Experimental demonstration of Ge2Sb2Te5 loaded 1-D plasmonic metasurface perfect absorber for near-IR wavelength regime.

Inclusion of a phase change material such as germanium-antimony-telluride (Ge2Sb2Te5 or GST) enhances the performance of plasmonic metasurface absorbers (PMAs). One-dimensional (1-D) plasmonic metasurfaces (PMs) support the excitation of surface plasmon modes for the normal incidence of transverse magnetically (TM) polarized light. The 1-D PMAs absorb incident light because of their confinement in the groove region, which is possible because of the surface plasmon modes excited at the metal-dielectric interface. A thin layer of the phase change material enhances the absorption of incident light because of the increasing strength of the confined electromagnetic field in the vicinity of the PMA. We developed a GST loaded, low cost, 1-D PMA for the absorption of near-infrared (NIR) light (740-920 nm). The PMA was fabricated using an Ag coated 1-D patterned polycarbonate, which was obtained from a commercial digital versatile disk (DVD). A 1-D PMA of 1 cm2 in size obtained from a DVD was coated with a GST layer of 8 nm in thickness to achieve the maximum absorption of 99.56% for the hexagonal closed packed (h.c.p.) crystalline state of the GST loaded layer. Control experiments were performed for different temperatures and different thicknesses of the GST layer for achieving an optimal performance nearing perfect absorption. Electric and magnetic field profiles were simulated for the normal incidence of TM-polarized light to understand the underlying physics of the light-matter interaction with the PMA. Such a PMA can be used to develop various cost-effective optical devices, such as optical sensors, optical filters, photodetectors, and heat absorbing photonic windows in the NIR wavelength regime.

Early Experience with Sine Wave Technique for Superficialization of a difficult to cannulate Arterio Venous Fistula.

OBJECTIVE: To highlight safety and efficacy of sine wave technique (SWT) in superficializing deep arterio venous fistula (AVF) and managing infiltrations and other complications. METHODS: It is a single center observational study done from Jul 2017 to July 2020. All successive cases of deep AVFs, aneurysm / pseudoaneurysms of AVFs, and AVFs requiring open venoplasty were managed with SWT. Data was collected prospectively and analyzed. SWT is based on random pattern skin flaps. Using ultrasound, a line is marked on either side of centre line (AVF) at a distance of approximately 1.5-2 cm. A sine wave is drawn starting from either of the lines to the other with multiple crests and troughs. The base of flap should be double the height of the flap, that is, about 3-4 cm. Skin is incised and flaps are raised at level of AVF. Excess fat is removed. A sliver of unhealthy skin can be sacrificed if required. Flaps are sutured back to restore sine wave continuity. RESULTS: SWT was used in a total of eleven patients. Median age was 58 years (range 10-67 years). Eight were females and three males. One was radio-cephalic and rest were brachio-cephalic AVFs. Eight AVFs were deep with median depth of 10.25mm (range 8-13mm), median body mass index of 25.5 kg/m2 (range 23.9-26.5kg/m2), median vein diameter of 7 mm (range 6-8 mm), and median flow rate of 1137.5ml/min (range 650- 1380 ml/min). Out of eight, four AVFs presented with infiltration. In other three, SWT was used for exposing AVF to treat underlying pathology (one case each of aneurysm, pseudoaneurysm & stenosis). Ten cases were done under local or regional anesthesia and one under general anesthesia. There was no peri-operative mortality or loss of AVF. Transient limb oedema developed in one case. Median time to cannulate was 20 days (range 13-28 days). Median follow up was 13 months (range 6 - 31months). Cumulative patency at 18 months was 90% (95% CI 47.3%-98.53%) and 45 % (95% CI 9.9%-87.1%) at 24months and at the end of the study. CONCLUSION: SWT is safe and effective in superficialization of deep / difficult to cannulate AVF as well a good approach to treat complications like infiltration. Post procedure cannulation time is reasonably short.

Unveiling the interplay between induced native defects and room temperature magnetic ordering in titanium deficient disordered-TiO2 nanoparticles.

