Piecewise-linear programming: The compact (CPLP) algorithm

A compact algorithm is presented for solving the convex piecewise-linear-programming problem, formulated by means of a separable convex piecewise-linear objective function (to be minimized) and a set of linear constraints. This algorithm consists of a finite sequence of cycles, derived from the simplex method, characteritic of linear programming, and the line search, characteristic of nonlinear programming. Both the required storage and amount of calculation are reduced with respect to the usual approach, based on a linear-programming formulation with an expanded tableau. The tableau dimensions arem×(n+1), wherem is the number of constraints andn the number of the (original) structural variables, and they do not increase with the number of breakpoints of the piecewise-linear terms constituting the objective function.     

Stability of shock waves for the Broadwell equations

For the Broadwell model of the nonlinear Boltzmann equation, there are shock profile solutions, i.e. smooth traveling waves that connect two equilibrium states. For weak shock waves, we prove asymptotic (in time) stability with respect to small perturbations of the initial data. Following the work of Liu [7] on shock wave stability for viscous conservation laws, the method consists of analyzing the solution as the sum of a shock wave, a diffusive wave, a linear hyperbolic wave and an error term. The diffusive and linear hyperbolic waves are approximate solutions of the fluid dynamic equations corresponding to the Broadwell model. The error term is estimated using a variation of the energy estimates of Kawashima and Matsumura [6] and the characteristic energy method of Liu [7].Research supported by the Office of Naval Research through grant N00014-81-0002 and by the National Science Foundation through grant NSF-MCS-83-01260Research supported by the National Science Foundation through grant DMS-84-01355     

Kinetic model for a step edge in epitaxial growth

A kinetic theory is formulated for the velocity of a step edge in epitaxial growth. The formulation involves kinetic, mean-field equations for the density of kinks and "edge adatoms" along the step edge. Equilibrium and kinetic steady states, corresponding to zero and nonzero deposition flux, respectively, are derived for a periodic sequence of step edges. The theoretical results are compared to results from kinetic Monte Carlo (KMC) simulations of a simple solid-on-solid model, and excellent agreement is obtained. This theory provides a starting point for modeling the growth of two-dimensional islands in molecular-beam epitaxy through motion of their boundaries, as an alternative to KMC simulations.     

Association of Systemic Steroid Treatment and Outcome in Patients Treated with Immune Checkpoint Inhibitors: A Real-World Analysis

Background: Immune-related adverse events (irAEs) are inflammatory side effects, which can occur during immune-checkpoint(s) inhibitors (ICIs) therapy. Steroids are the first-line agents to manage irAEs because of their immunosuppressive properties. However, it is still debated whether or when steroids can be administered without abrogating the therapeutic efforts of immunotherapy. Methods: We retrospectively evaluated 146 patients with metastatic non-small cell lung cancer (NSCLC), melanoma and renal cell carcinoma (RCC) treated with ICIs. We assessed the progression-free survival (PFS) of patients treated with steroids due to an irAE compared to a no-steroid group. Results: The early treatment with steroid (within the first 30 days from the beginning of immunotherapy) was not related to a shorter PFS (p = 0.077). Interestingly, patients who were treated with steroids after 30 days from the start of immunotherapy had significantly longer PFS (p = 0.017). In a multivariate analysis, treatment with steroids after 30 days was an independent prognostic factor for PFS (HR: 0.59 [95% CI 0.36–0.97], p = 0.037). Conclusions: This retrospective study points out that early systemic steroids administration to manage irAEs might not have a detrimental effect on patient clinical outcome in NSCLC, melanoma and RCC patients.     

