Effect of anisotropy on elastic moduli measured by nanoindentation in human tibial cortical bone

Many biological materials are known to be anisotropic. In particular, microstructural components of biological materials may grow in a preferred direction, giving rise to anisotropy in the microstructure. Nanoindentation has been shown to be an effective technique for determining the mechanical properties of microstructures as small as a few microns. However, the effects of anisotropy on the properties measured by nanoindentation have not been fully addressed. This study presents a method to account for the effects of anisotropy on elastic properties measured by nanoindentation. This method is used to correlate elastic properties determined from earlier nanoindentation experiments and from earlier ultrasonic velocity measurements in human tibial cortical bone. Also presented is a procedure to determine anisotropic elastic moduli from indentation measurements in multiple directions. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res.

Cost-effective and eco-friendly synthesis of novel and stable N-doped ZnO/g-C3N4 core-shell nanoplates with excellent visible-light responsive photocatalysis

N-doped ZnO/g-C3N4 hybrid core–shell nanoplates have been successfully prepared via a facile, cost-effective and eco-friendly ultrasonic dispersion method for the first time. HRTEM studies confirm the formation of the N-doped ZnO/g-C3N4 hybrid core–shell nanoplates with an average diameter of 50 nm and the g-C3N4 shell thickness can be tuned by varying the content of loaded g-C3N4. The direct contact of the N-doped ZnO surface and g-C3N4 shell without any adhesive interlayer introduced a new carbon energy level in the N-doped ZnO band gap and thereby effectively lowered the band gap energy. Consequently, the as-prepared hybrid core–shell nanoplates showed a greatly enhanced visible-light photocatalysis for the degradation of Rhodamine B compare to that of pure N-doped ZnO surface and g-C3N4. Based on the experimental results, a proposed mechanism for the N-doped ZnO/g-C3N4 photocatalyst was discussed. Interestingly, the hybrid core–shell nanoplates possess high photostability. The improved photocatalytic performance is due to a synergistic effect at the interface of the N-doped ZnO and g-C3N4 including large surface-exposure area, energy band structure and enhanced charge-separation properties. Significantly, the enhanced performance also demonstrates the importance of evaluating new core–shell composite photocatalysts with g-C3N4 as shell material.

Intellect Sensing of Neural Network that Trained to Classify Complex Signals

An experimental comparison of information features used by neural network is performed. The sensing method was used. Suboptimal classifier agreeable to the gaussian model of the training data was used as a probe. Neural nets with architectures of perceptron and feedforward net with one hidden layer were used. The experiments were carried out with spatial ultrasonic data, which are used for car’s passenger safety system neural controller learning. In this paper we show that a neural network doesn’t fully make use of gaussian components, which are first two moment coefficients of probability distribution. On the contrary, the network can find more complicated regularities inside data vectors and thus shows better results than suboptimal classifier. The parallel connection of suboptimal classifier improves work of modular neural network whereas its connection to the network input improves the specialization effect during training.

An algorithm for FHR estimation from foetal phonocardiographic signals

The long-term foetal surveillance is often to be recommended. Hence, the fully non-invasive acoustic recording, through maternal abdomen, represents a valuable alternative to the ultrasonic cardiotocography. Unfortunately, the recorded heart sound signal is heavily loaded by noise, thus the determination of the foetal heart rate raises serious signal processing issues. In this paper, we present a new algorithm for foetal heart rate estimation from foetal phonocardiographic recordings. A filtering is employed as a first step of the algorithm to reduce the background noise. A block for first heart sounds enhancing is then used to further reduce other components of foetal heart sound signals. A complex logic block, guided by a number of rules concerning foetal heart beat regularity, is proposed as a successive block, for the detection of most probable first heart sounds from several candidates. A final block is used for exact first heart sound timing and in turn foetal heart rate estimation. Filtering and enhancing blocks are actually implemented by means of different techniques, so that different processing paths are proposed. Furthermore, a reliability index is introduced to quantify the consistency of the estimated foetal heart rate and, based on statistic parameters; [,] a software quality index is designed to indicate the most reliable analysis procedure (that is, combining the best processing path and the most accurate time mark of the first heart sound, provides the lowest estimation errors). The algorithm performances have been tested on phonocardiographic signals recorded in a local gynaecology private practice from a sample group of about 50 pregnant women. Phonocardiographic signals have been recorded simultaneously to ultrasonic cardiotocographic signals in order to compare the two foetal heart rate series (the one estimated by our algorithm and the other provided by cardiotocographic device). Our results show that the proposed algorithm, in particular some analysis procedures, provides reliable foetal heart rate signals, very close to the reference cardiotocographic recordings. © 2010 Elsevier Ltd. All rights reserved.

