosis of TIA should only be considered after exclusion of other possibilities (Gomez et al. 1996 Bos et al. 2007). Global symptoms such as a reduced level of consciousness are almost never caused by a TIA. They can only be accepted as resulting from a TIA if there are additional focal symptoms that are unlikely to be epileptic or syncopal. 

Drop attacks affect middle-aged and elderly women, almost only when walking rather than just standing or sitting (Stevens and Matthews 1973). Without warning, the patient falls to... 

Cardiovascular syncope is the commonest cause of drop attacks in the older patient. European Journal of Cardiac Pacing and Electrophysiology 6 84-88... 

Stevens DL, Matthews WB (1973). Cryptogenic drop attacks an affliction of women. British Medical Journal 1 439-442 Stroke Prevention in Atrial Fibrillation Investigators (1995). Risk factors for... 

The Baylor doctors reported in 1967 a case of right vertebral artery blockage. The vertebral arteries are small, extremely important, and totally inaccessible blood vessels that travel from the heart, up the back of the spinal column, to the back of the brain. If one or both of these arteries become blocked you are in deep trouble. You lose speech, vision, and balance. Some victims of this type of blockage have "drop attacks." They drop to the floor just as if someone had cut their legs from under them. This happens without the slightest loss of consciousness. An inexperienced doctor will think the patient is faking because of the lack of mental change with the episode. It is a peculiar and mysterious medical phenomenon. 

A donble-blind stndy revealed topiramate to be eqniva-lent to valproate and carbamazepine in children and adnlts with newly diagnosed partial and primary generalized epilepsy. Additional stndies disclosed topiramate to be effective as monotherapy for refractory partial epilepsy and refractory generalized tonic-clonic seizures. Topiramate also was found to be sigifificantly more effective than placebo against both drop attacks and tonic-clonic seizures in patients with Lennox-Gastaut syndrome. 

In atonic seizures, a very sudden decrease In muscle tone occurs, leading to a head drop, drooping of a limb, or loss of all muscle tone, resulting In falling. The risk of Injury Is high In these sudden drop attacks." Atonic seizures are more common In... 

Treat the distillate with 2 drops of glacial acetic acid (to destroy the phosphorus esters present) and redistil using the same apparatus as before except that the separatory funnel is replaced by a thermometer. Collect the liquid which passes over at 50-56°. Transfer the acetyl chloride to a weighed glass-stoppered bottle (since cork and rubber stoppers are attacked) and determine the weight. The yield is 22 g. 

The completion stage is identified by the fact that all the monomer has diffused into the growing polymer particles (disappearance of the monomer droplet) and reaction rate drops off precipitously. Because the free radicals that now initiate polymerization in the monomer-swollen latex particle can more readily attack unsaturation of polymer chains, the onset of gel is also characteristic of this third stage. To maintain desirable physical properties of the polymer formed, emulsion SBR is usually terminated just before or at the onset of this stage. 

The ease with which the ferrous ion can be oxidized to a ferric ion in the electrowinning cell furthers this reaction. Attack on the copper is most apparent at the solution line, where it results in corrosion of the loops supporting the cathodes, leading to dropped cathodes. 

Reduction of oxygen is one of the predominant cathodic reactions contributing to corrosion. Awareness of the importance of the role of oxygen was developed in the 1920s (19). In classical drop experiments, the corrosion of iron or steel by drops of electrolytes was shown to depend on electrochemical action between the central relatively unaerated area, which becomes anodic and suffers attack, and the peripheral aerated portion, which becomes cathodic and remains unattacked. In 1945 the linear relationship between rate of iron corrosion and oxygen pressure from 0—2.5 MPa (0—25 atm) was shown (20). 

Fresh acid attack is recognized by the absence of corrosion product in wasted areas and the sharpness of attack. Oxide layers are usually easily stripped by a test drop of hydrochloric acid in freshly corroded areas. Deposits are almost always absent. Edges of attacked areas are sharp and angular, as intervening corrosion has not recently occurred. In stainless steels such distinctions blur, as corrosion in intervening periods is usually slight. 

Mechanical stirring is not strictly necessary however, severe bmnping is sometimes encountered if it is not used. Hydrazine attacks both cork and rubber. If a dropping fimnel with ground glass joint is not available, an ordinary dropping funnel may be placed at the top of the reflux condenser. 

Impingement is corrosion caused by aerated water streams constricting metal surfaces. It is similar to erosion corrosion in which air bubbles take the place of particles. The pits formed by impingement attack have a characteristic tear drop shape. 

It is obtained by allowing a solution of one molecule of phenol-acetic -ester in three to four times its weight of absolute alcohol, to fall in drops on a quantity of sodium calculated for six atoms. It is then heated for several hours on an oil-bath, until the sodium has disappeared, if necessary adding more alcohol. After cooling, water is added, and the ester which is not attacked is saponified. The alcohol and phenyl-ethyl alcohol are then distilled off with steam, when the latter is at once obtained in the pure state. 

Fig. 1.48 Examples of differential aeration cells (a) and (b) Differential aeration cells formed by the geometry of a drop of NaCl solution on a steel surface (c) differential aeration cells formed by the geometry of a vertical steel plate partly immersed in a NaCl solution. Increasing concentrations of Na2 CO3 decrease the anodic area (d) until at a sufficient concentration attack is confined to the water line (e) (/) shows the membrane of corrosion products formed at water...

White rust If a fresh zinc surface is allowed to stand with large drops of dew on it, as may easily happen if it is stored in a closed place in which the temperature varies periodically, it is attacked by the oxygen dissolved in the water, owing to differential aeration between the edges and the centres of the drops. A porous form of zinc oxide builds up away from the surface and quickly takes up carbon dioxide from the air to form the basic carbonate known as white rust or wet storage stain. 

Pt is attacked by bromine trifluoride at 280° in the presence of K fluoride (Ref 5). Finely divided Pt and some other metals will cause a mixt of Hj and 02 to explu at ordinary temps (Ref 1). A little Pt black dropped into a hydrogen peroxide soln can cause an expln (Ref 2). Pt and molten Ii react violently at 540° 20° (Ref 7), and an incandescent reaction occurs when it is wanned gently in gaseous oxygen difluoride (Ref 6). The decompn of 92% per-monosulfuric acid is expl in the presence of smooth or finely divided Pt (Ref 3). The re-. acting mass formed by the mixt of P and Pt can become incandescent when heated (Ref 8). Dry, used Pt catalyst has exWd while being screened (Ref 4)... 

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