Search

ABSTRACTExperiments are presented on the deformation of free surface induced by water exit of axisymmetric bodies, particular at the moment before body detaching from water. A set of experimental apparatus is designed to provide driving force for the bodies. A high-speed camera is adopted to capture the motion and deformation of the free surface. Bodies of various shapes, including a stretched spheroid, a sphere, a circular cone and a combination of cylinder and circular cone, are lifted out of water with different velocities, by using a straight rod attached on the top of models. It is found that free-surface deformation is affected by the moving velocity a lot. Three wake flow or free-surface spike patterns are generated corresponding to different velocities. When the velocity is larger than a critical velocity, cavitation incepts and bubble is entrapped inside the water spike, which changes the flow pattern and shape of the spike. It is aimed to explore the spike phenomenon of free surface and explain the reasons behind it.

Based on the measurements of ~100‐keV to 10‐MeV electrons from the Magnetic Electron Ion Spectrometer (MagEIS) and Relativistic Electron and Proton Telescope (REPT) on the Van Allen Probes, the radiation belt electron energy spectra characterization and evolution have been investigated systematically. The results show that the majority of radiation belt electron energy spectra can be represented by one of three types of distributions: exponential, power law, and bump‐on‐tail (BOT). The exponential spectra are generally dominant in the outer radiation belt outside the plasmasphere, power law spectra usually appear at high L‐shells during injections of lower‐energy electrons, and BOT spectra commonly dominate inside the plasmasphere at L>2.5 during relatively quiet times. The main features of three types of energy spectra have also been revealed. Specifically, for the BOT energy spectrum, the energy of local flux maximum usually ranges from approximately hundreds of keV to several MeV and the energy of local flux minimum varies from ~100 keV to ~MeV, both increasing as L‐shell decreases, confirming the plasmaspheric hiss wave scattering to be the main mechanism forming the BOT energy spectra. Statistical results using 4‐year observations from the Van Allen Probes on the relation between energy spectra and plasmapause location also show that the plasmasphere plays a critical role in shaping radiation belt electron energy spectrum: the peak location of BOT energy spectra is ~1 L‐shell inside the minimum plasmapause, where BOT energy spectra mostly form in ~1–2 days as a result of hiss wave scattering. Most radiation belt electron energy spectra can be represented by one of three distributions: exponential, power law, and bump‐on‐tailExponential spectra dominate outside the plasmasphere; power law spectra often appear at high L during injections of lower‐energy electronsBump‐on‐tail spectra dominate inside the plasmasphere at L<2.5 and are caused by hiss wave scattering

Highly energetic electrons are trapped in the magnetic field of Earth’s radiation belts. The physical mechanisms driving the dynamics of the Van Allen belts can be understood from the electron’s energy spectrum, which is believed to be steeply falling with increasing energy. This view has been prevalent for the past 60 years since the energy spectra were first measured. Here, we report the observation of a reversed energy spectrum with abundant high-energy and fewer low-energy electrons spanning from hundreds of keV to around two MeV in electron energy in data collected with NASA’s Van Allen Probes. We find that this spectrum dominates inside the plasmasphere—a dense cold plasma region co-rotating with the Earth. Using two-dimensional Fokker–Planck diffusion simulations with a time-dependent, data-driven model of hiss waves in the plasmasphere, we demonstrate that the formation of the reversed spectrum is explained by the scattering of hiss waves. The results have important implications for understanding the distributions of charged particles and wave–particle interactions in magnetized plasmas throughout the solar system and beyond.

To better understand rapid enhancements of the seed populations (hundreds of keV electrons) in the heart of the Earth's outer radiation belt (L*~ 3.5–5.0) during different geomagnetic activities, we investigate three enhancement events measured by Van Allen Probes in detail. Observations of the fluxes and the pitch angle distributions of energetic electrons are analyzed to determine rapid enhancements of the seed populations. Our study shows that three specified processes associated with substorm electron injections can lead to rapid enhancements of the seed populations, and the electron energy increases up to 342 keV. In the first process, substorm electron injections accompanied by the transient and intense substorm electric fields can directly lead to rapid enhancements of the seed populations in the heart of the outer radiation belt. In the second process, the substorm injected electrons are first trapped in the outer radiation belt and subsequently transported into L*< 4.5 by the convection electric field. In the third process, the lower energy electrons are first injected at L*~ 5.3 and then undergo drift resonance with ultralow‐frequency waves. These accelerated electrons by ultralow‐frequency waves are further transported into L*< 4.5 due to the convection electric field. This process is consistent with the radial diffusion. Our results suggest that these specified processes are important for understanding the dynamics of the seed populations in the heart of the outer radiation belt. Three specified different processes can lead to rapid enhancements of the seed populations in the heart of the Earth's outer radiation beltThe resonant acceleration associated with ULF waves is important for enhancements of the seed populations in L*~ 3.5–5.0These specified processes are important for understanding the dynamics of the seed populations in L*~ 3.5–5.0

