The development of an early warning system to detect trends in illicit drug use in Australia: The illicit drug reporting-system

Appropriate ways to monitor the availability and use of illicit drugs were examined. Four methods were tested concurrently: (1) a quantitative survey of injecting drug users, (2) a qualitative key informant study of illicit drug users and professionals working in the drug field, (3) examination of existing sources of survey, health and law enforcement data and (4) an ethnographic study of a high risk group of illicit drug users. The first three methods were recommended for inclusion in an ongoing national monitoring system, enabling the collection of both quantitative and qualitative data on a range of illicit drugs in a relatively brief, quick and cost-effective manner. A degree of convergent validity was also noted among these methods, improving the degree of confidence in drug trends. The importance of injecting drug users as a sentinel population of illicit drug users was highlighted, along with optimal methods for qualitative research.

Field evidence for mechanical transmission of rabbit haemorrhagic disease virus (RHDV) by flies (Diptera : Calliphoridae) among wild rabbits in Australia

Field collected flies were screened for the presence of rabbit haemorrhagic disease virus (RHDV) by applying reverse transcriptase PCR (RT-PCR) in which primers specific to the capsid protein of the virus were used. The virus was detected in flies from locations where rabbit haemorrhagic disease (RHD) was reported and also soon after the release of RHDV in a 'clean' area. Oral and/or anal excretions of flies (flyspots) were found to contain viable virus and oral inoculation of rabbits revealed that a single flyspot was able to cause RHD. We conclude that flyspots are a major potential source of the virus for oral or conjunctival transmission of the virus to rabbits. (C) 1998 Elsevier Science B.V. All rights reserved.

Shift of the subharmonic resonances and suppression of fluorescence in a two-level atom driven by a bichromatic field

We study the behavior of a two-level atom that is driven by a bichromatic field consisting of a strong resonant component and a weaker tunable component. In addition to the splitting of the energy levels (the multiphoton AC Stark effect), we find that the weaker component also shifts the subharmonic resonances, an effect we attribute to a dynamic Stark shift. When the weaker component is tuned to a shifted resonance, no fluorescence occurs at either the frequency of the strong component or the three-photon mixing frequency. Results are obtained with numerical techniques and explained in terms of the dressed-atom model of the system. (C) 1998 Optical Society of America [S0740-3224(98)01508-2] OCIS codes: 270.4180, 270.6620, 270.0270.

Resonance fluorescence spectrum in a weak squeezed field with an arbitrary bandwidth

We analyze the linewidth narrowing in the fluorescence spectrum of a two-level atom driven by a squeezed vacuum field of a finite bandwidth. It is found that the fluorescence spectrum in a low-intensity squeezed field can exhibit a (omega - omega(0))(-6) frequency dependence in the wings. We show that this fast fall-off behavior is intimately related to the properties of a narrow-bandwidth squeezed field and does not extend into the region of broadband excitation. We apply the Linear response model and find that the narrowing results from a convolution of the atom response with the spectrum of the incident field. On the experimental side, we emphasize that the linewidth narrowing is not sensitive to the solid angle of the squeezed modes coupled to the atom. We also compare the fluorescence spectrum with the quadrature-noise spectrum and find that the fluorescence spectrum for an off-resonance excitation does not reveal the noise spectrum. We show that this difference arises from the competing three-photon scattering processes. [S1050-2947(98)04308-X].

Interference pattern with a dark center in resonance fluorescence from two atoms driven by a squeezed vacuum field

We study the resonance fluorescence from two interacting atoms driven by a squeezed vacuum field and show that this system produces an interference pattern with a dark center. We discuss the role of the interatomic interactions in this process and find that the interference pattern results from an unequal population of the symmetric and antisymmetric states of the two-atom system. We also identify intrinsically nonclassical effects versus classical squeezed field effects, (C) 1998 Elsevier Science B.V. All rights reserved.

