Observations of transient high temperature vortical microstructures in solids during adiabatic shear banding

By using a unique infrared high-speed camera especially constructed for recording highly transient temperature fields at the microscale, we are able to reveal the spatial and temporal microstructure within dynamically growing shear bands in metals. It is found that this structure is highly nonuniform and possesses a transient, short range periodicity in the direction of shear band growth in the form of an array of intense "hot spots" reminiscent of the well-known, shear-induced hydrodynamic instabilities in fluids. This is contrary to the prevailing classical view that describes the deformations and the temperatures within shear bands as being essentially one-dimensional fields. These observations are also reminiscent of the nonuniform structure of localized shear regions believed to exist, at an entirely different length scale, in the earth's lower crust and upper mantle

Million frames per second infrared imaging system

An infrared imaging system has been developed for measuring the temperature increase during the dynamic deformation of materials. The system consists of an 8×8 HgCdTe focal plane array, each with its own preamplifier. Outputs from the 64 detector/preamplifiers are digitized using a row-parallel scheme. In this approach, all 64 signals are simultaneously acquired and held using a bank of track and hold amplifiers. An array of eight 8:1 multiplexers then routes the signals to eight 10 MHz digitizers, acquiring data from each row of detectors in parallel. The maximum rate is one million frames per second. A fully reflective lens system was developed, consisting of two Schwarszchild objectives operating at infinite conjugation ratio. The ratio of the focal lengths of the objectives determines the lens magnification. The system has been used to image the distribution of temperature rise near the tip of a notch in a high strength steel sample (C-300) subjected to impact loading by a drop weight testing machine. The results show temperature rises at the crack tip up to around 70 K. Localization of temperature, and hence, of deformation into "U" shaped zones emanating from the notch tip is clearly seen, as is the onset of crack propagation

Real-time Measurement of Stress and Damage Evolution During Initial Lithiation of Crystalline Silicon

Crystalline to amorphous phase transformation during initial lithiation in (100) silicon-wafers is studied in an electrochemical cell with lithium metal as the counter and reference electrode. It is demonstrated that severe stress jumps across the phase boundary lead to fracture and damage, which is an essential consideration in designing silicon based anodes for lithium ion batteries. During initial lithiation, a moving phase boundary advances into the wafer starting from the surface facing the lithium electrode, transforming crystalline silicon into amorphous LixSi. The resulting biaxial compressive stress in the amorphous layer is measured in situ and it was observed to be ca. 0.5 GPa. HRTEM images reveal that the crystalline-amorphous phase boundary is very sharp, with a thickness of ~ 1 nm. Upon delithiation, the stress rapidly reverses, becomes tensile and the amorphous layer begins to deform plastically at around 0.5 GPa. With continued delithiation, the yield stress increases in magnitude, culminating in sudden fracture of the amorphous layer into micro-fragments and the cracks extend into the underlying crystalline silicon.Comment: 12 pages, 5 figure

Orientation-dependent adhesion strength of a rigid cylinder in non-slipping contact with a transversely isotropic half-space

Recently, Chen and Gao [Chen, S., Gao, H., 2007. Bio-inspired mechanics of reversible adhesion: orientation-dependent adhesion strength for non-slipping adhesive contact with transversely isotropic elastic materials. J. Mech. Phys. solids 55, 1001–1015] studied the problem of a rigid cylinder in non-slipping adhesive contact with a transversely isotropic solid subjected to an inclined pulling force. An implicit assumption made in their study was that the contact region remains symmetric with respect to the center of the cylinder. This assumption is, however, not self-consistent because the resulting energy release rates at two contact edges, which are supposed to be identical, actually differ from each other. Here we revisit the original problem of Chen and Gao and derive the correct solution by removing this problematic assumption. The corrected solution provides a proper insight into the concept of orientation-dependent adhesion strength in anisotropic elastic solids

A prospective study on the prescription pattern of anti-cancer drugs and adverse drug reaction in a tertiary care hospital

Background: Cancers is a group of disease involving abnormal cell multiplication with the ability to spread to other parts of the body. Common side effects seen with chemotherapy are fatigue, hair loss, easy bruising and bleeding, infection, anemia, nausea and vomiting, appetite changes, constipation etc. The need of this study is to evaluate the prescribing pattern and the adverse drug reaction associated with chemotherapeutic drugs. The study is aimed to analyze the prescribing pattern of anticancer drugs in medical oncology department of a tertiary care hospital, Karnataka.Methods: An observational study was conducted on 30 patients of either sex admitted for chemotherapy for a period of 6 months in at HCG Cancer Institute, Gulbarga and Basaveshwar Teaching and General Hospital (BTGH), Gulbarga. The data collected is analysed statistically using descriptive statistics and presented as counts and percentages. Results are depicted in the form of tables.Results: A total of 30 prescriptions were collected with 10 (33.3%) male and 20 (66.6%) female. the maximum number of cases were noted in the age group of 46years to 55 years (10) and least in age group of 15-25 years having a single patient. In our study we found that more number of patients are breast cancer (12 patients) followed by cervical cancer and ovarian cancer (3 patients) and least are Ewing’s sarcoma and Non-Hodgkin’s lymphoma (1 patient). Most commonly prescribed anti-cancer drug is carboplatin and paclitaxel i.e. for 12 patients out of 30 patients, followed by cyclophosphamide for 10 patients and less commonly prescribed drug being dactinomycin and pemitrexate. Adverse drug reactions seen in maximum patients is hair loss among 20 pts followed by peripheral neuropathy (17) and taste change (16) and the less commonly noted side effects being chest pain and ototoxicity.Conclusions: The study concluded that the drugs which were used in the treatment of various neoplastic conditions are in adherence and in accordance with the standard treatment guidelines and most of them were prescribed with generic name which leads to reduce in cost of treatment