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The construction industry uses cement, the production of which is heavy contributor to carbon dioxide (CO2) emissions and environmental damage. Any method that reduces the usage of cement could thus result in a substantial reduction of the overall carbon dioxide footprint of final cement-based products. In this study, ureolytic bacteria were used to improve the different properties of cement mortar and concrete. Properties such as compressive strength and sorptivity were studied experimentally. The experimental results showed that the compressive strength of both cement mortar and concrete increased with an increase in bacterial concentration due to microbiologically induced mineral precipitation. An optimum bacterial dosage of 107 colony-forming units (CFU)/ml was found for the maximum increase in compressive strength for both mortar and concrete. Capillary water absorption was also found to be lower for the bacterial specimens at the optimum dosage compared with that of the control specimens. Microstructural analysis, X-ray powder diffraction and field emission scanning electron microscopy confirmed the microbiologically induced mineral precipitation.

Most reported cases of enteroliths causing obstruction occur in large bowel. If in small bowel, it is usually associated with underlying pathology. This is a curious case of a large enterolith in a normal small bowel, causing obstruction without any underlying pathology at the site of impaction, makes this case a rare one.

Filariasis of the breast is a very rare condition. In India, largest number (around 600 million) of people live in endemic areas. Despite the huge number, it is quite rare to find microfilaria in routine smears and body fluids and it is even more rare to find it in breasts. A 40 years old female, presented with a history of lump in the right breast approximately 3x3 cm in size in the right lower quadrant. Findings were confirmed by clinical examination which did not reveal any palpable ipsilateral or contralateral axillary lymph nodes. FNAC showed it as a benign lesion. After local excision, histopathology revealed a filarial worm. Filariasis of the breast is a rare disease. The presence of microfilaria in breasts using FNAC has been reported at times but the presence of the filarial worms can only be confirmed on histopathology, hence a core biopsy or an excision biopsy is a must in all the cases. A presumptive diagnosis of filariasis can be made on sonography if the worms are alive and active, the typical presentation on USG is the filarial dance. Surgical excision of the lump followed by DEC therapy is the treatment of choice for filarial lump of the breast.

Malignant melanoma of the rectum is an extremely rare disease. It typically presents in the fifth or sixth decade predominantly in female sex. The first symptoms are nonspecific such as bleeding, anal mass or pain. A timely diagnosis of melanoma is made even more difficult due to lack of obvious pigmentation and histologically amelanotic. Anorectal malignant melanoma spread along submucosal planes and are often beyond complete resection at the time of diagnosis. Prognosis is very poor. We present a rare case of malignant melanoma of rectum in a 21-year-old male, who was diagnosed at advanced stage, and a case of malignant melanoma in a 50-year-old male, who underwent abdominoperineal resection with permanent colostomy. Anorectal malignant melanoma is difficult to diagnose and prognosis is poor.

Jejunal diverticulitis is a rare disease, with jejunal perforation as its rarest complications due to low intraluminal pressure. Since the current pandemic of COVID-19 it has shown to be affecting gastrointestinal system in a proportion of patients, and worsening of pre-existing GI conditions. We encountered a case of a 75 years old gentleman, suffering with severe COVID-19 pneumonia, who during the course of the disease presented with spontaneous Jejunal perforation, secondary to jejunal diverticulosis. Jejunal diverticula are the least common type of small bowel diverticula & perforation as their complication is the rarest of all complications. Their presentation is variable from asymptomatic to chronic abdominal symptoms and the complications such as perforation as described in our case. Their relative clinical rarity and varied presentation may make diagnosis both delayed and difficult.

Ureolytic-type bacteria has been used to improve the strength of cement mortar by the precipitation of calcium carbonate. In the present study Bacillus sphaericus has been used to improve the properties of cement mortar such as setting time, compressive strength and sorptivity. The setting time is found to be unaffected by the presence of bacteria. It is found that compressive strength at both 7-days and 28-days of mortar cube increases with the increase of bacteria concentration. At the optimum bacteria dosage of 107 cells/ml, the average compressive strength increases by 58% (at 7 day) and 23% (at 28 day) over the control specimen. The sorpitivity coefficient decreases as the concentration of bacterial cells increases. The mineralogy and morphology of the calcium carbonate precipitation have been tested by XRD and FESEM.

