One of the limitations to the widespread use of hydrogen as an energy carrier is its storage in a... more One of the limitations to the widespread use of hydrogen as an energy carrier is its storage in a safe and compact form. Herein, recent developments in effective high-capacity hydrogen storage materials are reviewed, with a special emphasis on light compounds, including those based on organic porous structures, boron, nitrogen, and aluminum. These elements and their related compounds hold the promise of high, reversible, and practical hydrogen storage capacity for mobile applications, including vehicles and portable power equipment, but also for the large scale and distributed storage of energy for stationary applications. Current understanding of the fundamental principles that govern the interaction of hydrogen with these light compounds is summarized, as well as basic strategies to meet practical targets of hydrogen uptake and release. The limitation of these strategies and current understanding is also discussed and new directions proposed.
A chance observation of return of excellent facial movement, after 18 months following the first ... more A chance observation of return of excellent facial movement, after 18 months following the first stage of cross-face nerve grafting, without free functional muscle transfer, in a case of long-standing facial palsy, lead the senior author (RBA) to further investigate clinically. This procedure, now christened as cross-face nerve extension and neurotization, was carried out in 12 patients of very long-standing facial palsy (mean 21 years) in years 1996-2011. The mean patient age and duration of palsy were 30.58 years and 21.08 years, respectively. In patients, 1-5 a single buccal or zygomatic branch served as a donor nerve, but subsequently, we used two donor nerves. The mean follow-up period was 20.75 months. Successive patients had excellent to good return of facial expression with two fair results. Besides improved smile, patients could largely retain air in the mouth without any escape and had improved mastication. No complications were encountered except synkinesis in 1 patient. No additional surgical procedures were performed. There is experimental evidence to suggest that neurotization of a completely denervated muscle can occur by the formation of new ectopic motor end plates. Long-standing denervated muscle fibres eventually atrophy severely but are capable of re-innervation and regeneration, as validated by electron microscopic studies. In spite of several suggestions in the literature to clinically validate functional recovery by direct neurotization, the concept remains anecdotal. Our results substantiate this procedure, and it has the potential to simplify reanimation in longstanding facial palsy. Our work now needs validation by other investigators in the field of restoring facial animation.
Indian journal of plastic surgery : official publication of the Association of Plastic Surgeons of India, 2014
One of the better options available to repair a large palatal defect is by employing a free flap.... more One of the better options available to repair a large palatal defect is by employing a free flap. Almost all the times such free flaps are plumbed to facial vessels. The greatest challenge in such cases is the placement of the pedicle from palatal shelf to recipient vessels because there is no direct route available. As majority of large palatal fistulae are encountered in operated cleft palates there is a possibility of routing the pedicle through a cleft in the maxillary arch or via pyriform aperture. When such a possibility doesn't exist the pedicle is routed behind the maxillary arch. We describe a novel technique of pedicle placement through a maxillary antrostomy, in this case report, where a large palatal fistula in a 16 year old boy was repaired employing a free radial artery forearm flap. The direct route provided by maxillary antrostomy is considered the most expeditious of all possibilities mentioned above.
We report an unusual robust ferromagnetic order above room temperature upon amorphization of pero... more We report an unusual robust ferromagnetic order above room temperature upon amorphization of perovskite [YCrO3] in pulsed laser deposited thin films. This is contrary to the usual expected formation of a spin glass magnetic state in the resulting disordered structure. To understand the underlying physics of this phenomenon, we combine advanced spectroscopic techniques and first-principles calculations. We find that the observed order-disorder transformation is accompanied by an insulator-metal transition arising from a wide distribution of Cr-O-Cr bond angles and the consequent metallization through free carriers. Similar results also found in YbCrO3-films suggest that the observed phenomenon is more general and should, in principle, apply to a wider range of oxide systems. The ability to tailor ferromagnetic order above room temperature in oxide materials opens up many possibilities for novel technological applications of this counter intuitive effect.
