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Forces and energetics of intermittent swimming

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Acta Mechanica Sinica 2017年第4期33卷 725-732页

作者： Daniel Floryan tyler Van Buren Alexander j.Smits Department of Mechanical and Aerospace Engineering Princeton University Princeton NJ 08544 USA

Experiments are reported on intermittent swimming motions. Water tunnel experiments on a nominally two-dimensional pitching foil show that the mean thrust and power scale linearly with the duty cycle, from a value of 0.2 all the way up to continuous motions, indicating that individual bursts of activity in intermittent motions are independent of each other. This conclusion is corroborated by particle image velocimetry（PIV） flow visualizations, which show that the main vortical structures in the wake do not change with duty cycle. The experimental data also demonstrate that intermittent motions are generally energetically advantageous over continuous motions. When metabolic energy losses are taken into account, this conclusion is maintained for metabolic power fractions less than 1.

关键词： intermittent swimming maintained conclusion cycle thrust favorable producing aquatic circles

Aging gracefully: social engagement joins exercise and enrichment as a key lifestyle factor in resistance to age-related cognitive decline

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Neural Regeneration Research 2019年第1期14卷 39-42页

作者： tyler j.Dause Elizabeth D.Kirby Department of Psychology The Ohio State University Department of Neuroscience The Ohio State University Chronic Brain Injury Program The Ohio State University

Cognitive impairment is a consequence of the normal aging process that effects many species, including humans and rodent models. Decline in hippocampal memory function is especially prominent with age and often reduces quality of life. As the aging population expands, the need for interventional strategies to prevent cognitive decline has become more pressing. Fortunately, several major lifestyle factors have proven effective at combating hippocampal aging, the most well-known of which are environmental enrichment and exercise. While the evidence supporting the beneficial nature of these factors is substantial, a less well-understood factor may also contribute to healthy cognitive aging: social engagement. We review the evidence supporting the role of social engagement in preserving hippocampal function in old age. In elderly humans, high levels of social engagement correlate with better hippocampal function, yet there is a dearth of work to indicate a causative role. Existing rodent literature is also limited but has begun to provide causative evidence and establish candidate mechanisms. Summed together, while many unanswered questions remain, it is clear that social engagement is a viable lifestyle factor for preserving cognitive function in old age. Social integration across the lifespan warrants more investigation and more appreciation when designing living circumstances for the elderly.

关键词： aging age-related cognitive decline social engagement hippocampus cognitive enrichment exercise memory neurogenesis

Genetic factors that affect nonalcoholic fatty liver disease: A systematic clinical review

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World journal of Gastroenterology 2016年第29期22卷 6742-6756页

作者： tyler j Severson Siddesh Besur Herbert L Bonkovsky Department of Gastroenterology and Hepatology Wake Forest University NC Baptist Medical Center Abdominal Transplant Program Aurora St Luke’s Medical Center

AIM: To investigate roles of genetic polymorphisms in non-alcoholic fatty liver disease (NAFLD) onset, severity, and outcome through systematic literature ***: The authors conducted both systematic and specific searches of PubMed through December 2015 with special emphasis on more recent data (from 2012 onward) while still drawing from more historical data for background. We identified several specific genetic polymorphisms that have been most researched and, at this time, appear to have the greatest clinical significance on NAFLD and similar hepatic diseases. These were further investigated to assess their specific effects on disease onset and progression and the mechanisms by which these effects ***: We focus particularly on genetic polymorphisms of the following genes: PNPLA3, particularly the p. I148M variant, TM6SF2, particularly the p. E167K variant, and on variants in FTO, LIPA, IFNλ4, and iron metabolism, specifically focusing on HFE, and HMOX-1. We discuss the effect of these genetic variations and their resultant protein variants on the onset of fatty liver disease and its severity, including the effect on likelihood of progression to cirrhosis and hepatocellular carcinoma. While our principal focus is on NAFLD, we also discuss briefly effects of some of the variants on development and severity of other hepatic diseases, including hepatitis C and alcoholic liver disease. These results are briefly discussed in terms of clinical application and future potential for personalized ***: Polymorphisms and genetic factors of several genes contribute to NAFLD and its end results. These genes hold keys to future improvements in diagnosis and management.

