Enhanced glacial discharge from the eastern Antarctic Peninsula since the 1700s associated with a positive Southern Annular Mode.

The Antarctic Peninsula Ice Sheet is currently experiencing sustained and accelerating loss of ice. Determining when these changes were initiated and identifying the main drivers is hampered by the short instrumental record (1992 to present). Here we present a 6,250 year record of glacial discharge based on the oxygen isotope composition of diatoms (δ18Odiatom) from a marine core located at the north-eastern tip of the Antarctic Peninsula. We find that glacial discharge - sourced primarily from ice shelf and iceberg melting along the eastern Antarctic Peninsula - remained largely stable between ~6,250 to 1,620 cal. yr BP, with a slight increase in variability until ~720 cal. yr. BP. An increasing trend in glacial discharge occurs after 550 cal. yr BP (A.D. 1400), reaching levels unprecedented during the past 6,250 years after 244 cal. yr BP (A.D. 1706). A marked acceleration in the rate of glacial discharge is also observed in the early part of twentieth century (after A.D. 1912). Enhanced glacial discharge, particularly after the 1700s is linked to a positive Southern Annular Mode (SAM). We argue that a positive SAM drove stronger westerly winds, atmospheric warming and surface ablation on the eastern Antarctic Peninsula whilst simultaneously entraining more warm water into the Weddell Gyre, potentially increasing melting on the undersides of ice shelves. A possible implication of our data is that ice shelves in this region have been thinning for at least ~300 years, potentially predisposing them to collapse under intensified anthropogenic warming.

Multi-isotope analysis reveals that feasts in the Stonehenge environs and across Wessex drew people and animals from throughout Britain.

The great henge complexes of southern Britain are iconic monuments of the third millennium BCE, representing great feats of engineering and labor mobilization that hosted feasting events on a previously unparalleled scale. The scale of movement and the catchments that the complexes served, however, have thus far eluded understanding. Presenting the largest five-isotope system archeological dataset (87Sr/86Sr, δ34S, δ18O, δ13C, and δ15N) yet fully published, we analyze 131 pigs, the prime feasting animals, from four Late Neolithic (approximately 2800 to 2400 BCE) complexes to explore the networks that the feasts served. Because archeological evidence excludes continental contact, sources are considered only in the context of the British Isles. This analysis reveals wide-ranging origins across Britain, with few pigs raised locally. This finding demonstrates great investment of effort in transporting pigs raised elsewhere over vast distances to supply feasts and evidences the very first phase of pan-British connectivity.

Effects of methylphenidate on reward strength in boys with attention-deficit hyperactivity disorder.

OBJECTIVE: To test the hypothesis that methylphenidate reduces thresholds for reward in children with attention-deficit hyperactivity disorder (ADHD). METHOD: A double-blind crossover design was used in which 16 ADHD boys, aged 8 to 13 years, received methylphenidate on one testing occasion and placebo on another. On each occasion, subjects performed a task that required progressively greater numbers of button presses to earn a fixed monetary payoff. RESULTS: The "breaking point" above which the hyperactive child was unwilling to continue with the task was significantly higher during drug than placebo trials. CONCLUSIONS: The results support an assumption that underlies the reward system dysfunction hypothesis of ADHD, and they suggest that reward mechanisms may underlie the therapeutic effects of stimulants observed across a wide range of tasks and settings.

Progressive hemifacial atrophy (Parry-Romberg disease).

Hemifacial atrophy (Parry-Romberg syndrome) is characterized by slowly progressive atrophy of one side of the face, primarily involving the subcutaneous tissue and fat. The onset is usually in the first two decades. Ophthalmic involvement is common; the most frequent abnormality is progressive endophthalmos with subsequent changes in the palpebral fissure. Pupillary disturbances, heterochromia, uveitis, and restrictive strabismus have also been frequently reported. We describe six cases that manifest a wide spectrum of ocular and systemic findings. They are noteworthy in that all exhibit pigmentary disturbances of the ocular fundus, a finding rarely reported. Another unusual ocular manifestation in one patient was an acquired partial third nerve palsy on the unaffected side.

Ultraviolet-absorbing pseudophakos: an efficacy study.

