Gold Tracks Research Articles

EVALUATING THE EFFECTIVENESS OF DEMONSTRATION-CUM-DISCUSSION TEACHING STRATEGY ON STUDENTS’ ACADEMIC ACHIEVEMENT IN SOME ECOLOGICAL CONCEPTS

This study investigated the effectiveness of Demonstration-cum-Discussion teaching strategy on students’ academic achievement in ecological concepts at Navrongo Senior High School, using quasi-experimental design (pretest, posttest non-equivalent approach). The sample comprised of 75 Form Two General Science Gold Track (control group of 29 males and 10 females) and Green Track (experimental group of 21 males and 15 females) students. The experimental group and control groups were taught using Demonstration-cum-Discussion teaching strategy and Conventional Teaching Method respectively. The test-retest reliability coefficient of the instrument was found to be 0.78. The pretest scores revealed that the students were homogeneous in terms of academic achievement (Mean = (22.19, 21.46) t-value = 0.87, p-value = 0.39, p > 0.05). The posttest results of the experimental group were significantly higher than the control group (Mean = (48.19, 38.71) t-value = 12.43, p-value = 0.000, p < 0.05). There was no significant difference in the achievement of male and female students in the experimental group for both pretest (Mean = (23.24, 21.33) t-value = 1.43, p-value = 0.20, p > 0.05) and posttest (Mean = (48.52, 47.73) t-value = 0.53, p-value = 0.59, p > 0.05). This study recommended that Biology teachers at Navrongo Senior High School should be encouraged to teach the concept of Ecology using demonstration-cum-discussion in order to enhance the conceptual understanding and academic achievement of students. 
 
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EFFECT OF CONCEPT MAPPING INSTRUCTIONAL STRATEGY ACCOMPANIED BY DISCUSSION WEB ON STUDENTS’ ACADEMIC ACHIEVEMENT IN THE CONCEPT OF GENETICS

Purpose: This study explored the effect of Concept Mapping Instructional Strategy Accompanied by Discussion Web on students’ academic achievement in the concept of Genetics at Navrongo Senior High School, generally, and on gender basis.
 Methodology: The study adopted quasi-experimental design (pretest, posttest non-equivalent design). The sample comprised of 80 Navrongo Senior High School Form Three Gold Track and Green Track science students. Students from the Green Track class and Gold Track class were assigned experimental group and control group respectively. The experimental group class was made up of 23 males and 20 females. The control group class was also made up of 24 males and 13 females. Pretest was administered to all the participants. The experimental group was taught using Concept Mapping Instructional Strategy Accompanied by Discussion Web. The control group was taught using Conventional Teaching Method. A posttest was administered to both groups to determine the effectiveness of the treatment. The reliability of the test items was determined using test-retest reliability coefficient. The test-retest reliability coefficients of the instruments were found to be 0.70 and 0.73 for the pretest and posttest respectively. The data obtained were analysed using t-test.
 Results: The pretest test scores revealed that the students were homogeneous in terms of academic achievement (t-value = 1.05, p-value=0.30, p>0.05). Posttest results of students in the experimental group were significantly higher than the control group (t-value = 8.07, p-value = 0.000, p < 0.05). The result of the posttest showed that the use of concept mapping instructional strategy accompanied by discussion web in teaching genetics was more effective than conventional teaching method. There was no statistically significant difference in the academic achievement of male and female students in the experimental group (t-value = 1.68, p-value = 0.11, p > 0.05).
 Unique contribution to theory, practice and policy: This study recommended that Biology teachers in Navrongo Senior High School should be encouraged to teach Genetics using Concept Mapping Instructional Strategy Accompanied by Discussion Web in order to improve the academic achievement of students. Science teachers should be given the opportunity to attend workshops, seminars, conferences to enable them update their knowledge on current instructional strategies that are capable of improving the academic achievement of students. The Government, Ghana Education Service and Ministry of Education should establish professional development fund for teachers to enable them upgrade professionally and also improve on their teaching styles since most teacher are not abreast with the current or modern methods of teaching.

