Cost-effectively detecting benzene, a human carcinogen, at occupationally and atmospherically rel... more Cost-effectively detecting benzene, a human carcinogen, at occupationally and atmospherically relevant concentrations would benefit individuals at risk of exposure. This paper presents the development of a titania (TiO2) nanotube-based sensor array that has a high surface area, is highly sensitive, and operates at room temperature using simple, portable instrumentation. An n-type TiO2 nanotube was synthesized through electrochemical anodization in an electrolytic solution of ammonium fluoride-ethylene glycol and oxygen annealed at 500 °C for up to 8 hours. The nanotube sensor had a bandgap (Eg) of ~2.6 eV, and it was operated at a bias voltage of +1.5 V. The response of the sensor to benzene vapor was measured using an amperometric technique at room temperature, and when exposed to benzene, the sensor exhibited a decrease in current, as expected for an n-type metal oxide semiconductor. The sensor response was proportional to benzene concentration over a range of 100–400 ppb. A sensing mechanism based on Fermi level changes caused by band bending has been explained for this benzene sensor.
Highly ordered anodically formed titanium oxide nanotubes possess high surface area, biocompatibi... more Highly ordered anodically formed titanium oxide nanotubes possess high surface area, biocompatibility and chemical inertness. These properties make them potentially useful for many applications, but these nanotubes are insulative and possess a high band gap limiting their usefulness. Hence, these NTs cannot be directly used for electrocatalysis. Synthesis of titanium oxide nanotubes with good electrocatalytic properties has been a challenge. This study reports on the synthesis of anodically formed NTs with desirable electrocatalytic properties through annealing treatment in 2% hydrogen with a nitrogen balance (H2N2). The changes in the flat band potential, donor density, double layer capacitance and diameter of double layer was investigated using the Mott Schottky plots. The results from the electrochemical testing, scanning electron microscopy (SEM), UV-visible spectroscopy (UV-Vis) for oxygen (O2) annealed NTs and H2N2 annealed NTs were compared to establish a relationship between...
The presence of Magnéli phases in titanium oxide nanotubes (NTs) can open up frontiers in many ap... more The presence of Magnéli phases in titanium oxide nanotubes (NTs) can open up frontiers in many applications owing to their electrical and optical properties. Synthesis of NTs with Magnéli phases have posed a challenge due to the degradation and loss of morphology in NTs upon high-temperature treatments (>600 °C) in a reducing environment. This study reports on the synthesis of anodically formed NTs containing Magnéli phases through a double annealing route: oxygen (O2) annealing followed by annealing in 2% hydrogen with a nitrogen balance (2%H2-N2). The nucleation, growth, and transformation of anodized amorphous NTs into crystalline phases was investigated. The NTs obtained through this route were highly ordered and composed of mixed phases of anatase, rutile, and the Magnéli phase (Ti4O7). Experimental results from scanning electron microscopy (SEM), X-ray diffraction (XRD), scanning transmission electron microscopy (S/TEM), and Raman spectroscopy were combined with first princ...
This study identifies the dependence of electrochemical properties of titanium dioxide nanotubes ... more This study identifies the dependence of electrochemical properties of titanium dioxide nanotubes (NTs) containing specific concentrations and locations of defects within the crystal structure. NTs, formed through electrochemical anodization, were annealed at 500 C in either oxygen (O 2-NTs) or 2% hydrogen with nitrogen balance (2%H 2 /N 2-NTs). Examination of the NTs using scanning/transmission electron microscopy showed that the O 2-NTs were comprised of a mixed phase anatase-rutile, while the 2%H 2 /N 2-NTs were primarily anatase with a defect laden disordered surface layer. Electrochemical impedance measurements showed enhanced electrochemical behavior of the 2%H 2 /N 2-NTs compared to the O 2-NTs as a result of the defect-laden structure.
