Interpolar methane gradient (IPG) data from ice cores suggest the "switching on" of a major Northern Hemisphere methane source in the early Holocene. Extensive data from Russia's West Siberian ...Lowland show (i) explosive, widespread peatland establishment between 11.5 and 9 thousand years ago, predating comparable development in North America and synchronous with increased atmospheric methane concentrations and IPGs, (ii) larger carbon stocks than previously thought (70.2 Petagrams, up to approximately 26% of all terrestrial carbon accumulated since the Last Glacial Maximum), and (iii) little evidence for catastrophic oxidation, suggesting the region represents a long-term carbon dioxide sink and global methane source since the early Holocene.
The Hawaiian-Emperor hotspot track has a prominent bend, which has served as the basis for the theory that the Hawaiian hotspot, fixed in the deep mantle, traced a change in plate motion. However, ...paleomagnetic and radiometric age data from samples recovered by ocean drilling define an age-progressive paleolatitude history, indicating that the Emperor Sea-mount trend was principally formed by the rapid motion (over 40 millimeters per year) of the Hawaiian hotspot plume during Late Cretaceous to early-Tertiary times (81 to 47 million years ago). Evidence for motion of the Hawaiian plume affects models of mantle convection and plate tectonics, changing our understanding of terrestrial dynamics.
On 21 January 2005, a moderate magnetic storm produced a number of anomalous features, some seen more typically during superstorms. The aim of this study is to establish the differences in the space ...environment from what we expect (and normally observe) for a storm of this intensity, which make it behave in some ways like a superstorm. The storm was driven by one of the fastest interplanetary coronal mass ejections in solar cycle 23, containing a piece of the dense erupting solar filament material. The momentum of the massive solar filament caused it to push its way through the flux rope as the interplanetary coronal mass ejection decelerated moving toward 1 AU creating the appearance of an eroded flux rope (see companion paper by Manchester et al. (2014)) and, in this case, limiting the intensity of the resulting geomagnetic storm. On impact, the solar filament further disrupted the partial ring current shielding in existence at the time, creating a brief superfountain in the equatorial ionosphere—an unusual occurrence for a moderate storm. Within 1 h after impact, a cold dense plasma sheet (CDPS) formed out of the filament material. As the interplanetary magnetic field (IMF) rotated from obliquely to more purely northward, the magnetotail transformed from an open to a closed configuration and the CDPS evolved from warmer to cooler temperatures. Plasma sheet densities reached tens per cubic centimeter along the flanks—high enough to inflate the magnetotail in the simulation under northward IMF conditions despite the cool temperatures. Observational evidence for this stretching was provided by a corresponding expansion and intensification of both the auroral oval and ring current precipitation zones linked to magnetotail stretching by field line curvature scattering. Strong Joule heating in the cusps, a by‐product of the CDPS formation process, contributed to an equatorward neutral wind surge that reached low latitudes within 1–2 h and intensified the equatorial ionization anomaly. Understanding the geospace consequences of extremes in density and pressure is important because some of the largest and most damaging space weather events ever observed contained similar intervals of dense solar material.
Key Points
The interactions are studied between geospace and a solar filament
Cold dense plasma sheet forms from filament material stretching magnetotail
Creates anomalous features including superfountain and expanded auroral oval
A portable monoenergetic 24 keV neutron source based on the 124Sb-9Be photoneutron reaction and an iron filter has been constructed and characterized. The coincidence of the neutron energy from SbBe ...and the low interaction cross-section with iron (mean free path up to 29 cm) makes pure iron specially suited to shield against gamma rays from 124Sb decays while letting through the neutrons. To increase the 124Sb activity and thus the neutron flux, a >1 GBq 124Sb source was produced by irradiating a natural Sb metal pellet with a high flux of thermal neutrons in a nuclear reactor. The design of the source shielding structure makes for easy transportation and deployment. A hydrogen gas proportional counter is used to characterize the neutrons emitted by the source and a NaI detector is used for gamma background characterization. At the exit opening of the neutron beam, the characterization determined the neutron flux in the energy range 20–25 keV to be 6.00±0.30 neutrons per cm2 per second and the total gamma flux to be 245±8 gammas per cm2 per second (numbers scaled to 1 GBq activity of the 124Sb source). A liquid scintillator detector is demonstrated to be sensitive to neutrons with incident kinetic energies from 8 to 17 keV, so it can be paired with the source as a backing detector for neutron scattering calibration experiments. This photoneutron source provides a good tool for in-situ low energy nuclear recoil calibration for dark matter experiments and coherent elastic neutrino-nucleus scattering experiments.