Using the electron phase space density (PSD) data measured by Van Allen Probe A from January 2013 to April 2015, we investigate the effects of magnetospheric processes on relativistic electron dynamics in the Earth's outer radiation belt during 50 geomagnetic storms. A statistical study shows that the maximum electron PSDs for various μ(μ =630, 1096, 2290, and 3311 MeV/G) at L*~4.0 after the storm peak have good correlations with storm intensity (cc~0.70). This suggests that the occurrence and magnitude of geomagnetic storms are necessary for relativistic electron enhancements at the inner edge of the outer radiation belt (L* =4.0). For moderate or weak storm events (SYM‐Hmin> ~−100 nT) with weak substorm activity (AEmax< 800 nT) and strong storm events (SYM‐Hmin≤ ~−100 nT) with intense substorms (AEmax≥ 800 nT) during the recovery phase, the maximum electron PSDs for various μat different L*values (L* =4.0, 4.5, and 5.0) are well correlated with storm intensity (cc >0.77). For storm events with intense substorms after the storm peak, relativistic electron enhancements at L* =4.5 and 5.0 are observed. This shows that intense substorms during the storm recovery phase are crucial to relativistic electron enhancements in the heart of the outer radiation belt. Our statistics study suggests that magnetospheric processes during geomagnetic storms have a significant effect on relativistic electron dynamics. The occurrence and magnitude of geomagnetic storms are necessary for relativistic electron enhancements at the inner edge of the outer radiation beltIntense substorms after the storm peak are crucial to relativistic electron enhancements in the heart of the outer radiation beltMagnetospheric processes during geomagnetic storms have a significant effect on relativistic electron dynamics

A new 3‐D diffusion code using a recently published layer method has been developed to analyze radiation belt electron dynamics. The code guarantees the positivity of the solution even when mixed diffusion terms are included. Unlike most of the previous codes, our 3‐D code is developed directly in equatorial pitch angle (α0), momentum (p), and Lshell coordinates; this eliminates the need to transform back and forth between (α0,p) coordinates and adiabatic invariant coordinates. Using (α0,p,L) is also convenient for direct comparison with satellite data. The new code has been validated by various numerical tests, and we apply the 3‐D code to model the rapid electron flux enhancement following the geomagnetic storm on 17 March 2013, which is one of the Geospace Environment Modeling Focus Group challenge events. An event‐specific global chorus wave model, an AL‐dependent statistical plasmaspheric hiss wave model, and a recently published radial diffusion coefficient formula from Time History of Events and Macroscale Interactions during Substorms (THEMIS) statistics are used. The simulation results show good agreement with satellite observations, in general, supporting the scenario that the rapid enhancement of radiation belt electron flux for this event results from an increased level of the seed population by radial diffusion, with subsequent acceleration by chorus waves. Our results prove that the layer method can be readily used to model global radiation belt dynamics in three dimensions. A 3‐D layer method code has been developed and validatedRadiation belt dynamics is modeled directly using (α0,p,L) coordinatesApplication to one storm time enhancement event supports acceleration by chorus waves

Using the particle data measured by Van Allen Probe A from October 2012 to March 2016, we investigate in detail the radiation belt seed population and its association with the relativistic electron dynamics during 74 geomagnetic storms. The period of the storm recovery phase was limited to 72 h. The statistical study shows that geomagnetic storms and substorms play important roles in the radiation belt seed population (336 keV electrons) dynamics. Based on the flux changes of 1 MeV electrons before and after the storm peak, these storm events are divided into two groups of “large flux enhancement” and “small flux enhancement.” For large flux enhancement storm events, the correlation coefficients between the peak flux location of the seed population and those of relativistic electrons (592 keV, 1 MeV, 1.8 MeV, and 2.1 MeV) during the storm recovery phase decrease with electron kinetic energy, being 0.92, 0.68, 0.49, and 0.39, respectively. The correlation coefficients between the peak flux of the seed population and those of relativistic electrons are 0.92, 0.81, 0.75, and 0.73. For small flux enhancement storm events, the correlation coefficients between the peak flux location of the seed population and those of relativistic electrons are relatively smaller, while the peak flux of the seed population is well correlated with those of relativistic electrons (correlation coefficients >0.84). It is suggested that during geomagnetic storms there is a good correlation between the seed population and ≤1 MeV electrons and the seed population is important to the relativistic electron dynamics. Geomagnetic storms and substorms play important roles in the radiation belt seed population dynamicsThe radiation belt seed population is well correlated with ≤1 MeV electronsThe radiation belt seed population is important to the relativistic electron dynamics

The aberrant expression of microRNAs (miRNAs) has emerged as an important hallmark of cancer. However, the molecular mechanisms underlying the changes in miRNA expression remain unclear. In this study, we discovered a novel epigenetic mechanism of miR-506 regulation and investigated its functional significance in pancreatic cancer. Sequencing analysis revealed that the miR-506 promoter is highly methylated in pancreatic cancer tissues compared with non-cancerous tissues. Reduced miR-506 expression was significantly associated with clinical stage, pathologic tumor status, distant metastasis and decreased survival of pancreatic cancer patients. miR-506 inhibited cell proliferation, induced cell cycle arrest at the G1/S transition and enhanced apoptosis and chemosensitivity of pancreatic cancer cells. Furthermore, we identified sphingosine kinase 1 (SPHK1) as a novel target of miR-506, the expression of which inhibited the SPHK1/Akt/NF-κB signaling pathway, which is activated in pancreatic cancer. High SPHK1 expression was significantly associated with poor survival in a large cohort of pancreatic cancer specimens. Our data suggest that miR-506 acts as a tumor suppressor miRNA and is epigenetically silenced in pancreatic cancer. The newly identified miR-506/SPHK1 axis represents a novel therapeutic strategy for future pancreatic cancer treatment.

