Search

OBJECTIVE To examine the role of intensive care unit (ICU) management following lateral skull base surgery for vestibular schwannoma and identify risk factors for complications warranting admission to the ICU. STUDY DESIGN Retrospective review. SETTING Tertiary referral center. PATIENTS Two hundred consecutive patients undergoing lateral skull base surgery for vestibular schwannomas. INTERVENTION Lateral skull base approach for resection of vestibular schwannoma and postoperative monitoring. MAIN OUTCOME MEASURES Patients were grouped if they sustained an ICU complication, a non-ICU complication, or no complication. Analysis was performed to determine patient or treatment factors that may be associated with ICU complications. Multivariate and three-way analysis of variance compared groups, and multivariate logistic regression determined adjusted odds ratios (aOR) for analyzed factors. RESULTS Seventeen of 200 patients sustained ICU complications (8.5%), most commonly hypertensive urgency (n = 15). Forty-six (23%) sustained non-ICU complications, and 137 (68.5%) had no complications. When controlling for age, sex, obesity, and other comorbidities, only hypertension (aOR 5.43, 95% confidence interval (CI) 1.35-21.73, p = 0.017) and tumor volume (aOR 3.29, 95% CI 1.09-9.96, p = 0.035) were independently associated with increased risk of ICU complications. CONCLUSIONS The necessity of intensive care following lateral skull base surgery is rare, with the primary ICU complication being hypertensive urgency. Preoperative hypertension and large tumor volume (>4500 mm3) were independently associated with increased risk for ICU complications. These findings may allow for risk stratification of patients appropriate for admission to stepdown units following resection of vestibular schwannomas. Further prospective, multi-center, randomized studies are necessary to validate these findings before systematic changes to current postoperative care practices.

After deep venous thrombosis (DVT), many patients have impaired quality of life (QOL). We aimed to assess whether pharmacomechanical catheter-directed thrombolysis (PCDT) improves short-term or long-term QOL in patients with proximal DVT and whether QOL is related to extent of DVT.The Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) trial was an assessor-blinded randomized trial that compared PCDT with no PCDT in patients with DVT of the femoral, common femoral, or iliac veins. QOL was assessed at baseline and 1 month, 6 months, 12 months, 18 months, and 24 months using the Venous Insufficiency Epidemiological and Economic Study on Quality of Life/Symptoms (VEINES-QOL/Sym) disease-specific QOL measure and the 36-Item Short Form Health Survey (SF-36) physical component summary (PCS) and mental component summary general QOL measures. Change in QOL scores from baseline to assessment time were compared in the PCDT and no PCDT treatment groups overall and in the iliofemoral DVT and femoral-popliteal DVT subgroups.Of 692 ATTRACT patients, 691 were analyzed (mean age, 53 years; 62% male; 57% iliofemoral DVT). VEINES-QOL change scores were greater (ie, better) in PCDT vs no PCDT from baseline to 1 month (difference, 5.7; P = .0006) and from baseline to 6 months (5.1; P = .0029) but not for other intervals. SF-36 PCS change scores were greater in PCDT vs no PCDT from baseline to 1 month (difference, 2.4; P = .01) but not for other intervals. Among iliofemoral DVT patients, VEINES-QOL change scores from baseline to all assessments were greater in the PCDT vs no PCDT group; this was statistically significant in the intention-to-treat analysis at 1 month (difference, 10.0; P .0001) and 6 months (8.8; P .0001) and in the per-protocol analysis at 18 months (difference, 5.8; P = .0086) and 24 months (difference, 6.6; P = .0067). SF-36 PCS change scores were greater in PCDT vs no PCDT from baseline to 1 month (difference, 3.2; P = .0010) but not for other intervals. In contrast, in femoral-popliteal DVT patients, change scores from baseline to all assessments were similar in the PCDT and no PCDT groups.Among patients with proximal DVT, PCDT leads to greater improvement in disease-specific QOL than no PCDT at 1 month and 6 months but not later. In patients with iliofemoral DVT, PCDT led to greater improvement in disease-specific QOL during 24 months.