Effect of Multimodal Instructional Approach on Students’ Academic Performance in The Concept of Biological Classification

Purpose: This study investigated the effect of Multimodal Instructional Approach on students’ academic performance in the concept of Biological Classification at Navrongo Senior High School, generally, and on gender basis.
 Methodology: The study adopted quasi-experimental research design. The sample comprised of 100 Navrongo Senior High School Form Two Gold Track and Green Track science students. Students from the Gold Track and Green Track were designated experimental group and control group respectively. Each group was made up of 25 males and 25 females. Pretest was administered to all the participants. The experimental group was taught using Multimodal Instructional Approach. The control group was taught using Discussion as the teaching method. A posttest was administered to both groups to determine the effectiveness of the treatment. The reliability of the test items was determined using test-retest reliability coefficient. The test-retest reliability coefficients of the instruments were found to be 0.73 and 0.78 for the pretest and posttest respectively. The data obtained were analysed using independent sample t-test.
 Results: The pretest test scores revealed that the students were homogeneous in terms of performance. Posttest results of students in the experimental group were significantly higher than the control group. There was no significant difference in the performance of males and females. The results of the posttest revealed that the use of MIA in teaching biological classification was more effective than discussion method.
 Unique contribution to theory, practice and policy: This study recommended that Biology teachers in NSHS should be encouraged to teach Biological Classification using MIA in order to improve the academic performance of both male and female students. School authority should invite educational technologists, instructional materials technicians and computer experts to help science teachers of NSHS on how to incorporate ICT in teaching science subjects.

Near‐Field Communication Powered Hydrogel‐Based Smart Contact Lens

AbstractNowadays, smart contact lenses (SCLs) display interesting features for healthcare monitoring; however, their comfort and practical usability strongly depend on the outermost material in contact with the eye. In this publication, the embedding of a custom‐made and thermoformed Near‐Field Communication based circuit in a conventional soft CL is presented. The circuit is composed of gold tracks on polyimide between thermoplastic polyurethane layers (insert), while the lens is based on industry standard double‐molding process of poly(2‐hydroxyethyl methacrylate) with proven compatibility with corneal tissue. The lens shows stable geometrical parameters (bevel landing area) thus enabling a practical implementation. Finite element method models are used to optimize the thermoforming process in order to provide a stable and desired curvature of the insert before the embedding process. While the insert is designed to allow oxygen transmission at the center of the lens, a custom‐made ultra‐compact radio‐frequency antenna provides communication and wireless power transfer both in air and inside saline solutions. The successful combination of the intrinsic soft mechanical properties of the wirelessly powered electronic insert with conventional hydrogel materials and manufacturing processes delivers a practical solution for SCLs. This enables non‐invasive applications in fields such as vision correction and/or biomedical sensing.

Wireless retina implant with optical energy supply

Abstract We present the first results of work towards a foil-based epiretinal prosthesis that can stimulate retinal cells. The prosthesis receives trigger signals and energy in the form of high intensity infrared radiation. Array-like silicon photodiodes with attached thin film electrodes convert the received infrared light into electrical stimulation signals, which are intended to stimulate ganglion cells. The photodiodes are arranged like stones in a mosaic on an only 10 µm thin and thus flexible polymer foil. Like this, the prosthesis can adapt to the curved shape of the eye and will have close contact with the retina. The photodiode array is fabricated on silicon wafers. Etched trenches guarantee the electrical separation between the individual photodiodes and pixels. Spectral sensitivities of backside-illuminated photodiodes were measured for wafers thinned to different thicknesses. The thin polymer foil is realized by spin coating polyimide on the photodiode array followed by imidization. Via holes are etched into the polyimide film for contacting the pads of the photodiodes. First spin coating tests were performed using silicon wafers without photodiodes but with metal pads and with etched trenches to simulate the gap between individual photodiodes. Although the thickness of the spin-coated polyimide layer was very inhomogeneous, we succeeded in realizing vias for connecting contact pads by thin film gold tracks crossing deep trenches. The realized via holes had inclined sidewalls as desired. Electrical measurements showed sufficient electrical contact between two connected pads.

