Hasil untuk "physics.soc-ph"

B. Bjellqvist, K. Ek, P. Righetti et al.

G. Smolders, J. van der Meij, M. Loosdrecht et al.

M. Kosmulski

S. Khanal, Wen‐Hsing Chen, Ling Li et al.

O. Abollino, Maurizio Aceto, M. Malandrino et al.

E. Svastova, A. Hulikova, Monika Rafajová et al.

J. Wootton, C. Pfister, James D. Forester et al.

I. Mainie, R. Tutuian, S. Shay et al.

C. Hunte, E. Screpanti, M. Venturi et al.

Jutaek Nam, Nayoun Won, Ho Jin et al.

Xin Zhang, S. Rehm, Marina M. Safont-Sempere et al.

G. Askarieh, M. Hedhammar, K. Nordling et al.

Wei Chen, F. Meng, Ru Cheng et al.

G. Malin, R. Morris, Khalid Khan

Objective To evaluate the association between umbilical cord pH at birth and long term outcomes. Design Systematic review and meta-analysis. Data sources Medline (1966-August 2008), Embase (1980-August 2008), the Cochrane Library (2008 issue 8), and Medion, without language restrictions; reference lists of selected articles; and contact with authors. Study selection Studies in which cord pH at birth was compared with any neonatal or long term outcome. Cohort and case-control designs were included. Results 51 articles totalling 481 753 infants met the selection criteria. Studies varied in design, quality, outcome definition, and results. Meta-analysis carried out within predefined groups showed that low arterial cord pH was significantly associated with neonatal mortality (odds ratio 16.9, 95% confidence interval 9.7 to 29.5, I2=0%), hypoxic ischaemic encephalopathy (13.8, 6.6 to 28.9, I2=0%), intraventricular haemorrhage or periventricular leucomalacia (2.9, 2.1 to 4.1, I2=0%), and cerebral palsy (2.3, 1.3 to 4.2, I2=0%). Conclusions Low arterial cord pH showed strong, consistent, and temporal associations with clinically important neonatal outcomes that are biologically plausible. These data can be used to inform clinical management and justify the use of arterial cord pH as an important outcome measure alongside neonatal morbidity and mortality in obstetric trials.

J. Rousk, P. Brookes, E. Bååth

Z. Poon, D. Chang, Xiaoyong Zhao et al.

Renata Negrini, R. Mezzenga

Li Yuan, Qianqian Tang, Dong Yang et al.

Xiluan Wang, H. Bai, G. Shi

Xuewu Liu, Mark C. Patsavas, R. Byrne

Spectrophotometric procedures allow rapid and precise measurements of the pH of natural waters. However, impurities in the acid–base indicators used in these analyses can significantly affect measurement accuracy. This work describes HPLC procedures for purifying one such indicator, meta-cresol purple (mCP), and reports mCP physical–chemical characteristics (thermodynamic equilibrium constants and visible-light absorbances) over a range of temperature (T) and salinity (S). Using pure mCP, seawater pH on the total hydrogen ion concentration scale (pHT) can be expressed in terms of measured mCP absorbance ratios (R = λ2A/λ1A) as follows:where −log(K2Te2) = a + (b/T) + c ln T – dT; a = −246.64209 + 0.315971S + 2.8855 × 10–4S2; b = 7229.23864 – 7.098137S – 0.057034S2; c = 44.493382 – 0.052711S; d = 0.0781344; and mCP molar absorbance ratios (ei) are expressed as e1 = −0.007762 + 4.5174 × 10–5T and e3/e2 = −0.020813 + 2.60262 × 10–4T + 1.0436 × 10–4 (S – 35). The mCP absorbances, λ1A and λ2A, used to calculate R are measured at wavelengths (λ) of 434 and 578 nm. This characterization is appropriate for 278.15 ≤ T ≤ 308.15 and 20 ≤ S ≤ 40.