Guest Editors' Introduction: Overview of Sensor Networks

Wireless sensor networks could advance many scientific pursuits while providing a vehicle for enhancing various forms of productivity, including manufacturing, agriculture, construction, and transportation.     

Extending IP to Low-Power, Wireless Personal Area Networks

Extending IP to low-power, wireless personal area networks (LoWPANs) was once considered impractical because these networks are highly constrained and must operate unattended for multiyear lifetimes on modest batteries. Many vendors embraced proprietary protocols, assuming that IP was too resource-intensive to be scaled down to operate on the microcontrollers and low-power wireless links used in LoWPAN settings. However, 6LoWPAN radically alters the calculation by introducing an adaptation layer that enables efficient IPv6 communication over IEEE 802.15.4 LoWPAN links.     

Virtual network transport protocols for Myrinet

Bringing direct and protected network multiprogramming into mainstream cluster computing requires innovations in three key areas: application programming interfaces, network virtualization systems, and lightweight communication protocols for high-speed interconnects. The AM-II API extends traditional active messages with support for client-server computing and facilitates the construction of parallel clients and distributed servers. Our virtual network segment driver enables a large number of arbitrary sequential and parallel applications to access network interface resources directly in a concurrent but fully protected manner. The NIC-to-NIC communication protocols provide reliable and at-most-once message delivery between communication endpoints. The NIC-to-NIC protocols perform well as the number of endpoints and the number of hosts in the cluster are scaled. The flexibility afforded by the underlying protocols enables a diverse set of timely research efforts. Other Berkeley researchers are actively using this system to investigate implicit techniques for the coscheduling of communicating processes, an essential part of high-performance communications in multiprogrammed clusters of uni- and multiprocessor servers. Other researchers are extending the active message protocols described here for clusters of symmetric multiprocessors, using so-called multiprotocol techniques and multiple network interfaces per machine     

Cost of extracorporeal life support in pediatric patients with acute respiratory failure

OBJECTIVES: To determine the impact of extracorporeal life support (ECLS) on mortality in pediatric patients with acute hypoxemic respiratory failure (AHRF) at our institution; and to calculate the hospital charges associated with the use of ECLS. DESIGN: Retrospective review of medical records and hospital charges. SETTING: Pediatric intensive care unit (ICU) of a university-affiliated children's hospital. PATIENTS: Twenty patients admitted to the pediatric ICU between 1991 and 1995 for AHRF who received ECLS as a part of their hospital course. INTERVENTIONS: Predicted mortality was calculated using the Pediatric Respiratory Failure score and was compared with survival at the time of hospital discharge. Hospital charges were used as a proxy for resource utilization. Cost-per-life-year-saved calculations were performed based on a normal life expectancy for survivors. MEASUREMENTS AND MAIN RESULTS: Twenty patients were identified. The median age was 4.83 yrs. The median duration of ECLS was 9 days, with 19.5 days in the pediatric ICU and 23.5 days for the entire hospital length of stay. The observed mortality rate for these patients was 20%. Median predicted mortality rate based on the Pediatric Respiratory Failure score calculation was 83%. The hospital charges incurred by these patients was a median of $199,096. Based on a normal life expectancy for survivors, this results in a cost of $4,190/life-year. CONCLUSIONS: ECLS for the pediatric patient with AHRF is done at a considerable cost. However, ECLS affects survival favorably, and compares favorably when considering cost/life-year calculations. The data presented in this study may serve as a benchmark for comparison with newer therapies (i.e., liquid ventilation, nitric oxide). These data also provide a framework for cost-based analyses at other ECLS institutions.     

The Investigation of the Behavior of Microorganisms by Computerized Television

Instrumentation is described which permits, along with simultaneous subjective observation, the rapid recording and quantification of the overt behavior of motile microorganisms under varying conditions. From a chain of standard commercially available units (with the exception of a single especially designed one) there has emerged a totality which provides unique advantages to the student of overt behavior. It consists of a primary optical system through which the organisms are televised, a standard video tape recorder, a unit which we have christened the ``bugwatcher' that processes the video signal from the tape for quantification of data by a computer, and finally, a digital computer.     

