The hydrogen evolution and oxidation kinetics during overdischarging of sealed nickel-metal hydride batteries

The hydrogen evolution and oxidation kinetics in NiMH batteries have been investigated under temperature-controlled, steady-state, overdischarging conditions within a temperature range of 10 and 50°C and at discharging currents of 1–330 mA (0.0009 to 0.3 C rate). In situ Raman spectroscopic analyses of the gas phase showed that hydrogen is the only gas evolving inside the battery during overdischarge at the above-mentioned conditions. The pressure increase could be very critical at low temperatures, leading to opening of the safety vent at relatively low discharging currents, for example, only 220 mA at 10°C. The polarization parameters for the hydrogen evolution reaction, such as Tafel slopes and exchange currents were determined at the different temperatures as well as the activation energy for the evolution and oxidation processes. The reaction mechanisms and the rate-determining steps are discussed. These are highly valuable information in NiMH modeling as they are obtained directly from the system of interest. Furthermore, the obtained results make battery simulations more realistic by minimizing the number of parameters involved and making the correct assumptions

Photoluminescence properties of Eu2+-activated sialon S-phase BaAlSi5O2N7

Within the scope of the search of potential LED conversion phosphors, the photoluminescence properties of Eu2+-activated BaAlSi5O2N7 sialon S-phase have been investigated. It shows a broad emission band in the wavelength range of 400–650 nm with maxima from 483 to 500 nm with increasing the Eu2+ concentration. This short-wavelength emission of Eu2+ despite nitrogen-rich coordination is attributed to lowering of the crystal field strength as a result of long distance between Eu and (N, O) anions. Due to the very rigid T12X18-4 network, T = (Si, Al) and X = (N, O), in the crystal structure of MAlSi5O2N7 (M = Sr, Ba), it is supposed that each Eu ion will create its own preferred local coordination irrespective of the occupation of the other sites by Ba or Sr ions in the MAlSi5O2N7 host lattice, which results in resembling luminescence properties for Eu2+-doped in BaAlSi5O2N7 and SrAlSi5O2N7

The hydrogen evolution and oxidation kinetics during overdischarging of sealed nickel-metal hydride batteries

The hydrogen evolution and oxidation kinetics in NiMH batteries have been investigated under temperature-controlled, steady-state, overdischarging conditions within a temperature range of 10 and 50°C and at discharging currents of 1–330 mA (0.0009 to 0.3 C rate). In situ Raman spectroscopic analyses of the gas phase showed that hydrogen is the only gas evolving inside the battery during overdischarge at the above-mentioned conditions. The pressure increase could be very critical at low temperatures, leading to opening of the safety vent at relatively low discharging currents, for example, only 220 mA at 10°C. The polarization parameters for the hydrogen evolution reaction, such as Tafel slopes and exchange currents were determined at the different temperatures as well as the activation energy for the evolution and oxidation processes. The reaction mechanisms and the rate-determining steps are discussed. These are highly valuable information in NiMH modeling as they are obtained directly from the system of interest. Furthermore, the obtained results make battery simulations more realistic by minimizing the number of parameters involved and making the correct assumptions

Preparation and photoluminescence properties of Mn2+-activated M2Si5N8 (M = Ca, Sr, Ba) phosphors

Mn2+-doped M2Si5N8 (M=Ca, Sr, Ba) phosphors have been prepared by a solid-state reaction method at high temperature and their photoluminescence properties were investigated. The Mn2+-activated M2Si5N8 phosphors exhibit narrow emission bands in the wavelength range of 500–700 nm with peak center at about 599, 606 and 567 nm for M=Ca, Sr, Ba, respectively, due to the 4T1(4G)¿6A1(6S) transition of Mn2+. The long-wavelength emission of Mn2+ ion in the host of M2Si5N8 is attributed to the effect of a strong crystal-field of Mn2+ in the nitrogen coordination environment. Also it is observed that there exists energy transfer between M2Si5N8 host lattice and activator (Mn2+). The potential applications of these phosphors have been pointed out

Stratified breast cancer follow-up using a partially observable MDP

Frequency and duration of follow-up for patients with breast cancer is still under discussion. Current follow-up consists of annual mammography for the first five years after treatment and does not depend on the personal risk of developing a locoregional recurrence (LRR) or second primary tumor. Aim of this study is to gain insight in how to allocate resources for optimal and personal follow-up. We formulate a discrete-time Partially Observable Markov Decision Process (POMDP) with a finite horizon in which we aim to maximize the total expected number of quality-adjusted life years (QALYs). Transition probabilities were obtained from data from the Netherlands Cancer Registry (NCR). Twice a year the decision is made whether or not a mammography will be performed. Recurrent disease can be detected by both mammography or women themselves (self-detection). The optimal policies were determined for three risk categories based on differentiation of the primary tumor. Our results suggest a slightly more intensive follow-up for patients with a high risk and poorly differentiated tumor, and a less intensive schedule for the other risk groups

Risk-based breast cancer follow-up stratified by age

Although personalization of cancer care is recommended, current follow-up after the curative treatment of breast cancer is consensus-based and not differentiated for base-line risk. Every patient receives annual follow-up for 5 years without taking into account the individual risk of recurrence. The aim of this study was to introduce personalized follow-up schemes by stratifying for age. Using data from the Netherlands Cancer Registry of 37 230 patients with early breast cancer between 2003 and 2006, the risk of recurrence was determined for four age groups (70). Follow-up was modeled with a discrete-time partially observable Markov decision process. The decision to test for recurrences was made two times per year. Recurrences could be detected by mammography as well as by self-detection. For all age groups, it was optimal to have more intensive follow-up around the peak in recurrence risk in the second year after diagnosis. For the first age group (<50) with the highest risk, a slightly more intensive follow-up with one extra visit was proposed compared to the current guideline recommendation. The other age groups were recommended less visits: four for ages 50-59, three for 60-69, and three for ≥70. With this model for risk-based follow-up, clinicians can make informed decisions and focus resources on patients with higher risk, while avoiding unnecessary and potentially harmful follow-up visits for women with very low risks. The model can easily be extended to take into account more risk factors and provide even more personalized follow-up schedules