Artificial Foam Research Articles

A constant-speed penetrometer for high-resolution snow stratigraphy

A new constant-speed penetrometer for field and laboratory measurement has been developed. The initially independent work of SFISAR and CRREL has been brought together, and a portable field device is now in an advanced stage of testing. The new penetrometer has high rigidity and a high-resolution large dynamic range force sensor. It uses a much smaller sensing head (5 mm) than previous designs and has a constant-speed drive. With this construction, the penetration resistance of very fine layers and the influence of the bonding strength between snow grains can be more accurately determined than is possible with the rammsonde or Pandalp. Artificial foam layers as thin as 2 mm and thin layers in snow have been detected by the penetrometer. Thin snow layers detected from penetration-resistance profiles have been correlated to fine layering as determined from plane-section microphotographs of samples taken adjacent to the profile. The instrument’s measurements are highly repeatable and the lack of subjective decisions when operating the penetrometer makes the penetration resistance a quantitative measure of snow stratigraphy.

A constant-speed penetrometer for high-resolution snow stratigraphy

A new constant-speed penetrometer for field and laboratory measurement has been developed. The initially independent work of SFISAR and CRREL has been brought together, and a portable field device is now in an advanced stage of testing. The new penetrometer has high rigidity and a high-resolution large dynamic range force sensor. It uses a much smaller sensing head (5 mm) than previous designs and has a constant-speed drive. With this construction, the penetration resistance of very fine layers and the influence of the bonding strength between snow grains can be more accurately determined than is possible with the rammsonde or Pandalp. Artificial foam layers as thin as 2 mm and thin layers in snow have been detected by the penetrometer. Thin snow layers detected from penetration-resistance profiles have been correlated to fine layering as determined from plane-section microphotographs of samples taken adjacent to the profile. The instrument’s measurements are highly repeatable and the lack of subjective decisions when operating the penetrometer makes the penetration resistance a quantitative measure of snow stratigraphy.

Long-term effects of UV and visible irradiance on natural populations of a scytonemin-containing cyanobacterium ( Calothrix sp.)

A natural warm spring stream with a cyanobacterial biofilm community composed almost entirely of Calothrix sp., a species rich in the UV-absorbing sheath pigment scytonemin, was used for 3 month summer experiments to test the following hypotheses: (1) UV radiation is necessary for the synthesis of high scytonemin content in sheaths. (2) High scytonemin content is required for uninhibited photosynthesis under high UV flux. Both of these hypotheses were answered affirmatively in earlier experiments with laboratory cultures of other cyanobacterial species. However, the tests of these hypotheses under natural conditions were necessary to confirm these conclusions, mainly because fluxes of UV and visible radiation and their ratios are very different under field conditions. Intact mats of Calothrix, siliceous substrate cleared of Calothrix, and artificial foam were treated for 3 months under filters transparent to UV radiation and visible light, and under filters that excluded only UV radiation. Neutral density screens were used in combination with filters to reduce the total irradiance over some sections of the stream. After 3 months, under all treatments, the predominant organism was still the same morphotype of Calothrix. Intact Calothrix mats produced high levels of scytonemin over the summer, except under low UV and low visible irradiance, while chlorophyll-a values per unit area remained relatively low and showed little change under all treatments. After 3 months, intact Calothrix mat and colonized mat with substantial scytonemin were not inhibited photosynthetically by UV irradiance. Only colonized populations exposed to ∼12% UV and ∼12% visible irradiance, and with very low scytonemin content, showed significant UV-inhibition. Thus, the correlation between UV protection and scytonemin presence was established experimentally for the first time under solar irradiance in a natural, essentially monospecific population of a cyanobacterium.

Further studies on efficiency of artificial foam in trapping conidia of Ingoldian fungi

Artificial foam traps conidia of rare species in rich communities of freshwater hyphomycetes as efficiently as it traps conidia in a community showing poor species composition with low conidial numbers. A large number of conidia, particularly the tetraradiate ones, are lost from the stream water as it passes through rapids and waterfalls. Addition of a detergent results in greater loss of conidia in the effluent water. The trapping of conidia in the foam concentrate and their loss while passing through the rapids and waterfalls is not related to conidial concentration. It may be influenced by water chemistry. Key words: artificial foam, conidia, Ingoldian fungi.

Species diversity of freshwater hyphomycetes in some streams of Pakistan. Comparison of sampling techniques

Freshwater hyphomycete communities in four streams were sampled by filtration of water samples, trapping conidia in artificial foam, and examination of alder leaf pack baits and random sampling of naturally occurring submerged leaves. No two communities of freshwater hyphomycetes detected by different sampling techniques used singly in a stream showed 100% similarity. Based on relative frequency values, the same 10 top-ranking species in a stream were detected by artificial foam trap and on the baited leaves. These species differed in ranking, and the community in artificial foam was riche than on baited leaves. Of the various communities detected by different sampling techniques used singly or in combination, those detected by artificial foam trap or a combination of this technique with leaf baiting or with leaf baiting and randomly sampled leaves or filtration showed the highest similarity to the total community based on data generated using four sampling techniques simultaneously.

Evaluation of the Virus Permeability of a New Condom for Women

The authors tested a polyurethane women's condom for permeability to the human immunodeficiency virus (HIV) and cytomegalovirus (CMV) using an artificial intercourse model. They did not detect viral leakage in three trials for each virus. Use of this device, which can be controlled by the woman, may reduce HIV and CMV infection.