Biomedical subjects

S Bose

Publications and source records attributed to S Bose.

At least 19 recordsLinked to original sources

PubMed2006

Microstructure and deformation behavior of biocompatible TiO2 nanotubes on titanium substrate.

Titanium oxide coatings have been shown to exhibit desirable properties as biocompatible coatings. We report on the quantitative microstructure characterization and deformation behavior of TiO(2) nanotubes on Ti substrate. Nanotubes were processed using anodic oxidation of Ti in a NaF electrolyte solution. Characterization of the as-processed coatings was conducted using scanning electron microscopy and focused ion beam milling. Increases in anodization time had no significant effect on tube diameter or tube wall thickness. Coating thickness, however, increased with time up to 2h of anodization, at which point an equilibrium thickness was established. Nanoindentation was used to probe the mechanical response in terms of Young's modulus and hardness. Progressively higher values of elastic modulus were obtained for thinner films consistent with increasing effects of the Ti substrate. A possible deformation mechanism of densification of the porous oxide and wear of the dense surface is suggested and discussed.

Biomechanical Phenomena↗

PubMed2006

Entanglement of two impurities through electron scattering.

We study how two magnetic impurities embedded in a solid can be entangled by an injected electron scattering between them and by subsequent measurement of the electron's state. We start by investigating an ideal case where only the electronic spin interacts successively through the same unitary operation with the spins of the two impurities. We find conditions for the impurity spins to be maximally entangled with a significant success probability. We then consider a more realistic description which includes both the forward and backscattering amplitudes. In this scenario, we obtain the entanglement between the impurities as a function of the interaction strength of the electron-impurity coupling. We find that our scheme allows us to entangle the impurities maximally with a significant probability.

Journal Article↗

PubMed2006

Entanglement and dynamics of spin chains in periodically pulsed magnetic fields: accelerator modes.

We study the dynamics of a single excitation in a Heisenberg spin-chain subjected to a sequence of periodic pulses from an external, parabolic, magnetic field. We show that, for experimentally reasonable parameters, a pair of counterpropagating coherent states is ejected from the center of the chain. We find an illuminating correspondence with the quantum time evolution of the well-known paradigm of quantum chaos, the quantum kicked rotor. From this we can analyze the entanglement production and interpret the ejected coherent states as a manifestation of the so-called "accelerator modes" of a classically chaotic system.

Journal Article↗

PubMed2006

BRCA1 and FOXA1 proteins coregulate the expression of the cell cycle-dependent kinase inhibitor p27(Kip1).

We have previously shown that the breast cancer susceptibility gene, BRCA1, can transcriptionally activate the p27(Kip1) promoter. The BRCA1-responsive element was defined as a 35 bp region from position -545 to -511. We next determined that within this region is also a potential binding site for the transcription factor Forkhead box (FOX)A1. RNA and protein analysis as well as immunohistochemistry showed that expression of FOXA1 correlated with the expression of the estrogen receptor in a panel of breast cancer cell lines and tissues. In transient transfection reporter assays, FOXA1 could activate the p27(Kip1) promoter. Cotransfection of BRCA1 and FOXA1 resulted in a synergistic activation of the p27(Kip1) promoter. Mutation of the FOXA1 DNA-binding site in the p27(Kip1) promoter-luciferase construct significantly diminished the activity of FOXA1 alone or in combination with BRCA1. Cotransfection of FOXA1 and BRCA1 resulted in a greater amount of each protein compared to transfection of each expression vector alone. The half-life of FOXA1 was increased when coexpressed with BRCA1. Electrophoretic mobility shift assay analysis demonstrated that FOXA1 could bind to a wild-type oligonucleotide containing the FOXA1 binding site in the p27(Kip1) promoter, but this binding was lost upon mutation of this FOXA1 binding site. The protein-DNA binding complex could be supershifted with an antibody directed against FOXA1. The activity of the p27(Kip1) promoter as well as FOXA1 expression was reduced in cells treated with BRCA1 siRNA, thus silencing the expression of BRCA1 protein. In summary, we identified a FOXA1 binding site within the BRCA1-responsive element of the p27(Kip1) promoter and showed that FOXA1 activated the promoter alone and in conjunction with BRCA1. Furthermore, we identified high expression of FOXA1 in breast cancer cell lines and tissues, discovered a role for BRCA1 in the regulation of p27(Kip1) transcription and a possible interaction with BRCA1.

