Molecular Dynamics Study of the Green Solvent Polyethylene Glycol with Water Impurities.

Polyethylene glycol (PEG) is one of the environmentally benign solvent options for green chemistry. It readily absorbs water when exposed to the atmosphere. The Molecular Dynamics (MD) simulations of PEG200, a commercial mixture of low molecular weight polyethyelene glycol oligomers, as well as di-, tetra-, and hexaethylene glycol are presented to study the effect of added water impurities up to a weight fraction of 0.020, which covers the typical range of water impurities due to water absorption from the atmosphere. Each system was simulated a total of four times using different combinations of two force fields for the water (SPC/E and TIP4P/2005) and two force fields for the PEG and oligomer (OPLS-AA and modified OPLS-AA). The observed trends in the effects of water addition were qualitatively quite robust with respect to these force field combinations and showed that the water does not aggregate but forms hydrogen bonds at most between two water molecules. In general, the added water causes overall either no or very small and nuanced effects in the simulation results. Specifically, the obtained water RDFs are mostly identical regardless of the water content. The added water reduces oligomer hydrogen bonding interactions overall as it competes and forms hydrogen bonds with the oligomers. The loss of intramolecular oligomer hydrogen bonding is in part compensated by oligomers switching from inter- to intramolecular hydrogen bonding. The interplay of the competing hydrogen bonding interactions leads to the presence of shallow extrema with respect to the water weight fraction dependencies for densities, viscosities, and self-diffusion coefficients, in contrast to experimental measurements, which show monotonous dependencies. However, these trends are very small in magnitude and thus confirm the experimentally observed insensitivity of these physical properties to the presence of water impurities.

Structures and Dynamics of Complex Guest Molecules in Confinement, Revealed by Solid-State NMR, Molecular Dynamics, and Calorimetry.

This review gives an overview of current trends in the investigation of confined molecules such as water, small and higher alcohols, carbonic acids, ethylene glycol, and non-ionic surfactants, such as polyethylene glycol or Triton-X, as guest molecules in neat and functionalized mesoporous silica materials employing solid-state NMR spectroscopy, supported by calorimetry and molecular dynamics simulations. The combination of steric interactions, hydrogen bonds, and hydrophobic and hydrophilic interactions results in a fascinating phase behavior in the confinement. Combining solid-state NMR and relaxometry, DNP hyperpolarization, molecular dynamics simulations, and general physicochemical techniques, it is possible to monitor these confined molecules and gain deep insights into this phase behavior and the underlying molecular arrangements. In many cases, the competition between hydrogen bonding and electrostatic interactions between polar and non-polar moieties of the guests and the host leads to the formation of ordered structures, despite the cramped surroundings inside the pores.

Six-Month Outcomes Correlate with 10-Year Outcomes Following Hip Arthroscopy for Femoroacetabular Impingement Syndrome.

PURPOSE: To identify whether 6-month outcomes following hip arthroscopy for FAIS correlate with outcomes at minimum 10-year follow-up. METHODS: Patients who underwent primary hip arthroscopy for FAIS from 2012-2013 were reviewed and included if they had 6-month and minimum 10-year follow-up. Patient-reported outcome (PRO) measures included Hip Outcome Score Activities of Daily Living (HOS-ADL) and Sports-Specific (HOS-SS) subscales, modified Harris Hip Score (mHHS), and Visual Analog Scales for Pain (VAS-P) and Satisfaction (VAS-S). Six-month and 10-year outcome scores were compared and the relationships between 6-month and 1-, 2-, 5-, and 10-year outcome scores were analyzed using Pearson correlation coefficients (r). 6-month scores and clinically significant outcome (CSO) achievement were then compared to 10-year CSO achievement and reoperations, including revision hip arthroscopy and total hip arthroplasty (THA) conversion, using logistic regressions and Fisher's exact tests. RESULTS: Sixty patients (60.0% female, age: 36.0±12.2 years) were included. mHHS, VAS-P, and VAS-S significantly improved from 6-month to 10-year follow-up (p≤0.021), while HOS-ADL and HOS-SS did not (p≥0.072). There were significant correlations between 6-month and 10-year scores for HOS-ADL (r=0.505), HOS-SS (r=0.592), and mHHS (r=0.362, p≤0.022 for all), as well as significant correlations between 6-month and 1-, 2-, and 5-year scores (p<0.014, for all). 6-month HOS-ADL, HOS-SS, and mHHS were all significantly associated with their respective 10-year PASS achievement (p≤0.044). Furthermore, 6-month HOS-ADL and mHHS were significantly associated with THA conversion (p≤0.041). Comparable 6-month and 10-year minimal clinically important difference (96.5% vs. 97.8%, p=1.000) and patient acceptable symptom state (85.2% vs. 87.5%, p=1.000) achievement for any PRO was observed. CONCLUSION: Following hip arthroscopy for FAIS, patients' 6-month HOS-ADL and mHHS scores were significantly associated with their 10-year PROs, PASS achievement, and THA conversion; although, correlation strengths decreased with increasing time from surgery. LEVEL OF EVIDENCE: IV, case series.

