Similar Delay Times Research Articles

Joint r-process Enrichment by Supernovae with a Metallicity Threshold and Neutron Star Mergers

The enrichment history of r-process elements has been imprinted on the stellar abundances that change in accordance with increasing metallicity in galaxies. Close examination of the [Eu/Fe] feature caused by stars in nearby galaxies, including the Large Magellanic Cloud (LMC), shows its perplexity. The decreasing trend of the [Eu/Fe] feature is followed by a nearly constant value; this trend is generally attributed to an onset of the delayed Fe release from Type Ia supernovae (SNe Ia), which is the same interpretation of the [α/Fe] feature. However, this feature appears in the LMC at [Fe/H] of approximately −0.7, which is significantly higher than that for the [α/Fe] case (≈−2). This result potentially indicates the presence of an overlooked property of the r-process site that remains unseen in the study of the Milky Way. Here, we propose that this [Eu/Fe]-knee feature is created by a fade-out of core-collapse SNe producing r-process elements; these elements along with neutron star mergers (NSMs) promote the r-process enrichment under the condition for this specific SNe such that their occurrence is limited to a low-metallicity environment. This metallicity threshold for the occurrence rate of r-process SNe at a subsolar is nearly identical to that for long gamma-ray bursts whose origin may be connected to fast-rotating massive stars. Moreover, we reason that the contribution of Eu from NSMs is crucial to maintain a high [Eu/Fe] at an early stage in dwarf galaxies by a balance with Fe from SNe Ia; both enrichments via NSMs and SNe Ia proceed with similar delay time distributions.

Novel PVT Resilient Low-Power Dynamic XOR/XNOR Design Using Variable Threshold MOS for IoT Applications

A variable threshold voltage hybrid evaluation network based dynamic XOR/XNOR gate is presented to reduce the parameters leakage power dissipation, dynamic power, and layout area compared to existing dynamic gates under similar delay time conditions. This study explores the impacts of process, supply voltage, and temperature changes on leakage power dissipation and dynamic power using Monte Carlo simulation. The Monte Carlo analysis demonstrates that leakage power dissipation and dynamic power reduction have significantly improved. Furthermore, when compared to hybrid type dynamic XOR/XNOR (N-type XOR/XNOR), the proposed design reduces leakage power and dynamic power consumption by 6.1% (54.0%) and 18.75% (35.0%), respectively. While the proposed design has a slight layout area penalty compared to a hybrid type dynamic XOR/XNOR, it offers the same amount of the layout area as a traditional N-type XOR/XNOR.

Limitations of cetane number to predict transient combustion phenomena in high-pressure fuel sprays

Fundamental understanding of in-cylinder processes in diesel engines is important to screen emerging biofuels and advanced combustion modes that can reduce greenhouse gas emissions and regulated pollutants including soot. In this study, the role of fuel properties on spray development and combustion is investigated by systematically isolating chemical and thermophysical effects. Three different fuels are considered, two with similar chemical properties and two with similar thermophysical properties with one fuel common to both groups. Experiments are performed in a constant-pressure flow chamber designed to provide stable test conditions and facilitate acquisition of at least 150 injections in quick succession for each fuel under reacting high-pressure, high-temperature ambient conditions using a modified conventional diesel engine injector. High speed optical diagnostics including rainbow schlieren deflectometry, OH* chemiluminescence, and a two-color pyrometry system are employed to simultaneously image the transient spray and reacting jets. Image analysis is performed to determine liquid length, vapor penetration length, timing and location of first stage and main ignition events, lift-off location, total soot mass, and more. Results show that fuels with similar chemical properties or cetane number (CN) exhibit similar delay times for first stage and main ignition events as may be expected, but very different liquid length, first stage and main ignition locations, lift-off length, apparent turbulent flame speed, and soot formation. As such, the ability to characterize candidate biofuels with CN or other parameters derived from simple flame configurations is called into question. In this study, thermophysical properties controlling the liquid length are identified as the main contributing factor for the observed differences.

Autonomic and Vascular Control in Prehypertensive Subjects with a Family History of Arterial Hypertension.

BackgroundIndividuals with a family history of systemic arterial hypertension (FHSAH) and / or prehypertension have a higher risk of developing this pathology.ObjectiveTo evaluate the autonomic and vascular functions of prehypertensive patients with FHSAH.MethodsTwenty-five young volunteers with FHSAH, 14 normotensive and 11 prehypertensive subjects were submitted to vascular function evaluation by forearm vascular conductance(VC) during resting and reactive hyperemia (Hokanson®) and cardiac and peripheral autonomic modulation, quantified, respectively, by spectral analysis of heart rate (ECG) and systolic blood pressure (SBP) (FinometerPRO®). The transfer function analysis was used to measure the gain and response time of baroreflex. The statistical significance adopted was p ≤ 0.05.ResultsPre-hypertensive individuals, in relation to normotensive individuals, have higher VC both at rest (3.48 ± 1.26 vs. 2.67 ± 0.72 units, p = 0.05) and peak reactive hyperemia (25, 02 ± 8.18 vs. 18.66 ± 6.07 units, p = 0.04). The indices of cardiac autonomic modulation were similar between the groups. However, in the peripheral autonomic modulation, greater variability was observed in prehypertensive patients compared to normotensive individuals (9.4 [4.9-12.7] vs. 18.3 [14.8-26.7] mmHg2; p < 0.01) and higher spectral components of very low (6.9 [2.0-11.1] vs. 13.5 [10.7-22.4] mmHg2, p = 0.01) and low frequencies (1.7 [1.0-3.0] vs. 3.0 [2.0-4.0] mmHg2, p = 0.04) of SBP. Additionally, we observed a lower gain of baroreflex control in prehypertensive patients compared to normotensive patients (12.16 ± 4.18 vs. 18.23 ± 7.11 ms/mmHg, p = 0.03), but similar delay time (-1.55 ± 0.66 vs. -1.58 ± 0.72 s, p = 0.90).ConclusionPrehypertensive patients with FHSAH have autonomic dysfunction and increased vascular conductance when compared to normotensive patients with the same risk factor.