BRCA1 Protein↗

PubMed2006

Entanglement reciprocation between qubits and continuous variables.

We investigate how entanglement can be transferred between qubits and continuous-variable (CV) systems. We find that one ebit borne in maximally entangled qubits can be fully transferred to two CV systems which are initially prepared in a pure separable Gaussian field with high excitation. We show that it is possible to retrieve the entanglement back to qubits from the entangled CV systems. The deposition of multiple ebits from qubits to the initially separable CV systems is also pointed out. We show that the entanglement transfer and retrieval are done at a quasisteady state.

Journal Article↗

PubMed2006

The impact of image guided needle biopsy on the outcome of mammographically detected indeterminate microcalcification.

A study was carried out to examine the impact of development in image guided needle biopsy on the outcome of mammographically detected indeterminate microcalcification. Between 01.04.1991 and 31.03.2001, the South East London Breast Screening Programme detected 392 cases of indeterminate microcalcificaton. Histological diagnosis was obtained using open biopsy, fine needle aspiration cytology (FNAC), 18/14 G wide bore needle core biopsy (WBNCB) and 11 G vacuum assisted core biopsy (VACB). The study period group was divided into two. Group A (between 01.04.1991 and 31.03.1996) and group B (between 01.04.1996 and 31.03.2001). There was a significant reduction in the benign open biopsy rate in group B compared to group A (25% vs. 51%) (P=0.0001). Of the malignant cases, there is a higher percentage of ductal carcinoma in situ (DCIS) in group B compared to group A (77% vs. 62%). In conclusion, the implementation of more effective methods of image guided biopsy has led to a 50% reduction in benign open biopsies for indeterminate microcalcification and to an increase in the detection of DCIS.

Biopsy, Needle↗

PubMed2006

The elusive multiple self-healing squamous epithelioma (MSSE) gene: further mapping, analysis of candidates, and loss of heterozygosity.

The MSSE gene predisposes to multiple invasive but self-healing skin tumours (multiple self-healing epitheliomata). MSSE was previously mapped to chromosome 9q22-q31 and a shared haplotype in affected families suggested a founder mutation. We have refined the MSSE critical region (<1 cM, <1 Mb) between the zinc-finger gene ZNF169 and the Fanconi anaemia gene FANCC. By genetic mapping we have excluded ZNF169 and FANCC as well as PTCH (PATCHED) and TGFBR1 (transforming growth factor beta receptor type-1) genes. The CDC14B cell cycle phosphatase gene also lies in the region but screening of the complete coding region revealed no mutation in MSSE patients. Somatic cell hybrids created by haploid conversion of an MSSE patient's cells enabled screening of the MSSE chromosome 9 and showed no CDC14B deletion or mutation that abrogates CDC14B mRNA expression. Thus, CDC14B is unlikely to be the MSSE gene. We also report the first molecular analysis of MSSE tumours showing loss of heterozygosity of the MSSE region, with loss of the normal allele, providing the first evidence that MSSE is a tumour suppressor gene.

Base Sequence↗

PubMed2006

Three-month change in cerebral glucose metabolism in patients with nonarteritic ischemic optic neuropathy.

BACKGROUND: No specific therapy is available for non-arteritic ischemic optic neuropathy (NAION), a blinding disease, which is related to microvascular insufficiency of the optic disc and white matter lesions in brain MRI representing ischemia. We hypothesize that pentoxifylline, traditionally used for treatment of peripheral vascular disease due to its ability to decrease viscosity and increase erythrocyte flexibility, may be useful to improve blood flow in patients with NAION. Positron emission tomography (PET) to determine the change in glucose metabolic rate in the visual cortex of patients with NAION versus age-matched controls was performed after 3 months' administration of pentoxifylline. METHODS: Eight patients clinically diagnosed with NAION underwent clinical and laboratory evaluation, brain MRI and PET with fluoride-18 fluorodeoxyglucose (FDG). All patients were treated with oral pentoxifylline 400 mg three times a day for a period of at least 3 months. Three patients were included in the final PET data analysis. RESULTS: At baseline, PET revealed bilateral metabolic decreases especially in the ventral visual stream in all patients compared with 56 age- and gender-normalized controls. Metabolic changes were seen in the dorsal stream areas 17, 18, and 19, cerebellar region, dorsolateral prefrontal cortex, medial temporal lobe, and frontal eye fields 8 and 6. At 3 months following pentoxifylline, all three patients included in the final PET data analysis showed partial normalization from the baseline metabolism. CONCLUSIONS: Metabolic imaging with FDG-PET in NAION provides functional information not attainable with conventional brain MRI. The exact relevance of these results, and the role of pentoxifylline in these metabolic changes, should be determined by means of a larger randomized and controlled trial.