Hip Arthroscopy Patients with Lower Back Pain Show Delayed Clinical Improvement and Inferior Time-Dependent Survivorship: A Propensity Matched Study at Mid-Term Follow-Up.

PURPOSE: To evaluate patient-reported outcomes (PROs) and survivorship at mid-term follow-up after hip arthroscopy (HA) for femoroacetabular impingement syndrome (FAIS) in patients with and without preoperative lower back pain (LBP). METHODS: Patients with self-endorsed preoperative LBP who underwent HA for FAIS with mid-term follow-up were identified and propensity matched 1:1 to patients without back pain by age, sex, and body mass index. PROs collected preoperatively and at postoperative years 1, 2, and 5 included: Hip Outcome Score Activities of Daily Living (HOS-ADL) and Sports Subscale (HOS-SS), International Hip Outcome Score 12 (iHOT-12), modified Harris Hip Score (mHHS), Visual Analog Scale (VAS) for Pain. Achievement of minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) were compared. Survivorship was compared with Kaplan-Meier analysis. RESULTS: 119 patients with LBP were matched to 119 patients without LBP. Group demographic factors were as follows, age (37.4±11.9 years vs 37.6±12.6, p=0.880), sex (64.4% female vs 67.7%, p=0.796), and BMI (25.3±5.1 kg/m2 vs 25.3±5.4, p=0.930). Average follow-up duration was 6.0 ± 1.9 years. LBP patients showed similar preoperative PROs, yet lower 1-year scores for all PROs (p ≤ 0.044). At final follow-up, similar PROs were shown between groups (p ≥ 0.196). LBP and non-LBP patients had similar MCID achievement for HOS-ADL (59.3%vs.63.1%,p=0.640), HOS-SS (73.9%vs.70.8%,p=0.710), mHHS (66.7%vs.73.4%, p=-.544), iHOT-12 (85.1%vs.79.4%,p=0.500), and VAS-Pain (75.6%vs.69.9%,p=0.490). Groups also had similar PASS achievement for HOS-ADL (63.5%vs.61.3%,p=0.777), HOS-SS (57.0%vs.62.5%,p=0.461), mHHS (81.9%vs.79.1%, p=0.692), iHOT-12 (54.6%vs.61.2%,p=0.570), and VAS-Pain (51.0%vs.55.4%,p=0.570). with similar MCID (p ≥ 0.490) and PASS (p ≥ 0.386) achievement. Conversion to total hip arthroplasty occurred in 3.4% of hips with LBP and 0.8% of hips without LBP (p=0.370), Back pain patients demonstrated inferior time-dependent survivorship compared to patients without back pain on Kaplan-Meier survival analysis (p = 0.023). CONCLUSIONS: Patients undergoing primary hip arthroscopy for femoroacetabular impingement syndrome with LBP achieve comparable PROs and CSOs to patients without back pain at mid-term, despite lower 1-year PRO scores. LBP patients show inferior reoperation-free time-dependent survivorship compared to those without LBP.

