Parametric study of two planar high power flexible solar array concepts

The design parameters examined were: frequency, aspect ratio, packaging constraints, and array blanket flatness. Specific power-to-mass ratios for both solar arrays as a function of array frequency and array width were developed and plotted. Summaries of the baseline design data, developed equations, the computer program operation, plots of the parameters, and the process for using the information as a design manual are presented

Summary of Voyager Design and Flight Loads

Estimates of flight loads for Voyager 1 and Voyager 2 are summarized and compared to the Voyager design loads obtained from the shock spectra/impedance method and to the loads obtained using space vehicle transient loads analysis. These estimates were obtained by using the measured flight accelerations at the launch vehicle/spacecraft interface as forcing functions for the Voyager mathematical model. Based on these data, an assessment of the shock spectra/impedance loads method used for Voyager is presented. The following conclusions were reached: (1) the shock spectra approach provided reasonable conservative design loads for Voyager, (2) care has to be executed to insure that all critical events are accounted for in constructing shock spectra envelopes, (3) the selection of critical events is not always obvious, especially for those flight events wherein the spacecraft dynamic characteristics are important, and (4) the success of the method is strongly dependent on the analysts' experience and judgement

Orbiting astronomical observatory A-2 space vehicle response to transient loadings at Atlas booster engine cutoff

Predicting structural response of OAO A-2 to transient loading at Atlas booster engine cut-of

Paleohydrological Reconstruction from Late Holocene Records in Interdune Lakes (N'Guigmi, Northern Bank of the Lake Chad, Niger)

An old erg covers the northern part of the Lake Chad basin. This dune landform allowed the formation of many inter- dune ponds of various sizes. Still present in certain zones where the groundwater level is high (e.g. Kanem, southern Manga), these ponds formed in the past a vast network of lacustrine microsystems, as shown by the nature and the dis- tribution of their deposits. In the Manga, these interdune deposits represent the main sedimentary records of the Holo- cene environmental succession. Their paleobiological (pollens, diatoms, ostracods) and geochemical (δ18O, δ13C, Sr/ Ca) contents are often the basis for paleoenvironmental reconstruction. On the other hand, their sedimentological char- acters are rarely exploited. This study of palustro-lacustrine deposits of the Holocene N'Guigmi lake (northern bank of the Lake Chad; Niger) is based on the relationships between the sedimentological features and the climato-hydrological fluctuations. The mineralogical parameters (e.g. calcium carbonate content, clay mineralogy) and the nature of autoch- thonous mineralization (i.e. amorphous silica, clays, calcium carbonates) can be interpreted using a straightforward hy- dro-sedimentary model. Established to explain the geochemical dynamics of Lake Chad, this model is based on a bio- geochemical cycle of the main elements (i.e. silicium, calcium) directly controlled by the local hydrological balance (i.e. rainfall/evaporation ratio). All these results show that a detailed study of sedimentological features can provide impor- tant paleohydrological informations about the regional aridification since ca 6500 14C BP

Potentials of Sludge from Drinking Water Treatment Plant for Use as Source of Soil Nutrients for Reclamation of Degraded Land

The residuals from Gubi drinking water treatment plant are usually discharged directly into the nearby streams without any form of treatment. The decomposition of the organic materials contained in the untreated sludge has caused the production of malodorous gases and unsightly condition in the area. The disposal of this sludge in an environmentally friendly manner is therefore not only desirable but necessary. The aim of this investigation was to assess the feasibility of utilizing the residuals from Gubi water treatment plant as a source of nutrients for reclamation of degraded lands especially those arising from mining activities. The study was carried out at Gubi water treatment plant located in the vicinity of Gubi Dam water reservoir.Ten sludge samples were collected from each of the three clerifiers. Important sludge properties that are known to aid nutrients status of soil were analyzed using standard laboratory procedures. The means of various soil quality parameters recorded in the WTRs were 6.8, 20.06g/kg, 34.90g/kg, 1.65g/kg, 2.30g/kg, 13.45mg/kg, 2.50Cmol/kg, 2.10Cmol/kg and 28Cmol/kg for pH, Organic C, Organic Matter, K, Total N, Olsen P, Ca, Mg and CEC respectively. The means of all the parameters analysed falls within the ranges considered good for vegetation growth. The heavy metals concentrations recorded in the residual were 1.8mg/kg, 0.1mg/kg, 2mg/kg, 29mg/kg, 66mg/kg, 15mg/kg, 8.7mg/kg, 6.2mg/kg and 0.03mg/kg for As, Cd, Pb, Cu, Zn, Ni, Co, Cr and Hg respectively. The concentrations of all the metals did not exceed the acceptable threshold limits recommended by regulatory authorities. Considering the enormous amount of plant nutrients and absence of excessive toxic metals in Gubi WTRs, it is safe to conclude that the residual can be use as a source of soil nutrients for reclamation of degraded land. Key words: Sludge, Soil Nutrients, Degraded Land, Reclamatio