The occurrence of terrestrial palynomorphs in Quaternary marine sedimentary sequences allows for direct land–sea correlations and provides a means for transferring Marine Isotope Stage chronologies to terrestrial records that extend beyond the range of radiocarbon dating. Both of these important applications require an implicit assumption that the lag between pollen release and final deposition on the seafloor – here referred to as source-to-sink residence time – is negligible in relation to the chronological resolution of the sedimentary sequence. Most studies implicitly assume zero lag, and where studies do take palynomorph residence time into account, its magnitude is rarely quantified. In Westland, New Zealand, fluvial transport is the main source of delivery of terrestrial pollen offshore to the adjacent East Tasman Sea. We radiocarbon-dated organic matter carried and deposited by contemporary Westland rivers that drain catchments with varying degrees of disturbance. The ages obtained ranged widely from essentially modern (i.e., − 57 ± 22 cal yr BP) to 3583 ± 188 cal yr BP, suggesting that precisely constraining the residence time in this region is unlikely to be achieved. We also compared the timing of four palynomorph events characterising Westland's late Pleistocene, along with the well-dated Kawakawa/Oruanui Tephra (KOT), between marine core MD06-2991 and four terrestrial records from Westland. Critically, all palynomorph events and the KOT are chronologically indistinguishable with respect to the independently dated marine and terrestrial records, supporting the general principle of transferring the marine chronology onto the terrestrial records in this setting. In other regions, particularly those lacking the high soil production and erosion rates that characterise Westland, we suggest that similar tests of marine residence time should be conducted before assumptions of zero or negligible lag are invoked.

In this paper we report the generation of flat top optical spectrum using an arbitrary waveform generator to increase the SBS threshold in high power optical fiber amplifiers. The optical spectrum consists of a number of discrete spectral lines, ranging from 16 to 380, within the bandwidth of 2GHz, corresponding to line spacing between 133 MHz and 5 MHz. These discrete spectral lines correspond to a PRBS pattern of n = 4 to n = 8. The SBS threshold and coherence properties of the flat top spectrum are measured and compared to that of the filtered PRBS in a kilowatt class fiber amplifier. It is experimentally demonstrated that for large frequency line spacing, the flat top spectrum significantly outperforms the corresponding filtered PRBS, but as the line spacing is decreased to less than the Brillouin bandwidth, the two modulation waveforms have similar enhancement factors in the SBS threshold due to the enhanced crosstalk between neighboring frequency components.

This study examined the energy transfer ratio (ETR) of Central Mine Equipment (CME) automatic standard penetration test (SPT) hammers utilizing a large database of SPT energy measurements. The database consisted of energy measurements from 17,825 SPT hammer blows obtained from 33 CME automatic hammers over a 5-year period, many of which were tested multiple times. The average ETR for all 17,825 CME automatic hammer blows in the database was 82.9% with a COV of ±7.4%. The database also provided an opportunity to determine the impacts of hammer calibration, test depth, and calibration interval on the measured ETR. The impact on average ETR of eliminating hammer blows due to D4633-10 restrictions was also demonstrated.

Polychromatic laser light can reduce speckle contrast in wavefront-sensing and imaging applications that use direct detection schemes. To help quantify the associated reduction in speckle contrast, this study investigates the accuracy and numerical efficiency of three separate wave-optics models that simulate the active illumination of extended objects with polychromatic laser light. The three separate models use spectral slicing, Monte Carlo averaging, and depth slicing, respectively, to simulate the laser-target interaction. The sampling requirements of all three models are discussed. Comparisons to analytical solutions and experimental data are made when possible. In general, the experiments and theory compare favorably with the models.

The design of Q-switched lasers capable of producing pulse widths of 100’s of picoseconds necessitates the cavity length be shorter than a few centimeters. Increasing the amount of energy extracted per pulse requires increasing the mode area of the resonator that for the same cavity length causes exciting higher order transverse modes and decreasing the brightness of the output radiation. To suppress the higher order modes of these multimode resonators while maintaining the compact cavity requires the use of intra-cavity angular filters. A novel Q-switched laser design is presented using transmitting Bragg gratings (TBGs) as angular filters to suppress the higher order transverse modes. The laser consists of a 5 mm thick slab of Nd:YAG, a 3 mm thick slab of Cr:YAG with a 20% transmission, one TBG aligned to suppress the higher order modes along the x-axis, and a 40% output coupler. The gratings are recorded in photo-thermo-refractive (PTR) glass, which has a high damage threshold that can withstand both the high peak powers and high average powers present within the resonator. Using a 4.1 mrad TBG in a 10.8 mm long resonator with an 800μm x 400 μm pump beam, a nearly diffraction limited beam quality of M2 = 1.3 is obtained in a 0.76 mJ pulse with a pulse width of 614 ps.