Outcomes of Flexibility Sport Athletes With Borderline Hip Dysplasia After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Analysis at Minimum 2-Year Follow-up.

BACKGROUND: Hip arthroscopy has proved successful in treating femoroacetabular impingement syndrome (FAIS) in patients with and without borderline hip dysplasia (BHD). Despite a high prevalence of BHD in patients who participate in sports with high flexibility requirements, a paucity of literature evaluates the efficacy of hip arthroscopy in treating FAIS in flexibility sport athletes with BHD. PURPOSE: To compare minimum 2-year patient-reported outcomes (PROs) and achievement of clinically significant outcomes in flexibility sport athletes with BHD undergoing primary hip arthroscopy for FAIS with capsular plication with results in flexibility sport athletes without dysplasia. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Data were prospectively collected for patients undergoing primary hip arthroscopy for FAIS with BHD, defined as a lateral center-edge angle of 18° to 25°, who reported participation in a sport with a high flexibility requirement, including dance, gymnastics, figure skating, yoga, cheerleading, and martial arts, according to previous literature. These patients were matched 1:2 to flexibility sport athletes without dysplasia, controlling for age, sex, and body mass index. Preoperative and minimum 2-year postoperative PROs were collected and compared between groups. Cohort-specific minimal clinically important difference and patient acceptable symptom state achievement was compared between groups. RESULTS: In total, 52 flexibility sport athletes with BHD were matched to 104 flexibility sport athletes without BHD. Both groups showed similar sport participation (P = .874) and a similar level of competition (P = .877). Preoperative lateral center-edge angle (22.2°± 1.6° vs 31.5°± 3.9°; P < .001) and Tönnis angle (10.9°± 3.7° vs 5.8°± 4.4°; P < .001) differed between groups. Capsular plication was performed in all cases. Both groups achieved significant improvement in all PROs (P < .001) with no differences in postoperative PROs between groups (P≥ .147). High minimal clinically important difference (BHD group: 95.7%; control group: 94.8%) and patient acceptable symptom state (BHD group: 71.7%; control group: 72.2%) achievement for any PRO was observed with no differences between groups (P≥ .835). CONCLUSION: Flexibility sport athletes with BHD achieved similar outcomes as those of flexibility sport athletes without BHD after hip arthroscopy for FAIS with capsular plication.

Elastin-like Peptide as a Model for Disordered Proteins: Diffusion Behaviour in Self-Crowding Conditions.

Despite the current high interest, there is limited information on diffusion data for intrinsically disordered proteins (IDPs). This study investigates the effect of crowding on the diffusion behaviour of an elastin-like peptide (ELP), by combined pulse field gradient (PFG) and static field gradient (SFG) NMR techniques. We interpret our findings in terms of highly dynamic chain assemblies with weak interactions, resulting in ELP diffusion that is primarily governed by the viscous flow of the solvent. The diffusion behaviour of the peptide appears to resemble that of globular proteins rather than flexible linear polymers over a wide concentration range.

Gluteus Repair Yields Satisfactory Clinically Significant Outcome Achievement by 1 Year in Mostly Partial-Thickness Tears With Preoperative Hip Abduction Weakness Associated With Delayed Achievement.