Understanding the origin of magnetic ordering in an undoped semiconductor with native defects is an open question, which is being explored actively in research. In this investigation, the interplay between magnetic ordering and excess induced native defects in undoped anatase TiO2 nanoparticles is explained using an experimental and theoretical approach. It is demonstrated that structurally disordered TiO2 nanoparticles with a high concentration of native defects such as titanium interstitials and oxygen vacancies are synthesized using controlled atmospheric rapid cooling (i.e. quenching) process. The structural disorders in the lattice have been examined using various spectroscopic and microscopic analyses revealed the existence of Ti deficiency in both pristine and quenched TiO2 nanoparticles. A possible origin of magnetic ordering in titanium deficient anatase TiO2 system is elucidated based on first-principle calculations. It was found that the overall magnetic moment of Ti deficient TiO2 system is determined by the distance between Ti interstitials and its neighboring vacancies (i.e. either V Ti or V Os). However, quenched TiO2 nanoparticles possess excess Ti interstitials, Ti and O vacancies and therefore the net magnetic moment of the system is reduced due to anti-ferromagnetically coupled neighboring Tilattice ions.

Enhanced intrinsic fluorescence from carboxidized nano-sculptured thin films of silver and their application for label free dual detection of glycated hemoglobin.

Enhanced intrinsic fluorescence (~x103) from novel carboxidized nanosculptured thin films (CO-nSTFs) of silver is reported. The sources of intrinsic fluorescence, confirmed by X-ray photoelectron spectroscopy, are Ag2O grains and residual carbon formed on the outer layer of silver nSTFs when exposed to air, while the localized surface plasmons on silver nSTFs enhance this intrinsic fluorescence. The CO-nSTFs are optimized with respect to porosity for the maximum enhancement. A sensor developed by using the self-assembled monolayer technique on optimized CO-nSTF is used for the label free detection of glycated hemoglobin, performed by simultaneously using fluorescence imaging and spectroscopy. The specificity of the sensor is established from control experiments on hemoglobin. These novel nanorod like intrinsically fluorescent CO-nSTFs pose huge potential in label free biosensing, light sources, imaging and many more applications.

Irrigating okra with secondary treated municipal wastewater: Observations regarding plant growth and soil characteristics.

The present study was carried out to probe the agronomic response of hybrid cultivar of okra (Hibiscus esculentus L. var. JK 7315) grown in secondary treated municipal wastewater irrigated soil with field investigations. The concentrations of the municipal wastewater viz., 10%, 20%, 40%, 60%, 80%, and 100% along with the control (groundwater) were used for the irrigation of the H. esculentus. The study revealed that the concentrations of the municipal wastewater showed significant (p < 0.05/p < 0.01) effect on the soil parameters after wastewater fertigation in comparison to groundwater in both the seasons. The maximum agronomic performance of the H. esculentus was recorded with 60% concentration of the municipal wastewater in both the seasons. The contamination factor of heavy metals varied in the H. esculentus plants and soils. In the H. esculentus plants, following fertigation with municipal wastewater, the contamination factor of manganese was the highest, while that of chromium was the lowest. Intermediate contamination factor were observed for zinc, copper, and cadmium. Therefore, secondary treated municipal wastewater can be used as an agro-fertigant after appropriate dilution (up to 60%) to achieve the maximum yield of the H. esculentus.

Self-referenced sensor utilizing extra-ordinary optical transmission from metal nanoslits array.

We report the first self-referenced sensor based on the extraordinary optical transmission (EOT) of metal-nanoslits array in the near-infra-red (NIR) telecommunication window of the electromagnetic spectrum. The nanoslits array shows two enhanced transmission peaks, out of which one shows a red shift with an increase in the refractive index of the analyte medium, while the other remains fixed. We demonstrate the detection of small amounts of water in ethanol using the nanoslits array chip. The present study might be useful in developing ultra-small biosensor chips integrated to optical fibers for online monitoring and remote sensing applications.

Highly sensitive and specific detection of E. coli by a SERS nanobiosensor chip utilizing metallic nanosculptured thin films.