Whistler waves are believed to play an important role during magnetic reconnection. Here we report the near-simultaneous occurrence of two types of the whistler-mode waves in the magnetotail Hall reconnection region. The first type is observed in the magnetic pileup region of downstream and propagates away to downstream along the field lines and is possibly generated by the electron temperature anisotropy at the magnetic equator. The second type, propagating toward the X line, is found around the separatrix region and probably is generated by the electron beam-driven whistler instability or Cerenkov emission from electron phase-space holes. These observations of two different types of whistler waves are consistent with recent kinetic simulations and suggest that the observed whistler waves are a consequence of magnetic reconnection. Two types of whistler waves are observed in the reconnection diffusion regionFirst one is in pileup region, and second one is around separatrixWhistlers are the consequences of magnetic reconnection

Recent test particle simulations have shown that energetic electrons traveling through fast magnetosonic (MS) wave packets can experience an effect which is specifically associated with the tight equatorial confinement of these waves, known as transit time scattering. However, such test particle simulations can be computationally cumbersome and offer limited insight into the dominant physical processes controlling the wave‐particle interactions, that is, in determining the effects of the various wave parameters and equatorial confinement on the particle scattering. In this paper, we show that such nonresonant effects can be effectively captured with a straightforward analytical treatment that is made possible with a set of reasonable, simplifying assumptions. It is shown that the effect of the wave confinement, which is not captured by the standard quasi‐linear theory approach, acts in such a way as to broaden the range of particle energies and pitch angles that can effectively resonate with the wave. The resulting diffusion coefficients can be readily incorporated into global diffusion models in order to test the effects of transit time scattering on the dynamical evolution of radiation belt fluxes. New analytical expressions have been derived for magnetosonic waves scatteringThe diffusion coefficients contain nonresonant/transit time scattering effectsThese coefficients can be directly incorporated into global diffusion codes

To effectively study loss due to hiss‐driven precipitation of relativistic electrons in the outer radiation belt, it is useful to isolate this loss by studying a time of relatively quiet geomagnetic activity. We present a case of initial enhancement and slow, steady decay of 700 keV–2 MeV electron populations in the outer radiation belt during an extended quiescent period from ∼15 December 2012 to 13 January 2013. We incorporate particle measurements from a constellation of satellites, including the Colorado Student Space Weather Experiment (CSSWE) CubeSat, the Van Allen Probes twin spacecraft, and Time History of Events and Macroscale Interactions during Substorms (THEMIS), to understand the evolution of the electron populations across pitch angle and energy. Additional data from calculated phase space density, as well as hiss and chorus wave data from Van Allen Probes, help complete the picture of the slow precipitation loss of relativistic electrons during a quiet time. Electron loss to the atmosphere during this event is quantified through use of the Loss Index Method, utilizing CSSWE measurements at low Earth orbit. By comparing these results against equatorial Van Allen Probes electron flux data, we conclude the net precipitation loss of the outer radiation belt content to be greater than 92%, suggesting no significant acceleration during this period, and resulting in faster electron loss rates than have previously been reported. Relativistic e‐lifetimes can be estimated with Loss Index MethodTotal outer belt precipitation loss in quiet time over 92%Hiss scattering gives shorter lifetimes than current theory

Wave normal distributions of lower‐band whistler‐mode waves observed outside the plasmapause exhibit two peaks: one near the parallel direction and the other at very oblique angles. We analyze a number of conjunction events between the Van Allen Probes near the equatorial plane and Polar Orbiting Environmental Satellites (POES) at conjugate low altitudes, where lower‐band whistler‐mode wave amplitudes were inferred from the two‐directional POES electron measurements over 30–100 keV, assuming that these waves were quasi‐parallel. For conjunction events, the wave amplitudes inferred from the POES electron measurements were found to be overestimated as compared with the Van Allen Probes measurements primarily for oblique waves and quasi‐parallel waves with small wave amplitudes (< ~20 pT) measured at low latitudes. This provides plausible experimental evidence of stronger pitch angle scattering loss caused by oblique waves than by quasi‐parallel waves with the same magnetic wave amplitudes, as predicted by numerical calculations. Oblique waves cause stronger pitch angle scattering than parallel waves with the same BwWe provide the evidence using conjunction events between Radiation Belt Storm Probes (RBSP) and POESBoth observational and numerical results support this scenario

Local acceleration driven by whistler‐mode chorus waves is fundamentally important for accelerating seed electron populations to highly relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus‐driven electron acceleration during the 17 March 2013 storm, when the Van Allen Probes observed very rapid electron acceleration up to several MeV within ~12 hours. A clear radial peak in electron phase space density (PSD) observed near L* ~4 indicates that an internal local acceleration process was operating. We construct the global distribution of chorus wave intensity from the low‐altitude electron measurements made by multiple Polar Orbiting Environmental Satellites (POES) satellites over a broad region, which is ultimately used to simulate the radiation belt electron dynamics driven by chorus waves. Our simulation results show remarkable agreement in magnitude, timing, energy dependence, and pitch angle distribution with the observed electron PSD near its peak location. However, radial diffusion and other loss processes may be required to explain the differences between the observation and simulation at other locations away from the PSD peak. Our simulation results, together with previous studies, suggest that local acceleration by chorus waves is a robust and ubiquitous process and plays a critical role in accelerating injected seed electrons with convective energies (~100 keV) to highly relativistic energies (several MeV). Rapid electron acceleration with a radial PSD peak is observed during a stormChorus driven electron acceleration reproduces observed electron evolutionLocal acceleration by chorus waves is a robust and ubiquitous process