The replacement of the existing endcap calorimeter in the Compact Muon Solenoid (CMS) detector for the high-luminosity LHC (HL-LHC), scheduled for 2027, will be a high granularity calorimeter. It ...will provide detailed position, energy, and timing information on electromagnetic and hadronic showers in the immense pileup of the HL-LHC. The High Granularity Calorimeter (HGCAL) will use 120-, 200-, and 300-μm-thick silicon (Si) pad sensors as the main active material and will sustain 1 MeV neutron equivalent fluences up to about 1016neqcm−2. In order to address the performance degradation of the Si detectors caused by the intense radiation environment, irradiation campaigns of test diode samples from 8-inch and 6-inch wafers were performed in two reactors. Characterization of the electrical and charge collection properties after irradiation involved both bulk polarities for the three sensor thicknesses. Since the Si sensors will be operated at −30ˆC to reduce increasing bulk leakage current with fluence, the charge collection investigation of 30 irradiated samples was carried out with the infrared-TCT setup at −30ˆC. TCAD simulation results at the lower fluences are in close agreement with the experimental results and provide predictions of sensor performance for the lower fluence regions not covered by the experimental study. All investigated sensors display 60% or higher charge collection efficiency at their respective highest lifetime fluences when operated at 800 V, and display above 90% at the lowest fluence, at 600 V. The collected charge close to the fluence of 1016neqcm−2 exceeds 1 fC at voltages beyond 800 V.
Mutant mice lacking the central region of the presynaptic active zone protein Bassoon were generated to establish the role of this protein in the assembly and function of active zones as sites of ...synaptic vesicle docking and fusion. Our data show that the loss of Bassoon causes a reduction in normal synaptic transmission, which can be attributed to the inactivation of a significant fraction of glutamatergic synapses. At these synapses, vesicles are clustered and docked in normal numbers but are unable to fuse. Phenotypically, the loss of Bassoon causes spontaneous epileptic seizures. These data show that Bassoon is not essential for synapse formation but plays an essential role in the regulated neurotransmitter release from a subset of glutamatergic synapses.
Background Endoscopic ablation of Barrett's esophagus (BE) is a treatment option for patients with high-grade dysplasia (HGD) and intramucosal carcinoma (IMCA). Objective To assess the safety and ...efficacy of a unique noncontact method of liquid nitrogen cryoablation as measured by histologic response rate and cancer-free survival. Design Single-center, nonrandomized cohort study. Setting Referral center, conducted between September 2005 and September 2008. Patients Patients with BE and HGD or IMCA who were deemed inoperable or who refused esophagectomy. Age, length of BE, and previous ablation were not exclusion criteria. Intervention Cryoablation every 6 weeks until endoscopic resolution. EMR was used for pathologic staging of nodular areas before cryoablation and focal residual areas during the follow-up period. Main Outcome Measurements Histologic response was defined by the worst pathology obtained at any level of the esophagus or gastric cardia in 1 of 3 categories: (1) incremental = absence of HGD and IMCA in all biopsy specimens, (2) partial = residual IMCA with absence of any dysplasia, and (3) complete = absence of any intestinal metaplasia or dysplasia. Results Thirty patients underwent ablation; 9 had undergone previous ablation or mucosectomy. Twenty-seven of 30 patients (90%) had downgrading of pathology stage after treatment. Elimination of cancer or downgrading of HGD at last follow-up was 68% for HGD and 80.0% for IMCA, with a median follow-up period of 12 months (25th percentile, 6; 75th percentile, 24). Minor adverse events included mild pain (n = 7), a low incidence of mild strictures (n = 3), and lip ulcer (n = 1). One major adverse event (perforation) in a patient with Marfan syndrome occurred with the prototype system. During follow-up, 3 of 6 patients with complete response had recurrence of dysplasia or cancer in the gastric cardia. Limitations A nonrandomized, single-center study with a heterogeneous cohort of patients. Conclusions Patients with BE and HGD or IMCA have a positive response to endoscopic cryotherapy at 1-year follow-up.