Fabry-Perot micro-structured polymer optical fibre sensors for opto-acoustic endoscopy

Opto-Acoustic Endoscopy (OAE) requires sensors with a high sensitivity and small physical dimensions in order to facilitate integration into an endoscope of less than 1mm in diameter. We present fibre Bragg grating (FBG) and Fabry- Perot intrinsic fibre sensors for ultrasound detection. We present a structure profile characterisation setup to analyse tune the fibre sensors in preparation for ultrasonic detection. We evaluate the suitability of the different structures and grating parameters for ultrasonic sensing. By analysing the prepared gratings, we enable the optimisation of the profile and a simplification of the detection regime for an optimal interferometric OAE configuration.

Polymer optical fibre sensors for endoscopic optoacoustic imaging

Opto-acoustic imaging (OAI) shows particular promise for in-vivo biomedical diagnostics. Its applications include cardiovascular, gastrointestinal and urogenital systems imaging. Opto-acoustic endoscopy (OAE) allows the imaging of body parts through cavities permitting entry. The critical parameter is the physical size of the device, allowing compatibility with current technology, while governing flexibility of the distal end of the endoscope based on the needs of the sensor. Polymer optical fibre (POF) presents a novel approach for endoscopic applications and has been positively discussed and compared in existing publications. A great advantage can be obtained for endoscopy due to a small size and array potential to provide discrete imaging speed improvements. Optical fibre exhibits numerous advantages over conventional piezo-electric transducers, such as immunity from electromagnetic interference and a higher resolution at small sizes. Furthermore, micro structured polymer optical fibres offer over 12 times the sensitivity of silica fibre. We present a polymer fibre Bragg grating ultrasound detector with a core diameter of 125 microns. We discuss the ultrasonic signals received and draw conclusions on the opportunities and challenges of applying this technology in biomedical applications.

A compact polymer optical fibre ultrasound detector

Polymer optical fibre (POF) is a relatively new and novel technology that presents an innovative approach for ultrasonic endoscopic applications. Currently, piezo electric transducers are the typical detectors of choice, albeit possessing a limited bandwidth due to their resonant nature and a sensitivity that decreases proportionally to their size. Optical fibres provide immunity from electromagnetic interference and POF in particular boasts more suitable physical characteristics than silica optical fibre. The most important of these are lower acoustic impedance, a reduced Young's Modulus and a higher acoustic sensitivity than single-mode silica fibre at both 1 MHz and 10 MHz. POF therefore offers an interesting alternative to existing technology. Intrinsic fibre structures such as Bragg gratings and Fabry-Perot cavities may be inscribed into the fibre core using UV lasers. These gratings are a modulation of the refractive index of the fibre core and provide the advantages of high reflectivity, customisable bandwidth and point detection. We present a compact in fibre ultrasonic point detector based upon a POF Bragg grating (POFBG) sensor. We demonstrate that the detector is capable of leaving a laboratory environment by using connectorised fibre sensors and make a case for endoscopic ultrasonic detection through use of a mounting structure that better mimics the environment of an endoscopic probe. We measure the effects of water immersion upon POFBGs and analyse the ultrasonic response for 1, 5 and 10 MHz.