Discovery of Adamantyl Ethanone Derivatives as Potent 11β‐Hydroxysteroid Dehydrogenase Type 1 (11β‐HSD1) Inhibitors

11β‐Hydroxysteroid dehydrogenases (11β‐HSDs) are key enzymes regulating the pre‐receptor metabolism of glucocorticoid hormones. The modulation of 11β‐HSD type 1 activity with selective inhibitors has beneficial effects on various conditions including insulin resistance, dyslipidemia and obesity. Inhibition of tissue‐specific glucocorticoid action by regulating 11β‐HSD1 constitutes a promising treatment for metabolic and cardiovascular diseases. A series of novel adamantyl ethanone compounds was identified as potent inhibitors of human 11β‐HSD1. The most active compounds identified ( 52 , 62 , 72 , 92 , 103 and 104 ) display potent inhibition of 11β‐HSD1 with IC₅₀ values in the 50–70 nM range. Compound 72 also proved to be metabolically stable when incubated with human liver microsomes. Furthermore, compound 72 showed very weak inhibitory activity for human cytochrome P450 enzymes and is therefore a candidate for in vivo studies. Comparison of the publicly available X‐ray crystal structures of human 11β‐HSD1 led to docking studies of the potent compounds, revealing how these molecules may interact with the enzyme and cofactor.     

Energy impact of modifications of a river freight transport system: The upper Mississippi

As an example of analysis of the energy impact of enlarging a river freight-transport system, we consider Locks and Dam 26 near Alton, Illinois, which is the principal bottleneck of the upper Mississippi River. A simple queueing theory model is developed to predict the average delay time prior to processing through the locks as a function of traffic growth rates. Estimates of the energy intensity of freight transport on the upper Mississippi are made from a theoretical model and compared with values published in the literature. The energy impact of the replacement of Locks and Dam 26 is assessed by combining the results of the traffic-flow and energy-intensity models. For a traffic growth rate of 2.5%/yr, the cumulative energy savings (during a 40 yr operating life) of replacing the current facility is nearly 20 × 10¹² Btu. The economic value of the energy savings is 40–85% of the cost differential between repairing the current installation with no increase in capacity and the construction of an entirely new facility with a 100% increase in main locking chamber size.     

Molecular genetic analysis of plastocyanin biosynthesis in Chlamydomonas reinhardtii

Five plastocyanin-deficient mutants were identified from a population of UV-mutagenized Chlamydomonas reinhardtii cells. Genetic complementation experiments indicated that four mutants represented alleles at the PCY1 locus (pcy1-2, pcy1-3, pcy1-4, and pcy1-5). Sequence analysis confirmed that two strains, pcy1-2 and pcy1-3, carry a frameshift (-1) and a nonsense mutation, respectively, while strains pcy1-4 and pcy1-5 synthesize an extended protein as a result of read-through mutations at the stop codon. The C-terminal extension does not affect synthesis or processing of the pre-proteins, but the polypeptides are rapidly degraded after the second (lumenal) processing event. The frameshift mutation in pcy1-2 results in loss of Pcy1 mRNA, as noted previously for strain ac208 (pcy1-1), but the abundance of Pcy1 mRNA in strain pcy1-3, which carries a nonsense mutation at codon 26, is unaffected relative to wild-type cells. The decreased abundance of frameshifted Pcy1 mRNA is attributed to increased degradation rather than decreased synthesis, since the mRNAs can be stabilized by treatment of cells with cycloheximide or anisomycin. The fifth strain has a wild-type plastocyanin-encoding gene, but the strain accumulates apoplastocyanin at the expense of holoplastocyanin. We suggest that the mutation identifies a new locus (PCY2) whose function is required for normal holoplastocyanin accumulation. Like ac208 (pcy1-1), several of the new mutants were suppressed spontaneously owing to accumulation of cytochrome c6 (a functional substitute for plastocyanin). The suppressor mutation(s) displayed Mendelian inheritance and segregated independently from the PCY1 locus, which confirms that regulation of Cyc6 expression is not tightly linked to plastocyanin function.