Sources of information about HIV/AIDS and perceived risk of infection among heterosexual young adults: 1989 and 1994

This paper reports a study of sources of information about HIV/AIDS and trust of the sources among heterosexuals in 1989 (113 females and 91 males) and 1994 (185 females and 66 males). We also examined whether perceived personal risk of HIV infection was predicted by sources of information about HIV/AIDS, trust of the sources, how informed about AIDS people believed they were, and perceived risk of infection to others, as well as whether there was a relationship between perceived personal risk and safe sex behaviour Participants received most of their information about AIDS/HIV from magazines, newspapers, and television, but placed most trust on sources such as doctors and HIV/AIDS organisations. Perceived personal risk was influenced most by perceived risk to friends and to people with the same sexual practices. In the 1994 sample, perceived personal risk was correlated with the amount of condom use among participants with sexual experience. These results indicate ther has been. relative stability across a five-year period. They also point to the continuing discrepancy among young heterosexuals between the most-used and most-trusted sources of information, as well as to the importance of peer influence on perceptions of personal risk of HIV infection.

Spectral linewidth narrowing by a weak squeezed field of an arbitrary bandwidth

We study the spectral and noise properties of the fluorescence field emitted from a two-level atom driven by a beam of squeezed light. For a weak driving field we derive simple analytical formulae for the fluorescence and quadrature-noise spectra which are valid for an arbitrary bandwidth of the squeezed field. We analyse the spectra in the regime where the squeezing bandwidth is smaller or comparable to the atomic linewidth, the area where non-Markovian effects are important. We emphasize that there is a noticable difference between the fluorescence spectra for the thermal and squeezed field excitations. In both cases the spectrum can be narrower than any bandwidth involved in the process. However, as we point out for the squeezed driving field the linewidth narrowing, being much larger than in the thermal-field case, can be attributed to the squeezing of the fluctuations in the driving held. We also calculate the quadrature-noise spectrum of the emitted fluorescence, and find that for a detuned squeezed field the fluorescence spectrum does not reveal the quadrature-noise spectrum. In contrast to the fluorescence spectrum having two peaks, the quadrature-noise spectrum exhibits three peaks. We explain this difference as arising from the competiting three-photon scattering processes. (C) 1998 Elsevier Science B.V. All rights reserved.

Subantarctic Macquarie Island - a model ecosystem for studying animal-derived nitrogen sources using N-15 natural abundance

Plants collected from diverse sites on subantarctic Macquarie Island varied by up to 30 parts per thousand in their leaf delta(15)N values. N-15 natural abundance of plants, soils, animal excrement and atmospheric ammonia suggest that the majority of nitrogen utilised by plants growing in the vicinity of animal colonies or burrows is animal-derived. Plants growing near scavengers and animal higher in the food chain had highly enriched delta(15)N values (mean = 12.9 parts per thousand), reflecting the highly enriched signature of these animals' excrement, while plants growing near nesting penguins and albatross, which have an intermediate food chain position, had less enriched delta(15)N values (> 6 parts per thousand). Vegetation in areas affected by rabbits had lower delta(15)N values (mean = 1.2 parts per thousand), while the highly depleted delta(15)N values (below -5 parts per thousand) of plants at upland plateau sites inland of penguin colonies, suggested that a portion of their nitrogen is derived from ammonia (mean N-15 = -10 parts per thousand) lost during the degradation of penguin guano. Vegetation in a remote area had delta(15)N values near -2 parts per thousand. These results contrast with arctic and subarctic studies that attribute large variations in plant N-15 values to nitrogen partitioning in nitrogen-limited environments. Here, plant N-15 reflects the N-15 Of the likely nitrogen sources utilised by plants.

X-ray properties of the Parkes sample of flat-spectrum radio sources: dust in radio-loud quasars?