As primary repair of divided flexor tendons becomes more common, secondary tendon surgery becomes... more As primary repair of divided flexor tendons becomes more common, secondary tendon surgery becomes largely that of the complications of primary repair, namely ruptured and adherent repairs. These occur with an incidence of each in most reported series world-wide of around 5%, with these problems having changed little in the last two decades, despite strengthening our suture repairs. Where the primary referral service is less well-developed, and as a more occasional occurrence where primary treatment is the routine, the surgeon faces different problems. Patients arrive at a hand unit variable, but longer, times after the primary insult, having had no, or bad, previous treatment. Sometimes the situation is the same, viz. an extended finger with no active flexion, but now no longer amenable to primary repair. Frequently, it is much more complex as a result of injuries to the other tissues of the digit and, also, as a result of the unaided healing process within the digit in the presence...
Indian journal of plastic surgery : official publication of the Association of Plastic Surgeons of India
Composite grafts for nasal reconstruction have been around for over a century but the opinion on ... more Composite grafts for nasal reconstruction have been around for over a century but the opinion on its virtues and failings keeps vacillating with a huge difference on the safe size of the graft for transfer. Alar margin and columellar defects are more distinct than dorsal nasal defects in greater difficulty in ensuring a good aesthetic outcome. We report our series of 19 consecutive patients in whom a composite graft was used to reconstruct a defect of alar margin (8 patients), alar base (7 patients) or columella (4 patients). Patient ages ranged from 3-35 years with 5 males and 14 females. The grafts to alar margin and base ranged 0.6-1 cm in width, while grafts to columella were 0.7-1.2 cm. The maximum dimension of the graft in this series was 0.9 mm x 10 mm. Composite grafts were sculpted to be two layered (skin + cartilage), three layered wedges (skin + cartilage + skin) or their combination (two layered in a portion and three layered in another portion). All grafts were cooled i...
Mucormycosis is usually an invasive mycotic disease caused by fungi in the class mucormycetes. He... more Mucormycosis is usually an invasive mycotic disease caused by fungi in the class mucormycetes. Here we report a case of cutaneous mucormycosis due to Lichtheimia ramosa in a 20-year-old female patient with burn injuries. She was admitted to the hospital with accidental flame burns covering 60 % total burn surface area. After 15 days of admission to hospital, the burn wound showed features of fungal infection. Culture showed white cottony growth belonging to the Mucorales order. Morphological identification confirmed it as L. ramosa. She was managed surgically and medically with the help of amphotericin B. Patient survived due to prompt diagnosis and appropriate medical and surgical treatment. Early diagnosis is critical in prevention of morbidity and mortality associated with the disease. Fungal infection in burn wounds can be difficult to diagnose and manage.
Proceedings of the National Academy of Sciences of the United States of America, Jan 2, 2014
First principles-based electronic structure calculations of superhard iron tetraboride (FeB4) und... more First principles-based electronic structure calculations of superhard iron tetraboride (FeB4) under high pressure have been undertaken in this study. Starting with a "conventional" superconducting phase of this material under high pressure leads to an unexpected phase transition toward a semiconducting one. This transition occurred at 53.7 GPa, and this pressure acts as a demarcation between two distinct crystal symmetries, metallic orthorhombic and semiconducting tetragonal phases, with Pnnm and I4₁/acd space groups, respectively. In this work, the electron-phonon coupling-derived superconducting T(c) has been determined up to 60 GPa and along with optical band gap variation with increasing pressure up to 300 GPa. The dynamic stability has been confirmed by phonon dispersion calculations throughout this study.
Metallization in pure hydrogen has been proposed to give rise to high-temperature superconductivi... more Metallization in pure hydrogen has been proposed to give rise to high-temperature superconductivity at pressures which still lie beyond the reach of contemporary experimental techniques. Hydrogen-dense materials offer an opportunity to study related phenomena at experimentally achievable pressures. Here we report the prediction of high-temperature superconductivity in yttrium hydride (YH3), with a T(c) of 40 K at 17.7 GPa, the lowest reported pressure for hydrogen-dense materials to date. Specifically, we find that the face-centered cubic structure of YH3 exhibits superconductivity of different origins in two pressure regions. The evolution of T(c) with pressure follows the corresponding change of s-d hybridization between H and Y, due to an enhancement of the electron-phonon coupling by a matching of the energy level from Y-H vibrations with the peak of the s electrons from the octahedrally coordinated hydrogen atoms.
