Requirements for a 4ω Thomson scattering system on megajoule scale laser facilities

With the arrival of megajoule class laser facilities, the features of laser-produced plasmas are evolving toward unprecedented high electron temperatures reached in the environment of a cm-scale indirect-drive Hohlraum for a few tens of nanoseconds. In this context, the need for in situ experimental characterization of the plasma parameters becomes critical in order to test hydrodynamics simulations in these novel conditions. Taking advantage of the progress achieved in the last 40 years, Thomson scattering has become a classic diagnostic in the characterization of laser produced plasmas. However, the many beam configuration of the megajoule scale experiments makes the measurements increasingly complex because the Thomson scattering signals produced by the 351 nm heaters themselves dominate the plasma emission around 263 nm, a wavelength range typically of interest when a 4ω Thomson probe is used. This paper reviews the requirements for and the potential of a 4ω Thomson scattering system to be operated on such 351 nm megajoule scale facilities in order to characterize the hot (T_e > 3 keV) plasmas produced in the indirect-drive irradiation of a Hohlraum. It is found that the configuration of the diagnostic could be optimized in order to enable the detection of the ion acoustic resonances over a large domain of plasma parameters. The results for the electron plasma wave resonances are also given.

Visual Function and Visual Acuity in An Urban Adult Population

In this survey, 6,850 Baltimore residents aged 40 and older were interviewed about activities they had difficulty doing or could no longer do because of poor vision. One-fourth of the sample reported limitations in activities, most frequently reading and other near-vision tasks, because of poor vision. In addition to poor vision, general health status, educational level, and time since the last eye care visit were associated with the loss of visual function.

OP0071 PREDICTING PERSISTENT HIGH-DOSE OPIOID USE AFTER TOTAL KNEE REPLACEMENT

Background:

Patients undergoing total knee replacement (TKR) are at increased risk of persistent opioid use and dependence

Objectives:

To identify patients with persistent high-dose opioid use after TKR using group-based trajectory models (GBTM) and determine predictors of persistent high-dose opioid users using pre-TKR patient characteristics

Methods:

Using US Medicare claims (2010-2014), we identified patients aged ≥65 years who underwent a TKR and had no history of cancer or high-dose opioid use (>25 mean morphine equivalents (MME)/day) in the year prior. All patients were continuously enrolled in Medicare for ≥360 days prior to and ≥30 days after the TKR. To determine opioid filling patterns after the surgery, patients were followed up to 360 days from the day of TKR. We modeled 12 monthly indicators of opioid prescription fills as a continuous (MME/day) variable using a censored normal GBTM and categorized patients into 4 groups. The primary outcome was persistent high-dose opioid use defined as patients in trajectory Group 3 (38.8 MME/day) or Group 4 (22.4 MME/day). We split the data into training (2010-2013 data) and test (2014 data) sets and used logistic regression to predict high-dose opioid use vs low-dose opioid use (Groups 1 and 2) as a binary outcome utilizing pre-TKR patient characteristics as candidate predictors using the least absolute shrinkage and selection operator (LASSO) regression for variable selection. A reduced model with only 10 pre-specified variables readily available for clinical use was also considered

Results:

The final study cohort included 142,089 patients. The GBTM identified 4 distinct trajectories (Group 1- Short-term, low-dose, Group 2- long-term, low-dose, Group 3- medium-term, high-dose, Group 4-long-term, high-dose) of opioid use in the year after TKR(Figure). Using logistic regression and LASSO, we predicted the probability of persistent high-dose opioid use (N=17,171) (vs. low-dose opioid use) in the training set (N=101,810) for an AUC=0.80. The AUC in the test set (N=40,279) predicting high opioid use (N=5,893) was 0.77. The final model selected 33 variables and identified baseline history of opioid use as the strongest positive predictor of high-dose persistent opioid use. The reduced model with only ten predictors also performed equally well (AUC=0.77)(Table).

Conclusion:

In this cohort of older patients with no history of cancer or high-dose opioid use at baseline, 16.2% became high dose (28.1 MME/day) opioid users during the year after TKR. Our prediction model with 10 readily available clinical factors may help identify patients at high risk of future adverse outcomes from persistent opioid use and dependence after TKR

Figure.

