<b><i>Introduction:</i></b> An association has been found between human-gut microbiota and various diseases (e.g., metabolic disease) by analyzing fecal or colonic microbiota. Despite the importance of the small intestinal microbiota, sampling difficulties prevent its full analysis. We investigated the composition and metagenomic functions of microbiota along the small intestine and compared them with the microbiota from feces and from other gastrointestinal (GI) sites. <b><i>Methods:</i></b> Mucosal samples from the six GI sites (stomach, duodenum, distal jejunum, proximal ileum, terminal ileum, and rectum) were collected under balloon-assisted enteroscopy. Fecal samples were collected from all participants. The microbial structures and metagenomic functions of the small intestinal mucosal microbiota were compared with those from feces and other GI sites using 16S ribosomal RNA gene sequencing. <b><i>Results:</i></b> We analyzed 133 samples from 29 participants. Microbial beta diversity analysis showed that the jejunum and ileum differed significantly from the lower GI tract and the feces (<i>p</i> &#x3c; 0.001). Jejunal and duodenal microbiotas formed similar clusters. Wide clusters spanning the upper and lower GI tracts were observed with the ileal microbiota, which differed significantly from the jejunal microbiota (<i>p</i> &#x3c; 0.001). <i>Veillonella</i> and <i>Streptococcus</i> were abundant in the jejunum but less so in the lower GI tract and feces. The metagenomic functions associated with nutrient metabolism differed significantly between the small intestine and the feces. <b><i>Conclusions:</i></b> The fact that the compositional structures of small intestinal microbiota differed from those of fecal and other GI microbiotas reveals that analyzing the small intestinal microbiota is necessary for association studies on metabolic diseases and gut microbiota.

A B S T R A C T This paper proposes a local stress concept to evaluate the fretting fatigue limit for contact edge cracks. A unique S-N curve based on the local stress could be obtained for a contact edge crack irrespective of mechanical factors such as contact pressure, relative slip, contact length, specimen size and loading type. The analytical background for the local stress concept was studied using FEM analysis. It was shown that the local stress uniquely determined the K change due to crack growth as well as the stress distribution near the contact edge. The condition that determined the fretting fatigue limit was predicted by combining the K change due to crack growth and the K th for a short crack. The formation of a non-propagating crack at the fatigue limit was predicted by the model and it was experimentally confirmed by a long-life fretting fatigue test.a = crack length area = area of small defect HV = Vickers hardness l = distance from the contact edge L = length of contact pad p = mean value of contact pressure R = stress ratio (σ min /σ max ) µ = friction coefficient σ a = nominal applied stress amplitude σ ap = local stress amplitude at the contact edge σ max = maximum stress σ min = minimum stress K = stress intensity factor range K th = threshold stress intensity factor range

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i［ has been reported that the efi辷ct of various f 亘ctQrs intluencing し hc n 』 etting fbtlguc ］ imit can be ＄ucc じ∬ t｝ 」lly evaluated based oll the looal stress at the contacl c 〔 ｝ rn じr、 1t is shown in this rcport ［hal lhc fretting fatigue Iimit of the local stress coincided with the threshold conditbn for the continuous growth ofamicro " crack which had been generated by 丘e し し ing． Key 脇 Verds ： Fretting Fatigue ， Local Stress ， Fatigue Limit． Material Strength． Short Crack 、 Thresho ］ d Condition