A nanobiosensor chip, utilizing surface enhanced Raman spectroscopy (SERS) on nanosculptured thin films (nSTFs) of silver, was shown to detect Escherichia coli (E. coli) bacteria down to the concentration level of a single bacterium. The sensor utilizes highly enhanced plasmonic nSTFs of silver on a silicon platform for the enhancement of Raman bands as checked with adsorbed 4-aminothiophenol molecules. T-4 bacteriophages were immobilized on the aforementioned surface of the chip for the specific capture of target E. coli bacteria. To demonstrate that no significant non-specific immobilization of other bacteria occurs, three different, additional bacterial strains, Chromobacterium violaceum, Paracoccus denitrificans and Pseudomonas aeruginosa were used. Furthermore, experiments performed on an additional strain of E. coli to address the specificity and reusability of the sensor showed that the sensor operates for different strains of E. coli and is reusable. Time resolved phase contrast microscopy of the E. coli-T4 bacteriophage chip was performed to study its interaction with bacteria over time. Results showed that the present sensor performs a fast, accurate and stable detection of E. coli with ultra-small concentrations of bacteria down to the level of a single bacterium in 10 µl volume of the sample.

SERS biosensor using metallic nano-sculptured thin films for the detection of endocrine disrupting compound biomarker vitellogenin.

A biosensor chip is developed for the detection of a protein biomarker of endocrine disrupting compounds, vitellogenin (Vg) in aquatic environment. The sensor chip is fabricated by immobilizing anti-Vg antibody on 4-Aminothiophenol (4-ATP) coated nanosculptured thin films (nSTFs) of silver on Si substrates. The biosensor is based on the SERS of 4-ATP, enhanced by the Ag nSTFs. Before the fabrication of the sensor, the performance of the enhancement is optimized with respect to the porosity of nSTFs. Further, the biosensor is developed on the nSTF with optimized enhancement. The SERS signals are recorded from the sensor chip for varying concentrations of Vg. A control experiment is performed on another similar protein Fetuin to confirm the specificity of the sensor. The repeatability and reusability of the sensor, along with its shelf life are also checked. The limit of detection of the sensor is found to be 5 pg mL −1 of Vg in PBS within our experimental window. Apart from high sensitivity, specificity and reusability, the present sensor provides additional advantages of miniaturization, requirement of very small volumes of the analyte solution (15 µL) and fast response as compared to conventional techniques e.g., ELISA, as its response time is less than 3 minutes.

Irrigational impact of distillery effluent on Abelmoschus esculentus L. Okra with special reference to heavy metals.

The present study was performed under natural environment to assess levels of different heavy metals in soil and Abelmoschus esculentus plants along with soil microbial population irrigated with five rates of distillery effluent (DE) viz. 10, 25, 50, 75 and 100 % concentration in comparison with control (Bore well water). Results revealed that among various concentrations of DE, irrigation with 100 % DE significantly (P < 0.001) increased Zn (+63.46 %), Cu (+292.37 %), Zn (+3763.63 %), Cd (+264.29 %), Ni (+48.39 %) and Cr (+815.74 %), while decreased total bacteria (-45.23 %), fungi (-17.77 %) and actinomycetes (-42.57 %) in the soil. Enrichment factor of various heavy metals for soil was in the order Ni > Cr > Cd > Zn > Cu, and for A. esculentus plants, it was in the order Ni > Cr > Cu > Cd > Zn after irrigation with distillery effluent. The enrichment factor value was found maximum for Ni in comparison to other metals at 100 % DE concentration as compared with BWW. However, the values of these metals were below the recommended permissible limit.

Accumulation of heavy metals in Spinacia oleracea irrigated with paper mill effluent and sewage.