 Trajectories of opioid use patterns after TKR

Table.

Predictors of persistent high-dose opioid use in the reduced mode

VariableMultivariable Odds Ratio (95% CI)Predicting High dose vs.Low dose opioid useP-valueAge (in years)0.94 (0.93-0.94)<0.001Females (Ref=Males)0.99 (0.93-1.06)0.78White race (Ref=Other)1.25 (1.04-1.50)0.02Baseline opioid use (MME/day)1.22 (1.22-1.23)<0.001Substance use (Yes/No)1.10 (1.02-1.20)0.02Benzodiazepine use (Yes/No)1.22 (1.12-1.32)<0.001Anxiolytic use (Yes/No)1.30 (1.19-1.43)<0.001Anticonvulsant use (Yes/No)0.94 (0.87-1.03)0.19Antidepressant use (Yes/No)1.03 (0.96-1.11)0.36NSAID use (Yes/No)1.07 (1.00-1.14)0.04

Disclosure of Interests:

Chandrasekar Gopalakrishnan: None declared, Jessica Franklin: None declared, Yinzhu Jin: None declared, Daniel Solomon Grant/research support from: Funding from Abbvie and Amgen unrelated to this work, Jeffrey Katz Grant/research support from: Dr Katz reported receiving grants from Samumed and Flexion Therapeutics outside the submitted work., Yvonne Lee Shareholder of: Cigna-Express Scripts, Grant/research support from: Pfizer, Consultant of: Highland Instruments, Inc., Patricia Franklin: None declared, Joyce Lii: None declared, Rishi J Desai Grant/research support from: Dr. Desai reported receiving grants from Bayer, Novartis, and Vertex Pharmaceuticals outside the submitted work., Seoyoung Kim Grant/research support from: Seoyoung C Kim has received research grants from AbbVie, Roche, Bristol-Myers Squibb and Pfizer.

Measurement of Kinetic-Scale Current Filamentation Dynamics and Associated Magnetic Fields in Interpenetrating Plasmas

We present the first local, quantitative measurements of ion current filamentation and magnetic field amplification in interpenetrating plasmas, characterizing the dynamics of the ion Weibel instability. The interaction of a pair of laser-generated, counterpropagating, collisionless, supersonic plasma flows is probed using optical Thomson scattering (TS). Analysis of the TS ion-feature revealed anticorrelated modulations in the density of the two ion streams at the spatial scale of the ion skin depth c/ω_{pi}=120  μm, and a correlated modulation in the plasma current. The inferred current profile implies a magnetic field amplitude ∼30±6  T, corresponding to ∼1% of the flow kinetic energy, indicating that magnetic trapping is the dominant saturation mechanism.

Plasma Collision in a Gas Atmosphere

We present a study on the impact of a gas atmosphere on the collision of two counterpropagating plasmas (gold and carbon). Imaging optical Thomson scattering data of the plasma collision with and without helium in between have been obtained at the Omega laser facility. Without gas, we observed large scale mixing of colliding gold and carbon ions. Once ambient helium is added, the two plasmas remain separated. The difference in ionic temperature is consistent with a reduction of the maximum Mach number of the flow from M=7 to M=4. It results in a reduction of a factor ∼10 of the counterstreaming ion-ion mean free path. By adding a low-density ambient gas, it is possible to control the collision of two high-velocity counterstreaming plasma, transitioning from an interpenetrating regime to a regime in agreement with a hydrodynamic description.

Evolution of the Electron Distribution Function in the Presence of Inverse Bremsstrahlung Heating and Collisional Ionization

The picosecond evolution of non-Maxwellian electron distribution functions was measured in a laser-produced plasma using collective electron plasma wave Thomson scattering. During the laser heating, the distribution was measured to be approximately super-Gaussian due to inverse bremsstrahlung heating. After the heating laser turned off, collisional ionization caused further modification to the distribution function while increasing electron density and decreasing temperature. Electron distribution functions were determined using Vlasov-Fokker-Planck simulations including atomic kinetics.

Predictors of Post-operative Pain and Opioid Consumption in Patients Undergoing Liver Surgery

BACKGROUND

Post-operative pain management is a critical component of perioperative care. Patients at risk of poorly controlled post-operative pain may benefit from early measures to optimize pain management. We sought to identify risk factors for post-operative pain and opioid consumption in patients undergoing liver resection.

