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•Two-Photon lithography can fabricate true 3D microstructures with high spatial resolution.•Feature sizes beyond the diffraction limit can be attained via TPL.•TPL is applicable to ...wide range of materials.•Functionalizing polymers expands the application areas of TPL.•Scalability and high throughput with superior resolution can be achieved in TPL.•TPL is well-suited for the fabrication of three-dimensional metamaterials.
With the advent of femtosecond lasers in the early 1990s, ultrafast laser processing has proven to be an imperative tool for micro/nano machining. Two-photon lithography (TPL) is one such unique microfabrication technique exploiting the nonlinear dependency of the polymerization rate on the irradiating light intensity to produce true three-dimensional structures with feature sizes beyond the diffraction limit. This characteristic has revolutionized laser material processing for the fabrication of micro and nanostructures. In this paper, an overview of TPL including its working principle, experimental setup, and materials is presented. Then, the effect of resolution with a focus on techniques adopted to improve the final resolution of the structures is covered. Insights to improve throughput and speed of fabrication to pave a way for industrialization of this technique are provided. Finally, TPL for microfabrication of structures with the emphasis on metamaterials is thoroughly reviewed and presented.
Mechanical metamaterials are generally two-dimensional periodic structures or three-dimensional cellular structures that exhibit mechanical properties beyond the ordinary. Due to size and boundary ...effects, three-dimensional mechanical metamaterials typically display anisotropic changes even if they are isotropic in construction and composition. However, in this study, the comprehensive design and fabrication of a three-dimensional axisymmetric auxetic structure that exhibits uniform and axisymmetric transverse deformation under longitudinal compression loading are proposed. Extending the concept of two-dimensional periodically perforated auxetic sheet structures to the third dimension, the design of the metamaterial was generated by revolving a two-dimensional parabolic curve along the axis of rotation and subsequently perforating the structure periodically with elliptical voids varying in size longitudinally along the curvature of the structure in order to promote the exhibition of isotropic negative Poisson's ratio. Furthermore, this study elucidates the significance of the perforations by comparing the metamaterial structure to a so-called plain structure.
Hypoparathyroidism occurs due to insufficient production of parathyroid hormone to maintain extracellular calcium levels within the normal range. The acute clinical symptoms and signs of ...hypoparathyroidism are those of hypocalcaemia, ranging from tingling and numbness of limb extremities to intractable seizures. Often seizures are mistaken for epilepsy. Though hypoparathyroidism is not uncommon, the diagnosis is often missed due to its unusual clinical manifestation. This is the first documented report with vitamin D, Parathormone levels and urinary biochemical parameters from India. We present two cases of hypoparathyroidism who presented with seizures along with a short review of literature.
Hypoparathyroidism occurs due to insufficient production of parathyroid hormone to maintain extracellular calcium levels within the normal range. The acute clinical symptoms and signs of ...hypoparathyroidism are those of hypocalcaemia, ranging from tingling and numbness of limb extremities to intractable seizures. Often seizures are mistaken for epilepsy. Though hypoparathyroidism is not uncommon, the diagnosis is often missed due to its unusual clinical manifestation. This is the first documented report with vitamin D, Parathormone levels and urinary biochemical parameters from India. We present two cases of hypoparathyroidism who presented with seizures along with a short review of literature.
Six children with untreated congenital adrenal hyperplasia (CAH) were examined by computed tomography (CT). Three cases demonstrated diffuse enlargement of both adrenal glands with preservation of ...normal configuration and two showed tumorous transformation in one of the enlarged glands. One had equivocal enlargement of the adrenal gland. Even the youngest in this group (age 2 years) also showed bilateral hyperplasia.
•MT resistivity structure across the hitherto least studied eastern segment of Proterozoic CITZ.•North dipping crustal conductive horizon beneath Tan Shear suggests suture signature.•NSL shows ...conductive mid-lower crust due to magma plumbing during the Deccan volcanism.•Resistivity section indicates polyphase tectonics, from Proterozoic to Tertiary, in the mega lineament zone.
The Central Indian Tectonic Zone (CITZ), a major tectonic feature extending across the Indian sub-continent, was formed by the accretion of the cratonic domains in the north and south blocks of peninsular India during the Proterozoic. It is characterized with prominent shear/fault zones and granulite belts that carry the evolutionary history of the central Indian region. This study presents the two-dimensional resistivity structure of the hitherto least studied eastern segment of the mega lineament in the Indian subcontinent. Magnetotelluric (MT) data along the Rajnandgaon-Bareli profile, which extends from the southern margin (Central Indian Shear-CIS) to the northern limit (Narmada-Son Lineament-NSL) of the CITZ, were used to investigate the resistivity character of the crust and shallow upper mantle. The study imaged conductive to moderately conductive structures, which show correlation to the various shear/faults and granulitic belts mapped in the region, interspersed in a resistive background. An upper crustal isolated conductor was observed below the Bhandra – Balaghat Granulite belt, which is exposed along the CIS. A vertical moderately conductive structure noticed in the middle to upper mantle depths under the Ramakona-Katangi Granulite (RKG) belt and this is interpreted as fault/shear zone that acted as the channel/pathway for the emplacement of parental magma of the RKG rocks. A more interesting feature in the MT model is a north dipping conductive horizon extending from the upper crust to the Moho. This feature shows further extension into the upper mantle as a subvertical moderately conductive zone and can be traced onto the surface mark of the Tan Shear, which suggests suture status to this prominent shear zone within the CITZ. Resistivity section also shows mid-lower crustal conductive/moderately conductive horizons under the Deccan trap and NSL, which are produced due to the large-scale magma intrusions into the crust during the Cretaceous-Tertiary Deccan volcanism through the pre-existing weak zones in the CITZ. The conductive to moderately conductive features of the MT model are indicative of the complex tectonic history of the region that range from accretion processes started in the Paleoproterozoic, followed by multiple metamorphic and deformation cycles in different geological times, to the Late Cretaceous volcanism.
