mA Range Research Articles

Miocene development of the Main Boundary Thrust and Ramgarh Thrust, and exhumation of Lesser Himalayan rocks of the Kumaun-Garhwal region, NW-Himalaya (India): Insights from Fission Track Thermochronology

• New FT ages suggest that the MBT and Saleri Thrust were initiated during ∼14 Ma. • The Amritpur granite was emplaced over the Siwalik along the MBT during late Miocene . • The Ramgarh Thrust sheet was emplaced over the LHMS zone along the RT during ∼24 Ma. • Old ZFT ages suggest that the metamorphism of the outer LHMS zone occurred < 250 °C. • Reactivation of the MBT and its associated faults occurred since Plio-Plistocene time. Bounded between the northeast dipping Main Boundary Thrust (MBT) at the base and the Saleri Thrust (ST) at the top, the Amritpur granite in the Kumaun-Garhwal region, NW-Himalaya is emplaced over the Siwalik sediments. As it is devoid of microscopic/mesoscopic imprints of the Himalayan tectonics, there is a debate regarding its emplacement along the MBT. While some interpret it as a klippe, others describe it as an intrusive body. The new apatite (AFT) and the zircon (ZFT) fission-track thermochronological data from the Amritpur granite provide similar age ranges and trends from the MBT to the ST. AFT ages range between 11.3 ± 1.6 and 14.7 ± 1.0 Ma with a weighted mean of 13.4 ± 1.5 Ma and ZFT ages range between 12.4 ± 1.2 and 15.4 ± 1.7 Ma with a weighted mean of 13.9 ± 1.2 Ma. Such age ranges and trends could be explained by rapid upliftment and exhumation of the Amritpur granite as horse rooted from the basement along the MBT from a depth of ∼8–10 km during mid-Miocene (∼14 to 13 Ma). We interpret this age as the time of development of the MBT. The new ZFT ages from the Jaunsar Group of the outer Lesser Himalayan meta-sedimentary (LHMS) zone range between 49.4 ± 2.0 and 80.3 ± 4.1 Ma (with a weighted mean of 67.5 ± 4.01 Ma) while the AFT ages range between 1.7 ± 0.2 and 4.2 ± 1.0 Ma (with a weighted mean of 3.17 ± 0.6 Ma). The old ZFT ages indicate that the outer LHMS zone underwent low-grade pre-Himalayan metamorphism (∼250 °C) around ∼67–72 Ma and the ZFT age of outer LHMS was not reset during the Himalayan orogeny. Young AFT ages from the Jaunsar Group of the outer LHMS zone reflect accelerated exhumation, likely due to reactivation of the MBT and its associated faults, since Plio-Pleistocene time. The new ZFT ages from the Ramgarh Thrust (RT) sheet range between 23.2 ± 2.4 and 24.2 ± 2.7 Ma with a weighted mean of 23.7 ± 2.5 Ma. The mean ZFT age of the RT sheet is similar to the age range of the Main Central Thrust (MCT) movements. This indicates that the RT sheet has been thrusted along the RT during 24 Ma followed by the exhumation of the RT sheet.

Thermal history along the Araçuaí Orogen and São Francisco Craton border, eastern Brazilian continental margin, based on low-temperature thermochronologic data

