Construction of asymptotically good low-rate error-correcting codes through pseudo-random graphs

A novel technique, based on the pseudo-random properties of certain graphs known as expanders, is used to obtain novel simple explicit constructions of asymptotically good codes. In one of the constructions, the expanders are used to enhance Justesen codes by replicating, shuffling, and then regrouping the code coordinates. For any fixed (small) rate, and for a sufficiently large alphabet, the codes thus obtained lie above the Zyablov bound. Using these codes as outer codes in a concatenated scheme, a second asymptotic good construction is obtained which applies to small alphabets (say, GF(2)) as well. Although these concatenated codes lie below the Zyablov bound, they are still superior to previously known explicit constructions in the zero-rate neighborhood

Spectroscopy of blue horizontal branch stars in NGC 6656 (M22)

Recent investigations revealed very peculiar properties of blue horizontal branch (HB) stars in \omega Centauri, which show anomalously low surface gravity and mass compared to other clusters and to theoretical models. \omega Centauri, however, is a very unusual object, hosting a complex mix of multiple stellar populations with different metallicity and chemical abundances. We measured the fundamental parameters (temperature, gravity, and surface helium abundance) of a sample of 71 blue HB stars in M22, with the aim of clarifying if the peculiar results found in \omega Cen are unique to this cluster. M22 also hosts multiple sub-populations of stars with a spread in metallicity, analogous to \omega Cen. The stellar parameters were measured on low-resolution spectra fitting the Balmer and helium lines with a grid of synthetic spectra. From these parameters, the mass and reddening were estimated. Our results on the gravities and masses agree well with theoretical expectations, matching the previous measurements in three "normal" clusters. The anomalies found in \omega Cen are not observed among our stars. A mild mass underestimate is found for stars hotter than 14\,000 K, but an exact analogy with \omega Cen cannot be drawn. We measured the reddening in the direction of M22 with two independent methods, finding E(B-V)=0.35 \pm 0.02 mag, with semi-amplitude of the maximum variation \Delta(E(B-V))=0.06 mag, and an rms intrinsic dispersion of \sigma(E(B-V))=0.03 mag.Comment: 11 pages, 9 Postscript figure

A hot horizontal branch star with a close K-type main-sequence companion

Dynamical interactions in binary systems are thought to play a major role in the formation of extreme horizontal branch stars (EHBs) in the Galactic field. However, it is still unclear if the same mechanisms are at work in globular clusters, where EHBs are predominantly single stars. Here we report on the discovery of a unique close binary system (period ~1.61 days) in the globular cluster NGC6752, comprising an EHB and a main-sequence companion of 0.63+-0.05 Msun. Such a system has no counterpart among nearly two hundred known EHB binaries in the Galactic field. Its discovery suggests that either field studies are incomplete, missing this type of systems possibly because of selection effects, or that a particular EHB formation mechanism is active in clusters but not in the field

Identifikasi Miskonsespi Siswa pada Materi Getaran dan Gelombang Kelas VIII di Mtsn Rukoh

This study aims to identify misconceptions in students in class VIII MTSN Rukoh on the concept of vibrations and waves. The study population was a class VIII student MTsN Rukoh Banda Aceh the school year 2016/2017, amounting to 120 students and 28 are designated sample VIIIA class. Determination of sample is purposive sampling. The method used is qualitative descriptive method. The data collection was done by using a diagnostic test which is equipped with a CRI (Certainly of Response Index) and interviews. Processing data using simple statistical calculation in the form of a percentage. The result showed that the average level of Lucky Guess (LG) of 11:24%, Know Concepts (TK) as much as 26.75%, Do not Know Concepts (TTK) as much as 25.17% and Misconceptions (M) as much as 32.67%