PURPOSE: To define the time to achievement of clinically significant outcomes (CSOs) after primary gluteus medius and/or minimus (GM) repair and to identify factors associated with delayed CSO achievement. METHODS: Patients who underwent primary GM repair between January 2012 and June 2021 with complete preoperative, 6-month, 1-year, and 2-year Hip Outcome Score-Activities of Daily Living (HOS-ADL) were retrospectively identified. Cohort-specific minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) were calculated. The time to achievement of MCID and PASS was analyzed using Kaplan-Meier survival analysis. Median time to MCID and PASS achievement was recorded. Multivariate stepwise Cox regressions were used to identify factors associated with delayed CSO achievement. RESULTS: Fifty GM repairs were identified (age 59.4 ± 9.7 years, body mass index 27.9 ± 6.2, 94% female). Tears were grade 1 in 39 cases, grade 2 in 7 cases, and grade 3 in 4 cases. Endoscopic repair was performed in 35 cases, and open repair was performed in 15 cases. Labral debridement and repair were each performed in 15 cases. Median time to CSO achievement was 5.7 months for MCID and 11.0 months for PASS. The 2-year cumulative probability of MCID and PASS achievement was 92.7% and 66.7%, respectively. Preoperative hip abduction weakness on physical examination was associated with delayed achievement of MCID (hazard ratio 2.27, confidence interval 1.067-7.41, P = .039) and PASS (hazard ratio 3.89, confidence interval 1.341-11.283, P = .012). CONCLUSIONS: This study demonstrated that in patients undergoing repair of primarily grade 1 GM tears, most achieved MCID by 6 months, and more than one half achieved PASS by 12 months. Preoperative hip abduction weakness on physical examination was associated with delayed CSO achievement. LEVEL OF EVIDENCE: Level IV, retrospective case series.

The Promising 2-Year Performance of the Patient-Reported Outcomes Measurement Information System in Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome.

BACKGROUND: Minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) thresholds have been previously defined for the Patient-Reported Outcomes Measurement Information System (PROMIS) at 1-year follow-up in patients undergoing hip arthroscopy for femoroacetabular impingement syndrome; however, the MCID and PASS thresholds are yet to be defined for the PROMIS at 2-year follow-up. PURPOSE: (1) To establish MCID and PASS thresholds for the PROMIS Pain Interference (PROMIS-PI) and PROMIS Physical Function (PROMIS-PF) at 2-year follow-up and (2) to correlate PROMIS scores with hip-specific patient-reported outcome measure (PROM) scores. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: Patients undergoing primary hip arthroscopy for femoroacetabular impingement syndrome between August and November 2020 with preoperative and minimum 2-year postoperative data were identified. Collected scores included those for the PROMIS-PI, PROMIS-PF, Hip Outcome Score-Activities of Daily Living (HOS-ADL), Hip Outcome Score-Sports Subscale (HOS-SS), International Hip Outcome Tool-12 (iHOT-12), and visual analog scale (VAS) for pain. MCID thresholds were calculated using the distribution-based method and PASS thresholds using the anchor-based method. Pearson correlation coefficients were used to compare scores between PROMs. RESULTS: A total of 65 patients met the criteria for inclusion (72.3% female; mean age, 36.9 ± 13.5 years; mean body mass index, 26.2 ± 6.0). The mean follow-up was 25.3 ± 3.3 months. Significant preoperative to postoperative improvements were observed for all PROMs (P < .001). MCID thresholds and achievement rates were as follows: HOS-ADL, 10.1 and 75%, respectively; HOS-SS, 13.8 and 79%, respectively; iHOT-12, 14.0 and 67%, respectively; VAS pain, -13.8 and 78%, respectively; PROMIS-PI, -4.7 and 65%, respectively; and PROMIS-PF, 5.8 and 60%, respectively. PASS thresholds and achievement rates were as follows: HOS-ADL, 78.7 and 67%, respectively; HOS-SS, 76.4 and 62%, respectively; iHOT-12, 67.4 and 60%, respectively; VAS pain, 25.5 and 61%, respectively; PROMIS-PI, 57.0 and 65%, respectively; and PROMIS-PF, 45.6 and 58%, respectively. PROMIS-PI scores correlated most strongly with HOS-ADL (r = -0.836), HOS-SS (r = -0.767), and iHOT-12 (r = -0.719) scores and exhibited at least moderate correlations (r≥-0.595) with the other PROM scores. PROMIS-PF demonstrated moderate correlations with all the other PROM scores (r≥-0.586). Strong correlations were seen between the hip-specific PROM scores (r≥-0.745). CONCLUSION: This study defined 2-year MCID and PASS thresholds for the PROMIS-PI and PROMIS-PF and demonstrated moderate to strong correlations between PROMIS scores and hip-specific PROM scores.

