Creation Of Holes Research Articles

Immobilized Ag-nanoparticles (iNPs) for environmental applications: Elucidation of immobilized silver-induced inhibition mechanism of Escherichia coli

Although silver nanoparticles (AgNPs) appear to be promising for certain medical/pharmaceutical applications, they present significant disadvantages when it comes to environmental applications due to the need for recovery of the metal (Ag) which is considered hazardous for the environment. The present study examines the antimicrobial properties and mechanism of action of immobilized (on Al2O3) silver nanoparticles’ (1 wt% Ag-iNPs) regarding the treatment of E. coli microbial solutions. Antimicrobial experiments were conducted in semi-batch mode using a three-phase continuous flow stirred tank reactor. Every treated sample was taken from the outlet of the reactor for the time intervals of 0, 5 and 25 min. To ensure that the bactericidal property of Ag-iNPs is not attributed to the dissolution of surface silver (as free Ag+), a suitable Ag+ scavenger was used as already described in our earlier studies. Regarding the molecular analysis performed under this study, the regulation of key enzymes involved in bactericidal activity of E. coli, was examined, after their treatment either with immobilized silver nanoparticles (Ag-iNPs) or AgNO3. Specifically, 50 mL sample for each case was centrifuged (10 min at 10,000 rpm) and the pellet (≈109 cells) was immediately subjected to total RNA extraction. For real-time RT-qPCR analyses, 1 μg of total RNA was converted into cDNA. It was found that PldA gene, which encodes outer membrane’s phospholipase A (OMPLA), was up-regulated after 5 and 25 min of treatment with Ag-iNPs. OMPLA’s activation appears to be the initial step of Ag-iNPs bactericidal mechanism that ultimately leads to the creation of holes on the outer membrane (OM), irreversibly disturbing the cells’ respiration cycle. In addition, after treatment with Ag-iNPs, Blue copper oxidase CueO (encoded by cueO gene) was found to be over-produced and appears to play a key-role in the oxidative transfer of silver from the surface of Ag-iNPs to the cell. This leads to the Ag-induced displacement of copper from its native protein sites such as CusS/CusR, a fact that causes the release of labile copper and ROS inside the cell. In addition, TEM analysis of bacteria treated with Ag-iNPs revealed severe morphological changes (“holes”) on bacterial outer membrane, indicating that there is an intermediate step in the proposed antimicrobial mechanism which takes place on the surface of Ag-iNPs.

Optical Mapping of Nonequilibrium Charge Carriers

We investigate the energy relaxation segmentation in a resonant tunneling heterostructures by assessing the optical and transport dynamics of non-equilibrium charge carriers. The electrical and optical properties are analyzed using electronic transport measurements combined with electro- and photoluminescence spectroscopies in continuous-wave mode. The radiative recombination is mainly governed by the creation of heavy holes \textit{via} impact ionization processes. Our results suggest hot electrons and holes populations form independent non-equilibrium systems that do not thermalize among them and with the lattice. Consequently, the carriers effective temperature changes independently at different regions of the heterostructure, with a population distribution for holes colder than for electrons.

Identification of Auger mechanisms responsible for low energy electron emission from graphene on copper using Auger-gamma coincidence spectroscopy

We have applied positron annihilation induced Auger-gamma coincidence spectroscopy to identify important mechanisms responsible for the emission of low energy electrons following the sudden creation of holes in bilayer graphene on copper substrate. The novel surface spectroscopic method measures the energy of the Doppler shifted annihilation gamma photon in coincidence with the Auger electron emitted following the relaxation of the hole created by the annihilation of a surface electron with a surface trapped positron. By extracting and theoretically modelling the annihilation gamma spectra coincident with low energy electrons, we associate majority of the intensity in the low energy (7 eV–25 eV) region of the Auger spectrum to electron emission following Auger decays of 2s holes in adsorbed oxygen and deep valence holes in graphene. We provide additional support to this conclusion by showing that most of the Auger electrons with energy less than ∼ 25 eV are coincident with gamma photons with small Doppler shift (511 keV–512 keV) indicating that the primary electron whose annihilation resulted in low energy Auger electron emission had small momentum parallel to the gamma emission direction. On the other hand, majority of the Auger electrons measured in coincidence with the photons having maximum Doppler shift (515 keV–521 keV) were emitted following the decay of core holes (C 1s and O 1s). By selecting annihilation gamma photons coincident only with the O KVV (from surface adsorbed oxygen), C KVV (graphene), and Cu MVV (copper substrate) Auger electrons, we have also experimentally derived the energy spectrum of Doppler shifted gamma photons resulting from the annihilation of positrons with 1s electrons of O, 1s electrons of C and 3p electrons of Cu respectively. Model Doppler broadened gamma spectra produced using ab-initio calculations agree well with the experimentally derived line shapes. This demonstrates the ability of Auger-gamma coincidence method to experimentally resolve the Doppler broadened annihilation gamma spectrum from surfaces into its veiled electronic level constituents which has, heretofore, relied solely on theoretical analysis. Our results also demonstrate that the line shape of the Doppler broadened annihilation gamma peak reflect the chemical composition of the topmost atomic layer and can thus be used to characterize both external and inaccessible surfaces of porous materials.