In order to reveal structural trends with increasing pressure in d transition metals, we performe... more In order to reveal structural trends with increasing pressure in d transition metals, we performed full potential linear muffin-tin orbital calculations for Fe, Ru, and Os in the hexagonal close packed structure. The calculations cover a wide volume range and ...
Hydrogen binding energies for the primary and secondary adsorption sites in the Cd- and Zn-based ... more Hydrogen binding energies for the primary and secondary adsorption sites in the Cd- and Zn-based metal organic framework-5 (MOF-5) were studied using density functional theory. Out of the three exchange-correlation functionals employed in our study, we find that the local density approximation yields a qualitatively correct description of the interaction strengths of H(2) in MOF-5 systems. The H(2) adsorption energies for all trapping sites in Zn- and Cd-based MOF-5 are seen to be of the same order of magnitude but with a generally stronger binding in Cd-based MOF-5 as compared to Zn-based MOF-5. In particular, the H(2) binding energy at the secondary adsorption sites in Cd-based MOF-5 is increased by around 25% compared to Zn-based MOF-5. This result suggests that Cd-based MOF-5 would be better suited to store hydrogen at higher temperatures than Zn-based MOF-5.
We report a case of total upper eyelid reconstruction by a new technique after excision of an eye... more We report a case of total upper eyelid reconstruction by a new technique after excision of an eyelid tumour. The eyelid was reconstructed by a horizontal, laterally based flap from just under the lower eyelid combined with a chondro-mucosal graft from the nasal septum. Surgical outcome was an excellent aesthetically reconstructed eyelid, which was mobile and properly gliding on the globe to achieve complete eye closure.
One of the limitations to the widespread use of hydrogen as an energy carrier is its storage in a... more One of the limitations to the widespread use of hydrogen as an energy carrier is its storage in a safe and compact form. Herein, recent developments in effective high-capacity hydrogen storage materials are reviewed, with a special emphasis on light compounds, including those based on organic porous structures, boron, nitrogen, and aluminum. These elements and their related compounds hold the promise of high, reversible, and practical hydrogen storage capacity for mobile applications, including vehicles and portable power equipment, but also for the large scale and distributed storage of energy for stationary applications. Current understanding of the fundamental principles that govern the interaction of hydrogen with these light compounds is summarized, as well as basic strategies to meet practical targets of hydrogen uptake and release. The limitation of these strategies and current understanding is also discussed and new directions proposed.
A chance observation of return of excellent facial movement, after 18 months following the first ... more A chance observation of return of excellent facial movement, after 18 months following the first stage of cross-face nerve grafting, without free functional muscle transfer, in a case of long-standing facial palsy, lead the senior author (RBA) to further investigate clinically. This procedure, now christened as cross-face nerve extension and neurotization, was carried out in 12 patients of very long-standing facial palsy (mean 21 years) in years 1996-2011. The mean patient age and duration of palsy were 30.58 years and 21.08 years, respectively. In patients, 1-5 a single buccal or zygomatic branch served as a donor nerve, but subsequently, we used two donor nerves. The mean follow-up period was 20.75 months. Successive patients had excellent to good return of facial expression with two fair results. Besides improved smile, patients could largely retain air in the mouth without any escape and had improved mastication. No complications were encountered except synkinesis in 1 patient. No additional surgical procedures were performed. There is experimental evidence to suggest that neurotization of a completely denervated muscle can occur by the formation of new ectopic motor end plates. Long-standing denervated muscle fibres eventually atrophy severely but are capable of re-innervation and regeneration, as validated by electron microscopic studies. In spite of several suggestions in the literature to clinically validate functional recovery by direct neurotization, the concept remains anecdotal. Our results substantiate this procedure, and it has the potential to simplify reanimation in longstanding facial palsy. Our work now needs validation by other investigators in the field of restoring facial animation.