Cartilage Defects Are Negatively Associated With Long-Term Hip Survivorship Following Contemporary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Analysis at Minimum 10-Year Follow-Up.

PURPOSE: To identify the timing and risk factors associated with secondary surgery following primary hip arthroscopy for femoroacetabular impingement syndrome (FAIS) at 10-year minimum follow-up. METHODS: A prospectively collected clinical repository was evaluated for cases of primary hip arthroscopy for FAIS between January 2012 and February 2013 with minimum 10-year follow-up. Patients who underwent secondary surgery were propensity matched 1:4 to patients who did not undergo secondary surgery, controlling for age, sex, and body mass index (BMI). The groups were compared on demographics, radiographs, intraoperative findings, operative procedures, and patient-reported outcomes. A Kaplan-Meier survivorship curve was generated. Among the reoperation-free survivors, minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) achievement were recorded for Hip Outcome Score-Activities of Daily Living (HOS-ADL), Hip Outcome Score-Sports Specific (HOS-SS) subscales, modified Harris Hip Score (mHHS), 12-item international Hip Outcome Tool (iHOT-12), and Visual Analog Scale for Pain (VAS Pain). RESULTS: Twenty-four reoperation patients (67% female; age 40.1 ± 14.3 years; BMI 27.2 ± 5.5) were matched to 96 reoperation-free patients (62% female; age 37.0 ± 10.8 years; BMI 25.2 ± 4.7, P ≥ .111). Mean follow-up was 10.3 ± 0.2 years. No preoperative demographic differences were found between groups. The reoperation group showed more high-grade cartilage defects on the acetabulum and femoral head (33% vs 8%, P = .004; 29% vs 7%, P = .007). A bimodal distribution of time to reoperation was evidenced independent of the secondary surgery performed. Among the reoperation-free survivors, MCID and PASS achievement was as follows: HOS-ADL (69.1%, 62.1%), HOS-SS (69.9%, 74.4%), mHHS (73.3%, 58.1%), iHOT-12 (n/a, 63.8%), and VAS-Pain (80.2%, 62.6%). CONCLUSIONS: Patients requiring reoperation following primary hip arthroscopy for FAIS demonstrated more severe cartilage defects and a bimodal distribution of time to reoperation. LEVEL OF EVIDENCE: Level III, retrospective comparative case series.

Ice-Water Equilibrium in Nanoscale Confinement.

We show that 2D ^{2}H NMR spectra enable valuable insights into the nature of an ice-water equilibrium in nanoscale confinement, which extends over a broad temperature range. In particular, 2D ^{2}H NMR line-shape analysis allows us to determine the timescale on which the coexisting ice and water phases exchange molecules. For D_{2}O in a silica nanopore with a diameter of 5.4 nm, we find that the residence time of a water molecule in either phase is characterized by an NMR exchange time of τ_{X}=5.7 ms at 220 K. Thus, the ice-water equilibrium is highly dynamic, which is an important aspect for an understanding of deeply cooled confined and, possibly, bulk waters.

Ultrafast Proton Conduction in an Aqueous Electrolyte Confined in Adamantane-like Micropores of a Sulfonated, Aromatic Framework.

Sulfonated, cross-linked porous polymers are promising frameworks for aqueous high-performance electrolyte-host systems for electrochemical energy storage and conversion. The systems offer high proton conductivities, excellent chemical and mechanical stabilities, and straightforward water management. However, little is known about mass transport mechanisms in such nanostructured hosts. We report on the synthesis and postsynthetic sulfonation of an aromatic framework (SPAF-2) with a 3D-interconnected nanoporosity and varying sulfonation degrees. Water adsorption produces the system SPAF-2H20. It features proton exchange capacities up to 6 mequiv g-1 and exceptional proton conductivities of about 1 S cm-1. Two contributions are essential for the highly efficient transport. First, the nanometer-sized pores link the charge transport to the diffusion of adsorbed water molecules, which is almost as fast as bulk water. Second, continuous exchange between interface-bound and mobile species enhances the conductivities at elevated temperatures. SPAF-2H20 showcases how to tailor nanostructured electrolyte-host systems with liquid-like conductivities.

