Kenneth Gitiye - Academia.edu (original) (raw)

Papers by Kenneth Gitiye

The red ellipse worked as a cue for keeping gaze (every 4 secs) within one of the region... more The red ellipse worked as a cue for keeping gaze (every 4 secs) within one of the regions containing only one of the two faces. A trial began with a neutral blank gray image, equiluminant to the average brightness of the successive faces image, and serving as a baseline image to compute pupil changes in an event-related manner (by subtracting the mean pupil diameter during viewing of each baseline image from the mean pupil diameter when subsequently attending a face stimulus).</p

Error bars represent Standard Errors. In the inlay the face regions corresponding to eac... more Error bars represent Standard Errors. In the inlay the face regions corresponding to each AOI (the colors are arbitrary) are shown superimposed to the “African” face.</p

Analyses of choices in the lightness comparison task.</p

Error bars represent Standard Errors.</p

Because the perceived difference in skin tone persists even after the observer is inform... more Because the perceived difference in skin tone persists even after the observer is informed that the two face images deliver the same average intensity of light to the eyes, such a visual demonstration has been included in the “library” of optical illusions and it is often referred to as the Face Race Illusion (source: “Distortions in the perceived lightness of faces: the role of race categories,” by Daniel T. Levin and Mahzarin R. Banaji, 2006, Journal of Experimental Psychology: General, vol. 1358:4).</p

Brighter regions indicate more luminance in the African’s than the European’s facial ima... more Brighter regions indicate more luminance in the African’s than the European’s facial image.</p

Bars represent standard errors.</p

Journal of Advanced Psychology

Purpose: Assessment on the effect of executive functioning disorders in vulnerability to depressi... more Purpose: Assessment on the effect of executive functioning disorders in vulnerability to depression among adolescents in secondary schools in Meru County, Kenya. Methodology: The study adopted descriptive research design to gather both qualitative and quantitative data. Secondary schools were sampled using proportionate stratified sampling method to obtain 27 secondary schools in Meru County. The principals/deputy principals and counseling teachers were interviewed. Mathematics and English teachers answered a questionnaire, while the students were assessed using depression tool. Pretesting of data collecting instruments was done in 3 schools in the neighboring Tharaka Nithi County; Ikuu girls’ secondary school, Chuka boys’ high school and Ndagani mixed day secondary school. Data was analyzed using descriptive statistics such as frequency, percentage and median. Additionally, inferential statistics such as linear regression and multiple regressions inclusive of regression coefficient...

Geologien i Nordsjøen består i stor grad av sedimentære bergarter som har bygget seg opp over fle... more Geologien i Nordsjøen består i stor grad av sedimentære bergarter som har bygget seg opp over flere hundre millioner år. Disse er blitt dannet ved at sand og leirpartikler er blitt presset sammen, knust og sementert til stein under høyt trykk og temperatur. I denne prosessen bevares som regel noe mellomrom mellom kornene, og det er ikke uvanlig at disse væskefylte porene kan utgjøre 20–30 prosent av steinens volum.

Energies, 2021

A comprehensive monitoring program is an integral part of the safe operation of geological CO2 st... more A comprehensive monitoring program is an integral part of the safe operation of geological CO2 storage projects. Noble gases can be used as geochemical tracers to detect a CO2 anomaly and identify its origin, since they display unique signatures in the injected CO2 and naturally occurring geological fluids and gases of the storage site complex. In this study, we assess and demonstrate the suitability of noble gases in source identification of CO2 anomalies even when natural variability and analytical uncertainties are considered. Explicitly, injected CO2 becomes distinguishable from shallow fluids (e.g., subsea gas seeps) due to its inheritance of the radiogenic signature (e.g., high He) of deep crustal fluids by equilibration with the formation water. This equilibration also results in the CO2 inheriting a distinct Xe concentration and Xe/noble gas elemental ratios, which enable the CO2 to be differentiated from deep crustal hydrocarbon gases that may be in the vicinity of a storag...

