Floristic Changes in the Understory Vegetation of Mixed Temperate New England Freshwater Island Forests over a Period of 33 Years.

During a 33-year sampling period, we observed species richness and calculated species evenness and Shannon Diversity for understory woody seedlings and herbaceous species on three small islands in Lake Winnipesaukee, New Hampshire, and noted consistency of dominant plant species over time. Seedlings and herbaceous species were recorded and measured in 25 permanent plots that were created on the three islands in 1978. The understory species data were compiled by frequency and dominance of woody seedlings and herbaceous species. Data from 250 individual quadrats show that species richness more than doubled from 41 in 1978 to 83 species on all three islands in 2011. Species evenness on all the islands remained relatively constant in each of the four samplings. The combined Shannon's Diversity for the three islands rose from 2.76 in 1978 to 3.37 in 2011. Dominant species in the study were Aralia nudicaulis, Gaultheria procumbens, Gaylussacia baccata, Maianthemum canadense, and Tsuga canadensis seedlings.

Enhanced CDC of B cell chronic lymphocytic leukemia cells mediated by rituximab combined with a novel anti-complement factor H antibody.

Rituximab therapy for B cell chronic lymphocytic leukemia (B-CLL) has met with mixed success. Among several factors to which resistance can be attributed is failure to activate complement dependent cytotoxicity (CDC) due to protective complement regulatory proteins, including the soluble regulator complement factor H (CFH). We hypothesized that rituximab killing of non-responsive B-CLL cells could be augmented by a novel human monoclonal antibody against CFH. The B cells from 11 patients with B-CLL were tested ex vivo in CDC assays with combinations of CFH monoclonal antibody, rituximab, and a negative control antibody. CDC of rituximab non-responsive malignant B cells from CLL patients could in some cases be augmented by the CFH monoclonal antibody. Antibody-mediated cytotoxicity of cells was dependent upon functional complement. In one case where B-CLL cells were refractory to CDC by the combination of rituximab plus CFH monoclonal antibody, additionally neutralizing the membrane complement regulatory protein CD59 allowed CDC to occur. Inhibiting CDC regulatory proteins such as CFH holds promise for overcoming resistance to rituximab therapy in B-CLL.

Patient-dependent count-rate adaptive normalization for PET detector efficiency with delayed-window coincidence events.

Quantitative PET imaging is widely used in clinical diagnosis in oncology and neuroimaging. Accurate normalization correction for the efficiency of each line-of- response is essential for accurate quantitative PET image reconstruction. In this paper, we propose a normalization calibration method by using the delayed-window coincidence events from the scanning phantom or patient. The proposed method could dramatically reduce the 'ring' artifacts caused by mismatched system count-rates between the calibration and phantom/patient datasets. Moreover, a modified algorithm for mean detector efficiency estimation is proposed, which could generate crystal efficiency maps with more uniform variance. Both phantom and real patient datasets are used for evaluation. The results show that the proposed method could lead to better uniformity in reconstructed images by removing ring artifacts, and more uniform axial variance profiles, especially around the axial edge slices of the scanner. The proposed method also has the potential benefit to simplify the normalization calibration procedure, since the calibration can be performed using the on-the-fly acquired delayed-window dataset.

Room-temperature sub-band gap optoelectronic response of hyperdoped silicon.

Room-temperature infrared sub-band gap photoresponse in silicon is of interest for telecommunications, imaging and solid-state energy conversion. Attempts to induce infrared response in silicon largely centred on combining the modification of its electronic structure via controlled defect formation (for example, vacancies and dislocations) with waveguide coupling, or integration with foreign materials. Impurity-mediated sub-band gap photoresponse in silicon is an alternative to these methods but it has only been studied at low temperature. Here we demonstrate impurity-mediated room-temperature sub-band gap photoresponse in single-crystal silicon-based planar photodiodes. A rapid and repeatable laser-based hyperdoping method incorporates supersaturated gold dopant concentrations on the order of 10(20) cm(-3) into a single-crystal surface layer ~150 nm thin. We demonstrate room-temperature silicon spectral response extending to wavelengths as long as 2,200 nm, with response increasing monotonically with supersaturated gold dopant concentration. This hyperdoping approach offers a possible path to tunable, broadband infrared imaging using silicon at room temperature.

