Search Results - (Author, Cooperation:J. M. Drake)

2014-10-25

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Africa, Western/epidemiology ; Ebolavirus/*genetics/isolation & purification ; Epidemiological Monitoring ; Genomics ; Hemorrhagic Fever, Ebola/*epidemiology ; *Human Migration ; Humans ; Travel

2013-04-09

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Cohort Studies ; Databases, Factual/standards ; Dengue/*epidemiology/transmission/virology ; Dengue Virus/physiology ; Global Health/*statistics & numerical data ; Humans ; Incidence ; Public Health/statistics & numerical data ; Quality Control ; Rain ; Risk Factors ; Temperature ; Tropical Climate ; Urbanization ; World Health Organization

2018-01-25

Royal Society

2054-5703

Natural Sciences in General

ecology, health and disease and epidemiology

2018-09-05

The American Association for Cancer Research (AACR)

1078-0432

1557-3265

Medicine

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small-angle x-ray scattering, molecular adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission-electron-microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small-angle x-ray scattering and molecular adsorption. The roughness has an upper cutoff of 〈20 A(ring) which is not resolved in the transmission-electron-microscopy image and is shown to be unimportant to the dynamics of the direct energy transfer process. The dimensionality probed by direct energy transfer is shown to be related to interfacial geometrical crossover from two dimensional to three dimensional, which is characterized by a persistent length of the interface of 45 A(ring).

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The experimentally measured rotational diffusion times of various neutral solute molecules are compared with hydrodynamic and molecular models for microscopic friction. New viscosity and temperature dependent results for the rotational time of a large neutral solute (26 A(ring) long) indicate nearly perfect agreement with stick hydrodynamic predictions in both alkane and alcohol solvents. For smaller solute molecules, the results of previous studies show an increasingly large deviation from hydrodynamic predictions as the solute size decreases. This solute size dependent effect is compared with the theoretical predictions of Zwanzig's hydrodynamic "bumpy cylinder'' model, Dote–Kivelson-Schwartz's molecular free volume model, and a new generalized hydrodynamic model for the effects of frequency dependent viscosity on molecular rotational diffusion. Although hydrodynamic predictions agree with experiment in some respects, it is found that molecular aspects of the solvation process must be introduced in order to get quantitative agreement with the observed solute size dependence.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The decay of the excited singlet state of an aromatic molecule such as naphthalene adsorbed to the surface of silica is nonexponential. This nonexponential decay is shown to result from a multipolar interaction between the excited adsorbate and the intrinsic defects of silica. We present experimental evidence for direct energy transfer between the donor molecules, naphthalene and 2-methoxynaphthalene, and acceptor defects sites of a crystalline silica zeloite (silicalite). The principal condition for direct energy transfer, spectral overlap between the optical absorption of the defects and the fluorescence emission of the adsorbate is demonstrated for this system, and the nonexponential relaxation of the donor is shown to be described by a Forster-type stretched exponential. Based on the spectral overlap and energy transfer rate determined, the intrinsic defect density of silicalite is calculated to be 3±2×1020 cm−3.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The decay of an initially excited donor due to the presence of acceptor molecules embedded in porous silica gels has been studied. The time evolution of the decay process has been related to the geometrical restrictions imposed on the participating molecules by the porous structure of the silicas. Fractal and regular geometrical shape models have been confronted with experimental findings. We conclude that for silica gels simple pore geometries, i.e., spheres and cylinders, account well for the relaxation behavior. The decay patterns exhibit temporal crossovers typical of dynamics in restricted geometries.