METHODS

This is a multi-institutional prospective nested cohort study of patients undergoing open liver resection. Opioid consumption and pain scores were collected following surgery. To estimate the effects of patient factors on opioid consumption (oral morphine equivalents-OME) and on pain scores (NRS-11), we used generalized linear models and multivariable linear regression model, respectively.

RESULTS

One hundred and fifty-three patients who underwent open liver resection between 2013 and 2016 were included in the study. The mean patient age was 62.2 years, and 43.3% were female. Younger patients were significantly more likely to use more opioids in the early post-operative period (16.7 OME/10 years, p < 0.001). Patient factors that were significantly associated with increased NRS-11 pain scores also included younger patient age (difference in pain score of 0.3/10 years with cough and 0.2/10 years at rest, p < 0.01 for both) as well as a history of analgesic use (difference in pain score of 0.9 with cough and 0.6 at rest, p < 0.01 and p = 0.07, respectively).

CONCLUSION

Younger patients and those with a history of analgesic use are more likely to report higher post-operative pain and require higher doses of opioids. Early identification of these patients, and measures to better manage their pain, may contribute to optimal perioperative care.

Picosecond Thermodynamics in Underdense Plasmas Measured with Thomson Scattering

The rapid evolutions of the electron density and temperature in a laser-produced plasma were measured using collective Thomson scattering. Unprecedented picosecond time resolution, enabled by a pulse-front-tilt compensated spectrometer, revealed a transition in the plasma-wave dynamics from an initially cold, collisional state to a quasistationary, collisionless state. The Thomson-scattering spectra were compared with theoretical calculations of the fluctuation spectrum using either a conventional Bhatnagar-Gross-Krook (BGK) collision operator or the rigorous Landau collision terms: the BGK model overestimates the electron temperature by 50% in the most-collisional conditions.

Oral hygiene, prevalence of gingivitis, and associated risk factors among pregnant women in Sarlahi District, Nepal

BACKGROUND

The oral health status of pregnant women in low-resource communities such as Nepal has not been well characterized. This sub-population is also of specific interest given associations between poor oral health and adverse pregnancy outcomes previously documented in other settings. We explored relationships between gingivitis and risk factors among pregnant women in rural Nepal.

METHODS

The design was a community-based, cross-sectional study in a sub-area of Sarlahi District, Nepal. Pregnant women < 26 weeks gestation underwent clinical periodontal exams conducted by community-based oral health workers. Exams included a full mouth assessment measuring bleeding on probing (BOP), probing depth (PD) (six sites per tooth), and gingival recession, the distance from the cemento-enamel junction to the free gingival margin (two direct sites per tooth). Data on participant risk factors were collected through household surveys, including demographic characteristics, oral health behaviors, care seeking, and health attitudes. Multivariable logistic regression modeling was used to assess relationships between gingivitis and risk factors.

RESULTS

We enrolled 1452 participants, of which 40% (n = 582) had signs of clinical gingivitis and 60% (n = 870) clinical health. Average participant age was 23. Most participants (88%) had never received oral health care. Participants averaged 10% of sites with BOP with most (79%) having ≥1 site with BOP. Nine percent of participants had ≥1 site with PD ≥4 mm, although very few participants (0.7%) had sites with PD ≥5 mm. Few participants (13%) had any recession (≥1 mm). In the final adjusted model, odds of gingivitis increased by 3% for each year of age (aOR 1.03, 95% CI 1.00, 1.06) and were higher for women of short maternal stature (< 150 cm) (aOR 1.43, 95% CI: 1.14, 1.79) and among women reporting cost to be a barrier to seeking dental care (aOR 2.13, 95% CI: 1.09, 4.15).

CONCLUSIONS

Gingivitis was common and associated with age, maternal stature, self-reported high cost of dental care, and other risk factors among pregnant women in rural Nepal.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01177111 (Nepal Oil Massage Study) and NCT02788786 (Pilot Trial).