We investigate the X-ray properties of the Parkes sample of Bat-spectrum radio sources using data from the ROSAT All-Sky Survey and archival pointed PSPC observations. In total, 163 of the 323 sources are detected. For the remaining 160 sources, 2 sigma upper limits to the X-ray flux are derived. We present power-law photon indices in the 0.1-2.4 keV energy band for 115 sources, which were determined either with a hardness ratio technique or from direct fits to pointed PSPC data if a sufficient number of photons were available. The average photon index is <Gamma > = 1.95(-0.12)(+0.13) for flat-spectrum radio-loud quasars, <Gamma > = 1.70(-0.24)(+0.23) for galaxies, and <Gamma > = 2.40(-0.31)(+0.12) for BL Lac objects. The soft X-ray photon index is correlated with redshift and with radio spectral index in the sense that sources at high redshift and/or with flat (or inverted) radio spectra have flatter X-ray spectra on average. The results are in accord with orientation-dependent unification schemes for radio-loud active galactic nuclei. Webster et al. discovered many sources with unusually red optical continua among the quasars of this sample, and interpreted this result in terms of extinction by dust. Although the X-ray spectra in general do not show excess absorption, we find that low-redshift optically red quasars have significantly lower soft X-ray luminosities on average than objects with blue optical continua. The difference disappears for higher redshifts, as is expected for intrinsic absorption by cold gas associated with the dust. In addition, the scatter in log(f(x)/f(o)) is consistent with the observed optical extinction, contrary to previous claims based on optically or X-ray selected samples. Although alternative explanations for the red optical continua cannot be excluded with the present X-ray data, we note that the observed X-ray properties are consistent with the idea that dust plays an important role in some of the radio-loud quasars with red optical continua.

The solution structure of a copper(II) compound of a new cyclic octapeptide by EPR spectroscopy and force field calculations

A new cyclic octapeptide, cyclo(Ile-Ser-(Gly)Thz-Ile-Thr-(Gly)Thz) (PatN), related to patellamide A, has been synthesized and reacted with copper(II) and base to form mono- and dinuclear complexes. The coordination environments around copper(TI) have been characterized by EPR spectroscopy. The solution structure of the thermodynamically most stable product, a purple dicopper(TI) compound, has been examined by simulating weakly dipole-dipole coupled EPR spectra based upon structural parameters obtained from force field (MM and MD) calculations. The MM-EPR method produces a saddle-shaped structure for [Cu-2(PatN)(OH2)(6)] that is similar to the known solution structure of patellamide A and the known solid-state structure of [Cu-2(AscidH(2))CO3(OH2)(2)]. Compared with the latter, [Cu-2(PatN)] has no carbonate bridge and a significantly flatter topology. The MM-EPR approach to solution-structure determination for paramagnetic metallopeptides may find wide applications to other metallopeptides and metalloproteins.

Inactive Australian college students' preferred activities, sources of assistance, and motivators

Participation in regular physical activity reduces the risk of cardiovascular disease and all-cause mortality as well as providing numerous health benefits.' The steepest decline in physical activity occurs during adolescence (approximately 15 to 18 years of age) and young adulthood (20 to 25 years).(2) Australian population studies have found that levels of physical inactivity are twice as high for those 20 to 29 years old as they are for those under 20 years old.(3,4) As college students move through this period of changing roles within family and peer groups, they may be expected to have specific preferences and expected outcomes for physical activity participation that are different from those they had previously as high school students.(5) Studies of physical activity determinants suggest that while there are some similarities between males and females, there are differences in preferences for specific types of activity.(6) Calfas et al.(5) found that women reported body image factors (weight loss, dissatisfaction with body) to be more motivating, while young men rated strength (muscle gain, muscle tone) and social aspects (organized competition, meeting people) of physical activity more highly than did young women. We examined preferred physical activities, sources of assistance to be more active, and perceived motivators for activity in a sample of inactive college students. Differences between males and females were examined, and the implications for campus-based physical activity promotion strategies are considered.

Therapeutic efficacy of zeta-cypermethrin pour-on for the treatment of biting and sucking lice in cattle under field conditions

Objective To assess the efficacy of zeta-cypermethrin pour-on to control cattle lice. Design Five field trials in south-eastern Australia. Procedure Zeta-cypermethrin pour-on, deltamethrin pour-on and pour-on vehicle were applied to groups of 10 cattle. Lice were counted before treatment and 14, 28, 42 and 56 days after treatment. Results Zeta-cypermethrin pour-on given at 2.5 mg/kg was equivalent to, or marginally more effective than a deltamethrin pour-on at 0.75 mg/kg. It eliminated B bovis and H eurysternus and gave good control of L vituli and S capillatus. Zeta-cypermethrin at 1 mg/kg gave good control of B bovis and H eurysternus but was not satisfactory against L vituli and S capillatus. Conclusion Zeta-cypermethrin pour-on, given at 2.5 mg/kg, is an effective treatment for cattle lice control. Zeta-cypermethrin, and other synthetic pyrethroid pour-ons, are the treatment of choice to control B bovis.