Dynamics of sensorimotor cortex activation during absence and myoclonic seizures in a mouse model of juvenile myoclonic epilepsy.

Generalized epilepsy syndromes often confer multiple types of seizures, but it is not known if these seizures activate separate or overlapping brain networks. Recently, we reported that mice with a juvenile myoclonic epilepsy mutation (Gabra1[A322D]) exhibited both absence and myoclonic generalized seizures. Here, we determined the time course of sensorimotor cortex activation and the spatial distribution of spike voltage during these two seizures. We implanted Gabra1+/A322D mice with multiple electroencephalography (EEG) electrodes over bilateral somatosensory cortex barrel fields (S1) and anterior (aM1) and posterior (pM1) motor cortices and recorded absence seizures/spike-wave discharges (SWDs) and myoclonic seizures. We used nonlinear-association analyses and cross-correlation calculations to determine the strength, leading regions, and time delays of cortical coupling from the preictal to ictal states and within the spike and interspike periods. The distribution of spike voltage was also measured in SWDs and myoclonic seizures. EEG connectivity among all electrode pairs increased at the onset of both SWDs and myoclonic seizures. Surprisingly, during spikes of both seizure types, S1 led M1 with similar delay times. Myoclonic seizure spikes started more focally than SWD spikes, with a significant majority appearing first only in S1 electrodes, whereas a substantial fraction of SWD spikes were detected first in S1 and at least one M1 electrode. The absolute voltage of myoclonic seizure spikes was significantly higher than that of SWD spikes, and there was a greater relative voltage over M1 during myoclonic seizure spikes than in the first one to two SWD spikes. The leading sites in S1 and similar delay times suggest both SWDs and myoclonic seizures activate overlapping networks in sensorimotor cortex and thus, therapeutically targeting of this network could potentially treat both seizures. Spike focality, absolute voltage, and voltage distribution provide insight into neuronal activation during these two seizure types.

Recently diagnosed axial spondyloarthritis: gender differences and factors related to delay in diagnosis

A cohort of patients with recently diagnosed axial spondyloarthritis (SpA) was characterized with emphasis on gender differences and factors leading to delay in diagnosis. Clinical, laboratory, and imaging data of 151 consecutive patients diagnosed with ankylosing spondylitis or undifferentiated SpA in 2004-2009 and satisfying the new ASAS classification criteria for axial SpA, was collected and analyzed. Seventy-nine men and 72 women were enrolled. Both groups (men and women) had similar age of onset of disease-related symptoms, as well as similar delay time to diagnosis, follow-up duration and frequency of anti-TNF treatment. Inflammatory back pain, as a first symptom related to SpA, was reported more often by men, while women had more pelvic, heel, and widespread pain (WP) during the course of the disease. At the time of diagnosis, men were more limited in chest expansion and showed increased occiput-to-wall distance compared to women. Elevated erythrocyte sedimentation rate and/or C-reactive protein were detected in a similar proportion of men and women. Presence of WP in women almost doubled the delay in the diagnosis of SpA. No other differences in disease presentation or burden were demonstrated to correlate with delay in diagnosis.

Low power and high performance dynamic CMOS XOR/XNOR gate design

A hybrid network technique is proposed in dynamic CMOS XOR/XNOR gate to reduce the power consumption, save the layout area and avoid signal skew. Compared to the standard N type dynamic gate with similar delay time, the leakage power, dynamic power and layout area of the novel XOR/XNOR gate are reduced by up to 51%, 13% and 24%, respectively. Also, the inputs and clock signals combination static state dependent leakage characteristics of three dynamic CMOS XOR/XNOR gates are analyzed thoroughly. Finally, their robustness to noise, process and temperature variations are discussed.

Optical observation of flow field induced by pulsed laser ablation of selected target materials

A flow field induced by pulsed laser ablation of several target materials in air was observed by high-speed photography. Two Nd:YAG lasers were used in this study, one as an energy source and the other as a light source. Propagation of produced shock wave front in the early stage was visualized by the laser shadowgraphy technique. We found an appreciable density variation after about 100 μs of laser irradiation. We have tested the targets of several kinds of metals, silicon, and graphite, and observed the same phenomena at a similar delay time. This dark shadow region seems to represent the cloud of nanoparticles produced by ablated materials, which can be collected on a glass plate.