Electronic Resource

1747-6593

Blackwell Publishing Journal Backfiles 1879-2005

Energy, Environment Protection, Nuclear Power Engineering

The new Kuala Lumpur International Airport in Malaysia requires substantial works for the management and attenuation of surface-water runoff from a large platform constructed on both high ground and low-lying swamp. This paper describes the key features of the main drainage system and reviews (a) the hydrological context of the scheme, (b) the design principles, and (c) the methodologies which were adopted. The platform drainage works comprise concrete-lined open channels discharging through large balancing ponds into the local rivers. Other components of the scheme include numerous culverts, a river diversion, and an interim system to drain the earthworks’platform prior to completion of the permanent airport drainage. Measures to mitigate the impact of the development, and the application of hydrodynamic modelling in optimizing the system design, are discussed.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We report the results of light scattering, absorption, excitation, and emission spectroscopy of three polyphenylene vinylene (PPV) derivatives; poly[2-methoxy, 5-(2'-ethyl-hexyloxy-p-phenylene- vinylene] (MEH-PPV), poly[2-butoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (BEH-PPV), and poly[2-dicholestanoxy-p-phenylene-vinylene] (BCHA-PPV) in solution with p-xylene. We find that increasing the size of the solubilizing side chains increases the intrinsic persistence length of the polyphenylene vinylene backbone and that this change in stiffness has dramatic effects on the photoluminescence of polyphenylene vinylene. We have determined the luminescence quantum efficiencies of the polyphenylene vinylene derivatives relative to a known standard, Rhodamine 6G, and find that the photoluminescence can be greatly enhanced by increasing the intrinsic stiffness of the polymer backbone. The stiffest polymer, poly[2-dicholestanoxy-p-phenylene-vinylene] (BCHA-PPV), has a quantum efficiency of 0.66±0.05. The quantum efficiency decreases to 0.22±0.05 for poly[2-butoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (BEH-PPV) and 0.20±0.05 for poly[2-methoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (MEH-PPV), the most coiled derivative. Excitation profiles of the three derivatives also show an increase in nonradiative decay at high energies when the polymer assumes a more coiled comformation. Thus, the quantum yields are dependent on pump energy.

Electronic Resource

1432-0533

Brain ; Cyst ; Respiratory epithelium ; Metaplasia

Springer Online Journal Archives 1860-2000

Medicine

Summary An 8.5-year-old female presented with multiple episodes of aseptic meningitis and was found to have a cystic lesion in the prepontine region. Microscopic examination revealed a respiratory-type epithelium with squamous metaplasia. Like its normal analogue in the respiratory tract, the epithelium of these intracranial cysts can undergo squamous metaplasia when chronically irritated. The ultrastructural and immunohistochemical characteristics of the transition from ciliated epithelium to squamous metaplasia are described.

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] THE spatial, temporal and spectral coherence of lasers has made them powerful tools for a dizzying assortment of precise measurements and for the efficient delivery of high optical powers. The lasing threshold is reached when the round-trip gain of the portion of the beam which is FIG. 1 How a ...

Electronic Resource

1433-0350

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1433-0350

Keywords Hydrocephalus ; Cerebrospinal fluid ; Cerebrospinal fluid shunts

Springer Online Journal Archives 1860-2000

Medicine

Abstract  Cerebrospinal fluid (CSF) shunts were invented almost 50 years ago. While their introduction revolutionized the treatment of hydrocephalus, their complications have become legendary, and the focus of much investigation and development of new devices. New devices have been based upon improved understanding of the pathophysiology of hydrocephalus or shunt complications. Despite the rational, or frequently ”more physiological,” functioning of these devices, all too often unexpected complications have ensued, and the initial enthusiasm for the devices has waned. Assessing the efficacy of the devices has been difficult, owing to the lack of properly conducted studies. Nevertheless, the overall impact of shunt design improvements has seemed very limited. A recent randomized trial of CSF shunt design, examining the failure rates of two new and widely used valves (the Cordis Orbis Sigma and the Medtronic PS Medical Delta valves) failed to find any advantage of these over standard valve designs, many of which have been used almost since the inception of CSF shunts. A search for risk factors for failure, in a post hoc analysis of the data, indicated only that the etiology of the hydrocephalus and the position and local environment of the ventricular catheter tip were probably important. Remarkably, the rate of change in the size of the ventricles and the final ventricular size were not different despite the substantial differences in flow characteristics of the two new valves. Shunt failure rates of less than 5% at 1 year, with infection rates of less than 1%, seem like reasonable goals for the next decade in the new millenium. This can be achieved through basic research into the pathophysiology of shunt failure with improved mathematical models, and perhaps animal models of shunt failure. Efficacy of new devices or treatments must be scrutinized scientifically so as not to waste valuable resources and time on unproven treatments. Uncontrolled series and testimonial assertions about new treatments or devices, especially from proponents with a vested interest, should be regarded with great skepticism. Nevertheless, our best efforts are likely to result in a major advance in the management of pediatric hydrocephalus, which now seems tantalizingly close.

Electronic Resource