g-C3N4/NaTaO3 organic–inorganic hybrid nanocomposite:high-performance and recyclable visible light driven photocatalyst

Novel g-C3N4/NaTaO3 hybrid nanocomposites have been prepared by a facile ultrasonic dispersion method. Our results clearly show the formation of interface between NaTaO3 and g-C3N4 and further loading of g-C3N4 did not affect the crystal structure and morphology of NaTaO3. The g-C3N4/NaTaO3 nanocomposites exhibited enhanced photocatalytic performance for the degradation of Rhodamine B under UV–visible and visible light irradiation compared to pure NaTaO3 and Degussa P25. Interestingly, the visible light photocatalytic activity is generated due to the loading of g-C3N4. A mechanism is proposed to discuss the enhanced photocatalytic activity based on trapping experiments of photoinduced radicals and holes. Under visible light irradiation, electron excited from the valance band (VB) to conduction band (CB) of g-C3N4 could directly inject into the CB of NaTaO3, making g-C3N4/NaTaO3 visible light driven photocatalyst. Since the as-prepared hybrid nanocomposites possess high reusability therefore it can be promising photocatalyst for environmental applications.

Mechanistic studies on the degradation of gasoline oxygenates by advanced oxidation technologies and the reaction of 4-methyl-1,2,4-triazoline-3,5-dione with tetracyclopropylethylene

Gasoline oxygenates (MTBE, methyl tert-butyl ether; DIPE, di-isopropyl ether; ETBE, ethyl tert-butyl ether; TAME, tert-amyl ether) are added to gasoline to boost octane and enhance combustion. The combination of large scale use, high water solubility and only minor biodegradability has now resulted in a significant gasoline oxygenate contamination occurring in surface, ground, and drinking water systems. Combination of hydroxyl radical formation and the pyrolytic environment generated by ultrasonic irradiation (665 kHz) leads to the rapid degradation of MTBE and other gasoline oxygenates in aqueous media. ^ The presence of oxygen promotes the degradation processes by rapid reaction with carbon centered radicals indicating radical processes involving O 2 are significant pathways. A number of the oxidation products were identified. The formation of products (alcohols, ketones, aldehydes, esters, peroxides, etc) could be rationalized by mechanisms which involve hydrogen abstraction by OH radical and/or pyrolysis to form carboncentered radicals which react with oxygen and follow standard oxidation chain processes. ^ The reactions of N-substituted R-triazolinediones (RTAD; R = CH 3 or phenyl) have attracted considerable interest because they exhibit a number of unusual mechanistic characteristics that are analogous to the reactions of singlet oxygen (1O2) and offer an easy way to provide C-N bond(s) formation. The reactions of triazolinedione with olefins have been widely studied and aziridinium imides are generally accepted to be the reactive intermediates. ^ We observed the rapid formation of an unusual intermediate upon mixing tetracyclopropylethylene with 4-methyl-1,2,4-triazoline-3,5-dione in CDCl 3. Detailed characterization by NMR (proton, 13C, 2-D NMRs) indicates the intermediate is 5,5,6,6-tetracyclopropyl-3-methyl-5,6-dihydro-oxazolo[3,2- b][1,2,4]-triazolium-2-olate. Such products are extremely rare and have not been studied. Upon warming the intermediate is converted to 2 + 2 diazetidine (major) and ene product (minor). ^ To further explore the kinetics and dynamics of the reaction activation energies were obtained using Arrhenius plots. Activation energies for the formation of the intermediate from reactants, and 2+2 adduct from the intermediate were determined as 7.48 kcal moll and 19.8 kcal mol−1 with their pre-exponential values of 2.24 × 105 dm 3 mol−1 sec−1 and 2.75 × 108 sec−1, respectively, meaning net slow reactions because of low pre-exponential values caused by steric hindrance. ^