Availability of two forms of dissolved nitrogen to the coral Pocillopora damicornis and its symbiotic zooxanthellae

The relative contribution of dissolved nitrogen (ammonium and dissolved free amino acids DFAAs) to the nitrogen budget of the reef-building coral Pocillopora damicornis was assessed for colonies growing on control and ammonium-enriched reefs at One Tree Island (southern Great Barrier Reef) during the ENCORE (Enrichment of Nutrient on Coral Reef; 1993 to 1996) project. P. damicornis acquired ammonium at rates of between 5.1 and 91.8 nmol N cm(-2) h(-1) which were not affected by nutrient treatment except in the case of one morph. In this case, uptake rates decreased from 80.5 to 42.8 nmol cm(-2) h(-1) (P < 0.05) on exposure to elevated ammonium over 12 mo. The presence or absence of light during measurement did not influence the uptake of ammonium ions. Nitrogen budgets revealed that the uptake of ammonium from concentrations of 0.11 to 0.13 mu M could completely satisfy the demand of growing P. damicornis for new nitrogen. P. damicornis also took up DFAAs at rates ranging from 4.9 to 9.8 nmol N cm(-2) h(-1). These rates were higher in the dark than in the light (9.0 vs 5.1 nmol m(-2) h(-1), P < 0.001). Uptake rates were highest for the amino acids serine, arginine and alanine, and lowest for tyrosine. DFAA concentrations within the ENCORE microatolls that received ammonium were undetectable, whereas they ranged up to 100 nM within the control microatolls. The contribution of DFAAs to the nitrogen budget of P. damicornis constituted only a small fraction of the nitrogen potentially contributed by ammonium under field conditions. Even at the highest field concentrations measured during this study, DFAAs could contribute only similar or equal to 11.3% of the nitrogen demand of P. damicornis. This contribution, however, may be an important source of nitrogen when other sources such as ammonium are scarce or during periods when high concentrations of DFAAs become sporadically available (e.g. cell breakage during fish-grazing).

Influence of field-based nutrient enrichment on the photobiology of the giant clam Tridacna maxima

Nutrients were added to 12 microatolls in One Tree Island lagoon every low tide for 13 mo to an initial concentration of 10 mu M (ammonium, N) and 2 mu M (phosphate, P). These concentrations remained above background for 2 to 3 h after addition. The addition of ammonium (N and NI-P but not P alone) significantly increased P, (gross photosynthesis) P,, (net photosynthesis) and R (respiration) per unit wet-tissue weight and cc (photosynthetic efficiency) in Tridacna maxima after 3 mo nutrient enrichment. These responses to small and transient changes in ammonium concentrations suggest that symbiotic clams are not nutrient-replete, and that even subtle changes in nutrients can have a measurable effect on photosynthesis. The same clams did not show significant differences in photosynthetic parameters 6 mo after the beginning of nutrient enrichment, suggesting that their previous responses had either been seasonal or that symbiotic clams such as T. maxima are able to adjust their photophysiology following external changes in nutrient concentrations.

Effect of disorder on quantum phase transitions in anisotropic XY spin chains in a transverse field

We present some exact results for the effect of disorder on the critical properties of an anisotropic XY spin chain in a transverse held. The continuum limit of the corresponding fermion model is taken and in various cases results in a Dirac equation with a random mass. Exact analytic techniques can then be used to evaluate the density of states and the localization length. In the presence of disorder the ferromagnetic-paramagnetic or Ising transition of the model is in the same universality class as the random transverse field Ising model solved by Fisher using a real-space renormalization-group decimation technique (RSRGDT). If there is only randomness in the anisotropy of the magnetic exchange then the anisotropy transition (from a ferromagnet in the x direction to a ferromagnet in the y direction) is also in this universality class. However, if there is randomness in the isotropic part of the exchange or in the transverse held then in a nonzero transverse field the anisotropy transition is destroyed by the disorder. We show that in the Griffiths' phase near the Ising transition that the ground-state energy has an essential singularity. The results obtained for the dynamical critical exponent, typical correlation length, and for the temperature dependence of the specific heat near the Ising transition agree with the results of the RSRODT and numerical work. [S0163-1829(99)07125-8].