The availability of clean drinking water is a significant problem worldwide. Many technologies ex... more The availability of clean drinking water is a significant problem worldwide. Many technologies exist for purifying drinking water, however, many of these methods require chemicals or use simple methods, such as boiling and filtering, which may or may not be effective in removing waterborne pathogens. Present methods for detecting pathogens in point-of-use (POU) sterilized water are typically time prohibitive or have limited ability differentiating between active and inactive cells. This work describes a rapid electrochemical sensor to differentially detect the presence of active Escherichia coli (E. coli) O157:H7 in samples that have been partially or completely sterilized using a new POU electrocatalytic water purification technology based on superradicals generated by defect laden titania (TiO 2) nanotubes. The sensor was also used to detect pathogens sterilized by UV-C radiation for a comparison of different modes of cell death. The sensor utilizes immunomagnetic bead separation to isolate active bacteria by forming a sandwich assay comprised of antibody functionalized secondary magnetic beads, E. coli O157:H7, and polyguanine (polyG) oligonucleotide functionalized secondary polystyrene beads as an electrochemical tag. The assay is formed by the attachment of antibodies to active receptors on the membrane of E. coli, allowing the sensor to differentially detect viable cells. Ultravioloet (UV)-C radiation and an electrocatalytic reactor (ER) with integrated defect-laden titania nanotubes were used to examine the sensors' performance in detecting sterilized cells under different modes of cell death. Plate counts and flow cytometry were used to quantify disinfection efficacy and cell damage. It was found that the ER treatments shredded the bacteria into multiple fragments, while UV-C treatments inactivated the bacteria but left the cell membrane mostly intact.
Industrial & Engineering Chemistry Research, 2017
In this study, adsorption properties of cationized cellulose nanofibers (c-CNF) were examined for... more In this study, adsorption properties of cationized cellulose nanofibers (c-CNF) were examined for the removal of sulfate (SO 4 2-) ions from aqueous solutions under diverse experimental conditions. Nanofiber mats were fabricated through electrospinning and cationized with 3chloro-2-hydroxypropyl tri-methyl ammonium chloride (CHTAC). The resultant c-CNF with 0.134 mmol/g ammonium content showed the maximum adsorption capacity of 24.5 mg of SO 4 2per gram of sorbent using a Langmuir isotherm model. A pseudo-second order (PSO) kinetic model was fitted to the adsorption rate data, showing a faster adsorption rate of 0.0022 mg•g-1 min-1. The SEM (scanning electron microscope) micrographs revealed the average fiber diameter 280±10 nm with BET surface area of 5.04 m 2 /g analyzed through BET surface area and porosity analyzer. Fourier transform infrared (FTIR) spectroscopy confirmed the conversion of cellulose acetate (CA) to cellulose, and its subsequent cationization. Furthermore, the consequences of cationization were evaluated by Zeta potential and Thermogravimetric analysis (TGA).
Environmental science and pollution research international, Jan 21, 2017
Lead is known for its toxic and non-biodegradable behavior. The consumption of lead-contaminated ... more Lead is known for its toxic and non-biodegradable behavior. The consumption of lead-contaminated water is one of the major threat the world is facing nowadays. In this study, polyacrylonitrile (PAN) and magnetite (Fe3O4) composite nanofiber adsorbent was developed for Pb(2+) removal in batch mode. The synthesis was done by a simple and scalable process of electrospinning followed by chemical precipitation of Fe3O4. The nanofibers thus obtained were characterized through FTIR, zeta potential analyzer, and scanning electron microscope (SEM) and were analyzed for their adsorption capability for Pb(2+) ions. The amount of metal ion adsorbed was influenced by the initial metal ion concentration, the time the adsorbent was in contact, the amount of nanofiber, and the pH of the solution. The experimental data fitted well with pseudo 2nd-order and Langmuir adsorption isotherm model. The nanofibers showed high adsorption capability and could be recommended for Pb(2+) removal successfully.
Nongovernmental organizations are one group of players who are active in the efforts of internati... more Nongovernmental organizations are one group of players who are active in the efforts of international development and increasing the welfare of poor people in poor countries. Nongovernmental organizations are largely staffed by altruistic employees and volunteers working towards ideological, rather than financial, ends. Their founders are often intense, creative individuals who sometimes come up with a new product to deliver or a better way to deliver existing goods and services. They are funded by donors, many of them poor or anonymous. Yet these attributes should not be unfamiliar to economists. Development NGOs, like domestic nonprofits, can be understood in the framework of not-for-profit contracting. It is easy to conjure up a glowing vision of how the efforts of NGOs could focus on problem solving without getting bogged down in corruption or bureaucracy. But the strengths of the NGO model have some corresponding weaknesses—in agenda setting, decision making, and resource alloc...
