We report on a terrestrial gamma ray flash (TGF) that occurred on 15 August 2014 coincident with an altitude‐triggered lightning at the International Center for Lightning Research and Testing (ICLRT) ...in North Central Florida. The TGF was observed by a ground‐level network of gamma ray, close electric field, distant magnetic field, Lightning Mapping Array (LMA), optical, and radar measurements. Simultaneous gamma ray and LMA data indicate that the upward positive leader of the triggered lightning flash induced relativistic runaway electron avalanches when the leader tip was at about 3.5 km altitude, resulting in the observed TGF. Channel luminosity and electric field data show that there was an initial continuous current (ICC) pulse in the lightning channel to ground during the time of the TGF. Modeling of the observed ICC pulse electric fields measured at close range (100–200 m) indicates that the ICC pulse current had both a slow and fast component (full widths at half maximum of 235 μs and 59 μs) and that the fast component was more or less coincident with the TGF, suggesting a physical association between the relativistic runaway electron avalanches and the ICC pulse observed at ground. Our ICC pulse model reproduces moderately well the measured close electric fields at the ICLRT as well as three independent magnetic field measurements made about 250 km away. Radar and LMA data suggest that there was negative charge near the region in which the TGF was initiated.
Key Points
Best documented TGF observed at ground
Second TGF induced by triggered lightning
An ICC pulse occurred simultaneously (within 20 μs) of the TGF
In this study, we analyze 44 terrestrial gamma‐ray flashes (TGFs) detected by the Fermi Gamma‐ray Burst Monitor (GBM) occurring in 2014–2016 in conjunction with data from the U.S. National Lightning ...Detection Network (NLDN). We examine the characteristics of magnetic field waveforms measured by NLDN sensors for 61 pulses that occurred within 5 ms of the start‐time of the TGF photon flux. For 21 (out of 44) TGFs, the associated NLDN pulse occurred almost simultaneously with (that is, within 200 μs of) the TGF. One TGF had two NLDN pulses within 200 μs. The median absolute time interval between the beginning of these near‐simultaneous pulses and the TGF flux start‐time is 50 μs. We speculate that these RF pulses are signatures of either TGF‐associated relativistic electron avalanches or currents traveling in conducting paths “preconditioned” by TGF‐associated electron beams. Compared to pulses that were not simultaneous with TGFs (but within 5 ms of one), simultaneous pulses had higher median absolute peak current (26 kA versus 11 kA), longer median threshold‐to‐peak rise time (14 μs versus 2.8 μs), and longer median peak‐to‐zero time (15 μs versus 5.5 μs). A majority (77%) of our simultaneous RF pulses had NLDN‐estimated peak currents less than 50 kA indicating that TGF emissions can be associated with moderate‐peak‐amplitude processes. The lightning flash associated with one of the TGFs in our data set was observed by a Lightning Mapping Array, which reported a relatively high‐power source at an altitude of 25 km occurring 101 μs after the GBM‐reported TGF discovery‐bin start‐time.
Key Points
TGF‐associated RF pulses have a wide range of NLDN‐estimated peak currents, which are proportional to their magnetic field peak amplitudes
Median rise time and peak‐to‐zero time for TGF‐simultaneous RF pulses were significantly longer than those for nonsimultaneous pulses
A TGF that was associated with relatively high‐power VHF radiation is described in detail
The theory is advanced that the common denominator of a wide range of addictive substances is their ability to cause psychomotor activation. This view is related to the theory that all positive ...reinforcers activate a common biological mechanism associated with approach behaviors and that this mechanism has as one of its components dopaminergic fibers that project up the medial forebrain bundle from the midbrain to limbic and cortical regions. Evidence is reviewed that links both the reinforcing and locomotor-stimulating effects of both the psychomotor stimulants and the opiates to this brain mechanism. It is suggested that nicotine, caffeine, barbiturates, alcohol, benzodiazepines, cannabis, and phencyclidine-each of which also has psychomotor stimulant actions-may activate the dopaminergic fibers or their output circuitry. The role of physical dependence in addiction is suggested to vary from drug to drug and to be of secondary importance in the understanding of compulsive drug self-administration.
This study examined tolerance to cocaine's threshold-lowering effect in brain stimulation reward (BSR) following continuous cocaine infusions and secondly, used the nitric oxide synthase inhibitor ...Nω-nitro-L-arginine methyl ester (L-NAME) to determine NO's involvement in the development of cocaine tolerance. Animals were continuously infused with saline or cocaine (30mg/kg per day) via osmotic minipump for 14days and injected daily with saline or L-NAME (30mg/kg, i.p.) following BSR testing. Saline-treated animals continuously infused with saline showed stable BSR thresholds across the 14-day infusion period. Saline-treated animals continuously infused with cocaine showed markedly lowered BSR thresholds on Day 1 followed by a progressive increase in BSR thresholds across the infusion period – indicating the development of tolerance. L-NAME-treated animals continuously infused with cocaine showed stimulation thresholds that were not significantly different from saline-treated animals continuously infused with cocaine.