Design and fabrication of a microelectromechanical system resonator based on two orthogonal silicon beams with integrated mirror for monitoring in-plane magnetic field

We present a resonant magnetic field sensor based on microelectromechanical systems technology with optical detection. The sensor has single resonator composed of two orthogonal silicon beams (600 µm × 26 µm × 2 µm) with an integrated mirror (50 µm × 34 µm × 0.11 µm) and gold tracks (16 µm × 0.11 µm). The resonator is fabricated using silicon-on-insulator wafer in a simple bulk micromachining process. The sensor has easy performance that allows its oscillation in the first bending vibration mode through the Lorentz force for monitoring in-plane magnetic field. Analytical models are developed to predict first bending resonant frequency, quality factor, and displacements of the resonator. In addition, finite element method models are obtained to estimate the resonator performance. The results of the proposed analytical models agree well with those of the finite element method models. For alternating electrical current of 30 mA, the sensor has a theoretical linear response, a first bending resonant frequency of 43.8 kHz, a sensitivity of 46.1 µm T−1, and a power consumption close to 54 mW. The experimental resonant frequency of the sensor is 53 kHz. The proposed sensor could be used for monitoring in-plane magnetic field without a complex signal conditioning system.

Focused Ion Beam and Advanced Electron Microscopy for Minerals: Insights and Outlook from Bismuth Sulphosalts

This paper comprises a review of the rapidly expanding application of nanoscale mineral characterization methodology to the study of ore deposits. Utilising bismuth sulphosalt minerals from a reaction front in a skarn assemblage as an example, we illustrate how a complex problem in ore petrology, can be approached at scales down to that of single atoms. We demonstrate the interpretive opportunities that can be realised by doing this for other minerals within their petrogenetic contexts. From an area defined as Au-rich within a sulphosalt-sulphide assemblage, and using samples prepared on a Focused Ion Beam–Scanning Electron Microscopy (SEM) platform, we identify mineral species and trace the evolution of their intergrowths down to the atomic scale. Our approach progresses from a petrographic and trace element study of a larger polished block, to high-resolution Transmission Electron Microscopy (TEM) and High Angle Annular Dark Field (HAADF) Scanning-TEM (STEM) studies. Lattice-scale heterogeneity imaged in HAADF STEM mode is expressed by changes in composition of unit cell slabs followed by nanoparticle formation and their growth into “veins”. We report a progressive transition from sulphosalt species which host lattice-bound Au (neyite, lillianite homologues; Pb-Bi-sulphosalts), to those that cannot accept Au (aikinite). This transition acts as a crystal structural barrier for Au. Fine particles of native gold track this progression over the scale of several hundred microns, leading to Au enrichment at the reaction front defined by an increase in the Cu gradient (several wt %), and abrupt changes in sulphosalt speciation from Pb-Bi-sulphosalts to aikinite. Atom-scale resolution imaging in HAADF STEM mode allows for the direct visualisation of the three component slabs in the neyite crystal structure, one of the largest and complex sulphosalts of boxwork-type. We show for the first time the presence of aikinite nanoparticles a few nanometres in size, occurring on distinct (111)PbS slabs in the neyite. This directly explains the non-stoichiometry of this phase, particularly with respect to Cu. Such non-stoichiometry is discussed elsewhere as defining distinct mineral species. The interplay between modular crystal structures and trace element behaviour, as discussed here for Au and Cu, has applications for other mineral systems. These include the incorporation and release of critical metals in sulphides, heavy elements (U, Pb, W) in iron oxides, the distribution of rare earth elements (REE), Y, and chalcophile elements (Mo, As) in calcic garnets, and the identification of nanometre-sized particles containing daughter products of radioactive decay in ores, concentrates, and tailings.