Administration, Oral↗

PubMed2005

Upper limits on a stochastic background of gravitational waves.

The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of omega0 < 8.4 x 10(-4) in the 69-156 Hz band is approximately 10(5) times lower than the previous result in this frequency range.

Journal Article↗

PubMed2005

Limits on gravitational-wave emission from selected pulsars using LIGO data.

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.

Journal Article↗

PubMed2005

Anal cytology: is there a role for reflex HPV DNA testing?

There is an increased incidence of anal squamous carcinoma and its precursor lesions (anal intraepithelial neoplasia [AIN]) among persons who engage in anal-receptive sex. Analogous to cervical cancer screening, anal Papanicplaou (Pap) smears currently are used to screen these high-risk populations. Human papilloma virus (HPV) has been implicated in anal carcinoma pathogenesis and this study was performed to assess the potential role of HPV DNA testing as an adjunct to anal cytology. We correlated cytological diagnoses and HPV DNA (Digene Hybrid Capture [HC II] assay) in anal specimens collected in SurePath liquid medium from 118 patients; 54.8% of cases diagnosed as atypical squamous cells of undetermined significance (ASC-US) and 87.8% diagnosed as low-grade squamous intraepithelial lesion (LSIL) or above tested positive for high- risk HPV DNA (B+). High-grade SIL (HSIL) was present in 31 of the 51 patients with follow-up. Although a cytological diagnosis of ASC-US or above was a reliable indicator for AIN, cytology frequently did not accurately predict the grade of SIL in subsequent biopsy. Our findings suggest that reflex HPV DNA testing would be helpful in triaging patients diagnosed with ASC-US. However, patients diagnosed with LSIL or above should go directly to ansocopic biopsy.

Adult↗

PubMed2004

Towards quantum entanglement in nanoelectromechanical devices.

We study arrays of mechanical oscillators in the quantum domain and demonstrate how the motions of distant oscillators can be entangled without the need for control of individual oscillators and without a direct interaction between them. These oscillators are thought of as being members of an array of nanoelectromechanical resonators with a voltage being applicable between neighboring resonators. Sudden nonadiabatic switching of the interaction results in a squeezing of the states of the mechanical oscillators, leading to an entanglement transport in chains of mechanical oscillators. We discuss spatial dimensions, Q factors, temperatures and decoherence sources in some detail, and find a distinct robustness of the entanglement in the canonical coordinates in such a scheme. We also briefly discuss the challenging aspect of detection of the generated entanglement.

Journal Article↗

PubMed2004

Effects of MgO-CaO-P2O5-Na2O-based additives on mechanical and biological properties of hydroxyapatite.

In this research, we improved densification, hardness, and compression strength of synthetic hydroxyapatite (HAp) ceramics by introducing small quantities of MgO-CaO-P(2)O(5)-Na(2)O-based sintering additives. Biological properties of HAp were not altered by this procedure. Phase analyses were performed by using a Philips Xpert fully automated diffractometer with Co K-alpha radiation to understand the influence of additives on phase purity in the final products. All compositions were characterized at green and sintered densities to understand the influence of additives on densification. Some of the compositions showed >40% increase in Vickers microhardness compared with pure HAp processed under the same conditions. Improvement in compression strength was also detected in some compositions. In vitro biological testing used a modified human osteoblast cell line to test biocompatibility, cell attachment, and cell proliferation. All these compositions were nontoxic and biocompatible. Our results indicate that MgO-CaO-P(2)O(5)-Na(2)O-based sintering additives can be used to improve both mechanical and biological properties of HAp ceramics.

Biocompatible Materials↗

PubMed2004

CaO--P2O5--Na2O-based sintering additives for hydroxyapatite (HAp) ceramics.