Photoelectrons are produced on the dayside of Mars via solar Extreme Ultraviolet (EUV) and X‐ray ionization and are also frequently observed on the nightside as a result of field‐aligned transport. Based on the Solar Wind Electron Analyzer (SWEA) measurements made on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we show that the shape of the photoelectron energy distribution exhibits interesting cross‐terminator variations, in that the He II peak becomes less pronounced and the 10 − 50 eV smooth background becomes hardened, both more evident at lower altitudes. These observations could be understood as the outcome of “atmospheric absorption” via photoelectron collisions with ambient neutrals during day‐to‐night transport. Such a scenario could successfully interpret the diversity of the MAVEN SWEA observations such as the dawn‐dusk and north‐south asymmetries, the impacts of crustal magnetization, upstream solar wind conditions, and solar EUV and X‐ray radiation, all using the 10–50 eV spectral hardness as a diagnostic. In particular, the magnetic control of the cross‐terminator spectral reshaping is proposed as the outcome of varying day‐to‐night magnetic connectivity which naturally implies varying field‐aligned atmospheric column for “absorption.” Crude estimates suggest that an “absorbing” atmospheric column of ≈1.5 × 1015cm−2is required for a significant photoelectron spectral reshaping beyond the EUV terminator. Therefore the observations reported here may shed light on the extension of the cross‐terminator magnetic field lines, as complementary to the day‐to‐night magnetic connectivity inferred from the occurrence of nightside photoelectrons. Photoelectrons are an omnipresent population of the Martian ionosphere, which are produced exclusively on the dayside via photoionization and are also frequently observed on the nightside as a result of cross‐terminator transport. They are of broad interest because they make significant contributions to local ionization, heating, and airglow emission in the Martian upper atmosphere. In addition, the occurrence of nightside photoelectrons has been commonly used as a diagnostic of the day‐to‐night magnetic connectivity near Mars. Photoelectrons may also undergo significant spectral reshaping beyond the EUV terminator, an issue that has been paid little attention to but is potentially important for shedding light on the extension of the magnetic connectivity. This study is devoted to such a topic using SWEA measurements made on board the MAVEN spacecraft. We propose that collisions with atmospheric neutrals continuously modify the photoelectron energy distribution from a highly non‐thermal, structured one toward a thermal, featureless one. This scenario successfully interprets many aspects of the observed cross‐terminator variation, such as the dawn‐dusk and north‐south asymmetries, the impacts of crustal magnetization, upstream solar wind conditions, and solar activity. The shape of the photoelectron energy distribution varies systematically across the Martian terminatorThe variation is the direct outcome of atmospheric absorption, which is more pronounced at low altitudesBoth crustal magnetization and upstream solar wind conditions affect the variation by modifying the field‐aligned atmospheric column The shape of the photoelectron energy distribution varies systematically across the Martian terminator The variation is the direct outcome of atmospheric absorption, which is more pronounced at low altitudes Both crustal magnetization and upstream solar wind conditions affect the variation by modifying the field‐aligned atmospheric column

Insulin-like growth factor 1 (IGF-1) and its receptor (insulin-like growth factor 1 receptor, IGF1R) can regulate the extracellular matrix synthesis and play a crucial role in maintaining the normal functions of the intervertebral disc (IVD). The objective of this study was to investigate whether there would be accelerated IVD degeneration (IVDD) in IGF1R+/-mice. Three IGF1R+/-male mice and three wild-type male mice were sacrificed respectively at 6, 12, and 18 weeks after birth. Six lumbar disc samples were harvested from each mouse, with a total of 54 disc samples taken from each genotype. Histomorphological analysis for the IVD was performed to assess the degenerative extent according to the classification system proposed by Boos et al. Quantitative real-time PCR and semi-quantitative histologic scoring (HScore) for immunohistochemical staining were used to evaluate the expression level of type-II collagen, aggrecan and matrix metallopeptidase 13 (MMP-13). Histomorphological analysis for the discs revealed significantly less amounts of proteoglycan and type-II collagen, and significantly higher total degenerative score in IGF1R+/-mice than in wild-type mice. Real-time PCR showed that the mRNA expressions of type-II collagen and aggrecan in the discs were significantly lower, while MMP-13 was significantly higher in IGF1R+/-mice than in wild-type mice. The results of HScore analysis were similar to those obtained from the quantitative real-time PCR. Taken together, our study indicates that reduced expression of IGF1R would lead to accelerated degeneration of IVD. IGF1R+/-mice could be regarded as a good animal model to study IVD degeneration (IVDD), and studies on the IVD of IGF1R+/-mice could provide further insight into the pathogenesis of IVDD.

