Fourth-generation SM imprints in B -> K^*l^+l^- decays with polarized K^*

The implication of the fourth-generation quarks in the B -> K^*l^+l^- (l=mu,tau) decays, when K^* meson is longitudinally or transversely polarized, is presented. In this context, the dependence of the branching ratio with polarized K^* and the helicity fractions (f_{L,T}) of K^* meson are studied. It is observed that the polarized branching ratios as well as helicity fractions are sensitive to the NP parameters, especially when the final state leptons are tauons. Hence the measurements of these observables at LHC can serve as a good tool to investigate the indirect searches of new physics beyond the Standard Model.Comment: 13 pages, 10 figures, V2: some of the graphs are modified according to the new data from recent experiments. arXiv admin note: substantial text overlap with arXiv:1107.569

Hawking Radiation of Dirac Particles in a Variable-mass Kerr Space-time

Hawking effect of Dirac particles in a variable-mass Kerr space-time is investigated by using a method called as the generalized tortoise coordinate transformation. The location and the temperature of the event horizon of the non-stationary Kerr black hole are derived. It is shown that the temperature and the shape of the event horizon depend not only on the time but also on the angle. However, the Fermi-Dirac spectrum displays a residual term which is absent from that of Bose-Einstein distribution.Comment: 12 pages in 12pt Revtex, no figure, to appear in Gen. Rel. Grav. Vol.33, No.7 (2001

Histopathological Features of Whipple Pancreaticoduodenectomy in Sudan: A Single-center Experience

Background: Periampullary tumors (PATs) are rare and Whipple pancreaticoduodenectomy is the commonest surgical approach for its management. The aim of this study was to analyze the histopathological features of Whipple-resected periampullary tumors in Sudanese patients.Methods: This retrospective descriptive study included 62 cases of Whipple resection seen in a center in Khartoum, Sudan from January 2016 to June 2021. The specimens were assessed for nine features of the tumor: site of the tumor (whether within the periampullary region), size of the tumor, histological type of the tumor, grade, perineural invasion, lymph vascular invasion, surgical margin status, lymph node metastasis status, and the pathological stage (pTNM).Results: In total, 62 cases, 40 (64.5%) males and 22 (35.5%) females, were included. Age ranged from 20 to 90 years with a mean age of 56.08 years (±12.98 SD). Of the 62 cases, 58 were malignant (93.5%), while 4 cases were benign (6.5%). The pancreas was the commonest site for malignant tumors (53.4%), followed by the ampulla (24.1%), duodenum (15.5%), and distal common bile duct tumors (DCBD) (7%). The maximum tumor size was 8 cm, and the number of lymph nodes resected ranged from 3 to 33. Pancreatic ductal adenocarcinomas (PDACs) showed the highest percentage of perineural (62.1%) and lymphovascular (55.2%) invasions, and a positive margin was seen in four cases. The most common tumor stage was pT3pN1pMx.Conclusion: PATs in the Sudanese population showed histological diversity regarding subtyping, grading, and staging. Further studies involving molecular prognostic features will support improving patient management. Keywords: periampullary tumors; Whipple pancreaticoduodenectomy; resection; histological features; Suda

Entropy of Rotating Misner String Spacetimes

Using a boundary counterterm prescription motivated by the AdS/CFT conjecture, I evaluate the energy, entropy and angular momentum of the class of Kerr-NUT/bolt-AdS spacetimes. As in the non-rotating case, when the NUT charge is nonzero the entropy is no longer equal to one-quarter of the area due to the presence of the Misner string. When the cosmological constant is also non-zero, the entropy is bounded from above.Comment: Revtex, 9 pages, 3 figure

Pseudo-Hermitian Hamiltonians, indefinite inner product spaces and their symmetries

We extend the definition of generalized parity $P$, charge-conjugation $C$ and time-reversal $T$ operators to nondiagonalizable pseudo-Hermitian Hamiltonians, and we use these generalized operators to describe the full set of symmetries of a pseudo-Hermitian Hamiltonian according to a fourfold classification. In particular we show that $TP$ and $CTP$ are the generators of the antiunitary symmetries; moreover, a necessary and sufficient condition is provided for a pseudo-Hermitian Hamiltonian $H$ to admit a $P$-reflecting symmetry which generates the $P$-pseudounitary and the $P$-pseudoantiunitary symmetries. Finally, a physical example is considered and some hints on the $P$-unitary evolution of a physical system are also given.Comment: 20 page