How Subtle Changes Can Make a Difference – Reproducibility in Complex Supramolecular Systems

The desire to construct complex molecular systems is driven by the need for technological (r)evolution and our intrinsic curiosity to comprehend the origin of life. Supramolecular chemists tackle this challenge by combining covalent and noncovalent reactions leading to multicomponent systems with emerging complexity. However, this synthetic strategy often coincides with difficult preparation protocols and a narrow window of suitable conditions. Here, we report on unsuspected observations of our group that highlight the impact of subtle “irregularities” on supramolecular systems. Based on the effects of pathway complexity, minute amounts of water in organic solvents or small impurities in the supramolecular building block, we discuss potential pitfalls in the study of complex systems. This article is intended to draw attention to often overlooked details and to initiate an open discussion on the importance of reporting experimental details to increase reproducibility in supramolecular chemistry

Melting of a colloidal crystal

A melting transition for a system of hard spheres interacting by a repulsive Yukawa potential of DLVO form is studied. To find the location of the phase boundary, we propose a simple theory to calculate the free energies for the coexisting liquid and solid. The free energy for the liquid phase is approximated by a virial expansion. The free energy of the crystalline phase is calculated in the spirit of the Lenard-Jonnes and Devonshire (LJD) theory. The phase boundary is found by equating the pressures and chemical potentials of the coexisting phases. When the approximation leading to the equation of state for the liquid breakes down, the first order transition line is also obtained by applying the Lindemann criterion to the solid phase. Our results are then compared with the Monte Carlo simulations.Comment: 7 pages, Revtex (using twocolumn style), four figures and postscript file. Submitted to Physica

Assessment of disease activity in patients with rheumatoid arthritis using optical spectral transmission measurements, a non-invasive imaging technique

Objectives: In rheumatoid arthritis (RA), treat-to-target strategies require instruments for valid detection of joint inflammation. Therefore, imaging modalities are increasingly used in clinical practice. Optical spectral transmission (OST) measurements are non-invasive and fast and may therefore have benefits over existing imaging modalities. We tested whether OST could measure disease activity validly in patients with RA. Methods: In 59 patients with RA and 10 patients with arthralgia, OST, joint counts, Disease Activity Score (DAS) 28 and ultrasonography (US) were performed. Additionally, MRI was performed in patients with DAS28<2.6. We developed and validated within the same cohort an algorithm for detection of joint inflammation by OST with US as reference. Results: At the joint level, OST and US performed similarly inproximal interphalangeal-joints (area under the receiver-operating curve (AUC) of 0.79, p<0.0001) andmetacarpophalangeal joints (AUC 0.78, p<0.0001). Performance was less similar in wrists (AUC 0.62, p=0.006). On the patient level, OST correlated moderately with clinical examination (DAS28 r=0.42, p=0.001), and US scores (r=0.64, p<0.0001). Furthermore, in patients with subclinical and low disease activity, there was a correlation between OST and MRI synovitis score (RAMRIS (Rheumatoid Arthritis MRI Scoring) synovitis), r=0.52, p=0.005. Conclusions: In this pilot study, OST performed moderately in the detection of joint inflammation in patients with RA. Further studies are needed to determine the diagnostic performance in a new cohort of patients with RA

Low adherence to recommended use of neoadjuvant chemotherapy for muscle-invasive bladder cancer

