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Oral Bioavailability, Bioaccessibility, and Dermal Absorption of PAHs from Soil - State of the Science. - Environmental science & technology
This article reviews the state of the science regarding oral bioavailability, bioaccessibility, and dermal absorption of carcinogenic polycyclic aromatic hydrocarbons (cPAHs) in soil by humans, and discusses how chemical interactions may control the extent of absorption. Derived from natural and anthropomorphic origins, PAHs occur in a limited number of solid and fluid matrices (i.e., PAH sources) with defined physical characteristics and PAH compositions. Existing studies provide a strong basis for establishing that oral bioavailability of cPAHs from soil is less than from diet, and an assumption of 100% relative bioavailability likely overestimates exposure to cPAHs upon ingestion of PAH-contaminated soil. For both the oral bioavailability and dermal absorption studies, the aggregate data do not provide a broad understanding of how different PAH source materials, PAH concentrations, or soil chemistries influence the absorption of cPAHs from soil. This article summarizes the existing studies, identifies data gaps, and provides recommendations for the direction of future research to support new default or site-specific bioavailability adjustments for use in human health risk assessment.
Magnetite as a precursor for green rust through the hydrogenotrophic activity of the iron-reducing bacteria Shewanella putrefaciens. - Geobiology
Magnetite (Fe(II) Fe(III) 2 O4 ) is often considered as a stable end product of the bioreduction of Fe(III) minerals (e.g., ferrihydrite, lepidocrocite, hematite) or of the biological oxidation of Fe(II) compounds (e.g., siderite), with green rust (GR) as a mixed Fe(II) -Fe(III) hydroxide intermediate. Until now, the biotic transformation of magnetite to GR has not been evidenced. In this study, we investigated the capability of an iron-reducing bacterium, Shewanella putrefaciens, to reduce magnetite at circumneutral pH in the presence of dihydrogen as sole inorganic electron donor. During incubation, GR and/or siderite (Fe(II) CO3 ) formation occurred as secondary iron minerals, resulting from the precipitation of Fe(II) species produced via the bacterial reduction of Fe(III) species present in magnetite. Taking into account the exact nature of the secondary iron minerals and the electron donor source is necessary to understand the exergonic character of the biotic transformation of magnetite to GR, which had been considered to date as thermodynamically unfavorable at circumneutral pH. This finding reinforces the hypothesis that GR would be the cornerstone of the microbial transformations of iron-bearing minerals in the anoxic biogeochemical cycle of iron and opens up new possibilities for the interpretation of the evolution of Earth's history and for the understanding of biocorrosion processes in the field of applied science.Â© 2015 John Wiley & Sons Ltd.
Tools for the Microbiome: Nano and Beyond. - ACS nano
The microbiome presents great opportunities for understanding and improving the world around us and elucidating the interactions that compose it. The microbiome also poses tremendous challenges for mapping and manipulating the entangled networks of interactions among myriad diverse organisms. Here, we describe the opportunities, technical needs, and potential approaches to address these challenges, based on recent and upcoming advances in measurement and control at the nanoscale and beyond. These technical needs will provide the basis for advancing the largely descriptive studies of the microbiome to the theoretical and mechanistic understandings that will underpin the discipline of microbiome engineering. We anticipate that the new tools and methods developed will also be more broadly useful in environmental monitoring, medicine, forensics, and other areas.
