Maxwell currents beneath thunderstorms

Analyses of single station measurements of the Maxwell current density (Jm) made under Florida thunderstorms during the summer of 1981 have been completed. The results of these analyses indicate that: (1) Jm is usually dominated by the displacement current component when the electric field is close to zero; (2) Jm is steady with time in the intervals between lightning flashes; (3) Jm is not altered significantly by lightning; and (4) the average value of Jm changes slowly and over time scales that are comparable to those required for storm development. Maps have also been derived of the surface Maxwell current density for a number of the Florida TRIP (76-78) storms using field mill data to estimate Jm from the displacement current density. Studies show that these maps provide a good indication of the location and relative intensity of the storm current generators, and area-integrations of the current contours provide estimates of the total storm currents

Lithium Lens Interlocks

The lithium lens in the antiproton source target vault is protected by an interlock system, which is located in relay racks R5 and R6 near the southwest corner of the Target Hall (building APO). The interlock system consists of crates of commercial signal conditioner and alarm modules built by Acromag, Inc and interlock Master Modules built by Fermilab: Twenty analog signals from the lens/transformer, power supply, and cooling water system are buffered with signal conditioners (amplifiers), which are located in creates R5C and R5E. The signals and conditioner assignments are listed in Table 1. Interconnection details are shown in Figure 1. Thermocouple signals come into the conditioners directly from the vault or water system via 12-pair multiconductor thermocouple extension cables. All other signals pass through a master connection panel on the east end of rack R6. Water flow signals are AC voltages which must be converted by electronics in crate D2B to DC voltages before entering their signal conditioners. Each conditioner drives two parallel outputs. One output goes to a Multiplexed Analog to Digital Converter (MADC 25), which is located in R5D. This voltage output is read by the accelerator control network (ACNET) and can be displayed at any control console on parameter page P46. The other voltage output is connected to an alarm module. Thirteen analog signals are processed by alarm modules, which are located in crates R6B and R6C. Alarm connection details are shown in Figure 2. Each alarm module contains two DPDT relays, one for an upper limit and one for a lower limit. The relays are latching, so that once an input has passed outside a limit, that limit relay remains in the tripped condition until an operator issues a reset pulse. The reset may be generated locally with a pushbutton on the appropriate interlock master module or remotely from controls parameter page P46 via ACNET. Alarm settings are summarized in engineering units in Table 1, and actual comparitor voltage settings are listed in Figure 2. Each alarm crate contains 10 module slots and is wired as shown in Figure 3, except for the water conductivity slot, which is wired to a separate interlock chain output. Normally open contacts are used for interlock chains, while normally closed contacts provide status bits. The interlock chain outputs are connected to Interlock Master Modules located in D5C. Status bits are read into ACNET through a multiplexer in R4A, and can be displayed on parameter page S40. Any alarm slot may be bypassed by inserting a 'dummy' printed circuit card in place of a module. Each interlock master module sums 5 inputs and provides 3 reed relay contact closure outputs. A circuit schematic is shown in Figure 4. Input 1 requires +5 volts, and directly energizes an interlock chain relay. Input 2 and 3 require TTL logic levels, and inputs 4 and 5 require and external contact closure. Internal switches select which inputs are active Interlock master interconnections are shown in Figure 5. The lens uses two masters, one for water conductivity and the other for all interlocked conditions. The Conductivity Master controls the lens water purging system and also energizes one input of the General Master. The General Master provides the external interlock for the pulsed power supply. If lithium comes into contact with the cooling water, the conductivity master will trip. Output 2 of the Master shuts off the water circulating pump and initiates purging hardware, which isolates the lens from the water supply and allows inert gas to force remaining water from the lens into a reservoir located in the vault. Output 1 of the Master, which is connected to input 4 of the lens General Master, causes the General Master to trip and disable the pulsed power supply. All other lens alarm conditions (except conductivity) enter input 1 and 2 of the Lens General Master. An alarm condition from these inputs will disable the pulsed power supply, but the water system will remain on. Each interlock master has a manual Emergency Stop pushbutton (red) on its front panel. The pushbutton has alternating action, one push enabling the interlock master, the next push opening the interlock chain. all interlock masters are connected to an audible trip alarm module located in R5E-6