Background: Internet video sharing sites allow the free dissemination of educational material. Th... more Background: Internet video sharing sites allow the free dissemination of educational material. This study investigated the quality and educational content of videos of eye movement disorders posted on such sites. Methods: Educational neurological eye movement videos were identified by entering the titles of the eye movement abnormality into the search boxes of the video sharing sites. Also, suggested links were followed from each video. The number of views, likes, and dislikes for each video were recorded. The videos were then rated for their picture and sound quality. Their educational value was assessed according to whether the video included a description of the eye movement abnormality, the anatomical location of the lesion (if appropriate), and the underlying diagnosis. Results: Three hundred fifty-four of these videos were found on YouTube and Vimeo. There was a mean of 6,443 views per video (range, 1-195,957). One hundred nineteen (33.6%) had no form of commentary about the eye movement disorder shown apart from the title. Forty-seven (13.3%) contained errors in the title or in the text. Eighty (22.6%) had excellent educational value by describing the eye movement abnormality, the anatomical location of the lesion, and the underlying diagnosis. Of these, 30 also had good picture and sound quality. The videos with excellent educational value had a mean of 9.84 "likes" per video compared with 2.37 for those videos without a commentary (P , 0.001). The videos that combined excellent educational value with good picture and sound quality had a mean of 10.23 "likes" per video (P = 0.004 vs videos with no commentary). There was no significant difference in the mean number of "dislikes" between those videos that had no commentary or which contained errors and those with excellent educational value. Conclusions: There are a large number of eye movement videos freely available on these sites; however, due to the lack of peer review, a significant number have poor educational value due to having no commentary or containing errors. The number of "likes" can help to identify videos with excellent educational value but the number of "dislikes" does not help in discerning which videos have poor educational value.
Sir, we read with interest the publication by Scawn et al. on a novel use of 3D printing in orbit... more Sir, we read with interest the publication by Scawn et al. on a novel use of 3D printing in orbital surgery. The authors correctly highlight the unique difficulties pertaining to orbital surgical training and using 3D models to overcome these issues. We seek to provide additional information, related to the model presented in the article. First, the commonest indication for decompressive surgery is Graves’ orbitopathy, which is due to an increase in the muscle and fat around the eye, rather than changes in the bony anatomy of the orbit. The addition of a model eye and surrounding soft tissue structures may be achieved through the use of bio-texturemodelling (a form of 3D printing). This would provide a more realistic experience to trainees and has been successfully used in other surgical fields. Second, the inclusion of electrical components should be considered, which can be used to alert trainees (via an acoustic signal) if important structures are damaged. When practising orbital decompression, this will allow a trainee to yield accurate decompressive effect, whilst preventing excessive bone removal. It will also serve to highlight the risks of nerve damage, dural tears, leakage of cerebral spinal fluid and injury to tear ducts. We appreciate the paucity of utilization of 3D printing in this field, but firmly believe that further uptake of this technology has the capacity to improve practice, and welcome further investigation.
European Journal of Orthopaedic Surgery & Traumatology, 2003
Transient osteoporosis of the hip is an uncommon condition that affects young and middleaged men,... more Transient osteoporosis of the hip is an uncommon condition that affects young and middleaged men, and women during the third trimester of pregnancy. Its incidence and aetiology in pregnancy is unknown. It is bilateral in approximately one third of patients. The patient characteristically gives a history of gradual onset of groin pain increasing in severity over a number of weeks, with pain worse on weight bearing. There is no history of trauma or systemic upset. Differential diagnoses are avascular necrosis of the hip, neoplasm, osteomyelitis and synovitis. Clinical diagnosis can be elusive, and symptoms are often misinterpreted leading to unnecessary tests and morbidity. Diagnosis is by radiological investigation. Treatment is conservative, including protected weight bearing, physical therapy and non-steroidal analgesics. We present a highly unusual case of sequential bilateral transient osteoporosis of the hip in a non-pregnant woman. Initial presentation mimicked septic arthritis leading to arthrotomy.
