Effect of Different Substitutions at the 1,7-Bay Positions of Perylenediimide Dyes on Their Optical and Laser Properties.

Perylenediimide (PDI) compounds are widely used as the active units of thin-film organic lasers. Lately, PDIs bearing two sterically hindering diphenylphenoxy groups at the 1,7-bay positions have received attention because they provide a way to red-shift the emission with respect to bay-unsubstituted PDIs, while maintaining a good amplified spontaneous emission (ASE) performance at high doping rates. Here, we report the synthesis of a series of six PDI derivatives with different aryloxy groups (PDI 6 to PDI 10) or ethoxy groups (PDI 11) at the 1,7 positions of the PDI core, together with a complete characterization of their optical properties, including absorption, photoluminescence, and ASE. We aim to stablish structure-property relationships that help designing compounds with optimized ASE performance. Film experiments were accomplished at low PDI concentrations in the film, to resemble the isolated molecule behaviour, and at a range of increasing doping rates, to investigate concentration quenching effects. Compounds PDI 10 and PDI 7, bearing substituents in the 2' positions of the benzene ring (the one contiguous to the linking oxygen atom) attached to the 1,7 positions of the PDI core, have shown a better threshold performance, which is attributed to conformational (steric) effects. Films containing PDI 11 show dual ASE.

Green and wide acceptance angle solar concentrators.

A low-toxicity photopolymer was employed to prepare holographic solar concentrators (HSCs). The main aim of this study is to obtain a versatile holographic element to concentrate the sunlight from different relative positions of the Sun during the day, avoiding the need of expensive tracking systems. Multiplexed holographic elements that combine symmetric and asymmetric holographic lenses of low frequency (545 l/mm) have been recorded in the same plate to concentrate the sunlight from sunrise to sunset. The holographic behavior of HSCs has been studied by measuring the angular diffraction efficiency at 633 nm (close to the maximum response of silicon cells). The efficiency of the complete system "HSC-solar cell" has been evaluated by measuring the short-circuit current (Isc) under solar illumination at different incident angles. This study overcomes the trade-off between good efficiency and high incident acceptance angle, showing an important breakthrough to obtain wide acceptance angle systems.

Tunable Waveguides Couplers Based on HPDLC for See-Through Applications.

Photopolymers have become an important recording material for many applications, mainly related to holography. Their flexibility to change the chemical composition together with the optical properties made them a versatile holographic recording material. The introduction of liquid crystal molecules in a photopolymer based on multifunctional monomer provides us the possibility to generate tunable holograms. The switchable holographic elements are a key point for see-through applications. In this work, we optimize the holographic polymer-dispersed liquid crystals composition to improve the performance of tunable waveguide couplers based on transmission gratings and specifically their response under an applied electric field. A variation around 60% in the transmission efficiency was achieved.

Aberration-Based Quality Metrics in Holographic Lenses.

Aberrations and the image quality of holographic lenses were evaluated by a Hartmann-Shack (HS) wavefront sensor. Two lenses, one recorded with a symmetrical configuration and the other with an asymmetrical one, were stored in a photopolymer called Biophotopol. Each was reconstructed with two different wavelengths, 473 nm and 633 nm. Different metrics were applied to determine and quantify the aberration of the lenses (Zernike coefficients, Seidel coefficients, Marechal tolerances, root-mean-square (RMS), peak to valley, critical fraction of the pupil), and the quality of the image they provided (Strehl ratio, entropy, cutoff frequency, modulation transfer function (MTF), and area under the MTF). Good agreement between the metrics related to optical quality was obtained. The negative asymmetric holographic lenses had less aberration than the positive symmetric ones.

Costs Analysis of Fibrin Sealant for Prevention of Anastomotic Leakage in Lower Colorectal Surgery.

