Physics

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Concentration of Inorganic Contaminants in Shallow Borehole Water in Chuka Sub-County, Kenya
(Journal of Chemical, Biological and Physical Sciences, 2020-11-24) M. Rugendo, Edith; C. Njagi, Eric; Ombaka, Ochieng
Groundwater from shallow aquifers is an important source of portable water in Chuka Sub-County. However, most shallow boreholes in Chuka Sub-County are undocumented and susceptible to contamination by both geogenic and anthropogenic activities. This study was conducted to evaluate the quality of shallow boreholes water in Chuka Sub-County. Samples were collected from twenty boreholes in Chuka Sub County during the dry and wet seasons. The temperature, pH and conductivity were determined in situ using a meter. The concentration of cations was determined using ICP-MS. The concentrations of anions were determined using standard APHA analytical methods. The temperatures and conductivities of borehole waters were within the limits set by KEBS and WHO. The pH of water in most boreholes during the wet season was within the limits set by KEBS and WHO for portable water. However, borehole water at Karandini (T15) was highly acidic (pH of 3.95) during the wet season. During the dry season, borehole waters were slightly acidic (4.42 - 6.44) except for the borehole at Ndagani market (T11), whose water was alkaline (pH = 8.75). The concentrations of trace and toxic cations and anions (NO3 - , SO4 2- , Cl and PO4 3- ) were within the limits set by KEBS and WHO. However, the concentration of nitrate in several boreholes during the dry season was within the range that cause chronic health effects. Groundwater from most boreholes in Chuka Sub-County is generally safe for domestic uses but require regular monitoring for quality.
Massive Protocluster of a Periodic Maser Source G188.95+0.89
(Oxford University Press on behalf of Royal Astronomical Society, 2021-07-14) M. M., Mutie; J. O., Chibueze; K., El Bouchefry; G. C., MacLeod; J., Morgan; P., Baki
We report the results of ongoing monitoring of the 6.7 GHz CH3OH masers associated with G188.95+0.89. In these observations, five features are periodically varying and at least two exhibit evidence of velocity drifts. It is not clear the cause of these velocity drifts. The spectra have varied significantly since detection in 1991. The 11.45 km s−1 feature has decreased exponentially from 2003. Complementary ALMA 1.3-mm continuum and line observational results are also presented. Eight continuum cores (MM1–MM8) were detected in G188.95+0.89. We derived the masses of the detected cores. G188.95+0.89 MM2 was resolved into two continuum cores (separated by 0.1 arcsec) in ALMA band 7 observations. Also, CH3OH (4(2, 2)-3(1, 2)) thermal emission associated with MM2 is double peaked. We propose the presence of multiple (at least binary) young stellar objects in MM2. SiO emission exhibits a bow-shock morphology in MM2 while strong emission of 12CO at the east and west of MM2 suggests the presence of an east–west bipolar outflow.
Thermal Conductivities of Selected Solid Waste Materials Determined Using Lees’ Disc Method
(International Journal of Research Publications (IJRP.ORG), 2020-04-02) Chepkorir, Doreen; Kamweru Kuria, Paul
In this study, the coefficients of thermal conductivities have been determined. The goal was to find out the best insulator among the recyclable and locally available materials which can be adopted for use to replace the existing thermal insulation. Rice husks, dry grass, sawdust and old/used newspapers have been studied in this study using Lees’ disc method. The results showed that grass can do best as an insulating material though all the samples can be used as insulators. They all have low thermal conductivities. The coefficient of thermal conductivities ranged from 𝟎. 𝟐𝟐𝟔 𝑾/𝒎𝑲 for grass, 𝟎. 𝟐𝟕 𝑾/𝒎𝑲 for saw dust, 𝟎. 𝟓𝟎 𝑾/𝒎𝑲 for rice husks and 𝟏. 𝟗𝟑 𝑾/𝒎𝑲 for newspaper cut-outs. Due to their local abundance, and no much competing commercial interest, we recommend the studied materials as suitable thermal insulators.