Measurement of apparent ion temperature using the magnetic recoil spectrometer at the OMEGA laser facility

The Magnetic Recoil neutron Spectrometer (MRS) at the OMEGA laser facility has been routinely used to measure deuterium-tritium (DT) yield and areal density in cryogenically layered implosions since 2008. Recently, operation of the OMEGA MRS in higher-resolution mode with a new smaller, thinner (4 cm², 57 μm thick) CD₂ conversion foil has also enabled inference of the apparent DT ion temperature (T _ion) from MRS data. MRS-inferred T _ion compares well with T _ion as measured using neutron time-of-flight spectrometers, which is important as it demonstrates good understanding of the very different systematics associated with the two independent measurements. The MRS resolution in this configuration, ΔE _MRS = 0.91 MeV FWHM, is still higher than that required for a high-precision T _ion measurement. We show how fielding a smaller foil closer to the target chamber center and redesigning the MRS detector array could bring the resolution to ΔE _MRS = 0.45 MeV, reducing the systematic T _ion uncertainty by more than a factor of 4.

Supersonic gas-jet characterization with interferometry and Thomson scattering on the OMEGA Laser System

A supersonic gas-jet target platform has been activated on the OMEGA Laser System. An analytic model for gas dynamics in a supersonic nozzle was used to predict gas-plume parameters and to design nozzles for use in laser-plasma experiments. The gas-jet system was analyzed with a Mach-Zehnder interferometer to study neutral density and with Thomson scattering to study plasma parameters on the OMEGA Laser System. These initial measurements demonstrate the capabilities of the OMEGA gas jet as a platform for future laser-plasma interaction science.

Unabsorbed light beamlets for diagnosing cross-beam energy transfer

A new diagnostic has been fielded on OMEGA to diagnose cross-beam energy transfer (CBET) during direct-drive implosions. Unabsorbed light from each OMEGA laser beam is imaged as a distinct "spot" onto a gated optical imager. Each spot is in essence the endpoint of a beamlet of light that originates from different regions of each beam profile and follows a path determined by refraction. The intensity of light in the beamlet varies along its path as a result of absorption and CBET with other beamlets. This diagnostic allows the investigation of the effects of CBET on laser energy from specific locations of the beam profile. The diagnostic records images in two 200-ps time windows and includes a Wollaston prism to split each beamlet into two orthogonal polarizations recorded on separate images, allowing the absolute polarization of each beamlet to be determined. This diagnostic has provided the first evidence of polarization rotation caused by CBET during direct-drive implosions.

Observation of Nonlocal Heat Flux Using Thomson Scattering

Nonlocal heat flux was measured in laser-produced coronal plasmas using a novel Thomson scattering technique. The measured heat flux was smaller than the classical values inferred from the measured plasma conditions in regions with large temperature gradients and agreed with classical values for weak gradients. Vlasov-Fokker-Planck simulations self-consistently calculated the electron distribution functions used to reproduce the measured Thomson scattering spectra and to determine the heat flux. Multigroup nonlocal simulations overestimated the measured heat flux.

Ionization Waves of Arbitrary Velocity

Flying focus is a technique that uses a chirped laser beam focused by a highly chromatic lens to produce an extended focal region within which the peak laser intensity can propagate at any velocity. When that intensity is high enough to ionize a background gas, an ionization wave will track the intensity isosurface corresponding to the ionization threshold. We report on the demonstration of such ionization waves of arbitrary velocity. Subluminal and superluminal ionization fronts were produced that propagated both forward and backward relative to the ionizing laser. All backward and all superluminal cases mitigated the issue of ionization-induced refraction that typically inhibits the formation of long, contiguous plasma channels.

Oral health knowledge, behavior, and care seeking among pregnant and recently-delivered women in rural Nepal: a qualitative study

BACKGROUND

Oral health behavior and attitudes of pregnant women in low-income countries are rarely examined, yet should be considered when designing preventative or therapeutic studies to reduce burden of oral diseases. We aimed to understand dental care-seeking behavior, as well as oral health knowledge and attitudes of oral health among pregnant women in rural Nepal.

METHODS

Semi-structured in-depth interviews (n = 16) and focus group discussions (3 groups, n = 23) were conducted among pregnant and recently-delivered women in Sarlahi, Nepal. Transcripts were translated from the local language to English then analyzed using a hybrid approach to thematic coding with Atlas.ti version 7.