INTRODUCTION: Postoperative anastomotic leaks remain a common and serious complication of colorectal surgeries and are a major cause of mortality and morbidity of these procedures. Anastomotic leaks (AL) have been extensively studied; however, there has been no significant reduction in their prevalence over time. In addition, there is a significant economic burden from AL attributed to the need for repeat surgery, radiologic intervention and lengthened hospital stay. We conducted a comparative cost analysis of patients undergoing colorectal surgery with anastomosis, with the application of fibrin sealant (FS) to the sutured anastomosis versus not treating the sutured anastomosis with FS. METHODS: The deterministic decision-tree model was populated with clinical data including operating room time, hospitalization days, occurrence of AL, need for revision surgery, blood products and radiologic interventions to treat the AL in lower colorectal surgery. A systematic literature review was conducted to identify appropriate studies with these variables. RESULTS: The average cost per case treated lower colorectal surgery with fibrin sealant glue 10 mL Tisseel® and those not treated with a fibrin sealant after suturing the anastomoses was €3233 and €4130, respectively, for resource expenses paid by the healthcare system. This would suggest potential savings of €897 per surgery, achieved through the application of FS to the sutured anastomosis for preventing AL following colorectal surgery. CONCLUSION: Application of FS to the sutured anastomosis in lower colorectal surgery resulted in a decrease in post-operative AL, and cost savings based on a reduction in hospitalization days, a reduction needing: revision surgery, radiologic intervention and blood products to treat AL.

LED-Cured Reflection Gratings Stored in an Acrylate-Based Photopolymer.

The storage of volume holographic reflection gratings in low-toxicity photopolymers represents a challenge at present since they can be used in many important applications such as biosensors and holographic optical elements. In this context, an acrylate-based photopolymer developed in our research group was employed to study the recording of unslanted holographic reflection gratings at high spatial frequencies. The optimal preparation conditions of the photopolymer layers were determinated. The diffraction efficiencies are measured in both recording and curing stage and a comparative study of these values was realized. In addition, a theoretical study using Kogelnik's coupled wave theory was carried out with the aim of understanding the diffraction efficiency behaviour of both processes. In this work, a maximum diffraction efficiency of 14.1% was reached after a curing process in 150 µm layers at a recording wavelength of 488 nm. This value represents a good result compared to that reported in the literature and opens the way to reflection mode holography research using low-toxicity material.

Influence of Tert-Butylthiol and Tetrahydrofuran on the Holographic Characteristics of a Polymer Dispersed Liquid Crystal: A Research Line Toward a Specific Sensor for Natural Gas and Liquefied Petroleum Gas.

Tert-Butylthiol (TBT) and tetrahydrothiophene (THT) are odorant substances added to natural gas and liquefied petroleum gas to help their detection by the human smell. In this research, TBT and THT are incorporated into a holographic polymer-dispersed liquid crystal and their influence in the main holographic characteristics of the photopolymer are studied in order to open the way towards the design of a holographic sensor to detect natural gas and liquefied petroleum gas.

Cost-consequence analysis of a hemostatic matrix alone or in combination for spine surgery patients.

BACKGROUND: A five-year retrospective database analysis comparing the use of Floseal 1 flowable topical hemostat alone (F) and in combination with gelatin/thrombin (F + G/T) to achieve hemostasis and control surgical bleeding showed higher resource utilization for F + G/T cases relative to F matched pairs during spinal surgery. Lower resource use in the F group was characterized by shorter hospital length of stay and surgical time as well as fewer blood transfusions and less hemostat agent used per surgery. OBJECTIVE: To evaluate the cost-consequence of using F compared to F + G/T in minor, major and severe spinal surgery from the US hospital perspective. METHODS: A cost-consequence model was developed using the US hospital perspective. Model inputs include clinical inputs from the literature, cost inputs (hemostatic matrices, blood product transfusion, hospital stay and operating room time) from the literature, and an analysis of annual spine surgery volume (minor, major and severe) using the 2012 National Inpatient Sample (NIS) database. Costs are reported in 2017 US dollars. One-way and probabilistic sensitivity analyses address sources of variability in the results. RESULTS: A medium-volume hospital (130 spine surgeries per year) using F versus F + G/T for spine surgeries is expected to require 85 less hours of surgical time, 58 fewer hospital days and 7 fewer blood transfusions in addition to hemostat volume savings (F: 1 mL, thrombin: 1994 mL). The cost savings associated with the hospital resources for a medium-volume hospital are expected to be $317,959 (surgical hours = $154,746, hospital days = $125,237, blood transfusions = $19,023, hemostatic agents = $18,953) or $2445 per spine surgery. CONCLUSIONS: The use of F versus F + G/T could lead to annual cost savings for US hospitals performing a low to high volume of spinal surgeries per year.

