Anthropogenic change decouples a freshwater predator's density feedback.

Intraspecific interactions within predator populations can affect predator-prey dynamics and community structure, highlighting the need to better understand how these interactions respond to anthropogenic change. To this end, we used a half-century (1969-2018) of abundance and size-at-age data from Lake Erie's walleye (Sander vitreus) population to determine how anthropogenic alterations have influenced intraspecific interactions. Before the 1980s, the length-at-age of younger walleye (ages 1 and 2) negatively correlated with older (age 3 +) walleye abundance, signaling a 'density feedback' in which intraspecific competition limited growth. However, after the early 1980s this signal of intraspecific competition disappeared. This decoupling of the density feedback was related to multiple anthropogenic changes, including a larger walleye population resulting from better fisheries management, planned nutrient reductions to improve water quality and transparency, warmer water temperatures, and the proliferation of a non-native fish with novel traits (white perch, Morone americana). We argue that these changes may have reduced competitive interactions by reducing the spatial overlap between older and younger walleye and by introducing novel prey. Our findings illustrate the potential for anthropogenic change to diminish density dependent intraspecific interactions within top predator populations, which has important ramifications for predicting predator dynamics and managing natural resources.

Fatal inhalation injury following an industrial accident involving acetic anhydride.

A 22-year-old man sustained 35 per cent burns to his skin and an inhalation injury in an industrial accident involving acetic anhydride. Although the skin burns healed following irrigation and conservative treatment, the inhalation injury proved fatal.

The sliding fasciocutaneous flap.

A sliding fasciocutaneous flap on the medial side of the lower third of the leg is described. Its application in the management of skin defects in this area is illustrated.

Group amplification in schools for the hearing impaired.

In the present field study, ambient noise levels and the status of group FM-wireless amplification systems were examined in 19 classrooms for the hearing impaired. Classroom noise was judged to be unacceptably high thus justifying the need for group amplification devices. Physical inspection of the group systems revealed defects in approximately one-half of the 28 teacher and 89 student amplification units. The electroacoustic measurements showed wide variability in performance among systems. There also appeared to be no systematic relationship between the degree of hearing loss of the children and the amount of unit gain being employed by each specific amplification system.

Electroacoustic performance characteristics of FM auditory trainers.

This study investigated the electroacoustic performance characteristics of FM auditory trainers. Experiment one was designed to answer two interrelated questions. First, what are the differences in the electroacoustic performance of FM auditory trainers between the FM and EM modes? Second, is the method for evaluating electroacoustic performance of hearing aids also appropriate for assessing the response characteristics of FM auditory trainers? The purpose of the second experiment was to assess the effect that taper of the volume control dial had on performance of these trainers. The study found that, with certain cautions, the ANSI S3.22-1976 procedures for assessing a hearing aid could be applied to the measurement of FM trainers. There were performance differences, however, between the auditory trainers when set to the FM and EM transmission modes. Thus, the electroacoustic assessment of FM units in both the EM and FM modes of operation is needed to assess their performance fully.

Primary free-flap cover of open tibial fractures.

Seventeen consecutive patients with Grade IIIB open tibial fractures had definitive treatment of both the fracture and soft tissues performed within 72 h of injury. Free tissue transfer was used for cover in each case. There were no cases of deep infection. Flap survival was 100 per cent. The mean time to fracture healing was 10 months, and mean time to walking unaided was 12 months. The average length of stay in hospital was 82 days. The findings suggest that immediate radical debridement followed by adequate soft tissue cover is a safe and effective method for treating these severe injuries.

Long-term behaviour of the free vascularised fibula following reconstruction of large bony defects.

Thirty-two free vascularised fibula grafts performed at our unit have been assessed retrospectively with respect to success, bony union and percentage graft hypertrophy. Between 1981 and 1998, there were 21 males and 11 females (aged 8-61 years) with follow-up of 5 months to 14.6 years. The mean bony defect bridged was 12.0 cm (standard deviation 4.8; range 5.0-21.0 cm). Bony union and hypertrophy were assessed radiographically. Time to bony union was compared using the log-rank, Wilcoxon or likelihood ratio tests. Kaplan-Meier survival curves were constructed. Hypertrophy was compared with Wilcoxon's rank sum test.Three flaps failed. Seventy-four percent of patients healed primarily at a median time of 4.75 months; five patients required further surgery to heal by 18 months (interquartile range 14-20 months). Complication rate and donor site morbidity were low. The stress fracture rate was 21%. Ninety percent of patients regained a functional limb by 12 months.Hypertrophy was measured in 22 patients and ranged from 0 to 316% (median 71%; interquartile range 10-145%). Median hypertrophy in the lower limb was 76.5% (interquartile range 26.5-165%) compared to 33.5% in the upper limb (0-88%); p=0.16. Median hypertrophy in trauma cases was 80% (interquartile range 10-167%) compared to 70% in tumour cases (33-105%); p=0.62.Our findings confirm that the fibula responds physiologically to biomechanical loading. Our results compare well with other series and alternative reconstructive modalities. We conclude that the free fibula flap can provide excellent results in the salvage of limbs with large bony defects.

The use of near-infrared spectroscopy for assessing flap viability during reconstructive surgery.

The ability to assess viability of tissues by monitoring changes in oxygenation and perfusion during harvesting and following transfer of free and pedicled flaps is potentially important in reconstructive surgery. Rapid detection of a critical change in tissue oxygenation could enable earlier and more successful surgical intervention when such problems arise. In this study near infra-red spectroscopy (NIRS) was used to assess changes in tissue oxygenation, haemoglobin oxygenation and blood volume in a porcine prefabricated myocutaneous flap model in response to pedicle manipulations. As far as we are aware this is the first usage of a NIRS instrument to assess changes in oxygenation in a flap model which closely simulates the clinical situation. A myocutaneous flap was raised (n = 9 pigs), tubed and the flap circulation allowed to readjust for periods between 7 and 9 days. The pedicle vessels were then subjected to arterial (n = 9), venous (n = 12) and total occlusion (n = 6). Repeatable and reproducible patterns of change were measured in each case. Comparison of mean values indicated that the differences between arterial and venous, and venous and total occlusions were significant for all NIRS parameters. The monitor was easily able to detect two additional features: (i) the presence of venous congestion indicated by raised levels of deoxygenated haemoglobin and an increase in blood volume; and (ii) the presence and magnitude of reactive hyperaemia. In two flaps release of arterial or total occlusion did not result in the expected reactive hyperaemia associated with an increase in blood volume (oxygenated haemoglobin) suggestive of possible damage to the vascular bed. NIRS proved able to detect and distinguish between microcirculatory changes occurring as a result of arterial, venous or total vascular occlusion. We believe that NIRS provides a sensitive and reliable postoperative monitor of tissue viability following transfer of free and pedicled flaps. It can accurately identify different types of problems with the pedicle vessels. In addition its predictive capabilities would allow assessment of flaps buried deep to the skin. This monitor is excellent for surgical and intensive care unit monitoring since it is unaffected by light, portable and is extremely easy to use.