Ruolo del tempo di contatto del bolo e dei valori di impedenza basale nella distinzione di differenti sottocategorie di pazienti con malattia da reflusso gastroesofageo non erosiva.

Background Nella malattia da reflusso gastro-esofageo (Gastroesophageal Reflux Disease - GERD), le anormalità della clearance del bolo esofageo sottolineano l’importanza di un’alterata funzione esofagea. Attualmente non sono disponibili dati relativi al ruolo del tempo di contatto del bolo (Bolus Contact Time - BCT) in pazienti con GERD non erosiva (Non Erosive Reflux Disease - NERD). Scopo dello Studio Scopo di tale studio è stato il confronto del BCT e dei livelli di impedenza basale (Baseline Impedance - BI) in pazienti con sintomi da reflusso tipici e caratteristiche fisiopatologiche tipiche della NERD, suddivisi in tre gruppi sulla base dei valori del tempo di esposizione acida (Acid Exposure Time - AET) e del numero degli episodi di reflusso rilevati con pH-Impedenziometria delle 24 ore (24-h impedance-pH Monitoring – MII-pH). Tali risultati sono inoltre stati confrontati con un gruppo di pazienti con sintomi da reflusso tipici e MII-pH negativa. Materiali e Metodi Centodiciassette pazienti consecutivi con pirosi e/o rigurgito ed esofago-gastro-duodenoscopia negativa sono stati sottoposti a MII-pH, previa sospensione di eventuale terapia con inibitori di pompa protonica. Per ogni paziente sono state raccolte le seguenti informazioni: caratteristiche demografiche (età, sesso, BMI); sintomatologia; AET; numero degli episodi di reflusso indentificati mediante MII; BI a livello del canale 3, valutata durante il riposo notturno in tre differenti momenti; BCT rilevato ai canali 3 e 5 per ogni episodio di reflusso indentificato con la MII. I pazienti con NERD, AET e/o episodi di reflusso nei limiti sono stati arruolati e suddivisi in tre sottogruppi come segue: AET+/MII+ (alterati valori sia di AET che del numero di reflussi); AET+/MII- (alterato AET e normale numero di reflussi); AET-/MII+ (AET normale e alterato numero di reflussi). I pazienti con AET e numero di reflussi nei limiti della norma (AET-/MII-) sono stati selezionati come controlli. Risultati I pazienti AET+/MII+ hanno mostrato valori medi più elevati di AET, BI e BCT rispetto a tutti gli altri gruppi (p<0,001). Il numero dei reflussi è risultato più elevato nei soggetti AET+/MII+ e AET-/MII+ rispetto ai soggetti AET+/MII- e AET-/MII- (rispettivamente 79±26,7 e 70,2±15,6 vs 36,3±9,1 e 24,3±9,6; p=0,001). Il valore di BI (a 3 cm) ha mostrato una progressiva riduzione dai pazienti con AET+/MII+, AET+/MII-, AET-/MII+ fino a quelli con AET-/MII- (1144,5±422,1 vs 1580,5±861,5 vs 1723,3±434,4 vs 3652,5±888,4; p<0,001). Il valore di BCT medio (3 e 5 cm) è risultato più elevato nei pazienti con AET+/MII- e con AET-/MII+ rispetto a quelli con AET-/MII- sia a 3 cm (29,7±4,4 vs 23,6±11 vs 14,5±2,3; p<0,001) che a 5 cm (25±4,5 vs 19,1±11,2 vs 11±2,7; p<0,001). Parametri MII-pH nei differenti sottogruppi di pazienti AET+/MII+ (31) AET+/MII- (28) AET-/MII+ (34) AET-/MII- (24) P value M:F 18:13 11:17 18:16 6:18 0,03 Età media (ds) 56,1±12 54,5±11,5 45,3±14,7 48,8±11,5 0,64 Reflussi Prossimali (ds 42,6±26,7 14,3±8 29,7±12 9,3±4,8 0,001 BI 3 cm (ds) 1144,5±422,1 1580,5±861,5 1723,3±434,4 3652,5±888,4 0,001 BCT 3 cm (ds) 46,5±18,3 29,7±4,4 23,6±11 14,5±2,3 0,001 BCT 5 cm (ds) 38,8±15,3 25±4,5 19,1±11,2 11±2,7 0,001 AET – Acid Exposure Time; BCT – Bolus Contact Time; BI - Basal Impedance; MII – Impedence Monitoring. Conclusioni Tali risultati dimostrano come sia il valore di BI che il BCT (a 3 e 5 cm) potrebbero aiutare nella distinzione di differenti sottocategorie di pazienti con NERD

A general solution to the Schr\"odinger-Poission equation for charged hard wall: Application to potential profile of an AlN/GaN barrier structure