The use of intraocular lenses (IOLs) to replace cataractous lenses has raised question of possible retinal damage due to exposure to ultraviolet (UV) radiation. Three groups of cynomolgus monkeys underwent cataract operations and either received normal UV-transparent IOLS or UV-opaque IOLs, or were left aphakic. All eyes were later exposed to UV light for varying periods of time. Exposure to UV light produced severe retinal lesions. In aphakic eyes and those with normal IOLs lengthy exposure to low levels of UV light produced lesions similar to those seen after brief, very intense UV radiation. Eyes with UV-opaque IOLs displayed no such lesions. Our results indicate that clinicians should consider the use of UV-opaque IOLs.

Netilmicin: new aminoglycoside effective against bacterial endophthalmitis.

Bacterial endophthalmitis is difficult to treat because antibiotics administered systemically, subconjuctivally or topically cannot be delivered in bactericidal amounts to the infected tissues. Netilmicin, a new aminoglycoside, is active against Pseudomonas aeruginosa, Staphylococcus and most Enterobacteriaceae, including Escherichia coll, Klebsiella and Enterobacter, that have been resistant to other aminoglycosides. In rabbits an intravitreal injection of 250 mu g/0.1 ml rapidly provided a bactericidal concentration (greater than 10 mu g/ml) in the vitreous, and this level was maintained for 100 hours. This dose was not toxic to ocular tissues, unlike higher doses (1000 to 2000 mu g). Intravenous, subconjunctival and topical administration yielded only low concentrations of the drug in the vitreous, although subconjunctival injection yield significant concentrations in the aqueous for 4 hours. Experimentally induced Staphylococcus aureus endophthalmitis was quickly eradicated by a single intravitreal dose of netilmicin without detectable sequelae in 9 to 10 eyes studied. A solution of netilmicin infused during vitrectomy and lensectomy prevented infection.

The generalization effects of parent training across stimulus settings.

Five parents of nonverbal children were trained in two home settings to modify antecedents and consequences to their children's vocalizations. Generalization effects of the parent training on both the parent's and children's behaviors under different stimulus conditions were investigated using multiple-baseline designs. Increases in parent prompting and reinforcing their children's vocalizations generalized only minimally to a new setting in the home where parent training had not occurred. Child increases in vocalizations produced by the parents in the training settings did generalize to this new setting in the home. There was minimal generalization of child vocalizations to a free-play setting at school. In a formal speech session conducted by a behavior specialist at school, only one child showed definite increases in acquisition rate as a function of the parents starting to train the sound at home.

Training elementary aged peer behavior managers to control small group programmed mathematics.

The effects of a training procedure and two maintenance contingencies on consequence-dispensing behavior were investigated. Four peer behavior managers were trained to supervise small groups of subjects (four to six per group) working in programmed math materials and were compared with a teacher skilled in the use of social and point reinforcement and response cost. Manager training was differentially effective in accelerating manager's rates of appropriate social and point dispensing. Having manager reinforcement contingent upon manager consequence-dispensing resulted in moderately higher rates of appropriate social and point dispensing for three of four subjects than did having manager reinforcement contingent upon group study behavior. Two managers exposed to the group performance contingency before the manager performance contingency increased inappropriate social and point-dispensing behaviors to pretraining baseline levels. Subsequent change to the manager performance contingency was effective in reducing the inappropriate dispensing behavior of only one of the two managers.

Effects of contingency contracting on study rate and test performance.

A contingency contracting program designed to increase study rate and subsequent test performance was implemented with a group of undergraduate psychology students. The function of the contingency contracting program in producing increased study rate was evaluated by individual experiments with each student in an experimental contracting group. The overall effect of the program on test performance was assessed by comparing the final scores for the course earned by the experimental group with those earned by two matched control groups. A reversal procedure established that contingency contracting did significantly increase the study rate of students of a wide range of ability. However, it was selectively effective in improving the test performance of below-average students only. Study rate gains in contracted courses did not generalize to noncontracted courses. Self-recording of study time in the absence of scheduled differential consequences did not improve test performance. Study rate under no-consequence conditions varied with test schedule. For both consequence and no-consequence groups, the correlation between study time and final score for the course was only moderate.

Modification of a child's problem behaviors in the home with the mother as therapist.

Differential consequences were used to increase obedience and decrease aggressive behavior in a four-and-one-half year old boy. Treatment was conducted in the child's home by his mother.