We report efficient coherent beam combining of five kilowatt-class fiber amplifiers with a diffractive optical element (DOE). Based on a master oscillator power amplifier (MOPA) configuration, the amplifiers were seeded with pseudo random phase modulated light. Each non-polarization maintaining fiber amplifier was optically path length matched and provides approximately 1.2 kW of near diffraction-limited output power (measured M2

We report results from two ~1.5 kW Yb-doped fiber amplifiers with comparable optical to optical efficiencies and linewidths. One amplifier utilized a fiber with a core diameter of 25 μm while the core diameter of the fiber utilized in the other amplifier was 20 μm. Stimulated Brillouin scattering (SBS) suppression in both cases was achieved through pseudo-random bit sequence (PRBS) phase modulation. While the power generated in the larger core fiber was modal instability (MI) limited, no sign of MI was observed in the smaller core fiber. This may allow us to utilize the higher MI threshold fiber to scale further while maintaining sufficiently narrow linewidth for beam combining. Furthermore, in a demonstration of the utility of applying a thermal gradient in conjunction with phase modulation to suppress SBS further, we report on a 1 kW amplifier driven at a PRBS clock rate of 2 GHz. Finally, we compare the coherent beam combining properties of amplifiers seeded with PRBS phase modulated sources to those seeded with white noise sources.

Background Chronic pain is common and challenging to treat. Although cognitive behavioral therapy (CBT) is efficacious, its benefit in disadvantaged populations is largely unknown. Objective To evaluate the efficacy of literacy-adapted and simplified group CBT versus group pain education (EDU) versus usual care. Design Randomized controlled trial. (ClinicalTrials.gov: NCT01967342). Setting Community health centers serving low-income patients in Alabama. Patients Adults (aged 19 to 71 years) with mixed chronic pain. Interventions CBT and EDU delivered in 10 weekly 90-minute group sessions. Measurements Self-reported, postintervention pain intensity (primary outcome) and physical function and depression (secondary outcomes). Results 290 participants were enrolled (70.7% of whom were women, 66.9% minority group members, 72.4% at or below the poverty level, and 35.8% reading below the fifth grade level); 241 (83.1%) participated in posttreatment assessments. Linear mixed models included all randomly assigned participants. Members of the CBT and EDU groups had larger decreases in pain intensity scores between baseline and posttreatment than participants receiving usual care (estimated differences in change scores-CBT: -0.80 [95% CI -1.48 to -0.11]; P = 0.022; EDU: -0.57 [CI, -1.04 to -0.10]; P = 0.018). At 6-month follow-up, treatment gains were not maintained in the CBT group but were still present in the EDU group. With regard to physical function, participants in the CBT and EDU interventions had greater posttreatment improvement than those receiving usual care, and this progress was maintained at 6-month follow-up. Changes in depression (secondary outcome) did not differ between either the CBT or EDU group and the usual care group. Limitations Participants represented a single health care system. Self-selection bias may have been present. Conclusion Simplified group CBT and EDU interventions delivered at low-income clinics significantly improved pain and physical function compared with usual care. Primary funding source Patient-Centered Outcomes Research Institute.

Optical linewidth broadening through both white noise (WNS) and pseudo-random binary sequence (PBRS) phase modulation are effective techniques for suppressing stimulated Brillouin scattering (SBS) in high- power fiber amplifiers. However, detailed studies comparing both coherent beam combining and SBS suppression of these phase modulation schemes have not been reported. In this study, a passive fiber cutback experiment is performed comparing the SBS threshold enhancement factor of a PRBS and WNS broadened seed as a function of linewidth and fiber length. Particularly, assuming an optimal PRBS pattern is chosen, pseudo-random modulation provides superior SBS suppression than WNS for a given fiber length and signal linewidth. Furthermore, two WNS and PRBS modulated 150 W fiber lasers are coherently combined to measure and compare the combining efficiency, beam quality, and coherence as a function of optical path length difference. Notably, the discrete spectral density of PRBS modulation provides a re-coherence effect where the lasers periodically come back into phase. Overall, this may reduce path length matching complexity in coherently combined fiber laser systems.

Power scaling using a higher order mode in a ribbon fiber has previously been proposed. However, methods of selecting the higher order mode and converting to a single lobe high brightness beam are needed. We propose using a multiplexed transmitting Bragg grating (MTBG) to convert a higher order mode into a single lobe beam. Using a ribbon fiber with core dimensions of 107.8 μm by 8.3 μm, we use the MTBG to select a higher order mode oscillating within the resonator with 51.4% efficiency, while simultaneously converting the higher order mode to a beam with diffraction limited divergence of 10.2 mrad containing 60% of the total power.

Selection of the fundamental mode of an active large mode area “ribbon” fiber laser with core dimensions of 107.8 μm by 8.3 μm was produced by a transmitting Bragg grating (TBG) in a free-space resonator. The multimode performance of the original laser was characterized to have an M2 of 11.3 with an absorbed power slope efficiency of 76%. With the TBG aligned to provide maximum diffraction efficiency for the fundamental mode, the M2 improved to 1.45 at an absorbed power slope efficiency of 54% and enhanced the brightness by 5.1 times.

