Investigations of afterpulsing and detection efficiency recovery in superconducting nanowire single-photon detectors

We report on the observation of a non-uniform dark count rate in Superconducting Nanowire Single Photon Detectors (SNSPDs), specifically focusing on an afterpulsing effect present when the SNSPD is operated at a high bias current regime. The afterpulsing exists for real detection events (triggered by input photons) as well as for dark counts (no laser input). In our standard set-up, the afterpulsing is most likely to occur at around 180 ns following a detection event, for both real counts and dark counts. We characterize the afterpulsing behavior and speculate that it is not due to the SNSPD itself but rather the amplifiers used to boost the electrical output signal from the SNSPD. We show that the afterpulsing indeed disappears when we use a different amplifier with a better low frequency response. We also examine the short-lived enhancement of detection efficiency during the recovery of the SNSPD due to temporary perturbation of the bias and grounding conditions

Model for hypernucleus production in heavy ion collisions

We estimate the production cross sections of hypernuclei in projectile like fragment (PLF) in heavy ion collisions. The discussed scenario for the formation cross section of hypernucleus is: (a) Lambda particles are produced in the participant region but have a considerable rapidity spread and (b) Lambda with rapidity close to that of the PLF and total momentum (in the rest system of PLF) up to Fermi motion can then be trapped and produce hypernuclei. The process (a) is considered here within Heavy Ion Jet Interacting Generator HIJING-BBbar model and the process (b) in the canonical thermodynamic model (CTM). We estimate the production cross-sections for light hypernuclei for C + C at 3.7 GeV total nucleon-nucleon center of mass energy and for Ne+Ne and Ar+Ar collisions at 5.0 GeV. By taking into account explicitly the impact parameter dependence of the colliding systems, it is found that the cross section is different from that predicted by the coalescence model and large discrepancy is obtained for 6_He and 9_Be hypernuclei.Comment: 9 pages, 4 figures, 3 tables, revtex4, added reference

Direct imaging of primary atomisation in the near-nozzle region of diesel sprays

The spray formation and breakup of n-dodecane was investigated experimentally on a common rail diesel injector using a long working distance microscope. The objectives were to further the fundamental understanding of the processes involved in the initial stage of diesel spray formation under engine-like operating conditions, i.e. high ambient pressure and temperature. Present measurements show that the end of injection is dependent on injection pressure for low injection pressure of 50 MPa and independent for 100-150 MPa pressure range. The end of injection was characterized by large ligaments and deformed droplets along with spherical droplets. It was noted that formation of large droplets during end of injection was not related to injection pressure. The large droplets were found to be in the range of up to 50 μm, which were moving with relatively low velocity. Typical velocity range for large droplets (30-50 μm) was between 1.5 to 5 m/s. The trajectory of individual droplets appeared to be random from injection to injection. It was particularly emphasized that the real fuel injector under engine-like operating conditions can produce a fuel spray, which can be a mix of liquid and vapour at the start of injection. In this publication we report on progress made with ongoing experimental investigations of the atomisation of n-dodecane by using microscopic imaging and high-speed video using ECN ‘Spray A’ injector. A long-distance microscopy was used to study near-nozzle region (1.025x0.906 mmm). Our study focuses on the primary atomisation during the start, the steady-state and the end of the injection process

Small RNA populations for two unrelated viruses exhibit different biases in strand polarity and proximity to terminal sequences in the insect host Homalodisca vitripennis

AbstractNext generation sequence analyses were used to assess virus-derived small RNA (vsRNA) profiles for Homalodisca coagulata virus-1 (HoCV-1), family Dicistroviridae, and Homalodisca vitripennis reovirus (HoVRV), family Reoviridae, from virus-infected H. vitripennis, the glassy-winged sharpshooter. The vsRNA reads were mapped against the monopartite genome of HoCV-1 and all 12 genome segments of HoVRV, and 21nt vsRNAs were most common. However, strikingly contrasting patterns for the HoCV-1 and HoVRV genomic RNAs were observed. The majority of HoCV-1 vsRNAs mapped to the genomic positive-strand RNA and, although minor hotspots were observed, vsRNAs mapped across the entire genomic RNA. In contrast, HoVRV vsRNAs mapped to both positive and negative-sense strands for all genome segments, but different genomic segments showed distinct hotspots. The HoVRV vsRNAs were more common for 5′ and 3′ regions of HoVRV regions of all segments. These data suggest that taxonomically different viruses in the same host offer different targets for RNA-antiviral defense

Nanoscale electrochemical visualization of grain-dependent anodic iron dissolution from low carbon steel