Passive margins form in response to rifting affecting a continental area. Rifting evolution is dependent on structural and rheological inheritance, generally controlling differential denudation, and deposition. The Brazilian continental margin developed over a complex basement, composed of the orogenic lithosphere of the Brasiliano-Pan-African orogenic belts (e.g., the Araçuaí Orogen), and the cratonic lithosphere of the São Francisco Craton. In this work, we focus on the transitional zone between the warm and cold lithosphere of the northern segment of the Araçuaí Orogen to the São Francisco Craton. This study provides the first suite of two low-temperature thermochronometers, i.e., zircon and apatite (UTh)/He, for the region. Using this approach, we examine the main cooling events, the geodynamic forces acting upon the lithosphere, the denudation rates affecting this region since West Gondwana amalgamation, and the correlation between thermochronology and structural inheritance. Our results indicate that ZHe corrected ages range from 483.1 ± 38.6 to 93.8 ± 7.5 Ma and eU concentrations vary from 10.91 to 632.51 mg/g. AHe corrected ages span from 129.9 ± 7.79 to 32.7 ± 1.96 Ma and eU concentrations range from 5.6 to 62.8 mg/g. Both ZHe and AHe ages display a positive correlation with eU concentration. Based on this dataset, we identify three cooling episodes, constrained from Lower Devonian to Carboniferous, Triassic/Jurassic to the present day, and Late Cretaceous/Paleocene to the present day. Additionally, two reheating episodes are constrained from Middle Jurassic to Early Cretaceous and from Late Cretaceous to Paleocene. Furthermore, we analyzed lineament directions in the orogenic, cratonic, and Cenozoic sedimentary cover domains to understand how structural inheritance affects the thermochronological record. Our observations reveal that reactivation of the Brasiliano NW-SE inherited structures during continental breakup up until the Paleocene possibly kept the AHe system open, resulting in the youngest AHe ages of our data set.

Class-B Power Amplifier with Si-Based Double-Gate MOSFET: A Circuit Perspective

This research work designs a power amplifier with the use of Silicon-based Double-Gate (DG) MOSFET. It is a novel device used to amplify the input signal of an audio signal, etc. This research paper provides information on the problem identification in the existing models and its design objectives with its design constraints. It also reduces crossover distortion due to DG MOSFET instead of BJTs and MOSFETs in the class-B power amplifier. This is a low-power device for the mA range using SiO2 as a dielectric material.

Preliminary evaluation of interferometry measurements of the flow field in the vicinity of a self-excited single profile

This paper deals with the interferometry measurement of the flow field in the vicinity of the surface of the self-excited single profile NACA 0015 in subsonic air flow. The pressure and velocity on the profile surface, the total forces and total moments acting on the profile are evaluated in the range of the Mach number Ma = 0.18-0.45 and the Reynolds number Re = (3-6)·105 . Since the interferogram processing was conducted with simplified assumptions of the isentropic changes of the flow field, the results have a limited accuracy especially in the case with flow separation. Results were not compared with the direct pressure measurement on the profile surface. The optical measurement method enabled the forces and moments to be evaluated separately for the suction and pressure surface of the airfoil.

Origin of the tuff parting and associated enrichments of Zr, REY, redox-sensitive and other elements in the Early Miocene coal of the Siniy Utyes Basin, southwestern Primorye, Russia

Miocene coal beds in the Siniy Utyes Basin, South Primirye, in eastern Russia, are interbedded with volcanic ash layers and are enriched in rare earth elements and Y (REY, or REE if Y is not included), Zr, redox-sensitive and other trace elements around these layers. However, high contents of fresh volcanic glass and alkalies as well as no evidence of leaching suggest that the source of these elevated concentrations of these elements are not interpreted to be derived from the volcanic ash fall layers, as is found in many other coals worldwide. In contrast, the broader geochemical signature of the coal indicates that these elements sourced from weathered granites. Interestingly, both the coal and volcanic ash contain pyrite and, less commonly, barite, REE phosphate (rhabdophane?), silver sulfate and sylvite, all of which indicate a post-depositional emplacement of these trace elements, possibly through an initial evaporative process in the peat before burial. Instead of leaching of the adjacent tuff, enrichment of REY, Zr, Mo, V, and other elements in the coal proximal to the volcanic ash layers may be a result of higher permeability and a geochemical barrier at the coal/volcanic ash interface, which concentrated element migration in these zones during diagenesis. U-Pb zircon dating (LA ICP-MS) of the volcanic ash layer indicates an age in the 18–25 Ma range. The younger (5 of 22 grains) cluster of dates, however, is in the 18–19 Ma (early Miocene) range, which may indicate the age of the actual eruption.