Two parallel magnetotelluric (MT) traverses across the Achankovil shear zone (AKSZ) in southern India using a wide band (1
kHz–1
ks) data acquisition system, reveal the regional geo-electric average ...strike direction of N 40°W, consistent with the geological strike direction of the AKSZ. The derived model shows distinct high electrical resistivity (>
1000
Ω
m) for the upper crust below the Madurai Granulite Block (MGB) with a gentle dip towards south and a northerly dip below the Kerala Khondalite Block (KKB). The lower crust is resistive below both MGB and KKB while it is moderately conductive (<
500
Ω
m) below AKSZ. Our study shows that the AKSZ is a tectonic divide between the MGB to the north and KKB to the south. The results together with an integration of seismic, gravity and heat flow data suggest a high dense and moderately conductive mantle material brought up to the mid–lower crust, and a thermally eroded crust with a flower structure at depth, in conformity with the model of AKSZ as the trace of a collisional suture.
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► MT model reveals the thermal evolution of the crust across the Achankovil shear zone. ► Moderately conductive deep crust beneath the AKSZ, associated with high velocity, high density and high heat flow. ► A dome like feature beneath the Madurai Granulite Block. ► The study reveals a crustal flower structure and confirms the model of AKSZ as a collisional suture.
We report the generation of functional dopaminergic neurons from human embryonic stem cells (hESCs) using a growth factor mediated multistep EB protocol and its therapeutic effects in vivo. Embryoid ...bodies (EBs) were cultured in insulin–transferrin–selenium fibronectin (ITSFn) media for the selection of neural precursor cells (NPC). The selected cells on exposure to N2 media supplemented with EGF, bFGF initially aggregated to generate spontaneous free floating neurospheres and on exposure to signaling molecules Shh and FGF-8 differentiated into dopaminergic neurons (40% TH+ cells/total neurons). The differentiated NPC expressed dopaminergic specific markers both at cellular and molecular levels. They secreted detectable levels of dopamine into the culture supernatant. The most unique feature of our protocol is the generation of free floating neurospheres which can be expanded for a longer period without losing their capability to differentiate into DA neurons. Further, transplantation of NPCs into the substantia nigra of 6-OHDA lesioned rat model of Parkinson’s disease elicited significant reversal of lesion induced motor deficits which was sustained upto the end of 1 year long study period. Immunohistochemical studies of the grafted area one year post transplantation revealed that transplanted hESC derived neural precursor cells survived, integrated in vivo and differentiated into dopaminergic neurons without teratoma formation.
In summary, our results encourage the potential use of hESC derived dopaminergic neurons for future clinical application in Parkinson’s disease.
The Narmada–Son Lineament (NSL) Zone is the second most important tectonic feature after Himalayas, in the Indian geology. Magnetotelluric (MT) studies were carried out in the NSL zone along a 130
km ...long NNE-SSW trending profile. The area of investigation extends from Edlabad (20°46′16″; 75°59′05″) in the South to Khandwa (21°53′51″; 76°18′05″) in the North. The data shows in general the validity of a two-dimensional (2D) approach. Besides providing details on the shallow crustal section, the 2D modeling results resolved four high conductive zones extending from the middle to deep crust, spatially coinciding with the major structural features in the area namely the Gavligarh, Tapti, Barwani-Sukta and Narmada South faults. The model for the shallow section has brought out a moderately resistive layer (30–150
Ω
m) representing the exposed Deccan trap layer, overlying a conductive layer (10–30
Ω
m) inferred to be the subtrappean Gondwana sediments, the latter resting on a high resistive basement/upper crust. The Deccan trap thickness varies from around a few hundred meters to as much as 1.5
km along the traverse. A subtrappean sedimentary basin like feature is delineated in the northern half of the traverse where a sudden thickening of subtrappean sediments amounting to as much as 2
km is noticed. The high resistive upper crust is relatively thick towards the southern end and tends to become thinner towards the middle and northern part of the traverse. The lower crustal segment is conductive over a major part of the profile. Considering the generally enhanced heat flow values in the NSL region, coupled with characteristic gravity highs and enhanced seismic velocities coinciding with the mid to lower crustal conductors delineated from MT, presence of zones of high density mafic bodies/intrusives with fluids, presumably associated with magmatic underplating of the crust in the zone of major tectonic faults in NSL region are inferred.