The world is suffering from the COVID-19 pandemic. Nature has thrown a new challenge towards the healthcare professionals in the form of this new virus. As if that was not enough, we found an extremely rare, interesting and challenging case of mesenteric immature teratoma in this pandemic. Teratomas take origin from totipotent cells and may give rise to neoplasms that contain, in a helter-skelter fashion, bits of bone, epithelium, muscles, fat, nerves and other tissues. They are usually smaller than 10 cm, with cystic space, which is filled with a thick sebaceous secretion containing matted hair and sometimes teeth protruding from a nodular projection, which are unbrushed and may be carious. Though the usual sites are ovaries, occasionally testes, extragonadal sites may be affected. Classically the teratoma originates in the midline position. But in the abdomen, it usually takes the position of one of the paravertebral gutters, as in the present case, perhaps due to its size and weight of the solid part of the constituent elements. Due to its rarity it deserves the attention of the world and therefore we present to u this interesting case.

Bearing retainer instability is one of the major causes of failure in the ball bearings used in spacecraft systems. These bearing failures lead to mission failure or performance degradation of the spacecraft. The instability is characterized by intermittent torque fluctuations and severe audible noise in both low- and high-speed bearings. It also generates severe transient forces that result in high cage wear or fracture. A series of retainer designs was made and the possibility of instability under various operating conditions of a momentum/reaction wheel used in a spacecraft was studied. Various tests such as run-in test, temperature test, and overlubrication test were conducted to study the instability and select a design that is stable under all operating conditions. The study results showed that square pocket retainers are more stable compared to circular pocket retainers. � 2012 Copyright Taylor and Francis Group, LLC.

The success of a spacecraft mission depends to a great extent on the performance of the moving mechanical systems. The most common mode of failure in these systems is tribological. Tribological failures occur mainly due to non availability of lubricant at the working zone of the bearings as a result of degradation, evaporation and creep. The life of these moving mechanical systems could be extended, if lubricant is replenished by some means. This paper describes the development of a positive lubrication system named as command lubrication system (CLS). This is an active lubrication system which when actuated by external commands delivers lubricant to the bearings. It is actuated only when there is a demand for lubricant indicated by increase in frictional torque or bearing temperature. The outstanding feature of this system is that the lubricant is stored under ambient pressure and hence less chance of leakage. The CLS can solve the lubrication problem of spacecraft systems which require very long mission life of more than 20 years. It is also suitable to tribosystems in terrestrial devices.

The success of any satellite mission largely depends upon the performance of the attitude control systems such as gyroscopes and momentum/reaction wheels. The required life and performance quality of these rotating mechanisms are ensured by the selection of bearings and its lubrication. The design and development of lubrication system to meet the long-term uninterrupted performance is a challenging task before the tribologists. This article describes the developmental study of a lubrication system for long-term requirements of momentum/reaction wheels. The developed system is compact and can be placed inside the bearing unit assembly. It works on centrifugal force and able to supply lubricant continuously at a very low rate of few micrograms per hour for many years. Further, the system can be tuned for any flow rate depending on the requirement. � 2008 Springer Science+Business Media, LLC.

Laser microdrilling is the process of material removal by ablation using focused laser pulses. With brief preamble on laser system, how a micro-orifice is created successfully on 50mu;m thick copper foil using modified Nd:YAG ophthalmic laser is elucidated. The micro-orifice is required to control the flow of lubricant from the centrifugal lubricator used in spacecraft moving mechanisms. The orifices are characterized using scanning electron microscope (SEM), and the process parameters are optimized. Orifices from 1.5mu;m to 2.7mu;m diameter are produced. The work is further extended to drill microholes in 60mu;m copper wire. It is observed that the bead formed at melt zone near the hole can be conveniently used for microjoining. Copyright � Taylor & Francis Group, LLC.

