Rapid emergence of subaerial landmasses and onset of a modern hydrologic cycle 2.5 billion years ago.

The history of the growth of continental crust is uncertain, and several different models that involve a gradual, decelerating, or stepwise process have been proposed1-4. Even more uncertain is the timing and the secular trend of the emergence of most landmasses above the sea (subaerial landmasses), with estimates ranging from about one billion to three billion years ago5-7. The area of emerged crust influences global climate feedbacks and the supply of nutrients to the oceans 8 , and therefore connects Earth's crustal evolution to surface environmental conditions9-11. Here we use the triple-oxygen-isotope composition of shales from all continents, spanning 3.7 billion years, to provide constraints on the emergence of continents over time. Our measurements show a stepwise total decrease of 0.08 per mille in the average triple-oxygen-isotope value of shales across the Archaean-Proterozoic boundary. We suggest that our data are best explained by a shift in the nature of water-rock interactions, from near-coastal in the Archaean era to predominantly continental in the Proterozoic, accompanied by a decrease in average surface temperatures. We propose that this shift may have coincided with the onset of a modern hydrological cycle owing to the rapid emergence of continental crust with near-modern average elevation and aerial extent roughly 2.5 billion years ago.

Clinically Significant Treatment Delay in Pediatric Scaphoid Fractures.

PURPOSE: Pediatric scaphoid fractures present to treatment in a delayed manner 8% to 29% of the time. The indications for cast immobilization in this population are not clear. The definition of a clinically important treatment delay is based only on anecdotal reports. Successful treatment with a cast may be more desirable than surgical intervention. However, it remains unclear what clinical and radiographic factors may predict success with casting. METHODS: A retrospective analysis of all scaphoid fractures treated at a single pediatric hospital was performed to identify fracture characteristics, the presence of cystic change, treatment method, and healing rate. A cut-point analysis was performed to determine the number of days of treatment delay, predictive of casting failure. Kaplan-Meier assessments were performed to determine the differences in time in cast. Characteristics of the delayed group were described and stratified by treatment success or failure. RESULTS: After review, 254 patients met the inclusion criteria. Cut-point analysis determined that a presentation delay of ≥21 days was associated with failure to unite with casting. The median time in the cast for the acute and delayed groups was not significantly different. The casting union rate of delayed fractures was less than acute fractures (75.0% vs 97.0%). CONCLUSIONS: Delayed presentation of scaphoid fractures 21 days or more after injury predicts a greater risk of casting failure; however, the union rate remains high with comparable time in cast. Cast immobilization for scaphoid fractures presenting 21 days or more after injury is a reasonable option. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognosis IV.

Loss of PTEN selectively desensitizes upstream IGF1 and insulin signaling.

Many tumors have chronically elevated activity of PI 3-kinase-dependent signaling pathways, caused largely by oncogenic mutation of PI 3-kinase itself or loss of the opposing tumor suppressor lipid phosphatase, PTEN. Several PI 3-kinase-dependent feedback mechanisms have been identified that may affect the sensitivity of upstream receptor signaling, but the events required to initiate an inhibited state have not been addressed. We show that in a variety of cell types, loss of PTEN via experimental knockdown or in tumor cell lines correlates with a block in insulin-like growth factor 1 (IGF1)/insulin signaling, without affecting the sensitivity of platelet-derived growth factor or epidermal growth factor signaling. These effects on IGF/insulin signaling include a reduction of up to five- to tenfold in IGF-stimulated PI 3-kinase activation, a failure to activate the ERK kinases and, in some cells, reduced expression of insulin receptor substrate 1, and both IGF1 and insulin receptors. These data indicate that chronically elevated PI 3-kinase-dependent signaling to the degree seen in many tumors causes a selective loss of sensitivity in IGF1/insulin signaling that could significantly reduce the selective advantage of deregulated activation of IGF1/IGF1-R signaling in tumor development.

A new solid state extractor pulser for the FNAL magnetron ion source.