Parametric analysis of hole circularity for laser percussion drilling of carbon fibre reinforced plastic using Nd: YAG laser

Holes of diameter less than 1 mm has wide application of manufacturing sector. Laser beam can be conveniently used for creation of such hole in different materials. The Carbon Fiber Reinforced Composite (CFRP) is quickly replacing the conventional materials in most of the engineering applications. Therefore, a detail parametric study to analyse the influence of factors like laser current, laser interaction time, pressure of assist gas, workpiece thickness and incidence angle on the geometrical accuracy of hole in terms of hole circularity at top (HCT) has been explored by changing the individual contributing factors. Small holes (< 1mm) have been fabricated with Nd: YAG laser of millisecond pulse duration in CFRP workpiece of thickness 1mm, 3mm, and 5 mm. It was observed that hole circularity at top surface is highest for zero angle of incidence. The increase of laser current, interaction time, and pressure of assist gas increases the HCT when the laser direction is normal to the workpiece whereas it shows a decline trend when the angle of incidence of 10° and 20°g;. The increase of workpiece thickness reduces the HCT irrespective of angle of incidence.

A novel scheme for mitigation of energy hole problem in wireless sensor network for military application

SummaryWireless Sensor Networks (WSNs) have been widely considered as one of the most important technologies with unique characteristics designed for various applications. However, one of the major problems in WSNs is a limited lifetime. The creation of an energy hole near the sink has been a chief concern for researchers working to mitigate the lifetime problem. The data transmission in a multi‐hop network, as used for military purposes, follows a many‐to‐one pattern resulting in a heavier traffic load for nodes near to sink. Hence, these nodes deplete energy very soon resulting in a vacuum of energy and breakage of the network. This article aims to mitigate the energy hole problem (EHP) by implementing a corona‐based model in a clustered network. Here the cluster head selection is regularized by preferring the outer corona nodes over the inner ones. As a result, the energy balances evenly in the network with fewer loads to the nodes nearer to the sink. The distance between the sending node and the sink is evaluated to estimate the required energy for transmission. Only when a node has energy more than the required value, it is allowed to transmit, or else it turns off the radio to save energy. The proposed model is implemented in both homogeneous and heterogeneous networks and better network performance is observed.

Crystal structure and Cu/Fe K-edge analysis of Ba0.5Sr0.5Fe1-xCuxO3-δ (x = 0–0.2) and the influence on conductivity

Ba0.5Sr0.5Fe(1-x) CuxO3-δ (BSFC-x; x = 0–0.2) was synthesized and characterized. A sol-gel self-combustion method with mixed cation nitrate solutions and citric acid was used to synthesize BSFC-x precursors. Calcination was conducted in air at 850 °C for 6 h, followed by sintering in air at 1100 °C for 6 h. The phase, structure, and lattice parameters of the sintered BSFC-x were determined by X-ray diffraction (XRD). X-ray absorption near-edge spectroscopy (XANES) was used to analyze the oxidation state of the cation in the octahedron site (Cu/Fe). It showed that copper's oxidation state was predominantly 3+ due to oxygen octahedron neighbors in the crystalline symmetry and shifted to a lower oxidation state at 800 °C. The oxidation state was thought to be the predominant factor contributing to the overall conductivity through hole creation. The electrical analysis demonstrated semiconductor behavior at up to 500 °C that was influenced by the hole concentration, oxygen vacancies, and hopping distance. Above the maximum conductivity values, oxygen losses dominated the electrical response and disrupted the conductivity. Considering the doping quantity, the optimum doping was x = 0.1 with an electrical conductivity of ≈60 S/cm.

Molecular Modes of Attosecond Charge Migration.