Advanced oxidation of arsenic species in aqueous solutions

Ingestion of arsenic from contaminated water is a serious problem and affects the health of more than 100 million people worldwide. Traditional water purification technologies are generally not effective or cost prohibitive for the removal of arsenic to acceptable levels (≤10 ppb). Current multi-step arsenic removal processes involve oxidation, precipitation and/or adsorption. Advanced Oxidation Technologies (AOTs) may be attractive alternatives to existing treatments. The reactions of inorganic and organic arsenic species with reactive oxygen species were studied to develop a fundamental mechanistic understanding of these reactions, which is critical in identifying an effective and economical technology for treatment of arsenic contaminated water. ^ Detailed studies on the conversion of arsenite in aqueous media by ultrasonic irradiation and TiO2 photocatalytic oxidation (PCO) were conducted, focusing on the roles of hydroxyl radical and superoxide anion radical formed during the irradiation. ·OH plays the key role, while O2 -· has little or no role in the conversion of arsenite during ultrasonic irradiation. The reaction of O2-· does not contribute in the rapid conversion of As(III) when compared to the reaction of As(III) with ·OH radical during TiO2 PCO. Monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) are readily degraded upon TiO2 PCO. DMA is oxidized to MMA as the intermediate and arsenate as the final product. For dilute solutions, TiO2 also may be applicable as an adsorbent for direct removal of arsenic species, namely As(III), As(V), MMA and DMA, all of which are strongly adsorbed, thus eliminating the need for a multi-step treatment process. ^ Phenylarsonic acid (PA) was subjected to gamma radiolysis under hydroxyl radical generating conditions, which showed rapid degradation of PA. Product analysis and computational calculation both indicate the arsenate group is an ortho, para director. Our results indicate · OH radical mediated processes should be effective for the remediation of phenyl substituted arsonic acids. ^ While hydroxyl radical generating methods, specifically AOTs, appear to be promising methods for the treatment of a variety of arsenic compounds in aqueous media, pilot studies and careful economic analyses will be required to establish the feasibility of AOTs applications in the removal of arsenic. ^

Space division multiple access for wireless sensor networks

This dissertation proposed a self-organizing medium access control protocol (MAC) for wireless sensor networks (WSNs). The proposed MAC protocol, space division multiple access (SDMA), relies on sensor node position information and provides sensor nodes access to the wireless channel based on their spatial locations. SDMA divides a geographical area into space divisions, where there is one-to-one map between the space divisions and the time slots. Therefore, the MAC protocol requirement is the sensor node information of its position and a prior knowledge of the one-to-one mapping function. The scheme is scalable, self-maintaining, and self-starting. It provides collision-free access to the wireless channel for the sensor nodes thereby, guarantees delay-bounded communication in real time for delay sensitive applications. This work was divided into two parts: the first part involved the design of the mapping function to map the space divisions to the time slots. The mapping function is based on a uniform Latin square. A Uniform Latin square of order k = m 2 is an k x k square matrix that consists of k symbols from 0 to k-1 such that no symbol appears more than once in any row, in any column, or in any m x in area of main subsquares. The uniqueness of each symbol in the main subsquares presents very attractive characteristic in applying a uniform Latin square to time slot allocation problem in WSNs. The second part of this research involved designing a GPS free positioning system for position information. The system is called time and power based localization scheme (TPLS). TPLS is based on time difference of arrival (TDoA) and received signal strength (RSS) using radio frequency and ultrasonic signals to measure and detect the range differences from a sensor node to three anchor nodes. TPLS requires low computation overhead and no time synchronization, as the location estimation algorithm involved only a simple algebraic operation.