A novel total reflection X-ray fluorescence procedure for the direct determination of trace elements in petrochemical products

A total reflection X-ray fluorescence (TXRF) procedure was developed for the determination of metal traces in petrochemical end products or intermediates for surfactant synthesis. The method combines a fast and straightforward sample preparation, i.e. deposition on the sample holder and evaporation of the sample matrix, with an efficient quantification method based on internal standardization (organic gallium standard). The method developed showed detection limits below 0.05 μg g^-1 and in most cases below 0.005 μg g^-1. Fifteen elements (Ca, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Rh, Sn, Sr, V and Zn) were determined in matrices such as paraffins, n-olefins, linear alkylbenzenes, long-chain alkyl alcohols and esters: typical metal contents were below 1 μg g^-1. The results were compared with the reference method ASTM D5708 (test method B) based on inductively coupled plasma optical emission spectroscopy: advantages and drawbacks of the two procedures were critically evaluated. The TXRF method developed showed comparable precision and absence of bias with respect to the reference method. A comparison of the performances of the two methods is presented.     

Solid state synthesis of CuFe2O4 from Cu(OH)2?·?CuCO3–4FeC2O4?·?2H2O mixtures: mechanism of reaction and thermal characterization of CuFe2O4

Copper Ferrite has been prepared by solid state synthesis of milled mixtures of copper basic carbonate [Cu(OH)₂ · CuCO₃] and iron (II) oxalate dihydrate [FeC₂O₄ · 2H₂O]. The reaction mechanism has been studied by simultaneous TG/DSC analysis: the different steps of the mass loss process have been individuated along with the relevant enthalpy terms starting from both physical and mechanically activated mixtures. CuFe₂O₄ has been synthesized by annealing the mechanically activated mixture at 750–800 °C while no pure CuFe₂O₄ is obtained by annealing the physical mixture at temperatures as high as 1100 °C. CuFe₂O₄ has been characterized as concerns the molar het capacity, the tetragonal–cubic transition enthalpy and the Curie point.     

Amyloid fibril polymorphism is under kinetic control

Self-assembly of proteins into amyloid aggregates displays a broad diversity of morphologies, both at the protofibrillar and final fibrillar species. These polymorphic species can coexist at fixed experimental conditions, and their relative abundance can be controlled by changing the solvent composition, or stirring the solution. However, the extent to which external conditions regulate the equilibrium of morphologically distinct species is still unknown. Here we investigate the nucleation of distinct fibril morphologies using computer simulations of a simplified model of an amyloid polypeptide. Counterintuitively, the energetically less favorable fibril morphologies nucleate more frequently than the morphologies of higher stability for models with low aggregation propensity. The free-energy profiles of the aggregation process indicate that the nucleation barrier determines the population fractions of different fibril morphologies, i.e., amyloid polymorphism is under kinetic control.     

One‐Pot Synthesis of Highly Emissive Dipyridinium Dihydrohelicenes

Condensation of a pyridyl‐2‐carbaldehyde derivative with 2‐(bromoethyl)amine hydrobromide gave tetracyclic pyrido[1,2‐a]pyrido[1′,2′:3,4]imidazo‐[2,1‐c]‐6,7‐dihydropyrazinium dications in excellent yields. Crystal structures and NOE data demonstrated the helical character of the dications, the dihedral angles between the two pyrido groups ranging from 28–45°. An intermediate in the synthesis was also characterized. A much brighter emission compared to literature helicenes has been found, with quantum yields as high as 60 % in the range of λ=460–600 nm. Preliminary cytotoxicity studies against HT‐29 cancer cells demonstrated moderate‐to‐good activity, with IC₅₀ values 12–30× that of cisplatin.     

Simple Direct Synthesis of New 1-Heterocyclamino-3-Carbonylaminopyrroles by Reaction of Heterocyclic Azoalkenes with β-Ketoamides

Pyrrole and several its derivatives have been subjected to extensive chemical investigations, while substituted 1-aminopyrroles remain a class of compounds about which relatively little is known due to the far from trivial problem sposed by their syntheis. In fact, 1-aminopyrroles appear to be prepared mainly by direct reactionfrom conjugated azoalkenes,2 that unfortunately represent a class of relatively little