High mobility group box 1 (HMGB1), known as a pro-inflammatory cytokine and chromatin-binding molecule, plays an important role in the carcinogenesis and metastasis of various tumors. The present study aimed to investigate the expression of HMGB1 in human osteosarcoma and its clinical relevance. At first, human osteosarcom tissues and their corresponding adjacent non-cancerous tissues (ANCT) from forty consecutive cases were collected. The expression of HMGB1 was detected by immunohistochemical assay through tissue microarray procedure and the correlation of HMGB1 expression with clinicopathologic factors was evaluated. Secondly, through small hairpin RNA(shRNA)-mediated HMGB1 knockdown in MG-63 osteosarcoma cells, we observed the changes of the biological behaviors of the osteosarcoma cells. As a consequence, the rate of positive expression of HMGB1 was significantly higher in osteosarcoma tissues than in the ANCT (60% vs 15%, P< 0.01). HMGB1 expression had significant positive correlation with Ennecking staging (P= 0.034) and distant metastases (P= 0.003), but had no correlation with the factors including age and gender of the patients, or histology and location of the tumor (each P> 0.05). Knockdown of HMGB1 down-regulated the expression of p-AKT, p-PI3K, PCNA, MMP-9 and CyclinD1, while it up-regulated the expression of cleaved caspase-3. More importantly, HMGB1 knockdown inhibited the proliferative activities and invasive potential, and induced apoptosis and cycle arrest in MG63 osteosarcoma cells. Taken together, our results indicate that HMGB1 was highly expressed in human osteosarcoma tissues, and the patients with higher HMGB1 expression in osteosarcoma tissues were more likely to have progression and metastasis of the disease. Knockdown of HMGB1 could inhibit the proliferation and invasion of osteosarcoma cells and induce its apoptosis through down-regulation of PI3K/AKT signaling pathway. HMGB1 could be a potential therapeutic target for osteosarcoma.

In this paper, we address the data-driven design of observers for the process monitoring and control purposes. Instead of identifying a standard state space model, our design schemes are based on the identification of the so-called parity subspace. Two design schemes are developed, which allow a direct design of (a) observer-based fault detection systems (b) a full order observer for the estimation of the process state variables. The achieved results are illustrated by a benchmark example.

Pokemon gene has crucial but versatile functions in cell differentiation, proliferation and tumorigenesis. It is a master regulator of the ARF-HDM2-p53 and Rb-E2F pathways. The facts that the expression of Pokemon is essential for tumor formation and many kinds of tumors over-express the Pokemon gene make it an attractive target for therapeutic intervention for cancer treatment. In this study, we used an RNAi strategy to silence the Pokemon gene in a cervical cancer model. To address the issues involving tumor specific delivery and durable expression of siRNA, we applied the Arg-Gly-Asp (RGD) peptide ligand and polylysine (K18) fusion peptide to encapsulate a recombinant retrovirus plasmid expressing a siRNA targeting the Pokemon gene and produced the ‘mimoretrovirus’. At charge ratio 2.0 of fusion peptide/plasmid, the mimoretrovirus formed stable and homogenous nanoparticles, and provided complete DNase I protection and complete gel retardation. This nanoparticle inhibited SiHa cell proliferation and invasion, while it promoted SiHa cell apoptosis. The binding of the nanoparticle to SiHa cells was mediated via the RGD-integrin v3 interaction, as evidenced by the finding that unconjugated RGD peptide inhibited this binding significantly. This tumor-targeting mimoretrovirus exhibited excellent anti-tumor capacity in vivo in a nude mouse model. Moreover, the mimoretrovirus inhibited tumor growth with a much higher efficiency than recombinant retrovirus expressing siRNA or the K18/P4 nanoparticle lacking the RGD peptide. Results suggest that the RNAi/RGD-based mimoretrovirus developed in this study represents a novel anti-tumor strategy that may be applicable to most research involving cancer therapy and, thus, has promising potential as a cervical cancer treatment.

A 36-year-old man presented a sudden left occipital headache and right limb weakness after tooth-brushing. Conventional catheter digital subtraction angiography (DSA) showed a left VA occlusion at the crotch of the posterior inferior cerebellar artery. Four days later, the patient got worse. The angiogram showed the left vertebral artery had reopened and the basilar trunk occluded above the AICA. He died two days later and autopsy demonstrated a dissection of the basilar arteries. Based on the autopsy data from the patient in this study, we suggest that the BA dissection might be due to left VA dissection, and placing a stent on the juncture between the uninjured VA and the basilar trunk might be an effective method to prevent fatal BA occlusion.

Abstract: This is the second part of a paper which deals with the advantages and disadvantages of relative instrumental neutron activation analysis concerning traceability and uncertainty, and the current scope and possible future extensions of neutron activation analysis as a primary ratio method. The first part of this paper has been published in this Journal [1].

The modification of bundled single-walled and multiwalled carbon nanotubes is examined using a combination of computational and experimental methods. The computational approach is classical molecular dynamics simulations using the many-body reactive empirical bond-order potential parametrized by Brenner. The simulations consider the deposition of CH3⁺ at incident energies of 10, 45, and 80 eV. They predict the chemical functionalization of the nanotubes, the formation of defects on the nanotube walls, and the formation of cross-links between neighboring nanotubes or between the walls of a single nanotube. They also illustrate the manner in which the number of walls in the nanotube and incident energy affect the results. In the experiments, multiwalled nanotubes with about 40 shells (average diameter of 25 nm) are synthesized by chemical vapor deposition. CF3⁺ ions are deposited at incident energies of 10 and 45 eV, and then the nanotubes are examined with X-ray photoelectron spectroscopy and scanning electron microscopy. These experiments find strong evidence of chemical functionalization, in agreement with the simulation results.

There are four different kinds of scratch morphologies developed when a blunt spherical stylus is in contact with the surface of a polymer multilayer system in relative motion. Qualitatively, a relationship between scratch morphologies and mechanisms can be established. The main deformation mechanisms are surface shear yielding, surface cracking, subsurface yielding (indentation), and interfacial delamination. Tangential forces during scratching using a blunt spherical stylus are largely due to the friction between materials and the stylus. In that sense, lubricants can improve the material scratch performance by reducing the friction force at a given normal load. Many variables, such as scratching speed, environments, and the sizes of styli, can affect polymer scratching performances to a large degree.