Seismic performance of hybrid fiber reinforced polymer-concrete pier columns

As part of a multi-university research program funded by NSF, a comprehensive experimental and analytical study of seismic behavior of hybrid fiber reinforced polymer (FRP)-concrete column is presented in this dissertation. Experimental investigation includes cyclic tests of six large-scale concrete-filled FRP tube (CFFT) and RC columns followed by monotonic flexural tests, a nondestructive evaluation of damage using ultrasonic pulse velocity in between the two test sets and tension tests of sixty-five FRP coupons. Two analytical models using ANSYS and OpenSees were developed and favorably verified against both cyclic and monotonic flexural tests. The results of the two methods were compared. A parametric study was also carried out to investigate the effect of three main parameters on primary seismic response measures. The responses of typical CFFT columns to three representative earthquake records were also investigated. The study shows that only specimens with carbon FRP cracked, whereas specimens with glass or hybrid FRP did not show any visible cracks throughout cyclic tests. Further monotonic flexural tests showed that carbon specimens both experienced flexural cracks in tension and crumpling in compression. Glass or hybrid specimens, on the other hand, all showed local buckling of FRP tubes. Compared with conventional RC columns, CFFT column possesses higher flexural strength and energy dissipation with an extended plastic hinge region. Among all CFFT columns, the hybrid lay-up demonstrated the highest flexural strength and initial stiffness, mainly because of its high reinforcement index and FRP/concrete stiffness ratio, respectively. Moreover, at the same drift ratio, the hybrid lay-up was also considered as the best in term of energy dissipation. Specimens with glassfiber tubes, on the other hand, exhibited the highest ductility due to better flexibility of glass FRP composites. Furthermore, ductility of CFFTs showed a strong correlation with the rupture strain of FRP. Parametric study further showed that different FRP architecture and rebar types may lead to different failure modes for CFFT columns. Transient analysis of strong ground motions showed that the column with off-axis nonlinear filament-wound glass FRP tube exhibited a superior seismic performance to all other CFFTs. Moreover, higher FRP reinforcement ratios may lead to a brittle system failure, while a well-engineered FRP reinforcement configuration may significantly enhance the seismic performance of CFFT columns.

Mechanistic studies on the advanced oxidation and photochemical transformation of cyanotoxins (microcystins)

The increased occurrence of cyanobacteria (blue-green algae) blooms and the production of associated cyanotoxins have presented a threat to drinking water sources. Among the most common types of cyanotoxins found in potable water are microcystins (MCs), a family of cyclic heptapeptides containing substrates. MCs are strongly hepatotoxic and known to initiate tumor promoting activity. The presence of sub-lethal doses of MCs in drinking water is implicated as one of the key risk factors for an unusually high occurrence of primary liver cancer. ^ A variety of traditional water treatment methods have been attempted for the removal of cyanotoxins, but with limited success. Advanced Oxidation Technologies (AOTs) are attractive alternatives to traditional water treatments. We have demonstrated ultrasonic irradiation and UV/H2O2 lead to the degradation of cyanotoxins in drinking water. These studies demonstrate AOTs can effectively degrade MCs and their associated toxicity is dramatically reduced. We have conducted detailed studies of different degradation pathways of MCs and conclude that the hydroxyl radical is responsible for a significant fraction of the observed degradation. Results indicate preliminary products of the sonolysis of MCs are due to the hydroxyl radical attack on the benzene ring and substitution and cleavage of the diene of the Adda peptide residue. AOTs are attractive methods for treatment of cyanotoxins in potable water supplies. ^ The photochemical transformation of MCs is important in the environmental degradation of MCs. Previous studies implicated singlet oxygen as a primary oxidant in the photochemical transformation of MCs. Our results indicate that singlet oxygen predominantly leads to degradation of the phycocyanin, pigments of blue green algae, hence reducing the degradation of MCs. The predominant process involves isomerization of the diene (6E to 6Z) in the Adda side chain via photosensitized isomerization involving the photoexcited phycocyanin. Our results indicate that photosensitized processes play a key role in the environmental fate and elimination of MCs in the natural waters. ^

Interactions of different arsenic species with thols: Chemical and biological implications

