D-erythro-neopterin biosynthesis in the methanogenic archaea Methanococcus thermophila and Methanobacterium thermoautotrophicum deltaH

The steps in the biosynthetic transformation of GTP to 7,8-dihydro-D-erythro-neopterin (H2neopterin), the precursor to the modified folates found in the methanogenic archaea, has been elucidated for the first time in two members of the domain Archaea. In Methanococcus thermophila and Methanobacterium thermoautotrophicum deltaH, it has been demonstrated that H2neopterin 2':3'-cyclic phosphate is an intermediate in this conversion. In addition, the formation of the pterin ring of the H2neopterin 2':3'-cyclic phosphate is catalyzed not by a single enzyme, as is known to occur with GTP cyclohydrolase I in the Eucarya and Bacteria, but rather by two or more enzymes. A 2,4,5-triamino-4(3H)-pyrimidinone-containing molecule, most likely 2,5-diamino-6-ribosylamino-4(3H)-pyrimidinone 5'-triphosphate, has been identified as an intermediate in the formation of the H2neopterin 2':3'-cyclic phosphate. Synthetic H2neopterin 2':3'-cyclic phosphate was found to be readily hydrolyzed by cell extracts of M. thermophila via the H2neopterin 3'-phosphate to H2neopterin, a known precursor to the pterin portion of methanopterin.     

Determination of plasma concentrations of propofol associated with 50% reduction in postoperative nausea

BACKGROUND: Subhypnotic doses of propofol possess direct antiemetic properties. The authors sought to determine the plasma concentration of propofol needed to effectively manage postoperative nausea and vomiting. METHODS: Patients aged 18-70 yr who were classified as American Society of Anesthesiologists physical status 1 or 2 and had surgery during general anesthesia were approached for the study. Only patients who had nausea (verbal rating score > 5 on a 0- to 10-point scale), retching, or vomiting in the postanesthetic care unit participated. Propofol was administered to these patients to achieve target plasma concentrations of 100, 200, 400, and 800 ng/ml using a computer-assisted continuous infusion device. Target concentrations were increased every 15 min until patients described at least a 50% reduction in symptoms on the verbal rating score. An arterial blood sample was obtained at each step. The measured plasma propofol concentrations were used to analyze data. Blood pressure, heart and respiratory rates, arterial blood saturation, sedation score, and overall satisfaction with treatment were recorded. RESULTS: Of the 89 patients who consented to the study, 15 patients met entry criteria and were enrolled. Five of these patients also had retching or vomiting when they entered the study. Fourteen patients responded successfully to treatment. One patient did not achieve the required response at plasma concentrations of 830 ng/ml. Hence the success rate for the treatment of postoperative nausea and vomiting was 93%. Among patients who responded, the median plasma concentration associated with an antiemetic response was 343 ng/ml. There was no difference in sedation scores from baseline and no episodes of desaturation. Hemodynamic parameters were stable during the study. CONCLUSIONS: Propofol is generally efficacious in treating postoperative nausea and vomiting at plasma concentrations that do not produce increased sedation. Simulations indicate that to achieve antiemetic plasma propofol concentrations of 343 ng/ml, a bolus dose of 10 mg followed by an infusion of approximately 10 microg x kg(-1) x min(-1) are necessary.     

The tyranny of distance prevails: HTTP protocol latency and returns to fast fibre internet access network deployment in remote economies

Public policies to deploy enhanced local broadband access infrastructure in locations physically very far removed from the firms and customers with whom they transact are frequently justified by claims of increased competitiveness arising from the elimination of the ‘tyrannies of distance’. Yet relative distance-based disadvantages remain in respect of time-dependent applications and those hosted on distant infrastructures or requiring data sourced from distant locations. Trading off the effects of faster local access and latency on the time taken to load a Web page based on the HTTP Web protocol, we demonstrate that the increasing returns to distance rapidly overcome the effect of faster local access bandwidth as the distance the data must travel increases. We conclude that claims that investment in ultra-fast local broadband access will unconditionally facilitate a step-change in national economic performance are without foundation. In the absence of some compelling underlying competitive advantages, the ‘transformational’ economic benefits will be local rather than international in nature. At best, government investment in nationwide fast fibre networks is a defensive strategy that enables ongoing participation in the international economy, but at relatively higher costs than those faced by larger economies in closer proximity to end markets.     