QBF Gallery 2014: The QBF Competition at the FLoC 2014 Olympic Games

The QBFGallery 2014 was a competitive evaluation for QBF solvers organized in the context of the FLoC 2014 Olympic Games of the Vienna Summer of Logic. Quantified Boolean formulas (QBF) extend formulas of propositional logic by existential and universal quantifiers over the propositional variables and, thus, lift the satisfiablity problem from NP to PSPACE. In consequence, there are many application problems from fields like verification, synthesis, and planning that can be encoded efficiently in QBF. This motivates the quest for efficient QBF solvers. The QBFGallery 2014 invited the developers of QBF solvers to submit their tools to a competitive evaluation in a uniform environment. Gold, silver, and bronze track medals were awarded to the solvers that solved the most formulas in each of three different tracks covering various kinds of benchmarks. Additionally, the three participants that were most successful overall were decorated with Kurt G odel medals, the official prizes of the Olympic Games. In this paper, we give an overview of the setup of the competition, we briefly review the participating solvers, and finally report on the results of the QBFGallery 2014.

Electrical monitoring of crack propagation during quasi-static loading and ballistic impact of alumina plates

Abstract An electrical methodology has been developed to monitor crack advance during ballistic impact. Velocities of radial cracks can be measured and information about development of the crack pattern can be obtained. This is done via a grid of thin gold tracks, printed onto the front or back surfaces of the sample. These elements were incorporated into an electrical circuit and high speed data acquisition was carried out during impact. The fracture behaviour of two grades of alumina has been examined. Hard spherical projectiles were used, with a range of impact velocities. An increase in radial crack velocity was detected with increasing impact velocity, within this range. Differences in crack velocities were also noted between the two types of alumina. Crack speed values are in good agreement with data reported previously for similar systems, obtained using high speed photography. The methodology proposed here looks to be reliable, convenient and economically attractive.

Development and evaluation of thin-film flexible microelectrode arrays for retinal stimulation and recording

We have described the development of a flexible microelectrode array with potential applications in the large scale recording of neural signals and in focal electrical stimulation for use as a prosthetic implant in degenerative retinal diseases. The array under test consisted of 61 platinum electrodes of 5 µm diameter with 60 µm spacing connected by 8 µm wide gold tracks encased in a flexible polyimide substrate of 15 µm thickness from which recordings were taken from 16 electrodes. The device was tested on an exposed frog eyecup preparation which is characterized by small retinal ganglion cells of similar dimensions to those present in the human retina. The responses of these cells evoked by photic stimulation consisted of trains of action potentials of high signal-to noise ratio at each of the recording sites. Delivery of cathodal constant voltage pulses and constant current pulses to specific electrodes in the array led to the generation of action potentials in adjacent electrodes, implying that retinal ganglion cells in the proximity had been stimulated. Since prolonged stimulation with supra-threshold voltages impaired neither electrode structure nor retinal function, these results provide a sound basis for scaling up the number of array electrodes to deliver focal electrical pulses to the retina, as would be required by a viable epiretinal prosthesis.

Fabrication of soft gold microelectrode arrays as probes for scanning electrochemical microscopy

Soft linear gold microelectrode arrays for high throughput scanning electrochemical microscopy (SECM) imaging were fabricated using the Aerosol Jet® printing technology. Nanoparticulate gold ink was printed on polyimide Kapton HN® thin films. After sintering, a 200 nm thick Parylene C coating was deposited to cover and seal the gold tracks. A cross-section of the array of microelectrodes was exposed by laser cutting using an ArF excimer laser beam directed onto a metallic mask. Cyclic voltammograms, approach curves and SECM images in feedback mode demonstrate the capability of the arrays as SECM probes. Reactivity imaging of a platinum band structure on glass was performed with Parylene C coating facing the substrate providing an almost constant working distance. The softness of the array leads to a bending and allows scanning in contact mode like brushing the sample surface. For hard surfaces such as array electrode structures and similar materials, this occurs without detectable damage to the sample.

