Level degeneracy and temperature-dependent carrier distributions in self-organized quantum dots

Using femtosecond three-pulse pump–probe spectroscopy, we investigated the transparency condition for the ground and first excited states in self-organized In0.4Ga0.6AsIn0.4Ga0.6As quantum dots at different temperatures and wavelengths. The temperature-dependent behavior of the transparency condition is consistent with calculations using a multilevel model with a large density of states in the quantum-well reservoir. The twofold spatial degeneracy of the first excited state and the temperature dependence of the thermal equilibrium processes were experimentally observed. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71141/2/APPLAB-82-12-1959-1.pd

Blood pressure management in ischemic stroke patients undergoing mechanical thrombectomy

The relationship between presenting blood pressure in acute ischemic stroke patients and outcome is complex. Several studies have demonstrated a U-shaped curve with worse outcomes when blood pressure is high or low. The American Heart Association/American Stroke Association guidelines recommend values of blood pressure \u3c 185/110 mmHg in patients treated with intravenous t-PA and permissive hypertension up to 220/120 mmHg in those not treated with intravenous t-PA. The optimal blood pressure target is less clear in patients undergoing mechanical thrombectomy. Before thrombectomy, the guidelines recommend a blood pressure \u3c 185/110 mmHg though patients with even lower systolic blood pressures may have better outcomes. During and after thrombectomy, the guidelines recommend a blood pressure \u3c 180/105 mmHg. However, several studies have suggested that during thrombectomy the primary goal should be to prevent significant low blood pressure (e.g., target systolic blood pressure \u3e 140 mmHg or MAP \u3e 70 mmHg). After thrombectomy, the primary goal should be to prevent high blood pressure (e.g., target systolic blood pressure \u3c 160 mmHg or MAP \u3c 90 mmHg). To make more specific recommendations, large, randomized-control studies are needed that address factors such as the baseline blood pressure, timing and degree of revascularization, status of collaterals, and estimated risk of reperfusion injury

Gain dynamics and ultrafast spectral hole burning in In(Ga)As self-organized quantum dots

Using a femtosecond three-pulse pump-probe technique, we investigated spectral hole-burning and gain recovery dynamics in self-organized In(Ga)As quantum dots. The spectral hole dynamics are qualitatively different from those observed in quantum wells, and allow us to distinguish unambiguously the gain recovery due to intradot relaxation and that due to carrier capture. The gain recovery due to carrier–carrier scattering-dominated intradot relaxation is very fast ( ∼ 130 fs),(∼130fs), indicating that this is not the factor limiting the bandwidth of directly modulated quantum dot lasers. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70041/2/APPLAB-81-4-670-1.pd

Temperature-dependent carrier dynamics in self-assembled InGaAs quantum dots

We measured the transient temperature-dependent carrier population in the confined states of self-assembled In0.4Ga0.6AsIn0.4Ga0.6As quantum dots as well as those of the surrounding wetting layer and barrier region using differential transmission spectroscopy. Results show directly that thermal reemission and nonradiative recombination contribute significantly to the dynamics above 100 K. We offer results of an ensemble Monte Carlo simulation to explain the contribution of these thermally activated processes. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71088/2/APPLAB-80-12-2162-1.pd

A photoconductive, miniature terahertz source

We discuss the performance of a micromachined, photoconductive terahertz emitter that is fabricated on low-temperature-grown GaAs. The device is mounted on a pair of single-mode optical fibers that allows the source to be freely positionable. A strong radiation burst is emitted due to the large magnetic moment created by the electrode. The emitter’s small feature size of 300 μm by 300 μm with a photoconductive switch area of 30 μm by 30 μm suggests its application for terahertz, time-domain, near-field spectroscopy and imaging. © 1998 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70594/2/APPLAB-72-24-3100-1.pd

Application of a new screening model to thermonuclear reactions of the rp process

A new screening model for astrophysical thermonuclear reactions was derived recently which improved Salpeter's weak-screening one. In the present work we prove that the new model can also give very reliable screening enhancement factors (SEFs) when applied to the rp process. According to the results of the new model, which agree well with Mitler's SEFs, the screened rp reaction rates can be, at most, twice as fast as the unscreened ones.Comment: 8 RevTex pages + 7 ps figures. (Revised version). Accepted for publication in Journal of Physics

