153 research outputs found
Adult medulloblastoma: Clinical profile and treatment results of 18 patients
No full textThe objective of this article is to examine the clinicoradiological features and surgical outcomes of adult patients (>16 years) with medulloblastoma. An attempt was made to identify the predictors of poor outcome and assess patterns of relapse and to compare these with pediatric medulloblastoma. Retrospective case record analyses were performed on 18 adults (> 16 years) and 79 children (< 16 years) operated upon after January 1990, who had at least 5 years of follow-up. The following variables were assessed by bivariate analyses: age, location of the lesion, brainstem invasion, extent of excision and histological subtype. Statistical analysis was performed using chi-square test, Fischer's exact test and Student's t-test. Results revealed there was no gender preference. The tumor was located in the vermis in 12 patients (66.6%) and in the cerebellar hemisphere in six (16.6%). Calcification was observed in two cases (11.1%) and hydrocephalus was seen in six (33.3%). MRI evidence of brainstem infiltration was seen in three patients (16.6%). Total excision was achieved in 13 cases (72.2%), near total excision in four (22.2%) and subtotal excision in one. Major complications included fresh cranial nerve deficits in four patients (22.2%), hemiparesis and gait unsteadiness in three (16.6%), mutism in one and meningitis in two. All patients underwent adjuvant radiotherapy in the form of craniospinal irradiation with a posterior fossa boost. On follow-up, 11 patients (61.1%) were observed to have recurrence and all were located in the posterior fossa. All 11 subsequently underwent chemotherapy. Two patients had reoperation for residual/recurrent lesions causing raised intracranial symptoms. Five-year follow-up data showed that 10 patients (55.5%) were alive, five (27.7%) had died while three (16.6%) were lost to follow-up. In spite of recent advances in management, patients with medulloblastoma still have a poor prognosis. However, adults fared better than children. Vermian location had a better outcome in adults, but not in children. Desmoplastic variant histology was not observed to be a significant prognostic factor in the adult group while brain stem invasion carried a poor prognosis. (c) 2007 Elsevier Ltd. All rights reserved
Chern-Simons theory of magnetization plateaus on the kagome lattice
No full textFrustrated spin systems on Kagome lattices have long been considered to be a promising candidate for realizing exotic spin liquid phases. Recently, there has been a lot of renewed interest in these systems with the discovery of experimental materials such as Volborthite and Herbertsmithite that have Kagome like structures. In this thesis I will focus on studying frustrated spin systems on the Kagome lattice using a spin-1/2 antiferromagnetic XXZ Heisenberg model in the presence of an external magnetic field as well as other perturbations. Such a system is expected to give rise to magnetization platueaus which can exhibit topological characteristics in certain regimes.
We will first develop a flux-attachment transformation that maps the Heisenberg spins (hard-core bosons) onto a problem of fermions coupled to a Chern-Simons gauge field. This mapping relies on being able to define a consistent Chern-Simons term on the lattice. Using this newly developed mapping we analyse the phases/magnetization plateaus that arise at the mean-field level and also consider the effects of adding fluctuations to various mean-fi eld states. Along the way, we show how to discretize an abelian Chern-Simons gauge theory on generic 2D planar lattices that satisfy certain conditions. We find that as long as there exists a one-to-one correspondence between the vertices and plaquettes defined on the graph, one can write down a discretized lattice version of the abelian Chern-Simons gauge theory.
Using the newly developed flux attachment transformation, we show the existence of chiral spin liquid
states for various magnetization plateaus for certain range of parameters in the XXZ Heisenberg model in the presence of an external magnetic field. Speci cally, in the regime of XY anisotropy the ground states at the 1/3 and 2/3 plateau are equivalent to a bosonic fractional quantum Hall Laughlin state with filling fraction 1/2 and that the 5/9 plateau is equivalent to the first bosonic Jain daughter state at filling fraction 2/3.
Next, we also consider the effects of several perturbations: a) a chirality term, b) a Dzyaloshinskii-Moriya term, and c) a ring-exchange type term on the bowties of the kagome lattice, and inquire if they can also support chiral spin liquids as ground states. We find that the chirality term leads to a chiral spin liquid even in the absence of an uniform magnetic field, with an effective spin Hall conductance of 1/2 in the regime of XY anisotropy. The Dzyaloshinkii-Moriya term also leads a similar chiral spin liquid but only when this term is not too strong. An external magnetic field when combined with some of the above perturbations also has the possibility of giving rise to additional plateaus which also behave like chiral spin liquids in the XY regime. Under the in influence of a ring-exchange term we find that provided its coupling constant is large enough, it may trigger a phase transition into a chiral spin liquid by the spontaneous breaking of time-reversal invariance.