Why take the square root? An assessment of interstellar magnetic field strength estimation methods

Context. The magnetic field strength in interstellar clouds can be estimated indirectly from measurements of dust polarization by assuming that turbulent kinetic energy is comparable to the fluctuating magnetic energy, and using the spread of polarization angles to estimate the latter. The method developed by Davis (1951, Phys. Rev., 81, 890) and by Chandrasekhar and Fermi (1953, ApJ, 118, 1137) (DCF) assumes that incompressible magnetohydrodynamic (MHD) fluctuations induce the observed dispersion of polarization angles, deriving B ∝ 1∕δθ (or, equivalently, δθ ∝ MA, in terms of the Alfvénic Mach number). However, observations show that the interstellar medium is highly compressible. Recently, two of us (ST) relaxed the incompressibility assumption and derived instead B ∝ 1/√δθ (equivalently, δθ ∝ MA2). Aims. We explored what the correct scaling is in compressible and magnetized turbulence through theoretical arguments, and tested the assumptions and the accuracy of the two methods with numerical simulations. Methods. We used 26 magnetized, isothermal, ideal-MHD numerical simulations without self-gravity and with different types of forcing. The range of MA and sonic Mach numbers Ms explored are 0.1 ≤ MA ≤ 2.0 and 0.5 ≤ Ms ≤ 20. We created synthetic polarization maps and tested the assumptions and accuracy of the two methods. Results. The synthetic data have a remarkable consistency with the δθ ∝ MA2 scaling, which is inferred by ST, while the DCF scaling failed to follow the data. Similarly, the assumption of ST that the turbulent kinetic energy is comparable to the root-mean-square (rms) of the coupling term of the magnetic energy between the mean and fluctuating magnetic field is valid within a factor of two for all MA (with the exception of solenoidally driven simulations at high MA, where the assumption fails by a factor of 10). In contrast, the assumption of DCF that the turbulent kinetic energy is comparable to the rms of the second-order fluctuating magnetic field term fails by factors of several to hundreds for sub-Alfvénic simulations. The ST method shows an accuracy better than 50% over the entire range of MA explored; DCF performs adequately only in the range of MA for which it has been optimized through the use of a “fudge factor”. For low MA, it is inaccurate by factors of tens, since it omits the magnetic energy coupling term, which is of first order and corresponds to compressible modes. We found no dependence of the accuracy of the two methods on Ms. Conclusions. The assumptions of the ST method reflect better the physical reality in clouds with compressible and magnetized turbulence, and for this reason the method provides a much better estimate of the magnetic field strength over the DCF method. Even in super-Alfvénic cases where DCF might outperform ST, the ST method still provides an adequate estimate of the magnetic field strength, while the reverse is not true.

Studies on the radiation dose, image quality and low contrast detectability from MSCT abdomen by using low tube voltage

BackgroundTo study radiation dose, image quality and low-contrast cylinder detectability from multislice CT (MSCT) abdomen by using low tube voltage using the American College of Radiology (ACR) phantom. The ACR phantom (low-contrast module) was scanned with 64 MSCT scanner (Brilliance, Philips Medical System, Eindhoven, Netherlands) with 80 and 120 KVP, utilizing different tube current time product (mAs) range from 50 to 380 mAs. The image noise (SD), signal to noise ratio, contrast-to-noise ratio (CNR), and scores of low contrast detectability were assessed for every image respectively.ResultsFrom images analyses, the noise essentially increased with the use of low tube voltage. The CNR was 0.94 ± 0.27 at 120 KVP, and CNR was 0.43 ± 0.22 at 80 KVP. However, with the same dose, there were no differences of statistical significance in scores of low-contrast detectability between 120 KVP at 300mAs and 80 KVP at (200–380) mAs (p > 0.05). At 300 mAs, the CTDIvol obtained at 80 KVP was about 29% of that at 120 KVP. The CTDIvol obtained at 80 KVP were decreased from 5% at 50 mAs, to 37% at 380 mAs.ConclusionsThere is a possibility to decrease exposure of radiation virtually by reducing KVP from 120 to 80 KVP in examination of abdominal CT when the high tube current is used, though increasing image noise at low tube voltage.

Experience and consensus on stimulation of the anterior nucleus of thalamus for epilepsy.

