Effects of Shot-Peening on High Cycle Fretting Fatigue Behavior of Ti-6Al-4V

Effects of Shot-peening on High Cycle Fretting Fatigue behavior of Ti-6Al-4V were investigated. Experiments were performed with 6.35 mm thick specimens which provided S/N curves. After the tests, it was observed that the specimens failed near the trailing edge of contact. Scanning Electron Microscopy showed that cracks initiated on the contact surface for 6.35 mm, and at the depth of specimen ranging from 200 to 300 microns for 3.81 mm thick specimens. Initial crack orientation was around 37 and 42 degrees respectively for 6.35 and 3.81 mm thicknesses. Finite Element Analysis (FEA) was conducted, and using FEA results, Smith-Watson-Topper, Findley, Shear Stress Range and Modified Shear Stress Range parameters were evaluated. Stress relaxation was observed after the failure of the specimens, and evaluations were repeated for different percentages of stress relaxation. Based on specific assumptions about stress relaxation. Modified Shear Stress range parameter was determined to be the only appropriate fatigue parameter that could meet all the required conditions for shot-peened fretting fatigue specimens. Also thickness effects on shot-peened specimens were investigated and discussed in this study

Weighted Approximation by a Certain Family of Summation Integral-Type Operators

AbstractIn this study, we investigate the weighted approximation properties of a general sequence of summation integral-type operators introduced by Srivastava and Gupta [1]. We estimate the rate of convergence of these operators for functions of polynomial growth in terms of weighted modulus of continuity on the interval [0, ∞)

Search for α\alpha decay of 151^{151}Eu to the first excited level of 147^{147}Pm using underground γ\gamma-ray spectrometry

The alpha decay of $^{151}$Eu to the first excited level of $^{147}$Pm ($J^\pi = 5/2^+$, $E_{exc}=91.1$ keV) was searched for at the HADES underground laboratory ($\approx 500$ m w.e.). A sample of high purity europium oxide with mass of 303 g and a natural isotopic composition has been measured over 2232.8 h with a high energy resolution ultra-low background n-type semi-planar HPGe detector (40 cm$^3$) with sub-micron deadlayer. The new improved half-life limit has been set as $T_{1/2} \geq 3.7\times 10^{18}$ yr at 68% C.L. Possibilities to improve the sensitivity of the experiment, which is already near the theoretical predictions, are discussed. New half-life limit for $\alpha$ decay of $^{153}$Eu is also set as $T_{1/2} \geq 5.5\times 10^{17}$ yr.Comment: 11 pages, 5 figures, 2 tables, 18 reference

Direct Evidence for P2Y2 Receptor Involvement in Vascular Response to Injury

Objectives Extracellular nucleotide release at the site of arterial injury mediates proliferation and migration of vascular smooth muscle cells (SMC). Our aim was to investigate the role of the P2Y2 nucleotide receptor (P2Y2R) in neointimal hyperplasia. Approach and Results Vascular injury was induced by implantation of a polyethylene cuff around the femoral artery in wild-type and P2Y2 receptor-deficient mice (P2Y2R−/−). Electron microscopy was used to analyze monocyte and lymphocyte influx to the intima 36 hours post-injury. Compared to wild-type (WT) littermates, P2Y2R−/− mice exhibited a 3-fold decreased number of mononuclear leukocytes invading the intima (p<0.05). Concomitantly, migration of smooth muscle cells was decreased by more than 60% (p<0.05) a resulting in a sharp inhibition of intimal thickening formation in P2Y2R−/− mice (n=15) 14 days after cuff placement. In vitro, loss of P2Y2 receptor significantly impaired monocyte migration in response to nucleotide agonists. Furthermore, transgenic rats over-expressing the P2Y2R developed accelerated intimal lesions resulting in more than 95% luminal stenosis (P<0.05, n=10). Conclusions Loss-and gain-of-function approaches established a direct evidence for P2Y2 receptor involvement in neointimal hyperplasia. Specific anti-P2Y2 receptor therapies may be used against restenosis and bypass graft failure

Role of IRAK-M in Alcohol Induced Liver Injury

Increasing evidence suggests that innate immunity plays an important role in alcohol-induced liver injury and most studies have focused on positive regulation of innate immunity. The main objective of this study was to investigate the negative regulator of innate immunity, IL-1/Toll-like receptor (TLR) signaling pathways and interleukin receptor-associated kinase-M (IRAK-M) in alcoholic liver injury. We established an alcohol-induced liver injury model using wild type and IRAK-M deficient B6 mice and investigated the possible mechanisms. We found that in the absence of IRAK-M, liver damage by alcohol was worse with higher alanine transaminase (ALT), more immune cell infiltration and increased numbers of IFNγ producing cells. We also found enhanced phagocytic activity in CD68+ cells. Moreover, our results revealed altered gut bacteria after alcohol consumption and this was more striking in the absence of IRAK-M. Our study provides evidence that IRAK-M plays an important role in alcohol-induced liver injury and IRAK-M negatively regulates the innate and possibly the adaptive immune response in the liver reacting to acute insult by alcohol. In the absence of IRAK-M, the hosts developed worse liver injury, enhanced gut permeability and altered gut microbiota