Indian journal of plastic surgery : official publication of the Association of Plastic Surgeons of India, 2014
One of the better options available to repair a large palatal defect is by employing a free flap.... more One of the better options available to repair a large palatal defect is by employing a free flap. Almost all the times such free flaps are plumbed to facial vessels. The greatest challenge in such cases is the placement of the pedicle from palatal shelf to recipient vessels because there is no direct route available. As majority of large palatal fistulae are encountered in operated cleft palates there is a possibility of routing the pedicle through a cleft in the maxillary arch or via pyriform aperture. When such a possibility doesn't exist the pedicle is routed behind the maxillary arch. We describe a novel technique of pedicle placement through a maxillary antrostomy, in this case report, where a large palatal fistula in a 16 year old boy was repaired employing a free radial artery forearm flap. The direct route provided by maxillary antrostomy is considered the most expeditious of all possibilities mentioned above.
We report an unusual robust ferromagnetic order above room temperature upon amorphization of pero... more We report an unusual robust ferromagnetic order above room temperature upon amorphization of perovskite [YCrO3] in pulsed laser deposited thin films. This is contrary to the usual expected formation of a spin glass magnetic state in the resulting disordered structure. To understand the underlying physics of this phenomenon, we combine advanced spectroscopic techniques and first-principles calculations. We find that the observed order-disorder transformation is accompanied by an insulator-metal transition arising from a wide distribution of Cr-O-Cr bond angles and the consequent metallization through free carriers. Similar results also found in YbCrO3-films suggest that the observed phenomenon is more general and should, in principle, apply to a wider range of oxide systems. The ability to tailor ferromagnetic order above room temperature in oxide materials opens up many possibilities for novel technological applications of this counter intuitive effect.
As primary repair of divided flexor tendons becomes more common, secondary tendon surgery becomes... more As primary repair of divided flexor tendons becomes more common, secondary tendon surgery becomes largely that of the complications of primary repair, namely ruptured and adherent repairs. These occur with an incidence of each in most reported series world-wide of around 5%, with these problems having changed little in the last two decades, despite strengthening our suture repairs. Where the primary referral service is less well-developed, and as a more occasional occurrence where primary treatment is the routine, the surgeon faces different problems. Patients arrive at a hand unit variable, but longer, times after the primary insult, having had no, or bad, previous treatment. Sometimes the situation is the same, viz. an extended finger with no active flexion, but now no longer amenable to primary repair. Frequently, it is much more complex as a result of injuries to the other tissues of the digit and, also, as a result of the unaided healing process within the digit in the presence...
Indian journal of plastic surgery : official publication of the Association of Plastic Surgeons of India
Composite grafts for nasal reconstruction have been around for over a century but the opinion on ... more Composite grafts for nasal reconstruction have been around for over a century but the opinion on its virtues and failings keeps vacillating with a huge difference on the safe size of the graft for transfer. Alar margin and columellar defects are more distinct than dorsal nasal defects in greater difficulty in ensuring a good aesthetic outcome. We report our series of 19 consecutive patients in whom a composite graft was used to reconstruct a defect of alar margin (8 patients), alar base (7 patients) or columella (4 patients). Patient ages ranged from 3-35 years with 5 males and 14 females. The grafts to alar margin and base ranged 0.6-1 cm in width, while grafts to columella were 0.7-1.2 cm. The maximum dimension of the graft in this series was 0.9 mm x 10 mm. Composite grafts were sculpted to be two layered (skin + cartilage), three layered wedges (skin + cartilage + skin) or their combination (two layered in a portion and three layered in another portion). All grafts were cooled i...