Power scaling of high power laser resonators is limited due to several nonlinear effects. Scaling to larger mode areas can offset these effects at the cost of decreased beam quality, limiting the brightness that can be achieved from the multi-mode system. In order to improve the brightness from such multi-mode systems, we present a method of transverse mode selection utilizing volume Bragg gratings (VBGs) as an angular filter, allowing for high beam quality from large mode area laser resonators. An overview of transverse mode selection using VBGs is given, with theoretical models showing the effect of the angular selectivity of transmitting VBGs on the resonator modes. Applications of this ideology to the design of laser resonators, with cavity designs and experimental results presented for three types of multimode solid state lasers: a Nd:YVO4 laser with 1 cm cavity length and 0.8 mm diameter beam with an M 2 of 1.1, a multimode diode with diffraction limited far field divergence in the slow axis, and a ribbon fiber laser with 13 cores showing M 2 improved from 11.3 to 1.5.

We propose to use transmitting volume Bragg gratings recorded in photo-thermo-refractive glass as high efficient intracavity angular filters in order to achieve high beam quality while using large aperture active medium. The paper describes implementation of novel compact cavity design for solid state lasers, laser diodes, fiber crystal lasers and others. Keywords—Holographic volume grating, laser cavity Scaling of the pumping size in gain medium is an efficient way to increase output power, improve heat exchange and suppress nonlinear effects in different types of laser systems. Obviously, the cost of such scaling is degradation of the laser beam quality. Complex, bulk cavities or other special techniques are required in order to obtain lasing with beam quality close to diffraction limit. We propose to use transmitting volume Bragg gratings (VBGs) recorded in photothermo-refractive glass (PTR-glass) as high efficient intracavity angular filters in order to achieve high beam quality while using large aperture active medium. In comparison with standard methods of mode selection based on spatial (aperture) mode filtration, VBGs provide highly efficient mode selection in the angular space. Therefore, a very compact and simple laser cavity with extended pumping area could be created based upon such PTR glass holographic elements. The paper describes implementation of this novel laser cavity design for solid state lasers, laser diodes, fiber crystal lasers and others. While the first VBGs were recorded in PTR-glass long time ago [1], the real attention to these optical components began only when the technology allowed the fabrication of low loss and high efficiency PTR VBGs [2]. These new diffractive optical elements had high tolerance to laser radiation of up to multi kilowatt levels and triggered hundreds of publications in the area of laser applications. Today reflecting VBGs are used significantly more in laser systems in comparison with other elements from the same family. The most well-known application of such volume gratings is the narrowing and wavelength stabilization of the emission of laser diode sources [3] that are used for pumping of solid-state or fiber lasers. In comparison with reflecting gratings, transmitting VBGs have substantially narrower angular selectivity and wider spectral selectivity. Transmitting VBGs with angular selectivity of less than 50 μrad were demonstrated experimentally and this number is not the limit for our PTR glass technology. Nevertheless, up to now such a unique grating property did not find wide application in laser systems. We demonstrate experimentally the possibility to use a transmitting VBG for transverse mode selection in different types of lasers with extended pumping region. First, we designed and made a solid state laser based on Nd-doped vanadate crystal and were able to shrink the cavity length by 30 times. The implemented plain cavity had a 10 mm length. The diameter of the pumped area varied from 0.8 to 2 mm (15-94 Fresnel numbers). Without mode selection the measured M 2 exceeded 5 for pumped area with diameter of 0.8 mm. Modeling showed that the cavity losses for TEM01 mode are 2.5 times higher than the losses for TEM00 mode for wide range of transmitting VBGs with different angular selectivity. The insertion of VGB filters in the laser cavity enabled stable lasing with M 2 =1.05-1.3 for 0.8-2.0 mm pumping diameters. The slope efficiency was more than 30% for optimal parameters of the VBG filter. This number is very close to the slope efficiency of a stable semispherical cavity with 30 cm length which was used as reference. Another type of an explored laser was an external cavity strongly multi-mode broad area laser diode with 100 μm stripe. In this case, a compact (~ 3 mm) external cavity was created by off-axis scheme with a transmitting VBG as a transverse mode filter and a reflecting VBG as an output coupler. We obtained lasing with divergence close to the diffraction limit and with efficiency just 15% less than that of a free running LD. High quality emission was obtained for pumping currents which did not exceed 6-7 times the threshold. At higher currents the beam quality degraded quickly due to influences of parasitic reflections from the AR-coated mirror of the internal laser diode cavity. We could substantially expand the mentioned current interval by using the same off-axis scheme with a VBG filter for a 100 μm stripe surface emitting diode laser with a detuned grating output coupler. Additionally, VBG spatial mode selection technique was applied successfully for external cavity fiber crystal lasers and organic VECSEL. Obtained results will be discussed. [1] V.A. Borgman, L.B. Glebov, N.V. Nikonorov, G.T. Petrovskii, V.V. Savvin, A.D. Tsvetkov. Photothermal refractive effect in silicate glasses. Sov. Phys. Dokl., 34 (1989) 1011-1013. [2] L. Glebov "Photosensitive holographic glass – new approach to creation of high power lasers" Eur. J. Glass Sci. Technol. B, 48, 123–128, 2007 [3] G. Venus, A. Sevian, V. Smirnov, L. Glebov “High-brightness narrowline laser diode source with volume Bragg-grating feedback.” Proc. of SPIE Vol. 5711 (2005) , 166-176