The properties of steels and other alloys are often tailored to suit specific applications through the manipulation of microstructure (e.g., grain structure). Such microscopic heterogeneities are also known to modulate corrosion susceptibility/resistance, but the exact dependency remains unclear, largely due to the challenge of probing and correlating local electrochemistry and structure at complex (alloy) surfaces. Herein, high-resolution scanning electrochemical cell microscopy (SECCM) is employed to perform spatially-resolved potentiodynamic polarisation measurements, which, when correlated to co-located structural information from electron backscatter diffraction (EBSD), analytical scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), reveal the relationship between anodic metal (iron) dissolution and the crystallographic orientation of low carbon steel in aqueous sulfuric acid (pH 2.3). Considering hundreds of individual measurements made on each of the low-index planes of body-centred cubic (bcc) low carbon steel, the rate of iron dissolution, and thus overall corrosion susceptibility, increases in the order (101) < (111) < (100). These results are rationalized by complementary density functional theory (DFT) calculations, where the experimental rate of iron dissolution correlates with the energy required to remove (and ionise) one iron atom at the surface of a lattice, calculated for each low index orientation. Overall, this study further demonstrates how nanometre-resolved electrochemical techniques such as SECCM can be effectively utilised to vastly improve the understanding of structure-function in corrosion science, particularly when combined with complementary, co-located structural characterisation (EBSD, STEM etc.) and computational analysis (DFT)

MANP Activation Of The cGMP Inhibits Aldosterone Via PDE2 And CYP11B2 In H295R Cells And In Mice

Background: Aldosterone is a critical pathological driver for cardiac and renal diseases. We recently discovered that mutant atrial natriuretic peptide (MANP), a novel atrial natriuretic peptide (ANP) analog, possessed more potent aldosterone inhibitory action than ANP in vivo. MANP and natriuretic peptide (NP)-augmenting therapy sacubitril/valsartan are under investigations for human hypertension treatment. Understanding the elusive mechanism of aldosterone inhibition by NPs remains to be a priority. Conflicting results were reported on the roles of the pGC-A (particulate guanylyl cyclase A receptor) and NP clearance receptor in aldosterone inhibition. Furthermore, the function of PKG (protein kinase G) and PDEs (phosphodiesterases) on aldosterone regulation are not clear. Methods: In the present study, we investigated the molecular mechanism of aldosterone regulation in a human adrenocortical cell line H295R and in mice. Results: We first provided evidence to show that pGC-A, not NP clearance receptor, mediates aldosterone inhibition. Next, we confirmed that MANP inhibits aldosterone via PDE2 (phosphodiesterase 2) not PKG, with specific agonists, antagonists, siRNA silencing, and fluorescence resonance energy transfer experiments. Further, the inhibitory effect is mediated by a reduction of intracellular Ca2+ levels. We then illustrated that MANP directly reduces aldosterone synthase CYP11B2 (cytochrome p450 family 11 subfamily b member 2) expression via PDE2. Last, in PDE2 knockout mice, consistent with in vitro findings, embryonic adrenal CYP11B2 is markedly increased. Conclusions: Our results innovatively explore and expand the NP/pGC-A/3',5', cyclic guanosine monophosphate (cGMP)/PDE2 pathway for aldosterone inhibition by MANP in vitro and in vivo. In addition, our data also support the development of MANP as a novel ANP analog drug for aldosterone excess treatment

Droplet Misalignment Limit for Inkjet Printing into Cavities on Textured Surfaces

The control of droplets deposited onto textured surfaces is of great importance for both engineering and medical applications. This research investigates the dynamics of a single droplet deposited into a confined space and its final equilibrium morphology, with emphasis given to droplet deposition under print head misalignment, the effect of nonuniform wettability, and deposition of droplets with varying sizes. A multiphase pseudopotential lattice Boltzmann methodology is used to simulate the process of deposition. The print quality is characterized in terms of a parameter referred to as the wetted fraction, which describes the proportion of the cavity that is wetted by the droplet. Our results show how single and multiple axis misalignment affect the final equilibrium morphology, and it was found for comparable configurations that multiaxis misalignment resulted in a higher wetted fraction. Investigations into wettabilities of the substrate and cavity wall revealed how larger ratios of the contact angles between the two enhance the ability for the droplet to self-align within the cavity. Additionally, a range of uniform wettabilities between the substrate and cavity were found, which mitigate against misalignment. Investigations into varying droplet sizes relative to the cavity revealed how misalignment can be compensated for with larger droplets, and limits for filling a cavity with a single drop are defined. Finally, we explore the deposition with misalignment into closely positioned cavities where it is found that the spacing between cavities is a key factor in determining the maximum permissible misalignment