Transport Mechanism in Nafion Revealed by Detailed Comparison of 1H and 17O Nuclear Magnetic Resonance Diffusion Coefficients.

We use 1H and 17O NMR static field gradient diffusometry to measure self-diffusion coefficients of protons (DH) and oxygens (DO) in Nafion 212 with various hydration levels (λ = 4-18). For all samples and both nuclei, we obtain activation energies (Ea) of ≈0.19 eV. Analyzing the hydration-level dependence of DH and DO, we find DO/DH ≈ 1 at λ ≈ 18, resembling the situation in bulk water, while oxygen diffusion becomes faster than proton diffusion when the water content is decreased, leading to DO/DH ≈ 1.2 at λ ≈ 4. A comparison with literature data for acidic bulk solutions implies that faster oxygen than proton diffusion results from the existence of the polymer framework. To rationalize the observed ratios DO/DH ≥ 1, we consider a bimodal dynamical model in which the interactions of H+(H2O)m ions with neighboring SO3- groups lead to slower water dynamics in the vicinity of the polymer framework than in the center of the water nanochannels.

Comparative Analysis of Engineering Carbonation Model Extensions to Account for Pre-Existing Cracks.

Cracks in reinforced concrete structures can accelerate the local depassivation of reinforcement due to carbonation. Different approaches have been proposed to account for pre-existing cracks within engineering models to predict the carbonation depth. In this study, we provide a detailed comparative analysis of different extensions available for the fib carbonation model to account for cracks, viz., crack influence factor (CIF) approaches, a diffusion-based model and the crack depth adaption. The model extensions are first validated against a dataset of lab data collected from the literature and additional experiments performed as the part of this study. The CIF approaches achieved the highest accuracy for the carbonation depth prediction when compared against lab data. The diffusion-based model was inaccurate for low CO2 concentrations. The crack depth adaption provides overly conservative results. No model was found to be best performing, and large scatter was observed between predicted and experimental values. This emphasizes the need for more detailed multi-physics-based models to achieve accurate predictions. For further comparison, service life predictions were conducted for two structural scales, viz., the whole structure and the cracked area. It is concluded that the choice of model extension and the structural scale of analysis have a large influence on predicted probability of failure.

2H NMR studies on the dynamics of supercooled water in a metal-organic framework.

We use 2H nuclear magnetic resonance (NMR) to study water (D2O) reorientation and diffusion in the metal-organic framework MFU-4l, which features a regular three-dimensional network of nearly spherical pores with diameters of 1.2 and 1.9 nm. We observe that the rotational correlation times follow Vogel-Fulcher-Tammann and Arrhenius (Ea = 0.48 eV) relations above ∼225 K and below ∼170 K, respectively, whereas the temperature dependence continuously evolves from one to the other behavior in the broad crossover zone in between. In the common temperature range, the present NMR results are fully consistent with previous broadband dielectric spectroscopy (BDS) data on water (H2O) in a very similar framework. Several of our observations, e.g., rotational-translational coupling, indicate that a bulk-like structural (α) relaxation is observed above the crossover region. When cooling through the crossover zone, a quasi-isotropic reorientation mechanism is retained, while 2H spin-lattice relaxation evolves from exponential to nonexponential, implying that the water dynamics probed at low temperatures does no longer fully restore ergodicity on the time scale of this experiment. We discuss that the latter effect may result from bulk-like and/or confinement-imposed spatially heterogeneous water properties. Comparison with previous NMR and BDS results for water in other confinements reveals that, for confinement sizes around 2 nm, water reorientation depends more on the pore diameter than on the pore chemistry, while water diffusion is strongly affected by the connectivity and topology of the pores.

The Nature of the Low-Temperature Crossover of Water in Hard Confinement.