Calorific Value and Moisture Content Of Selected Solid Wastes at Chuka University
(IJRP.ORG., 2020-04-02) Kanogo Thuo, Daniel; Kamweru Kuria, Paul
Solid waste, which typically consists of metals, plastics, glasses, paper, wood, and organics, is generated and accumulated due to human day to day activities. The waste often leads to ecological pollution unless an appropriate solid waste management system is applied. Remarkably, solid waste can be channeled into a very useful form to generate energy leading to the reduction of the use of fossils fuels which are rapidly becoming limited, reduction of wastes in dumping sites and also be an additional source of energy. For such ventures though, the amount of energy that can be recovered from burning solid waste needs to be determined. In this work, solid waste samples were collected, classified, sundried, powdered and sieved using a sieve of size 500µm. The percentage moisture content of fruits waste, animal dung, and yard trimming & vegetables were found to be 33, 48, and 55 % respectively. The fruits waste had the highest calorific value of 104,130.91J/g, followed by the animal dung with 95,804.13 J/g and the least was yard trimming and vegetables with 95,100.39 J/g. The average specific energy content is 98345.14 J/g.
Correlation Between Electromagnetic Wave Equation And Einstein Theory Of Relativity In Derivation Of Schrödinger Equation And Hilbert Space Operators
(Journal of Multidisciplinary Engineering Science Studies (JMESS), 2020-03) Mbatha M., Elizabeth; Musundi W., Sammy; Kamweru K., Paul
Operators in Hilbert space have properties which are useful in the study of mathematical abstract areas such as approximation theory, Banach Fixed point theory, the spectral theory as well as Quantum Mechanics. Schrödinger equation is a fundamental entity with many applications in Quantum Mechanics. This equation was initially derived by applying the knowledge of electromagnetic wave function and Einstein theory of relativity. Later, it was derived by applying the knowledge of Newtonian mechanics. It was also derived by extending the wave equation for classical fields to photons and simplified using approximations consistent with generalized non-zero rest mass. However, from the existing literature no study has been done on deriving Schrödinger equation using properties of Hilbert space operators. In this study, Hilbert space operators that include unitary operators, self adjoint operators and compact operators, norms of linear operators, Hilbert Schmidt operator, normal operators together with Lebesque Integral, Neumann Integral and spectrum are used in place of the existing concepts of electromagnetic wave function, Einstein theory of relativity and approximation consistent with generalized non zero mass to derive the Schrödinger equation. The derivation of Schrödinger equation and its application using Hilbert space operators enhances a better understanding of the concept of Schrödinger equation. The results of this work can further find use in quantum mechanics as well as in mathematical operator theory.
Effect Of Electric Field In The Soil On The Germination And Growth Rate Of Rosecoco Beans Plant
(Research journali, 2020-01) Evance, Odiwour; Stanislous, Mutunga; Kanyago, Gitonga Anthony; Kuria, Kamweru Paul
This study shows the effect of electric field on the germination and growth of bean plants. Rose coco beans was chosen because its growing rate is fast and it’s a common food plant. An electric field was applied in the soil and is expressed in terms of electric energy density created within pairs of copper plates with different polarities (-ve and +ve) forming electric impulse with 9V DC current at room conditions for 6 hours a day. A control sample was treated similarly except with no electric field applied. The growth parameters investigated were the germination rate and the heights of the stems and were recorded after every 4 days. The obtained results shows a positive effect on the germination of about 27.8% positive deviation and improved height gain rate of 32.1%. This data shows that electric field could have an effect of awakening seed dormancy which result to faster germination, and positively influence other biochemical processes resulting to higher growth rates.