Selenium segregation in femtosecond-laser hyperdoped silicon revealed by electron tomography.

Doping of silicon with chalcogens (S, Se, Te) by femtosecond laser irradiation to concentrations well above the solubility limit leads to near-unity optical absorptance in the visible and infrared (IR) range and is a promising route toward silicon-based IR optoelectronics. However, open questions remain about the nature of the IR absorptance and in particular about the impact of the dopant distribution and possible role of dopant diffusion. Here we use electron tomography using a high-angle annular dark-field (HAADF) detector in a scanning transmission electron microscope (STEM) to extract information about the three-dimensional distribution of selenium dopants in silicon and correlate these findings with the optical properties of selenium-doped silicon. We quantify the tomography results to extract information about the size distribution and density of selenium precipitates. Our results show correlation between nanoscale distribution of dopants and the observed sub-band gap optical absorptance and demonstrate the feasibility of HAADF-STEM tomography for the investigation of dopant distribution in highly-doped semiconductors.

Curing light burns.

This study sought to reveal the potential heat generated by a light-emitting diode (LED) curing light, which has generally been considered to be relatively cool. It is likely that similarly designed curing lights will produce a similar level of heat and have the potential to cause damage to soft tissue.

Insulator-to-metal transition in selenium-hyperdoped silicon: observation and origin.

Hyperdoping has emerged as a promising method for designing semiconductors with unique optical and electronic properties, although such properties currently lack a clear microscopic explanation. Combining computational and experimental evidence, we probe the origin of sub-band-gap optical absorption and metallicity in Se-hyperdoped Si. We show that sub-band-gap absorption arises from direct defect-to-conduction-band transitions rather than free carrier absorption. Density functional theory predicts the Se-induced insulator-to-metal transition arises from merging of defect and conduction bands, at a concentration in excellent agreement with experiment. Quantum Monte Carlo calculations confirm the critical concentration, demonstrate that correlation is important to describing the transition accurately, and suggest that it is a classic impurity-driven Mott transition.

Insulator-to-metal transition in sulfur-doped silicon.

We observe an insulator-to-metal transition in crystalline silicon doped with sulfur to nonequilibrium concentrations using ion implantation followed by pulsed-laser melting and rapid resolidification. This insulator-to-metal transition is due to a dopant known to produce only deep levels at equilibrium concentrations. Temperature-dependent conductivity and Hall effect measurements for temperatures T>1.7 K both indicate that a transition from insulating to metallic conduction occurs at a sulfur concentration between 1.8 and 4.3×10(20) cm(-3). Conduction in insulating samples is consistent with variable-range hopping with a Coulomb gap. The capacity for deep states to effect metallic conduction by delocalization is the only known route to bulk intermediate band photovoltaics in silicon.

Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst.

Integrating a silicon solar cell with a recently developed cobalt-based water-splitting catalyst (Co-Pi) yields a robust, monolithic, photo-assisted anode for the solar fuels process of water splitting to O(2) at neutral pH. Deposition of the Co-Pi catalyst on the Indium Tin Oxide (ITO)-passivated p-side of a np-Si junction enables the majority of the voltage generated by the solar cell to be utilized for driving the water-splitting reaction. Operation under neutral pH conditions fosters enhanced stability of the anode as compared to operation under alkaline conditions (pH 14) for which long-term stability is much more problematic. This demonstration of a simple, robust construct for photo-assisted water splitting is an important step towards the development of inexpensive direct solar-to-fuel energy conversion technologies.

Emissivity of microstructured silicon.