The present study on heavy metal contamination in soil and their accumulation in edible part (leaves) and roots of Spinacia oleracea (Spinach) on irrigation with paper mill effluent (PME)/sewage revealed that there was significant increase in the nickel (Ni, +227.17 %) content of the soil irrigated with PME, whereas in the soil irrigated with sewage chromium (Cr, +274.84 %), iron (Fe, +149.56 %), and cadmium (Cd, +133.39 %), contents were increased appreciably. The value of enrichment factor (EF) for Ni (3.27) indicated moderate enrichment in PME-irrigated soil. The EF of Fe, zinc (Zn), Cd, and Cr were <2 in PME effluent-irrigated soil which showed deficiency of minimal enrichment. In sewage irrigated soil, EF value for Cr, Fe, and Cd indicated moderate enrichment, while the values for Zn and Ni indicated deficiency of minimal enrichment. Among various metallic concentrations, the maximum concentration of Fe was observed in leaves (400.12 ± 11.47 mg/kg) and root (301.41 ± 13.14 mg/kg) of S. oleracea after irrigation with PME, whereas the maximum concentrations of Fe was found in leaves (400.49 ± 5.97 mg/kg) and root (363.94 ± 11.37 mg/kg) of S. oleracea after irrigation with sewage for 60 days. The bioaccumulation factor value was found maximum for Cd (2.23) in the plants irrigated with PME while that of Fe (0.90) in the plants irrigated with sewage. The undiluted use of PME/sewage for irrigation increased the concentration of Cr, Cd, Zn, Ni, and Fe metals which were accumulated in S. oleracea, posing a potential threat to human health from this practice of irrigation.

Agro-potentiality of distillery effluent on soil and agronomical characteristics of Abelmoschus esculentus L. (okra).

The present study showed that irrigation of soil with different effluent concentrations (10, 25, 50, 75, and 100 %) of distillery effluent (DE) for 60 days resulted in significant (P < 0.001) changes in moisture content; electrical conductivity (EC), pH, chlorides (Cl(-)), total organic carbon (TOC), exchangeable sodium (Na(+)), available potassium (K(+)), calcium (Ca(2+)), magnesium (Mg(2+)), iron (Fe(2+)), total Kjeldahl nitrogen (TKN), available phosphorus (P), and sulfate (SO4 (2-)) of soil. The non-significant (P > 0.05) changes were observed for water-holding capacity and bulk density of the soil. Among various concentrations of DE irrigation, irrigation with 100 % effluent concentration increased moisture content, (24.85 %), EC (77.88 %), Cl(-) (285.95 %), TOC (3,171.42 %), exchangeable Na(+) (241.04 %), available K(+) (52.49 %), Ca(2+) (990.37 %), Mg(2+) (1,751.72 %), TKN (1,417.00 %), available P (305.00 %), and SO4 (2-) (75.32 %) in the soil and decreased pH (-20.22 %). The more stimulation in agronomical parameters such as shoot length, root length, number of leaves, flowers, pods, dry weight, fresh weight, chlorophyll content, leaf area index, and crop yield of A. esculentus were observed to be inversely proportional to the concentration of effluent water, with the best results being obtained at a dilution of 25 % of DE concentration.

Giant Extra-Ordinary Near Infrared Transmission from Seemingly Opaque Plasmonic Metasurface: Sensing Applications.

In the present study, we report giant extra-ordinary transmission of near infrared (NIR) light, more than 90%, through a seemingly opaque plasmonic metasurface, which consists of two metal nano-slits arrays (MNSAs) with alternate opening arrangements. By using perfect coupling of the plasmonic modes formed between the sharp edges of the upper and lower MNSAs of silver, a giant, wavelength selective transmission could be obtained. The study is accompanied by optimization of electromagnetic (EM) field coupling for different interlayer spacings and lateral overlap between the two MNSAs to understand their significance in light transmission through the metasurface. The interlayer spacing between the MNSAs works as the transmitting channel for light. The optimization of performance with different fill factors and plasmonic metals was performed as well. Because of the excitation of extended surface plasmons (ESPs) generated at both the MNSAs, the metasurface can be used for refractive index (RI) sensing as one of its applications by using a transparent and flexible polymer, such as polydimethylsiloxane (PDMS), as substrate. The maximum sensitivity which could be achieved for the optimal configuration of the metasurface was 1435.71 nm/RIU, with a figure of merit (FOM) of 80 RIU-1 for 90.45% optical transmission of light for the refractive index variation of analyte medium from 1.33 to 1.38 RIU. The present study strengthens the concept of light funneling through subwavelength structures due to plasmons, which are responsible for light transmission through this seemingly opaque metasurface and finds use in highly sensitive, flexible, and cost-effective EOT-based sensors.