关键词： Genetic polymorphisms Non-alcoholic fatty liver disease Non-alcoholic steatohepatitis PNPLA3 TM6SF2 FTO Cirrhosis Iron metabolism

Tight junction disruption: Helicobacter pylori and dysregulation of the gastric mucosal barrier

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World journal of Gastroenterology 2015年第40期21卷 11411-11427页

作者： tyler j Caron Kathleen E Scott james G Fox Susan j Hagen Department of Surgery Beth Israel Deaconess Medical Center and Harvard Medical School Division of Comparative Medicine Massachusetts Institute of Technology

Long-term chronic infection with Helicobacter pylori(H. pylori) is a risk factor for gastric cancer development. In the multi-step process that leads to gastric cancer,tight junction dysfunction is thought to occur and serve as a risk factor by permitting the permeation of luminal contents across an otherwise tight mucosa. Mechanisms that regulate tight junction function and structure in the normal stomach,or dysfunction in the infected stomach,however,are largely unknown. Although conventional tight junction components are expressed in gastric epithelial cells,claudins regulate paracellular permeability and are likely the target of inflammation or H. pylori itself. There are 27 different claudin molecules,each with unique properties that render the mucosa an intact barrier that is permselective in a way that is consistent with cell physiology. Understanding the architecture of tight junctions in the normal stomach and then changes that occur during infection is important but challenging,because most of the reports that catalog claudin expression in gastric cancer pathogenesis are contradictory. Furthermore,the role of H. pylori virulence factors,such as cytotoxin-associated gene A and vacoulating cytotoxin,in regulating tight junction dysfunction during infection is inconsistent in different gastric cell lines and in vivo,likely because non-gastric epithelial cell cultures were initially used to unravel the details of their effects on the stomach. Hampering further study,as well,is the relative lack of cultured cell models that have tight junction claudins that are consistent with native tissues. This summary will review the current state of knowledge about gastric tight junctions,normally and in H. pylori infection,and make predictions about the consequences of claudin reorganization during H. pylori infection.

关键词： Helicobacter pylori Tight junction Claudins Parace

Emerging role of microRNAs in lipid metabolism

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Acta Pharmaceutica Sinica B 2015年第2期5卷 145-150页

作者： Zhihong Yang tyler Cappello Li Wang Department of Physiology and Neurobiology and the Institute for Systems Genomics University of Connecticut Veterans Affairs Connecticut Healthcare System Department of Internal Medicine Section of Digestive Diseases Yale University

micro RNAs(mi RNAs or mi Rs) are small non-coding RNAs that are involved in posttranscriptional regulation of their target genes in a sequence-specific manner. Emerging evidence demonstrates that mi RNAs are critical regulators of lipid synthesis, fatty acid oxidation and lipoprotein formation and secretion. Dysregulation of mi RNAs disrupts gene regulatory network, leading to metabolic syndrome and its related diseases. In this review, we introduced epigenetic and transcriptional regulation of mi RNAs expression. We emphasized on several representative mi RNAs that are functionally involved into lipid metabolism, including mi R-33/33 n, mi R122, mi R27a/b, mi R378/378 n, mi R-34 a and mi *** the function of mi RNAs in lipid homeostasis may provide potential therapeutic strategies for fatty liver disease.

关键词： Lipid metabolism microRNAs Nuclear receptors

Intersystem crossing and exciton–defect coupling of spin defects in hexagonal boron nitride

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npj Computational Materials 2021年第1期7卷 537-544页

作者： tyler jSmart Kejun Li junqing Xu Yuan Ping Department of Physics University of CaliforniaSanta CruzCAUSA Lawrence Livermore National Laboratory LivermoreCAUSA Department of Chemistry and Biochemistry University of CaliforniaSanta CruzCAUSA

Despite the recognition of two-dimensional(2D)systems as emerging and scalable host materials of single-photon emitters or spin qubits,the uncontrolled,and undetermined chemical nature of these quantum defects has been a roadblock to further *** the design of extrinsic defects can circumvent these persistent issues and provide an ultimate ***,we established a complete theoretical framework to accurately and systematically design quantum defects in wide-bandgap 2D *** this approach,essential static and dynamical properties are equally considered for spin qubit *** particular,many-body interactions such as defect–exciton couplings are vital for describing excited state properties of defects in ultrathin 2D ***,nonradiative processes such as phonon-assisted decay and intersystem crossing rates require careful evaluation,which competes together with radiative *** a thorough screening of defects based on firstprinciples calculations,we identify promising single-photon emitters such as SiVV and spin qubits such as TiVV and MoVV in hexagonal boron *** work provided a complete first-principles theoretical framework for defect design in 2D materials.