On the Principles of Printing Sub-micrometer 3D Structures from Dielectric-Liquid-Based Colloids

Dielectrophoresis-assisted (DEP) on-demand printing of dielectric-liquid-based colloidal gold under room conditions is demonstrated and employed to print 2D and 3D structures with sub-micrometer feature sizes. The focus of the work is primarily on explaining the physics of the printing process, based on the formation of a controlled sequence of sub-micrometer drops. The physics of 3D structure formation on the substrate is explained through the visualization and analysis of various time-scales relevant to the printing process and the pinning of the contact line of the printed colloids. A parametric variation of the related variables, namely the applied voltage and the pulse length, is used to investigate the morphology and topography of a host of basic, printable 2D and 3D features. It is established that it is possible to obtain uniform particle deposits in 2D by filling up an initial coffee-ring-type non-uniform deposit with a series of subsequently formed drops, all obtained during a single electric pulse. Finally, on-demand production of multilayered, sub-micrometer gold tracks is demonstrated, where the annealed tracks exhibit exceptionally low electrical resistivity for their sizes, only two times higher than that of bulk gold.

Polymer-based micro flow sensor for dynamical flow measurements in hydraulic systems

In this paper we present a micro flow sensor from a polymer for dynamical flow measurements in hydraulic systems. The flow sensor is based on the thermal anemometric principle and consists of two micro-structured housing shells from polysulfone (PSU) which form a small fluidic channel with a cross-section of 580 µm × 400 µm. In between there is a thin polyimide membrane supporting three gold track structures forming an electrical heater and two resistive thermometers which allows the detection of the flow direction, too. The complete sensor is inserted into the hydraulic system, but only a small bypass flow is directed through the fluidic channel by means of a special splitting system. Due to its small heat capacity, the sensor is suitable to detect flow pulsations up to about 1200 Hz which allows the sensor to be used for the condition monitoring or preventive maintenance of hydraulic systems.

Realisation and characterisation of mass-based diamond micro-transducers working in dynamic mode

We report on novel MEMS micro-transducers made of diamond and targeted for bio-sensing applications. To overcome the non-straightforward micromachining of diamond, we developed a bottom up process for the fabrication of synthetic diamond micro-structures involving the patterned growth of diamond using the CVD (chemical vapour deposition) technique, inside micro-machined silicon moulds. Here typical resonant MEMS structures including cantilevers fabricated using this method were characterized by measuring their first mode resonance (frequency and Q-factor) by Doppler laser interferometry. The experimental data matched the simulation data. Data from bare diamond cantilevers and from diamond cantilevers with actuation gold track on the surface were compared and showed a significant decrease in the resonant frequency in the presence of gold tracks. Nevertheless, comparisons with equivalent silicon structures demonstrated the superior performances of diamond cantilevers: the resonance frequencies were twice higher and the Q-factors 2.5 times higher for the diamond transducers. Diamond cantilevers sensitivity were measured using PMMA deposition and values as high as 227.4 Hz ng −1 were found. It was shown that diamond mass sensitivity values are typically two times higher than identical silicon devices. Finally, the limit of detection (LOD) of diamond cantilevers was found experimentally to be as low as 0.86 pg using our set up. This is suitable for many bio-sensing applications.

Dynamical flow measurements in hydraulic systems using a polymer-based micro flow sensor

We present a dynamical flow sensor for the condition monitoring of hydraulic systems using a micro flow sensor from polymer. The micro flow sensor is based on the thermal anemometric principle. A thin Polyimide membrane is used as a support for 3 gold track structures forming a heater and two resistive thermometers. When inserted into the hydraulic pipe only a small bypass flow is directed through the fluidic channel of the sensor by means of a special splitting system. Due to its small heat capacity the flow sensor is suitable to detect flow pulsations up to about 1000 Hz.