RESULTS

Women felt confident describing the signs and symptoms of tooth decay and gum disease, but were not knowledgeable about where to receive care for tooth and/or gum pain and relied heavily on the knowledge of their community. Some women used a toothbrush and toothpaste at least once a day to clean their teeth, but many reported the traditional use of a branch of a local shrub or tree as their teeth cleaning instrument. Women suggested a willingness to consider using an oral rinse throughout pregnancy, perceiving that it might have a positive impact on infant health.

CONCLUSIONS

Future studies should focus on providing adequate and sustainable resources for pregnant women in Nepal and other low income settings to engage in good oral health behaviors (possibly supported through community-based workers), to maintain dental hygiene, and to access qualified dentists as a means of improving their oral health.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01177111 (Nepal Oil Massage Study) and NCT02788786 (Pilot Trial).

Highly Resolved Measurements of a Developing Strong Collisional Plasma Shock

The structure of a strong collisional shock front forming in a plasma is directly probed for the first time in laser-driven gas-jet experiments. Thomson scattering of a 526.5 nm probe beam was used to diagnose temperature and ion velocity distribution in a strong shock (M∼11) propagating through a low-density (ρ∼0.01  mg/cc) plasma composed of hydrogen. A forward-streaming population of ions traveling in excess of the shock velocity was observed to heat and slow down on an unmoving, unshocked population of cold protons, until ultimately the populations merge and begin to thermalize. Instabilities are observed during the merging, indicating a uniquely plasma-phase process in shock front formation.

Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma

Magnetic fields are ubiquitous in the Universe. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of the luminous matter. The standard theoretical model for the origin of these strong magnetic fields is through the amplification of tiny seed fields via turbulent dynamo to the level consistent with current observations. However, experimental demonstration of the turbulent dynamo mechanism has remained elusive, since it requires plasma conditions that are extremely hard to re-create in terrestrial laboratories. Here we demonstrate, using laser-produced colliding plasma flows, that turbulence is indeed capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. These results support the notion that turbulent dynamo is a viable mechanism responsible for the observed present-day magnetization.

Post hoc support vector machine learning for impedimetric biosensors based on weak protein–ligand interactions

We develop a simple, open source machine learning algorithm for analyzing impedimetric biosensor data using a mobile phone.

Validation of an obstetric fistula screening questionnaire in rural Nepal: a community-based cross-sectional and nested case-control study with clinical examination

OBJECTIVE

To validate a symptom-based fistula screening questionnaire and estimate obstetric fistula (OF) prevalence in rural Nepal.

DESIGN

Cross-sectional and nested case-control study.

SETTING

Sarlahi District, Nepal.

POPULATION

Parous, reproductive age women.

METHODS

The questionnaire assessed symptoms of vesicovaginal and rectovaginal fistula (VVF and RVF, respectively), stress and urge urinary incontinence (SUI and UUI, respectively), fecal incontinence (FI), and included interviewer observations on the smell and presence of urine and/or stool. All women who screened positive for OF and a randomly selected group of women who screened negative for OF were included in a nested case-control study (one case, four normal controls, and four incontinent controls) and underwent confirmatory clinical examinations.

MAIN OUTCOME MEASURES

Clinically confirmed OF, and questionnaire sensitivity (Se) and specificity (Sp).

RESULTS

Of the 16 893 women who completed cross-sectional screening, 68 were screened-positive cases. Fifty-five (82%) screened-positive cases, 203 screened-negative normal controls, and 203 screened-incontinent controls participated in the case-control study, which confirmed one case of VVF and one case of both VVF and RVF without any false-negative cases. For VVF, the screening tool demonstrated Se 100% (95% CI 34.2-100.0%), Sp 86.9% (95% CI 83.3-89.9%), and estimated VVF prevalence as 12 per 100 000 (95% CI 3-43); for RVF, it demonstrated Se 100% (95% CI 20.7-100.0), Sp 99.8% (95% CI 98.6-100.0), and estimated RVF prevalence as 6 per 100 000 (95% CI 1-34).

CONCLUSIONS

The OF screening questionnaire demonstrated high sensitivity and specificity in this low-prevalence setting.

TWEETABLE ABSTRACT

Community-based obstetric fistula screening tool validation study, Nepal, n = 16 893: High Se, Sp & feasibility.