Deep brain stimulation of the anterior nuclei of thalamus (ANT-DBS) is effective for reduction of seizures, but little evidence is available to guide practitioners in the practical use of this therapy. In an attempt to fill this gap, a questionnaire with 37 questions was circulated to 578clinicians who were either engaged in clinical trials of or known users of DBS for epilepsy, with responses from 141, of whom 58.2% were epileptologists and 28.4% neurosurgeons. Multiple regions of the world were represented. The survey found that the best candidates for DBS were considered those with temporal or frontal seizures, refractory to at least two medicines. Motivations for renewing therapy upon battery depletion were reduced convulsive, impaired awareness, and severe seizures and improved quality of life. Targeting of leads mainly was by magnetic resonance imaging, sometimes with intraoperative imaging or microelectrode recording. The majority used transventricular approaches. Stimulation parameters mostly imitated the SANTE study parameters, except for initial stimulation amplitudes in the 2-3-V or -mA range, versus 5V in the SANTE study. Stimulation intensity was most often increased or reduced, respectively, for lack of efficacy or side effects, but changes in active contacts, cycle time, and pulse duration were also employed. Mood or memory problems or paresthesias were the side effects most responsible for adjustments. Off-label sites stimulated included centromedian thalamus, hippocampus, neocortex, and a few others. Several physicians used DBS in conjunction with vagus nerve stimulation or responsive neurostimulation, although our study did not track efficacy for combined use. Experienced users varied more from published parameters than did inexperienced users. In conclusion, surveys of experts can provide Class IV evidence for the most prevalent practical use of ANT-DBS. We present a flowchart for one protocol combining common practices. Controlled comparisons will be needed to choose the best approach.

No evidence of improvements in inhibitory control with tRNS

Previous work suggests that transcranial random noise stimulation (tRNS) over the prefrontal cortex could influence inhibitory control. Nevertheless, the specific neural mechanisms underlying this proposed effect have not been investigated. Here, we aimed at exploring behavioral and neurophysiological effects of tRNS applied over bilateral inferior frontal gyrus (IFG) on inhibitory control performance during a Go/No-go task (GNG). Nineteen participants performed two tRNS sessions (real and sham) in a double-blind crossover design study. Stimulation was applied over the bilateral IFG during 10 min at 1 mA (range: 1/+1). Resting-state MEG activity was recorded before and after tRNS, and performance on a GNG task was tested after tRNS. Behavioral performance during the GNG task was measured by the false alarm rate (FA), the reaction time in Go (RT Go) and No-go trials (RT FA), and the variability in Go responses (individual coefficient of variability, ICV). Neurophysiological impact of tRNS was assessed using global field power and power spectral density analysis of the MEG recording during the GNG task and the resting-state, respectively. tRNS stimulation did not impact inhibitory control performance. MEG analysis showed significant brain modulations during the resting-state with an increase in power spectral amplitude in beta band (20 Hz) following application of real tRNS. Our results suggest that inhibitory control performance is not modulated by tRNS over the IFG. However, we observed significant modulation of oscillatory brain activity during the resting-state, suggesting that tRNS over bilateral IFG specifically targets the dominant frequency band involved in frontal cortical interactions.

Thermal evolution of onshore West Iberia: A better understanding of the ages of breakup and rift-to-drift in the Iberia-Newfoundland Rift

The age of breakup which formed the Central-North Atlantic has been debated for many decades and is still subject to debate: from ca. 150 Ma to 110 Ma. To address this issue, we have carried out a thermochronological study of the eastern margin of the rifted Iberia-Newfoundland sector. New apatite fission-track (AFT) data acquired on samples from the footwall (Variscan basement) and one sample (Triassic of the Lusitanian Basin) from the hanging wall of the principal normal fault bounding the basin. Thermal history of western Iberia can be then reconstructed since ca. 250 Ma. Fission-track ages of Variscan granitoids (whose crystallization age is >275 Ma) range between 191 ± 8 Ma and 75 ± 5 Ma, indicating that significant thermal events affected the study area during that period. Thermal inversion supports two main cooling events that we attribute to a major uplift and denudation of the Variscan basement, consistent with widespread basement-derived siliciclastic rocks of similar ages: Late Jurassic/Early Cretaceous (ca. 150–145 Ma) and late Early Cretaceous (ca. 110 Ma). From the sedimentary record in the Lusitanian Basin and the new AFT data, we deduce that: (1) temperatures >70–110 °C affected west Iberia between ca. 190 and 150 Ma, which can be explained partly by a subsiding basement in both foot and hanging walls; (2) the main cooling event at ca. 150–145 Ma is interpreted as major rift flank uplift; (3) the ca. 110 Ma cooling event may be linked to the final evolution of the margin and onset of oceanic spreading. We infer that the AFT main cooling event at ca. 150–145 Ma reflects the break of the elastic core of the lithosphere (whole lithosphere failure = breakup) with significant rift shoulder uplift (end of Rift 1), which was followed by hyper-extension and mantle exhumation (Rift 2) and finally, by oceanic spreading (rift-to-drift) at ca. 110 Ma (onset of Rift 3).

