Optimum pulse duration and radiant exposure for vascular laser therapy of dark port-wine skin: a theoretical study

Laser therapy for cutaneous hypervascular malformations such as port-wine stain birthmarks is currently not feasible for dark-skinned individuals. We study the effects of pulse duration, radiant exposure, and cryogen spray cooling (CSC) on the thermal response of skin, using a Monte Carlo based optical-thermal model. Thermal injury to the epidermis decreases with increasing pulse duration during irradiation at a constant radiant exposure; however, maintaining vascular injury requires that the radiant exposure also increase. At short pulse durations, only a minimal increase in radiant exposure is necessary for a therapeutic effect to be achieved because thermal diffusion from the vessels is minimal. However, at longer pulse durations the radiant exposure must be greatly increased. There exists an optimum pulse duration at which minimal damage to the epidermis and significant injury within the targeted vasculature occur. For example, the model predicts optimum pulse durations of approximately 1.5, 6, and 20 ms for vessel diameters of 40, 80, and 120 microm, respectively. Optimization of laser pulse duration and radiant exposure in combination with CSC may offer a means to treat cutaneous lesions in dark-skinned individuals.     

Ammonium Perchlorate,Friend or Foe?

In part 1 of this paper, it was demonstrated that a nitroglycerine and polyethylene glycol based propellant containing ammonium perchlorate degraded at a slower rate at temperatures of 80 °C or less compared with the other two energetic materials studied which did not have this oxidizer present. It was suggested that ammonium perchlorate might act as an oxygen inhibitor reducing the oxidation rate of the polyethylene glycol binder which decreases the rate of propellant decomposition. In part 2, the specific interaction between ammonium perchlorate, nitroglycerine and polyethylene glycol is reported. It has been shown that at temperatures lower than 90 °C, if there is any uncured and unstabilised PEG present, nitroglycerine rapidly degrades in the presence of ammonium perchlorate but this is prevented if stabiliser is added. In addition, ammonium perchlorate initially appears to hinder acid hydrolysis of nitroglycerine which also slows down the degradation of polyethylene glycol based propellants. However, in the long term at low temperatures, or short term at higher temperatures, AP accelerates the decomposition of NG.     

Modulation of in vivo tumor radiation response via gold nanoshell-mediated vascular-focused hyperthermia: characterizing an integrated antihypoxic and localized vascular disrupting targeting strategy

We report noninvasive modulation of in vivo tumor radiation response using gold nanoshells. Mild-temperature hyperthermia generated by near-infrared illumination of gold nanoshell-laden tumors, noninvasively quantified by magnetic resonance temperature imaging, causes an early increase in tumor perfusion that reduces the hypoxic fraction of tumors. A subsequent radiation dose induces vascular disruption with extensive tumor necrosis. Gold nanoshells sequestered in the perivascular space mediate these two tumor vasculature-focused effects to improve radiation response of tumors. This novel integrated antihypoxic and localized vascular disrupting therapy can potentially be combined with other conventional antitumor therapies.     

Printing-induced improvements of organic thin-film transistors

To understand the observation of improved pentacene (Pn) thin-film transistor mobility in flexible printed devices, a method for performing electrical measurements of organic thin-film transistors (OTFT) during the process of transfer printing has been developed. Different sample configurations were designed to test two aspects of the printing process: (1) the formation of the source/drain contacts a Pn thin-film, and (2) the formation of the transfer printed Pn/dielectric interface. In situ measurements show that pressure-induced contacts of gold (Au) electrodes result in a factor of seven mobility improvement compared with evaporation of top Au electrodes on an otherwise identical device configuration. Annealing the laminated device up to 90 °C caused no further improvement, and heating above 90 °C degraded performance. The mobility of a transfer printed device with the rough, as-grown top surface of the Pn in contact with the dielectric was found to increase dramatically with subsequent annealing for a sample temperature up to 120 °C. This is attributed to annealing-induced structural changes in the Pn film at elevated temperatures, consistent with X-ray bulk measurements showing enhanced crystal morphology in transfer printed Pn thin-films.     

Three dimensions of naturalness: An expanded definition of field research.

Reviews several definitions of field research, and presents an expanded framework for conceptualizing field research. Three theoretically independent dimensions commonly used in field designs—natural behavior, natural setting, and natural treatment—are defined and exemplified. Advantages of combining all 3 dimensions in research include the discovery of new empirical laws and increased internal and external validity. Empirical examples are given that illustrate how naturalistic dimensions can be implemented in many settings, both laboratory and field, often without loss of experimental control. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In Vivo Detection of Gold Nanoshells in Tumors Using Diffuse Optical Spectroscopy

This study demonstrates the use of diffuse optical spectroscopy (DOS) for the noninvasive measurement of gold nanoshell concentrations in tumors of live mice. We measured the diffuse optical spectra (500-800 nm) using an optical fiber probe placed in contact with the tissue surface. We performed in vitro studies on tissue phantoms illustrating an accurate measurement of gold-silica nanoshell concentration within 12.6% of the known concentration. In vivo studies were performed on a mouse xenograft tumor model. DOS spectra were measured at preinjection, immediately postinjection, 1 and 24 h postinjection times, and the nanoshell concentrations were verified using neutron activation analysis.     

Copper selenide nanocrystals for photothermal therapy

Ligand-stabilized copper selenide (Cu(2-x)Se) nanocrystals, approximately 16 nm in diameter, were synthesized by a colloidal hot injection method and coated with amphiphilic polymer. The nanocrystals readily disperse in water and exhibit strong near-infrared (NIR) optical absorption with a high molar extinction coefficient of 7.7 × 10(7) cm(-1) M(-1) at 980 nm. When excited with 800 nm light, the Cu(2-x)Se nanocrystals produce significant photothermal heating with a photothermal transduction efficiency of 22%, comparable to nanorods and nanoshells of gold (Au). In vitro photothermal heating of Cu(2-x)Se nanocrystals in the presence of human colorectal cancer cell (HCT-116) led to cell destruction after 5 min of laser irradiation at 33 W/cm(2), demonstrating the viabilitiy of Cu(2-x)Se nanocrystals for photothermal therapy applications.     

Relative Population of the Levels of the 1s2s2p and 1s2p2 Configurations of Argon from Three Electron Excited Atoms

The possible contributions of the cascading from higher excited states to the states which can deexcite by the x-ray and Auger processes are investigated for Li-like argon. A model is developed to calculate the probability that a given excited state will eventually populate a particular lower excited state. The model requires the calculation of the transition rates of the cascading levels. Numerical results are presented for the cascade feeding of the levels of the ls2s2p and ls2p2 configurations. The cascading levels considered belong to the ls2snl and ls2pnl configurations with nl = 3s,3p,...4f.