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Photoconductive antennas (PCAs) are among the most conventional devices used for emission as well as detection of terahertz (THz) radiation. However, due to their low optical-to-THz conversion efficiencies, applications of these devices in out-of-laboratory conditions are limited. In this paper, we report several factors of enhancement in THz emission efficiency from conventional PCAs by coating a nano-layer of dielectric (TiO2) on the active area between the electrodes of a semi-insulating GaAs-based device. Extensive experiments were done to show the effect of thicknesses of the TiO2layer on the THz power enhancement with different applied optical power and bias voltages. Multiphysics simulations were performed to elucidate the under-lying physics behind the enhancement of efficiency of the PCA. Additionally, this layer increases the robustness of the electrode gaps of the PCAs with high electrical insulation as well as protect it from external dust particles.

Let $G$ be a graph(directed or undirected) having $k$ number of blocks. A $\mathcal{B}$-partition of $G$ is a partition into $k$ vertex-disjoint subgraph $(\hat{B_1},\hat{B_1},\hdots,\hat{B_k})$ such that $\hat{B}_i$ is induced subgraph of $B_i$ for $i=1,2,\hdots,k.$ The terms $\prod_{i=1}^{k}\det(\hat{B}_i),\ \prod_{i=1}^{k}\text{per}(\hat{B}_i)$ are det-summands and per-summands, respectively, corresponding to the $\mathcal{B}$-partition. The determinant and permanent of a graph having no loops on its cut-vertices is equal to summation of det-summands and per-summands, respectively, corresponding to all possible $\mathcal{B}$-partitions. Thus, in this paper we calculate determinant and permanent of some graphs, which include block graph with negatives cliques, signed unicyclic graph, mix complete graph, negative mix complete graph, and star mix block graphs.

There is a digraph corresponding to every square matrix over $\mathbb{C}$. We generate a recurrence relation using the Laplace expansion to calculate the characteristic, and permanent polynomials of a square matrix. Solving this recurrence relation, we found that the characteristic, and permanent polynomials can be calculated in terms of characteristic, and permanent polynomials of some specific induced subdigraphs of blocks in the digraph, respectively. Interestingly, these induced subdigraphs are vertex-disjoint and they partition the digraph. Similar to the characteristic, and permanent polynomials; the determinant, and permanent can also be calculated. Therefore, this article provides a combinatorial meaning of these useful quantities of the matrix theory. We conclude this article with a number of open problems which may be attempted for further research in this direction.

The walk distances in graphs are defined as the result of appropriate transformations of the $\sum_{k=0}^\infty(tA)^k$ proximity measures, where $A$ is the weighted adjacency matrix of a connected weighted graph and $t$ is a sufficiently small positive parameter. The walk distances are graph-geodetic, moreover, they converge to the shortest path distance and to the so-called long walk distance as the parameter $t$ approaches its limiting values. In this paper, simple expressions for the long walk distance are obtained. They involve the generalized inverse, minors, and inverses of submatrices of the symmetric irreducible singular M-matrix ${\cal L}=\rho I-A,$ where $\rho$ is the Perron root of $A.$, Comment: 7 pages. Accepted for publication in Linear Algebra and Its Applications

We consider the two-person zero-sum game in which the strategy sets for Players I and II consist of the vertices and the edges of a directed graph respectively.If Player I chooses vertex v and Player II chooses edge e; then the payoff is zero if v and e are not incident and otherwise it is 1 or _1 according as e originates or terminates at v: We obtain an explicit expression for the value of this game and describe the structure of optimal strategies.A similar problem is considered for undirected graphs and it is shown to be related to the theory of 2-matchings in graphs.

Stress is known to depress the immune system severely. This study was done to evaluate whether surgical stress influenced polymorphonuclear (PMN) and monocyte functions in association with serum cortisol and the anxiety score as measured on the HARS Rating Scale. We found that surgery (irrespective of whether it was major or minor) significantly depressed PMN and monocyte functions and increased serum cortisol levels. PMN phagocytosis correlated significantly (p < 0.05) with the rise in serum cortisol. In spite of these changes, postoperative clinical recovery was uneventful. No major alterations in the HARS scores were noted pre and post operatively. This study demonstrates that surgical stress depresses the immune system with a concomitant rise in cortisol.

A lymphangioma of the chest wall, hitherto unreported is described here.

Thyroid abscess arising from Acute Suppurative Thyroiditis (AST) is a rare clinical disorder. The ability of the thyroid gland to resist infection is well known and infection in the thyroid gland is rare, particularly so with the advent of widespread usage of antibiotics. An internal pharyngeal fistula (Pyriform sinus fistula) is the most common underlying abnormality in patients with AST. We report a case of an adult male who presented with a thyroid abscess. The causal organism was found to be Staphylococcus aureus. Intravenous antibiotics and, incision and drainage of the abscess led to an uncomplicated recovery.

The entity of nonspecific granulomatous inflammatory lesions(NSGIL) of the small bowel is a diagnostic and therapeutic dilemma. Data of 52 histopathologically proven cases of NSGIL seen by us between 1986 and 1991 were analysed. All these patients presented with either intestinal obstruction or perforation. They were thoroughly evaluated and investigated for tuberculosis. Of the 52 patients, 6 patients received antitubercular therapy (ATT) before and after surgery and 32 patients only after surgery. Fourteen patients did not receive ATT. Surgical procedures undertaken included stricturoplasty, resection/anastomosis and simple suturing of perforation. No complications were seen in patients who received ATT; however, six of 14 patients who did not receive ATT developed wound sepsis and 2 developed partial wound dehiscence. Many of these NSGIL lesions could be tuberculous in etiology though typical caseating granulomas were not seen.

A sixty year old female referred for thyroid and liver scintigraphy had a clinical history of progressive swelling in the neck with hepatomegaly. A large cold area was detected in the right thyroid lobe using 99mTc pertechnetate and in the right lobe of liver using 99mTc phytate. Subsequent whole body scan with 99mTC DMSA(V) showed avid tracer uptake in right lobe of thyroid and liver. Aspiration cytology of thyroid and liver showed medullary carcinoma of thyroid with its metastasis in liver. Histopathology following thyroidectomy confirmed the diagnosis. Thus 99mTc pentavalent DMSA contributes specificity to diagnose medullary carcinoma of thyroid and metastatic lesions.

Data on 105 solitary thyroid nodules, confirmed at surgery to be solitary, is presented. Six (5.7%) were malignant, 4 papillary and 2 follicular. The sensitivity and the specificity of 131I radionuclide thyroid scan (n = 90) were 100% and 24% respectively. Similarly, the sensitivity and specificity of fine needle aspiration cytology (n = 65) was 75% and 100% respectively. In both instances, the "gold standard" was the histopathology of the surgically removed nodule. In order to avoid unnecessary surgery, without missing malignancy, we would recommend the combination of radionuclide thyroid scan and FNAC for investigation of solitary thyroid nodules.