We have assessed the effect of CaO--P2O5--Na2O-based sintering additives on mechanical and biological properties of hydroxyapatite (HAp) ceramics. Five different compositions of sintering additives were selected and prepared by mixing of CaO, P2O5, and Na2CO3 powders. 2.5 wt% of each additive was combined with commercial HAp powder, separately, followed by ball milling, and sintering at 1250 degrees C and 1300 degrees C in a muffle furnace. Green and sintered densities of the compacts were analyzed for the influence of additives on densification of HAp. Phase analyses were carried out using an X-ray diffractometer. Vickers microhardness testing was used to evaluate hardness of sintered compacts of different compositions. A maximum microhardness of 4.6 (+/- 0.28) GPa was attained for a composition with 2.5 wt% addition of CaO:P2O5:Na2O in the ratio of 3:3:4. Results from mechanical property evaluation showed that some of these sintering additives improved failure strength of HAp under compressive loading. Maximum compressive strength was observed for samples with 2.5 wt% addition of CaO. Average failure strength for this set of samples was calculated to be 220 (+/- 50) MPa. Cytotoxicity, and cell attachment studies were carried out using a modified human osteoblast cell line called OPC-1. In vitro results showed that these compositions were non-toxic. Some sintering aids enhanced cell attachment and proliferation, which was revealed from SEM examination of the scaffolds seeded with OPC-1 cells.

Bone Substitutes↗

PubMed2004

Glycaemic consequences of HIV and highly active antiretroviral therapy: a pilot study and review of literature.

The metabolic consequences of HIV and AIDS are accentuated in the setting of highly active antiretroviral therapy. Peripheral lipodystrophy, central adiposity, hyperlipidaemia, insulin resistance and diabetes mellitus are frequent associations of protease inhibitor containing highly active antiretroviral therapy regimens. Ninety patients aged 25-50 years (males 52, females 38), seropositive for HIV 1 and 2 or both were selected to see the glycaemic profiles in asymptomatic early HIV disease with CD4 counts > 100/microl and to compare this with the glycaemic profile of (a) advanced HIV disease (CD4 counts < 200/microl), not on highly active antiretroviral therapy and (b) advanced HIV disease (CD4 counts < 200/microl), on uninterrupted non-protease inhibitor highly active antiretroviral therapy > 6 months. All the patients were grouped into 3: (1) Group A: CD4 counts > 500/microl (n=37), highly active antiretroviral therapy naive, (2) group B: CD4 counts < 200/microl (n=21), not on highly active antiretroviral therapy, and (3) group C: CD4 counts < 200/microl, receiving uninterrupted non-protease inhibitor based highly active antiretroviral therapy for > 6 months (n=32). The fasting blood glucose, glycosylated Hb (HbA1c) levels, were measured in all the patients in 3 groups and significance of difference between means was calculated among various groups. Body weight and waist-hip ratio were also measured. The results were analysed and compared with other studies.

Adult↗

PubMed2003

Differential nicotinic acetylcholine receptor subunit expression in the human hippocampus.

Neuronal nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels composed of alpha and beta subunits with specific structural, functional and pharmacological properties. In this study the distribution of alpha3, alpha4, alpha7, beta2 and beta4 nAChR subunits in the human hippocampus was investigated using immunohistochemistry. Most pyramidal neurons, pre-alpha cells of the entorhinal cortex and dentate granule cells were immunoreactive for all subunits. Small islands of alpha7 immunoreactive cells were present in the outer presubiculum. alpha4 and beta2, and alpha3, alpha4 and beta2 immunoreactive fibre tracts were present in the stratum radiatum and subiculum, respectively, suggesting nAChRs may play a role in modulating inputs to the hippocampus via Schaffer collaterals and along the perforant pathway. Some astrocytes were immunoreactive for alpha3, alpha7 and beta4 subunits. Immunoreactivity to all subunits was noted in association with blood vessels. These results indicate the involvement of multiple nAChR subtypes in the modulation of both neuronal and non-neuronal functions in the human hippocampus.

Adult↗

PubMed2002

Vacuum induced spin-1/2 Berry's phase.

We calculate the Berry phase of a spin-1/2 particle in a magnetic field considering the quantum nature of the field. The phase reduces to the standard Berry phase in the semiclassical limit and the eigenstate of the particle acquires a phase in the vacuum. We also show how to generate a vacuum induced Berry phase considering two quantized modes of the field which has an interesting physical interpretation.

Journal Article↗

PubMed2002

Entanglement concentration using quantum statistics.

We propose an entanglement concentration scheme which uses only the effects of quantum statistics of indistinguishable particles. This establishes the fact that useful quantum information processing can be accomplished by quantum statistics alone. Because of the basis independence of statistical effects, our protocol requires less knowledge of the initial state than most entanglement concentration schemes. Moreover, no explicit controlled operation is required at any stage.

Journal Article↗