关键词： defect hexagonal boron

Mechanistic insights of enhanced spin polaron conduction in CuO through atomic doping

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npj Computational Materials 2018年第1期4卷 154-161页

作者： tyler j.Smart Allison C.Cardiel Feng Wu Kyoung-Shin Choi Yuan Ping Department of Physics University of CaliforniaSanta CruzCA 95064USA Department of Chemistry University of WisconsinMadisonWI 53706USA Department of Chemistry and Biochemistry University of CaliforniaSanta CruzCA 95064USA

The formation of a“spin polaron”stems from strong spin-charge-lattice interactions in magnetic oxides,which leads to a localization of carriers accompanied by local magnetic polarization and lattice *** example,cupric oxide(CuO),which is a promising photocathode material and shares important similarities with high Tc superconductors,conducts holes through spin polaron hopping with flipped spins at Cu atoms where a spin polaron has *** formation of these spin polarons results in an activated hopping conduction process where the carriers must not only overcome strong electron−phonon coupling but also strong magnetic ***,these effects cause low carrier conduction in CuO and hinder its *** overcome this fundamental limitation,we demonstrate from first-principles calculations how doping can improve hopping conduction through simultaneous improvement of hole concentration and hopping mobility in magnetic oxides such as ***,using Li doping as an example,we show that Li has a low ionization energy that improves hole concentration,and lowers the hopping barrier through both the electron−phonon and magnetic couplings'reduction that improves hopping ***,this improved conduction predicted by theory is validated through the synthesis of Li-doped CuO electrodes which show enhanced photocurrent compared to pristine CuO *** conclude that doping with nonmagnetic shallow impurities is an effective strategy to improve hopping conductivities in magnetic oxides.

关键词： conduction doping polaron

A General Algorithm for Calculating Irreducible Brillouin Zones

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Communications in Computational Physics 2022年第2期31卷 495-515页

作者： jeremy j.jorgensen john E.Christensen tyler j.jarvis Gus L.W.Hart Department of Physics and Astronomy Brigham Young UniversityProvoUtah84602USA Department ofMathematics BrighamYoungUniversityProvoUtah84602USA

Calculations of properties of materials require performing numerical integrals over the Brillouin zone(BZ).Integration points in density functional theory codes are uniformly spread over the BZ(despite integration error being concentrated in small regions of the BZ)and preserve symmetry to improve computational *** points over an irreducible Brillouin zone(IBZ),a rotationally distinct region of the BZ,do not have to preserve crystal symmetry for greater *** freedom allows the use of adaptive meshes with higher concentrations of points at locations of large error,resulting in improved algorithmic *** have created an algorithm for constructing an IBZ of any crystal structure in 2D and *** algorithmuses convex hull and half-space representations for the BZ and IBZ to make many aspects of construction and symmetry reduction of the BZ *** algorithm is simple,general,and available as open-source software.

关键词： Brillouin zone irreducible Brillouin zone

Near-UV electroluminescence in unipolar-doped, bipolar-tunneling GaN/AlN heterostructures

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Light(Science & Applications) 2017年第1期6卷 168-174页

作者： tyler A Growden Weidong Zhang Elliott R Brown David F Storm David j Meyer Paul R Berger Department of Electrical and Computer Engineering The Ohio State UniversityColumbusOhio 43210USA Departments of Physics and Electrical Engineering Wright State UniversityDaytonOhio 45435USA US Naval Research Laboratory WashingtonDC 20375USA

Cross-gap light emission is reported in n-type unipolar GaN/AlN double-barrier heterostructure diodes at room *** different designs were grown on semi-insulating bulk GaN substrates using molecular beam epitaxy(MBE).All samples displayed a single electroluminescent spectral peak at 360 nm with full-width at half-maximum(FWHM)values no greater than 16 nm and an external quantum efficiency(EQE)of≈0.0074%at 18.8 *** contrast to traditional GaN light emitters,p-type doping and p-contacts are completely avoided,and instead,holes are created in the GaN on the emitter side of the tunneling structure by direct interband(that is,Zener)tunneling from the valence band to the conduction band on the collector *** Zener tunneling is enhanced by the high electric fields(~5×106 V cm^(−1))created by the notably large polarization-induced sheet charge at the interfaces between the AlN and GaN.

关键词： AlN GaN heterostructure Near-UV light emission unipolar Zener tunneling