First-principles calculations are employed to elucidate the modes of attosecond charge migration (CM) in halogenated hydrocarbon chains. We use constrained density functional theory (DFT) to emulate the creation of a localized hole on the halogen and follow the subsequent dynamics via time-dependent DFT. We find low-frequency CM modes (∼1 eV) that propagate across the molecule and study their dependence on length, bond order, and halogenation. We observe that the CM speed (∼4 Å/fs) is largely independent of molecule length, but is lower for triple-bonded versus double-bonded molecules. Additionally, as the halogen mass increases, the hole travels in a more particlelike manner as it moves across the molecule. These heuristics will be useful in identifying molecules and optimal CM detection methods for future experiments, especially for halogenated hydrocarbons which are promising targets for ionization-triggered CM.

Structural Changes Induced by Heating in Sputtered NiO and Cr2O3 Thin Films as p-Type Transparent Conductive Electrodes

NiO and Cr2O3 are transition metal oxides with a partially filled d electron band that supports p-type conduction. Both are transparent to the visible light due to optical absorption beginning at wavelengths below 0.4 μm and the creation of holes by metal vacancy defects. The defect and strain effects on the electronic characteristics of these materials need to be established. For this purpose, NiO and Cr2O3 thin films were deposited on unheated glass substrates by reactive DC sputtering from metallic targets. Their structural, morphological, optical and electrical properties were analyzed comparatively in the as-grown conditions (25 °C) and after heating in air at 300 °C or 500 °C. The cubic NiO structure was identified with some tensile strain in the as-grown conditions and compressive strain after heating. Otherwise, the chromium oxide layers were amorphous as grown at 25 °C and crystallized into hexagonal Cr2O3 at 300 °C or above also with compressive strain after heating. Both materials achieved the highest visible transmittance (72%) and analogous electrical conductivity (~10−4 S/cm) by annealing at 500 °C. The as-grown NiO films showed a higher conductivity (2.5 × 10−2 S/cm) but lower transmittance (34%), which were related to more defects causing tensile strain in these samples.

Arthroscopic Internal Brace Augmentation With Arthroscopic Modified Broström Operation for Chronic Ankle Instability

Lateral ankle sprains are very common injuries that sometimes lead to chronic lateral ankle instability. The modified Broström operation is the gold standard procedure for treatment of chronic lateral ankle instability. Currently, this operation is performed arthroscopically. Broström repair depends on the quality of the remnant ligament. In cases with an insufficient remnant ligament, Gould augmentation or reconstruction using the gracilis tendon is generally performed. Recently, tape augmentation (internal brace) also has been used to support an insufficient ligament. This article introduces arthroscopic tape augmentation with arthroscopic modified Broström operation. This technique consists of creation of a talar anchor hole and fibular anchor hole, reattachment of the remnant ligament to the fibula with tape, and tape fixation to the talus. This technique uses only one knotless anchor screwed to the fibula for both the modified Broström operation and fixation of the tape. This technique is relatively simple and produces similar results as an open procedure.

Designed Analogue Black Hole Solitons in Josephson Transmission Lines

In the nonlinear LC circuit dual to the Toda (voltage) soliton, the current (shock-wave-type) solitons spatially modulate the velocity of the electromagnetic waves in the circuit through the nonlinear inductance, resulting in the creation of analogue black holes. The analogue black hole solitons are spontaneously formed, but their configuration could not be controlled so far. In this paper, the on-demand scheme to design the configuration of analogue black holes is presented by using solitons and antisolitons in the nonlinear LC circuit. In addition, a novel photon source using analogue Hawking radiation is also proposed.

Pseudo n-type behaviour of nickel oxide thin film at room temperature towards ammonia sensing

Sensors are part of a safe laboratory, working space and closed environment. In view of this, a sensing material for ammonia (NH3) vapour, nickel oxide (NiO) has been investigated to improve its quality as a sensor. The transparent nanostructured NiO thin films were deposited on glass substrates by sol-gel spin coating method at different molar concentrations (0.4 M, 0.6 M and 0.8 M). The NH3 sensing studies reveal that 0.6 M film shows admirable response of 403 (75 ppm), and also it has good response and recovery times (110 s and 33 s) for 25 ppm at room temperature. These features of the film are attributed to low surface roughness, small grain size and higher surface to volume ratio compared to other films. In presence of air ambience, the electrons at film surface are chemisorbed by oxygen molecules and thereby cause an increase of the depletion layer. Once the film is exposed to the analyte gas NH3, the depletion layer decreases because of electrons returning back to the conduction band (CB). These electrons are then de-excited to the valence band (VB) and recombine with holes (annihilation of holes). At the same time, the trapping of electrons by Ni(OH)2 and creation of holes by oxidation of Ni2+ into Ni3+ increases the hole concentration at VB, followed by a reduction of recombination rate of electrons and holes. All these processes decrease the potential barrier between the grains and thereby cause the Fermi level (EF) to shift towards VB. These processes remarkably enhance the sensing behaviour of the film. Importantly, the prepared NiO thin film behaves as a n-type sensor at room temperature for NH3; and therefore, termed as pseudo-n-type.