Abstract: This paper deals with the mechanisms of localization of Franck-Condon vibronic coupling of πσ*- or πlπ*-orbital type in a few vibrational modes, (LVM) in excited electronic states of polyatomic molecules. The analysis of vibronic coupling uses highly symmetric basis sets (for representing MO structures and normal coordinates ξR) as well as simplified models that relate the shift ΔR of the electron potential minima along the normal coordinates to the MO structure and to ξR in the form of analytical expressions. The modes that are active in LVM are determined from the experimental luminescence spectra. These ideas about approximately high local symmetry of vibronic coupling in benzene fragments as well as the estimates of ΔR depending on variations in the MO structure explain the experimental results.

Abstract: This paper studies changes in the matrix elements (Ump) of spin-orbit coupling between the nπ*- and ππ*-states, which are induced by the (“chair,” “bath”) distortions of the nuclear configurations of molecules. The analysis is performed for acridine molecules in which the n-pz atomic orbital (AO) of the heteroatom is directed along the C2 symmetry axis. Earlier, for molecules with a planar nuclear configuration of C2v symmetry and with the heteroatom lying on the C2 axis, we established the dependence of Ump on the symmetry of ππ*-states [Γ(ππ*)=A1 or B2]. The values of Ump differ by more than one order of magnitude; this is in line with the difference between the interconversion rate constants (Kisc; two or three orders). In this work we have found that this contrast in Ump (and, accordingly, in Kisc) is retained when the nuclear configuration of the acridine molecule is distorted to the “chair” (AC-A) configuration, although the individuality of both molecular orbital types (nσ-MO and π-MO) and states nπ* and ππ* is annihilated to a certain extent. For the “bath” (AC-B) conformation the difference in Ump considerably diminishes. Reasons for the changes in the matrix elements of spin-orbit coupling and rate constants of the S-T conversion are analyzed. The available energy level diagram is critically analyzed, and a slightly different diagam as well as a scheme of nonradiating deactivation of acridine are suggested.

Abstract: Oxygen and fluorine have been simultaneously determined by 14-MeV INAA in samples containing boron. Both boron and fluorine can cause serious interferences in the determination of oxygen. The fluorine and boron interference corrections for oxygen determination have been determined to be 0.43±0.01 and 0.0832±0.0017 apparent g oxygen per g of fluorine and boron, respectively, for our system. Boron can be determined in the same sample by a second irradiation. Mutual interferences have been evaluated and the procedure has been applied to NIST SRM and several other compounds.

Abstract: Reactor thermal neutron irradiation of biological matrices induces high levels of intense gamma-ray or bremsstrahlung radiation from82Br,42K,24Na, and32P, that interfere with the determination of As, Cd, Cu, and Mo by INAA. Central nervous system (CNS) issue samples from subjects with Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and controls were analyzed using a simple RNAA procedure involving a rapid two-step solvent extraction procedure to determine these four elements. Significant increases (ple0.05) in concentrations of Cd and Mo were observed for brain of AD subjects compared to controls, but significant imbalances were not observed for ALS subjects. Concentration data for these elements in selected international reference standards are also presented.

Abstract: A 14-MeV FNAA system for oxygen analysis has been developed in which both data collection and processing are controlled by a PC-type computer equipped with an ORTEC ACETM-MCS multichannel scaler card. A single loop pneumatic transfer system automatically moves samples to the irradiation position and returns them to a counting position between two NaI(Tl) detectors operated through a summing amplifier. Software for data processing has been developed. Dead times of the BF3 neutron monitor and gamma-ray counting system have been separately determined. Results are presented for a variety of standard samples.

Responses of net photosynthesis (A), leaf conductance to water vapor (g(wv)) and instantaneous water use efficiency (WUE) to decreasing leaf and soil water potentials (Psi(l), Psi(s)) were studied in three-month-old white oak (Quercus alba L.), post oak (Q. stellata Wangenh.), sugar maple (Acer saccharum Marsh.), and black walnut (Juglans nigra L.) seedlings. Quercus seedlings had the highest A and g(wv) when plants were well watered. As the soil was allowed to dry, both A and g(wv) decreased; however, trace amounts of A were observed at a Psi(l) as low as -2.9 MPa in Q. stellata and -2.6 MPa in Q. alba and A. saccharum. Photosynthesis was not measurable at Psi(l) lower than -2.2 MPa in J. nigra and water stress-induced leaflet senescence was observed in this species. Within each species, g(wv) showed a similar relationship to soil and leaf Psi, but the response to Psi(l) was shifted to more negative values by 1.2 to 1.6 MPa. As Psi(s) declined below -1 MPa, the difference between soil and leaf Psi diminished because of the suppression of transpiration. There was no indication that Psi(s) had a more direct influence on g(wv) than did Psi(l). Water use efficiency showed an initial increase as the soil dried, followed by a decline under severe water stress. Water use efficiency was highest in J. nigra, intermediate in Quercus species and lowest in A. saccharum. There was an evident relationship between gas exchange characteristics and natural distribution in these species, with the more xeric species showing higher A and g(wv) under both well-watered and water-stressed conditions. There was no trend toward increased efficiency of water use in the more xeric species.

