Numerical assessment of hydrodynamic and mixing characteristics for mixed electroosmotic and pressure-driven flow through a wavy microchannel with patchwise surface heterogeneity

The micromixing of two fluids plays a vital role in lab-on-a-chip devices. For obtaining better mixing efficiency, we propose a micromixer using patchwise surface potential heterogeneity and wavy wall. We numerically investigate the hydrodynamic and mixing characteristics for flow through a microchannel with a straight top wall and wavy bottom wall. The primary flow is actuated by an external pressure-gradient and patches are placed at the top wall with positive zeta potential, such that the reversed electroosmotic actuation forms the recirculation zones close to the top wall. The streamlines, flow velocity, recirculation zone velocity, species concentration, flow rate, and mixing efficiency are investigated by varying the relative pressure-gradient strength, Debye parameter, zeta potential and wavy surface amplitude. Two different configurations are considered by placing the patches at the top wall, opposite to the peaks and valleys of the bottom wavy surface, respectively. It reveals that the recirculation zone velocity increases with the increase in both Debye parameter and surface amplitude, whereas it decreases with relative pressure-gradient strength near the patch surfaces. The flow rate decreases with the increase in zeta potential and we also identify the values of zeta potential for chocking of flow in the microchannel. It reveals that the mixing efficiency monotonically increases with surface amplitude, and the variation with zeta potential is non-monotonic. We also identify the range of zeta potential for which the value of mixing efficiency is higher than 90% for different configurations of the channel.

Energy Loss in Steep Open Channels with Step-Pools

Three-dimensional numerical simulations were performed for different flow rates and various geometrical parameters of step-pools in steep open channels to gain insight into the occurrence of energy loss and its dependence on the flow structure. For a given channel with step-pools, energy loss varied only marginally with increasing flow rate in the nappe and transition flow regimes, while it increased in the skimming regime. Energy loss is positively correlated with the size of the recirculation zone, velocity in the recirculation zone and the vorticity. For the same flow rate, energy loss increased by 31.6% when the horizontal face inclination increased from 2° to 10°, while it decreased by 58.6% when the vertical face inclination increased from 40° to 70°. In a channel with several step-pools, cumulative energy loss is linearly related to the number of step-pools, for nappe and transition flows. However, it is a nonlinear function for skimming flows.

Advantages and Limitations of Seismic Refraction Method Using Hammer Sources

The seismic refraction surveying method uses seismic energy that returns to the surface after traveling through the ground along refracted ray paths. The first arrival of seismic energy at a detector offset from a seismic source always represents either a direct ray or a refracted ray. This fact allows simple refraction surveys to be performed in which attention is concentrated solely on the first arrival (or onset) of seismic energy, and timedistance plots of these first arrivals are interpreted to derive information on the depth to refracting interfaces. this simple approach does not always yield a full or accurate picture of the subsurface. In such circumstances more complex interpretations may be applied. The method is normally used to locate refracting interfaces (refractors) separating layers of different seismic velocity, but the method is also applicable in cases where velocity varies smoothly as a function of depth or laterally.Despite the numerous limitation of hammer seismic refraction survey, the technique is still very much in use due to the various aspects in which it is found advantageous. The most pronounce advantage of the refraction method is that it gives directly the velocities of the refracting beds. Which are needed in the depth interpretation. This this work reveals that even though there are several problem of this technique, there are also a lot of advantages, one of which is that it is the most readily available seismic energy source we can lay hands on.Hammer source is a low energy source whose use is restricted to shallow survey. Due to weak energy generated,only the first few layers of the ground subsurface can be detected. It provides only the picture of the bedrock configuration. When there arises problems such as noise, irregularities in the shallow bedrock surface or eroded and weathered rock surface, anisotropic surface, existence of blind zone, velocity reversal with depth, and when the boundary between the interfaces are non-parallel, then correction measures are necessary to improve on the results obtained. Ambiguities do occur in this technique hence it requires thought, care, a high degree of skill and a good sense of judgment.These shortcomings are not enough to dismiss the use of the hammer source in seismic refraction method as its results has been shown to be useful in solving civil engineering and hydrogeological problems. The method is economical in cost, time and area of coverage. It poses no danger to the environment to which the work is done, or neither personnel nor damage to instruments used. This work has not only enumerated the limitations and advantages of seismic refraction method using hammer source but has also made suggestions to aid in the basic problem of the method, like dipping layers, blind zone, velocity inversion occurrence and noise control.

