排序方式: 共有6条查询结果,搜索用时 15 毫秒
1
1.
P. K. Kamweru F. G. Ndiritu T. K. Kinyanjui Z. W. Muthui R. G. Ngumbu P. M. Odhiambo 《Journal of Macromolecular Science: Physics》2013,52(7):1338-1349
Plastic bags mostly made of polyethylene (PE) cause pollution as solid waste due to their non-degradability nature. Initiation of a degradative process by enhanced photo-oxidation is a possible method for an accelerated degradation. This paper presents temperature treatment effects on PE films where photodegradation was initiated using ultraviolet (UV) irradiation in the ranges of 200–300 nm and 300–400 nm for 2 hr. Effects of temperature of 40°C and 55°C on non-UV-irradiated and UV-irradiated PE films processed by conventional methods were investigated and evaluated after 50 hr, 150 hr, and 350 hr of temperature exposure. The effects of UV wavelength range irradiation on the degradation were deduced. Measuring the dynamic moduli using a dynamic mechanical analyzer monitored the degradation. The decrease in average storage modulus was 62% with treatment at 55°C, higher than the 16% drop at 40°C for unirradiated samples after 350-hr exposure. Cross-linking in UV-exposed samples, characterized by an increase in dynamic modulus (stiffening), was observed followed by a reduction of storage modulus. Temperature treatment at 55°C together with 300–400-nm UV range irradiation resulted in the largest increase, i.e., 22% after 150 hr, followed by the largest reduction of storage modulus, i.e., 74.6% for a cumulative 350-hr exposure. 相似文献
2.
Odhiambo A Perlman DH Huang H Costello CE Farber HW Steinberg MH McComb ME Klings ES 《Rapid communications in mass spectrometry : RCM》2007,21(14):2195-2203
Pulmonary hypertension (PH) in sickle cell anemia (SCA) is characterized by decreased nitric oxide bioavailability that might, in part, be related to oxidative stress. Oxidative post-translational modifications of plasma proteins may serve as hallmarks of disease severity and could result in altered protein function and structure. We hypothesized that serum albumin in patients with PH of SCA undergoes oxidative post-translational modification and that this modification may reflect important mediators of disease pathogenesis that are common to both idiopathic pulmonary arterial hypertension (IPAH) and PH of SCA. To explore this hypothesis, we studied albumin purified from the plasma of patients in four subject groups: SCA and PH, SCA steady-state without PH, IPAH, and normal volunteers. Purified albumin was analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). Using MALDI-TOFMS, we identified that an ion corresponding to a malondialdehyde (MDA)-modified albumin peptide was differentially present in patients with IPAH and PH of SCA. These results were confirmed by dot-blotting and Western analysis. We localized the site of MDA modification to albumin residue K159 using LC/MS/MS. Thus, we have identified an MDA modification of serum albumin that appears to be a common link between PH of SCA and IPAH. This finding supports the notion that oxidative stress modulates the pathogenesis of PH of SCA and suggests that this and other post-translational modifications may be important biomarkers of disease. 相似文献
3.
Predoana Luminita Atkinson Irina Karaj Dániel Attila Odhiambo Vincent Otieno Bakos László Péter Nagyné Kovács Teodóra Pandele-Cusu Jeanina Petrescu Simona Rusu Adriana Szilágyi Imre M. Pokol György Zaharescu Maria 《Journal of Thermal Analysis and Calorimetry》2021,143(4):2893-2900
Journal of Thermal Analysis and Calorimetry - In the literature data, several papers reported the synthesis by various chemical or physical methods of the SrCu2O2 (SCO) having possible applications... 相似文献
4.
P. K. Kamweru F. G. Ndiritu T. K. Kinyanjui Z. W. Muthui R. G. Ngumbu P. M. Odhiambo 《Journal of Macromolecular Science: Physics》2013,52(5):817-827
Plastic bags, mostly made of polyethylene, cause pollution as solid waste due to their nondegradable nature. Accelerated degradation, as a solution to mitigate the menace, can be achieved through moisture enhanced photolysis. This study evaluated the effect of three relative humidity environments, i.e., 25%, 40%, and 60% RH, at a constant temperature of 55°C. The effect was studied for ultraviolet (UV) irradiated and nonirradiated samples of polyethylene (PE) films processed under conventional ways. Photodegradation was initiated using ultraviolet irradiation in the ranges (200–300) nm and (300–400) nm for two hours and the effects of subsequent humidity treatment analyzed. Dynamic mechanical analysis was used to measure the dynamic storage modulus to monitor degradation. For nonirradiated samples, there was essentially no change in storage modulus at the three relative humidity environments after 550 hrs. Irradiation in the (300–400) nm range showed faster degradation than for the (200–300)nm range with the highest drop in storage modulus being 67% after 550 hrs. Raising the humidity from 25% to 40% and 60% RH resulted in 41%, 62%, and 67% drop of storage modulus, respectively, at the 550 hrs. 相似文献
5.
Thong Le Ba Ahmed Baqer Mohammed Saad Kamel Gyula Grf Vincent Otieno Odhiambo Somchai Wongwises Lezsovits Ferenc Imre Mikls Szilgyi 《Molecules (Basel, Switzerland)》2022,27(3)
Halloysite nanotube (HNT) which is cheap, natural, and easily accessible 1D clay, can be used in many applications, particularly heat transfer enhancement. The aim of this research is to study experimentally the pool boiling heat transfer (PBHT) performance of novel halloysite nanofluids at atmospheric pressure condition from typical horizontal heater. The nanofluids are prepared from halloysite nanotubes (HNTs) nanomaterials-based deionized water (DI water) with the presence of sodium hydroxide (NaOH) solution to control pH = 12 to obtain stable nanofluid. The nanofluids were prepared with dilute volume concentrations of 0.01–0.5 vol%. The performance of PBHT is studied via pool boiling curve and pool boiling heat transfer coefficient (PBHTC) from the typical heater which is the copper horizontal tube with a thickness of 1 mm and a diameter of 22 mm. The temperatures of the heated tube surface are measured to obtain the PBHTC. The results show an improvement of PBHTC for halloysite nanofluids compared to the base fluid. At 0.05 vol% concentration, HNT nanofluid has the best enhancement of 5.8% at moderate heat flux (HF). This indicates that HNT is a potential material in heat transfer applications. 相似文献
6.
Ruth A. Odhiambo Gerald K. Muthakia Stanley M. Kagwanja 《Transition Metal Chemistry》2012,37(5):431-437
Mo(NO)T p * Cl2 (T p * ?=?3,5-dimethyl pyrazole) when reacted with m-functionalized Fe(III) Schiff base complexes; the Schiff base ligands being derived from condensation of 2,4-dihydroxybenzaldehyde or salicylaldehyde with a variety of ??,??-diamines [1,2-C6H4(NH2)2, NH2(CH2) n NH2; n?=?2?C4] affords bimetallic complexes containing two potential reduction centers. The compounds were characterized by physicochemical and spectroscopic methods. It is shown that as the polymethylene carbon chain of the Schiff base backbone increases, the physicochemical and spectroscopic properties also change gradually. Electrochemical data show that the m-functionalized complexes reduce at potentials less cathodic than their p-substituted analogues. It is also shown that the redox potentials are solvent dependent. 相似文献
1