Abstract: It has been suggested that several age-related neurological diseases such as Alzheimer's disease and amyotrophic lateral sclerosis may be related to environmental toxins. Bulk sample multielement analyses by INAA alone are not adequate to define the role of trace elements in these diseases. A multitechnique approach has been developed that incorporates 14 MeV, instrumental reactor, radiochemical, and pre-irradiation chemical neutron activation analysis, together with laser microprobe mass spectrometry. The analytical scheme is able to provide bulk or protein normalized elemental concentrations, as well as microstructural, cellular, and subcellular localization information.

We have isolated a brain-specific cDNA that encodes a Na(+)-dependent inorganic phosphate (Pi) cotransporter (BNPI). The nucleotide sequence of BNPI predicts a protein of 560 amino acids with 6-8 putative transmembrane-spanning segments that is approximately 32% identical to the rabbit kidney Na(+)-dependent Pi cotransporter. Expression of BNPI mRNA in Xenopus oocytes results in Na(+)-dependent Pi transport similar to that reported for the recombinantly expressed or native kidney Na(+)-dependent cotransporter. RNA blot analysis reveals that BNPI mRNA is expressed predominantly (if not exclusively) in brain, and in situ hybridization histochemistry reveals BNPI transcripts in neurons of the cerebral cortex, hippocampus, and cerebellum. Furthermore, we have confirmed the presence of saturable Na(+)-dependent Pi cotransport in cultured cerebellar granule cells. Together, these data demonstrate the presence of a specific neuronal Na(+)-dependent transport system for Pi in brain.

Metal cations are known to be required for proton pumping by bacteriorhodopsin (bR). Previous studies found that bR has two high-affinity and four to six low-affinity Ca(2+)-binding sites. In our efforts to find the location of these Ca2+ sites, the effects of replacing charged (Asp-85, Asp-212, and Arg-82) and H-bonding (Tyr-185) residues in the retinal pocket on the color control and binding affinity of Ca2+ ions in Ca(2+)-regenerated bR were examined. The important results are as follows: (i) The removal of Ca2+ from recombinant bR in which charged residues were replaced by neutral ones shifted the retinal absorption to the blue, opposite to that observed in wild-type bR or in recombinant bR in which the H-bonding residue, Tyr-185, was replaced by a non-H-bonding amino acid (Phe). (ii) Similar to the observation in wild-type bR, the binding of Ca2+ to the second site gave the observed color change in the recombinant bR samples in which charged residues were replaced by neutral ones. (iii) The residue replacements had no effect on the affinity constants of the four to six weakly bound Ca2+. (iv) The two high-affinity sites exhibited reduced affinity with substitutions; while the extent of the reduction depended on the specific substitution, each site was reduced by the same factor for each of the charged residue substitutions but by different factors for the mutant where Tyr-185 was replaced with Phe(Y185F). The above results suggest that the two Ca2+ ions in the two high-affinity sites are within interaction distance with one another and with the charged residues in the retinal pocket. The results further suggest that, while the interaction between Tyr-185 and the high-affinity Ca2+ ions is relatively short range and specific (with more coupling to the Ca2+ ion in the second affinity site), between the charged residues and Ca2+ ions it seems to be of the electrostatic (e.g., ion-ion) long range, nonspecific type. Although neither Asp-85, Asp-212, nor Arg-82 is individually directly involved in the binding of Ca2+ in these two sites, they might all participate in it. Together with the protonated Schiff base, the charged residues along with Tyr-185 and one or two Ca2+ ions (and probably a few water molecules) seem to form an electrostatically coupled system that is part of a cavity that controls the color and function of bR.

Mal63p is a transcriptional activator for maltose fermentation in Saccharomyces cerevisiae. We have purified it to homogeneity from a yeast strain in which the MAL63 gene is under the control of the GAL1–GAL10 promoter. Purification included fractionation of a whole-cell extract by ion-exchange chromatography, chromatography using both non-specific DNA-affinity (calf thymus), and sequence-specific DNA-affinity chromatography. Mal63p activity was assayed by its binding to a fragment of the MAL61–MAL62 promoter, using both filter-binding and electrophoretic-mobility shift assays. DNase-I footprinting identified a new binding site (site 3) between the two previously known sites (sites 1 and 2). Mal63p is a dimer, and methylation-protection experiments identify the recognition motif as: c/a GC N9 c/a GC/g.

Postoperative radiculopathy is a complication of posterior cervical decompression associated with tethering of the nerve root. We reviewed retrospectively 287 consecutive patients with cervical compression myelopathy who had been treated by multilevel cervical laminectomy and identified 37 (12.9%) with postoperative radiculopathy. There were 27 men and ten women with a mean age of 56 years at the time of operation. The diagnosis was either cervical spondylosis (25 patients) or ossification of the posterior longitudinal ligament (12 patients).Radiculopathy was observed from four hours to six days after surgery. The most frequent pattern of paralysis was involvement of the C5 and C6 roots of the motor-dominant type. The mean time for recovery was 5.4 months (two weeks to three years). The results at follow-up showed that the rate of motor recovery was negatively related to the duration of complete recovery of postoperative radiculopathy (? = -0.832, p < 0.01) and that patients with spondylotic myelopathy had a significantly better rate of clinical recovery than those with ossification of the posterior longitudinal ligament (t = 2.960, p < 0.01).Postoperative radiculopathy may be prevented by carrying out an anterior decompression in conjunction with spinal fusion, which will achieve stabilisation and directly remove compression of the cord at multiple levels.

