The Promise of Citywide Charter Strategies

Charter school enrollment is on the rise in many urban areas. In fact, 56% of all public charter schools are located in urban areas, and 10 of our nation's largest school districts now have 20,000 students enrolled in public charter schools. With this growth in the charter movement, there is an increasing need for local infrastructure support through technical services, advocacy, and coordination. This report examines the potential for citywide charter strategies as a key leverage point for increasing charter school quality

The microstructure of meteoric ice from Vostok, Antarctica

The 3623 m long, 5G core collected at Vostok station, Antarctica, contains alternating layers of meteoric ice with two distinctly different microstructures. In this paper, we present the microstructure and impurity content of a number of specimens ranging in depth from 97 to 3416 m, describe in detail the characteristics of the different layers and propose a mechanism for their microstructural development. Digital image analysis, ion chromatography, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to measure texture and the location and type of impurities; electron backscatter diffraction was used to determine crystal orientation. The ice associated with interglacial periods is characterized by relatively coarse grains and a strong preferred orientation of the c axes in a plane encompassing the coring direction, producing a vertical-girdle fabric. In contrast, ice from glacial periods is characterized by a much smaller grain size and a strong single-maximum fabric, where the c axes are clustered around the vertical. Calcium is uniquely present in the grain boundaries of the fine-grained glacial layers, and its effect on grain-boundary mobility and the misorientation dependence of mobility can explain the development of the discontinuous microstructure seen in glacial ice at Vostok station

Data Structure for Supporting In-Memory Storage with Multiple Keys

The Object data structure in JavaScript is simply a set of key-value pairs in which the values for each key must be one of the primitive data types. Developers can add multiple value fields for a given key within a JavaScript Object by using an array as the value. Developers can also use an array as a key and retrieve any value via the array. However, developers must query Objects with whole matching key values which prevents execution of queries with partial or multi-key matching. Overcoming these limitations by storing data in a client-side database on the local disk of a user device is an asynchronous, high latency, and potentially risky operation. This disclosure describes a higher-level data structure called InMemoryStorage that can be used to store data with multiple keys in memory. The values for the keys within the InMemoryStorage data structure can be JavaScript objects, each of which can store its own key-value pairs as usual. Developers can retrieve data from the InMemoryStorage data structure by formulating queries based on keys within the objects stored within it. The techniques can be used for any application that requires synchronous, in-memory, client-side storage and access of data with more than one key, such as batching logs in memory prior to transmitting them to remote persistent storage. The techniques extend JavaScript by adding support for partial and multi-key matching

Prevalence of microplastics in the marine environment of Qatar's exclusive economic zone

Microplastics are now firmly recognized as a ubiquitous and growing global threat to marine biota, as well as their associated ecology and habitats. The prevalence of microplastics in the marine waters within Qatar’s Exclusive Economic Zone (EEZ) was investigated. Following sample extraction, microplastics were characterized using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy, and the polymer type then verified using OMNIC Spectra Library. Synthetic polymer microplastics were identified in seawater sampled from ten out of twelve marine monitoring stations, with varying shapes and sizes. Granular shaped microplastics present ranged from 120µm to 1.2mm in size, and fibrous microplastic ranged from 150µm to 10mm. Polypropylene (PP), low density polyethylene (LDPE), polyethylene (PE), polystyrene (PS), polyamide (PA), acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA) and cellophane microplastic particles were identified. Copolymers were also identified from the collected samples, including poly(styrene:vinylidene chloride), poly(ethylene:propylene:diene) and alkyd resin e.g. paint debris. The most numerous type of synthetic polymer microplastic identified was polypropylene, with the greatest concentration found near Halul Island in the north east of the Qatar EEZ, where nearby anthropogenic activities include oil-rig installations and shipping operations. In addition, as par to the investigation, an optimized method was also developed for the extraction of microplastics from seawater samples rich in phytoplankton. The use of 1M NaOH proved to be more efficient digestion treatment than 10M NaOH and 22.5M HNO3 solutions, as the latter two solutions resulted in structural damage and discoloration of the reference polymers: polyvinyl alcohol (PVA), polyvinyl chloride (PVC), polystyrene (PS), polyethylene (PE), and nylon

A scanning electron microscope technique for identifying the mineralogy of dust in ice cores

Dust particles in an ice core from East Rongbuk Glacier on the northern slope of Qomolangma (Mount Everest; 28deg 01\u27 N, 58deg 00\u27 E; 6518m a.s.l.), central Himalaya, have been identified as mica using a combination of scanning electron microscope-based techniques and energy-dispersive X-ray spectroscopy to identify the elements present, and electron backscatter diffraction to identify the crystal type. This technique for identifying individual crystalline dust particles in samples of glacial ice could be especially useful in the future for identifying water-soluble crystals in ice, for studying the strain history (glaciotectonics) of basal ice or in studies of icemica composites used as analogs of quartz-mica rocks