Arsenic has been classified as a group I carcinogen. It has been ranked number one in the CERCLA priority list of hazardous substances due to its frequency, toxicity and potential for human exposure. Paradoxically, arsenic has been employed as a successful chemotherapeutic agent for acute promyelocytic leukemia and has found some success in multiple myeloma. Since arsenic toxicity and efficacy is species dependent, a speciation method, based on the complementary use of reverse phase and cation exchange chromatography, was developed. Inductively coupled plasma mass spectrometer (ICP-MS), as an element specific detector, and electrospray ionization mass spectrometer (ESI-MS), as a molecule specific detector, were employed. Low detection limits in the µg. L−1 range on the ICP-MS and mg. L−1 range on the ESI-MS were obtained. The developed methods were validated against each other through the use of a Deming plot. With the developed speciation method, the effects of both pH on the stability of As species and reduced glutathione (GSH) concentration on the formation and stability of arsenic glutathione complexes were studied. To identify arsenicals in multiple myeloma (MM) cell lines post arsenic trioxide (ATO) and darinaparsin (DAR) incubation, an extraction method based on the use of ultrasonic probe was developed. Extraction tools and solvents were evaluated and the effect of GSH concentration on the quantitation of arsenic glutathione (As-GSH) complexes in MM cell extracts was studied. The developed method was employed for the identification of metabolites in DAR incubated cell lines where the effect of extraction pH, DAR incubation concentration and incubation time on the relative distribution of the As metabolites was assessed. A new arsenic species, dimethyarsinothioyl glutathione (DMMTA V-GS), a pentavalent thiolated arsenical, was identified in the cell extracts through the use of liquid chromatography tandem mass spectrometry. The formation of the new metabolite in the extracts was dependent on the decomposition of s-dimethylarsino glutathione (DMA(GS)). These results have major implications in both the medical and toxicological fields of As because they involve the metabolism of a chemotherapeutic agent and the role sulfur compounds play in this mechanism.

A model for continuous measurement of drilled shaft diameter during construction

Non-Destructive Testing (NDT) of deep foundations has become an integral part of the industry's standard manufacturing processes. It is not unusual for the evaluation of the integrity of the concrete to include the measurement of ultrasonic wave speeds. Numerous methods have been proposed that use the propagation speed of ultrasonic waves to check the integrity of concrete for drilled shaft foundations. All such methods evaluate the integrity of the concrete inside the cage and between the access tubes. The integrity of the concrete outside the cage remains to be considered to determine the location of the border between the concrete and the soil in order to obtain the diameter of the drilled shaft. It is also economic to devise a methodology to obtain the diameter of the drilled shaft using the Cross-Hole Sonic Logging system (CSL). Performing such a methodology using the CSL and following the CSL tests is performed and used to check the integrity of the inside concrete, thus allowing the determination of the drilled shaft diameter without having to set up another NDT device.^ This proposed new method is based on the installation of galvanized tubes outside the shaft across from each inside tube, and performing the CSL test between the inside and outside tubes. From the performed experimental work a model is developed to evaluate the relationship between the thickness of concrete and the ultrasonic wave properties using signal processing. The experimental results show that there is a direct correlation between concrete thicknesses outside the cage and maximum amplitude of the received signal obtained from frequency domain data. This study demonstrates how this new method to measuring the diameter of drilled shafts during construction using a NDT method overcomes the limitations of currently-used methods. ^ In the other part of study, a new method is proposed to visualize and quantify the extent and location of the defects. It is based on a color change in the frequency amplitude of the signal recorded by the receiver probe in the location of defects and it is called Frequency Tomography Analysis (FTA). Time-domain data is transferred to frequency-domain data of the signals propagated between tubes using Fast Fourier Transform (FFT). Then, distribution of the FTA will be evaluated. This method is employed after CSL has determined the high probability of an anomaly in a given area and is applied to improve location accuracy and to further characterize the feature. The technique has a very good resolution and clarifies the exact depth location of any void or defect through the length of the drilled shaft for the voids inside the cage. ^ The last part of study also evaluates the effect of voids inside and outside the reinforcement cage and corrosion in the longitudinal bars on the strength and axial load capacity of drilled shafts. The objective is to quantify the extent of loss in axial strength and stiffness of drilled shafts due to presence of different types of symmetric voids and corrosion throughout their lengths.^