Lumbar spinal stenosis and lumbar disc herniation are usually regarded as two pathogenetically different conditions, but in the literature lumbar disc herniation in patients with developmental spinal stenosis has been rarely documented. In a clinical retrospective study, 42 lumbar disc herniations with developmental spinal stenosis were reported and analyzed. Discectomy was performed after laminotomy. The patients were followed-up for an average of 4.4 years (range 2–7 years). The preoperative symptoms disappeared completely in 28 patients, in 13 patients some degree of backache remained although their nerve root pain had been relieved, and in 1 patient intermittent claudication reappeared after 6 years resolution of their preoperative pain. We conclude that when developmental spinal stenosis is combined with disc herniation, discectomy through laminotomy rather than laminectomy is usually sufficient for decompression.

A new application of bender elements to measure the small strain shear modulus of sand in multiple shear planes under anisotropic loading is developed. The tests were conducted in a specially designed oedometer with the side of the ring smoothed by a Teflon sheet. The soil used in the tests is clean angular pool filter sand. The effects of size of bender elements on the results of shear wave velocity measurement are discussed. Shear modulus in four different shear planes during a loading-unloading cycle is presented. The results of experiments are compared with the Hardin-Blanford equation on Gmax, which shows good agreement. The influence of side friction of the oedometer is investigated.

Maltose fermentation in Saccharomyces species requires the presence of at least one of five unlinked MAL loci: MAL1, MAL2, MAL3, MAL4, and MAL6. Each of these loci consists of a complex of genes involved in maltose metabolism; the complex includes maltase, a maltose permease, and an activator of these genes. At the MAL6 locus, the activator is encoded by the MAL63 gene. While the MAL6 locus has been the subject of numerous studies, the binding sites of the MAL63 activator have not been determined. In this study, we used Escherichia coli extracts containing the MAL63 protein to define the binding sites of the MAL63 protein in the divergently transcribed MAL61-62 promotor. When a DNA fragment containing these sites was placed upstream of a CYC1-lacZ gene, maltose induced beta-galactosidase. These sites therefore constitute an upstream activating sequence for the MAL genes.

Despite produced exclusively on the dayside, photoelectrons, as an important population of the Martian ionosphere, have also been observed on the nightside. Here we present a statistical survey of nightside photoelectrons using the suprathermal electron measurements, made by the Solar Wind Electron Analyzer onboard the Mars Atmosphere and Volatile Evolution. We find that nearly 30% of the available nightside suprathermal electron spectra show clear photoelectron signatures. Nightside photoelectrons have an occurrence rate that decreases with increasing solar zenith angle and they are characterized by a preferentially field‐aligned pitch angle distribution. Our analysis also suggests that nightside photoelectrons are less likely observed under the high solar wind condition. These observations are favorably interpreted by the scenario of photoelectron transport along cross‐terminator magnetic field lines, as supported by a simplified test particle model. Our study highlights a complex plasma environment near Mars modulated by both internal and external conditions. Photoelectrons are an important population of a planetary upper atmosphere that plays a crucial role in ionization, heating, radiation, and escape. Despite that photoelectrons are ideally produced by solar radiation on the dayside only, they have also been observed on the nightside of a planet such as Mars. This study is devoted to a statistical survey of photoelectrons in the nightside Martian upper atmosphere, based on the state‐of‐the‐art measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. A surprisingly large fraction of photoelectron energy spectra is identified on the nightside of Mars, occupying nearly 30% of the available nightside measurements. Meanwhile, substantial variations in the observations of nightside photoelectrons are suggested by the data, revealing that (1) their occurrence rate declines rapidly near and beyond the terminator; (2) their velocities are more likely parallel to the ambient magnetic field lines; and (3) they are less likely observed under high solar wind dynamic pressures. These observations could be interpreted by photoelectron transport along large‐scale magnetic field lines from their dayside source regions to the nightside, a scenario that is controlled by both internal and external conditions and thus provides a useful diagnostic of the ambient magnetic field configuration. The photoelectron occurrence rate in the nightside Martian ionosphere decreases with increasing solar zenith angleNightside photoelectrons are observed to be preferentially field‐aligned, as a natural result of cross‐terminator transportNightside photoelectrons are more likely observed under low solar wind dynamical pressures The photoelectron occurrence rate in the nightside Martian ionosphere decreases with increasing solar zenith angle Nightside photoelectrons are observed to be preferentially field‐aligned, as a natural result of cross‐terminator transport Nightside photoelectrons are more likely observed under low solar wind dynamical pressures

Developing cost-effective electrocatalysts for electrochemical water splitting (EWS) is appealing and challenging for sustainable water electrolysis. Currently, nickel sulfides are considered as promising candidates for EWS due to their low cost and high catalytic activity. However, the facile design of nickel sulfides with high catalytic performance is still highly demanded. In this study, we have developed a one-step solvothermal strategy to construct nickel sulfides as efficient water splitting catalysts. By taking advantage of the small size, abundant active sites, large electrochemical surface area, and good conductivity, the nanoworm-like nickel sulfides (NiS-NW/Ni foam [NF]) exhibit better oxygen evolution reaction performance (a low overpotential of 279 mV to achieve 100 mA cm−2, Tafel slope of 38.44 mV dce−1) than the nanoplate-like analogs, as well as most of reported nickel sulfide–based electrocatalysts. In addition, the NiS-NW/NF directly used as bifunctional electrodes for overall water splitting requires a low voltage of 1.563 V to attain a current density of 10 mA cm−2with good long-term durability. This work provides a facile strategy for the design of efficient nickel sulfide-based electrocatalysts for energy conversion applications.