The pH of beverages in the UnitedÂ States. - Journal of the American Dental Association (1939)
Dental erosion is the chemical dissolution of tooth structure in the absence of bacteria when the environment is acidic (pHÂ < 4.0). Research indicates that low pH is the primary determinant of a beverage's erosive potential. In addition, citrate chelation of calcium ions may contribute to erosion at higher pH. The authors of this study determined the erosive potential measured by the pH of commercially available beverages in the United States.The authors purchased 379 beverages from stores in Birmingham, Alabama, and categorized them (for example, juices, sodas, flavored waters, teas, and energy drinks) and assessed their pH. They used a pH meter to measure the pH of each beverage in triplicate immediately after it was opened at a temperature of 25Â°C. The authors recorded the pH data as mean (standard deviation).Most (93%, 354 of 379) beverages had a pH of less than 4.0, and 7% (25 of 379) had a pH of 4.0 or more. Relative beverage erosivity zones based on studies of apatite solubility in acid indicated that 39% (149 of 379) of the beverages tested in this study were considered extremely erosive (pHÂ < 3.0), 54% (205 of 379) were considered erosive (pH 3.0 to 3.99), and 7% (25 of 379) were considered minimally erosive (pHÂ â‰¥ 4.0).This comprehensive pH assessment of commercially available beverages in the United States found that most are potentially erosive to the dentition.This study's findings provide dental clinicians and auxiliaries with information regarding the erosive potential of commercially available beverages. Specific dietary recommendations for the prevention of dental erosion may now be developed based on the patient's history of beverage consumption.Copyright Â© 2016 American Dental Association. Published by Elsevier Inc. All rights reserved.
Magnetic anisotropy in Shiba bound states across a quantum phase transition. - Nature communications
The exchange coupling between magnetic adsorbates and a superconducting substrate leads to Shiba states inside the superconducting energy gap and a Kondo resonance outside the gap. The exchange coupling strength determines whether the quantum many-body ground state is a Kondo singlet or a singlet of the paired superconducting quasiparticles. Here we use scanning tunnelling spectroscopy to identify the different quantum ground states of manganese phthalocyanine on Pb(111). We observe Shiba states, which are split into triplets by magnetocrystalline anisotropy. Their characteristic spectral weight yields an unambiguous proof of the nature of the quantum ground state. Our results provide experimental insights into the phase diagram of a magnetic impurity on a superconducting host and shine light on the effects induced by magnetic anisotropy on many-body interactions.
End States and Subgap Structure in Proximity-Coupled Chains of Magnetic Adatoms. - Physical review letters
A recent experiment [Nadj-Perge etÂ al., Science 346, 602 (2014)] provides evidence for Majorana zero modes in iron (Fe) chains on the superconducting Pb(110) surface. Here, we study this system by scanning tunneling microscopy using superconducting tips. This high-resolution technique resolves a rich subgap structure, including zero-energy excitations in some chains. We compare the symmetry properties of the data under voltage reversal against theoretical expectations and provide evidence that the putative Majorana signature overlaps with a previously unresolved low-energy resonance. Interpreting the data within a Majorana framework suggests that the topological gap is smaller than previously extracted from experiment. Aided by model calculations, we also analyze higher-energy features of the subgap spectrum and their relation to high-bias peaks which we associate with the Fe d bands.
Characterization of the Vibrio fischeri Fatty Acid Chemoreceptors, VfcB and VfcB2. - Applied and environmental microbiology
Bacteria use a wide variety of methyl-accepting chemotaxis proteins (MCPs) to mediate their attraction to or repulsion from different chemical signals in their environment. The bioluminescent marine bacterium Vibrio fischeri is the monospecific symbiont of the Hawaiian bobtail squid, Euprymna scolopes, and encodes a large repertoire of MCPs that are hypothesized to be used during different parts of its complex, multistage lifestyle. Here, we report the initial characterization of two such MCPs from V. fischeri that are responsible for mediating migration toward short- and medium-chain aliphatic (or fatty) acids. These receptors appear to be distributed among only members of the family Vibrionaceae and are likely descended from a receptor that has been lost by the majority of the members of this family. While chemotaxis greatly enhances the efficiency of host colonization by V. fischeri, fatty acids do not appear to be used as a chemical cue during this stage of the symbiosis. This study presents an example of straight-chain fatty acid chemoattraction and contributes to the growing body of characterized MCP-ligand interactions.Copyright Â© 2016, American Society for Microbiology. All Rights Reserved.