Journal of Geophysical Research: Solid Earth, 2020

Fracture stiffness and flow properties have been measured in the laboratory using naturally fract... more Fracture stiffness and flow properties have been measured in the laboratory using naturally fractured fault rock samples from the Little Grand Wash fault, Utah, USA. We compare fracture closure and related flow change during isotropic loading of two fractures which have been subject to various amounts of paleoreactive flow. The two tested fractures are described as (i) a small-aperture fracture (0.1 mm) with negligible geochemical alterations of the fracture surface and (ii) a large-aperture fracture (0.53 mm) where precipitates are observed on the fracture surface. X-ray imaging is used for quantification of fracture aperture and fracture surface contact distribution. The petrographical characterization using scanning electron microscopy and X-ray powder diffraction is performed pretest and describes burial and uplift diagenesis as well as pulses of reactive fluid flow within the fault. The stress-dependent flow and deformation experiment provides new data on fracture stiffness and flow for naturally developed fractures in siliciclastic rock. Fracture stiffness is found to be highest for the small-aperture fracture due to its high-fracture contact ratio and well-developed surface mating during closure. For the naturally altered and rougher, large-aperture fracture, fracture stiffness is lower and a highly stress dependent decay in flow is observed during initial closure. The results illustrate that a natural fracture with high contact ratio and well-mated surfaces will close during loading, whereas a fracture associated with high flow rates and affected by previous geochemical alteration maintains a high flow rate compared to the host rock during similar loading.

Energy Procedia, 2017

Understanding geodynamic reservoir and seal performance is important in order to ensure safe stor... more Understanding geodynamic reservoir and seal performance is important in order to ensure safe storage of CO 2. In Utah leakage from natural gas reservoirs through sandstones and along faults may be observed as diagenetic alteration traces. Aeolian deposits, stained red by iron oxides, have commonly been bleached by reducing fluids of varying density. At the study site, bleaching is observed within and along the base of a low-permeability, regionally sealing unit; the lowermost Carmel Formation. Compactional stress during progressive deformation in the San Rafael monocline induced pressure gradients driving flow through the seal and towards venting fractures. Chemical transport processes are interpreted to be a combination of diffusion and advection. Capillary barriers may be overcome as transient in situ pressures and temperatures affecting fluid properties. The same geological unit may behave as a conduit during some parts of burial/uplift-history and as a sealing unit at other times.

Recent experimental results have confirmed a possible reduction in the GT + strengths of pfshell ... more Recent experimental results have confirmed a possible reduction in the GT + strengths of pfshell nuclei. These proton-rich nuclei are of relevance in the deflagration and explosive burning phases of Type Ia supernovae. While prior GT strengths result in nucleosynthesis predictions with a lower-than-expected electron fraction, a reduction in the GT + strength can result in an slightly increased electron fraction compared to previous shell model predictions, though the enhancement is not as large as previous enhancements in going from rates computed by Fuller, Fowler, and Newman based on an independent particle model. A shell model parametrization has been developed which more closely matches experimental GT strengths. The resultant electroncapture rates are used in nucleosynthesis calculations for carbon deflagration and explosion phases of Type Ia supernovae, and the final mass fractions are compared to those obtained using more commonly-used rates.

The last few years there has been broad attention towards finding permanent storage options for C... more The last few years there has been broad attention towards finding permanent storage options for CO2. The Norwegian continental margin holds great potential for storage in saline aquifers. Common for many of these reservoir candidates, however, is that geological data are sparse relative to thoroughly mapped hydrocarbon reservoirs in the region. Scenario modeling provides a method for estimating reservoir performances for potential CO2 storage sites and for testing injection strategies. This approach is particularly useful in the evaluation of uncertainties related to reservoir properties and geometry. In this study we have tested the effect of geological heterogeneities in the Johansen Formation, which is a laterally extensive sandstone and saline aquifer at burial depths of 2 - 4 km, proposed as a suitable candidate for CO2 storage by Norwegian authorities. The central parts of the Johansen Formation are underlying the operating hydrocarbon field Troll. In order not to interfere wi...