Dynamic properties of molecularly thin liquid films

An experimental technique is described for simultaneously measuring the static and dynamic interactions of very thin liquid films between two surfaces as they are moved normally or laterally relative to each other. Film thickness can be measured and controlled to 1 angstrom. Initial results are presented of the transition in the physical properties of liquid films only one molecular layer thick to thicker films whose properties are practically indistinguishable from the bulk. In particular, the results show that two molecularly smooth surfaces, when close together in simple liquids, slide (shear) past each other while separated by a discrete number of molecular layers, and that the frictional force is "quantized" with the number of layers.     

Probing c60

Experiments involving the laser vaporization of graphite have indicated that one particular duster of carbon, C(60), is preeminently stable; this special stability may be evidence that C(60) can readily take the form of a hollow truncated icosahedron (a sort of molecular soccerball). If true, this structure for C(60) would be the first example of a spherical aromatic molecule. In fact, because of symmetry properties unique to the number 60, it may be the most perfecty spherical, edgeless molecule possible. Its rapid formation in condensing carbon vapors and its extreme chemical and photophysical stability may have far-reaching implications in a number of areas, particularly combustion science and astrophysics. For these reasons C(60) and other dusters of carbon have continued to be the subject of intense research. This article provides a short review of the many new experimental probes of the properties of C(60) and related carbon dusters.     

Soil acidity, and the growth, biomass partitioning and leaf mineral composition of honeylocust (Gleditsia triacanthos L.) seedlings

Honeylocust seedlings (Gleditsia triacanthos L.) were grown in cylinders containing soil adjusted to pH 4, 5 or 6, and harvested every 10 days for 40 days for dry weight and leaf mineral analysis. Total weight of plants grown at pH 4 was less than that of plants grown at pH 5 or 6. Root weight accounted for a greater proportion of total weight in plants grown at pH 4 than in plants grown at pH 5 or 6. Root growth as a function of total plant growth was higher in plants grown at pH 4 than in plants grown at pH 5 or 6, whereas leaf growth as a function of total plant growth was less in plants grown at pH 4 than in plants grown at pH 5 or 6. However, the relationships between root biomass and root length and between leaf biomass and leaf area were the same in all treatments. An analysis of total leaf concentrations of Ca, P, K, Mg, Mn and Al indicated that Al accumulation in leaves was significantly related to a decrease in plant growth at pH 5. A leaf tissue aluminum concentration of 35 microg g(-1) was associated with toxicity symptoms and a 25% reduction in total plant weight.     

Simple, rapid method for determination of total extractable fat in canned pet foods

The rapid column method described, unlike AOAC method 7.056, determines both neutral ("crude") and total fat in canned pet foods, and uses nonflammable solvent mixtures and simple laboratory equipment. Neutral fat values are obtained by eluting the column with dichloromethane, whereas total fat values are determined by using dichloromethane-methanol (9 + 1). For 7 samples analyzed in triplicate, fat ranged from 2.9 to 10.8%. Neutral fat values by the dry column method were significantly lower (P less than 0.05) than were those by 7.056 (6.29 vs 6.49), although these differences were practically unimportant. Total fat determinations by the dry column method and by 7.056 yielded overall means of 7.40 and 6.49%, respectively. The 0.91% mean difference is significant (P less than 0.01) and represents a more complete extraction of polar lipids by the proposed method.     

An exploration of Cryoprotective compounds for fowl spermatozoa

1. Glycerol is an effective cryoprotective for fowl spermatozoa, but after thawing the frozen semen it must be reduced in concentration from the level adequate to protect spermatozoa during freezing, otherwise it has a contraceptive action.

2. A series of alternative cryoprotective compounds were tested for their effect on fertility when fowl spermatozoa were inseminated fresh in their presence. Under these circumstances dimethylsulphoxide, dimethylaceta‐mide, ethane‐diol, propane‐diol and methylpyrrolidone did not depress fertility when used in concentrations equivalent to that of glycerol or in amounts reported previously to be non‐toxic and adequate to protect cells during freezing.

3. Dimethylacetamide was compared with propane‐diol for use in freezing fowl semen and the former enabled encouraging levels of fertility to be obtained.     

Salmon poisoning disease in dogs on southern vancouver island

Salmon poisoning disease in dogs has previously been reported in North America only along the western coast of the U.S.A. This paper presents the findings from eight affected dogs recently diagnosed on Vancouver Island, Canada. The clinical signs shown by these dogs were lethargy, anorexia, pyrexia and lymph node enlargement. The causative agent, Neorickettsia helminthoeca was observed in macrophages obtained from lymph node aspirates. This organism is transmitted to dogs in cysts of the fluke Nanophyetus salmincola salmincola within the tissues of the salmon or trout. The presence of fluke eggs in the feces of dogs showing typical signs is very suggestive of a diagnosis of salmon poisoning disease. Appropriate treatment, including chloramphenicol or oxytetracycline and fluid therapy, resulted in recovery. Prevention of salmon poisoning disease in endemic areas can be achieved by advising owners against allowing their dogs to eat raw salmon or trout. We suggest, based on the diagnoses made in these eight dogs, that Vancouver Island now be considered an endemic area for salmon poisoning disease.     

Intracranial schwannoma in a cow

A nine year old Hereford crossbred cow with a history of progressive neurological signs was referred to the Western College of Veterinary Medicine, Saskatoon. A large intracranial mass, histologically identified as a schwannoma, was found to be compressing the left brain stem and appeared to have arisen from the left fifth cranial nerve.