Failure analysis and shock protection of external hard disk drive

Technology for processing and storage of data in portable external storage hard disks has increasingly improved over the years. Currently, terabytes of data can be stored in one portable external storage hard disk drive. Storing such amount of data on a single disk on itself is a risk. Several instances of data lost by big institutions and Multinational Corporation leading to several billions of Naira annually have been reported. As the technology for storing data is improving, there is an equal need to improve on data safety and reliability. It has been estimated that hardware structural failure contributes to over 40% of reported data loss annually worldwide.  This case study is aimed at failure analysis and shock protection of external hard disk drive. In order to achieve this aim, the hard disk components were assumed as a single block structure and mass-spring-damper system was used to analytically model its structural responses to free fall drop-impact shock and vibration. Secondly, the hard disk was also modeled as a beam element, which was again, subjected to impact of free fall from selected heights. The analytical results of these two mathematical models are comparable and within the limits. Then, Finite Element Analysis system was used to simulate the impact of stress on the structure of the hard disk before and after enclosing it in a padded casing. It was discovered that the padded casing absorbed shock and vibration from direct impact on the enclosed disk with a significant reduction of stress by 90%. Vibration and shock protection is recommended to be designed into all such delicate engineering components and systems to mitigate occurrence of failure. http://dx.doi.org/10.4314/njt.v35i4.2

Malaria diagnosis and treatment amongst health workers in University of Nigeria Teaching Hospital Enugu, Nigeria

Background: Confirmation of malaria and appropriate treatment are keys to malaria control.Objective: To determine the practice of malaria diagnosis and treatment in a Nigerian tertiary hospital.Materials and Methods: Retrospective review of patients’ records at the Children’s Clinic in UNTH.Results: Out of 6,684 children seen within the one year reviewed period, children diagnosed with malaria were 35.8 percent. Males were 60 percent and females were 40 percent. Children under five years were 72.6 percent of the total. Folders successfully traced were 1012; in 92 percent investigations for malaria were requested while 32 percent had differential diagnosis. Out of the 931 malaria investigations requested, 30percent did the tests and positive results were 94.9 percent. Presumptive treatment was 98 percent. Majority (83.3%) received ACTs.Conclusion: The practice of presumptive treatment was high and few cases had a differential diagnosis. Training of health workers on the need to confirm malaria cases is required.Key words: Children, diagnosis, malaria, Nigeria, treatmen

Asymptomatic bacteriuria among pregnant women with sickle cell trait in Enugu, South Eastern Nigeria

Context: Asymptomatic bacteriuria (ASB) in pregnancy is a major risk factor for developing acute cystitis and pyelonephritis, especially, among women with sickle cell disease. This study compared the prevalence, pattern, and microbiological characteristics of ASB in pregnancy between sickle cell trait (HbAS) and normal hemoglobin AA(HbAA) genotype subjects.Materials and Methods: Culture and sensitivity of mid‑stream urine samples were collected from 300 HbAS women and 300 matched HbAA control at the antenatal clinic of University of Nigeria Teaching Hospital Enugu, Nigeria from August 2010 to December 2011. Analysis was both descriptive and inferential at 95% confidence levels.Results: Prevalence of ASB in HbAS and HbAA women were 32.7% (98/300) and 32% (96/300) respectively (odd ratio (OR) =1.03 [95% confidence interval (CI) 0.73, 1.45]). Escherichia coli was the most common organism isolated in both the HbAS group (56.1%, 55/98) and control group (61.4%, 59/96), (OR = 0.80 [95% CI 0.45, 1.42]). The  antibiotics with the highest microbial sensitivity were ciprofloxacin 90.8% (89/98) and gentamicin 100% (98/98) for HbAS and HbAA women respectively.Conclusions: The prevalence of ASB in pregnant women with HbAS in Enugu, Nigeria was high and did not vary significantly from that of woman with HbAA. Therefore, pregnant women irrespective of their sickle cell status would benefit from routine screening for ASB.Key words: Asymptomatic bacteriuria, Enugu‑Nigeria, pregnant women, sickle cell trai

Saturated electric field effect at semi-insulating GaAs-metal junctions studied with a low energy positron beam