GaSb-based laser diodes grown on MOCVD GaAs-on-Si templates.

We report GaSb-based laser diodes (LDs) grown on on-axis (001) Si substrates and emitting at 2.3 µm. Two series of LDs were studied and compared. For the first series, a GaAs-based buffer layer was first grown by metal organic chemical vapor deposition (MOCVD) before growing the laser heterostructure by molecular-beam epitaxy (MBE). For the second series, a MOCVD GaSb buffer layer was added between the MOCVD GaAs buffer layer and the MBE laser heterostructure. Both series of LDs exhibited threshold currents in the 50-100 mA range and several mW output power at room temperature. They demonstrated continuous wave operation (CW) up to 70°C (set-up limited) without thermal rollover. Broad area LDs exhibited record threshold-current densities in the 250-350 A.cm-2 range for the second series of LDs, in spite of cracks that appeared during device processing. These results show that the design and fabrication steps of the buffer-layer stacks are critical issues in the epitaxial integration of GaSb-based optoelectronic devices on Si substrates and offer room for much performance improvement.

Magnetohydrodynamic simulations of a megaampere-class Kr-doped deuterium dense plasma focus

The addition of Kr dopant to a deuterium or deuterium–tritium dense plasma focus (DPF) is conventionally thought to enhance radiative cooling of the imploding sheath, resulting in a tighter pinch and, under optimized conditions, increased neutron yield [M. Krishnan, IEEE Trans. Plasma Sci. 40, 3189 (2012)]. In this work, 2D radiation magnetohydrodynamic (MHD) simulations are conducted of a DPF at peak current levels in the 2–3 MA range with Kr dopant concentrations of 0%, 0.1%, and 1.0% (by volume). Fully kinetic simulations are required to accurately model the pinch stagnation and accurately predict total neutron yield (thermonuclear + beam target), as MHD simulations cannot capture kinetic effects or beam-target neutron production. However, insights can be gained from following the evolution of the bulk dynamics of the sheath. The results show that sheath width narrows with increasing dopant concentration due to increased radiation. Thermonuclear neutron yields of ∼109−1010 are observed, which is in good agreement with experimental data [E. N. Hahn et al., J. Appl. Phys. 128, 143302 (2020)] and simulations [N. Bennett et al., Phys. Plasmas 24, 021702 (2017)] that measure yields of ∼1011 at ∼2 MA with ∼1% of that yield having thermonuclear origin. Scaling in excess of the conventional ∝I4 scaling is observed, though this should be confirmed with 3D and/or fully kinetic simulations of Kr-doped DPFs.

ГРАНИТОИДЫ АЛТАХТИНСКОГО КОМПЛЕКСА ВОСТОЧНОЙ ЧАСТИ БУРЕИНСКОГО КОНТИНЕНТАЛЬНОГО МАССИВА ЦЕНТРАЛЬНО-АЗИАТСКОГО СКЛАДЧАТОГО ПОЯСА: ВОЗРАСТ, ГЕОХИМИЧЕСКИЕ ОСОБЕННОСТИ, ГЕОДИНАМИЧЕСКАЯ ИНТЕРПРЕТАЦИЯ

