Analysis of the effect of transverse modes on free-space optical interconnect performance

Vertical-cavity surface-emitting lasers (VCSELs) and microlenses can be used to implement free space optical interconnects (FSOIs) which do not suffer from the bandwidth limitations inherent in metallic interconnects. A comprehensive link equation describing the effects of both optical and electrical noise is introduced. We have evaluated FSOI performance by examining the following metrics: the space-bandwidth product (SBP), describing the density of channels and aggregate bandwidth that can be achieved, and the carrier-to-noise ratio (CNR), which represents the relative strength of the carrier signal. The mode expansion method (MEM) was used to account for the primary cause of optical noise: laser beam diffraction. While the literature commonly assumes an ideal single-mode laser beam, we consider the experimentally determined multimodal structure of a VCSEL beam in our calculations. It was found that maximum achievable interconnect length and density for a given CNR was significantly reduced when the higher order transverse modes were present in Simulations. However, the Simulations demonstrate that free-space optical interconnects are still a suitable solution for the communications bottleneck, despite the adverse effects introduced by transverse modes.

Effect of information provision on trauma symptoms following therapeutic writing

Recent studies in the area of psychological debriefing (PD) have reported adverse effects. This study examined one possible explanation for such effects, that of sensitisation to the possibility of pathology. Subjects were 161 psychology students (female, n = 121; male, n = 40) who had experienced trauma but received no previous treatment. Subjects either received an explanation (explanation group) or received no explanation at all (no explanation group) about trauma reactions prior to undertaking a therapeutic writing protocol. The hypothesis of increased morbidity where the possibility of pathology was made explicit was not supported. At 2 months, the explanation group had a greater reduction on Impact of Events Scale Revised JES-R) total scores, F(1, 151) = 3.98, p = .048, and on the General Health Questionnaire - 28 (GHQ-28) Anxiety and Insomnia subscale, F(1, 151) = 9.84, p = .002, and total score F(1, 150) 5.05, p = .026. High-avoidance copers in particular appeared to benefit from information provision, F(1, 148) = 4.2 6, p = .044. Results suggest that adverse findings associated with PD may not be due to information sensitising of participants to pathology and that the provision of information to trauma survivors appears to be a useful strategy. Recommendations were made regarding the management of those exposed to trauma and for future research.

The effect of organic mulch amendments on the physical and chemical properties and revegetation success of a saline-sodic minespoil from central Queensland, Australia

Saline-sodic clay minespoil materials excavated during open-cut coal mining in central Queensland, Australia, pose significant challenges for revegetation, particularly where suitable topsoil capping is not available. We examined the ability of sawdust or straw mulch amendments to ameliorate the adverse properties of these minespoils and improve the success of revegetation efforts. In laboratory studies, mulch application improved infiltration, increased soil moisture retention and reduced surface crust strength. In the field, mulches incorporated to a depth of 0.15 m at application rates of at least 20 t/ha straw or 80 t/ha sawdust were needed to mitigate against capillary rise of salts during drying cycles and support satisfactory vegetation cover. Further research is needed to determine whether improvements are maintained beyond the 4-year trial period reported here.