Theoretical investigations about the effect of electron-withdrawing groups on proprieties of A-π-D-π-A type small molecules donor for organic solar cells.

Taking the reporting donor SM0 as reference, three new A-π-D-π-A type small molecules donors (SM1, SM2, and SM3) were designed via replacing acceptor moieties. The molecular proprieties affecting the cell performance, such as, frontier molecular orbital, open circuit voltage (Voc), absorption spectrum, vertical and adiabatic ionization potential, vertical and adiabatic electronic affinity, and energy driving force ΔEL-L were investigated through the density functional theory (DFT) and the time dependent density functional theory (TD-DFT). All new designed molecules exhibit reduced energy gap, show a red shift absorption band, small energy binding Eb, moderate Voc, and improve the creation of hole and electron as compared to SM0, which demonstrate that these new designed molecules could be used as a promising donors materials for organic solar cell. Additionally, the three new designed molecules present a larger amount charge transfer qCT, a longer length charge transfer DCT than SM0 and have a smaller reorganization energy of hole λ(h) which improve the charge carrier mobilities.

The BEAMISH hot water drill system and its use on the Rutford Ice Stream, Antarctica

AbstractDuring the 2018/19 Antarctic field season, the British Antarctic Survey (BAS) Basal conditions on Rutford Ice Stream: BEd Access, Monitoring and Ice Sheet History’ (BEAMISH) project drilled three holes through the Rutford Ice Stream, West Antarctica. At up to 2154 m, these are the deepest hot water drilled subglacial access holes yet created, enabling the recovery of sediment from the subglacial environment, and instrumenting the ice stream and its bed. The BEAMISH hot-water drill system was built on extensive experience with the BAS ice shelf hot-water drill and utilises many identical components. With up to 1 MW of heating power available, the hot water drill produces 140 L min−1of water at 85°C to create a 300 mm diameter access hole to the base of the ice stream. New systems and processes were developed for BEAMISH to aid critical aspects of deep access drilling, most notably the creation of cavities interlinking boreholes at 230 m below the surface and enabling water recirculation throughout the deep drilling operations. The modular design of the BEAMISH drill offers many benefits in its adaptability, redundancy, and minimal logistical footprint. These design features can easily accommodate the modifications needed for future deep, clean access hole creation in the exploration of subglacial environments.

Optimization of Beta Radioluminescent Batteries with Different Radioisotopes: A Theoretical Study

In this paper, a beta radioluminescent battery with different radioisotopes is studied, and different parameters of the proposed structure are optimized. These parameters include the luminescent layer thickness, the doping concentration in the semiconductor P-N junction, etc. Some of the parameters have an inverse effect on the battery outputs. So, a trade-off is sought between them to increase efficiency. Each part of the proposed structure is divided into much smaller parts in the simulations to ensure proper tracking of photons and the creation of electron holes in the semiconductor layer. Also, the passage of particles through each layer is carefully reviewed and calculated in terms of particle crossing percentage, their reflection percentage, rate of self-absorption, etc. Finally, the power, open-circuit voltage, and short-circuit current density of the proposed battery versus the main parameter changes are presented.

Borehole breakout modeling in arkose and granite rocks

The existence of a deep borehole in the Earth’s crust disturbs the local stresses and creates a stress concentration that may result in breakout and damage to the borehole. Maintaining wellbore integrity mitigates environmental impacts such as groundwater contamination, gas leakage to the atmosphere, and fluid spills and seepage at the surface. In this paper, the stability of deep boreholes (5 km) is examined by laboratory experiments and numerical models in the context of nuclear waste disposal in Israel. Two rock types in southern Israel are considered: the crystalline basement (granite) and the Zenifim Formation (arkose). A series of room-temperature triaxial rock deformation experiments were conducted at different confining pressures. This mechanical characterization was then used to parameterize the elastic properties and damage behavior of the rocks. This facilitated modeling the stability of the deep boreholes by two different formulations of damage rheology: a dynamic-oriented formulation used to model deformation immediately after the creation of the open hole and a quasi-static formulation used to model longer stress corrosion regime. The calibrated modeling results indicate greater stability with Zenifim arkose than the crystalline granite for deep borehole conditions despite the granite having a greater triaxial compressive strength. Dissipation associated with dilation and porous compaction in the arkose during deformation plays a significant stabilizing role in the borehole compared to crystalline rocks. These results suggest that common strength-based borehole stability assessment may lead to inaccurate predictions. Three-dimensional modeling of bottom-hole stress conditions and the effects of transient borehole geometry show conventional two-dimensional analysis may not be conservative when predicting borehole damage.