Background: As many as 70% of veterans with chronic pain treated within the US Veterans Administration (VA) system may have posttraumatic stress disorder (PTSD), and conversely, up to 80% of those with PTSD may have pain. We describe pain experienced by US service members and veterans with symptoms of PTSD, and report on the effect of Accelerated Resolution Therapy (ART), a new, brief exposure-based therapy, on acute pain reduction secondary to treatment of symptoms of PTSD. Methods: A randomized controlled trial of ART versus an attention control (AC) regimen was conducted among 45 US service members/veterans with symptoms of combat-related PTSD. Participants received a mean of 3.7 sessions of ART. Results: Mean age was 41.0 � 12.4 years and 20% were female. Most veterans (93%) reported pain. The majority (78%) used descriptive terms indicative of neuropathic pain, with 29% reporting symptoms of a concussion or feeling dazed. Mean pre-/post-change on the Pain Outcomes Questionnaire (POQ) was � 16.9916.6 in the ART group versus � 0.7914.2 in the AC group (p � 0.0006). Among POQ subscales, treatment effects with ART were reported for pain intensity (effect size � 1.81, p � 0.006), pain-related impairment in mobility (effect size � 0.69, p � 0.01), and negative affect (effect size � 1.01, p � 0.001). Conclusions: Veterans with symptoms of combat-related PTSD have a high prevalence of significant pain, including neuropathic pain. Brief treatment of symptoms of combat-related PTSD among veterans by use of ART appears to acutely reduce concomitant pain.

Volume Bragg gratings (VBG) recorded in photo-thermo refractive glass (PTR) have high stability, and high damage threshold, allowing for many applications to the design of high power lasers. Gratings recorded in the transmitting geometry (TBG) have narrow angular selectivity, and can be used as a spatial filter in a resonator. Such gratings have previously been useful for improving the brightness of high power diodes, and increasing the beam quality in rod geometry solid state lasers. As the gratings have narrow angular selectivity, losses for higher order modes in the resonator no longer depend on the cavity length, allowing for the construction of short cavities with large mode areas. In this paper, we explore the design of short 1cm cavities using two TBGs as a spatial filter and no aperture in the cavity. The M 2 parameter as a function of pump size and angular selectivity of the TBG are explored, using pump diameters ranging from 800um to 2mm and angular selectivity ranging from 11mrad to 1.8mrad. An M 2 parameter of 1.05 is reported for an 800μm pump diameter, a 6.2mrad TBG, and a 1cm long cavity.

In order to generate high power laser radiation it is often necessary to combine multiple lasers into a single beam. The recent advances in high power spectral beam combining using multiplexed volume Bragg gratings recorded in photo-thermo-refractive glass are presented. The focus is on using multiple gratings recorded within the same volume to lower the complexity of the combining system. Combining of 420 W with 96% efficiency using a monolithic, multiplexed double grating recorded in PTR glass is demonstrated. A multiplexed quadruple grating that maintains high efficiency and good beam quality is demonstrated to pave a way for further scaling of combining channels.

The earliest or patch stage of mycosis fungoides may present diagnostic difficulty both clinically and pathologically. The present study of the polymerase chain reaction (PCR) as a diagnostic tool in early mycosis fungoides was therefore undertaken, using a rapid PCR method for the detection of gamma- and beta-chain T-cell receptor (TCR) gene rearrangements in routine formalin-fixed, paraffin-embedded histological sections. Forty-two biopsies were studied from 26 patients with mycosis fungoides. Twenty-three skin biopsies with a clinicopathological diagnosis of early, or patch stage, mycosis fungoides were investigated. Of these, 18 (78 per cent) showed TCR-gamma or both beta- and gamma-chain TCR gene rearrangements. TCR gene rearrangements were shown in seven of the 14 plaque stage lesions (50 per cent) and also in the single case of tumour stage disease. Where gene rearrangements were identified, these were identical in all biopsies from an individual patient, irrespective of the site of the lesion, the disease stage, or the time lapse between the biopsies. The PCR is therefore a highly sensitive technique, which can be performed on routine pathological material, in cases where the diagnosis of early mycosis fungoides cannot be made with certainty on conventional histopathological and immunohistochemical grounds.