New data are reported on the age, composition and formation conditions of the Late Triassic granitoids of minor intrusions from the eastern part of the Bureya continental massif of the Central Asian fold belt, and their geodynamic interpretation is given. U-Pb geochronological studies on zircons indicate that the age of rocks of the Altakhta syenite-leucogranite complex is in the 235–224 Ma range, which intrusion proceeding in two phases. The formation of magmatites is associated with the first phase (235.3 ± 2.9–230 Ma), which by their geochemical features are similar to А1-type intraplate granitoids and by REE concentrations to subduction- and collision-related granitoids. Geochemical characteristics of А2-type and А2 + I &amp; S-type granites (226–224 Ma) suggest their formation in a syncollisional setting. The evolution of the chemical composition of the Altakhta granitoids indicates a change in the geodynamic setting type, when the opposing (orthogonal) movement of the plates at the convergent boundary (subduction) changed to their sliding past each other (transform continental margin).

Organ dose and radiogenic risk in dental cone-beam computed tomography examinations

During the last decade, the development of cone beam computed tomography (CBCT) has led to a large range of imaging methods. CBCT has advantages compared to other extraoral radiographic imaging, but its contribution to radiation dose in patients is a point of concern. This study aims to provide a full understanding and determination of absorbed dose and an estimation of effective dose to the thyroid, bone marrow, salivary glands and brain in patients during CBCT examinations and to estimate the radiogenic risk resulting from radiation exposure. In this study, a total of 157 pediatric and adult patients with different indications were investigated at the dental clinic. All procedures were performed using Planmeca ProMax 3D Max. Sensitive organ equivalent doses were estimated using PCXMC software. Organ equivalent doses were also estimated using PCXMC software. The fixed tube voltage was set to 90.0 kVp, the mean tube current was 12.7.0 mA (range: 8.0 to 14.0) and the mean exposure time was 12.5 ± 1.8 s (range: 12.0–16.0). The overall mean patient effective dose was 150.8 μSv (range: 22.4–210.0). Salivary gland equivalent dose was the highest of all the organs measured as no protective shield was used in these patients. Patient doses were slightly higher compared to those in previous studies. Poor patient protection conditions were noted. Staff training is a vital priority regardless of a low dose of CBCT compared to other imaging modalities.

Implementazione e ottimizzazione di un protocollo per l’imaging ibrido a bassa dose con tomografia ad emissione di fotone singolo, studio preliminare

Background and aim The CT component of SPECT/CT is required for attenuation correction (AC) and anatomical localization (AL) in SPECT/CT imaging. The aim of this preliminary study is to evaluate quantitatively the image quality of different low-dose CT protocols for AL-AC, in order to reduce the patient’s radiation exposure while keeping the interpretation unchanged. Material and methods Using the 16-section CT component of a commercially available SPECT/CT scanner, we compared the standard protocol indicated by application specialists (main parameters: 120kV, 80mA, 0.8s, pitch 1.37) with different CT scans acquisitions with manually adjusted x-ray tube voltage (kV range 100-140), anode current (mA range 40-100), rotation time (s range 0.5-1), and pitch (p range 0.938- 1.75). The imaging performance of the CT system was evaluated using Cathpan 600 phantom (Phantom Laboratory, Salem, NY, USA). We evaluated uniformity (U), contrast-to-noise ratio for objects with nominal contrast of 1% (CNR1%), spatial resolution (SR) and CT linearity (L). The Volume Computed Tomography Dose Index (CTDIvol) was registered by the scanner software and compared with the different scanner acquisitions. Results The results of standard protocol results were U=0.46 HU, CNR1%=1.37, CNR0.5%=0.98, SR= 7 line pairs/cm, L=0.998 and CTDIvol=4.12mGy. The results of experimental protocols (24 acquisitions), expressed as mean, standard deviation and minimum-maximum, were U= 0.48±1.11 (0.02-2.51) HU, CNR1%=1.28±0.4 (0.39-2.08), SR= 7 line pairs/cm, L=0.998±0.001 (0.993-0.998) and CTDIvol=3.81±1.73 (1.29-7.44) mGy. An analysis of the data identified the combinations of scan parameters that have image quality comparable to the standard acquisition protocol for correcting the attenuation and anatomical localization, obtaining a significant reduction in the CTDIvol. Conclusion The different settings of tube voltage, anode current, scan time, and pitch allow to reduce the CTDIvol up to -37.9% for AL and AC purposes, maintaining an image quality comparable to the factory protocol. Further studies should be performed to verify the effect on attenuation map of the reduced kV, using an anthropomorphic phantom. Keywords: Hybrid imaging, nuclear medicine, CT, phantom, attenuation correction.