Purpose: To evaluate guideline adherence and variation in the recommended use of neoadjuvant chemotherapy (NAC) and the effects of this variation on survival in patients with non-metastatic muscle-invasive bladder cancer (MIBC). Patients and methods: In this nationwide, Netherlands Cancer Registry-based study, we identified 1025 patients newly diagnosed with non-metastatic MIBC between November 2017 and November 2019 who underwent radical cystectomy. Patients with ECOG performance status 0–1 and creatinine clearance ≥ 50 mL/min/1.73 m2 were considered NAC-eligible. Interhospital variation was assessed using case-mix adjusted multilevel analysis. A Cox proportional hazards model was used to evaluate the association between hospital specific probability of using NAC and survival. All analyses were stratified by disease stage (cT2 versus cT3-4a). Results: In total, of 809 NAC-eligible patients, only 34% (n = 277) received NAC. Guideline adherence for NAC in cT2 was 26% versus 55% in cT3-4a disease. Interhospital variation was 7–57% and 31–62%, respectively. A higher hospital specific probability of NAC might be associated with a better survival, but results were not statistically significant (HRcT2 = 0.59, 95% CI 0.33–1.05 and HRcT3-4a = 0.71, 95% CI 0.25–2.04). Conclusion: Guideline adherence regarding NAC use is low and interhospital variation is large, especially for patients with cT2-disease. Although not significant, our data suggest that survival of patients diagnosed in hospitals more inclined to give NAC might be better. Further research is warranted to elucidate the underlying mechanism. As literature clearly shows the potential survival benefit of NAC in patients with cT3-4a disease, better guideline adherence might be pursued.</p

Single photon emitters based on Ni/Si related defects in single crystalline diamond

We present investigations on single Ni/Si related color centers produced via ion implantation into single crystalline type IIa CVD diamond. Testing different ion dose combinations we show that there is an upper limit for both the Ni and the Si dose 10^12/cm^2 and 10^10/cm^2 resp.) due to creation of excess fluorescent background. We demonstrate creation of Ni/Si related centers showing emission in the spectral range between 767nm and 775nm and narrow line-widths of 2nm FWHM at room temperature. Measurements of the intensity auto-correlation functions prove single-photon emission. The investigated color centers can be coarsely divided into two groups: Drawing from photon statistics and the degree of polarization in excitation and emission we find that some color centers behave as two-level, single-dipole systems whereas other centers exhibit three levels and contributions from two orthogonal dipoles. In addition, some color centers feature stable and bright emission with saturation count rates up to 78kcounts/s whereas others show fluctuating count rates and three-level blinking.Comment: 7 pages, submitted to Applied Physics B, revised versio

Dissemination of rat cytomegalovirus through infected granulocytes and monocytes in vitro and in vivo

The role of leukocytes in the in vivo dissemination of cytomegalovirus was studied in this experiment. Rat cytomegalovirus (RCMV) could be transferred to rat granulocytes and monocytes by cocultivation with RCMV-infected fibroblasts in vitro. Intravenous injection of purified infected granulocytes or monocytes resulted in a systemic infection in rats, indicating that our model is a powerful tool to gain further insight into CMV dissemination and the development of new antivirals

Carotid intima-media thickness and its associations with type 2 diabetes mellitus in South Africans

OBJECTIVES: Carotid intima-media thickness (CIMT) is a surrogate marker of subclinical atherosclerosis and a predictor of cardiovascular events. Few studies in Africa have evaluated CIMT and its associations in people with type 2 diabetes mellitus. This study measured CIMT in a sample of mainly black South African patients with type 2 diabetes mellitus, and evaluated the association of demographic and clinical risk factors with CIMT. DESIGN: Cross-sectional study. SETTING: Kafalong Hospital, a large community hospital in Pretoria that mainly serves an urban black community. SUBJECTS: Patients with type 2 diabetes mellitus. OUTCOME MEASURES: We evaluated clinical, biochemical and CIMT ultrasound measurements in a standardised fashion. RESULTS: In 185 patients, the univariate significant predictors of mean far-wall CIMT were age [beta 0.007 (standard error 0.001)], systolic blood pressure [beta 0.001 (standard error 0.000)] and inverse serum creatinine [beta -8.15 (standard error 3.23)]. Low-density lipoprotein cholesterol, apolipoprotein A-1, apolipoprotein B:A-1 ratio and apolipoprotein B:A-1 ratio > 1.2 all had p-values below 0.1, but above 0.05. Age had the largest R-squared (20%). The multivariate models did not explain more of the variation in CIMT than did age alone. CONCLUSION: Lipid parameters were related to CIMT in our study population. However, this did not reach statistical significance in this relatively small sample, and lipids added very little to the variability of CIMT compared with age alone.http://www.jemdsa.co.za/index.php/JEMDSAay201