A prototype silicon–tungsten electromagnetic calorimeter (ECAL) for an international linear collider (ILC) detector was installed and tested during summer and autumn 2006 at CERN. The detector had ...6480 silicon pads of dimension
1
×
1
cm
2
. Data were collected with electron beams in the energy range 6–45
GeV. The analysis described in this paper focuses on electromagnetic shower reconstruction and characterises the ECAL response to electrons in terms of energy resolution and linearity. The detector is linear to within approximately the 1% level and has a relative energy resolution of
(
16.53
±
0.14
(
stat
)
±
0.4
(
syst
)
)
/
E
(
GeV
)
⊕
(
1.07
±
0.07
(
stat
)
±
0.1
(
syst
)
)
(
%
)
. The spatial uniformity and the time stability of the ECAL are also addressed.
Surface damage caused by ionizing radiation in SiO2 passivated silicon particle detectors consists mainly of theaccumulation of a positively charged layer along withtrapped-oxide-charge and interface ...traps inside the oxide and closeto the Si/SiO2-interface. High density positive interface netcharge can be detrimental to the operation of a multi-channel n-on-p sensor since the inversion layer generated under theSi/SiO2-interface can cause loss of position resolution bycreating a conduction channel between the electrodes. In theinvestigation of the radiation-induced accumulation of oxide chargeand interface traps, a capacitance-voltage characterization study ofn/γ- and γ-irradiated Metal-Oxide-Semiconductor (MOS)capacitors showed that close agreement between measurement andsimulation were possible when oxide charge density was complementedby both acceptor- and donor-type deep interface traps with densitiescomparable to the oxide charges. Corresponding inter-stripresistance simulations of a n-on-p sensor with the tuned oxidecharge density and interface traps show close agreement withexperimental results. The beneficial impact of radiation-inducedaccumulation of deep interface traps on inter-electrode isolationmay be considered in the optimization of the processing parametersof isolation implants on n-on-p sensors for the extremeradiation environments.
Background —Bolus thrombolytic therapy is a simplified means of administering thrombolysis that facilitates rapid time to treatment. TNK-tissue plasminogen activator (TNK-tPA) is a highly ...fibrin-specific single-bolus thrombolytic agent. Methods and Results —In TIMI 10B, 886 patients with acute ST-elevation myocardial infarction presenting within 12 hours were randomized to receive either a single bolus of 30 or 50 mg TNK-tPA or front-loaded tPA and underwent immediate coronary angiography. The 50-mg dose was discontinued early because of increased intracranial hemorrhage and was replaced by a 40-mg dose, and heparin doses were decreased. TNK-tPA 40 mg and tPA produced similar rates of TIMI grade 3 flow at 90 minutes (62.8% versus 62.7%, respectively, P =NS); the rate for the 30-mg dose was significantly lower (54.3%, P =0.035) and was 65.8% for the 50-mg dose ( P =NS). A prespecified analysis of weight-based TNK-tPA dosing using median TIMI frame count demonstrated a dose response ( P =0.001). Similar dose responses were observed for serious bleeding and intracranial hemorrhage, but significantly lower rates were observed for both TNK-tPA and tPA after the heparin doses were lowered and titration of the heparin was started at 6 hours. Conclusions —TNK-tPA, given as a single 40-mg bolus, achieved rates of TIMI grade 3 flow similar to those of the 90-minute bolus and infusion of tPA. Weight-adjusting TNK-tPA appears to be important in achieving optimal reperfusion; reduced heparin dosing appears to improve safety for both agents. Together with the safety results from the parallel Assessment of the Safety of a New Thrombolytic: TNK-tPA (ASSENT I) trial, an appropriate dose of this single-bolus thrombolytic agent has been identified for phase III testing.
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