Terahertz and autofluorescence imaging technologies are combined for accurate breast and oral cancer margin detection. More than thirty fresh tissue samples are imaged in this study. Cancer progression causes structural, and metabolic changes which can be probed effectively by combining Terahertz and Autofluorescence technologies and using advanced machine learning algorithms. To train the Machine Learning algorithm, the cancer and noncancer regions in Terahertz and fluorescence images are identified by overlapping with histopathology images. This study confirms that the combination of multiple spectroscopy techniques and Machine Learning algorithms has the potential to achieve better diagnostic accuracy in fresh cancer tissue.
In this paper, Continuous Wave Terahertz system is utilized to image freshly excised oral and breast tissues. The THz images show significant contrast between tumour and adjacent normal/fat tissues in both breast and oral cancer. The obtained images are compared with the histopathology images for the confirmation. Advanced Artificial Intelligence algorithm is developed in which the THz images at each pixel is labelled based on overlapping of THz and pathology images. The results demonstrate the potential of low frequency THz imaging to differentiate benign and malignant tissue in freshly excised samples.
Nanosilica incorporation in cement has been of great interest for its accelerating effect on the hydration process as well as providing higher compressive strength and durability. During hydration, cement constituents, such as tricalcium silicate (C3S) and dicalcium silicate (β-C2S) react with water to form key hydration products, such as calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)2, CH). In this work, Mid-infrared and Terahertz spectroscopy has been employed to study the effect of nanosilica incorporation in cement hydration. The acceleration due to the presence of nanosilica has been demonstrated by the reduction in peak intensity of the resonances related to Si-O stretching (925 cm-1) and Si-O bending modes (520 cm-1) which confirms faster consumption of the cement constituents. Furthermore, the formation of the hydration products C-S-H and CH is vital since C-S-H contributes to the early stage strength development in concrete and CH is an undesirable hydration product. CH content in the cement matrix can be minimized by nanosilica incorporation resulting in pozzolanic reactions as CH reacts with nanosilica to produce more C-S-H. Formation of C-S-H has been demonstrated by the prominence of the resonances related to deformations of SiO4 chains around 455 cm-1 and 1100 cm-1. The type of C-S-H can also be predicted by tracking the shift of resonances to higher/lower wavenumbers, denoting polymerization which is more prominent for the nanosilica incorporated sample. Formation of the other key hydration product is observed as the resonance related to CH around 314 cm-1 is seen to get sharper with hydration. This study has also been able to show a reduced carbonation effect in the nanosilica incorporated sample as evident from the less prominent carbonate peaks around 1425 cm-1 after 28 days of hydration.
Ordinary Portland Cement (OPC) primarily constitutes Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) making up 60–70 % and 20–30 % of the cement matrix respectively. During cement hydration, C3S starts to react faster contributing to early stage strength in comparison to C2S, which reacts slowly and is responsible for long term strength development of concrete. C2S is manufactured at lower temperatures compared to C3S, resulting in lesser emission of carbon dioxide as compared to C3S. Moreover, C2S produces less Ca(OH)2 than C3S, which is an undesirable hydration product. Thus, incorporation of greater percentages of C2S in cement matrix will be highly beneficial, provided it’s early stage reactivity can be increased. One of the key methods to increase reactivity of C2S is incorporating nanosilica which accelerates the hydration along with the formation of greater amount of calcium silicate hydrate (C-S-H) which is responsible for the strength development of concrete. Hence, understanding the acceleration in hydration dynamics of the nanosilica incorporated β-C2S can help in optimizing the percentages of C3S and C2S in cement. In this study, Terahertz spectroscopy has been employed to track the acceleration of hydration of C2S due to the addition of nanosilica. Results show early stage reduction in peak height of the resonance around 520 cm-1 in nanosilica incorporated sample which indicates faster hydration of C2S during hydration. Furthermore, early stage formation of a prominent resonance around 453 cm-1 for the nanosilica incorporated C2S sample implies formation of C-S-H like structures confirming the accelerated hydration rate.
Proton Exchange Membrane (PEM) fuel cells are increasingly gaining importance as a clean energy source. PEMs need to possess high proton conductivity and should be chemically and mechanically stable in the fuel cell environment. Proton conductivity of PEM in fuel cells is directly proportional to water content in the membrane. Among the various PEMs available, Nafion has high proton conductivity even with low water content compared to SPEEK (Sulfonated Poly(ether ether ketone)) but is also expensive. SPEEK membranes and it’s composites have better mechanical properties and have comparatively higher thermal stability. Operating the fuel cell at higher temperatures and at the same time maintaining the water content of the membrane is always a great challenge. In this paper, to increase water retention capacity, Nafion, SPEEK and it’s composite (SPEEK PSSA-CNT) membranes are exposed to Ultra-Violet (UV) radiation for varied times. Terahertz Spectroscopy, in both pulsed and CW mode has been used as an efficient tool to quantify the water retention of the membrane. Results using Terahertz spectroscopy show that even though the initial water absorption capacity of Nafion membranes is more, SPEEK membranes and it’s composites show considerable improvement in the water retention capacity upon high intensity UV irradiation.