Adsorption of Lead (II) Ions from Aqueous Solutions Using Mangroves Roots (Rhizophora Mucronata) Charcoal-Carbon Nanotubes Nanocomposite
(Journal of Multidisciplinary Engineering Science and Technology (JMEST), 2021) Ngugi, Fidelis; Mwangi, Joel; Njagi, Eric; Ombaka, Ochieng
Providing clean and affordable water to meet human needs is a grand challenge of the 21st century. Worldwide, water supply struggles to keep up with the fast growing demand, which is exacerbated by population growth, global climate change, and water quality deterioration. Nanotechnology holds great potential in advancing water treatment to improve water treatment efficiency. In this study, Mangrove Roots Charcoal and Carbon Nanotubes (MRCCNTs) nanocomposite was synthesized and utilized as a novel adsorbent for the removal of lead ions from aqueous solutions. The efficacy of MRC-CNT nanocomposites was investigated in batch mode which involved the effects of pH, temperature, concentration of the lead ions, adsorbent mass and contact time on adsorbates removal. Characterization of the adsorbent was carried out by Scanning Electron Microscopy (SEM) to observe the morphology of the adsorbent and surface area analysis and Energy Dispersive X-ray spectroscopy (EDX) to determine the elemental composition of the adsorbent. Adsorption isotherm models and adsorption kinetic studies were used for data analysis. It was observed that the removal efficiency of Pb (II) ions depended on pH of solution and the maximum efficiency was noticed at pH 7 with adsorption capacity of 3.629 mg/g which was calculated by the Freundlich isotherm model. Kinetic studies were well suited and found in good agreement with pseudo-second order. The results indicated that MRC-CNT nanocomposites would be a promising adsorbent for adsorption of Pb (II) ions from aqueous solutions.
Adsorption of rhodamine b from aqueous solution using mangroves (Rhizophora mucronata) carbon nanotubes nanocomposites
(www.allsubjectjournal.com, 2021) Ngugi, Fidelis; Mwangi, Joel; Njagi, Eric; Ombaka, Ochieng
The use of dyes has increased dramatically and uncontrollably in last few decades. Different types of dyes are frequently employed in plastics, paper, cosmetics, leather, and textile industries for coloring purposes. These dyes are released in water as effluents, which are of low Biological Oxygen Demand (BOD) and high Chemical Oxygen Demand (COD). Some of these dyes also are toxic and carcinogenic in nature. This study report on the synthesis of Mangroves Roots-Carbon Nanotubes (MRC-CNT) nanocomposite as an adsorbent for efficient removal of Rhodamine B (Rh. B) dye from aqueous solution. Effect of contact time, initial concentration of dye, pH, and shaking speed on adsorption behavior were systematically investigated. The data obtained were fitted into Langmuir, Freundlich, Dubinin-Rudishkevich (D-R), and Temkin adsorption isotherm models for evaluation of adsorption parameters. The results indicated that MRC-CNT nanocomposite would be a promising adsorbent for adsorption of Rh. B from aqueous solutions.
Spectrophotometric Determination Of Copper (Ii) In Soil From Ahero Rice Irrigation Schemes Using Hydroxytriazene
(IOSR Journal of Applied Chemistry, 2020) Ombaka, Ochieng
A simple, rapid, sensitive and cost effective spectrophotometric technique for the determination of copper (II) using 3-hydroxy-3-m-tolyl-1-O-carboxyphenyltriazene has been reported. The complex formed was greenishyellow having stoichiometry of 1:1 (Cu (II): hydroxytriazene) at a pH range of 6.0-6.6. The measurements were carried out at a working wavelength of 405nm with a molar absorptivity of 2.8×104Lmol-1 cm-1and sandell’s sensitivity of 2.26ng/cm2 . Lambert –Beer’s law is obeyed over a range of 1.27-7.63mg/L of copper. The correlation coefficient of the standard calibration curve was 0.997. The complex formed between copper (II) and hydroxytriazene was greenish –yellow with composition of 1:1(Cu (II): hydroxytriazene). The relative standard deviation (n=10) for standard dilution of 635.46mgL-1 copper (II) was 0.92%. The change in Gibb’s free energy at 270Cwas determined using Purohit’s, Harvey and Manning’s method and found to be respectively. The study showed that, the following cations and anions do not interfere when present at equivalent amount of copper: Cl- ,Br- , CH3COO- , CO3 2- , PO4 3- ,SO4 2- , C2O4 2- , I- , S2O3 2- , NO2- , SO3 2- ,S2- ,HPO4 2- , F- , NO3 - , WO4 2- , MO7O24 6- , NH4 + , Na+ , k + , Ba2+ , Cd2+ , Mg2+ , Ca2+ . However, UO2+ , Mn2+ , Pb2+ , Hg2+ , Sn2+ , Th4+,ZrO2+,Co2+ , Zn2+, Ni2+ interferes with copper (II) determination at equivalent amount, hence the need for the masking agent. The present method was applied to the determination of copper (II) in agricultural soil samples.
