Mermera: Non-Coherent Distributed Shared Memory for Parallel Computing

The proliferation of inexpensive workstations and networks has prompted several researchers to use such distributed systems for parallel computing. Attempts have been made to offer a shared-memory programming model on such distributed memory computers. Most systems provide a shared-memory that is coherent in that all processes that use it agree on the order of all memory events. This dissertation explores the possibility of a significant improvement in the performance of some applications when they use non-coherent memory. First, a new formal model to describe existing non-coherent memories is developed. I use this model to prove that certain problems can be solved using asynchronous iterative algorithms on shared-memory in which the coherence constraints are substantially relaxed. In the course of the development of the model I discovered a new type of non-coherent behavior called Local Consistency. Second, a programming model, Mermera, is proposed. It provides programmers with a choice of hierarchically related non-coherent behaviors along with one coherent behavior. Thus, one can trade-off the ease of programming with coherent memory for improved performance with non-coherent memory. As an example, I present a program to solve a linear system of equations using an asynchronous iterative algorithm. This program uses all the behaviors offered by Mermera. Third, I describe the implementation of Mermera on a BBN Butterfly TC2000 and on a network of workstations. The performance of a version of the equation solving program that uses all the behaviors of Mermera is compared with that of a version that uses coherent behavior only. For a system of 1000 equations the former exhibits at least a 5-fold improvement in convergence time over the latter. The version using coherent behavior only does not benefit from employing more than one workstation to solve the problem while the program using non-coherent behavior continues to achieve improved performance as the number of workstations is increased from 1 to 6. This measurement corroborates our belief that non-coherent shared memory can be a performance boon for some applications

Modelling of DMNB Content for Marked Plastic Explosives

2,3-dimethyl-2,3-dinitrobutane (DMNB) has been internationally accepted as an additive forthe purpose of marking, as it has desired vapour pressure for reliable detection. It is reportedto be compatible with known explosive formulations and has a good shelf life. Explosivecompositions with DMNB as marking agent can be detected in the temperature range –20 ºC to+ 50 ºC. This paper describes modelling for quantifying activation energy for depletion of  DMNBin the marked explosives, period for definite detection of the marked explosives and optimuminitial concentration needed for the detection of DMNB content in the marked  plastic explosives

Ocular Langerhans Cell Histiocytosis (A Multisystem Involvement of Langerhans Cell Histiocytosis)

A 2 year old boy was referred from paediatrics OPD to Eye OPD with chief complaint of Multiple conjunctival cyst since 15 days. The patient had a prior history of recurrent chest infections. Requiring hospitalisation since 7 months of age. Upon visual acuity examination, the patient seemed to follow light.Fundus examination of both eyes were within normal limits.H& E sections of the lesions showed collection of histiocytes typical of Langerhans Cell Histiocytosis.Patient was treated with multiple cycles of Vinblastine and predinisolone as per LCH 3 guidelines. Langerhans cell histiocytosis (LCH), the most common histiocytic disorder in children. LCH lesions are granulomatous lesions consisting of pathologic “Langerhans cells” (LCs), lymphocytes (primarily T-cells), eosinophils, and macrophages. The incidence of LCH is estimated to be around 5–10 cases per million children per year and 1–2 cases per million adults per year with a male is to female ratio 1.2:1.Its pathology is ‘Misguided Myeloid Differentiation’ where state of differentiation of myeloid precursor in which activating MAPK mutation arises determines the extent and severity of disease[1]. The current standard of care for initial therapy is vinblastine/prednisone for one year

Amniotic membrane transplantation in ocular surface disorders: A review

Amniotic membrane (AM) was first used as a biomaterial in ophthalmic surgery in 1938. It was applied as a conjunctival replacement following symblepharon release. The durability, pliability and versatility of AM make it a useful adjunctive treatment in various ophthalmic procedures. This review aims to highlight the new developments, mechanisms of action, and established indications of amniotic membrane transplantation (AMT) that have been published in the last few years

Late post-traumatic flap dislocation and macrostriae after laser in situ keratomileusis

We report an unusual flap-related complication that occurred 4 years after uneventful laser in situ keratomileusis (LASIK) performed in the eye of a 20-year-old woman. She developed dislocation with partial infolding of the LASIK flap with macrostriae and epithelial ingrowth in her left eye after trauma by a wooden chip. The flap was refloated, stretched, smoothened, and hydrated on both under and outer surfaces after epithelial debridement. At 1 week, the uncorrected visual acuity was 20/20 with absence of flap striae. The present case highlights that flap adhesions are not very strong even months and years after LASIK. Flap refloatation and stretching with hydration on both sides of the flap are effective in removing flap striae