Performance of urinary survivin as a non-invasive molecular marker of bladder carcinoma in a schistosomiasis endemic area

Objective: To compare the sensitivity, specificity, positive predictive value, negative predictive value of urinary survivin and that of urine cytology in the diagnosis of bladder carcinoma in a schistosoma endemic area.Design and setting: This is a 12-month prospective study of patients with features of bladder carcinoma as study group and patients with other urologic conditions and healthy volunteers as control group.Participants: Patients with features of bladder carcinoma formed the study group, while patients with other urological conditions and healthy volunteers formed the control group.Results: There were 52 patients in study group and 36 patients in control group. The mean ages of patients in the study and control groups were 47.17 ± 17.00 and 44.19 ± 18.89 years respectively. There were 48 males and 4 females in the study group, giving a male: female ratio of 12:1. Thirty-one (60 %) of the patients were farmers and 44 patients (85%) had history suggestive of schistosomiasis at childhood. The sensitivity of urine cytology and survivin in the study were 29.1% and 100.0% respectively. The specificity of urine cytology and survivin were 100.0%and 100.0% respectively (p= 0.05). The marker was associated with false positive (FP) results in patients with prostate cancer.Conclusion: Urinary survivin is highly sensitive, specific and predictive of bladder carcinoma in our environment. The marker is associated with false positive results in patients with prostate cancer.Funding: By authorsKeywords: survivin, urinary bladder carcinoma, schistosomiasis, sensitivity, specificit

Comparative Study of Maximum Power Point Tracking with a Modified DC DC Converter

Maximum power points are used to find the voltages and currents at which a photovoltaic (PV) panel should operate to obtain maximum power. In order to deliver highest power, an efficient DC DC converter and a reliable tracking algorithm are used. There is also the need to continuously find the maximum power under any environmental conditions at all times. This research is intended to study a comparative performance of maximum power point (MPP) which is presented under uniform irradiance condition. The algorithm employed is an improved cuckoo search algorithm and the DC-DC Converter( switched mode power supply) has been modified by including a synchronous rectifier connected to a load, the performance of the system is validated using MATLAB/Simulink and practical implementation for this work. A comparison of the MATLAB Simulation with the practical implementation of MPP is presented using maximum power and percentage tracking efficiency as performance metric. From the MATLAB results obtained, maximum extracted power is 26.81W and the hardware implementation gives a maximum power of 28.71W. Tracking efficiency improves by 6.62%. The results show the practical MPP gives a better maximum power, which consequently improves the Photovoltaic systems efficiency and conversely mitigates the power consumption and the cost of the system than the simulation result obtained in MATLAB

Effect of hormonal and copper IUDs on genital microbial colonisation and clinical outcomes in North-Western Nigeria

Background: Intrauterine devices are one of the popular long term reversible contraceptive methods. Earlier forms were associated with genital infections, however more recent types such copper IUDs and hormonal types have been shown to have better safety profile. However, there is no conclusive evidence to demonstrate that hormonal IUD is less associated with genital infection when compared with copper IUDs. The objectives include determination of prevalence of genital tract infections among IUD users, to determine the type of IUD that is less associated with genital infection, and also determine clinical features seen among IUD users.Methods: We conducted a descriptive, cross sectional study of clients who were at 6 months following IUD insertion. Endocervical and high vaginal samples were taken to isolate microbes.Results: The prevalence of genital tract infection was 20% in Copper IUD users and 8.6% among LNG-IUS users. Genital infection was significantly higher among copper IUD users compared to hormonal IUD users (p=0.038, OR= 2.88). Abnormal vaginal discharge was the commonest symptoms among IUD users and formal education was associated with less risk of genital infections (p=0.048).Conclusions: Hormonal IUDs are less associated with genital tract infection compared to copper IUDs and women with formal education are less likely to have genital infection among IUD users