Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Harry J. Khamis is active.

Publication


Featured researches published by Harry J. Khamis.


FEMS Microbiology Ecology | 2011

Distal gut microbiota of adolescent children is different from that of adults

Richard Agans; Laura Rigsbee; Harshavardhan Kenche; Sonia Michail; Harry J. Khamis; Oleg Paliy

Human intestinal microbiota plays a number of important roles in human health and is also implicated in several gastrointestinal disorders. Although the diversity of human gut microbiota in adults and in young children has been examined, few reports of microbiota composition are available for adolescents. In this work, we used Microbiota Array for high-throughput analysis of distal gut microbiota in adolescent children 11-18 years of age. Samples obtained from healthy adults were used for comparison. Adolescent and adult groups could be separated in the principal components analysis space based on the relative species abundance of their distal gut microbiota. All samples were dominated by class Clostridia. A core microbiome of 46 species that were detected in all examined samples was established; members of genera Ruminococcus, Faecalibacterium, and Roseburia were well represented among core species. Comparison of intestinal microbiota composition between adolescents and adults revealed a statistically significantly higher abundance of genera Bifidobacterium and Clostridium among adolescent samples. The number of detected species was similar between sample groups, indicating that it was the relative abundances of the genera and not the presence or absence of a specific genus that differentiated adolescent and adult samples. In summary, contrary to the current belief, this study suggests that the gut microbiome of adolescent children is different from that of adults.


The American Journal of Gastroenterology | 2012

Quantitative Profiling of Gut Microbiota of Children with Diarrhea-Predominant Irritable Bowel Syndrome

Laura Rigsbee; Richard Agans; Vijay Shankar; Harshavardhan Kenche; Harry J. Khamis; Sonia Michail; Oleg Paliy

OBJECTIVES:Human intestinal microbiota has a number of important roles in human health and is also implicated in several gastrointestinal disorders. The goal of this study was to determine the gut microbiota in two groups of pre- and adolescent children: healthy volunteers and children diagnosed with diarrhea-predominant irritable bowel syndrome (IBS-D).METHODS:Phylogenetic Microbiota Array was used to obtain quantitative measurements of bacterial presence and abundance in subjects’ fecal samples. We utilized high-throughput DNA sequencing, quantitative PCR, and fluorescent in situ hybridization to confirm microarray findings.RESULTS:Both sample groups were dominated by the phyla Firmicutes, Bacteroidetes, and Actinobacteria, which cumulatively constituted 91% of overall sample composition on average. A core microbiome shared among analyzed samples encompassed 55 bacterial phylotypes dominated by genus Ruminococcus; members of genera Clostridium, Faecalibacterium, Roseburia, Streptococcus, and Bacteroides were also present. Several genera were found to be differentially abundant in the gut of healthy and IBS groups: levels of Veillonella, Prevotella, Lactobacillus, and Parasporobacterium were increased in children diagnosed with IBS, whereas members of Bifidobacterium and Verrucomicrobium were less abundant in those individuals. By calculating a nonparametric correlation matrix among abundances of different genera in all samples, we also examined potential associations among intestinal microbes. Strong positive correlations were found between abundances of Veillonella and both Haemophilus and Streptococcus, between Anaerovorax and Verrucomicrobium, and between Tannerella and Anaerophaga.CONCLUSIONS:Although at the higher taxonomical level gut microbiota was similar between healthy and IBS-D children, specific differences in the abundances of several bacterial genera were revealed. Core microbiome in children was dominated by Clostridia. Putative relationships identified among microbial genera provide testable hypotheses of cross-species associations among members of human gut microbiota.


