Metallic glasses deform elastically under stress. However, the atomic-level origin of elastic properties of metallic glasses remain unclear. In this Letter using ab initio molecular dynamics ...simulations of the Cu_{50}Zr_{50} metallic glass under shear strain, we show that the heterogeneous stress relaxation results in the increased charge transfer from Zr to Cu atoms, enhancing the softening of the shear modulus. Changes in compositional short-range order and atomic position shifts due to the nonaffine deformation are discussed. It is shown that the Zr subsystem exhibits a stiff behavior, whereas the displacements of Cu atoms from their initial positions, induced by the strain, provide the stress drop and softening.
Using high-energy X-ray diffraction we study structural changes in bulk metallic glasses after uniaxial compressive homogeneous deformation at temperatures slightly below the glass transition. We ...observe that deformation results in structural disordering corresponding to an increase in the fictive, or effective, temperature. However, the structural disordering saturates after yielding. Examination of the experimental structure and molecular dynamics simulation suggests that local changes in the atomic connectivity network are the main driving force of the structural rejuvenation.
Liquids are ubiquitous, but the atomic origin of viscosity remains unknown because of structural disorder and dynamic complexities. By using molecular dynamics simulation for liquid iron, we find a ...strong local correlation between the atomic-level pressure and the relaxation of atomic-level shear stress that is directly connected to viscosity. The results show that atomic sites under compression are more unstable against shear than those under tension, which causes fast relaxation in atomic-level shear stress. This result indicates spatial heterogeneities in the local viscosity in a liquid. We also find a temperature-independent relation between the local shear relaxation time and atomic-level volume strain, which suggests a universal structure-dynamics relationship in liquids. To explain our new findings, we discuss the relationships between the atomic-level pressure and various other parameters, such as the atomic-level shear stress, von Mises stress, local coordination number, and mean-squared displacements of atoms.
Selective cannulation fails in approximately 3 % of endoscopic retrograde cholangiography (ERC) procedures. An endoscopic ultrasound-guided rendezvous technique (EUS - RV) may salvage failed ...cannulation. The aims of the current study were to determine the safety and efficacy of EUS - RV.
A total of 40 patients underwent salvage EUS - RV. EUS - RV was attempted immediately after failed biliary cannulation. A dilated intra- or extra-hepatic biliary duct (IHBD or EHBD) was punctured from the stomach or the small intestine under EUS guidance followed by cholangiography and antegrade manipulation of the guide wire into the small intestine. Finally, the echoendoscope was exchanged for an appropriate endoscope and biliary cannulation was achieved over or adjacent to the guide wire.
EUS-RV appears safe and effective and may be considered as a primary salvage technique after failed cannulation. Antegrade manipulation of the guide wire into the small intestine was achieved in 29 of 40 patients (73 %; EHBD 25 /31 and IHBD 4/9). The reasons for failure were inability to advance the guide wire through an obstruction or a native ampulla. Re-attempt at ERC immediately after failed EUS - RV was made in seven of the 11 patients, and was successful in four. The remaining seven patients underwent percutaneous drainage within 3 days. Complications occurred in five patients (13 %), including pancreatitis, abdominal pain, pneumoperitoneum, and sepsis/death, which was unlikely to be related to the procedure.
EUS - RV is safe and effective and should be considered as a primary salvage technique after failed cannulation. Immediate re-attempt at ERC after failed EUS - RV is warranted, as EUS-guided cholangiogram can facilitate biliary cannulation in some cases. Finally, prompt alternative biliary drainage should be available.
The diagnosis of mediastinal and intra-abdominal lymphadenopathy is sometimes difficult, especially in patients who have no other primary lesions. Lymphoma is one of the main causes of this ...condition. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is a safe and accurate diagnostic procedure for lesions surrounding the gastrointestinal tract. However, diagnosing lymphoma using the EUS-FNA technique remains a diagnostic challenge, due to limitations in the amount of material sampled. The aim of the present study was to evaluate the yield of EUS-FNA biopsy (EUS-FNAB) using a large-gauge needle in patients with mediastinal and intra-abdominal lymphadenopathy of unknown origin, especially in relation to subclassification of the lymphomas.
Consecutive patients with mediastinal and intra-abdominal lymphadenopathy of unknown origin who were referred between October 2003 and March 2005 were enrolled in the study. EUS-FNAB was carried out using a 19-gauge needle, passing through the esophageal, gastric, and duodenal walls. Pathological diagnoses were made on the basis of histological findings, including immunopathological staining.
A total of 104 patients were included in the study. The locations of the lymph nodes were mediastinal in 50 patients, intra-abdominal in 48 patients, and both mediastinal and intra-abdominal in six patients. The diagnoses made using EUS-FNAB were lymphoma (n = 48), metastasis (n = 16), and benign/reactive (n = 40). The overall accuracy of EUS-FNAB for unknown lymphadenopathy was 98 %, and it was possible to classify the lymphomas in accordance with the World Health Organization classifications in 88 % of cases. No serious complications occurred with the procedure.
Open thoracic surgery, laparotomy, and other invasive diagnostic procedures such as mediastinoscopy and laparoscopy can now be avoided, as EUS-FNAB is potentially a safe and accurate tool for diagnosing unknown lymphadenopathy, including lymphoma.
Arabidopsis halleri is a Cd hyperaccumulator; however, the mechanisms involved in the root to shoot translocation of Cd are not well understood. In this study, we characterized Cd transfer from the ...root medium to xylem in this species. Arabidopsis halleri accumulated 1,500 mg kg−1 Cd in the shoot without growth inhibition. A time-course experiment showed that the release of Cd into the xylem was very rapid; by 2 h exposure to Cd, Cd concentration in the xylem sap was 5-fold higher than that in the external solution. The concentration of Cd in the xylem sap increased linearly with increasing Cd concentration in the external solution. Cd transfer to the xylem was completely inhibited by the metabolic inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Cd concentration in the xylem sap was decreased by increasing the concentration of external Zn, but enhanced by Fe deficiency treatment. Analysis with 113Cd-nuclear magnetic resonance (NMR) showed that the chemical shift of 113Cd in the xylem sap was the same as that of Cd(NO3)2. Metal speciation with Geochem-PC also showed that Cd occurred mainly in the free ionic form in the xylem sap. These results suggest that Cd transfer from the root medium to the xylem in A. halleri is an energy-dependent process that is partly shared with Zn and/or Fe transport. Furthermore, Cd is translocated from roots to shoots in inorganic forms.
Abstract Background If tracheal intubation can be performed during uninterrupted chest compressions, this will sustain circulation during the procedure of intubation and may lead to successful ...resuscitation. We compared three types of laryngoscope on a manikin as to whether they enabled tracheal intubation while the manikin's chest was rhythmically compressed. Methods A total of 35 persons who had little or no experience in intubation served as examinees. The laryngoscopes employed were a conventional Macintosh laryngoscope (MAC), a new video laryngoscope, Pentax-AWS (AWS) and an optic laryngoscope Airtraq (ATQ). During chest compression on the manikin by an assistant, the examinee attempted to perform intubation. The success rate and the time for successful intubation were measured. Results During rhythmic chest compressions, nine examinees failed in tracheal intubation with the MAC, seven failed with the ATQ, and no one failed with the AWS. The success rates with the AWS were significantly higher than those with the MAC ( P < 0.01) or ATQ ( P < 0.05). The time needed for intubation was significantly shorter with the Pentax-AWS than with the others. Conclusions These results suggest that the use of the Pentax-AWS enables tracheal intubation while the patient's chest is rhythmically compressed, and would more often lead to successful intubation, which in turn may lead to more successful resuscitation.
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