The dynamics of water confined in mesoporous MIP (2-3 nm pores in size) with silica gel (secondary silica; further, the abbreviation SG will be used) and MAP (10-35 nm pores in size) without SG borosilicate glasses have been studied by broadband dielectric spectroscopy (BDS), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). MIP samples contain secondary silica inside the pores and provide a confinement size of about 2-3 nm, whereas MAP samples are free of secondary silica and provide a confinement size of about 10-35 nm. It is shown by BDS and NMR techniques that water exhibits a dynamic crossover of around 180 K when it is confined in MIP samples. By contrast, water confined in larger pores (MAP) does not exhibit any changes in its relaxation behavior. It is also shown that the crossover temperature depends on the hydration level (the higher the hydration level, the lower the crossover temperature). Below the crossover temperature, we find that water reorientation is isotropic (NMR) and that the temperature-dependent dielectric relaxation strength (BDS) follows the tendency expected for a solid-like material. In contrast, water reorientation is related to long-range diffusion above the crossover temperature, and the dielectric relaxation strength follows the tendency expected for a liquid-like material. Furthermore, the calorimetric results are compatible with crossing a glass transition near 180 K. Finally, the results are discussed within the Gibbs-Thomson model. In this framework, the crossover could be related to ice crystals melting.

Dynamical Susceptibilities of Confined Water from Room Temperature to the Glass Transition.

We confine water to narrow silica pores, where crystallization is suppressed, and determine the dynamical susceptibilities of the liquid from room temperature down to the glass transition by combining broadband dielectric spectroscopy (BDS) with 1H and 2H nuclear magnetic resonance (NMR), in particular, by establishing NMR field-cycling relaxometry. For the correlation times, derivative analysis reveals Vogel-Fulcher-Tammann and Arrhenius regimes at T ≥ 215 K and T ≤ 160 K, respectively, which are separated by a broad crossover region. The continuous transition in the temperature dependence is accompanied by a gradual change from asymmetric high-temperature shapes of the dynamical susceptibilities to symmetric low-temperature ones and by a steady decrease of the dielectric relaxation strength. In the Arrhenius regime (Ea = 0.48 eV) at T ≤ 160 K, 2D 2H NMR spectra reveal quasi-isotropic water reorientation. We rationalize these results in terms of a crossover to an interface-affected, noncooperative relaxation involving both rotational and translational motions.

Systematic Experimental Investigation into the Determination of Micromechanical Properties of Hardened Cement Paste Using Nanoindentation-Opportunities and Limitations.

The nanoindentation technique is already widely applied in the mechanical characterization of the microstructure of thin films with respect to different materials. Generally, by means of nanoindentation, the hardness and the elastic modulus of materials can be determined with high precision. The focus of these analyses is usually on the materials from the metal, ceramic, and plastics processing industry. The application of nanoindentation in construction science, especially in concrete technology, is a relatively new field of investigation. This study deals with the basic application of nanoindentation for the mechanical characterization of hardened cement paste. In particular, the effects of sample preparation and the selection of the nanoindentation measurement parameters on the obtained results are the main subjects of this investigation. The results re intended to show the opportunities and limitations of analyzing a heterogeneous material such as hardened cement paste. The findings are used to assess the suitability of the nanoindentation method for investigating durability-related damage (e.g., due to freeze-thaw or alkali-silica reaction) in concrete.

On the Behavior of the Ethylene Glycol Components of Polydisperse Polyethylene Glycol PEG200.