The ISME Journal | 2015

The networks of human gut microbe–metabolite associations are different between health and irritable bowel syndrome

Vijay Shankar; Daniel Homer; Laura Rigsbee; Harry J. Khamis; Sonia Michail; Michael L. Raymer; Nicholas V. Reo; Oleg Paliy

The goal of this study was to determine if fecal metabolite and microbiota profiles can serve as biomarkers of human intestinal diseases, and to uncover possible gut microbe–metabolite associations. We employed proton nuclear magnetic resonance to measure fecal metabolites of healthy children and those diagnosed with diarrhea-predominant irritable bowel syndrome (IBS-D). Metabolite levels were associated with fecal microbial abundances. Using several ordination techniques, healthy and irritable bowel syndrome (IBS) samples could be distinguished based on the metabolite profiles of fecal samples, and such partitioning was congruent with the microbiota-based sample separation. Measurements of individual metabolites indicated that the intestinal environment in IBS-D was characterized by increased proteolysis, incomplete anaerobic fermentation and possible change in methane production. By correlating metabolite levels with abundances of microbial genera, a number of statistically significant metabolite–genus associations were detected in stools of healthy children. No such associations were evident for IBS children. This finding complemented the previously observed reduction in the number of microbe–microbe associations in the distal gut of the same cohort of IBS-D children.


Journal of Applied Statistics | 2000

The two-stage i -corrected Kolmogorov-Smirnov test

Harry J. Khamis

Abstract The delta-corrected Kolmogorov-Smirnov test has been shown to be uniformly more powerful than the classical Kolmogorov-Smirnov test for small to moderate sample sizes. However, the delta-corrected test consists of two tests, leading to a slight inflation of the experimentwise type I error rate. The critical values of the delta-corrected test are adjusted to take into account the two-stage nature of the test, ensuring an experimentwise error rate at the nominal level. A power study confirms that the resulting so-called two-stage delta-corrected test is uniformly more powerful than the classical Kolmogorov-Smirnov test, with power improvements of up to 46 percentage points.


The Condor | 1990

Statistical Analysis of a Problem Data Set: Correlated Observations

Kathleen G. Beal; Harry J. Khamis

ANDERSON, D. R. 1975. Population of the Mallard. V. Temporal and geographic estimates of survival, recovery, and harvest rates. U.S. Fish and Wildl. Serv. Res. Publ. No. 125. ANDERSON, M. G., R. D. SAYLOR, AND A. D. AFTON. 1980. A decoy trap for diving ducks. J. Wildl. Manage. 44:217-219. BLOHM, R. J. 1978. Migrational homing of male Gadwalls to breeding grounds. Auk 95:763-766. COocH, G. 1953. Techniques for mass capture of flightless Blue and Snow Geese. J. Wildl. Manage. 17:460-465. CUMMINGS, G. E., AND O. H. HEwITT. 1964. Capturing waterfowl and marsh birds at night with light and sound. J. Wildl. Manage. 29:120-126. DoTr, H. A., AND R. J. GREENWOOD. 1974. Improved nasal-saddle marker for Mallards. J. Wildl. Manage. 38:938-939. DWYER, T. J., S. R. DERRICKSON, AND D. S. GILMER. 1973. Migrational homing by a pair of Mallards. Auk 90:687. HOCHBAUM, H. 1944. The Canvasback on a prairie marsh. American Wildlife Institute, Washington, DC.


Journal of Statistical Planning and Inference | 1990

The δ-corrected Kolmogorov-Smirnov test for goodness of fit

Harry J. Khamis

Abstract The empirical distribution function used in the classical Kolmogorov-Smirnov test is redefined in such a way that it becomes a function of a parameter called delta. Monte Carlo simulations are conducted for small sample sizes (n≤25) in order to determine those values of delta that lead to improvements in power. A goodness-of-fit test procedure is proposed as a replacement to the classical Kolmogorov-Smirnov test. Simulation results indicate that the size of the test is not affected by delta, and that the proposed test procedure has power that is at least as high as the classical Kolmogorov-Smirnov test, and in many instances the power improvement is very substantial.