Infrared transmittance and hemispherical-directional reflectance data from 2.5 to 25 microm on microstructured silicon surfaces have been measured, and spectral emissivity has been calculated for this wavelength range. Hemispherical-total emissivity is calculated for the samples and found to be 0.84 before a measurement-induced annealing and 0.65 after the measurement for the sulfur-doped sample. Secondary samples lack a measurement-induced anneal, and reasons for this discrepancy are presented. Emissivity numbers are plotted and compared with a silicon substrate, and Aeroglaze Z306 black paint. Use of microstructured silicon as a blackbody or microbolometer surface is modeled and presented, respectively.

Retention of gold alloy crowns cemented with traditional and resin cements.

The aim of this study was to measure in vitro retention of cast gold crowns cemented with traditional and resin cements. Forty-eight human molars were prepared on a lathe to produce complete crown preparations with a consistent taper and split into six groups, eight crowns in each group. Crowns were cast in a high-gold alloy and then cemented. After 24 hours, the retention force (N) was recorded and mean values were analyzed by one-way analysis of variance and the Fisher post-hoc least significant difference (PLSD) multiple comparisons test (a = .05). Failure sites were examined under 3100 magnification and recorded. Mean values (SD) for each group in increasing order of retention force were: Harvard Cement: 43 N (27), TempoCem: 59 N (16), PermaCem Dual: 130 N (42), RelyX Luting Cement: 279 N (26), Contax and PermaCem Dual: 286 N (38), and TempoCem with Contax and PermaCem Dual: 340 N (14). The Fisher PLSD interval (P = .05) for comparing cements was 29 N. Zinc-phosphate cement and provisional resin cements had the lowest retention forces. Resin cement with a bonding agent and the hybrid-ionomer cement had similar retention forces. Resin cement with a bonding agent applied after use of a provisional resin cement had a significantly higher retention force than the other cements tested.

Two-year clinical evaluation of a posterior resin composite using a fourth- and fifth-generation bonding agent.

This study evaluated the clinical performance of a posterior resin composite used with a fourth- and fifth-generation bonding agent. Sixty-two Class I and II restorations were placed with half the restorations restored with Gluma Solid Bond (a fourth-generation bonding system, or total etch two-step system) and the other half restored with Gluma Comfort Bond and Desensitizer (a fifth-generation bonding system, or total etch one-step system). Solitaire 2 was used as the restorative material for all restorations. The bonding systems and resin composite were used according to the manufacturer's instructions and all procedures were performed with rubber dam isolation. All restorations were evaluated at baseline, six months and one and two years. A modified USPHS scale was used to evaluate the restorations for marginal discoloration, recurrent caries, anatomic form, marginal adaptation and proximal contact. Statistical analysis revealed that at two years no significant differences were found between the two bonding agents. Overall, Solitaire 2 performed well clinically whether Gluma Solid Bond or Gluma Comfort Bond and Desensitizer was used. It was thus concluded that Solitaire 2 functions successfully when used as a posterior restorative material for at least two years.

All-optical switching in a nematic liquid crystal twist cell.

Continuous wave photorefractive-like all-optical switching was demonstrated using a twisted nematic liquid crystal cell composed of the liquid crystal 5CB (4-pentyl-4'-cyanobiphenyl) with polyvinyl alcohol (PVA) aligning layers. The nonlinear optical effect involved is due to optical control of surface charge on the polyvinyl alcohol alignment layer. The cell exhibits strong optical control of the Friedericksz transition by an argon ion laser. A mechanism is proposed involving the modulation of the charge double layer by photoinduced charge. Optical limiting in the milliwatt range was observed.

How storage and mixing affect a resin-modified glass ionomer.

This study investigates how the storage time and mixing speed of an older (20+ years old), common brand triturator affect the working time of a resin-modified glass ionomer restorative material. To achieve consistent working times, the correct mixing speed should be used, especially for material near its expiration date.