No abstract

Understanding self-assembly is a critical step toward controlling structure at the nanometer length scale. Furthermore, small changes in nanoscale morphology can have large impacts on the performance of nanomaterial devices. In this work, we experimentally explore how the physical properties of lead sulfide (PbS) nanocrystals, such as the surface ligands and core size dispersity, affect the ability of these nanocrystals to self-assemble. We quantified the self-assembly quality by monitoring grain size and the percentage of nanocrystals with coherent alignment of their atomic planes. We found that the ensemble size dispersity plays a large role in superlattice formation and that even small improvements in size distribution led to shorter neighbor-to-neighbor distances in superlattices (more efficient packing), larger grain sizes, and increased nanocrystal alignment. Additionally, the ligand coverage on nanocrystal surfaces had a significant influence on the self-assembly, and excess precipitation steps were highly detrimental to the formation of ordered solids. We show that surface ligand length is a more flexible parameter and that high-quality superlattices can still be achieved with compact surface ligands, so long as the nanocrystal size dispersity and ligand coverage are sufficient. Lastly, we investigated several different colloidal solvents, finding toluene to provide the best ordering, and show that nanocrystal self-assembly is largely unhindered by nanocrystal age. Overall, these results guide our understanding of the underlying factors influencing nanocrystal self-assembly and provide strategies for forming well-engineered superlattices.

We develop a method for achieving scalable transmission stabilization and switching of N colliding soliton sequences in optical waveguides with broadband delayed Raman response and narrowband nonlinear gain-loss. We show that dynamics of soliton amplitudes in N -sequence transmission is described by a generalized N -dimensional predator-prey model. Stability and bifurcation analysis for the predator-prey model are used to obtain simple conditions on the physical parameters for robust transmission stabilization as well as on-off and off-on switching of M out of N soliton sequences. Numerical simulations for single-waveguide transmission with a system of N coupled nonlinear Schrödinger equations with 2 ≤ N ≤ 4 show excellent agreement with the predator-prey model's predictions and stable propagation over significantly larger distances compared with other broadband nonlinear single-waveguide systems. Moreover, stable on-off and off-on switching of multiple soliton sequences and stable multiple transmission switching events are demonstrated by the simulations. We discuss the reasons for the robustness and scalability of transmission stabilization and switching in waveguides with broadband delayed Raman response and narrowband nonlinear gain-loss, and explain their advantages compared with other broadband nonlinear waveguides.

Context Dyspnea is one of the most distressing symptoms for cancer patients. The role of high flow oxygen (HFO) and bilevel positive airway pressure (BiPAP) in the palliation of dyspnea has not been well characterized. Objectives To determine the feasibility of conducting a randomized trial of HFO and BiPAP in cancer patients, and to examine the changes in dyspnea, physiologic parameters and adverse effects with these modalities. Methods In this randomized study (ClinicalTrials.gov Identifier: NCT01518140), we assigned hospitalized patients with advanced cancer and persistent dyspnea to either HFO or BiPAP for two hours. We assessed dyspnea with a numeric rating scale (NRS) and modified Borg scale (MBS) before and after the intervention. We also documented vital signs, transcutaneous carbon dioxide and adverse effects. Results Thirty patients were enrolled (1:1 ratio) and 23 (77%) completed the assigned intervention. HFO was associated with improvements in both NRS (mean 1.9, 95% confidence interval [CI] 0.4, 3.4; P=0.02) and MBS (mean 2.1, 95% CI 0.6, 3.5; P=0.007). BiPAP also was associated with improvements in NRS (mean 3.2; 95% CI 1.3, 5.1; P=0.004) and MBS (mean 1.5, 95% CI −0.3, 3.2; P=0.13). There were no significant differences between HFO and BiPAP in dyspnea NRS (P=0.14) and MBS (P=0.47). Oxygen saturation improved with HFO (93% vs. 99%, P=0.003), and respiratory rate had a non-statistically significant decrease with both interventions (HFO -3; P=0.11; BiPAP -2, P=0.11 ). No significant adverse effects were observed. Conclusion HFO and BiPAP alleviated dyspnea, improved physiologic parameters and were safe. Our results justify larger randomized controlled trials to confirm these findings.