The interfacial electric field established under different reverse bias conditions in Au and Ni on semi-insulating GaAs junctions has been studied by means of a low energy positron beam. The technique used is that of monitoring the positron drift to the interface through changes in the annihilation radiation lineshape as a function of incident positron beam energy at different reverse biases The data show a small but clear electric field drift of positrons towards the interface that increases more rapidly at low voltages (less than 50 V) which at higher biases tends towards saturation This confirmation of electric field saturation adds further weight to the picture of an electric field enhanced electron capture cross section for the ionized EL2 defect. Electric field values extracted from the data are compared with results from other techniques and suggest that enhanced electron capture is already occurring at the relatively low built-in fields (∼1 kV cm-1) found at the unbiased junction, with a rapid increase of EL2+ neutralization occurring for biases above 10 V. At still higher fields ∼10 kV cm-1 (biases>50 V), there appears to be an additional threshold for more complete EL2+ neutralization adjacent to the contact. The present study clearly demonstrates the often overlooked necessity of catering for built-in electric fields in positron diffusivity studies of III-V semiconductors where surface midgap Fermi-level pinning is common. © 1997 American Institute of Physics.published_or_final_versio

Seroprevalence of Human Immunodeficiency Virus, Hepatitis B, Hepatitis C, syphilis, and co infections among antenatal women in a tertiary institution in south east, Nigeria

Background: Sexually transmitted infections and human immunodeficiency virus (HIV)/AIDS are a major public health concern owing to both their prevalence and propensity to affect offspring through vertical transmission. Aim: The aim was to determine the seroprevalence of HIV, hepatitis B virus (HBV), hepatitis C virus (HCV), syphilis, and co‑infections among antenatal women in Enugu, South‑East Nigeria. Materials and Methods: A retrospective study of antenatal women at the University of Nigeria Teaching Hospital, Enugu, South‑East Nigeria from 1st May 2006 to 30th April 2008. A pretested data extraction form was used to obtain data on sociodemographic variables and screening test results from the antenatal records. The analysis was done with SPSS version 17 (Chicago, IL, USA). Results: A total of 1239 antenatal records was used for the study. The seroprevalence of HIV, HBV, HCV, and syphilis among the antenatal women were 12.4% (154/1239), 3.4% (42/1239) 2.6 (32/1239) 0.08% (1/1239), respectively. The HIV/HBV and HIV/HCV co‑infection prevalence rates were 0.24% (3/1239), 0.16% (2/1239), respectively. There was no HBC and HCV co‑infection among both HIV positive and negative antenatal women. There was no statistically significant difference in HBV and HCV infection between the HIV positive and negative antenatal women. The only woman that was seropositive for syphilis was also positive to HIV. Conclusion: The seroprevalence of HIV, HBV, HCV, and syphilis is still a challenge in Enugu. Community health education is necessary to reduce the prevalence of this infection among the most productive and economically viable age bracket.Keywords: Antenatal women, Co‑infection, Human immunodeficiency virus, Hepatitis C virus, Hepatitis B virus, Seroprevalence, Syphili

