The median function on graphs with bounded profiles

AbstractThe median of a profile π=(u1,…,uk) of vertices of a graph G is the set of vertices x that minimize the sum of distances from x to the vertices of π. It is shown that for profiles π with diameter θ the median set can be computed within an isometric subgraph of G that contains a vertex x of π and the r-ball around x, where r>2θ−1−2θ/|π|. The median index of a graph and r-joins of graphs are introduced and it is shown that r-joins preserve the property of having a large median index. Consensus strategies are also briefly discussed on a graph with bounded profiles

Evaluation of Thermal Management Solutions for Power Semiconductors

This thesis addresses the thermal management and reliability concerns of power semiconductor devices from die to system level packaging design. Power electronics is a continuously evolving and challenging field. Systems continue to evolve, demanding increasing functionality within decreasing packaging volume, whilst maintaining stringent reliability requirements. This typically means higher volumetric and gravimetric power densities, which require effective thermal management solutions, to maintain junction temperatures of devices below their maximum and to limit thermally induced stress for the packaging medium. A comparison of thermal performance of Silicon and Silicon Carbide power semiconductor devices mounted on Polycrystalline Diamond (PCD) and Aluminum Nitride (AlN) substrates has been carried out. Detailed simulation and experimental analysis techniques show a 74% reduction in junction to case thermal resistance (Rth (j-c)) can be achieved by replacing the AlN insulating layer with PCD substrate. In order to improve the thermal performance and power density of polycrystalline diamond substrates further at the system level, direct liquid cooling technique of Direct Bonded Copper (DBC) substrates were performed. An empirical model was used to analyse the geometric and thermo-hydraulic dependency upon thermal performance of circular micro pins fins. Results show that micro pin fin direct cooling of DBC can reduce the number of thermal layers in the system, and reduce the thermal resistance by 59% when compared to conventional DBC cooling without a base plate. Thermal management and packaging solutions for the wide band gap semiconductors, such as GaN, is also described in detail. Comparisons of face up and flip chip thermal performance of GaN on Sapphire, Silicon and 6H-SiC substrates in a T0-220 package system is presented. Detailed thermal simulation results analysed using ANSYS® show that a flip chip mounted GaN on sapphire substrate can reduce junction to case thermal resistance by 28% when compared against the face up mounted technique

Do younger women with non-metastatic and non-inflammatory breast carcinoma have poor prognosis?

BACKGROUND: Controversy abounds over whether breast cancer in younger women is more aggressive than those in older. The aim of the study was to assess the influence of age on long-term survival of women with breast carcinoma. MATERIALS AND METHODS: Patients with non-metastatic and non-inflammatory invasive breast carcinoma treated at the Regional Cancer Centre, Trivandrum, Kerala, India during 1990–93 were divided into 4 age groups as < 40 years, 40–49, 50–59, and > 60 years. The overall survival (OS) for each age group was estimated using the Kaplan-Meier method in relation to the primary tumor (T) and the axillary node status (N). The OS of the various age groups were compared using the log-rank test. Hazard ratio and 95% confidence interval for each age group was estimated using Cox-regression model after adjusting for T and N. RESULTS: Between 1990–1993, 1701 women (26%, <40 years) reported with non-metastatic and non-inflammatory invasive breast carcinoma. Overall survival (OS) of all the women was 52.6 % (standard error 1%) at 10 years. The OS for women with age < 40 years and with T3 and T4 disease status was 36.6% and 10.4% respectively and for those in 40–49 age group was 41.9% and 33.5%. The 10-year OS for women with node positive (N1) disease was 24.6% in < 40 years and 45.2% in the 40–49 age group (p = 0.0006). After adjusting for tumor and node stage the relative risk for death was 24% lower for women in 40–49 age group as compared to women <40 years of age. CONCLUSION: Women under 40 years with T3/ T4 breast lesions and/or positive axillary nodes were found to have a significantly poorer survival

On The Center Sets and Center Numbers of Some Graph Classes

For a set $S$ of vertices and the vertex $v$ in a connected graph $G$, $\displaystyle\max_{x \in S}d(x,v)$ is called the $S$-eccentricity of $v$ in $G$. The set of vertices with minimum $S$-eccentricity is called the $S$-center of $G$. Any set $A$ of vertices of $G$ such that $A$ is an $S$-center for some set $S$ of vertices of $G$ is called a center set. We identify the center sets of certain classes of graphs namely, Block graphs, $K_{m,n}$, $K_n-e$, wheel graphs, odd cycles and symmetric even graphs and enumerate them for many of these graph classes. We also introduce the concept of center number which is defined as the number of distinct center sets of a graph and determine the center number of some graph classes

Supravesical hernia – A rare cause of intestinal obstruction

AbstractSupravesical hernia is an unusual type of hernia. It is of two types: internal and external [Skandalakis JE, Gray SW, Burns WB, Sangmalee U, Sorg JL. Internal and external supravesical hernia. Am Surg 1976 Feb;42(2):142–6]. We are reporting a case of internal supravesical hernia, in a 62-year-old gentleman to call attention to the entity, as a rare cause of intestinal obstruction

Median computation in graphs using consensus strategies

Following the Majority Strategy in graphs, other consensus strategies, namely Plurality Strategy, Hill Climbing and Steepest Ascent Hill Climbing strategies on graphs are discussed as methods for the computation of median sets of profiles. A review of algorithms for median computation on median graphs is discussed and their time complexities are compared. Implementation of the consensus strategies on median computation in arbitrary graphs is discussed

The plurality strategy on graphs

The Majority Strategy for finding medians of a set of clients on a graph can be relaxed in the following way: if we are at v, then we move to a neighbor w if there are at least as many clients closer to w than to v (thus ignoring the clients at equal distance from v and w). The graphs on which this Plurality Strategy always finds the set of all medians are precisely those for which the set of medians induces always a connected subgraph

Tuberculosis and metastatic carcinoma coexistence in axillary lymph node: A case report

BACKGROUND: Coexistence of cancer and tuberculosis in axillary lymph nodes is rare. Only seven cases have been reported in the literature. CASE REPORT: We report here a case of infiltrating ductal carcinoma breast metastasizing to the axillary lymph node along with tubercular granuloma in the same lymph node without primary mammary or pulmonary tuberculosis. CONCLUSION: Primary tuberculosis coexisting with carcinoma is of rare occurrence. A possibility should always be borne in mind especially in patients from endemic areas

Marrow Stromal Cell Infusion Rescues Hematopoiesis in Lethally Irradiated Mice despite Rapid Clearance after Infusion

Marrow stromal cells (MSCs, also termed mesenchymal stem cells) have been proposed as a promising cellular therapy for tissue injury including radiation-induced marrow failure, but evidence for a direct effect is lacking. To assess the effects of MSCs on survival after lethal irradiation, we infused syngeneic MSCs (either as immortalized MSCs clones or primary MSCs) intravenously into wild-type C57/Bl6 mice within 24 hours of lethal total body irradiation (TBI). Mice receiving either of the MSC preparations had significantly improved survival when compared to controls. In vivo imaging, immune histochemistry, and RT-PCR employed to detect MSCs indicated that the infused MSCs were predominantly localized to the lungs and rapidly cleared following infusion. Our results suggest that a single infusion of MSCs can improve survival after otherwise lethal TBI but the effect is not due to a direct interaction with, or contribution to, the damaged marrow by MSCs