6,332 publications from this institution
An atomic force microscope (AFM) has been used to machine complex patterns and to form free structural objects in thin layers of MoO(3) grown on the surface of MoS(2). The AFM tip can pattern lines with </=10-nanometer resolution and then image the resulting structure without perturbation by controlling the applied load. Distinct MoO(3) structures can also be defined by AFM machining, and furthermore these objects can be manipulated on the MoS(2) substrate surface with the AFM tip. These results suggest application to nanometer-scale diffraction gratings, high-resolution lithography masks, and possibly the assembly of nanostructures with novel properties.
Nanoscale materials enable unique opportunities at the interface between the physical and life sciences, and the interface between nanoelectronic devices and biological systems makes possible communication between these two diverse systems at the length scale relevant to biological function. In this presentation, the development of nanowire nanoelectronic devices and their application as powerful tools for the life sciences will be discussed. First, a brief introduction to nanowire nanoelectronic devices as well as comparisons to other electrophysiological tools will be presented to illuminate the unique strengths and opportunities enabled at the nanoscale. Second, illustration of detection capabilities including signal-to-noise and applications for real-time label-free detection of biochemical markers down to the level of single molecules will be described. Third, the use of nanowire nanoelectronics for building interfaces to cells and tissues will be reviewed. Multiplexed measurements made from nanowire devices fabricated on flexible and transparent substrates recording signal propagation across cultured cells, acute tissue slices and intact organs will be illustrated, including quantitative analysis of the high simultaneous spatial and temporal resolution achieved with these nanodevices. Specific examples of subcellular and near point detection of extracellular potential will be used to illustrate the unique capabilities, such as recording localized potential changes due to neuronal activities simultaneously across many length scales, which provide key information for functional neural circuit studies. Last, emerging opportunities for the creation of powerful new probes based on controlled synthesis and/or bottom-up assembly of nanomaterials will be described with an emphasis on the creation of kinked nanowire probes capable of first intracellular transistor recordings. The prospects for blurring the distinction between nanoelectronic and living systems in the future will be highlighted.
We apply the J -integral to free-boundary flows in a channel geometry such as viscous fingering or blob injection in Hele-Shaw cells, void propagation in electromigration, and injection of air bubbles into inviscid liquids. The theory of that and related conservation integrals, developed in elasticity, is outlined in a way that is applicable to fluid mechanics problems. Depending on the boundary conditions, for infinite bubbles in Laplacian fields we are able to use the J -integral to predict finger width if such solutions exist or to predict that there are no solutions. For finite sized bubbles, bounds can sometimes be derived. In the case of Hele-Shaw flows, in which solutions appear as a continuum, finger width cannot be constrained, but we do obtain a new derivation and generalization of Richardson moment conservation. Applications to vortex motion are also outlined briefly.
The authors propose a grid-based subtree-subcube assignment strategy for solving PDE problems on hypercubes. A complexity analysis of the communication is given for the proposed approach and the standard subtree-subcube assignment when applied to a variant of nested dissection indexing and a nonsymmetric sparse solver. The new assignment reduces communication cost using p processors by a factor of $O(\log p)$ in message startups and a factor of about two in traffic volume. Using a modified nested dissection indexing, the total effect on message startups is a reduction by a factor of $O(\log N)$ compared to previous approaches, where N is the number of unknowns. This grid-based assignment strategy achieves the optimal order in both traffic volume and startups; it provides good load balancing and as much parallelism as is inherent in the underlying algorithm. Some experimental results are presented which confirm the increased communication efficiency.
Nanoskiving is a novel and inexpensive method that has been used to fabricate both isolated nanostructures and ordered arrays of nanostructures. The dimensions of the nanostructures are determined by i) the thickness of the deposited thinfilm (tens of nanometers), ii) the topography (sub-μm, using soft lithography) of the surface onto which the thin-film is deposited, and iii) the thickness of the section cut by the microtome (> 30 nm by ultramicrotomy). Nanoskiving can fabricate complex nanostructures that are difficult or impossible to achieve by other methods of nanofabrication. These include multilayer structures, structures on curved surfaces, structures that span gaps, structures in less familiar materials, structures with high aspect ratios, and large-area structures comprising two-dimensional periodic arrays. In this paper, we described the history, procedure, and applications, particularly in nanophotonics, of nanoskiving.
For crack-tip speeds which are even a modest fraction of the lowest elastic wave speed of a material, the strain rates that are induced at material points close to the crack tip are enormous. Experimental evidence is available which suggests that the flow stress is a fairly strong function of plastic strain rate at the rates anticipated. An approximate analysis of the high-strain-rate crack-growth process has been developed on the basis of this observation, which is interpreted as implying that the elastic strain rates dominate the plastic strain rates. The features of the approximate analysis are reviewed, and the results of more recent complete numerical analysis of the same crack-growth model are described. Using the growth of a macroscopic cleavage crack in mild steel as a vehicle for discussing the model, it is found that the approximate model appears to capture the essence of the process for those temperatures at which cleavage crack growth is supported. The numerical results indicate deficiencies in the approximate analysis for higher temperatures.
A minimum-weight flexural actuator is designed. The actuator comprises a triangular corrugated core with shape memory alloy (SMA) faces. It is clamped at one end and free at the other. For design and optimization, the temperature history of the face sheets upon heating and subsequent cooling is first obtained as a function of the cooling efficiency (Biot number) and the operational frequency deduced. Based upon this response, a phenomenological model is employed to represent the martensite evolution. Thereafter, the end deflection is calculated as a function of temperature. The minimum weight is calculated subject to the provisos that: (i) the end deflection attains a specified value; (ii) the power consumed is less than the upper limit of the supply; and failure is averted by (iii) face/core yielding and (iv) face/core buckling; (v) the operational frequency of the panel achieves a specified limit.
The influence of adiposity over life course on cancer risk remains poorly understood. We assessed trajectories of body shape from age 5 up to 60 using a group‐based modeling approach among 73,581 women from the Nurses' Health Study and 32,632 men from the Health Professionals Follow‐up Study. After a median of approximately 10 years of follow‐up, we compared incidence of total and obesity‐related cancers (cancers of the esophagus [adenocarcinoma only], colorectum, pancreas, breast [after menopause], endometrium, ovaries, prostate [advanced only], kidney, liver and gallbladder) between these trajectories. We identified five distinct trajectories of body shape: lean‐stable, lean‐moderate increase, lean‐marked increase, medium‐stable, and heavy‐stable/increase. Compared with women in the lean‐stable trajectory, those in the lean‐marked increase and heavy‐stable/increase trajectories had a higher cancer risk in the colorectum, esophagus, pancreas, kidney, and endometrium (relative risk [RR] ranged from 1.22 to 2.56). Early life adiposity was inversely while late life adiposity was positively associated with postmenopausal breast cancer risk. In men, increased body fatness at any life period was associated with a higher risk of esophageal adenocarcinoma and colorectal cancer (RR ranged from 1.23 to 3.01), and the heavy‐stable/increase trajectory was associated with a higher risk of pancreatic cancer, but lower risk of advanced prostate cancer. The trajectory‐cancer associations were generally stronger for non‐smokers and women who did not use menopausal hormone therapy. In conclusion, trajectories of body shape throughout life were related to cancer risk with varied patterns by sex and organ, indicating a role for lifetime adiposity in carcinogenesis.