We study the deterministic effects of Raman-induced crosstalk in amplified wavelength division multiplexing (WDM) optical fiber transmission lines. We show that the dynamics of pulse amplitudes in an N -channel transmission system is described by an N -dimensional predator-prey model.We find the equilibrium states with non-zero amplitudes and prove their stability by obtaining the Lyapunov function. The stability is independent of the exact details of the approximation for the Raman gain curve. Furthermore, we investigate the impact of cross phase modulation and Raman self and cross frequency shifts on the dynamics and establish the stability of the equilibrium state with respect to these perturbations. Our results provide a quantitative explanation for the robustness of differential-phase-shift-keyed WDM transmission against Raman crosstalk effects.

Background and objective: It is unclear if physiologic measures are useful for assessing dyspnea. We examined the association among the subjective rating of dyspnea according to patients with advanced cancer, caregivers and nurses, and various physiologic measures. Methods: We conducted a cross-sectional survey of patients with cancer hospitalized at MD Anderson Cancer Center. We asked patients, caregivers, and nurses to assess the patients' dyspnea at the time of study enrollment independently using a numeric rating scale (0 = none, 10 = worst). Edmonton Symptom Assessment Scale (ESAS) ratings, causes of dyspnea, vitals, and Respiratory Distress Observation Scale [RDOS] ratings were collected. Results: A total of 299 patients were enrolled in the study: average age 62 (range 20-98), female 47%, lung cancer 37%, and oxygen use 57%. The median RDOS rating was 2/16 (interquartile range 1-3) and the number of potential causes was 3 (range 2-4), with pleural effusion (n = 166, 56%), pneumonia (n = 144, 48%), and lung metastasis (n = 125, 42%) being the most common. The median intensity of patients' dyspnea at the time of assessment was 3 (interquartile range 0-6) for patients, 4 (interquartile range 1-6) for caregivers, and 2 (interquartile range 0-3) for bedside nurses. Patients' expression of dyspnea correlated moderately with caregivers' (r = 0.68, p < 0.001) and nurses' (r = 0.50, p < 0.001) assessments, and weakly with RDOS (r = 0.35, p < 0.001), oxygen level (r = 0.32, p < 0.001), and the number of potential causes (r = 0.19, p = 0.001). In multivariate analysis, patients' dyspnea was only independently associated with ESAS dyspnea ( p = 0.002) and dyspnea as assessed by caregivers ( p < 0.001). Conclusion: Patients' level of dyspnea was weakly associated with physiologic measures. Caregivers' perception may be a useful surrogate for dyspnea assessment.

We study transmission stability and dynamics of pulse amplitudes in N -channel soliton-based optical waveguide systems, taking into account second-order dispersion, Kerr nonlinearity, delayed Raman response, and frequency dependent

Purpose To report quality of life (QOL)/toxicity in men treated with proton beam therapy (PBT) for localized prostate cancer and to compare outcomes between passively scattered proton therapy (PSPT) and spot-scanning proton therapy (SSPT). Methods and Materials Men with localized prostate cancer enrolled on a prospective QOL protocol with a minimum of 2 years follow-up were reviewed. Comparative groups were defined by technique (PSPT vs. SSPT). Patients completed Expanded Prostate Cancer Index Composite (EPIC) questionnaires at baseline and every 3-6 months after PBT. Clinically meaningful differences in QOL were defined as ≥0.5 × baseline standard deviation. The cumulative incidence of modified RTOG grade ≥2 GI or GU toxicity and argon plasma coagulation (APC) were determined by the Kaplan-Meier method. Results 226 men received PSPT and 65 SSPT. Both PSPT and SSPT resulted in statistically significant changes in sexual, urinary, and bowel EPIC summary scores. Only bowel summary, function, and bother resulted in clinically meaningful decrements beyond treatment completion. The decrement in bowel QOL persisted through 24-month follow-up. Cumulative grade ≥2 GU and GI toxicity at 24 months were 13.4% and 9.6%, respectively. There was one Grade 3 GI toxicity (PSPT group) and no other grade 3 or greater GI or GU toxicity. APC application was infrequent (PSPT 4.4% vs. SSPT 1.5%; p = 0.21). No statistically significant differences were appreciated between PSPT and SSPT regarding toxicity or QOL. Conclusion Both PSPT and SSPT confer low rates of grade ≥ 2 GI or GU toxicity with preservation of meaningful sexual and urinary QOL at 24 months. A modest, yet clinically meaningful, decrement in bowel QOL was seen throughout follow-up. No toxicity or QOL differences between PSPT and SSPT were identified. Long term comparative results in a larger patient cohort are warranted.