Using femtosecond laser pulses for electronic distance meter calibration.

Electronic distance meters (EDMs) are widely used in different applications, such as surveying and civil engineering. In order to calibrate an EDM, different techniques can be used, including displacement interferometers and reference baselines. In this paper, an indoor baseline is designed and then accurately measured using femtosecond laser pulses from an optical frequency comb to be used for EDM calibration. The baseline consists of 13 fixed bases that cover 58 m distance. In order to accurately measure the distances between the bases, autocorrelation between femtosecond laser pulses is employed. The measurement shows a maximum precision of 14 µm over the 13 bases. Although this deviation is dominated mainly by the placement of the target mirror, the system capability is much more sufficient to safely calibrate the best available commercial EDM. The stability of the baseline is also investigated by measuring the interbase distances over long periods of time.

Microbial etiology of community acquired pneumonia among infants and children admitted to zagazig university pediatric hospital

Background: While recognizing the etiology of community-acquired pneumonia is necessary for formulating local antimicrobial guidelines, limited data is published about this etiology in Egyptian pediatric patients. The aim of this study is to elucidate the common bacterial pathogens causing CAP among immunocomptent infants and preschool children admitted to Zagazig university Pediatric hospital. Methods: 48 infant and preschool children admitted to pediatric hospital of Zagazig university and presented with signs of pneumonia according to WHO. Etiological agents were identified using conventional bacteriological identification methods and Ig M antibodies detection against common a typical bacteria and respiratory viruses. Results: Staph. Aureus 35.4% is the most common pathogen detected in sputum regardless the age group .In blood culture results negative results in most cases of pneumonia 62.5%. Staph. Aureus is the most common pathogen detected in blood culture in positive cases regardless the age group 18.7% , E Coli 6.25%, Klebsiella 2.08.In Serology results significant difference according to age in viral pneumonia occurrence and non significant difference in bacterial pneumonia based on serological findings with higher diagnosis of Legionella pneumophila 33.33% as a causative organism. Conclusion: This study provides preliminary data regarding the spectrum and frequency of microorganisms causing CAP in infants and preschool children

Assessment of the Effectiveness of Percutaneous Transluminal Balloon Angioplasty for Failing or Nonmaturing Arteriovenous Fistulae for Hemodialysis.

BACKGROUND: Autologous arteriovenous (A-V) fistulae are the recommended arteriovenous access for long-term dialysis in chronic renal failure patients. However, the rate of nonmaturity and failure is still significant. The present study aimed at salvaging fistulas using percutaneous transluminal balloon angioplasty (PTA). METHODS: Thirty-two patients with nonmaturing or failing fistulas were included, to which they were subjected to PTA with preintervention and postintervention fistulograms to assess the success rate in restoring the fistulae's patency and function. RESULTS: Salvage rate was 26 of 32 fistulas (81.3%) in which the fistulas regain their usability for hemodialysis at least for 3 months of follow-up, 4 cases (12.5%) persist nonmature and 2 cases (6.3%) were not used for stenosis. CONCLUSIONS: PTA is a safe and effective method for treating nonmature and failing native A-V fistulas.

Absolute gauge block calibration using ultra-precise optical frequency synthesizer locked to a femtosecond comb.

In this paper, we report a gauge block (GB) calibration that is traceable to the SI unit of time, the second. Four ultra-stable optical telecommunication wavelengths near 1556 nm are obtained by locking a narrow-tuning-range fiber laser to a fiber-based femtosecond frequency comb. Since the GB calibration system does not operate at this region of spectrum, the superior frequency stability of the laser is transferred to the 778 nm region by using a waveguide periodically poled lithium niobate crystal. After applying the locking scheme, the stability and accuracy of the laser become better than 8×10(-12). The frequency-doubled light is sent through 30 m optical fiber to a GB interferometer, which is installed at a different laboratory in the same building. Using this calibration scheme, a GB with a nominal length of 100 mm is calibrated with an uncertainty of ±52 nm. This uncertainty value is still comparable to or even better than other metrology laboratories for a similar block length.

Seroprevalence of Helicobacter pylori infection among family members of infected and non-infected symptomatic children.

This study determined the prevalence of seropositivity of anti-H. pylori IgG antibodies, and evaluated some socio-epidemiologic characteristics among family members of infected and non-infected symptomatic children. One hundred children with upper gastrointestinal symptoms without previous H. pylori eradication treatment were prospectively studied by both upper endoscopy with histopathological biopsies examination, and serum anti-H. pylori IgG test between July 2012 to June 2013. The patients were subdivided into: H. pylori infected children (GI), and H. pylori non-infected children (GII). Also, 320 of their family members were examined for serum anti-H. pylori IgG and stool antigen tests. Sheets were filled out included personal and medical history. The results showed statistically significant difference between both groups as regard dyspepsia, anemia, and histopathological findings (chronic active gastritis, peptic ulcer, and duodenitis). Family members were subdivided into: those of H. pylori infected symptomatic children (165) and those of H. pylori non-infected symptomatic children (155). Anti-H. pylori IgG prevalence was significantly higher in relatives of GI than those of GII (69.1% vs. 29%; p<0.05). The seroprevalence of H.pylori infection in all family members was (49.7%). Mothers of GI showed the highest seroprevalence (39.5%) as compared to fathers and siblings (22.8%, & 37.7%, respectively). Relatives of GI with low socioeconomic status, and lived in rural area showed the highest seroprevalence (82.5%, & 78.1% respectively).

Er-doped fiber frequency comb with mHz relative linewidth.

A low-noise fiber frequency comb is demonstrated to improve the frequency accuracy and linewidth by suppressing the phase noise caused by the nonlinear self-phase modulation as well as the amplified spontaneous emission within the Er-doped fiber amplifier. The linewidth of the carrier-envelop- offset signal measures less than 1.9 mHz and the frequency stability well follows the reference Rb clock. This achievement will facilitate the use of the fiber frequency comb for industrial applications to precision near-infrared spectroscopy, frequency calibration, optical clocks and length metrology.