Constitutive relations for the isotropic deformation of frictionless packings of polydisperse spheres

The isotropic compression of polydisperse packings of frictionless spheres is modeled with the Discrete Element Method (DEM). The evolution of coordination number, fraction of rattlers, isotropic fabric, and pressure (isotropic stress) is reported as function of volume fraction for different system parameters. The power law relationship, with power ≈1/2, between coordination number and volume fraction is confirmed in the jammed state for a broad range of volume fractions and for different (moderate) polydispersities. The polydispersity in the packing causes a shift of the critical volume fraction, i.e., more heterogeneous packings jam at higher volume fractions. Close to jamming, the coordination number and the jamming volume fraction itself depend on both history and rate. At larger densities, neither the deformation history nor the loading rate have a significant effect on the evolution of the coordination number.\ud \ud Concerning the fabric tensor, comparing our DEM results to theoretical predictions, good agreement for different polydispersities is observed. An analytical expression for the pressure as function of isotropic (volumetric) strain is proposed for polydisperse packings, based on the assumption of uniform deformation. We note that, besides the implicit proportionality to contact number density (or fabric), no single power-law is evidenced in the relation between pressure and isotropic strain. However, starting from zero pressure at the jamming point, a linear term with a quadratic correction describes the stress evolution rather well for a broad range of densities and for various polydispersities. Finally, an incremental evolution equation is proposed for both fabric and stress, as function of isotropic strain, and involving the coordination number and the fraction of rattlers, as starting point for further studies involving anisotropic deformations

Tip A Aort Diseksiyonlarında Operasyon Sonrası Erken Dönem Mortalite ve Morbidite Üzerine Etki Eden Faktörlerin Retrospektif İncelenmesi

Amaç: Aortik diseksiyon günümüzde hala önemli bir mortalite ve morbidite nedenidir. Tip A aort diseksiyonu nedeniyle ameliyat edilen hastalarda birçok faktör cerrahi sonuçları etkilemektedir. Bu faktörlerin yeterince belirlenmesi tedavinin başarılı olmasına etki edecektir. Yöntemler: Kliniğimizde Ocak 2006 - Aralık 2016 yılları arasında Tip A aort diseksiyonu tanısı ile opere edilen 140 hastanın preoperatif, intraoperatif, ve postoperatif verileri, hasta dosyaları ve hastane bilgi yönetim sistem kayıtlarından retrospektif olarak araştırıldı. Gruplar arası niceliksel parametreler Student t veya Mann-Whitney U testleri ile, niteliksel veriler ise Ki-Kare testi ile karşılaştırıldı. Bulgular: Hastalarda ortalama yaş 57.1±12.3 (min: 27 ile max: 84), 31’i (%22,2) kadın, 109’u (%77,8) erkekti. Hastaların çoğunluğuna izole asendan aorta replasmanı veya asendan aorta ile birlikte hemiarkus replasmanı uygulandı (%70). Beyin koruma yöntemi olarak çoğunlukla antegrad serebral perfüzyon (ASP) nadiren retrograd serebral perfüzyon (RSP) kullanıldı. Tüm hastalarda total mortalite 37 kişi (%26,4) idi. Başvuru anında sistolik tansiyonun 90 mmHg altında olması, majör nörolojik defisit varlığı, hastada geçirilmiş kardiyak cerrahi öyküsü olmasının mortaliteyi anlamlı oranda etkilediği saptanmıştır (p<0.05). Mortalite olan hastalarda perfüzyon süreleri uzun, inotrop ihtiyacı fazla, yoğun bakım yatış süreleri istatiksel olarak anlamlı derecede yüksekti (p<0.05). RSP yapılan grupta yoğun bakımda kalış süreleri ve mortalite, ASP uygulanan hastalara göre anlamlı oranda yüksekti (sırası ile p=0.02, p=0.04). Sonuç: Tip A aortik diseksiyonlarda mortalite üzerine etki eden faktörlerin daha büyük hasta serilerinde ortaya konulması ve bu faktörlere yönelik tedbirlerin alınması mortalite ve morbiditenin azaltılmasında etkili olabilir

Constitutive relations for the isotropic deformation of frictionless packings of polydisperse spheres