Cost-effectively detecting benzene, a human carcinogen, at occupationally and atmospherically rel... more Cost-effectively detecting benzene, a human carcinogen, at occupationally and atmospherically relevant concentrations would benefit individuals at risk of exposure. This paper presents the development of a titania (TiO2) nanotube-based sensor array that has a high surface area, is highly sensitive, and operates at room temperature using simple, portable instrumentation. An n-type TiO2 nanotube was synthesized through electrochemical anodization in an electrolytic solution of ammonium fluoride-ethylene glycol and oxygen annealed at 500 °C for up to 8 hours. The nanotube sensor had a bandgap (Eg) of ~2.6 eV, and it was operated at a bias voltage of +1.5 V. The response of the sensor to benzene vapor was measured using an amperometric technique at room temperature, and when exposed to benzene, the sensor exhibited a decrease in current, as expected for an n-type metal oxide semiconductor. The sensor response was proportional to benzene concentration over a range of 100–400 ppb. A sensing mechanism based on Fermi level changes caused by band bending has been explained for this benzene sensor.
Highly ordered anodically formed titanium oxide nanotubes possess high surface area, biocompatibi... more Highly ordered anodically formed titanium oxide nanotubes possess high surface area, biocompatibility and chemical inertness. These properties make them potentially useful for many applications, but these nanotubes are insulative and possess a high band gap limiting their usefulness. Hence, these NTs cannot be directly used for electrocatalysis. Synthesis of titanium oxide nanotubes with good electrocatalytic properties has been a challenge. This study reports on the synthesis of anodically formed NTs with desirable electrocatalytic properties through annealing treatment in 2% hydrogen with a nitrogen balance (H2N2). The changes in the flat band potential, donor density, double layer capacitance and diameter of double layer was investigated using the Mott Schottky plots. The results from the electrochemical testing, scanning electron microscopy (SEM), UV-visible spectroscopy (UV-Vis) for oxygen (O2) annealed NTs and H2N2 annealed NTs were compared to establish a relationship between...
The presence of Magnéli phases in titanium oxide nanotubes (NTs) can open up frontiers in many ap... more The presence of Magnéli phases in titanium oxide nanotubes (NTs) can open up frontiers in many applications owing to their electrical and optical properties. Synthesis of NTs with Magnéli phases have posed a challenge due to the degradation and loss of morphology in NTs upon high-temperature treatments (>600 °C) in a reducing environment. This study reports on the synthesis of anodically formed NTs containing Magnéli phases through a double annealing route: oxygen (O2) annealing followed by annealing in 2% hydrogen with a nitrogen balance (2%H2-N2). The nucleation, growth, and transformation of anodized amorphous NTs into crystalline phases was investigated. The NTs obtained through this route were highly ordered and composed of mixed phases of anatase, rutile, and the Magnéli phase (Ti4O7). Experimental results from scanning electron microscopy (SEM), X-ray diffraction (XRD), scanning transmission electron microscopy (S/TEM), and Raman spectroscopy were combined with first princ...
This study identifies the dependence of electrochemical properties of titanium dioxide nanotubes ... more This study identifies the dependence of electrochemical properties of titanium dioxide nanotubes (NTs) containing specific concentrations and locations of defects within the crystal structure. NTs, formed through electrochemical anodization, were annealed at 500 C in either oxygen (O 2-NTs) or 2% hydrogen with nitrogen balance (2%H 2 /N 2-NTs). Examination of the NTs using scanning/transmission electron microscopy showed that the O 2-NTs were comprised of a mixed phase anatase-rutile, while the 2%H 2 /N 2-NTs were primarily anatase with a defect laden disordered surface layer. Electrochemical impedance measurements showed enhanced electrochemical behavior of the 2%H 2 /N 2-NTs compared to the O 2-NTs as a result of the defect-laden structure.
