Staircase resiliency in a fluctuating cellular array.

Inhomogeneous mixing by stationary convective cells set in a fixed array is a particularly simple route to layering. Layered profile structures, or staircases, have been observed in many systems, including drift-wave turbulence in magnetic confinement devices. The simplest type of staircase occurs in passive-scalar advection, due to the existence and interplay of two disparate timescales, the cell turn-over (τ_{H}), and the cell diffusion (τ_{D}) time. In this simple system, we study the resiliency of the staircase structure in the presence of global transverse shear and weak vortex scattering. The fixed cellular array is then generalized to a fluctuating vortex array in a series of numerical experiments. The focus is on regimes of low-modest effective Reynolds numbers, as found in magnetic fusion devices. By systematically perturbing the elements of the vortex array, we learn that staircases form and are resilient (although steps become less regular, due to cell mergers) over a broad range of Reynolds numbers. The criteria for resiliency are (a) τ_{D}≫τ_{H} and (b) a sufficiently high profile curvature (κ≥1.5). We learn that scalar concentration travels along regions of shear, thus staircase barriers form first, and scalar concentration "homogenizes" in vortices later. The scattering of vortices induces a lower effective speed of scalar concentration front propagation. The paths are those of the least time. We observe that if background diffusion is kept fixed, the cell geometric properties can be used to derive an approximation for the effective diffusivity of the scalar. The effective diffusivity of the fluctuating vortex array does not deviate significantly from that of the fixed cellular array.

Selective use of drains in thyroid surgery.

OBJECTIVE: To identify whether there are differences in the use of drains and, if used, which would be the best for thyroid surgery. DESIGN: Prospective, longitudinal, comparative, randomized study. SETTING: General Hospital Mexico City, Mexico. PATIENTS AND METHODS: One hundred fifty patients were studied, divided into three groups: group A, without drain; group B, with a Penrose drain; and group C, with a semirigid suction drain. On the basis of the preoperative diagnosis, subtotal or total thyroidectomy or hemithyroidectomy was performed. Analyzed variables were thyroid volume (TV), transoperative bleeding (TOB), flow of postoperative drain (PD), length of hospital stay (HS), and complications, such as seromas, hematomas, and hemorrhages. Statistical Analysis. Multiple variant analysis, using Scheffe's procedure and chi2. RESULTS: Group A had an average TOB of 107 mL, HS of 2 days, and TV of 153.24 mL with two complications (seromas). Group B had an average TOB of 149.8 mL, HS of 2.6 days, TV of 175.4 mL, PD of 29.6 mL, and three complications (2 seromas and 1 hematoma). Group C had an average TOB of 161.5 mL, HS of 3.11 days, TV of 173.5 mL, PD of 25.84 mL, and two seromas. No differences existed regardless of the type of drain used between groups B and C. CONCLUSION: Statistical analysis showed that the size of the gland, diagnosis, type of surgery, transoperative bleeding, and complications are not valid arguments to leave an external drain in thyroid surgery. No advantages were found between the Penrose or the semirigid suction drains. Hospital stay was longer in patients with the suction drain. These results support the notion that the use of wound drainage cannot substitute for meticulous dissection and transoperative hemostasis.

[Clinical behavior of thyroid papillary cancer in pregnancy: optimal time for its treatment]. / Comportamiento clínico del cáncer papilar de tiroides durante el embarazo: momento óptimo para su tratamiento.

OBJECTIVE: To analyze the clinical characteristic and evolution of papillary thyroid cancer with pregnancy and know the optimal time to treatment. MATERIAL AND METHODS: Cohort analytic study with two groups: One with 6 papillary cancer and pregnancy and group 2 with 24 papillary cancer and the same age, prognostic score AMES and MACIS, treatment, time of follow up and mortality. The variables analyzed was clinical presentation, local, regional, distant recurrence, and mortality. The statistical analyzed by Chi Square and t test. RESULTS: There were no statistical differentiation between the two groups in age, prognostic score, rates of recurrence and mortality with a time of follow up for G1 83 (33 to 240) months and 88 (12 to 288) months for G2. There were differences only in clinical presentation with positive cervical nodes in 100% of patients in G1 vs. 12.5% in G2. This condition does not alter the final evolution. CONCLUSION: A pregnant patient with papillary thyroid cancer can wait the end of the pregnancy and then receive the appropriated cancer treatment.

Trilineage phenotypic compromise in acute leukemia.

The expression of three lineage specific antigens in the leukemic blasts is extremely infrequent. We here report a case of triphenotypic acute leukemia with involvement of the myeloid and B and T lineages. The morphology of the blasts showed promyelocytic features with agranular cytoplasm, suggesting a M3-variant of AML. The blasts were positive for myeloperoxidase PAS and Sudan Black. Immunophenotype and cytogenetics did not confirm M3-AML diagnosis, showing a trilineage compromise (myeloid and T and B lymphoid markers) and the cytogenetic alterations +8 and +11, respectively. This report highlights the importance of correlating the results of multiple diagnostic methods in order to establish a correct diagnosis of mixed lineage acute leukemias, and allows evaluation of the prognostic importance of this subgroup of patients.