A mm-Sized Free-Floating Wireless Implantable Opto-Electro Stimulation Device.

Towards a distributed neural interface, consisting of multiple miniaturized implants, for interfacing with large-scale neuronal ensembles over large brain areas, this paper presents a mm-sized free-floating wirelessly-powered implantable opto-electro stimulation (FF-WIOS2) device equipped with 16-ch optical and 4-ch electrical stimulation for reconfigurable neuromodulation. The FF-WIOS2 is wirelessly powered and controlled through a 3-coil inductive link at 60 MHz. The FF-WIOS2 receives stimulation parameters via on-off keying (OOK) while sending its rectified voltage information to an external headstage for closed-loop power control (CLPC) via load-shift-keying (LSK). The FF-WIOS2 system-on-chip (SoC), fabricated in a 0.35-µm standard CMOS process, employs switched-capacitor-based stimulation (SCS) architecture to provide large instantaneous current needed for surpassing the optical stimulation threshold. The SCS charger charges an off-chip capacitor up to 5 V at 37% efficiency. At the onset of stimulation, the capacitor delivers charge with peak current in 1.7–12 mA range to a micro-LED (µLED) array for optical stimulation or 100–700 μA range to a micro-electrode array (MEA) for biphasic electrical stimulation. Active and passive charge balancing circuits are activated in electrical stimulation mode to ensure stimulation safety. In vivo experiments conducted on three anesthetized rats verified the efficacy of the two stimulation mechanisms. The proposed FF-WIOS2 is potentially a reconfigurable tool for performing untethered neuromodulation.

Structural controls and 40Ar/39Ar geochronological data of basic dike swarms in the eastern domain of the Parnaíba Basin, northeast Brazil

Two important magmatic events related to the breakup of the Pangea supercontinent and the opening of the Atlantic Ocean are represented, in the Parnaíba Basin (Northeast Brazil), by volcanic intrusive and subordinate extrusive rocks ascribed to the Mosquito (Early Jurassic) and Sardinha (Early Cretaceous) magmatic suites based on K–Ar and Ar/Ar dates. In the southeastern and central-eastern regions of the basin, the basic dike swarms display either a consistent or different orientations at given places. These rocks were elected for Ar/Ar geochronological dating to verify whether they have different ages or different emplacement models, integrating geochronological and tectonic-structural approaches. Structural analysis of remote sensor images and field data allowed to characterize (i) a family of consistent NE-trending lineaments in the southeastern border of the basin and (ii) three sets striking NE-SW, ENE-WSW, and NW-SE, in the central-eastern region. In outcrops, these swarms correspond to diabase dikes and sills associated with fracture and fault systems also recorded in their older host sedimentary rocks of the basin. In the southeastern region, the NE-trending dike system, correlated to the Sardinha Suite was controlled by extensional fractures and faults with the same orientation, arranged adjacent to and along the basin border. These structures indicate a NW extension, well documented further east in the continental rift basins of Northeast Brazil, related to the onset of the South Atlantic opening in the Early Cretaceous. Further north, in the central-eastern region of the basin, the emplacement of a WNW-trending dike, dated at 135 Ma, is interpreted as controlled by a strike-slip sinistral fault also related to the NW extension. The second group of dikes in this region presents older ages (190–200 Ma range), being thus correlated to the Mosquito Suite, controlled by NNW extension and well exposed in the central-western region of the basin. These older dikes, previously poorly known in the eastern domain, display variable orientations but following a NE-trending swarm of fractures along the NE-trending Transbrasiliano Lineament. It is proposed that the Mosquito Suite dikes in this domain were emplaced along coeval and older (Permian to early Triassic) structures reactivated by the NNW-SSE extension during the opening of the Central Atlantic Ocean, at the transition between the Triassic and the Jurassic.