Mucormycosis is usually an invasive mycotic disease caused by fungi in the class mucormycetes. He... more Mucormycosis is usually an invasive mycotic disease caused by fungi in the class mucormycetes. Here we report a case of cutaneous mucormycosis due to Lichtheimia ramosa in a 20-year-old female patient with burn injuries. She was admitted to the hospital with accidental flame burns covering 60 % total burn surface area. After 15 days of admission to hospital, the burn wound showed features of fungal infection. Culture showed white cottony growth belonging to the Mucorales order. Morphological identification confirmed it as L. ramosa. She was managed surgically and medically with the help of amphotericin B. Patient survived due to prompt diagnosis and appropriate medical and surgical treatment. Early diagnosis is critical in prevention of morbidity and mortality associated with the disease. Fungal infection in burn wounds can be difficult to diagnose and manage.
Proceedings of the National Academy of Sciences of the United States of America, Jan 2, 2014
First principles-based electronic structure calculations of superhard iron tetraboride (FeB4) und... more First principles-based electronic structure calculations of superhard iron tetraboride (FeB4) under high pressure have been undertaken in this study. Starting with a "conventional" superconducting phase of this material under high pressure leads to an unexpected phase transition toward a semiconducting one. This transition occurred at 53.7 GPa, and this pressure acts as a demarcation between two distinct crystal symmetries, metallic orthorhombic and semiconducting tetragonal phases, with Pnnm and I4₁/acd space groups, respectively. In this work, the electron-phonon coupling-derived superconducting T(c) has been determined up to 60 GPa and along with optical band gap variation with increasing pressure up to 300 GPa. The dynamic stability has been confirmed by phonon dispersion calculations throughout this study.
Metallization in pure hydrogen has been proposed to give rise to high-temperature superconductivi... more Metallization in pure hydrogen has been proposed to give rise to high-temperature superconductivity at pressures which still lie beyond the reach of contemporary experimental techniques. Hydrogen-dense materials offer an opportunity to study related phenomena at experimentally achievable pressures. Here we report the prediction of high-temperature superconductivity in yttrium hydride (YH3), with a T(c) of 40 K at 17.7 GPa, the lowest reported pressure for hydrogen-dense materials to date. Specifically, we find that the face-centered cubic structure of YH3 exhibits superconductivity of different origins in two pressure regions. The evolution of T(c) with pressure follows the corresponding change of s-d hybridization between H and Y, due to an enhancement of the electron-phonon coupling by a matching of the energy level from Y-H vibrations with the peak of the s electrons from the octahedrally coordinated hydrogen atoms.
In order to reveal structural trends with increasing pressure in d transition metals, we performe... more In order to reveal structural trends with increasing pressure in d transition metals, we performed full potential linear muffin-tin orbital calculations for Fe, Ru, and Os in the hexagonal close packed structure. The calculations cover a wide volume range and ...
Hydrogen binding energies for the primary and secondary adsorption sites in the Cd- and Zn-based ... more Hydrogen binding energies for the primary and secondary adsorption sites in the Cd- and Zn-based metal organic framework-5 (MOF-5) were studied using density functional theory. Out of the three exchange-correlation functionals employed in our study, we find that the local density approximation yields a qualitatively correct description of the interaction strengths of H(2) in MOF-5 systems. The H(2) adsorption energies for all trapping sites in Zn- and Cd-based MOF-5 are seen to be of the same order of magnitude but with a generally stronger binding in Cd-based MOF-5 as compared to Zn-based MOF-5. In particular, the H(2) binding energy at the secondary adsorption sites in Cd-based MOF-5 is increased by around 25% compared to Zn-based MOF-5. This result suggests that Cd-based MOF-5 would be better suited to store hydrogen at higher temperatures than Zn-based MOF-5.
We report a case of total upper eyelid reconstruction by a new technique after excision of an eye... more We report a case of total upper eyelid reconstruction by a new technique after excision of an eyelid tumour. The eyelid was reconstructed by a horizontal, laterally based flap from just under the lower eyelid combined with a chondro-mucosal graft from the nasal septum. Surgical outcome was an excellent aesthetically reconstructed eyelid, which was mobile and properly gliding on the globe to achieve complete eye closure.
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Papers by Rajeev Ahuja