Hydrochemical Fluxes and their Effects on Stream Acidity in Two Forested Catchments in Central Scotland

The hydrochemical fluxes and budgets have been determined fortwo forested catchments, including inputs, tree throughfalland stemflow, soil water throughflow and output streams. Themajor vegetational induced differences are the enrichment ofsodium, chloride, sulphate and particularly hydrogen by Sitkaspruce compared to Norway spruce. These increased concentrationsare primarily due to vegetation interception along with crownleaching, both of which contribute to sulphate enhancement.Soil throughflow and consequent stream chemistries reflect thesespecies effects with additional enrichment both due to geologicalweathering of base cations as well as possible desorption ormineralization processes. Norway spruce vegetation and the associatedpodzolic soils show no net stream acidification (pH 4.61) ofinputs (pH 4.65), whereas Sitka spruce on gleyed soils showconsiderable stream acidification (pH 4.02) compared with similarinputs (pH 4.50). Both streams have similar sulphate concentrations,but this important mobile anion is associated primarily withhydrogen in the Sitka spruce dominated Kelty catchment whereasat Chon it is associated with base cations as well as hydrogen.     

A longitudinal study of lymphocyte subsets in a cohort of cats naturally-infected with feline immunodeficiency virus

Despite the potential of feline immunodeficiency virus (FIV) as an animal model for human immunodeficiency virus (HIV) studies, the long term effects of naturally-occurring infection have not been determined. HIV infection causes an ongoing deterioration in immune function which directly correlates with disease, in particular acquired immunodefciency syndrome (AIDS). However, it is not known whether FIV-induced immunosuppression is progressive or related to the clinical condition. This study examined changes in lymphocyte subset numbers of serial samples, taken from cohorts of FIV-positive and FIV-negative cats over an 18-month period. FIV-positive cats were clinically staged as asymptomatic carriers (AC) or cats with AIDS-related complex (ARC), and FIV-negative cats matched and staged on the basis of similar diseases. During the course of the study, 4 FIV-positive cats developed AIDS, classed as the terminal stage of infection. There were no significant differences in the mean absolute numbers of any lymphocyte subset between the onset (to) and the completion (t18) of the study. Similarly there were no significant changes in subset numbers during the 18 months preceding the development of AIDS. While the study period was brief and the sample sizes small, it is postulated that FIV infection in Australia may not necessarily cause progressive immunodeficiency and that FIV-induced immunosuppression (as measured by subset analysis) may not be well correlated with the clinical status of the infected cat.     

The effect and mechanism of H. polygyrus infection in T-cell-mediated inflammatory bowel disease in mice

AIM: To investigate the effect and mechanism of Heligmosomoides polygyrus (H. polygyrus) infection in mouse inflammatory bowel disease (IBD) mediated by CD4⁺ helper T-cells. METHODS: Ovalbumin (OVA) -specific CD4⁺ helper T-cells were transferred into SCID (severe combined immunodeficiency) mice to establish an IBD model. The IBD mice were infected by H. polygyrus and sacrificed 14 days later. The histological changes of the colon were observed, and the expression of interferon-gamma (IFN-γ) and interleukin-4 (IL-4) in mesenteric lymph nodes was detected by ELISA and flow cytometry. Additionally, IL-4 monoclonal antibody was intraperitoneally injected into the H. polygyrus-infected IBD mice to block the secretion of IL-4. The IL-4-blocking IBD mice were sacrificed 9 days later and the above indexes were also determined.RESULTS: Compared with the non-infection group, the H. polygyrus-infected IBD mice had more severe colonic lesions, higher level of IL-4 and lower level of IFN-γ in mesenteric lymph nodes (all P<0.05). Compared with the non-blocking group, the H. polygyrus-infected IBD mice with IL-4 blockage had less colonic lesions, lower IL-4 level and higher IFN-γ level (all P<0.05).CONCLUSION: H. polygyrus infection in CD4⁺ T-cell-mediated IBD model promotes inflammation in the early stage probably by inducing the secretion of Th2 cytokine and inhibiting the secretion of Th1 cytokine. The finding suggests that using worms for treatment of IBD needs to be cautious.     

Water intake of normal children

Estimates of daily total fluid intake and of tap-water consumption of normal children were made in four dissimilar geographic areas in the United States. (Total fluid intake increased and, relatively speaking, tap-water consumption decreased, with age.) Of basic importance in fluoridation programs was the observation that even older children rarely drank as much as 500 ml (about 1 pint) of tap water daily.     