Hole-Type Spacers for More Stable Shale Gas-Produced Water Treatment by Forward Osmosis.

An appropriate spacer design helps in minimizing membrane fouling which remains the major obstacle in forward osmosis (FO) systems. In the present study, the performance of a hole-type spacer (having holes at the filament intersections) was evaluated in a FO system and compared to a standard spacer design (without holes). The hole-type spacer exhibited slightly higher water flux and reverse solute flux (RSF) when Milli-Q water was used as feed solution and varied sodium chloride concentrations as draw solution. During shale gas produced water treatment, a severe flux decline was observed for both spacer designs due to the formation of barium sulfate scaling. SEM imaging revealed that the high shear force induced by the creation of holes led to the formation of scales on the entire membrane surface, causing a slightly higher flux decline than the standard spacer. Simultaneously, the presence of holes aided to mitigate the accumulation of foulants on spacer surface, resulting in no increase in pressure drop. Furthermore, a full cleaning efficiency was achieved by hole-type spacer attributed to the micro-jets effect induced by the holes, which aided to destroy the foulants and then sweep them away from the membrane surface.

Hole-rich CoP nanosheets with an optimized d-band center for enhancing pH-universal hydrogen evolution electrocatalysis

The creation of holes on the surface of CoP can optimize the d-band center of CoP for enhancing the HER activity. And this method can direct us to design more transition metal compound-based hole-rich catalysts.

Creation of carbon defects and in-plane holes with the assistance of NH4Br to enhance the photocatalytic activity of g-C3N4

A new holey defect-rich g-C3N4 photocatalyst from an NH4Br-assisted programmed heating method exhibits an enhanced photocatalytic performance.

Electrical properties of Mg-doped and Mg, Si co-doped alumina

Impedance measurements on Mg-doped alumina ceramics, over the temperature range 400−910 °C, showed a combination of oxide ion conductivity and p-type electronic conductivity, depending on temperature and oxygen partial pressure. The oxide ion conductivity is attributed to oxygen vacancies, introduced as charge compensation for the Mg dopant. The p-type conductivity is attributed to hole creation on under-bonded oxide ions and is the dominant conductivity for measurements in air at high temperatures. In samples co-doped with Mg and Si, impedance measurements showed a reduction in oxide ion conductivity and therefore, number of oxide ion vacancies because the self-compensation mechanism of co-doping lead to direct replacement of Al3+by Mg2+ and Si4+; the level of p-type conductivity was also reduced.

Sacrificial Volume Materials for Small Hole Generation in Low-Temperature Cofired Ceramics

The creation of hole, cavity or channel structures in low-temperature cofired ceramics (LTCCs), using different sacrificial volume materials (SVMs) was tested. The main functionality of the SVMs should be: easy application into the holes; protection of holes during lamination; uninhibited lamination between layers; and, during firing should burn out before the pores of the LTCCs close, to leave the empty holes clear of any residue. Five different materials were tested—hydroxyethyl cellulose (HEC) 2 wt%, HEC 5 wt%, agar-agar, gelatin, and commercial carbon paste—and compared to a reference sample where no SVMs were used. In all cases, lamination parameters were minimised in order to preserve the tested hole structures. Matrixes with holes ranging from 158 to 268 µm, with pitches of 573 µm in a green state, were tested. The agar-agar caused ceramic deformation as a result of thermal burst during firing and the lamination between the layers was compromised. The carbon paste was difficult to handle, requiring extra equipment for hole filling and incomplete filling of the larger holes. Traces of carbon paste were left as a landing pad on top of the holes, inhibiting lamination at these areas. The gelatin and the 2 wt% and 5 wt% hydroxyethylcellulose (HEC 2 wt% and HEC 5 wt%) filled all holes completely, and also worked as adhesive-assisted lamination (AAL) materials with excellent lamination between layers. Excellent lamination was also observed in the no-SVM case. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) analyses established that, for all SVMs tested, the remaining residue is negligible after firing. As a result, the HEC 2 wt% material was considered ideal for use as an SVM.