Control of Black Root Rot in Dark Tobacco

Reports of the increasing prevalence of black root rot in the areas where dark tobacco types are grown has triggered an accelerated effort from the tobacco research staff to develop and release additional varieties with high resistance to this disease. The high level of resistance to black root rot found in Nicotiana debneyi (an Australian species) is being used as the source of resistance in the breeding program

Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests

Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 ◦C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island ofHawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 ◦C increase in MAT. Our estimate of the Q10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5–2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming

Neutral-Donor-Bound-Exciton Complexes in ZnO Crystals

Neutral-donor–bound-exciton transitions have been observed in ZnO. The isolated neutral donors are made up of defect pair complexes. The neutral-donor nature of these pair complexes was determined from magneticfield measurements and from two-electron transitions. Excited states of the neutral-donor bound excitons were observed in the form of rotator states analogous to rotational states of the H2 molecule

Excitonic photoluminescence linewidths in AlGaAs grown by molecular beam epitaxy

The linewidths of excitonic transitions were measured in AlxGa1−xAs, grown by molecular beam epitaxy as a function of alloy composition x for values of x≲0.43 using high resolution photoluminescence spectroscopy at liquid helium temperature. The values of the linewidths thus measured are compared with the results of several theoretical calculations in which the dominant broadening mechanism is assumed to be the statistical potential fluctuations caused by the components of the alloy. An increase in the linewidth as a function of x is observed which is in essential agreement with the prediction of the various theoretical calculations. The linewidths of the excitonic transitions in AlxGa1−xAs observed in the present work are the narrowest ever reported in the literature, for example σ=2.1 meV for x=0.36, thus indicating very high quality material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70175/2/APPLAB-48-11-727-1.pd

Inflatable Re-entry Vehicle Experiment (IRVE-4) Overview

The suite of Inflatable Re-Entry Vehicle Experiments (IRVE) is designed to further our knowledge and understanding of Hypersonic Inflatable Aerodynamic Decelerators (HIADs). Before infusion into a future mission, three challenges need to be addressed: surviving the heat pulse during re-entry, demonstrating system performance at relevant scales, and demonstrating controllability in the atmosphere. IRVE-4 will contribute to a better understanding of controllability by characterizing how a HIAD responds to a set of controlled inputs. The ability to control a HIAD is vital for missions that are g-limited, require precision targeting and guidance for aerocapture or entry, descent, and landing. The IRVE-4 flight test will focus on taking a first look into controlling a HIAD. This paper will give an overview of the IRVE-4 mission including the control response portion of the flight test sequence, and will provide a review of the mission s development

Effect of C∕Si ratio on deep levels in epitaxial 4H–SiC

Changing the ratio of carbon to silicon during the epitaxial 4H–SiC growth is expected to alter the dominant deep level trap, which has been attributed to a native defect. The C∕Si ratio was changed from one to six during epitaxialgrowth of SiC. Diodes fabricated on the epitaxial layer were then characterized using current-voltage and deep level transient spectroscopy. The single peak at 340K (Z1/Z2 peak), was deconvolved into two traps, closely spaced in energy. The concentration of one of the Z1/Z2 traps decreased with increasing C∕Si ratio. This result opposes theoretical predictions of carboninterstitial components, and supports assignment to a silicon antisite or carbonvacancy relationship. The concentration of the second component of the peak at 340K did not depend on the C∕Si ratio, which would indicate an impurity in an interstitial site

Prophylactic Intra-Aortic Balloon Counterpulsation in High Risk Cardiac Surgery: The PINBALL Pilot Multicentre, Registry-Linked, Randomised, Controlled Feasibility Trial

Background: Prophylactic intra-aortic balloon counterpulsation (IABC) is commonly used in selected patients undergoing coronary artery bypass graft (CABG) surgery, but definitive evidence is lacking. The aim of the multicentre PINBALL Pilot randomised controlled trial (RCT) was to assess the feasibility of performing a definitive trial to address this question. Methods: Patients listed for CABG surgery with impaired left ventricular function and at least one additional risk factor for postoperative low cardiac output syndrome were eligible for inclusion if the treating surgical team was uncertain as to the benefit of prophylactic IABC. The primary outcome of feasibility was based on exceeding a pre-specified recruitment rate, protocol compliance and follow-up. Results: The recruitment rate of 0.5 participants per site per month did not meet the feasibility threshold of two participants per site per month and the study was stopped early after enrolment of 24 out of the planned sample size of 40 participants. For 20/24 (83%) participants, preoperative IABC use occurred according to study assignment. Six (6)-month follow-up was available for all enrolled participants, [IABC 1 death (8%) vs. control 1 death (9%), p = 0.95]. Conclusion: The PINBALL Pilot recruitment rate was insufficient to demonstrate feasibility of a multicentre RCT of prophylactic IABC in high risk patients undergoing CABG surgery