Detailed abundances in stars belonging to ultra-faint dwarf spheroidal galaxies

We report preliminary results concerning the detailed chemical composition of metal poor stars belonging to close ultra-faint dwarf galaxies (hereafter UfDSphs). The abundances have been determined thanks to spectra obtained with X-Shooter, a high efficiency spectrograph installed on one of the ESO VLT units. The sample of ultra-faint dwarf spheroidal stars have abundance ratios slightly lower to what is measured in field halo star of the same metallicity.We did not find extreme abundances in our Hercules stars as the one found by Koch for his 2 Hercules stars. The synthesis of the neutron capture elements Ba and Sr seems to originate from the same nucleosynthetic process in operation during the early stages of the galactic evolution.Comment: 3 pages, 1 figure; OMEG11 conference (Tokyo, Nov 2011

Biochar from co-pyrolysis of urban organic wastes : Investigation of carbon sink potential using ATR-FTIR and TGA

Urban organic wastes (UOW) strain the infrastructures for solid waste treatment (SWT) in emerging economies. This study investigated biochar gained from three major UOW sources in India—banana peduncles (BP), a fibrous waste, from fruit markets; sewage sludge (SS) from wastewater treatment plants; and anaerobic digestate (AD) from food and market waste processing facilities—in terms of its potential to sequester and become long-term carbon sink in soils. Herein, the chemical properties (using ATR-FTIR) and thermal oxidative stability (using TGA) of biochars derived from these UOW and their three blends were examined. Biochar from SS and AD and the blends were found to possess more ash content, Cl, and alkali and alkaline earth metals (AAEM) than that from BP. The conventional recalcitrance index (R50) could not quantify and compare the stability of these mineral- and ash-rich biochars. Hence, a modified thermal oxidative recalcitrance index (TORi) is proposed. All the biochar from blends prepared at highest treatment temperature of 650 °C shows similar aromaticity. However, biochar from blend of 50% SS, 30%BP, and 20% AD exhibits the highest recalcitrance (TORi = 0.193) to become a long-term carbon sink in soil. More than aromaticity, the influence of Si, Fe, and AAEM on the biochar matrix affects its recalcitrance. Variations in the structural properties and recalcitrance of biochars from blends are attributable to the synergy among their constituents SS, AD, and BP. The determined TORi confirms the potential of biochar from the blends of UOW as a long-term carbon sink. © 2020, The Author(s)

Biochar production though combined solar drying & single chamber pyrolysis

In this study, the challenging management of fibrous organic wastes (FOW) and dewatered municipal sewage sludge (MSS) in urban areas of Asia’s newly industrialised countries is presented with high energy efficiency, negative CO2 balance and biochar generation. This study investigates the feasibility and benefits of a combined treatment approach for both of the substrates, comprising solar drying (SD) and pyrolysis process (PYR). Based on material investigations, a calculation model is developed to project the material and energy flows of this process combination on the example of Chennai, India. Please click Additional Files below to see the full abstract

Kandungan Klorofil Tumbuhan Dominan Pasca Kebakaran Lahan Gambut dan Pemanfaatannya untuk Rancangan Lkpd Biologi SMA

This study aims to determine the effect of fire incident time on chlorophyll content of dominant plants after peat land fires in Rimba Panjang village, Kampar regency. This study was conducted during the months of February to June 2017 using the servei research design. Samples are the dominant strata sapling plant determined based on Important Value Index (IVI) with sampling using purpose random sampling technique based on gradient time of fires (2009, 2013, 2014, 2015, 2016, 2017). The measurement of chlorophyll content was done on the leaves of the three dominant strata sapling plants using Chlorophyll meter SPAD 502, while the physical chemical aspects of the environment were measured using Lux meter to measure light intensity, Thermo hygrometer to measure temperature and humidity, and Soil tester to measure pH and soil moisture. The measurement results dominant chlorophyll content in plants showed that the longer time after the fire the chlorophyll content tends to increase. In addition to the length of time after the fire, environmental factors also affect the chlorophyll content in plants such as, light intensity, soil pH, soil moisture, air temperature, and air humidity. Research result can be utilized for the design of Student WorkSheet of Biology learning in senior high school