Molecular dynamics (MD) simulations are reported for [polyethylene glycol (PEG)200], a polydisperse mixture of ethylene glycol oligomers with an average molar weight of 200 g·mol-1. As a first step, available force fields for describing ethylene glycol oligomers were tested on how accurately they reproduced experimental properties. They were found to all fall short on either reproducing density, a static property, or the self-diffusion coefficient, a dynamic property. Discrepancies with the experimental data increased with the increasing size of the tested ethylene glycol oligomer. From the available force fields, the optimized potential for liquid simulation (OPLS) force field was used to further investigate which adjustments to the force field would improve the agreement of simulated physical properties with experimental ones. Two parameters were identified and adjusted, the (HO)-C-C-O proper dihedral potential and the polarity of the hydroxy group. The parameter adjustments depended on the size of the ethylene glycol oligomer. Next, PEG200 was simulated with the OPLS force field with and without modifications to inspect their effects on the simulation results. The modifications to the OPLS force field significantly decreased hydrogen bonding overall and increased the propensity of intramolecular hydrogen bond formation at the cost of intermolecular hydrogen bond formation. Moreover, some of the tri- and more so tetraethylene glycol formed intramolecular hydrogen bonds between the hydroxy end groups while still maintaining strong intramolecular interactions with the ether oxygen atoms. These observations allowed the interpretation of the obtained RDFs as well as structural properties such as the average end-to-end distances and the average radii of gyration. The MD simulations with and without the modifications showed no evidence of preferential association of like-oligomers to form clusters nor any evidence of long-range ordering such as a side-by-side stacking of ethylene glycol oligomers. Instead, the simulation results support the picture of PEG200 being a random mixture of its ethylene glycol oligomer components. Finally, additional MD simulations of a binary mixture of tri-and hexaethylene glycol with the same average molar weight as PEG200 revealed very similar structural and physical properties as for PEG200.

Three-dimensional close-to-substrate trajectories of magnetic microparticles in dynamically changing magnetic field landscapes.

The transport of magnetic particles (MPs) by dynamic magnetic field landscapes (MFLs) using magnetically patterned substrates is promising for the development of Lab-on-a-chip (LOC) systems. The inherent close-to-substrate MP motion is sensitive to changing particle-substrate interactions. Thus, the detection of a modified particle-substrate separation distance caused by surface binding of an analyte is expected to be a promising probe in analytics and diagnostics. Here, we present an essential prerequisite for such an application, namely the label-free quantitative experimental determination of the three-dimensional trajectories of superparamagnetic particles (SPPs) transported by a dynamically changing MFL. The evaluation of defocused SPP images from optical bright-field microscopy revealed a "hopping"-like motion of the magnetic particles, previously predicted by theory, additionally allowing a quantification of maximum jump heights. As our findings pave the way towards precise determination of particle-substrate separations, they bear deep implications for future LOC detection schemes using only optical microscopy.

Single-Incision Laparoscopic Appendectomy Using Standard 5 mm Trocars: Single Pediatric Center Experience.

Purpose: Single-incision laparoscopic appendectomy (SILA) for the treatment of appendicitis has been documented. Typically, SILA requires the use of specialized ports, instruments, and materials. The SILA technique at our institution utilizes the same instrumentation as the conventional laparoscopic approach (CLA), thus obviating the need for these specialized products. This study aims to further demonstrate the noninferiority of our SILA technique for the treatment of uncomplicated appendicitis. Materials and Methods: This is a single-institution retrospective review of patients who underwent SILA from 2011 to 2020 to treat uncomplicated appendicitis. Outcomes including demographics, operative time, length of stay (LOS), and common postsurgical complications were evaluated. These SILA cases were matched with up to 3 CLA controls based on age, gender, and weight utilizing the Greedy match method. Patients with an operative diagnosis of perforated appendicitis were excluded. Results: A total of 137 patients underwent SILA at a single institution. A total of 128 patients were in the final cohort after excluding perforated appendicitis. Mean age was 11.9 years. Case-control matching was conducted with 349 controls included. Between cases and controls, SILA had shorter operative time (27.2 minutes versus 43.7 minutes, P < .001) with no difference in mean LOS (42.4 hours versus 42.4 hours, P = .88). There was no difference in complication rate (5.4% versus 8.5%, P = .06). There was no difference in readmission rate (0.8% versus 3.4%, P = .108). Conclusion: These data suggest that for appropriately selected patients, our SILA technique is noninferior to CLA with shortened operative time.