Haemorrhagic Brain Metastasis From Malignant Pleural Mesothelioma: A Rare Case.

Malignant pleural mesothelioma (MPM) typically has a short median survival of only a few months from diagnosis, with death usually due to thoracic disease. This has led to the belief in the past that mesothelioma rarely has distant metastasis, with cerebral metastasis accounting for only 3%. The multiple cases of brain metastasis from MPM recorded so far were discovered after death at autopsy. This report describes a rare case of known malignant mesothelioma with distant haemorrhagic metastasis to the brain, reviews current literature about its metastatic potential to the brain and discusses prognosis and management. We also review the imaging evaluation in known MPM patients with suspected intracranial involvement and describe typical imaging findings of parenchymal brain metastasis on computed tomography (CT) and magnetic resonance imaging (MRI).

Radiological Appearance and Imaging Techniques in the Diagnosis of Advanced Central Pontine Myelinolysis.

Conventional magnetic resonance imaging (MRI) and computed tomography (CT) are used to diagnose central pontine myelinolysis (CPM), which is seen in the setting of osmotic changes, typically with the rapid correction of hyponatremia. However, they typically follow clinical symptoms and fail to detect myelinolytic lesions within the first two weeks, limiting their efficacy in early diagnosis. CPM can mimic brainstem ischaemic changes on CT head and a glioma on MRI. This case reviews the relationship between radiological changes seen with clinical symptoms and serum sodium levels, combined with reviewing pioneering advances in radiomic analysis, including diffusion-weighted MRI, CT brain perfusion and MR spectroscopy.

Acute Disseminated Encephalomyelitis Following Thoracic Endovascular Aortic Repair.

Acute disseminated encephalomyelitis (ADEM) is a central nervous system demyelinating condition. The postulated etiology is an autoimmune reaction, however, the mechanistic details are yet unknown. While infection and immunization are the most prevalent precipitating causes of ADEM, we postulate that radiopaque contrast material might have played a role as an immunological trigger. This presentation is unusual and has not been recorded so far. This case also emphasizes the challenges involved in evaluating emerging neurological problems following a period of intubation/sedation among these patients. We present a patient who passed away due to the manifestations of ADEM following admission to the intensive care unit after thoracic endovascular aortic repair for type B aortic dissection. Magnetic resonance imaging (MRI) performed following multiple attempts at sedation weaning demonstrated typical features of this condition. Clinicians and radiologists should be diligent and consider ADEM as a differential diagnosis when treating patients who present with neurological symptoms following radiological interventional procedures and have a high index suspicion to reduce mortality and achieve satisfactory clinical outcomes.

Simulation of a localized surface-plasmon-resonance-based fiber optic temperature sensor.

A fiber optic temperature sensor based on localized surface plasmon resonance of spherical gold nanoparticles embedded in a dielectric layer around the unclad core of a small portion of the fiber has been analyzed. Simulations have been carried out for a number of dielectric materials that show considerable changes in their refractive indices due to a change in the temperature in addition to having refractive indices higher than that of the fiber core. The analysis is based on the spectral interrogation method. The surface plasmons in metal nanoparticles have been excited by the light refracted through the core and the dielectric interface. The sensitivity of the sensor has been determined for each dielectric material used, and it is found to be the maximum for CdGeP(2) as a sensing medium. The temperature sensing range of the present sensor is also wide because the melting points of the metal and the fiber core, as well as the sensing medium, are large. The proposed fiber optic temperature sensor is compact, light weight, and highly sensitive with a wide temperature sensing range.

Probing phase transition in VO2 with the novel observation of low-frequency collective spin excitation.