The availability of clean drinking water is a significant problem worldwide. Many technologies ex... more The availability of clean drinking water is a significant problem worldwide. Many technologies exist for purifying drinking water, however, many of these methods require chemicals or use simple methods, such as boiling and filtering, which may or may not be effective in removing waterborne pathogens. Present methods for detecting pathogens in point-of-use (POU) sterilized water are typically time prohibitive or have limited ability differentiating between active and inactive cells. This work describes a rapid electrochemical sensor to differentially detect the presence of active Escherichia coli (E. coli) O157:H7 in samples that have been partially or completely sterilized using a new POU electrocatalytic water purification technology based on superradicals generated by defect laden titania (TiO 2) nanotubes. The sensor was also used to detect pathogens sterilized by UV-C radiation for a comparison of different modes of cell death. The sensor utilizes immunomagnetic bead separation to isolate active bacteria by forming a sandwich assay comprised of antibody functionalized secondary magnetic beads, E. coli O157:H7, and polyguanine (polyG) oligonucleotide functionalized secondary polystyrene beads as an electrochemical tag. The assay is formed by the attachment of antibodies to active receptors on the membrane of E. coli, allowing the sensor to differentially detect viable cells. Ultravioloet (UV)-C radiation and an electrocatalytic reactor (ER) with integrated defect-laden titania nanotubes were used to examine the sensors' performance in detecting sterilized cells under different modes of cell death. Plate counts and flow cytometry were used to quantify disinfection efficacy and cell damage. It was found that the ER treatments shredded the bacteria into multiple fragments, while UV-C treatments inactivated the bacteria but left the cell membrane mostly intact.
Industrial & Engineering Chemistry Research, 2017
In this study, adsorption properties of cationized cellulose nanofibers (c-CNF) were examined for... more In this study, adsorption properties of cationized cellulose nanofibers (c-CNF) were examined for the removal of sulfate (SO 4 2-) ions from aqueous solutions under diverse experimental conditions. Nanofiber mats were fabricated through electrospinning and cationized with 3chloro-2-hydroxypropyl tri-methyl ammonium chloride (CHTAC). The resultant c-CNF with 0.134 mmol/g ammonium content showed the maximum adsorption capacity of 24.5 mg of SO 4 2per gram of sorbent using a Langmuir isotherm model. A pseudo-second order (PSO) kinetic model was fitted to the adsorption rate data, showing a faster adsorption rate of 0.0022 mg•g-1 min-1. The SEM (scanning electron microscope) micrographs revealed the average fiber diameter 280±10 nm with BET surface area of 5.04 m 2 /g analyzed through BET surface area and porosity analyzer. Fourier transform infrared (FTIR) spectroscopy confirmed the conversion of cellulose acetate (CA) to cellulose, and its subsequent cationization. Furthermore, the consequences of cationization were evaluated by Zeta potential and Thermogravimetric analysis (TGA).
Environmental science and pollution research international, Jan 21, 2017
Lead is known for its toxic and non-biodegradable behavior. The consumption of lead-contaminated ... more Lead is known for its toxic and non-biodegradable behavior. The consumption of lead-contaminated water is one of the major threat the world is facing nowadays. In this study, polyacrylonitrile (PAN) and magnetite (Fe3O4) composite nanofiber adsorbent was developed for Pb(2+) removal in batch mode. The synthesis was done by a simple and scalable process of electrospinning followed by chemical precipitation of Fe3O4. The nanofibers thus obtained were characterized through FTIR, zeta potential analyzer, and scanning electron microscope (SEM) and were analyzed for their adsorption capability for Pb(2+) ions. The amount of metal ion adsorbed was influenced by the initial metal ion concentration, the time the adsorbent was in contact, the amount of nanofiber, and the pH of the solution. The experimental data fitted well with pseudo 2nd-order and Langmuir adsorption isotherm model. The nanofibers showed high adsorption capability and could be recommended for Pb(2+) removal successfully.
Nongovernmental organizations are one group of players who are active in the efforts of internati... more Nongovernmental organizations are one group of players who are active in the efforts of international development and increasing the welfare of poor people in poor countries. Nongovernmental organizations are largely staffed by altruistic employees and volunteers working towards ideological, rather than financial, ends. Their founders are often intense, creative individuals who sometimes come up with a new product to deliver or a better way to deliver existing goods and services. They are funded by donors, many of them poor or anonymous. Yet these attributes should not be unfamiliar to economists. Development NGOs, like domestic nonprofits, can be understood in the framework of not-for-profit contracting. It is easy to conjure up a glowing vision of how the efforts of NGOs could focus on problem solving without getting bogged down in corruption or bureaucracy. But the strengths of the NGO model have some corresponding weaknesses—in agenda setting, decision making, and resource alloc...