A study for tube current exposure time products and image quality in digital mammography

Objective To investigate the relationship between current-exposure time products (mAs) and image quality in digital mammography. Methods The CDMAM phantom of 2 to 7 cm thickness were exposed by manual exposure modes using Mo-Rh anode-filer combinations. The exposure parameters were set as follows: (2 cm, 27 kVp, 10 to 90 mAs); (3 cm, 29 kVp, 20 to 120 mAs); (4 cm, 29 kVp, 20 to 200 mAs); (5 cm, 30 kVp, 40 to 220 mAs); (6 cm, 31 kVp, 40 to 260 mAs); (7 cm, 32 kVp, 80 to 280 mAs). The image quality figure (IQF), contrast to noise ratio (CNR), figure of merit (FOM) and the average glandular dose (AGD) were obtained from images. The optimum filtration and kVp for each breast thickness was found from the calculated FOMs. The optimum mAs for each breast thickness were found from the calculated FOMs and IQFs. And the Pearson correlation analysis was used to analyze the correlations among AGD, CNR and IQF. Results With the increase of mAs, the average glandular dose were linearly increased, and the FOM first increased and then decreased or changed slowly. The AGD, CNR and IQF were significantly correlated when the compression thickness was less than 7 cm (r all>0.87, P<0.05). The optimized exposure parameters were list as follows (2 cm,27 kVp,20 to 30 mAs);(3 cm,29 kVp,30 to 50 mAs); (4 cm,29 kVp,80 to 100 mAs); (5 cm, 30 kVp, 80 to 120 mAs); (6 cm, 31 kVp, 100 to 140 mAs); (7 cm, 32 kVp, 80 to 120 mAs). Conclusion The optimum range of mAs can be confirmed with different breast compression thickness and the setting of automatic exposure parameters should be chosen in clinical practice. Key words: Mammography; Image quality; Radiation dosage

An introduction to causes and consequences of Cretaceous sea-level changes (IGCP 609)

Abstract The International Geoscience Programme Project IGCP 609 addressed correlation, causes and consequences of short-term sea-level fluctuations during the Cretaceous. Processes causing several ka to several Ma (third- to fourth-order) sea-level oscillations during the Cretaceous are so far poorly understood. IGCP 609 proved the existence of sea-level cycles during potential ice sheet-free greenhouse to hothouse climate phases. These sea-level fluctuations were most probably controlled by aquifer-eustasy that is altering land-water storage owing to groundwater aquifer charge and discharge. The project investigated Cretaceous sea-level cycles in detail in order to differentiate and quantify both short- and long-term records based on orbital cyclicity. High-resolution sea-level records were correlated to the geological timescale resulting in a hierarchy of sea-level cycles in the longer Milankovitch band, especially in the 100 ka, 405 ka, 1.2 Ma and 2.4 Ma range. The relation of sea-level highs and lows to palaeoclimate events, palaeoenvironments and biota was also investigated using multiproxy studies. For a hothouse Earth such as the mid-Cretaceous, humid–arid climate cycles controlling groundwater-related sea-level change were evidenced by stable isotope data, correlation to continental lake-level records and humid–arid weathering cycles.

The LUNA-MV facility at Gran Sasso

About 25 year ago LUNA (laboratory for Underground Nuclear Astrophysics) opened the era of underground nuclear astrophysics installing a home-made 50 kV ion accelerator under the Gran Sasso mountain. A second machine, with a terminal voltage of 400 kV, was then installed and it is still in operation. Most of the processes so far investigated were connected to the physics of solar neutrinos and hence to the hydrogen burning phase in stars. The interest in next and warmers stages of star evolution (i.e. helium and carbon burning) pushed a new project based on an ion accelerator in the MV range called LUNA-MV. Thanks to a special grant of the Italian Ministry of Research (MIUR), INFN is now building, inside one of the major halls at Gran Sasso, a new facility which will host a 3.5 MV single-ended accelerator able to deliver proton, helium and carbon beams with intensity in the mA range.