Determination of vadose and saturated-zone nitrate lag times using long-term groundwater monitoring data and statistical machine learning

In this study, we explored the use of statistical machine learning and long-term groundwater nitrate monitoring data to estimate vadose-zone and saturated-zone lag times in an irrigated alluvial agricultural setting. Unlike most previous statistical machine learning studies that sought to predict groundwater nitrate concentrations within aquifers, the focus of this study was to leverage available groundwater nitrate concentrations and other environmental variable data to determine mean vertical velocities (transport rates) of water and solutes in the vadose zone and saturated zone (3.50 m/year and 3.75 m/year, respectively). Although a saturated-zone velocity that is greater than a vadose-zone velocity would be counterintuitive in most aquifer settings, the statistical machine learning results are consistent with two contrasting primary recharge processes in this aquifer: (1) diffuse recharge from irrigation and precipitation across the landscape, and (2) focused recharge from leaking irrigation conveyance canals. The vadose-zone mean velocity yielded a mean recharge rate (0.46 m/year) consistent with previous estimates from groundwater age-dating in shallow wells (0.38 m/year). The saturated zone mean velocity yielded a recharge rate (1.31 m/year) that was more consistent with focused recharge from leaky irrigation canals, as indicated by previous results of groundwater age-dating in intermediate-depth wells (1.22 m/year). Collectively, the statistical machine-learning model results are consistent with previous observations of relatively high-water fluxes and short transit times for water and nitrate in the aquifer. Partial dependence plots from the model indicate a sharp threshold where high groundwater nitrate concentrations are mostly associated with total travel times of seven years or less, possibly reflecting some combination of recent management practices and a tendency for nitrate concentrations to be higher in diffuse infiltration recharge than in canal leakage water. Limitations to the machine learning approach include potential non-uniqueness when comparing model performance for different transport rate combinations and highlight the need to corroborate statistical model results with a robust conceptual model and complementary information such as groundwater age.

VULNERABILITY INDEX ASSESSMENT USING NEURAL NETWORKS (VIANN): A CASE STUDY OF NICOSIA, CYPRUS

Many scholars have used microtremor applications to evaluate the vulnerability index. In order to reach fast and reliable results, microtremor measurement is preferred as it is a cost-effective method. In this paper, the vulnerability index will be reviewed by utilization of microtremor measurement results in Nicosia city. 100 measurement stations have been used to collect microtremor data and the data were analysed by using Nakamura’s method. The value of vulnerability index (Kg) has been evaluated by using the fundamental frequency and amplification factor. The results obtained by the artificial neural network (ANN) will be compared with microtremor measurements. Vulnerability Index Assessment using Neural Networks (VIANN) is a backpropagation neural network, which uses the original input microtremor Horizontal Vertical Spectrum Ratio (HVSR) spectrum set. A 3-layer back propagation neural network which contains 4096 input, 28 hidden and 3 output neurons are used in this suggested system. The output neurons are classified according to acceleration sensitivity zone, velocity zones, or displacement zones. The sites are classified by their vulnerability index values using binary coding: [1 0 0] for the acceleration sensitive zone, [0 1 0] for the velocity sensitive zone, and [0 0 1] for the displacement sensitive zone.

Human CAR Gene Expression in Nonpermissive Hamster Cells Boosts Entry of Type 12 Adenovirions and Nuclear Import of Viral DNA

ABSTRACT Adenovirus type 12 (Ad12) propagation in hamster BHK21 cells is blocked prior to viral DNA replication. The amounts of Ad12 DNA in the nuclei or cytoplasm of hamster cells are about 2 orders of magnitude (2 h postinfection [p.i.]) and 4 to 5 orders of magnitude (48 h p.i.) lower than in permissive human cells. Cell line BHK21-hCAR is transgenic for and expresses the human coxsackie- and adenovirus receptor (hCAR) gene. Nuclear uptake of Ad12 DNA in BHK21-hCAR cells is markedly increased compared to that in naïve BHK21 cells. Ad12 elicits a cytopathic effect in BHK21-hCAR cells but not in BHK21 cells. Quantitative PCR or [3H]thymidine labeling followed by zone velocity sedimentation fails to detect Ad12 DNA replication in BHK21 or BHK21-hCAR cells. Newly assembled Ad12 virions cannot be detected. Thus, the block in Ad12 DNA replication in hamster cells is not released by enhanced nuclear import of Ad12 DNA.

A structural glaciological analysis of the 2002 Larsen B ice-shelf collapse

This study provides a detailed structural glaciological analysis of changes in surface structures on the Larsen B ice shelf on the Antarctic Peninsula prior to its collapse in February–March 2002. Mapped features include the ice-shelf front, rifts, crevasses, longitudinal linear surface structures and meltwater features. We define domains on the ice shelf related to glacier source areas and demonstrate that, prior to collapse, the central Larsen B ice shelf consisted of four sutured flow units fed by Crane, Jorum, Punchbowl and Hektoria/Green/Evans glaciers. Between these flow units were ‘suture zones’ of thinner ice where the feeder glaciers merged. Prior to collapse, large open-rift systems were present offshore of Foyn Point and Cape Disappointment. These rifts became more pronounced in the years preceding break-up, and ice blocks in the rifts rotated because of the strong lateral shear in this zone. Velocity mapping of the suture zones indicates that the major rifts were not present more than about 20 years ago. We suggest that the ice shelf was preconditioned to collapse by partial rupturing of the sutures between flow units. This, we believe, was the result of ice-shelf front retreat during 1998–2000, reducing the lateral resistive stress on the upstream parts of the shelf and glacier flow units, ice-shelf thinning and pre-shelf-break-up glacier acceleration.