Background: Internet video sharing sites allow the free dissemination of educational material. Th... more Background: Internet video sharing sites allow the free dissemination of educational material. This study investigated the quality and educational content of videos of eye movement disorders posted on such sites. Methods: Educational neurological eye movement videos were identified by entering the titles of the eye movement abnormality into the search boxes of the video sharing sites. Also, suggested links were followed from each video. The number of views, likes, and dislikes for each video were recorded. The videos were then rated for their picture and sound quality. Their educational value was assessed according to whether the video included a description of the eye movement abnormality, the anatomical location of the lesion (if appropriate), and the underlying diagnosis. Results: Three hundred fifty-four of these videos were found on YouTube and Vimeo. There was a mean of 6,443 views per video (range, 1-195,957). One hundred nineteen (33.6%) had no form of commentary about the eye movement disorder shown apart from the title. Forty-seven (13.3%) contained errors in the title or in the text. Eighty (22.6%) had excellent educational value by describing the eye movement abnormality, the anatomical location of the lesion, and the underlying diagnosis. Of these, 30 also had good picture and sound quality. The videos with excellent educational value had a mean of 9.84 "likes" per video compared with 2.37 for those videos without a commentary (P , 0.001). The videos that combined excellent educational value with good picture and sound quality had a mean of 10.23 "likes" per video (P = 0.004 vs videos with no commentary). There was no significant difference in the mean number of "dislikes" between those videos that had no commentary or which contained errors and those with excellent educational value. Conclusions: There are a large number of eye movement videos freely available on these sites; however, due to the lack of peer review, a significant number have poor educational value due to having no commentary or containing errors. The number of "likes" can help to identify videos with excellent educational value but the number of "dislikes" does not help in discerning which videos have poor educational value.
Sir, we read with interest the publication by Scawn et al. on a novel use of 3D printing in orbit... more Sir, we read with interest the publication by Scawn et al. on a novel use of 3D printing in orbital surgery. The authors correctly highlight the unique difficulties pertaining to orbital surgical training and using 3D models to overcome these issues. We seek to provide additional information, related to the model presented in the article. First, the commonest indication for decompressive surgery is Graves’ orbitopathy, which is due to an increase in the muscle and fat around the eye, rather than changes in the bony anatomy of the orbit. The addition of a model eye and surrounding soft tissue structures may be achieved through the use of bio-texturemodelling (a form of 3D printing). This would provide a more realistic experience to trainees and has been successfully used in other surgical fields. Second, the inclusion of electrical components should be considered, which can be used to alert trainees (via an acoustic signal) if important structures are damaged. When practising orbital decompression, this will allow a trainee to yield accurate decompressive effect, whilst preventing excessive bone removal. It will also serve to highlight the risks of nerve damage, dural tears, leakage of cerebral spinal fluid and injury to tear ducts. We appreciate the paucity of utilization of 3D printing in this field, but firmly believe that further uptake of this technology has the capacity to improve practice, and welcome further investigation.
European Journal of Orthopaedic Surgery & Traumatology, 2003
Transient osteoporosis of the hip is an uncommon condition that affects young and middleaged men,... more Transient osteoporosis of the hip is an uncommon condition that affects young and middleaged men, and women during the third trimester of pregnancy. Its incidence and aetiology in pregnancy is unknown. It is bilateral in approximately one third of patients. The patient characteristically gives a history of gradual onset of groin pain increasing in severity over a number of weeks, with pain worse on weight bearing. There is no history of trauma or systemic upset. Differential diagnoses are avascular necrosis of the hip, neoplasm, osteomyelitis and synovitis. Clinical diagnosis can be elusive, and symptoms are often misinterpreted leading to unnecessary tests and morbidity. Diagnosis is by radiological investigation. Treatment is conservative, including protected weight bearing, physical therapy and non-steroidal analgesics. We present a highly unusual case of sequential bilateral transient osteoporosis of the hip in a non-pregnant woman. Initial presentation mimicked septic arthritis leading to arthrotomy.
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Papers by Hammad Malik