Daryoosh Vashaee

Bio: Daryoosh Vashaee is an academic researcher from North Carolina State University. The author has contributed to research in topics: Thermoelectric effect & Thermoelectric materials. The author has an hindex of 48, co-authored 225 publications receiving 15724 citations. Previous affiliations of Daryoosh Vashaee include University of California, Santa Cruz & Oklahoma State University–Tulsa.

Determination of total aflatoxin using cysteamine-capped CdS quantum dots as a fluorescence probe

Abstract: Aflatoxins form a class of potent carcinogens that contaminate a wide range of food products and can be fatal to humans and livestock. We have designed cysteamine-capped CdS quantum dots (QDs) to serve as aflatoxin photodetectors for use in agricultural industries. Water-soluble CdS QDs are synthesized through growth in a poly(vinyl alcohol) matrix using a chemical precipitation method. The prepared QDs are then characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) analyses. The obtained results revealed that these CdS QDs have a 1- to 2-nm crystalline size, hexagonal wurtzite structure, and spherical morphology with a diameter less than 10 nm. Photoluminescence spectroscopy (PL) is performed to study the CdS QDs interactions with a standard solution of aflatoxins (B1, B2, G1, and G2 in a ratio of 5:1:5:1) in order to determine their effectiveness as aflatoxin detectors. A green emission peak is observed at 508 nm, with an intensity enhancement positively correlated with total aflatoxin concentration. The lower limit of detection for total aflatoxin concentration is found to be 0.05 ppb, well below international contamination allowances for food products. PL variations with aflatoxin concentration are best described by a Langmuir-type equation in the concentration range of this study (2.4–48 ppb).

Innovative surface modification of orthopaedic implants with positive effects on wettability and in vitro anti-corrosion performance

Abstract: In this work, sol–gel derived bioactive glass/zirconium titanate coatings were uniformly deposited on stainless steel orthopaedic implants, by using carboxymethyl cellulose as a particulate dispersant in the sol. The surface features, wetting, and in vitro electrochemical corrosion behaviour of the coated samples were evaluated. It was found that, by applying the coating on the substrate, the water contact angle was decreased, which is indicative of an improvement in the implant hydrophilicity. Also, the coating improved the corrosion resistance of the metallic implant, as realised by an increase in the corrosion potential and a decrease in the corrosion current density. Indeed, this coating acted as a physical protective barrier which retards the electrolyte access to the metal surface and thereby electrochemical processes.

Stability of uni- and multillamellar spherical vesicles.

Abstract: Lipid molecules in water form uni- or multilamellar vesicles in polydisperse form. Herein, we present energetic considerations for their equilibrium morphological organization. Our formulation provides elemental energy diagrams, which explain the polydispersity and account for the structural diversity. These energy diagrams describe the ranges of core radius (r(c)) and number of lamellae (N) that result in the formation of stable vesicles under specific conditions, thus providing prescriptions for the design of vesicles tailored for specific properties, including stability, cargo capacity, and resistance to deformation by osmotic stress. We deduced key design criteria as follows: 1) designing highly stable unilamellar vesicles requires low bending rigidity lipids and dimensions exceeding a few hundred nm in radii; 2) very large unilamellar vesicles (r(c)>several tens of microns) are not stable for typical lipids; lipids with higher bending rigidity are required; 3) the distribution of the stable size of vesicles is proportional to the bending rigidity; 4) for the case of multilamellar vesicles, vesicles with more than a few hundred layers usually exhibit greater structural integrity than those with lower degrees of lamellarity, especially when the core radii are small ( mM) is the most dominant factor in the free energy, suggesting active response by vesicles (e.g., poration) to release osmotic stress; and 6) vesicles with a core radius of a few hundred nm and more than hundred lamellae are more resistant to deformation by osmotic stress, thus making them more suited to applications involving osmotic pressure gradients, such as in drug delivery.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Complex thermoelectric materials.

Abstract: Thermoelectric materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, could play an important role in a global sustainable energy solution. Such a development is contingent on identifying materials with higher thermoelectric efficiency than available at present, which is a challenge owing to the conflicting combination of material traits that are required. Nevertheless, because of modern synthesis and characterization techniques, particularly for nanoscale materials, a new era of complex thermoelectric materials is approaching. We review recent advances in the field, highlighting the strategies used to improve the thermopower and reduce the thermal conductivity.