Communications in Statistics - Simulation and Computation | 1984

Modified Kolmogorov-smirnov tests of goodness of fit

H. Leon Harter; Harry J. Khamis; Richard E. Lamb

The Kolmogorov-Smirnov (K–S) one-sided and two-sided tests of goodness of fit based on the test statistics D+ n D− n and Dn are equivalent to tests based on taking the cumulative probability of the i–th order statistic of a sample of size n to be (i–.5)/n. Modified test statistics C+ n, C− n and Cn are obtained by taking the cumulative probability to be i/(n+l). More generally, the cumula-tive probability may be taken to be (i−δ)/(n+l−2δ), as suggested by Blom (1958), where 0 less than or equal δ less than or equal .5. Critical values of the test statis-tics can be found by interpolating inversely in tables of the proba-bility integrals obtained by setting a=l/(n+l−2δ) in an expression given by Pyke (1959). Critical values for the Ds (corresponding to δ=.5) have been tabulated to 5DP by Miller (1956) for n=1(1)100. The authors have made analogous tabulations for the Cs (corresponding to δ=0) [previously tabulated by Durbin (1969) for n=1(1)60(2)100] and for the test statistics E+ n, E− n and En correspo...


American Journal of Human Biology | 1993

Improvement in the Roche‐Wainer‐Thissen stature prediction model: A comparative study

Harry J. Khamis; Shumei S. Guo

The Roche‐Wainer‐Thissen (RWT) prediction model, developed in 1975, predicts the adult stature of a child based on age, current stature, current weight, current skeletal age, and the average stature of the parents. Generally, the method has worked well; however, there are certain steps in the procedure that can be improved. Seven variations of the current version of the RWT prediction model are investigated and compared in terms of the accuracy and reliability of prediction, culminating in a recommendation for the prediction of adult stature in Caucasian Americans. The recommended method, called multivariate cubic spline smoothing [MCS2(1)], uses cubic splines in the smoothing part of the RWT prediction model, resulting in a simpler (i.e., fewer steps) method with smaller maximum deviations between predicted and actual adult statures than the current multivariate semi‐metric smoothing (MS2) method.


Archives of Ophthalmology | 2011

Effects of Time, Temperature, and Storage Container on the Growth of Fusarium Species: Implications for the Worldwide Fusarium Keratitis Epidemic of 2004-2006

John D. Bullock; B. Laurel Elder; Harry J. Khamis; Ronald E. Warwar

OBJECTIVE To demonstrate the effects of time, temperature, and container properties on the ability of ReNu with MoistureLoc (ReNuML; contains the antimicrobial agent alexidine) to inhibit growth of Fusarium species. METHODS ReNu with MoistureLoc was stored in its Bausch & Lomb (Rochester, New York) plastic or similarly sized glass containers for 1 and 4 weeks at room temperature, 42°C, and 56°C, and then tested for its ability to inhibit growth of 7 Fusarium isolates. RESULTS ReNu with MoistureLoc stored in glass containers for 1 or 4 weeks at all 3 temperatures demonstrated no significant fungistatic deterioration. However, ReNuML stored at 56°C in its Bausch & Lomb plastic container demonstrated a statistically significant fungistatic deterioration compared with room temperature storage in its original plastic container or with glass container storage at any temperature. CONCLUSION When exposed to elevated storage temperature, it appears that an interaction between ReNuML and its Bausch & Lomb plastic container adversely affects the fungistatic properties of ReNuML, which could have contributed to the Fusarium keratitis epidemic of 2004 through 2006.


Statistical Methods in Medical Research | 2008

Matched samples logistic regression in case-control studies with missing values: when to break the matches

Lisbeth Hansson; Harry J. Khamis

Simulated data sets are used to evaluate conditional and unconditional maximum likelihood estimation in an individual case-control design with continuous covariates when there are different rates of excluded cases and different levels of other design parameters. The effectiveness of the estimation procedures is measured by method bias, variance of the estimators, root mean square error (RMSE) for logistic regression and the percentage of explained variation. Conditional estimation leads to higher RMSE than unconditional estimation in the presence of missing observations, especially for 1:1 matching. The RMSE is higher for the smaller stratum size, especially for the 1:1 matching. The percentage of explained variation appears to be insensitive to missing data, but is generally higher for the conditional estimation than for the unconditional estimation. It is particularly good for the 1:2 matching design. For minimizing RMSE, a high matching ratio is recommended; in this case, conditional and unconditional logistic regression models yield comparable levels of effectiveness. For maximizing the percentage of explained variation, the 1:2 matching design with the conditional logistic regression model is recommended.

Collaboration


Dive into the Harry J. Khamis's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Oleg Paliy

Wright State University

View shared research outputs
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge