Report on a Periodic Extrinsic Infrared (PEIR) Photoconductor

An infrared photoconductor, designated as the Periodic Extrinsic InfraRed (PEIR) photoconductor, is proposed. A PEIR photoconductor will be useful for detecting wavelengths from 7 μm (1400 cm-1) to longer than 100 μm (100 cm-1). Through epitaxial growth, a PEIR photoconductor is made up of heavily doped layers separated by lightly doped layers. The heavily doped layers are doped such that an impurity band forms but are not doped high enough to cause the impurity band to merge with the conduction or valence band. The lightly doped layers are used to confine the carriers in the impurity bands and consequently, conduction can only occur due to carriers excited to the conduction (n-type device) or valence (p-type device) band. Radiation excites the carriers from the impurity band to the conduction or valence band. The impurity band layers are thin enough that even if the electric field in the impurity band layers is small, there is a high probability the excited carrier will scatter into the lightly doped layer and be swept away by the electric field in the lightly doped layer, A PEIR photoconductor will have two major advantages. First, the absorption coefficient will be high because of the high impurity concentration in the impurity band layers. The absorption coefficient will be from 103cm-1 to as high as 104cm-1. Additionally, a method has been found to approximately determine the highest absorption coefficient attainable in specific host semiconductor:impurity dopant materials systems. Consequently, one can determine the optimum host semiconductor:impurity dopant system to be used in a PEIR photoconductor designed to detect a certain wavelength. Second, some host semiconductors that are being considered are Si and GaAs, which are much easier to work with than HgCdTe (the material of choice for intrinsic photoconductors at wavelengths longer than 7 μm)

Sustainable perspective in public educational institutions restaurants : from foodstuffs purchase to meal offer

Abstract: This study aimed to evaluate aspects of sustainable nutrition in Public Educational Institutions Restaurants (PEIR) in a Brazilian state. Cross-sectional descriptive research was conducted in six PEIR. Purchased foodstuffs for a one-month period were investigated from the perspective of their origin (place of production), processing degree and nutritional profile. The presence of Genetically Modified Organisms (GMO) in packaged foodstuffs was also evaluated. Regarding served meals, a four-week period was evaluated in each PEIR considering the Water Footprint (WF) and the nutrient composition of the lunch meals. Results showed that 31.6% of foodstuffs purchased in the period evaluated were from national origin. Analysis of the processing degree of food purchased showed 64.8% unprocessed or minimally processed foods. However, 60.8% of the foodstuffs purchased in a one-month period presented sodium excess, 46.9% had an excess of saturated fat and 40.1% contained an excess of free sugar. The presence of GMO was observed in 9.2% of packed foods. The meals showed a per capita WF average of 2165.8 liters, an energy supply of 834.6 kcal and 1,289.6 mg of sodium per meal served. Foodstuff purchase and menu planning are essential steps towards achieving sustainable meal production and the results showed that foodstuffs purchased in institutional restaurants during the evaluated period was not in line with the precepts of a healthy and sustainable diet. Studies that assess the impact of meal production on the different dimensions of sustainable nutrition are essential to better understand this complex production process

Hazard's Toll: The Costs of Inaction at the Salton Sea

The objective of this report is to estimate the costs of inaction - defined as the absence of any large-scale revitalization or air quality management project - at the Salton Sea, to provide decision-makers and the general public with information for deciding on a path forward

Breakdown of disordered media by surface loads

We model an interface layer connecting two parts of a solid body by N parallel elastic springs connecting two rigid blocks. We load the system by a shear force acting on the top side. The springs have equal stiffness but are ruptured randomly when the load reaches a critical value. For the considered system, we calculate the shear modulus, G, as a function of the order parameter, \phi, describing the state of damage, and also the ``spalled'' material (burst) size distribution. In particular, we evaluate the relation between the damage parameter and the applied force and explore the behaviour in the vicinity of material breakdown. Using this simple model for material breakdown, we show that damage, caused by applied shear forces, is analogous to a first-order phase transition. The scaling behaviour of G with \phi is explored analytically and numerically, close to \phi=0 and \phi=1 and in the vicinity of \phi_c, when the shear load is close but below the threshold force that causes material breakdown. Our model calculation represents a first approximation of a system subject to wear induced loads.Comment: 15 pages, 7 figure

Multiple impacted third molars with pre-eruptive intracoronal resorption in geriatric patients: Two case reports

Background: Pre-eruptive intracoronal resorption (PEIR) is a rare condition usually detected through an incidental radiographic finding. The etiology and pathogenesis of this phenomenon are not fully understood. Purpose: To describe two cases in which multiple impacted third molars with PEIR defects were identified. Cases: Female patients aged 77 and 82 years, respectively, were presented with dental issues. Radiolucencies in the dental crown areas of the impacted maxillary and mandibular third molars were initially detected on the panoramic radiographs. Cone-beam computed tomography (CBCT) was performed to better evaluate the impacted teeth. The results showed that the intracoronal defects extended through more than two-thirds of the thickness of the coronal dentin. Case Managements: Considering the patients’ age and their asymptomatic status, a conservative approach with radiographic follow-up was considered most appropriate. Four-year follow-up checks revealed that the teeth remained asymptomatic in both patients. Conclusion: This case report confirms that PEIR can affect impacted third molars, even in elderly patients. CBCT images are preferred for diagnosing PEIR defects because this method provides an accurate assessment of internal tooth anatomy. With an accurate diagnosis of asymptomatic PEIR, the lesion can be monitored