A new solid state extractor pulser has been installed on the Fermi National Accelerator Laboratory (FNAL) magnetron ion source, replacing a vacuum tube style pulser that was used for over 40 years. The required ion source extraction voltage is 35 kV for injection into the radio frequency quadrupole. At this voltage, the old pulser had a rise time of over 150 µs due to the current limit of the vacuum tube. The new solid state pulsers are capable of 50 kV, 100 A peak current pulses and have a rise time of 9 µs when installed in the operational system. This paper will discuss the pulser design and operational experience to date.

Phylogeography of the deer mouse (Peromyscus maniculatus) provides a predictive framework for research on hantaviruses.

Phylogeographical partitioning of Sin Nombre and Monongahela viruses (hantaviruses) may reflect that of their primary rodent host, the deer mouse (Peromyscus maniculatus). Lack of a comprehensive assessment of phylogeographical variation of the host has precluded the possibility of predicting spatial limits of existing strains of these viruses or geographical regions where novel viral strains might emerge. The complete cytochrome b gene was sequenced for 206 deer mice collected from sites throughout North America to provide a foundation for future studies of spatial structure and evolution of this ubiquitous host. Bayesian analyses of these sequences partitioned deer mice into six largely allopatric lineages, some of which may represent unrecognized species. The geographical distributions of these lineages were probably shaped by Quaternary climatic events. Populations of mice were apparently restricted to refugia during glacial advances, where they experienced genetic divergence. Expansion of these populations, following climatic amelioration, brought genetically distinctive forms into contact. Occurrence of parallel changes in virus strains can now be explored in appropriate regions. In New Mexico, for example, near the location where Sin Nombre virus was first discovered, there are three genetically distinctive lineages of deer mice whose geographical ranges need to be delineated precisely. The phylogeography of P. maniculatus provides a framework for interpreting geographical variability, not only in hosts, but also in associated viral variants and disease transmission, and an opportunity to predict the potential geographical distribution of newly emerging viral strains.

Australia antigen in a closed adult population monitored for serum glutamic oxalacetic transaminase.

A study of the presence of Australia antigen (Au/SH) was conducted over a period of 21 weeks among volunteer plasma donors living in a prison and being monitored for serum glutamic oxalacetic transaminase (SGOT). A good correlation was observed between the level of SGOT and presence of Au/SH, the latter being present in 33% of donors with SGOT values higher than 101 Karmen units and in 12% of those with SGOT values of 41 to 100 units. Furthermore, none of the 87 donors with all SGOT values below 40 was found positive for Au/SH. It should be noted, however, that single specimens only were tested from 72 of the 87 individuals. Au/SH was detected with equivalent efficiency by both agar gel precipitation and complement fixation procedures. Implications of these findings in the prognostication of hepatitis carrier state are discussed.

Unusual eyelid tumors with sebaceous differentiation in the Muir-Torre syndrome. Rapid clinical regrowth and frank squamous transformation after biopsy.

An unusual eyelid tumor with sebaceous differentiation developed in two 70-year-old men and each had an earlier history of one or more colonic carcinomas--the so-called Muir-Torre syndrome. These eyelid tumors were both behaviorally and histopathologically different from previously documented cutaneous neoplasms in this syndrome. In the first case, a sebaceous adenoma took multifocal origin from the epidermis and exhibited an interanastomosing retiform growth pattern in the underlying dermis; the lesion rapidly recurred as a keratoacanthoma after subtotal excision. In the second case, a conjunctival tumor with features of a poorly differentiated squamous cell carcinoma manifested focal evidence of sebaceous differentiation. Again, after an incisional biopsy, the latter tumor rapidly regrew and transformed into a well-differentiated squamous cell carcinoma with massive central necrosis. Although sebaceous carcinoma of the eyelids does not appear to presage the Muir-Torre syndrome, any benign sebaceous or transitional squamo-sebaceous neoplasm should be considered a possible manifestation of this syndrome. Both clear-cut benign and transitional sebaceous neoplasms should also be recognized as having the potential to undergo an ominous clinical regrowth upon subtotal excision and a complete squamous transformation.