Volume Bragg gratings have been successfully used in spectr al beam combining of high po wer fiber lasers with narrow channel separationand in four channel passive coherent beam combining of fiber lasers. Future application of beam combining with kilowatt level lasers requires a more detailed understanding of how to cool the gratings without hurting beam quality. Forced air cooling blown across both surfaces of the grating is both easy and cheap, but has been avoided in the past due to concerns of how the air density fluctuations will hurt beam quality. It is now shown that forced air cooling has no adverse effect on the M 2 parameter due to density fluctuations in the air, and can efficiently cool VBG’s such that no degradation in beam quality is seen due to thermal distortions. Volume Bragg gratings are routinely made with low absorption on the level of 10 -4 cm -1 . To model grating operation for kilowatt level lasers, absorption of the studied grating was artif icially increased by 140 times. Thus the use of 80 W fiber lasers enabled imitation of 11kW beams, and the effects of forced air cooling on the beam quality were measured. Without cooling, the M

The recent development of kW fiber laser sources makes the concept of laser systems operating at power levels from tens of kilowatts up to 100 -kilowatt levels a reality. The use of volume Bragg gratings for spectral beam combining is one approach to achieve that goal. To make such systems compact, lower the complexity an d minimize the induced thermal distortions we propose and demonstrate the use of special volume Bragg elements which have several Bragg gratings written inside as combining optical components. The multiplexed volume Bragg gratings (MVBGs) were recorded in photo -thermo refractive glass and three beams with total power of 420 W were successfully combined using one MVBG. The combining efficiency was 97% and there was no significant beam quality degradation. The results demonstrated that the approach of using m ultiplexed volume Bragg gratings for spectral beam combining is an excellent extension to the current state of the art combining techniques. Especially valuable is the capability to reduce the number of optical elements in the system and while be ing able t o manage the expected thermal load when kilowatt level sources are used for beam combining. Key Words : Spectral Beam Combining, Volume Bragg Gratings, Multiplexed Volume Bragg Gratings, High Power, Fiber Lasers

In an experimental study to obtain detailed heating data over the Space Shuttle Orbiter, CUBRC has completed an extensive matrix of experiments using three distinct models and two unique hypervelocity wind tunnel facilities. This detailed data will be employed to assess heating augmentation due to boundary layer transition on the Orbiter wing leading edge and wind side acreage with comparisons to computational methods and flight data obtained during the Orbiter Entry Boundary Layer Flight Experiment 1 and HYTHIRM 2 during STS-119, -128, -131, -133, and -134 re-entries. These comparisons will facilitate critical updates to the engineering tools employed to make assessments about natural and tripped boundary layer transition during Orbiter re-entry and to guide the design of future re-entry configurations. To achieve the goals of this study data was obtained over a range of Mach numbers from 10 to 18, with flight scaled Reynolds numbers and model attitudes representing key points on the Orbiter re-entry trajectory. The first of these studies were performed as an integral part of Return to Flight activities following the accident that occurred during the re-entry of the Space Shuttle Columbia (STS-107) in February of 2003 3 . This accident was caused by debris, which originated from the foam covering the external tank bipod fitting ramps, striking and damaging critical wing leading edge thermal protection panels that reside in the Orbiter bow shock/wing interaction region. During investigation of the accident aeroheating team members discovered that only a limited amount of experimental wing leading edge data existed in this critical peak heating area and a need arose to acquire a detailed dataset of heating in this region. This new dataset was acquired in two phases consisting of a risk mitigation phase employing a 1.8% scale Orbiter model with special temperature sensitive paint covering the wing leading edge and the primary 1.8% scale Orbiter model with detailed thin- film resolution in both the span and chord direction in the area of peak heating. Additional objectives of this first study included: obtaining natural or tripped turbulent wing leading edge heating levels, assessing the effectiveness of protuberances and cavities placed at specified locations on the orbiter over a range of Mach numbers and Reynolds numbers to evaluate and compare to existing engineering and computational tools, obtaining cavity floor heating to aid in the verification of cavity heating correlations, acquiring control surface deflection heating data on both the main body flap and elevons, and obtain high speed schlieren videos of the interaction of the orbiter nose bow shock with the wing leading edge. To support these objectives, the stainless steel 1.8% scale orbiter model in addition to the sensors on the wing leading edge was instrumented down the windward centerline, over the wing acreage on the port side, and painted with