Automated Synthesis of 3‘-Metalated Oligonucleotides

We report the first synthesis of a metallonucleoside bound to a solid support and subsequent oligonucleotide synthesis with this precursor. Large-scale syntheses of metal-containing oligonucleotides are achieved using a solid support modified with [Ru(bpy)_2(impy‘)]^(2+) (bpy is 2,2‘-bipyridine; impy‘ is 2‘-iminomethylpyridyl-2‘-deoxyuridine). A duplex formed with the metal-containing oligonucleotide exhibits superior thermal stability when compared to the corresponding unmetalated duplex (Tm = 50 °C vs T_m = 48 °C). Electrochemical (E_(1/2) = 1.3 V vs NHE), absorption (λ_(max) = 480 nm), and emission (λ_(max) = 720 nm, τ = 44 ns, Φ = 0.11 × 10^(-3)) data for the ruthenium-modified oligonucleotides indicate that the presence of the oligonucleotide does not perturb the electronic properties of the ruthenium complex. The absence of any change in the emission properties upon duplex formation suggests that the [Ru(bpy)_2(impy)]^(2+) chromophore will be a valuable probe for DNA-mediated electron-transfer studies. Despite the relatively high Ru(III/II) reduction potential, oxidative quenching of photoexcited [Ru(bpy)_2(impy)]^(2+) does not lead to oxidative damage of guanine or other DNA bases

Spectroscopy and Electrochemistry of Ruthenium-Modified Nucleic Acids: Design of a Novel Metal-Binding Nucleoside

Electron transfer (ET) reactions through DNA have been the subject of numerous investigations due to the implications for light-induced DNA damage and the quest for understanding long-range ET events in biological molecules. An important objective in this area continues to be the facile and site-specific incorporation of metal complexes into DNA. While recent work has focused on nucleobasic and nonnucleosidic sites for the attachment of high-potential complexes, our efforts have concentrated on the ribose ring (to minimize structural perturbations) as the incorporation site for both high- and low-potential metal complexes

Inelastic interaction mean free path of negative pions in tungsten

The inelastic interaction mean free paths lambda of 5, 10, and 15 GeV/c pions were measured by determining the distribution of first interaction locations in a modular tungsten-scintillator ionization spectrometer. In addition to commonly used interaction signatures of a few (2-5) particles in two or three consecutive modules, a chi2 distribution is used to calculate the probability that the first interaction occurred at a specific depth in the spectrometer. This latter technique seems to be more reliable than use of the simpler criteria. No significant dependence of lambda on energy was observed. In tungsten, lambda for pions is 206 plus or minus 6 g/sq cm

Analysis of Proposed 2007-2008 Revisions to the Lightning Launch Commit Criteria for United States Space Launches

Ascending space vehicles are vulnerable to both natural and triggered lightning. Launches under the jurisdiction of the United States are generally subject to a set of rules called the Lightning Launch Commit Criteria (LLCC) (Krider etal., 1999; Krider etal., 2006). The LLCC protect both the vehicle and the public by assuring that the launch does not take place in conditions posing a significant risk of a lightning strike to the ascending vehicle. Such a strike could destroy the vehicle and its payload, thus causing failure of the mission while releasing both toxic materials and debris. To assure safety, the LLCC are conservative and sometimes they may seriously limit the ability of the launch operator to fly as scheduled even when conditions are benign. In order to safely reduce the number of launch scrubs and delays attributable to the LLCC, the Airborne Field Mill (ABFM II) program was undertaken in 2000 - 2001. The effort was directed to collecting detailed high-quality data on the electrical, microphysical, radar and meteorological properties of thunderstorm-associated clouds. Details may be found in Dye et al., 2007. The expectation was that this additional knowledge would provide a better physical basis for the LLCC and allow them to be revised to be less restrictive while remaining at least as safe. That expectation was fulfilled, leading to significant revisions to the LLCC in 2003 and 2005. The 2005 revisions included the application of a new radar-derived quantity called the Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) in the rules governing flight through anvil clouds. VAHIRR is the product of the volume averaged radar reflectivity times the radardetermined cloud thickness. The reflectivity average extends horizontally 5 km west, east, south and north of a point along the flight track and vertically from the 0 C isotherm to the top of the radar cloud. This region is defined as the "Specified Volume". See Dye et al., 2006 and Merceret et al., 2006 for a more thorough description of VAHIRR. The units are dBZ km (not dBZ per kilometer) and the threshold is 10 dBZ km. It is safe to fly through an anvil cloud for which VAHIRR is below this threshold everywhere along the flight track as long as (1) the entire cloud within 5 nmi. (9.26 km) of the flight track is colder than 0 C, (2) the points at which VAHIRR must be evaluated are at least 20 km from any active convective cores and recent lightning, and (3) the radar return is not being attenuated within the Specified Volume around those points