The nature of acicular ferrite in HSLA steel weld metals

In this paper, the nature of the fine interlocking acicular ferrite microstructure in HSLA steel weld metals is investigated. The results strongly suggest the acicular ferrite is comprised of intragranularly nucleated Widmanstätten ferrite. Further, it is shown that the active nucleation sites for this ferritic product are weld metal inclusions. Sympathetic nucleation then takes place which leads eventually to the fine, interlocking microstructure which is a characteristic of acicular ferrite.     

Full Field Temperature Measurement of Specular Wafers During Rapid Thermal Processing

Many of the processes involved in the creation of semiconductor devices involve high-temperature processing of silicon wafers. The benefits of reduced thermal budget and faster cycle time make rapid thermal processing (RTP) a possible key technology for semiconductor manufacturing. However, the problem of nonuniform wafer temperature has prevented it from further spread among the industry. The first step in developing controls to maintain a uniform wafer temperature is accurate temperature measurement during processing. In this paper, a system was developed to exploit the specular reflectivity of silicon wafers and obtain a measurement of the wafer temperature profile. The spectral reflectivity is determined by measuring the intensity of an incident beam and the beam reflected from the wafer surface. With this measured reflectivity value the spectral-directional wafer emissivity was determined using Kirchhoff's law. The obtained emissivity then was used to calculate the wafer temperature profile from an image obtained with an infrared camera. An experimental study of the transmittance of an undoped silicon calibration wafer at an elevated temperature is also discussed     

Sr2−XLaXMgMoO6 and Sr2−XLaXMgNbO6 for Use as Sulfur‐Tolerant Anodes Without a Buffer Layer

The objective of this effort is to synthesize and characterize a series of lanthanum‐(La) doped Sr₂MgMoO₆ (SMMO) and La‐doped Sr₂MgNbO₆ (SMNO) anode materials which can be used in combination with lanthanum‐containing electrolytes to mitigate the effects of lanthanum poisoning in solid oxide fuel cells (SOFCs). Currently, an La_0.4Ce_0.6O_1.8 (LDC) buffer layer is used with many perovskite‐based anode materials to prevent La diffusion into the anode from the La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 (LSGM) electrolyte which can create a resistive La species that impedes electrochemical performance. The LDC buffer layer, with diminished electronic conductivity, adds an extra level of complexity in the SOFC manufacturing process. Further, this extraneous layer presents an added experimental challenge when assessing anode material performance. Overall electrochemical performance could be improved if the resistive buffer layer could be removed, thereby allowing the anode material to have direct contact with the electrolyte. To accomplish this, a new class of anode materials was synthesized with the goal of balancing “La” chemical potential between these neighboring materials. La‐doped SMMO and SMNO were prepared and studied. It was hypothesized that by incorporating La into the anode, the gradient of chemical activity between the anode and electrolyte would decrease, which would prevent La diffusion. These anode materials were synthesized via a sol–gel methodology and characterized with X‐ray diffraction to assess phase purity. The conductivity of the materials was analyzed in the presence of both H₂ and 100 ppm H₂S/H₂ to determine the stability and performance of these materials during device operation. The stability experiments demonstrated that 40% La‐doped SMNO is stable in all pertinent environments while not reacting with the LSGM electrolyte.     

A 2-methyleneoxetane analog of orlistat demonstrating inhibition of porcine pancreatic lipase

The 2-methyleneoxetane analog 2 of orlistat (OLS, 1) has been synthesized and tested against porcine pancreatic lipase (PPL). Despite the loss of the carbonyl group, a potential site for hydrogen bonding interaction with the enzyme and the key element in the acylation by OLS, 2 has activity comparable to 1.