Porcine dentin sialoprotein glycosylation and glycosaminoglycan attachments

<p>Abstract</p> <p>Background</p> <p>Dentin sialophosphoprotein (Dspp) is a multidomain, secreted protein that is critical for the formation of tooth dentin. Mutations in <it>DSPP </it>cause inherited dentin defects categorized as dentin dysplasia type II and dentinogenesis imperfecta type II and type III. Dentin sialoprotein (Dsp), the N-terminal domain of dentin sialophosphoprotein (Dspp), is a highly glycosylated proteoglycan, but little is known about the number, character, and attachment sites of its carbohydrate moieties.</p> <p>Results</p> <p>To identify its carbohydrate attachment sites we isolated Dsp from developing porcine molars and digested it with endoproteinase Glu-C or pronase, fractionated the digestion products, identified fractions containing glycosylated peptides using a phenol sulfuric acid assay, and characterized the glycopeptides by N-terminal sequencing, amino acid analyses, or LC/MSMS. To determine the average number of sialic acid attachments per N-glycosylation, we digested Dsp with glycopeptidase A, labeled the released N-glycosylations with 2-aminobenzoic acid, and quantified the moles of released glycosylations by comparison to labeled standards of known concentration. Sialic acid was released by sialidase digestion and quantified by measuring β-NADH reduction of pyruvic acid, which was generated stoichiometrically from sialic acid by aldolase. To determine its forms, sialic acid released by sialidase digestion was labeled with 1,2-diamino-4,5-methyleneoxybenzene (DMB) and compared to a DMB-labeled sialic acid reference panel by RP-HPLC. To determine the composition of Dsp glycosaminoglycan (GAG) attachments, we digested Dsp with chondroitinase ABC and compared the chromotagraphic profiles of the released disaccharides to commercial standards. N-glycosylations were identified at Asn³⁷, Asn⁷⁷, Asn¹³⁶, Asn¹⁵⁵, Asn¹⁶¹, and Asn¹⁷⁶. Dsp averages one sialic acid per N-glycosylation, which is always in the form of N-acetylneuraminic acid. O-glycosylations were tentatively assigned at Thr²⁰⁰, Thr²¹⁶and Thr³¹⁶. Porcine Dsp GAG attachments were found at Ser²³⁸and Ser²⁵⁰and were comprised of chondroitin 6-sulfate and chondroitin 4-sulfate in a ratio of 7 to 3, respectively.</p> <p>Conclusions</p> <p>The distribution of porcine Dsp posttranslational modifications indicate that porcine Dsp has an N-terminal domain with at least six N-glycosylations and a C-terminal domain with two GAG attachments and at least two O-glycosylations.</p

Detection of Lyman-alpha Emitting Galaxies at Redshift z=4.55

Studies of the formation and early history of galaxies have been hampered by the difficulties inherent in detecting faint galaxy populations at high redshift. As a consequence, observations at the highest redshifts (3.5 < z < 5) have been restricted to objects that are intrinsically bright. These include quasars, radio galaxies, and some Ly alpha-emitting objects that are very close to (within ~10 kpc) -- and appear to be physically associated with -- quasars. But the extremely energetic processes which make these objects easy to detect also make them unrepresentative of normal (field) galaxies. Here we report the discovery using Keck spectroscopic observations of two Ly alpha-emitting galaxies at redshift z = 4.55, which are sufficiently far from the nearest quasar (~700 kpc) that radiation from the quasar is unlikely to provide the excitation source of the Ly alpha emission. Instead, these galaxies appear to be undergoing their first burst of star formation, at a time when the Universe was less than one billion years old.Comment: 8 pages, 1 landscape table, and 3 PostScript figures. Uses aaspp4.sty, flushrt.sty, aj_pt4.sty, overcite.sty (style macros available from xxx.lanl.gov) Figure 1 is bitmapped to 100 dpi. The original PostScript version of Fig. 1 is available via anonymous ftp to ftp://hubble.ifa.hawaii.edu/pub/preprints To appear in Natur

How do enamelysin and kallikrein 4 process the 32-kDa enamelin?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74876/1/j.1600-0722.2006.00281.x.pd

A domain decomposition non-intrusive reduced order model for turbulent flows

In this paper, a new Domain Decomposition Non-Intrusive Reduced Order Model (DDNIROM) is developed for turbulent flows. The method works by partitioning the computational domain into a number of subdomains in such a way that the summation of weights associated with the finite element nodes within each subdomain is approximately equal, and the communication between subdomains is minimised. With suitably chosen weights, it is expected that there will be approximately equal accuracy associated with each subdomain. This accuracy is maximised by allowing the partitioning to occur through areas of the domain that have relatively little flow activity, which, in this case, is characterised by the pointwise maximum Reynolds stresses.A Gaussian Process Regression (GPR) machine learning method is used to construct a set of local approximation functions (hypersurfaces) for each subdomain. Each local hypersurface represents not only the fluid dynamics over the subdomain it belongs to, but also the interactions of the flow dynamics with the surrounding subdomains. Thus, in this way, the surrounding subdomains may be viewed as providing boundary conditions for the current subdomain.We consider a specific example of turbulent air flow within an urban neighbourhood at a test site in London and demonstrate the effectiveness of the proposed DDNIROM