A cocaine challenge injection (10mg/kg, i.p.) administered 3 and again at 10days following minipump removal revealed that saline-treated animals continuously infused with saline showed lowered BSR thresholds. Saline-treated animals continuously infused with cocaine displayed lowered BSR thresholds that were not significantly different from saline-infused animals. L-NAME treated animals continuously infused with cocaine showed higher BSR thresholds to a challenge 3days following pump removal. However, stimulation thresholds for this group failed to reach statistical significance on both days (i.e., Days 3 and 10) following pump removal.
Results showed that animals continuously infused with cocaine develop robust tolerance to cocaine's threshold-lowering effect during the 14-day infusion period. Tolerance to cocaine's threshold-lowering effect was short-lived and dissipated soon after minipump removal. L-NAME treatment failed to significantly alter the development of tolerance to cocaine's threshold-lowering suggesting that NO does not have a primary role in the development of cocaine tolerance.
•Continuously-infused cocaine attenuated cocaine's facilitation of BSR thresholds.•Tolerance to cocaine's facilitation effect dissipated soon after minipump removal.•L-NAME failed to alter the development of cocaine-induced tolerance.
•Earthworm assemblages associated with discrete ecological habitats.•Earthworm species had distinct ecosystem niches.•First spatial distribution maps of East Texas native and non-native earthworm ...species.•First state record of B. longicinctus in Texas.•Second state record of D. mississippiensis in Texas.
Earthworms were collected and identified in different ecological habitats of the Stephen F. Austin Experimental Forest (SFAEF) in the Piney Woods Ecoregion (PWE) of Texas. Earthworm spatial distribution data were collected over four distinct ecological habitats with a range of soil conditions and vegetative cover. A total of 128 sampling plots were surveyed in two different, broadly defined locations (mesic slope=68 plots, dry-mesic upland=60 plots). Using multivariate classification/ordination (TWINSPAN) and detrended correspondence analysis (DCA) of overstory vegetation data, these two locations were further divided into four distinct habitats: dry-mesic mixed upland, transitional zone, mesic slope and wet forested seeps. By using TWINSPAN and principal component analysis (PCA), it was found that earthworm species assemblages and understory vegetation corresponded to these discrete ecological habitats. ArcGIS10 was then used to create spatial distribution maps of earthworm species throughout these delineated ecological habitats in the SFAEF. Six earthworm species from the native North American genus Diplocardia were collected at SFAEF: D. caroliniana Eisen (1899), D. eiseni Michaelsen (1894), D. komareki Gates (1977); D. macdowelli Murchie (1963), D. mississippiensis Smith (1924) and D. ornata Gates (1943). Two earthworm species from the native North American genus Bimastos were collected: B. heimburgeri Smith 1928 and B. longicinctus Smith and Gittins 1915. The collection of B. longicinctus is a new state record for Texas. Amynthas corticis Kinberg (1867) specimens were collected, which represent a non-native genus from Southeast Asia. Ocnerodrilidae, a megadrile family first described by Beddard in 1891, were also collected likely representing non-native species originating from intertropical America and Africa (Christoffersen, 2008).
Factor Xa (FXa) is a key coagulation protease and target for novel antithrombotic agents for prevention and treatment of diverse thromboembolic disorders. In the present study we describe the effect ...of a novel, potent, and selective FXa inhibitor, DPC602, on brain damage and neurobehavioral consequence in a rat thromboembolic model of stroke.
Thromboembolic stroke was induced in rats by placement of an autologous clot into the middle cerebral artery.
Laser-Doppler monitoring of cerebral blood flow demonstrated that DPC602 (8 mg/kg, single IV/IP bolus pretreatment) markedly improved cerebral blood flow after thromboembolic stroke by 25% to 160% (n=6; P<0.001) at 1 to 6 hours. DPC602 demonstrated concentration- and time-dependent reductions in infarct size, with maximal effect (89% reduction; n=14; P<0.001) at the highest dose over controls. Neurological function was also significantly improved in DPC602-treated rats at days 1, 3, and 7 (n=13; P<0.01). DPC602 treatment did not cause cerebral hemorrhage, assessed by free hemoglobin in the ischemic brain tissues.
These data suggest that anticoagulation with a selective FXa inhibitor might ameliorate the extent of ischemic brain damage and neurological deficits after a thromboembolic event. Enhanced clot dissolution and early reperfusion may account for the cerebrovascular-protective effect of the drug.
