37 research outputs found
Characterizing the mechanical response of metallic glasses to uniaxial tension using a spring network model
Metallic glasses are frequently used as structural materials. Therefore, it
is important to develop methods to predict their mechanical response as a
function of the microstructure prior to loading. We develop a coarse-grained
spring network model, which describes the mechanical response of metallic
glasses using an equivalent series network of springs, which can break and
re-form to mimic atomic rearrangements during deformation. To validate the
model, we perform simulations of quasistatic, uniaxial tension of Lennard-Jones
and embedded atom method (EAM) potentials for CuZr metallic
glasses. We consider samples prepared using a wide range of cooling rates and
with different amounts of crystalline order. We show that both the
Lennard-Jones and EAM models possess qualitatively similar stress
versus strain curves. By specifying five parameters in the spring
network model (ultimate strength, strain at ultimate strength, slopes of
at and at large strain, and strain at fracture
where ), we can accurately describe the form of the stress-strain
curves during uniaxial tension for the computational studies of
CuZr, as well as recent experimental studies of several Zr-based
metallic glasses. For the computational studies of CuZr, we find
that the yield strain distribution is shifted to larger strains for slowly
cooled glasses compared to rapidly cooled glasses. In addition, the average
number of new springs and their rate of formation decreases with decreasing
cooling rate. These effects offset each other at large strains, causing the
stress-strain curve to become independent of the sample preparation protocol in
this regime. In future studies, we will extract the parameters that define the
spring network model directly from atomic rearrangements that occur during
uniaxial deformation.Comment: 16 pages, 13 figure
Development and potential role of type-2 sodium-glucose transporter inhibitors for management of type 2 diabetes
There is a recognized need for new treatment options for type 2 diabetes mellitus (T2DM). Recovery of glucose from the glomerular filtrate represents an important mechanism in maintaining glucose homeostasis and represents a novel target for the management of T2DM. Recovery of glucose from the glomerular filtrate is executed principally by the type 2 sodium-glucose cotransporter (SGLT2). Inhibition of SGLT2 promotes glucose excretion and normalizes glycemia in animal models. First reports of specifically designed SGLT2 inhibitors began to appear in the second half of the 1990s. Several candidate SGLT2 inhibitors are currently under development, with four in the later stages of clinical testing. The safety profile of SGLT2 inhibitors is expected to be good, as their target is a highly specific membrane transporter expressed almost exclusively within the renal tubules. One safety concern is that of glycosuria, which could predispose patients to increased urinary tract infections. So far the reported safety profile of SGLT2 inhibitors in clinical studies appears to confirm that the class is well tolerated. Where SGLT2 inhibitors will fit in the current cascade of treatments for T2DM has yet to be established. The expected favorable safety profile and insulin-independent mechanism of action appear to support their use in combination with other antidiabetic drugs. Promotion of glucose excretion introduces the opportunity to clear calories (80–90 g [300–400 calories] of glucose per day) in patients that are generally overweight, and is expected to work synergistically with weight reduction programs. Experience will most likely lead to better understanding of which patients are likely to respond best to SGLT2 inhibitors, and under what circumstances