In support of the Boundary Layer Transition Flight Experiment (BLT FE) Project, a manufactured protuberance tile was installed on the port wing of Space Shuttle Orbiter Discovery for STS-119, STS-128, STS-131 and STS-133 as well as Space Shuttle Endeavour for STS-134. Additional instrumentation was installed in order to obtain more spatially resolved measurements downstream of the protuberance. This paper provides an overview of the BLT FE Project with emphasis on the STS-131 and STS-133 results. A high-level overview of the in-situ flight data is presented, along with a summary of the comparisons between pre- and post-flight analysis predictions and flight data. Comparisons show that empirically correlated predictions for boundary layer transition onset time closely match the flight data, while predicted surface temperatures were significantly higher than observed flight temperatures. A thermocouple anomaly observed on a number of the missions is discussed as are a number of the mitigation actions that will be taken on the final flight, STS-134, including potential alterations of the flight trajectory and changes to the flight instrumentation.

In support of the Boundary Layer Transition Flight Experiment (BLT FE) Project, a manufactured protuberance tile was installed on the port wing of Space Shuttle Orbiter Discovery for the flights of STS-119, STS-128 and STS-131. Additional instrumentation was installed in order to obtain more spatially resolved measurements downstream of the protuberance. This paper provides an overview of the BLT FE Project. Significant efforts were made to place the protuberance at an appropriate location on the Orbiter and to design the protuberance to withstand the expected environments. A high-level overview of the in-situ flight data is presented, along with a summary of the comparisons between pre- and post-flight analysis predictions and flight data. Comparisons show that predictions for boundary layer transition onset time closely match the flight data, while predicted temperatures were significantly higher than observed flight temperatures.

This chapter defines USB specifications, drivers, buffers, and types of overflows. It explores the historical aspects of the threats, peers into the future, and explains how one can detect and protect against these threats. Exploits that target buffer overflows are commonly used against operating systems, applications, or their dependencies. These can be considered the most common types of vulnerabilities still employed against legacy and current operating environments. Their exploitation usually relies on the modification of input variables similar to techniques used in SQL injection strikes. Individuals familiar with the exploitation of buffer overflows are usually well versed in x86 assembly and C languages, as well as have a general understanding of the respective operating system architecture. A crucial factor in keeping buffer pirates at bay is frequent updates to all system software. By default, Windows update and Microsoft update services will be set to automatic and should be left in this state. Most third-party applications and system utilities provide automatic updates for their components, and these should be enabled where applicable. Beware that some applications, plug-ins, and drivers are not automatically updated, and these will need to be managed using alternative methods.

We are currently facing a problem of pandemic proportions with viruses and other forms of malicious code being propagated through unexpected avenues. Advanced tactics are making it increasingly difficult to identify the actual source of this mischief. A majority of these threats now appear to be originating from Asia with fluctuating functionality. A While the risk of being exposed to malicious code is nothing new, how you can be exposed to it is swiftly transforming.

Publisher Summary This chapter focuses on Universal Serial Bus (USB) Hacksaw. It outlines the risks induced, and the available mitigation techniques for the systems. The original Hacksaw version was designed to use any configurable flash drive that can be customized with a compact disc, read-only memory (CD-ROM) partition. By leveraging the unique features of the U3 flash drives, it has the capability to install silently upon insertion. The drive will then act in a Trojan-like fashion as it copies the payload to an inconspicuous location, typically by way of an autorun mechanism enabled by the U3 CD-ROM emulation. The payload will then reside on the host by executing an initialization script each time the system is restarted. Once this is accomplished, the program monitors the system for external drives, and when detected, it will compress, split, and replicate all data to a mail account of the attacker stealthily. The Hacksaw puts a new spin on data security by preying on unsuspecting victims who do not comprehend the degree of negligence they might be exuding. New versions of this utility are already in the wild ready to pounce on systems deemed to have adequate protection. It seems the only protection against this is the education of the users who interact with the systems that can fall victim to these and related attacks.

Publisher Summary This chapter examines the USB Switchblade to uncover the clever yet mischievous usages this device can be engaged in. The Switchblade has more potential to wreak a higher degree of havoc on a system and its environment than its cousin, the Hacksaw. Administrator-level privileges are required to run most of the tools included in the Switchblade packages. The premise behind Switchblade is to provide a means for gathering vital information about a Windows system or the network in which it resides. Its modular design allows for developers to include additional toolsets and features with minimal effort. This tool would significantly benefit any administrator in need of a standard utility devised for isolated system troubleshooting and analysis. Data often thought to be inaccessible from a physical standpoint is now nearly effortlessly attainable. Most of the tools used by the USB Switchblade have been around for years. Information technology administrators and engineers are likely very familiar with some of these tools, just not the deployment methods. As with the USB Hacksaw, the method of use is what is important. As with most security strategies, a layered approach applied against USB types of attacks can be the most effective. Considering the convenient usages for auditing and general system administration, this deployment method could significantly increase in popularity. There are a large number of possible mutations a device of the Switchblade sort can take.