Rats were tested for the rewarding effects of ethanol using a place preference conditioning procedure. After receiving a total of 15 daily conditioning trials under 1.0 g/kg ethanol (IP), a ...significant place preference was produced. Subjects conditioned using saline or 0.5 g/kg ethanol showed no changes in place preference. This study suggests that failures to demonstrate rewarding effects from ethanol with the conditioned place preference method may be due to an insufficient number of conditioning trials or to an inadequate exposure to the drug. The fact that place preference conditioning was effective in demonstrating ethanol reward while other methods have been equivocal suggests that this method may be a valuable technique for studying the mechanisms of ethanol reward.
Ecological invasions of generalist species often are facilitated by anthropogenic disturbance. Coyotes (Canis latrans) have benefitted from anthropogenic changes to North American ecosystems and have ...experienced a dramatic range expansion since the early 19th century. The region east of the Mississippi River has been colonized via 2 routes that have converged in the mid-Atlantic region during the past few decades. Coyotes using the northern route of expansion show molecular evidence of admixture with the Great Lakes wolf (GLW). We used noninvasive molecular techniques to detect the geographic origins of the recent coyote colonization of northern Virginia as a representative of the mid-Atlantic region and to detect signatures of admixture with GLWs. Of 455 individual canid scats screened, we sequenced a variable 282-base pair fragment of the mitochondrial control region from 126 coyote scats, assigned individual identities to samples using 6 microsatellite loci, and conducted phylogeographic analyses by comparing our sequences to previously published haplotypes. In 39 individuals identified in our scat surveys we detected 7 mitochondrial DNA haplotypes, all of which have been previously reported in diverse surrounding geographic localities. Phylogeographic analyses indicate multiple sources of colonization of northern Virginia. One common haplotype detected in northern Virginia is of wolf origin, indicating the presence of admixed coyotes and GLWs from the north.
This study determined if Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) administered after the cocaine-conditioning trial attenuated the development of sensitization to cocaine's ...locomotor-stimulating effect and secondly, determined if L-NAME blocked conditioned-locomotor activity (LMA) elicited by a saline-challenge injection. Results revealed that cocaine-injected animals (10 mg/kg, i.p.) showed enhanced locomotor activity across the three conditioning trials (all p's < .05). Cocaine-injected animals administered L-NAME (30 mg/kg, i.p.) after each conditioning trial showed a slight increase in cocaine-stimulated LMA from the first to the second conditioning trial (all p's < .05) and no further increases in LMA thereafter. A saline-challenge injection administered 72 hr after the last conditioning trial revealed that cocaine-injected animals displayed as much locomotor stimulation to a saline injection as they did during their initial exposure to cocaine on the first conditioning trial - indicating the development of cocaine-conditioned LMA.
The present findings show that L-NAME administered after the cocaine-conditioning trial attenuates the development of sensitization to cocaine's locomotor-stimulating effect. The failure of L-NAME to block cocaine-conditioned LMA suggests that the pharmacological and conditioning mechanisms of sensitization can be dissociated. It is unlikely that L-NAME's effect is due to a sedative action produced by residual L-NAME since animals administered L-NAME (30 mg/kg, i.p.) for 10 consecutive days exhibited a similar responsiveness to a cocaine challenge administered 3 and 10 days following the termination of L-NAME administration. These data support a role for nitric oxide's involvement in the neuroadaptive responses that result from continued stimulant administration and demonstrate the importance of conditioned drug effects.
Rats were trained to lever press for intravenous cocaine (1.0 mg/kg/injection) and then switched to bromocriptine (0.3, 1.0, or 3.0 mg/kg/injection) on a FR-1 reinforcement schedule. Bromocriptine ...sustained responding at all three doses; hourly drug intake increased linearly with log-dose. In a second experiment, animals were trained to respond for cocaine (1.0 mg/kg/injection) or heroin (0.1 mg/kg/injection) reinforcement; drug was available for the first 2 h of each daily session; saline was substituted for cocaine or heroin for 5 subsequent hours. One hour into each saline substitution session, an intravenous injection of saline or bromocriptine (0.0, 0.5, 1.0, or 2.0 mg/kg) was given. Bromocriptine reinstated both cocaine-trained and heroin-trained lever pressing; under these conditions, the drug was most effective in the heroin-trained animals. Reinforcing doses of clonidine (0.0625 and 0.125 mg/kg), methohexital, and nicotine (0.05 and 0.1 mg/kg), and a sub-intoxicating dose of ethanol (2 g/kg) failed to reinstate cocaine-trained responding. These data indicate that bromocriptine has cocaine-like and heroin-like stimulus and reinforcing effects.
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