The success of a spacecraft mission depends to a great extent on the performance of the moving mechanical systems. The most common mode of failure in these systems is tribological. Tribological failures occur mainly due to nonavailability of lubricant at the working zone of the bearings as a result of degradation, evaporation, and creep. The life of these moving mechanical systems could be extended if lubricant is replenished by some means. Therefore, to ensure long-term uninterrupted performance of these systems, an efficient lubricant replenishment system is essential. This article describes the development of a novel lubricant supply system that can supply lubricant for more than 30 years at a controlled rate of a few micrograms/hour. Experimental evaluation of the lubricator was carried out under different operating conditions experienced in a spacecraft. The results of the experiments are compared with the theoretical results obtained from the mathematical model and computational fluid dynamics (CFD) simulation. The lowest flow rate obtained was 3.5 ug/h from a lubricator with a flow control orifice diameter of 2.3 um. The results of the study show that the lubricator can provide a long-term uninterrupted supply of lubricant to the moving mechanical systems for a period of more than 30 years. An outstanding and most promising feature of this lubricator is that the flow rate at various stages of the life can be theoretically predicted using the developed mathematical model and the prediction can be experimentally verified before the system is put into service. Refereed/Peer-reviewed

Spacecraft, irrespective of their mission's purpose, contain a number of moving mechanical assemblies such as momentum/reaction wheels, control moment gyros, solar array drives, etc. Most problems encountered with these moving systems are related to tribology and, specifically, lubrication. Lubrication problems result from the loss of lubricant from the working zone by evaporation, surface migration, etc. Therefore, to ensure long-term uninterrupted performance of these systems, an efficient lubricant replenishment system is essential. This article describes the development of a novel lubricant supply system that can supply lubricant for more than 30 years at a controlled rate of few micrograms/hour. A mathematical model of a such lubrication system is developed to predict its useful life and performance. In addition, a computational fluid dynamics (CFD) simulation study of the lubricator is carried out and the results are used to verify and refine the theoretical model. Finally, the refined model is used to predict the performance of the lubricator for a period of 30 years. � Society of Tribologists and Lubrication Engineers.

Momentum wheels are spacecraft actuators of large angular momentum used for the attitude control and stabilization of spacecrafts. The on-orbit performance of spacecrafts depends largely on the performance of the momentum wheels which in turn depends on its bearings and its lubrication. Currently, the life cycle of spacecrafts are aimed to be around 20-30 years. However, the increases in size, complexity and life expectancy of spacecrafts demand advanced technologies especially in tribology and in turn the development of more innovative lubrication systems for long-term operation. This article reviews the tribological requirements of momentum wheels and the various lubrication systems used in the past and raises a necessity to develop a new system to cope with the new requirements. � 2009 Elsevier Ltd. All rights reserved.

The requirement to make low profile ohmic contacts to a piezo-resistive MEMS pressure sensor has highlighted limitations of ultrasonic wire bonding technology. Wire bonding typically uses 25-50 μm diameter gold or aluminium wire and ultrasonic welding to the contact pads of micro-electronic devices results in a contact wire proud of the pad surface. If the application involves the MEMS pressure sensor and contacts being encapsulated, then repetitive changes in pressure flexing the contact wires can lead to fracture. A possible solution is to scale down laser welding technology to fuse materials at the micron scale. For this purpose a precision ophthalmic surgical laser system has been modified to investigate optimum conditions for laser welding, both at the micron scale and for the typical geometries involved. Typical requirements involve a cylindrical contact wire to be bonded to a thin contact pad on the MEMS device. Since the pad size is of similar dimension to the wire, and the requirement for a low profile stable configuration, a keyhole welding strategy is required. The Nd:YAG based ophthalmic laser has been modified, the Q-switch removed and the output pulse width and energy controlled principally via control of the flashlamp.