Bioaktivitas Metabolit Sekunder dari Genus Dipterocarpus

Research has been conducted with the title "Literature Study of Secondary Metabolites and Bioactivity of Plants Genus Dipterocarpus". The method used is a descriptive method with the aim of being to find out the active compounds in the genus plant dipterocarpus and to know the ability of the bioactivity of genus plants dipterocarpus. Based on the results of the study, bioactivity of secondary metabolites from planst of the genus dipterocarpus namely antidiabetic, antiplasmodial, antibacterial, antioxidant, anticlasses, cytotoxic, anticholinesterase, antiproliferation, anti-inflammatory and antimicrobial. Very strong biosaltivity indicated by the ethyl acetate faction plant D. Intricatus Sagai Antioxidant IC50 Nialial is 0.075 μg / mL. While very weak bioacchables are shown extract methanol stem plant D. Costatus as cytotoxic with ic50 value 973 ± 14.57 μg / mL

Evaluation of a Low-Cost, PC-Based Driving Simulator to Assess Persons with Cognitive Impairments Due to Brain Injury

Brain injury due to accident or stroke frequently results in cognitive impairment, reducing an individual’s ability to judge driving situations accurately. Rehabilitation professionals typically use a combination of clinical and on-road tests to determine whether an individual is safe to drive. Weighing the safety of the community, the candidate, and the driving evaluator, these on-road tests are often conducted under road, traffic and weather conditions less demanding than those that a driver might face in the “real world,” and thus may offer less than complete information regarding the candidate’s responses to such real-world driving challenges. Indeed, individuals with mild cognitive deficits may perform adequately under such testing conditions but unsafely when driving challenges increase. Complicating this situation further, those with mild to moderate acquired cognitive impairments may be largely unaware of their own limitations, and thus more intolerant of perceived delays or challenges to their desire to drive again. Although continuing advances have improved performance and fidelity while significantly reducing costs, most interactive driving simulators remain too expensive for widespread clinical application. In a project funded by the National Center for Medical Rehabilitation Research, National Institutes of Health, we sought to determine, on a pilot basis, whether a low-cost, PC-based driving simulator could provide clinicians with information useful to their efforts to assess the safe ability to drive of individuals with cognitive impairments. We developed two comprehensive simulator-based driving scenarios, one quite basic and one more challenging, and pilot-tested them on ten subjects – five with moderate cognitive impairments, and five age and sex matched-controls without impairment. The “simple” scenario was developed to match the essential demands of the first half of an existing on-road driving evaluation; the “complex” scenario was based on the second half of the on-road evaluation into which more demanding, but still common, driving challenges were integrated. Road types, lane widths, pavement markings, traffic signals, horizontal and vertical curvature, and the proximal built environment were all created in simulation to provide a convincing generic representation of the on-road test. Challenges incorporated into the “complex” phase of the scenario, which were absent from the “simple” phase, included traffic events such as: cross-traffic failing to stop at a STOP sign; pedestrians crossing the driver’s path; vehicles suddenly pulling out in front of the subject from the road shoulder; opposing thru traffic appearing suddenly from behind slower moving vehicles as the subject attempted to turn left; slower moving lead vehicles causing passing decisions; traffic streams forcing gap acceptance decisions; etc. Results from the simulator were compared to results from the on-road evaluation. In addition, data gathered from subject exit interviews was used to judge simulator verisimilitude and efficacy in changing self-awareness of deficit. Because the cognitive impairments associated with brain injury often reduce the individual’s awareness of his or her own limitations, we looked at evidence that performance on the simulator could contribute to an individual’s own understanding of his or her driving strengths and weaknesses. The results of the pilot study will lead to an enhancement of simulator capabilities, and to a comprehensive clinical trial at multiple sites. This paper will present the findings of this pilot investigation and an overview of the expanded clinical study

A fiber‐mounted, micromachined photoconductive probe with 15 nV/Hz1/2 sensitivity

We report the performance of a micromachined, photoconductive‐sampling probe that is fabricated on low‐temperature‐grown GaAs and mounted on a single‐mode optical fiber. The epitaxial probe has a temporal resolution of 3.5 ps, a spatial resolution of 7 μm, and a sensitivity of 15 nV/(Hz)1/2 when integrated with a high impedance, junction field‐effect transistor source follower. The fiber, which couples short laser pulses to the interdigitated detector pattern on the probe, also provides flexible support and mobility. The probe’s compact cross section makes it ideal for applications as an internal‐node, picosecond‐response, photoconductive sampling probe or wave form launcher for test and characterization of integrated circuits. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70779/2/APPLAB-69-13-1843-1.pd