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 …

I and i

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.

Fast parallel algorithms for short-range molecular dynamics

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

In the last 10 years the field of molecular diagnostics has witnessed an explosion of interest in the use of nanomaterials in assays for gases, metal ions, and DNA and protein markers for many diseases. Intense research has been fueled by the need for practical, robust, and highly sensitive and selective detection agents that can address the deficiencies of conventional technologies. Chemists are playing an important role in designing and fabricating new materials for application in diagnostic assays. In certain cases assays based upon nanomaterials have offered significant advantages over conventional diagnostic systems with regard to assay sensitivity, selectivity, and practicality. Some of these new methods have recently been reviewed elsewhere with a focus on the materials themselves or as subclassifications in more generalized overviews of biological applications of nanomaterials.1-7 We intend to review some of the major advances and milestones in the field of detection systems based upon nanomaterials and their roles in biodiagnostic screening for nucleic acids, * To whom correspondence should be addressed. Phone: 847-4913907. Fax: 847-467-5123. E-mail: chadnano@northwestern.edu. Nathaniel L. Rosi earned his B.A. degree at Grinnell College (1999) and his Ph.D. degree from the University of Michigan (2003), where he studied the design, synthesis, and gas storage applications of metal−organic frameworks under the guidance of Professor Omar M. Yaghi. In 2003 he began postdoctoral studies as a member of Professor Mirkin’s group at Northwestern University. His current research focuses on the rational assembly of DNA-modified nanostructures into larger-scale materials.

/pdf/nanostructures-in-biodiagnostics-5553cs9yqw.pdf

Nanostructures in Biodiagnostics

Etching of GaAs in a magnetron reactor was investigated using two different etch gases, namely SiCl4 and freon‐12 (CF2Cl2). SiCl4 etching yielded vertical sidewalls, whereas the etched profiles in the case of freon exhibited a negative undercut. Surface characterization was undertaken using Auger electron spectroscopy, x‐ray photoelectron spectroscopy, and secondary ion mass spectroscopy to determine the composition and chemical bonding in the near‐surface region of the etched samples. The etched surface in the case of SiCl4 was found to be free of any chlorine residue and predominantly GaAs. However, there were residues of Si on the sidewalls. GaF3 formation was observed in GaAs samples etched in freon‐12; in addition a CxFy fluorocarbon layer was present at high pressures which may not have been effectively removed due to reduced ion bombardment.

Magnetron etching of GaAs: Etch characteristics and surface characterization

Method and system for detecting presence of biomolecules in a selected subset, or in each of several selected subsets, in a fluid. Each of an array of two or more carbon nanotubes (“CNTs”) is connected at a first CNT end to one or more electronics devices, each of which senses a selected electrochemical signal that is generated when a target biomolecule in the selected subset becomes attached to a functionalized second end of the CNT, which is covalently bonded with a probe molecule. This approach indicates when target biomolecules in the selected subset are present and indicates presence or absence of target biomolecules in two or more selected subsets. Alternatively, presence of absence of an analyte can be detected.

/pdf/biochemical-sensors-using-carbon-nanotube-arrays-5ezqpiy0bl.pdf

Biochemical sensors using carbon nanotube arrays

The effect of altering the dc magnetic field on plasma properties and wave characteristics in a helicon source is studied. A two-dimensional, numerical model with self-consistency between wave propagation, including the Trivelpiece–Gould mode, and plasma transport is used. A parametric study is carried out to ascertain the magnetic field profile effects on wave propagation, peripheral versus bulk power absorption, plasma density, uniformity, temperature and potential. It is found that diffusion of plasma and power absorption away from the radio frequency antenna can be enhanced by adjusting the magnetic field profile. The effect on plasma uniformity qualitatively agrees with the measured data in the literature.

https://iopscience.iop.org/article/10.1088/0963-0252/13/4/001/pdf

Modelling of magnetic field profile effects in a helicon source

Bandgap engineering of single-crystalline alloy CdxZn1−xTe (0 ≤ x ≤ 1) nanowires is achieved successfully through control of growth temperature and a two zone source system in a vapor–liquid–solid process. Extensive characterization using electron microscopy, Raman spectroscopy and photoluminescence shows highly crystalline alloy nanowires with precise tuning of the bandgap. It is well known that bulk CdxZn1−xTe is popular for construction of radiation detectors and availability of a nanowire form of this material would help to improve detection sensitivity and miniaturization. This is a step forward towards the accomplishment of tunable and predetermined bandgap emissions for various applications.

Bandgap engineering of CdxZn1−xTe nanowires

We investigated the doping effects of chemical functionalization on graphene field-effect transistors (G-FETs). A pyrene backbone with an electron-withdrawing group (1-pyrenebutanoic acid succinimidyl ester, PBASE) and DMF acting as a solvent were used. The pyrene derivative was stably immobilized onto the graphene surface via π-π stacking between the two highly conjugated systems, confirmed by electric measurements with different incubation times and linker molecule concentrations. Dimethyl formamide (DMF) can decrease the conductivity of the FET devices and showed an n-doping effect while the pyrene derivative showed a p-doping effect. Because of this, the functionalization with PBASE in DMF could be regarded as a competitive process. This study provides a new insight into chemical functionalization with aromatic molecule, and understanding of doping effects about electron donor and electron acceptor on graphene during the functionalization process.

Meyya Meyyappan

Papers

Magnetron etching of GaAs: Etch characteristics and surface characterization

Biochemical sensors using carbon nanotube arrays

Modelling of magnetic field profile effects in a helicon source

Bandgap engineering of CdxZn1−xTe nanowires

Chemical functionalization of graphene with aromatic molecule