Attitudes toward beef and vegetarians in Argentina, Brazil, France, and the USA. - Appetite
Meat is both the most favored and most tabooed food in the world. In the developed world, there is a tension between its high nutritional density, preferred taste, and high status on the one hand, and concerns about weight, degenerative diseases, the ethics of killing animals, and the environmental cost of meat production on the other hand. The present study investigated attitudes toward beef, and toward vegetarians, among college students in Argentina, Brazil, France, and the USA. Across countries, men were more pro-beef, in free associations, liking, craving, and frequency of consumption. By country, Brazil and Argentina were generally the most positive, followed by France and then the United States. Ambivalence to beef was higher in women, and highest in Brazil. Only Brazilian and American women reported frequent negative associations to beef (e.g. "disgusting", "fatty"). Overall, most students had positive attitudes to beef, and the attitude to vegetarians was generally neutral. America and Brazilian women showed some admiration for vegetarians, while only French men and women had negative attitudes to vegetarians. In spite of frequent negative ethical, health, and weight concerns, in the majority of the sample, liking for and consumption of beef was maintained at a high level.Copyright Â© 2015 Elsevier Ltd. All rights reserved.
Impact of extreme exercise at high altitude on oxidative stress in humans. - The Journal of physiology
Exercise and oxidative stress research continues to grow as a physiologic sub-discipline. The influence of high altitude on exercise and oxidative stress is among the recent topics of intense study in this area. Early findings indicate that exercise at high altitude has an independent influence on free radical generation and the resultant oxidative stress. This review provides a detailed summary of oxidative stress biochemistry as gleaned mainly from studies of humans exercising at high altitude. Understanding of the human response to exercise at altitude is largely derived from field-based research at altitudes above 3000m in addition to laboratory studies which employ normobaric hypoxia. The implications of oxidative stress incurred during high altitude exercise appears to be a transient increase in oxidative damage followed by redox sensitive adaptations in multiple tissues. These outcomes are consistent for lowland natives, high altitude acclimated sojourners, and highland natives, although the latter group exhibits a more robust adaptive response. To date there is no evidence that altitude-induced oxidative stress is deleterious to normal training or recovery scenarios. Limited evidence suggests that deleterious outcomes related to oxidative stress are limited to instances where individuals are exposed to extreme elevations for extended durations. However, confirmation of this tentative conclusion requires further investigation. More applicably, altitude-induced hypoxia may have an independent influence on redox sensitive adaptive responses to exercise and exercise recovery. If correct, these findings may hold important implications for athletes, mountaineers, and soldiers working at high altitude. These points are raised within the confines of published research on the topic of oxidative stress during exercise at altitude. This article is protected by copyright. All rights reserved.This article is protected by copyright. All rights reserved.
Aggressive Surgical Therapy With Early Vitrectomy, Panretinal Photocoagulation, and Silicone Oil Tamponade for Streptococcus mitis Endophthalmitis. - Ophthalmic surgery, lasers & imaging retina
An 87-year-old woman presented with acute, painful vision loss in her right eye after intravitreal injection. Examination disclosed hypopyon and vitritis, as well as discrete inflammatory collections in the vitreous and widespread retinal hemorrhages. The patient underwent vitrectomy with injection of intravitreal antibiotics. Vitreous cultures were positive for Streptococcus mitis, a pathogen associated with severe tissue damage and poor clinical outcomes. Clinical deterioration prompted repeat vitrectomy with silicone oil tamponade and panretinal photocoagulation two weeks later, resulting in more favorable anatomic and visual outcomes. Endophthalmitis caused by exotoxin-producing bacterial species such as S. mitis is often associated with severe vision loss or loss of the eye. Aggressive surgical intervention--prompted by concerning clinical findings and vitreous cultures--may play a role in improving outcomes in these patients.Copyright 2015, SLACK Incorporated.
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