NEW METALLOCHROMIC INDICATORS FOR COMPLEXOMETRIC TITRATION OF COPPER (II) IN PRESENCE OF INTERFERING SPECIES
(Life Science Informatics Publications, 2020-09) Ombaka, Ochieng
Six hydroxytriazenes has been introduced as a metallochromic indicator in the complexometric titration with EDTA and applied successfully to the titration of copper (II). A direct method of titration of Cu (II) with EDTA using these hydroxytriazenes has been proposed. The change of colour of the solution at the end point during titration was from yellow to green at a pH range of 5.5-6.0, 5.05-5.50, 5.0-5.5 for reagent number (i, ii, iii, vi), iv, v respectively. The titration can be performed at the temperature range of 25-60℃. The minimum concentration of copper (II) which can be titrated is as follows: 1.0 x 10−3 M Cu (II), 3.0 x 10−3M Cu (II), 5.0 x 10−3M Cu (II) when using reagent number (i, iii, v, vi), iv, ii respectively as metallochromic indicators. Interference studies of a number of cations and anions have been studied. Cl−, Br−, CH3COO−, PO4 3−, SO4 2−,C2O4 2−, S2O3 2−, NO3 −, SO3 −, S 2−, HPO4 2−, F −, NO3 −, WO4 2−,Mo2O24 6− , I −, NH4 +, Na+, K +, Ba2+, Hg2+, Mg2+, Ca2+ can be tolerated on the titration of Cu (II) up to tenfold excess. However, {U(vi), Sn(II), Zr(iv), Co(II), Zn(II), Ni(II)}, {Pb(II), Th(IV)}, {Mn(II), Cd(II)} interfered at equivalent amounts, fivefold excess, tenfold excess respectively.
Ab initio Investigation of the Structural and Electronic Properties of Alkaline Earth Metal - TiO2 Natural Polymorphs
(Hindawi Advances in Materials Science and Engineering, 2022) Mbae, J.K.; Muthui, Z.W.
Titanium (IV) oxide (TiO2) has gained much attention due to its application in technologies such as optoelectronics, electronics, sensors, photocatalysts, and sustainable energy generation. However, its optical absorption falls in the ultraviolet part of the electromagnetic spectrum, resulting in a low absorption ratio of solar light. In addition, rapid electron-hole recombination limits its photocatalytic activity. To extend the application range of TiO2, the structural and chemical properties can be modified by adding various dopants to tune its electronic structure for applications within a wider range of the solar energy spectrum and ideally extend towards the visible region, which forms the dominant part of the solar energy spectrum. In this study, the structural and electronic properties of three polymorphs of TiO2 have been studied using density functional theory (DFT) as implemented in the Quantum ESPRESSO simulation package. )e exchange-correlation potential has been treated with the generalised gradient approximation (GGA). Cationic substitution with non-toxic alkaline earth metal dopants Mg and Ca has been carried out with the aim of modifying the electronic structure of the polymorphs of TiO2. On 1–4% Mg and Ca cationic substitution, there is a slight expansion of the optimal unit cell volume and modulation of the band gap energy by raising the valence band maximum to higher energies. In addition, dopant inter and intra-band states are observed.
Determination of the Class TransitionTemperature and Modulus of PLA Films Using Dynamic Mechanical Analysis at C ° 50 and Amplitude of 10 µm
(2014-03) Muthui, Z. W. 1; Nderitu, F. G 2; Hussein, S. A. 3; Kamweru, P. K. Golicha 4; Ngumbu, R. 5
Polylactic acid (PLA) is an environment friendly biodegradable thermoplastic produced by micro organism synthesis through the fermentation of starch. It can be used in the manufacture of thermoplastic films used to produce packaging material in place of those produced from fossil fuels. Its introduction in the production of packaging material will reduce the consumption of petroleum, which releases Carbon (IV ) Oxide, a greenhouse emission, unburned carbon fragments and other compounds that give rise to smog and air pollution on burning. It is also compostable, aiding solid waste management. In this study the mechanical properties of PLA were determined over a temperature and amplitude range in order to establish whether it can be used in the production of packaging material for single use purposes and of disposable items. The storage ( (ω) ' E ) and loss ( (ω) '' E ) moduli as well as the Loss Tangent ( tanδ ) and the Glass Transition Temperature (Tg ) of PLA films were determined using the Dynamic mechanical analyzer (DMA) model 2980, used in the Multistrain mode. The storage modulus of PLA at C ° 50 and amplitude of 10 µmwas found to be 2220.00 MPa. The loss modulus for PLA was found to be 112.90 MPa at the same temperature and amplitude. Consequently, the elastic modulus E of PLA was found to be 2222.87 MPa. This indicates that PLA is strong and tough at this temperature. From the peak of the loss modulus graph the Tg of PLA was found to be C ° 65 .Tgfrom the variation of loss tangent with temperature occurred at C ° 3.74 .
Geophysical structure of Homa Hills Geothermal field based on Gravity and magnetic survey
(2011) Adero, B. Otieno; Odek, A.; Ambusso, W.; Gitonga, G. J.
Gravity and ground magnetic surveys were conducted over an area of 76 Km 2 in order to investigate thermal structures responsible for geothermal manifestations such as hot springs in the Homa Hills geothermal prospect. The two surveys show that the southern part of the prospect has a potential for geothermal resource and should be investigated further to establish presence of an exploitable hydrothermal system. The magnetic survey indicates higher demagnetization in this part of the field compared to other parts of the field. The gravity survey is relatively sharp with a classic dome shaped profile associated with a large shallow dike
2D-Euler Deconvolution and Forward Modeling of Gravity Data of Homa-Hills Geothermal Prospect, Kenya
(2013) Odek, O. 1; Otieno, A.B. 1; Ambusso, W.J. 1; Githiri, J. G 2
In order to fully assess the potential of Homa Hills Geothermal prospect, the heat source which is one of the main features of a geothermal system had to be located based on its perturbation on the gravity field. Ground gravity survey was conducted in an area covering about 76 km2 and the data processed to remove all other effects which are not of geological interest. Qualitative interpretation was attempted and cross sections drawn across the anomalous areas on the complete Bougu er anomaly map. Quantitative interpretation attempted involved both Euler Deconvolution and 2 ‐D Forward modelling. The parameters obtained from Euler Deconvolution were used as the start up parameters for 2 ‐D Forward modeling. Well clustered Euler solutions were obtained at a shallow depth of approximately 200‐750 m which is consistent with the modeled shallow dike like intrusive probably of carbonatite origin
2D-Euler Deconvolution and Forward Modeling of Gravity Data of Homa-Hills Geothermal Prospect, Kenya
(2014) Odek, A.; Otieno, A. B.; Githiri, Jg
In order to fully assess the potential of Homa Hills Geothermal prospect, the heat source which is one of the main features of a geothermal system had to be located based on its perturbation on the gravity field. Ground gravity survey was conducted in an area covering about 76 km2 and the data processed to remove all other effects which are not of geological interest. Qualitative interpretation was attempted and cross sections drawn across the anomalous areas on the complete Bouguer anomaly map. Quantitative interpretation attempted involved both Euler Deconvolution and 2‐D Forward modelling. The parameters obtained from Euler Deconvolution were used as the start up parameters for 2‐D Forward modeling. Well clustered Euler solutions were obtained at a shallow depth of approximately 200‐750 m which is consistent with the modeled shallow dike like intrusive probably of carbonatite origin.
Inversion of Gravity data of Nyabisawa-Bugumbe area of Migori greenstone belt, Kenya
(2018) Odek, Antony
Migori greenstone belt is one of the major mineral prospects in Kenya, major mining activities are currently conducted by the local artisans using open cast methods. In order to subject the prospect to industrial use, a good understanding of the geophysical features in the subsurface which are likely to control the distribution of minerals is necessary. In this study, a 2-D lithoprediction model of Nyabisawa-Bugumbe area was developed from geologically constrained inversion of gravity field data. The measured gravity field data were subjected to cleaning process to remove perturbations which were not of geophysical interest, and later enhanced by removing long wavelength anomalies which are as a result of regional trend. The density variations were then inverted for the geometrical parameters of the model. Gravity high trending NW-SE around Nyabisawa, Kirengo towards Nyambeche was delineated. The gravity high is bounded by two major faults along rivers Migori and Munyu. Integrating the 2-D inversion of gravity data and the geology of the area, the gravity field perturbation is associated with banded iron formations.