Cost comparison of fibrin sealant versus tack screws for mesh fixation in laparoscopic repair of inguinal hernia.

OBJECTIVES: Inguinal hernias of the abdominal wall are common accounting for 75% of all hernia defects. They can be treated with laparoscopic surgery using a transabdominal preperitoneal (TAPP) approach. However, in surgery there is some contention on how to conclude the hernia repair, as there are alternatives of using fibrin sealant (FS) or tack screws for fixation of a mesh implant over the defect in the abdominal wall. In this study, we evaluate the economic consequences of using FS vs. tacks for mesh fixation in TAPP inguinal hernia repair for the UK from a hospital perspective. METHODS: The model was populated with clinical inputs (theater time, hospitalization days, occurrence of seroma, and neuralgia) from a previously conducted study comparing FS and tack screws in patients who had undergone TAPP hernia repair, and cost inputs from official government sources. One-way sensitivity analyses were also conducted to evaluate key drivers of cost analyses. RESULTS: The average cost per case treated with FS 2 mL Tisseel® and tack screws (ProTackTM) was £1,098 and £1,348, respectively, for resource expenses paid by the healthcare system. This would suggest a potential savings achieved of £249 per surgery using FS for mesh fixation. The sensitivity analysis showed that the key drivers for the cost difference were a variation in time to complete the surgery, followed by hospitalization days, and lower adverse outcomes such as seroma and neuralgia in the two cohorts. CONCLUSION: Using FS resulted in cost savings in hospitals based on reduced time to complete surgery, hospitalization time post-op, and lower adverse outcomes. Indirect cost savings were also found in favor of FS when comparing the two alternatives from a societal perspective, as patients were able to return to work more promptly in the FS group versus the tack screws group.

Floseal only versus in combination in spine surgery: a comparative, retrospective hospital database evaluation of clinical and healthcare resource outcomes.

OBJECTIVE: Flowable agents such as Floseal® (F) are often reserved as adjuncts to non-flowable agents (i.e. gelatin (G) sponges and thrombin (T)) when bleeding is not sufficiently controlled. Based on their perceived positive impact, it is postulated that flowable agents alone may result in better clinical and resource utilization outcomes. Clinical and health-care utilization outcomes were compared in this retrospective analysis of spine surgery cases with charges for Floseal only (FO) and F + G/T. METHODS: The United States Premier Hospital Database was searched for adult spine surgeries performed between October 2010 and September 2015 with FO or F and G/T charges. To obtain an unbiased treatment estimate, 1:1 propensity-score matching was used to identify FO and F + G/T cohorts. The cohorts were compared for rates of intraoperative, perioperative, postoperative and transfusion; blood loss-related, serious and other complications; hospital length-of-stay (LOS), surgical time, and volume of hemostat charged. RESULTS: Among 40,335 spine surgeries, 15,105 FO and F + G/T matched pairs were compared. Significantly (p < 0.0001) lower percentages of FO than F + G/T cases received intraoperative (1.4% vs. 2.5%), perioperative (1.6% vs. 2.8%), postoperative (1.6% vs 3.0%), and any transfusion (2.3% vs. 4.3%). FO cases had significantly less blood loss complications than F + G/T cases (0.5% vs. 0.8%, p = 0.0022) and significantly (p < 0.0001) shorter hospital LOS (-0.45 days), surgical time (-39.0 min), and used less hemostat (-12.5 mL). CONCLUSIONS: Results from this observational hospital database analyses indicate that FO use in spine surgery is associated with lower blood transfusion use and blood loss complications compared to its use with adjunct non-flowable hemostatic agents. The shorter hospital stay, reduced surgical time, and less hemostat volume health-care utilization outcomes that favored FO versus combination use may translate to health system cost savings. Further validation of these findings using controlled clinical trials and cost-consequence studies is warranted. CLINICAL RELEVANCE: The use of flowable hemostatic agents alone may result in better clinical and possibly economic outcomes in spine surgery.