Finally, we also present some numerical results based on some exact diagonalization studies. Here, we specifically focus on the 2/3-magnetization plateau which we previously argued should be a chiral spin liquid with a spin hall conductance of 1/2 . Such a topological state has a non-trivial ground state degeneracy and it excitations are described by semionic quasiparticles. In the numerical analysis, we analyse the ground state degeneracy structure on various Kagome clusters of different sizes. We compute modular matrices from the resultant minimally entangled states as well as the Chern numbers of various eigenstates all of which provide strong evidence that the 2/3-magnetization plateau very closely resembles a chiral spin liquid state with the expected characteristics.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-12-01The student, Ponnuraj Krishnakumar, accepted the attached license on 2016-11-23 at 22:00.The student, Ponnuraj Krishnakumar, submitted this Dissertation for approval on 2016-11-23 at 22:29.This Dissertation was approved for publication on 2016-11-29 at 10:54.DSpace SAF Submission Ingestion Package generated from Vireo submission #10318 on 2017-02-28 at 14:36:45Made available in DSpace on 2017-03-01T16:36:55Z (GMT). No. of bitstreams: 2
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No full textWe recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could selfassemble into Ca2+-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca2+ involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca2+ influx.Fil: Zanetti, Maria Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Bello, Oscar Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Wang, Jing. University of Yale. School of Medicine; Estados UnidosFil: Coleman, Jeff. University of Yale. School of Medicine; Estados UnidosFil: Cai, Yiying. University of Yale. School of Medicine; Estados UnidosFil: Sindelar, Charles V.. University of Yale. School of Medicine; Estados UnidosFil: Rothman, James E.. University of Yale. School of Medicine; Estados UnidosFil: Krishnakumar, Shyam S.. University of Yale. School of Medicine; Estados Unido
Dimensions of sex working - A cross comparison of different modes in Kerala
No full textSex working is the business or practice of engaging in sexual activity in exchange for payment. It is sometimes described as commercial sex or hooking. Sex work is the provision of sexual services for money or goods. The legal status of sex working varies from country to country, from being legal and considered a profession to being punishable by death. From the days of Devadasis to the present world of wireless networking, sex workers have been very evidently seen in the country and rest of the world. This study is based on the experiences from Kerala. Although no one is born as a sex worker, several push and pull factors turn then as sex worker. There are different modes of sex working and attempt is made to understand the push factors in entering into this job? What are the socio-economic conditions of these communities? What is their mode of work? Is there a difference and relative merit over one mode of sex working compared to than other forms? the results of the study show that most of the sex workers entered into the profession due to financial stress at home and sexual assault that they faced at their younger ages. The nature of working varied from mode of sex work they do. All sex workers are aware of their health conditions and undergo periodic checkups. Ageing is a factor in this profession and these women are to be rehabilitated. They wish to continue this profession till they are aged and wish to get rehabilitated by the society by helping them to do other forms of economic activity
Development and molecular characterization of polymeric micro-nanofibrous scaffold of a defined 3-D niche for in vitro chemosensitivity analysis against acute myeloid leukemia cells
No full textMaya S Nair,1 Ullas Mony,1 Deepthy Menon,1 Manzoor Koyakutty,1 Neeraj Sidharthan,2 Keechilat Pavithran,2 Shantikumar V Nair,1 Krishnakumar N Menon11Amrita Centre for Nanosciences and Molecular Medicine, 2Department of Oncology, Amrita Institute of Medical Sciences and Research Centre, Amrita Vishwa Vidyapeetham University, Kerala, IndiaAbstract: Standard in vitro drug testing employs 2-D tissue culture plate systems to test anti-leukemic drugs against cell adhesion-mediated drug-resistant leukemic cells that harbor in 3-D bone marrow microenvironments. This drawback necessitates the fabrication of 3-D scaffolds that have cell adhesion-mediated drug-resistant properties similar to in vivo niches. We therefore aimed at exploiting the known property of polyurethane (PU)/poly-L-lactic acid (PLLA) in forming a micro-nanofibrous structure to fabricate unique, not presented before, as far as we are aware, 3-D micro-nanofibrous scaffold composites using a thermally induced phase separation technique. Among