Near Surface Anomaly Depth Estimation Using Downward Continuation
(2018-10) Odek, Antony
Depth estimation in gravity survey is very important in mineral prospecting. It does not only inform the choice of the optimal point for mineral exploration but also very important in analyzing economical viability of the mines. A number of depth determination techniques ranging from empirically derived formulae to modern automated analysis of gravity data have been developed. In this study, downward continuation filtering technique has been used to filter the near surface perturbations on the gravity field which are suspected to be as a result of minerals. The measured total magnetic field data of Migori greenstone belt was first subjected to cleaning process to remove the effects which are not of geophysical interest, and later enhanced by removing long wavelength anomalies which are as a result of regional magnetic trend. The complete Bourguer anomaly was then subjected to downward continuation at depths of 0 m, 500 m, 1000 m and 1500 m. The near surface features seem to be filtered at a depth of 1500 m, leaving the deeply seated features. This result with the available geological information is a good indicator of the possible depth of the near surface anomaly causative bodies. The result was further improved by integrating it with the geochemical analysis of rock samples. Shallow gravity structures are mapped from the surface to a limiting depth of approximately 1,500 m. These structures agree well with the geochemical results that shows presence of minerals and known geology of the area.
Ground water prospecting using Self Potential (SP) in Mungoni area of TharakaNithi, Kenya
(2018) Odek, A. 1; Kiarie, B. 1
Self-potential method is based on the surface measurement of natural potential resulting from electrochemical reactions in the subsurface. It does not require electric currents to be injected into the ground as in the resistivity and induced potential methods. This method has been used in base metal exploration to detect presence of massive ore bodies, in contrast to the IP method which is used predominantly to investigate disseminated ore bodies. One of the most important applications of self-potential is detection of fluid flow thereby making it a complimentary technique in field applications involving fluid flow, fracture leakage detection and pollutant migration, among others. The study was carried out with the aim of investigating the underground water around Mungoni area, Tharaka Nithi, Kenya. The population within this area is growing rapidly due to the increase in the number of learning institutions; this poses a high demand for clean water for domestic use and for agricultural use. The data was collected using resistivity Terrameter and a GPS probe for recording the space coordinates of the data stations. The data analysis was conducted using Surfer 11 computer application software. From the data interpretation it was concluded that groundwater is present in Mungoni area and extents from a depth of 100 meters to 180 meters and is reliable for commercial use.
Power spectral analysis and edge detection of magnetic data of Migori greenstone belt, Kenya.
(2020-04) Odek, Antony1; Githiri, John 2; K’Orowe, Maurice 2; Ambusso, Willis 3
With the continuous extraction of minerals in Migori greenstone belt, exploration is currently evolving from surface based exploration to subsurface exploration. This necessitates a good understanding of the geophysical features in the subsurface which are likely to have a direct bearing on the distribution of minerals. In this study, the measured total magnetic field data was subjected to cleaning process to remove perturbations which are not of geophysical interest, and later enhanced by removing long wavelength anomalies which are as a result of regional magnetic trend. Power spectral analysis of geologically constrained magnetic intensity field data was then conducted, in order to obtain the limiting depth of the anomaly causative bodies. Edge detection techniques were then employed on the delineated magnetic field intensity anomalies trending WNW-ESE along the belt. The power spectral analysis shows bodies of high magnetic field intensity from the ground surface to a limiting depth of approximately 400 m. The anomalous region is bounded by two major faults along rivers Migori and Munyu. Integrating the 2-D inversion of magnetic field intensity data and the geology of the area, the magnetic field perturbation is associated with banded iron formations which act as the host for the minerals.
Study of Temperature and UV wavelength Range Effects on degradation of Photo Irradiated polyethylene films using DMA
(2011-06-09) Kamweru, P. K.; Ndiritu, F. G.; Kinyanjui, T. K.; Muthui, Z. W.; Ngumbu, R. G.; Odhiambo, P.M.
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.

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