The isotropic compression of polydisperse packings of frictionless spheres is modeled with the Discrete Element Method (DEM). The evolution of coordination number, fraction of rattlers, isotropic fabric, and pressure (isotropic stress) is reported as function of volume fraction for different system parameters. The power law relationship, with power ≈1/2, between coordination number and volume fraction is confirmed in the jammed state for a broad range of volume fractions and for different (moderate) polydispersities. The polydispersity in the packing causes a shift of the critical volume fraction, i.e., more heterogeneous packings jam at higher volume fractions. Close to jamming, the coordination number and the jamming volume fraction itself depend on both history and rate. At larger densities, neither the deformation history nor the loading rate have a significant effect on the evolution of the coordination number. Concerning the fabric tensor, comparing our DEM results to theoretical predictions, good agreement for different polydispersities is observed. An analytical expression for the pressure as function of isotropic (volumetric) strain is proposed for polydisperse packings, based on the assumption of uniform deformation. We note that, besides the implicit proportionality to contact number density (or fabric), no single power-law is evidenced in the relation between pressure and isotropic strain. However, starting from zero pressure at the jamming point, a linear term with a quadratic correction describes the stress evolution rather well for a broad range of densities and for various polydispersities. Finally, an incremental evolution equation is proposed for both fabric and stress, as function of isotropic strain, and involving the coordination number and the fraction of rattlers, as starting point for further studies involving anisotropic deformations

Hexagonal boron nitride nanoparticles trigger oxidative stress by modulating thiol/disulfide homeostasis

Background: Hexagonal boron nitride nanoparticles (hBN NPs) are encouraging nanomaterials with uniquechemical properties in medicine and biomedical fields. Until now, the optimal hBN NP’s dosage and biochemicalmechanism that can be used for in vivo systems has not been fully revealed. The main aim of this article is toreveal characteristics, serum and tissue interactions and any acute cytotoxic effect of different dose of hBNNPs for the first time.Methods: hBN NPs at concentrations varying between 50–3200 mg/kg was administered by intravenousinjection to Wistar albino rats (n ¼ 80) divided into seven dosage and control groups. Blood and tissue sampleswere taken after 24 hours.Results: Our findings suggested that higher doses hBN NPs caused oxidative stress on the serum of rats dosedependently.However, hBN NPs did not affect thiol/disulfide homeostasis on kidney, liver, spleen, pancreas andheart tissue of rats. Furthermore, hBN NPs increased serum disulfide formation by disrupting the thiol/disulfidebalance in rats. Also, LOOH and MPO levels increased at high doses, while CAT levels decreased statistically.Conclusion: The results revealed that hBN NPs induce oxidative stress in a dose-dependent manner bymodulating thiol/disulfide homeostasis in rats at higher concentrations</p

In Vivo Assessment of the Effect of Hexagonal Boron Nitride Nanoparticles on Biochemical, Histopathological, Oxidant and Antioxidant Status

The aim of our study is to investigate the dose-dependent biological system effect of hexagonal boron nitride (hBN) nanoparticles, which is directly produced nanoscale, in vivo. Wistar albino rats (n = 80) weighing 200-250 g were divided into eight groups (n = 10). The acute effects of hBN NPs (i.v) on the rats were investigated by measuring the biochemical, hematological parameters and oxidant-antioxidant status. The results show that no significant change was observed in the hematological and biochemical parameters when the control group and other low dose groups were compared, except for the 1600 and 3200 mu g/kg b.w. dose groups. Histological detection indicated that 1600 and 3200 mu g/kg hBN NPs treatment could induce significant damage in the liver, kidney, heart, spleen and pancreas. With the findings obtained, it can be seen that hBN NPs cannot be evaluated independently of particle morphology, and that the hBN NPs used in this study may be suitable for biomedical applications where low doses between 50 and 800 mu g/kg are not toxic.Eskiehir Technical University Scientific Research Projects Commission [19ADP163]This study was supported by Eskiehir Technical University Scientific Research Projects Commission. (Project No: 19ADP163). The authors would like to thank BORTEK Boron Technologies and Mechatronic Inc. for their material support and Dr. Umut SAVACI for his help to use Transmission Electron Microscopy (TEM) (Eskisehir Technical University, Turkey).WOS:0005330592000012-s2.0-8508501977

In Vivo Assessment of the Effect of Hexagonal Boron Nitride Nanoparticles on Biochemical, Histopathological, Oxidant and Antioxidant Status

The aim of our study is to investigate the dose-dependent biological system effect of hexagonal boron nitride (hBN) nanoparticles, which is directly produced nanoscale, in vivo. Wistar albino rats (n = 80) weighing 200-250 g were divided into eight groups (n = 10). The acute effects of hBN NPs (i.v) on the rats were investigated by measuring the biochemical, hematological parameters and oxidant-antioxidant status. The results show that no significant change was observed in the hematological and biochemical parameters when the control group and other low dose groups were compared, except for the 1600 and 3200 mu g/kg b.w. dose groups. Histological detection indicated that 1600 and 3200 mu g/kg hBN NPs treatment could induce significant damage in the liver, kidney, heart, spleen and pancreas. With the findings obtained, it can be seen that hBN NPs cannot be evaluated independently of particle morphology, and that the hBN NPs used in this study may be suitable for biomedical applications where low doses between 50 and 800 mu g/kg are not toxic