Nambu-Goldstone Dark Matter and Cosmic Ray Electron and Positron Excess

We propose a model of dark matter identified with a pseudo-Nambu-Goldstone boson in the dynamical supersymmetry breaking sector in a gauge mediation scenario. The dark matter particles annihilate via a below-threshold narrow resonance into a pair of R-axions each of which subsequently decays into a pair of light leptons. The Breit-Wigner enhancement explains the excess electron and positron fluxes reported in the recent cosmic ray experiments PAMELA, ATIC and PPB-BETS without postulating an overdensity in halo, and the limit on anti-proton flux from PAMELA is naturally evaded.Comment: 3 figure

Experimental investigation of relationship between trauma and bisphosphonate-related osteonecrosis

Background: Bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) disease is rare, but there are serious side-effects of BP therapy in patients. In some patients, surgery is needed and could not be cured. Astandard test is not available showing the risk of jaw osteonecrosis in routine use. The measurement of serum C.terminal telopeptide (CTX) levels has been used in diseases of BRONJ resorption and antiresorptive therapy.Aim: This paper is aimed at investigating the relationship between  traumatic procedures and presence of BP-related osteonecrosis.Materials and Methods: Thirty male Wistar albino rats with weighing 200 } 20 g were used for the experimental procedures. Rats were randomly divided into three groups each containing 10 rats as follows: Group 1 (traumatic extraction group), Group 2 (atraumatic extraction group), and Group 3 (control group). All groups, zoledronic acid (ZA) (0.3  mg/kg/week)[1] was diluted with physiological saline and given  subcutaneously for 2 months. After the 2 months, Group 1 was subjected totraumatic extraction of right first lower molars, and Group 2 was subjected to atraumatic extractions of the right first lower molars. Group 3 was subjected to no extractions as a control group. Animals were euthanized 32 days after tooth extractions, and the ZA administration protocol was maintained until the animalsf death. After sacrifice, blood samples were collected for C-terminal cross.linking telopeptide of type I collagen (CTX.1) levels, clinical and radiological findings were recorded.Results: The bone resorption marker CTX-1 showed a significant difference among the groups. CTX-1 was measured significantly higher in blood samples of Group 2 (4.15 } 0.34; P = 0.001) than Group 1 (3.77 } 0.34; P = 0.0001). No, statistically significant changes were found between Groups 1 and 2 as for clinical and radiological assessment.Conclusion: This study provides preliminary observations for the  development of an animal model of BRONJ. Although clinical and  radiological findings were not relevant, serum CTX values are reliable biochemical markers for predicting BRONJ and also atraumatic surgical procedures are important to prevent BRONJ.Key words: Bisphosphonates, bone, osteonecrosis, prevention, serum C-terminal telopeptide leve

Dark matter and sub-GeV hidden U(1) in GMSB models

Motivated by the recent PAMELA and ATIC data, one is led to a scenario with heavy vector-like dark matter in association with a hidden $U(1)_X$ sector below GeV scale. Realizing this idea in the context of gauge mediated supersymmetry breaking (GMSB), a heavy scalar component charged under $U(1)_X$ is found to be a good dark matter candidate which can be searched for direct scattering mediated by the Higgs boson and/or by the hidden gauge boson. The latter turns out to put a stringent bound on the kinetic mixing parameter between $U(1)_X$ and $U(1)_Y$: $\theta \lesssim 10^{-6}$. For the typical range of model parameters, we find that the decay rates of the ordinary lightest neutralino into hidden gauge boson/gaugino and photon/gravitino are comparable, and the former decay mode leaves displaced vertices of lepton pairs and missing energy with distinctive length scale larger than 20 cm for invariant lepton pair mass below 0.5 GeV. An unsatisfactory aspect of our model is that the Sommerfeld effect cannot raise the galactic dark matter annihilation by more than 60 times for the dark matter mass below TeV.Comment: 1+15 pages, 4 figures, version published in JCAP, references added, minor change

Dark Matter Model Selection and the ATIC/PPB-BETS anomaly

We argue that we may be able to sort out dark matter models in which electrons are generated through the annihilation and/or decay of dark matter, by using a fact that the initial energy spectrum is reflected in the cosmic-ray electron flux observed at the Earth even after propagation through the galactic magnetic field. To illustrate our idea we focus on three representative initial spectra: (i)monochromatic (ii)flat and (iii)double-peak ones. We find that those three cases result in significantly different energy spectra, which may be probed by the Fermi satellite in operation or an up-coming cosmic-ray detector such as CALET.Comment: 19 pages, 8 figure