The Hypersonic Thermodynamic Infrared Measurement (HYTHIRM) project is presently focused on near term support to the Shuttle program through the development of an infrared imaging capability of sufficient spatial and temporal resolution to augment existing on-board Orbiter instrumentation. Significant progress has been made with the identification and inventory of relevant existing optical imaging assets and the development, maturation, and validation of simulation and modeling tools for assessment and mission planning purposes, which were intended to lead to the best strategies and assets for successful acquisition of quantitative global surface temperature data on the Shuttle during entry. However, there are longer-term goals of providing global infrared imaging support to other flight projects as well. A status of HYTHIRM from the perspective of how two NASA-sponsored boundary layer transition flight experiments could benefit by infrared measurements is provided. Those two flight projects are the Hypersonic Boundary layer Transition (HyBoLT) flight experiment and the Shuttle Boundary Layer Transition Flight Experiment (BLT FE), which are both intended for reducing uncertainties associated with the extrapolation of wind tunnel derived transition correlations for flight application. Thus, the criticality of obtaining high quality flight data along with the impact it would provide to the Shuttle program damage assessment process are discussed. Two recent wind tunnel efforts that were intended as risk mitigation in terms of quantifying the transition process and resulting turbulent wedge locations are briefly reviewed. Progress is being made towards finalizing an imaging strategy in support of the Shuttle BLT FE, however there are no plans currently to image HyBoLT.

The Columbia accident on February 1, 2003 began an unprecedented level of effort within the hypersonic aerothermodynamic community to support the Space Shuttle Program. During the approximately six month time frame of the primary Columbia Accident Investigation Board activity, many technical disciplines were involved in a concerted effort to reconstruct the last moments of the Columbia and her crew, and understand the critical events that led to that loss. Significant contributions to the CAIB activity were made by the hypersonic aerothermodynamic community(REF CAIB) in understanding the re-entry environments that led to the propagation of an ascent foam induced wing leading edge damage to a subsequent breech of the wing spar of Columbia, and the subsequent breakup of the vehicle. A core of the NASA hypersonic aerothermodynamics team that was involved in the CAIB investigation has been combined with the United Space Alliance and Boeing Orbiter engineering team in order to position the Space Shuttle Program with a process to perform in-flight Thermal Protection System damage assessments. This damage assessment process is now part of the baselined plan for Shuttle support, and is a direct out-growth of the Columbia accident and NASAs response. Multiple re-entry aeroheating tools are involved in this damage assessment process, many of which have been developed during the Return To Flight activity. In addition, because these aeroheating tools are part of an overall damage assessment process that also involves the thermal and stress analyses community, in addition to a much broader mission support team, an integrated process for performing the damage assessment activities has been developed by the Space Shuttle Program and the Orbiter engineering community. Several subsets of activity in the Orbiter aeroheating communities support to the Return To Flight effort have been described in previous publications (CFD?, Cavity Heating? Any BLT? Grid Generation?). This work will provide a description of the integrated process utilized to perform Orbiter tile damage assessment, and in particular will seek to provide a description of the integrated aeroheating tools utilized to perform these assessments. Individual aeroheating tools will be described which provide the nominal re-entry heating environment characterization for the Orbiter, the heating environments for tile damage, heating effects due to exposed Thermal Protection System substrates, the application of Computational Fluid Dynamics for the description of tile cavity heating, and boundary layer transition prediction. This paper is meant to provide an overall view of the integrated aeroheating assessment process for tile damage assessment as one of a sequence of papers on the development of the boundary layer transition prediction capability in support of Space Shuttle Return To Flight efforts.

Currently, most antenna array designs are mechanically steered. However, as demand for higher performance antennas increases, an electronic replacement for the mechanical system becomes necessary. An alternative that may prove to be more cost effective is to use ferrite patch antennas as the elements in the array. The antenna's radiation characteristics are controlled by the direction and magnitude of the imposed magnetic fields that bias the ferrite. This is accomplished without requiring additional circuitry in the signal path. An initial study of this type of device was performed. The advanced ferrite handling capability of Ansoft HFSS was used to simulate the radiation characteristics of ferrite patch antennas. The simulation capability of this finite element field simulation tool with its advanced absorbing boundary condition to simulate ferrite patch antennas was studied. The advantage of this type of solver is the ability to analyze ferrites with non-uniform bias fields. Through this investigation a better understanding of the operating characteristics of ferrite patch antennas was achieved.