THz rays have higher penetration depth compared to infrared rays and hence can be effectively used to measure tablet coating thickness. In addition, THz wavelength (1 mm - 0.1 mm) provides an optimal depth resolution for the thickness measurement. This method can be non-invasive and hence ideal for inline quality monitoring. Tablet coating thickness is one of the major parameters of interest in Process Analytical Technology (PAT). In this paper, a reflection mode Continuous Wave (CW) Terahertz (THz) system has been employed to measure the tablet coating thickness. A frequency scan of the sample has been carried out from 0.1 THz to 1.1 THz and the reflection coefficient of the sample is inverse fourier transformed to obtain the tablet thickness. The calculated thickness has also been validated using the optical microscope. Results show that the thickness can be measured with considerable accuracy.
Terahertz (THz) technology is an active area of research with various applications in non-intrusive imaging and spectroscopy. Very few organic molecules have significant resonances below 1 THz. Understanding the origin of low frequency THz modes in these molecules and their absence in other molecules could be extremely important in design and engineering molecules with low frequency THz resonances. These engineered molecules can be used as THz tags for anti-counterfeiting applications. Studies show that low frequency THz resonances are commonly observed in molecules having higher molecular mass and weak intermolecular hydrogen bonds. In this paper, we have explored the possibility of enhancing the strength of THz resonances below 1 THz through electronegative atom substitution. Adding an electronegative atom helps in achieving higher hydrogen bond strength to enhance the resonances below 1 THz. Here acetanilide has been used as a model system. THz-Time Domain Spectroscopy (THz-TDS) results show that acetanilide has a small peak observed below 1 THz. Acetanilide can be converted to 2-fluoroacetanilide by adding an electronegative atom, fluorine, which doesn’t have any prominent peak below 1 THz. However, by optimally choosing the position of the electronegative atom as in 4-fluoroacetanilide, a significant THz resonance at 0.86 THz is observed. The origin of low frequency resonances can be understood by carrying out Density Functional Theory (DFT) simulations of full crystal structure. These studies show that adding an electronegative atom to the organic molecules at an optimized position can result in significantly enhanced resonances below 1 THz.
Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.
Concrete, a mixture of cement, coarse aggregate, sand and filler material (if any), is widely used in the construction industry. Cement, mainly composed of Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) reacts readily with water, a process known as hydration. The hydration process forms a solid material known as hardened cement paste which is mainly composed of Calcium Silicate Hydrate (C-S-H), Calcium Hydroxide and Calcium Carbonate. To quantify the critical hydration level, an accurate and fast technique is highly desired. However, in conventional XRD technique, the peaks of the constituents of anhydrated and hydrated cement cannot be resolved properly, where as Mid-infrared (MIR) spectroscopy has low penetration depth and hence cannot be used to determine the hydration level of thicker concrete samples easily. Further, MIR spectroscopy cannot be used to effectively track the formation of Calcium Hydroxide, a key by-product during the hydration process. This paper describes a promising approach to quantify the hydration dynamics of cement using Terahertz (THz) spectroscopy. This technique has been employed to track the time dependent reaction mechanism of the key constituents of cement that react with water and form the products in the hydrated cement, viz., C-S-H, Calcium Hydroxide and Calcium Carbonate. This study helps in providing an improved understanding on the hydration kinetics of cement and also to optimise the physio-mechanical characteristics of concrete.
Terahertz (THz) frequency band lies between the microwave and infrared region of the electromagnetic spectrum. Molecules having strong resonances in this frequency range are ideal for realizing "Terahertz tags" which can be easily incorporated into various materials. THz spectroscopy of molecules, especially at frequencies below 10 THz, provides valuable information on the low frequency vibrational modes, viz. intermolecular vibrational modes, hydrogen bond stretching, torsional vibrations in several chemical and biological compounds. So far there have been very few attempts to engineer molecules which can demonstrate customizable resonances in the THz frequency region. In this paper, Diamidopyridine (DAP) based molecules are used as a model system to demonstrate engineering of THz resonances (< 10 THz) by fine-tuning the molecular mass and bond strengths. Density Functional Theory (DFT) simulations have been carried out to explain the origin of THz resonances and factors contributing to the shift in resonances due to the addition of various functional groups. The design approach presented here can be easily extended to engineer various organic molecules suitable for THz tags application.
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