A general, system-independent formulation of the parabolic Schr\"odinger-Poisson equation is presented for a charged hard wall in the limit of complete screening by the ground state. It is solved numerically using iteration and asymptotic-boundary conditions. The solution gives a simple relation between the band bending and charge density at an interface. I further develop approximative analytical forms for the potential and wave function, based on properties of the exact solution. Specific tests of the validity of the assumptions leading to the general solution are made. The assumption of complete screening by the ground state is found be a limitation; however, the general solution still provides a fair approximate account of the potential when the bulk is doped. The general solution is further used in a simple model for the potential profile of an AlN/GaN barrier, and gives an approximation which compares well with the solution of the full Schr\"odinger-Poisson equation

Interdisciplinary Decisions Application in Management, or How to Use the Experience of Workload Management of Technological System with Regard to Human Resources

To a modern executive officer enterprise management means challenging requirements in search of unconventional solutions in system administration organization. A whole spectrum of solutions is found when you use knowledge, traditions and managerial decisions existing in other spheres. This article contemplates concepts and philosophy that consider the problem from the other point of view and find new or specialized decisions from related areas. A comparison between workload management in technological system and human resources is used as an example. Based on this comparison implications are made about certain compatibility of these systems and possible adaptation of the existing management methods. At the end we come to the conclusion of benefit from using intersectorial and cross-cultural experience

Investigation of flow parameters in a cylindrical pebble bed and in a model of a fuel assembly with microfuels

The results of an experimental study of the hydrodynamics and heat transfer of a pebble bed in a cylindrical channel and in a model of a fuel assembly with microfuels (FA MT) with a cross flow of a coolant are presented. Data on the temperature distribution along the height and the pebble radius for volumetric heat release, as well as data on pressure losses over a wide range of mass flow rates of the coolant from 0.05 to 1.75 kg/s are obtained

Anomalous magnetotransport and cyclotron resonance of high mobility magnetic 2DHGs in the quantum Hall regime

Low temperature magnetotransport measurements and far infrared transmission spectroscopy are reported in molecular beam epitaxial grown two-dimensional hole systems confined in strained InAs quantum wells with magnetic impurities in the channel. The interactions of the free holes spin with the magnetic moment of 5/2 provided by manganese features intriguing localization phenomena and anomalies in the Hall and the quantum Hall resistance. In magnetic field dependent far infrared spectroscopy measurements well pronounced cyclotron resonance and an additional resonance are found that indicates an anticrossing with the cyclotron resonance

Theory of Ferromagnetism in Diluted Magnetic Semiconductor Quantum Wells

We present a mean field theory of ferromagnetism in diluted magnetic semiconductor quantum wells. When subband mixing due to exchange interactions between quantum well free carriers and magnetic impurities is neglected, analytic result can be obtained for the dependence of the critical temperature and the spontaneous magnetization on the distribution of magnetic impurities and the quantum well width. The validity of this approximate theory has been tested by comparing its predictions with those from numerical self-consistent field calculations. Interactions among free carriers, accounted for using the local-spin-density approximation, substantially enhance the critical temperature. We demonstrate that an external bias potential can tune the critical temperature through a wide range.Comment: 4 pages, 3 figures, submitted to Phys. Rev.

Stability of trions in strongly spin-polarized two-dimensional electron gases

Low-temperature magneto-photoluminescence studies of negatively charged excitons (X- trions) are reported for n-type modulation-doped ZnSe/Zn(Cd,Mn)Se quantum wells over a wide range of Fermi energy and spin-splitting. The magnetic composition is chosen such that these magnetic two-dimensional electron gases (2DEGs) are highly spin-polarized even at low magnetic fields, throughout the entire range of electron densities studied (5e10 to 6.5e11 cm^-2). This spin polarization has a pronounced effect on the formation and energy of X-, with the striking result that the trion ionization energy (the energy separating X- from the neutral exciton) follows the temperature- and magnetic field-tunable Fermi energy. The large Zeeman energy destabilizes X- at the nu=1 quantum limit, beyond which a new PL peak appears and persists to 60 Tesla, suggesting the formation of spin-triplet charged excitons.Comment: 5 pages (RevTex), 4 embedded EPS figs. Submitted to PRB-R

Landau Level Crossings and Extended-State Mapping in Magnetic Two-dimensional Electron Gases

We present longitudinal and Hall magneto-resistance measurements of a ``magnetic'' two-dimensional electron gas (2DEG) formed in modulation-doped Zn$_{1-x-y}$Cd$_{x}$Mn$_{y}$Se quantum wells. The electron spin splitting is temperature and magnetic field dependent, resulting in striking features as Landau levels of opposite spin cross near the Fermi level. Magnetization measurements on the same sample probe the total density of states and Fermi energy, allowing us to fit the transport data using a model involving extended states centered at each Landau level and two-channel conduction for spin-up and spin-down electrons. A mapping of the extended states over the whole quantum Hall effect regime shows no floating of extended states as Landau levels cross near the Fermi level.Comment: 10 pages, 4 figures, submitted to Phys. Rev.