Irrigation development on Cooper Creek,central Australia—prospects for a regulated economy in a boom-and-bust ecology

1. We take issue with a proposal to irrigate cotton crops from Cooper Creek, as the development would be in sharp contrast to the ‘boom-and-bust’ character of the local environment. In dryland rivers the flow regime is influenced by aseasonal climatic phenomena like the Southern Oscillation, so that patterns are highly variable and averages are virtually meaningless. Some irrigation developments on dryland rivers have been planned during periods that were unusually wet and, as a result, present levels of water use are not sustainable. 2. Long, dry periods are the norm in dryland rivers. The biota tolerate drought and respond to occasional floods that may have long-enduring effects (riparian trees, for example, may live for centuries). All are sensitive to the rates of rise and fall and the amplitude, duration and frequency of floods. Where the flood pulse is erratic, as in Cooper Creek, species with opportunistic traits are likely to dominate. Base flows and seasonal variations imposed by irrigation use present a very different physical environment for these species. The plan to tap the Cooper headwaters would amplify the impacts because this region is a refuge for flora and fauna. 3. In general, we contend that the Cooper Creek ecosystem could not accommodate a competitor for water that is vital for its own maintenance, and that the irrigation proposal could be rationalized only in the sophistry of short-term economics. © 1997 John Wiley & Sons, Ltd.     

Self-Assembled Smectic Phases in Rod-Coil Block Copolymers

Rod-coil block copolymers are self-assembling polymers that combine the physics of orientational ordering of rodlike polymers and the microphase separation of coil-coil block copolymers. Several new solid-state morphologies were observed in a series of anionically synthesized model poly(hexyl isocyanate-b-styrene) rod-coil diblock copolymers examined by transmission electron microscopy and selected-area electron diffraction. The rod-coils formed smectic C-like and O-like morphologies with domain sizes ranging from tens of nanometers to almost 1 micrometer. Both structural and orientational changes were found for increasing rod volume fractions. In addition, some morphologies exhibited spontaneous long-range orientational order over many tens of micrometers.     

A dielectric omnidirectional reflector

A design criterion that permits truly omnidirectional reflectivity for all polarizations of incident light over a wide selectable range of frequencies was used in fabricating an all-dielectric omnidirectional reflector consisting of multilayer films. The reflector was simply constructed as a stack of nine alternating micrometer-thick layers of polystyrene and tellurium and demonstrates omnidirectional reflection over the wavelength range from 10 to 15 micrometers. Because the omnidirectionality criterion is general, it can be used to design omnidirectional reflectors in many frequency ranges of interest. Potential uses depend on the geometry of the system. For example, coating of an enclosure will result in an optical cavity. A hollow tube will produce a low-loss, broadband waveguide, whereas a planar film could be used as an efficient radiative heat barrier or collector in thermoelectric devices.     

Pathology in the ovine foetus caused by an ovine pestivirus

Homogenised tissues or tissue culture supernatant fluid containing a noncytopathic pestivirus obtained from a lamb with a neurologic form of border disease, were inoculated into ewes at different stages of pregnancy. Foetal death occurred in 9 ewes of those inoculated between 19 and 47 days of pregnancy while 3 ewes did not lamb. Eight of the foetuses were aborted between 77 and 132 days of pregnancy; of these 6 were autolysed or mummified and one had arthrogryposis. The one full-term dead lamb had a hairy birth coat and lissencephalic micrencephaly. Foetal death occurred in only 7 of 14 ewes inoculated between 57 and 72 days of pregnancy. Four of these ewes aborted between 77 and 108 days of pregnancy and 3 gave birth to full-term, dead, hairy lambs. The remaining 7 ewes gave birth to live hairy lambs with severe inco-ordination. All lambs carried to term and aborted foetuses or lambs that could be examined had a range of intracranial malformations including focal leucomalacia, micrencephaly, hydranencephaly, porencephaly, lissencephaly and cerebellar hypoplasia. Some lambs also had skeletal abnormalities including arthrogryposis, scoliosis and brachygnathia inferior. The pestivirus isolate used in these trials produced more severe effects on the ovine foetus than previously observed in similar inoculation trials using pestivirus isolates from border disease lambs without nervous signs.