Are current methods of measurement of erythropoietin (EPO) in human plasma or serum adequate for the diagnosis of polycythaemia vera and the assessment of EPO deficiency?

Current methodology for the immunoassay of erythropoietin (EPO) in human plasma or serum is reviewed, with an emphasis on measurement of EPO concentrations in the low and normal ranges, analytical interference and blood sampling requirements. In only 2 out of 8 research or in-house immunoassays reported since 1987 was there evidence that patients with polycythaemia vera (PV) could be identified, PV being an EPO-independent form of polycythaemia in which EPO concentrations are low in untreated cases. The same was true for only 1 out of 13 currently available kit methods. Remarkable differences in sample stability have been observed with different methods. Measurement of EPO in serum is recommended in most published articles. However, only EDTA plasma seems to be acceptable for the one generally available method with proven high diagnostic sensitivity for PV. It is concluded that most EPO assay methods have not been shown to be adequate for the measurement of the low EPO concentrations, and thus have poor diagnostic sensitivity for PV. It is inferred that they might not be appropriate to assess states of EPO deficiency. Only when a sufficiently sensitive diagnostic method becomes generally available will it be possible to define the various causes of low EPO concentrations. As in other fields of polypeptide hormone measurement, further developments in the field of EPO assay may be expected to be important in diagnostic medicine.     

On Closure under Formation of Parallel Systems

A parallel system of s-independent, identical components has the same aging property (eg, IFR or IFRA) as the components.     

Photocross-linking of low-density polyethylene. I. Kinetics and reaction parameters

The kinetic characteristics and the reaction conditions of photocross-linking of low-density polyethylene (LDPE) in the melt have been studied using benzophenone (BP) and its derivatives such as 4-chlorobenzophenone (4-CBP) as photoinitiator and triallyl cyanurate (TAC) as cross-linker. The efficiency of the photoinitiated cross-linking system LDPEBP-TAC and various factors affecting the cross-linking process, such as photoinitiator and cross-linker and their concentrations, irradiation time, temperature, and atmosphere, and UV light intensity were examined extensively by determining gel content, IR, and UV spectra. It has been found (i) that LDPE samples of 2–3 mm thickness are easily cross-linked to a gel content of about 70% with a UV-irradiation time of about 15 s under optimum conditions; (ii) that the photoinitiating system of a suitable initiator combined with a multifunctional cross-linker such as 4-CBP–TAC can enhance the efficiency of photocross-linking reactions, especially by increasing the initial rate of cross-linking; (iii) that photocross-linking of LDPE should be carried out in the melt, which increases the penetration of UV light by decreasing the scattering by crystallites, and (iv) that the rate of cross-linking is proportional to the square of the light intensity. An increase in light intensity can decrease the concentration of photoinitiator required to reach a certain rate of cross-linking. The photocross-linking of polyethylene is promising for industrial applications. © 1993 John Wiley & Sons, Inc.     

牛奶的超高温处理

1　牛奶牛奶含有多种人体所需的营养成分和维生素 ,如维生素Ａ和Ｄ等 ,是我们膳食的重要组成部分。研究发现 ,牛奶的营养组成比例是最接近人奶的天然食品。随着生活水平的不断提高和商品供给的日益丰富 ,消费者的需求也不仅仅局限于普通白奶了。多种风味奶、脱脂奶、强化奶及低乳糖牛奶应运而生。通常 ,我们讲到的“奶”是指牛奶 ,但在世界各地 ,由于地理条件 ,气候环境不同 ,也有很多其他品种供应 ,例如水牛奶、骆驼奶、山羊奶、豆奶、大麦奶等等。不同类型的奶往往要求不同的加工工艺和手段 ,以尽可能地保持原料奶中的营养成分和特有风味…     

Analysis of Proton Exchange Membrane Fuel Cell Systems Involving Heat Exchangers

Proton-exchange membrane fuel cells (PEMFCs) have been regarded as the new energy source for portable, stationary, and automotive applications. However, commercial exploitation of PEMFCs is still in an early stage, due to shortage of infrastructure in the society, high cost, and particularly the difficulty of the water/thermal management. One of the objectives of the current work is to analyze the water/thermal balances in a 100-kW class PEMFC system, consisting of PEMFC stack, compressor, intercooler, heater, humidifier, condenser, and radiator. As a first step, the heat and mass balances in the heat exchangers are analyzed for various water recovery schemes, followed by an analysis of the PEMFC stack effects on the system balance concerning the pressure drop and operating current density.     

The Peak of the Oil Age – Analyzing the world oil production Reference Scenario in World Energy Outlook 2008

The assessment of future global oil production presented in the IEA’s World Energy Outlook 2008 (WEO 2008) is divided into 6 fractions; four relate to crude oil, one to non-conventional oil, and the final fraction is natural-gas-liquids (NGL). Using the production parameter, depletion-rate-of-recoverable-resources, we have analyzed the four crude oil fractions and found that the 75 Mb/d of crude oil production forecast for year 2030 appears significantly overstated, and is more likely to be in the region of 55 Mb/d. Moreover, analysis of the other fractions strongly suggests lower than expected production levels. In total, our analysis points to a world oil supply in 2030 of 75 Mb/d, some 26 Mb/d lower than the IEA predicts.     

Endwall convective heat transfer for bluff bodies

The endwall heat transfer characteristics of forced flow past bluff bodies have been investigated using liquid crystal thermography (LCT). The bluff body is placed in a rectangular channel with both its ends attached to the endwalls. The Reynolds number varies from 50,000 to 100,000. In this study, a single bluff body and two bluff bodies arranged in tandem are considered. Due to the formation of horseshoe vortices, the heat transfer is enhanced appreciably for both cases. However, for the case of two bluff bodies in tandem, it is found that the presence of the second bluff body decreases the heat transfer as compared to the case of a single bluff body. In addition, the results show that the heat transfer exhibits Reynolds number similarity. For a single bluff body, the Nusselt number profiles collapse well when the data are scaled by Re^0.55; for two bluff bodies arranged in tandem, the heat transfer scaling is changed to Re^0.51, indicating that the power index of Reynolds number is flow dependent.     

Effects of agglomerate model parameters on transport characterization and performance of PEM fuel cells

A three-dimensional, non-isothermal and two-phase flow model for proton exchange membrane (PEM) fuel cells is developed. In the cathode catalyst layer, a spherical agglomerate model with consideration of catalyst layer structure and liquid water effect is applied to determine the electrochemical kinetics. The size and structure of the agglomerates are determined by the following parameters, i.e., the agglomerate radius (r_agg), the volume fraction of ionomer within the agglomerate (L_i,agg), and the thickness of the ionomer film over the agglomerate (δ_i). It is noted that a random combination of the three above parameters is widely used in agglomerate models by researchers. In this paper, the effects of r_agg and L_i,agg on the cell performance and local transport characteristics are numerically investigated by using the developed model with consideration of the relationships between agglomerate parameters. It is concluded that the cell performance is significantly improved by decreasing r_agg and increasing L_i,agg at medium and high current densities when the volume fractions of the solid phase (L_Pt/C) and ionomer phase (L_i) are maintained constant. In addition, the distributions of oxygen concentration, liquid water saturation, volumetric current density and effectiveness factor are also strongly influenced by the variation of the two parameters.