Holographic Lenses in an Environment-Friendly Photopolymer.

In this paper, we theoretically and experimentally evaluated the quality of volume phase transmission lenses stored in an environmentally friendly photopolymer. Holographic lenses (HLs) were obtained using symmetrical and asymmetrical experimental setups with the same positive and negative focal length and pupil diameter. The image quality was evaluated from the calculation of the modulation transfer function (MTF) by capturing the point spread function (PSF) with a charge-coupled device (CCD). A maximum frequency of 14 L/mm, reaching an MTF value of 0.1, was obtained for a negative asymmetrically recorded HL, evaluated at 473 nm wavelength. A theoretical study of aberrations was carried out to qualitatively evaluate the experimental results obtained.

Análise de custo-efetividade da terapia renal substitutiva contínua versus intermitente para pacientes graves com lesão renal aguda, na perspectiva do Sistema Suplementar de Saúde brasileiro / Cost-effectiveness analysis of continuous versus intermittent renal replacement therapy for critically ill acute kidney injury patients under the perspective of the Brazilian Private Healthcare System

Objetivo: O objetivo deste estudo é comparar custos e desfechos da Terapia de Substituição Renal Contínua (CRRT) versus Hemodiálise Intermitente (IRRT) em pacientes com lesão renal aguda sob a perspectiva do sistema suplementar de saúde no Brasil. Métodos: Um modelo analítico de decisão foi desenvolvido baseado nos resultados clínicos encontrados no estudo de Ethgen et al., 2015. Este estudo seguiu o padrão CHEERS (Consolidated Health Economic Evaluation Reporting Standards) para reportar a avaliação econômica. Quando a lesão renal aguda ocorre na UTI, inicia-se a CRRT ou IRRT. Definiu-se que o tempo de internação hospitalar e o tempo em UTI foram os mesmos para as duas modalidades. O modelo também assumiu que, se os pacientes ficassem dependentes de diálise, eles não recuperavam sua função renal e permaneciam em diálise ou evoluíam a óbito. O horizonte do estudo foi de 1 ano, 5 anos (caso-base) e 20 anos. Apenas custos diretos para o sistema privado foram considerados. Para desfechos clínicos (utilities), a referência foi o estudo de Klarenbach & Manns, 2009. Conforme diretrizes brasileiras de avaliação de tecnologias em saúde, tanto custos como desfechos foram descontados à taxa de 5% ao ano com análise de sensibilidade na faixa de 0% a 10% ao ano. Além disso, foram realizadas duas análises de sensibilidade: uma univariada e outra determinística bivariada considerando os dois parâmetros-chave que diferenciam CRRT de IRRT: a diferença de custo de implementação por dia e o risco cumulativo de dependência de diálise. Ambas as análises foram rodadas com o horizonte de tempo de 1 ano, 5 anos e de tempo total de vida. Para determinar se o tratamento era custo-efetivo, conforme práticas locais, utilizou-se o limiar de três vezes o Produto Interno Bruto (PIB) per capita, qual seja R$ 84.741 (3 x R$ 28.247). Resultados: Quando se compara CRRT à IRRT para o tratamento inicial da lesão renal aguda, CRRT é dominante versus IRRT a partir de 17 meses de tratamento. Com base nas premissas deste estudo, a coorte de pacientes inicialmente tratada com CRRT tem melhores desfechos clínicos (QALYs ­ Anos de Vida Ajustados pela Qualidade) e custos totais de tratamento mais baixos. Pacientes tratados com CRRT têm maior probabilidade de recuperar a função renal. Conclusão: Os resultados sugerem que CRRT, quando comparada à IRRT, pode ser considerada uma terapia preferencial, ou seja, apresenta melhores desfechos com menor custo total de tratamento, sob a perspectiva do sistema suplementar de saúde no Brasil.