VO2 is well known for its first order, reversible, metal-to-insulator transition (MIT) along with a simultaneous structural phase transition (SPT) from a high-temperature metallic rutile tetragonal (R) to an insulating low-temperature monoclinic (M1) phase via two other insulating metastable phases of monoclinic M2 and triclinic T. At the same time, VO2 gains tremendous attention because of the half-a-century-old controversy over its origin, whether electron-electron correlation or electron-phonon coupling trigger the phase transition. In this regard, V1-xMgxO2 samples were grown in stable phases of VO2 (M1, M2, and T) by controlled doping of Mg. We have observed a new collective mode in the low-frequency Raman spectra of all three insulating M1, M2 and T phases. We identify this mode with the breather (singlet spin excitation) mode about a spin-Pierls dimerized one dimensional spin ½ Heisenberg chain. The measured frequencies of these collective modes are phenomenologically consistent with the superexchange coupling strength between V spin ½ moments in all three phases. The significant deviation of Stokes to anti-Stokes intensity ratio of this low-frequency Raman mode from the usual thermal factor exp(hʋ/KBT) for phonons, and the orthogonal dependency of the phonon and spinon vibration in the polarized Raman study confirm its origin as spin excitations. The shift in the frequency of spin-wave and simultaneous increase in the transition temperature in the absence of any structural change confirms that SPT does not prompt MIT in VO2. On the other hand, the presence of spin-wave confirms the perturbation due to spin-Peierls dimerization leading to SPT. Thus, the observation of spin-excitations resulting from 1-D Heisenberg spin-½ chain can finally resolve the years-long debate in VO2 and can be extended to oxide-based multiferroics, which are useful for various potential device applications.

Theoretical modeling of a localized surface plasmon resonance based intensity modulated fiber optic refractive index sensor.

A localized surface plasmon resonance based fiber optic sensor for refractive index sensing has been analyzed theoretically. The effects of size of the spherical metal nanoparticle as well as the light sources on the performance of the sensor have been studied rigorously. It is observed that a diffuse light source along with an intensity modulation method gives better performance in terms of sensing range. In addition, the use of a diffuse source makes the sensing device very cheap and compact, which is an important issue for the commercial applications. The refractive index range of the sensor is larger than the ranges reported for various types of fiber optic sensors utilizing intensity modulation.

Spectroscopic studies on ligand-enzyme interactions: complexation of alpha-chymotrypsin with 4',6-diamidino-2-phenylindole (DAPI).

In the present study, the interaction of two structurally related proteolytic enzymes trypsin and alpha-chymotrypsin (CHT) with 4',6-Diamidino-2-phenylindole (DAPI) has been addressed. The binding of DAPI to CHT has been characterized by steady-state and picosecond time-resolved spectroscopic techniques. Enzymatic activity of CHT and simultaneous binding of the well-known inhibitor proflavin (PF) in the presence of DAPI clearly rule out the possibility of DAPI binding at the catalytic site of the enzyme. The spectral overlap between the emission of DAPI and absorption of PF offers the opportunity to explore the binding site of DAPI using Förster resonance energy transfer (FRET). FRET studies between DAPI and PF indicate that DAPI is bound to CHT with its transition dipole nearly perpendicular to that of PF. Competitive binding of DAPI with another fluorescent probe 2,6-p-toluidinonaphthalene sulfonate (TNS), having a well-defined binding site, indicates that DAPI and TNS bind at the same hydrophobic site of the enzyme CHT. The difference in the interactions of two well-studied, structurally similar enzymes with the same molecule may find its application in the design of specific substrate mimics or inhibitors of the enzymes.

DNA origami nanorobot fiber optic genosensor to TMV.

In the quest of greater sensitivity and specificity of diagnostic systems, one continually searches for alternative DNA hybridization methods, enabling greater versatility and where possible field-enabled detection of target analytes. We present, herein, a hybrid molecular self-assembled scaffolded DNA origami entity, intimately immobilized via capture probes linked to aminopropyltriethoxysilane, onto a glass optical fiber end-face transducer, thus producing a novel biosensor. Immobilized DNA nanorobots with a switchable flap can then be actuated by a specific target DNA present in a sample, by exposing a hemin/G-quadruplex DNAzyme, which then catalyzes the generation of chemiluminescence, once the specific fiber probes are immersed in a luminol-based solution. Integrating organic nanorobots to inorganic fiber optics creates a hybrid system that we demonstrate as a proof-of-principle can be utilized in specific DNA sequence detection. This system has potential applications in a wide range of fields, including point-of-care diagnostics or cellular in vivo biosensing when using ultrathin fiber optic probes for research purposes.