Why Do Computers Depreciate?

The value of installed computers falls rapidly and therefore computers have a very high user cost. The paper provides a complete account of the non-financial user cost of personal computers -- decomposing it into replacement cost change, obsolescence, instantaneous depreciation, and age-related depreciation. The paper uses data on the resale price of computers and a hedonic price index for new computers to achieve this decomposition. Once obsolescence is taken into account, age-related depreciation -- which is often identified as deterioration -- is estimated to be negligible. While the majority of the loss in value of used computers comes from declines in replacement cost, this paper shows the second most important source of decline in value is obsolescence. Obsolescence is accelerated by the decline in replacement cost of computers. Cheaper computing power drives developments in software and networks that make older computers less productive even though their original functionality remains intact.

Epidemiological data of falciparum malaria in Ado-Odo/Ota, Southwest Ogun State, Nigeria

In this data article, Blood and corresponding saliva samples from subjects presenting with fever and parasetaemia Z2000 were obtained from selected hospitals in Ado-Odo/Ota, Ogun State over a period of two years and analyzed using Polymerase chain reaction-Restriction fragment Length Polymorphism (PCR/Nested PCR-RFLP) to detect genetic mutations of Plasmodium falciparum chloroquine resistance transporter (Pfcrt), Plasmodium falciparum multidrugs resistance (Pfmdr1) and non-synonymous Pkelch (pk13) mutated genes. The study confirmed the presence of resistance genes in the blood and saliva samples collected from the study sit

The magnesium isotope record of cave carbonate archives

Here we explore the potential of magnesium (δ<sup>26</sup>Mg) isotope time-series data as continental climate proxies in speleothem calcite archives. For this purpose, a total of six Pleistocene and Holocene stalagmites from caves in Germany, Morocco and Peru and two flowstones from a cave in Austria were investigated. These caves represent the semi-arid to arid (Morocco), the warm-temperate (Germany), the equatorial-humid (Peru) and the cold-humid (Austria) climate zones. Changes in the calcite magnesium isotope signature with time are compared against carbon and oxygen isotope records from these speleothems. Similar to other proxies, the non-trivial interaction of a number of environmental, equilibrium and disequilibrium processes governs the δ<sup>26</sup>Mg fractionation in continental settings. These include the different sources of magnesium isotopes such as rainwater or snow as well as soil and host rock, soil zone biogenic activity, shifts in silicate versus carbonate weathering ratios and residence time of water in the soil and karst zone. Pleistocene stalagmites from Morocco show the lowest mean δ<sup>26</sup>Mg values (GDA: −4.26 ± 0.07‰ and HK3: −4.17 ± 0.15‰), and the data are well explained in terms of changes in aridity over time. The Pleistocene to Holocene stalagmites from Peru show the highest mean value of all stalagmites (NC-A and NC-B δ<sup>26</sup>Mg: −3.96 ± 0.04‰) but only minor variations in Mg-isotope composition, which is consistent with the rather stable equatorial climate at this site. Holocene stalagmites from Germany (AH-1 mean δ<sup>26</sup>Mg: −4.01 ± 0.07‰; BU 4 mean δ<sup>26</sup>Mg: −4.20 ± 0.10‰) suggest changes in outside air temperature was the principal driver rather than rainfall amount. The alpine Pleistocene flowstones from Austria (SPA 52: −3.00 ± 0.73‰; SPA 59: −3.70 ± 0.43‰) are affected by glacial versus interglacial climate change with outside air temperature affecting soil zone activity and weathering balance. Several δ<sup>26</sup>Mg values of the Austrian and two δ<sup>26</sup>Mg values of the German speleothems are shifted to higher values due to sampling in detrital layers (Mg-bearing clay minerals) of the speleothems. The data and their interpretation shown here highlight the potential but also the limitations of the magnesium isotope proxy applied in continental climate research. An obvious potential lies in its sensitivity for even subtle changes in soil-zone parameters, a hitherto rather poorly understood but extremely important component in cave archive research. Limitations are most obvious in the low resolution and high sample amount needed for analysis. Future research should focus on experimental and conceptual aspects including quantitative and well-calibrated leaching and precipitation experiments

Epidemiology of Plasmodium falciparum infection and drug resistance markers in Ota Area, Southwestern Nigeria

Purpose: Effective routine monitoring and surveillance of parasite genes is a necessary strategy in the control of parasites’ resistance to antimalarial drugs, according to the WHO’s recommendation. This cross-sectional study therefore aimed at carrying out an epidemiological analysis on malaria incidence in Ado-Odo/Ota, Ogun State. Patients and methods: Blood and corresponding saliva samples were collected from 1,243 subjects of all ages and sex presenting with fever and a parasitemia level ≥2,000 between September 2016 and March 2018. Samples were collected from selected health facilities in the study area of Ogun state to establish the prevalence of falciparum malaria and determine resistance genes harbored by the parasites. The overall prevalence of falciparum malaria in the study site by microscopic examination was 45.86%. The highest incidence of 57.42% was recorded among male subjects. Point mutations of K76T and N86Y in the Pfcrt and pfmdr-1 genes, as well as non-synonymous mutations in Pfk13 genes, were screened for and sequenced for further analysis. Results: Pfcrt was detectable in 57.42% of blood and 51.02% of saliva samples, respectively. About 34.78% of the subjects that were confirmed microscopically harbored the Pfmdr-1 mutated gene while 26.67% of the saliva samples revealed Pfmdr-1. Epidemiological studies identified the presence of wild-type Pfk13 genes in 21.84% of blood and 44.44% of saliva samples correspondingly. For each of the genes evaluated, saliva portrayed great diagnostic performance when compared with blood. Conclusion: Findings from this study have established the prevalence of malaria and the resistance pattern of P. falciparum in the study area. The findings may help in formulating drug policies and suggest the use of saliva as a noninvasive point-of-care method of diagnosing malaria potentially deployable to rural endemic areas