the different combinations of PU/PLLA composites generated, the unique PU/PLLA 60:40 composite displayed micro-nanofibrous morphology similar to decellularized bone marrow with increased protein and fibronectin adsorption. Culturing of acute myeloid leukemia (AML) KG1a cells in FN-coated PU/PLLA 60:40 shows increased cell adhesion and cell adhesion-mediated drug resistance to the drugs cytarabine and daunorubicin without changing the original CD34+/CD38-/CD33- phenotype for 168 hours compared to fibronectin tissue culture plate systems. Molecularly, as seen in vivo, increased chemoresistance is associated with the upregulation of anti-apoptotic Bcl2 and the cell cycle regulatory protein p27Kip1leading to cell growth arrest. Abrogation of Bcl2 activity by the Bcl2-specific inhibitor ABT 737 led to cell death in the presence of both cytarabine and daunorubicin, demonstrating that the cell adhesion-mediated drug resistance induced by Bcl2 and p27Kip1in the scaffold was similar to that seen in vivo. These results thus show the utility of a platform technology, wherein drug testing can be performed before administering to patients without the necessity for stromal cells.Keywords: daunorubicin, cytarabine, Bcl2, p27Kip1, cell adhesion-mediated drug resistanc
Meningiomas of the Lateral Ventricle-A Report of 15 cases
No full textLateral ventricular meningiomas are rare tumours that pose considerable surgical challenge. This study attempts to analyse some of the important clinical features of these tumours and review technical considerations in surgery for lateral ventricular meningiomas. A retrospective analysis of the case records of patients with lateral ventricular meningiomas operated in our institute since 1998 with a minimum of one year follow up was done. The variables analysed included age, sex, clinical presentation, imaging characteristics, histopathology and operative details. Outcome was analysed using the Glasgow outcome score (GOS). Fifteen patients with a mean age of 40.6 years formed the study group. A female preponderance was observed (M:F 5:10). Raised intracranial pressure was the predominant symptom at presentation (10/15; 66%) followed by visual field deficits (6/15; 40%) and contralateral motor deficits (5/15; 33.3%). One patient presented with evidence of intratumoural bleed. The tumour was on the right side in 7 patients and on the left side in 8 patients. The lesion was located in the trigone of the lateral ventricle in 13 patients and in the body of the ventricle in two. The tumours were excised through a parietooccipital approach in 11 (73.33%) patients and through a middle temporal gyrus approach in 4 (26.66%).The tumour recurred in 2 patients, both tumours being histologically fibroblastic variants. Fresh operative complications included motor deficits in 3, contralateral homonymous hemianopia in 2, dysphasia in 1, refractory seizures in 2 and loculated hydrocephalus in one. We had no operative mortality. At last follow-up for 10 patients were in GOS 5, two were in GOS 4 and three in GOS 3. Lateral ventricular meningiomas are difficult tumours to operate. Total surgical excision through a superior parietal lobule or middle temporal gyrus approach is possible in most cases with minimal morbidity
Dissecting intracranial aneurysms presenting as subarachnoid haemorrhage: report of two cases and review of literature
No full textSubarachnoid haemorrhage due to intracranial non-traumatic dissecting aneurysms is rare. Most of the published reports refer to dissecting aneurysms in the vertebrobasilar territory. Anterior circulation dissecting aneurysms are rare and their pathogenesis, clinical features, angiographic findings and management are a matter of debate. Management of patients with intracranial arterial dissection is unclear. Unlike the well-established proximal occlusion and trapping approaches to vertebral artery dissections, choices of interventions for anterior circulation and basilar dissecting aneurysms are limited, and most reports have been limited to wrapping techniques for arterial wall reinforcement. The role of anticoagulation therapy in the presence of subarachnoid haemorrhage is also a matter of debate. As no clear-cut guidelines are available, treatment should be tailored to the individual patient. We describe two cases of intracranial dissecting aneurysms, which presented as subarachnoid haemorrhage (SAH) and discuss the management issues
Subfrontal gangliocytoma masquerading as olfactory groove meningioma
No full textWe describe a rare case of an unusually located gangliocytoma. The conventional magnetic resonance imaging (MRI) appearance was suggestive of an olfactory groove meningioma. However, advanced MRI sequences (diffusion-weighted imagingDWI; perfusion MRI; susceptibility-weighted imagingSWI; MR spectroscopyMRS) revealed features more consistent with a glial neoplasm
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