Objective: The objective of this study is to compare the costs and outcomes of Continuous Renal Replacement Therapy (CRRT) versus Intermittent Hemodialysis (IRRT) in patients with acute kidney injury from the perspective of the private healthcare system in Brazil. Methods: An analytical decision model was developed based on the clinical results found in the Ethgen et al., 2015 study. Our study followed the CHEERS (Consolidated Health Economic Evaluation Reporting Standards) to report economic valuation. When acute kidney injury occurs in the ICU, patients are initiated in CRRT or IRRT. It was assumed that the length of hospital stay and ICU are the same for both modalities. The model assumes that once patients become dialysis dependent they do not recover their kidney function and remain on dialysis or die. The study horizon was 1 year, 5 years (base-case) and 20 years. Only direct costs to the private system were considered. The clinical outcomes (utilities) are from the Klarenbach & Manns, 2009 study. According to the Brazilian guidelines for health technology assessment, costs and outcomes were discounted at a rate of 5% per year with a sensitivity analysis in the range of 0% to 10% per year. In addition, two sensitivity analyzes were performed: a one-way, which generated a tornado diagram, and a two-way deterministic one considering the two key parameters that differentiate CRRT from IRRT: the daily implementation cost difference and the cumulative risk of dialysis dependence. We ran both analyzes with the time horizon of 1 year, 5 years and lifetime. According to local practices, we used the threshold of 3 times per capita GDP, that is, R $ 84,741 (3 x R$ 28,247) as the threshold for cost-effectiveness. Results: When we compare CRRT to IRRT for the initial treatment of acute kidney injury, CRRT is dominant vs. IRRT from 18 months of treatment. Based our assumptions, the cohort of patients initially treated with CRRT had better clinical outcomes (QALYs ­ Quality Adjusted Life Year) and lower total costs of treatment. Patients treated with CRRT are more likely to recover renal function. Conclusion: The results suggest that CRRT when compared to IRRT can be considered a dominant therapy, that is, it offers better outcomes and lower total treatment costs, under the perspective of the private healthcare system in Brazil.

Thickness dependence of amplified spontaneous emission in low-absorbing organic waveguides.

The effect of varying film thickness (h) on the amplified spontaneous emission (ASE) properties of 0.5 wt.% perylenediimide-doped polystyrene waveguides is reported. The threshold dependence on h, not previously investigated in detail, is analyzed in terms of the film absorption and photoluminescence, the confinement of the fundamental waveguide mode (TE0), and the presence of high-order modes. For h<400 nm and down to 150 nm, the ASE wavelength blueshifts, while the linewidth and threshold increase. The detrimental ASE operation in very thin films is due to the low absorption as well as to the poor confinement of the TE0 mode.

Efficient organic distributed feedback lasers with imprinted active films.

We report on the fabrication of efficient organic distributed feedback (DFB) lasers with thermally-nanoimprinted active films, emitting between 565 and 580 nm. The use of thermal-NIL has allowed, as opposed to room temperature or solvent-assisted techniques, high grating quality and excellent modulation depth. The 155°C heat exposure of the NIL process, does not significantly affect the thermal and optical properties of the active material (polystyrene films doped with a perylenediimide derivative). These devices combine a simple and low-cost preparation method with good laser characteristics, i.e. thresholds of 1 µJ/pulse, single-mode emission with linewidths below 0.2 nm and photostability half-lives of ~ 105 pump pulses under ambient conditions. In comparison to more standard DFBs with gratings on the substrate, their fabrication is much easier, while they show a similar laser performance.