Electric-Jet Assisted Layer-by-Layer Deposition of Gold Nanoparticles to Prepare Conducting Tracks

A suspension of 15nm diameter gold nanoparti-cles has been deposited along a line on a silicon substrate with the assistance of a jet generated in an electric field. In order to control the evaporation of the solvent used to suspend the gold nanoparticles, a heating device was used to change the substrate temperature. Layer-by- layer deposition enabled the direct writing of gold tracks having an electrical resistivity of 1.8 × 10-7 Ωm, only about an order of magnitude above the electrical resistivity of bulk gold.

Imaging of Effector Memory T Cells during a Delayed-Type Hypersensitivity Reaction and Suppression by Kv1.3 Channel Block

Effector memory T (Tem) cells are essential mediators of autoimmune disease and delayed-type hypersensitivity (DTH), a convenient model for two-photon imaging of Tem cell participation in an inflammatory response. Shortly (3 hr) after entry into antigen-primed ear tissue, Tem cells stably attached to antigen-bearing antigen-presenting cells (APCs). After 24 hr, enlarged Tem cells were highly motile along collagen fibers and continued to migrate rapidly for 18 hr. Tem cells rely on voltage-gated Kv1.3 potassium channels to regulate calcium signaling. ShK-186, a specific Kv1.3 blocker, inhibited DTH and suppressed Tem cell enlargement and motility in inflamed tissue but had no effect on homing to or motility in lymph nodes of naive and central memory T (Tcm) cells. ShK-186 effectively treated disease in a rat model of multiple sclerosis. These results demonstrate a requirement for Kv1.3 channels in Tem cells during an inflammatory immune response in peripheral tissues. Targeting Kv1.3 allows for effector memory responses to be suppressed while central memory responses remain intact.

Stretchable Gold Tracks on Flat Polydimethylsiloxane (PDMS) Rubber Substrate

A process to fabricate stretchable gold tracks on silicone rubber substrates is studied by XPS, static water contact angle measurement, AFM, and SEM. The process involves several steps: removing uncured oligomers by hexane Soxhlet extraction; pre-stretching the substrate; activating the strained silicone surface by an oxygen plasma treatment; coating the strained substrate with 5 nm titanium and 80 nm gold layers; and finally releasing the sample. The plasma treatment creates a thin brittle silica-like layer that temporarily increases the substrate's surface energy. Indeed, the plasma treatment is followed by a hydrophobic recovery. As a consequence, the delay between plasma treatment and metal deposition has to be reduced as much as possible. The silica-like layer can be nicely observed after release. The entire process allows us to obtain stretchable metallized samples that remain conductive even after an excessive deformation leading to electrical failure.

Metallization Process for Polydimethylsiloxane (PDMS) Rubber

AbstractA process to fabricate stretchable and adherent gold tracks on flat silicone rubber substrates is studied by X-ray photoelectron spectroscopy (XPS), static water contact angle measurement, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The process involves several steps: curing flat silicone substrate; removing uncured oligomers by hexane Soxhlet extraction; pre-stretching the substrate; activating the strained silicone surface by an oxygen plasma treatment; coating the strained substrate with 5nm titanium and 80nm gold layers by e-beam evaporation; and finally releasing the sample. The plasma treatment creates a thin brittle silica-like layer that temporarily increases the substrate's surface energy. Indeed the plasma treatment is followed by a hydrophobic recovery. As a consequence, the delay between plasma treatment and metal deposition has to be reduced as much as possible. The silica-like layer can be nicely observed after release. Its thickness is estimated to be around 20nm to 50nm. The entire process allows us to obtain stretchable metallized samples that remain conductive even after an excessive deformation leading to electrical failure.

Printing gold nanoparticles with an electrohydrodynamic direct-write device

A dispersion containing 15nm gold particles in ethanol was subjected to electrohydrodynamic atomization, producing droplets with an average size of ≈26μm as measured by laser diffraction. An electrohydrodynamic direct-write device was used to deposit the dispersion onto silicon wafers with the intention of printing gold tracks. Immediately after deposition ethanol evaporated, leaving the gold particles organised in a ≈75μm wide central region surrounded by two regions, each ≈50μm wide, at the edge of which two further gold tracks, each ≈7μm existed.