Synthetic chemists have developed robust methods to synthesize discrete molecules, linear and branched polymers, and disordered cross-linked networks. However, two-dimensional polymers (2DPs) ...prepared from designed monomers have been long missing from these capabilities, both as objects of chemical synthesis and in nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization of covalently linked macromolecular sheets. Here we review 2DPs and 2D polymerization methods. Three predominant 2D polymerization strategies have emerged to date, which produce 2DPs either as monolayers or multilayer assemblies. We discuss the fundamental understanding and scope of each of these approaches, including: the bond-forming reactions used, the synthetic diversity of 2DPs prepared, their multilayer stacking behaviors, nanoscale and mesoscale structures, and macroscale morphologies. Additionally, we describe the analytical tools currently available to characterize 2DPs in their various isolated forms. Finally, we review emergent 2DP properties and the potential applications of planar macromolecules. Throughout, we highlight achievements in 2D polymerization and identify opportunities for continued study.
To perform a meta-analysis of the current evidence in the literature comparing arthroscopic Bankart repair versus conservative management for first-time anterior shoulder dislocation.
A literature ...search of the MEDLINE, Embase, and Cochrane Library databases was performed based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. Prospective studies comparing arthroscopic Bankart repair versus conservative management as treatment for first-time anterior shoulder dislocation were included. Recurrence, further treatment, and return to play were compared, with all statistical analysis performed using Review Manager, version 5.3. P < .05 was considered statistically significant.
Ten prospective studies with 569 patients were included. Arthroscopic Bankart repair resulted in a lower rate of total recurrent instability (9.7% vs 67.4, I2 = 0, P < .0001) and further surgical treatment for anterior shoulder instability (5.9% vs 46.7%, I2 = 0, P < .0001). Additionally, arthroscopic Bankart repair resulted in a higher rate of return to play (92.8% vs 80.8%, I2 = 0, P = .002).
Arthroscopic Bankart repair resulted in a 7-fold lower recurrence rate and a higher rate of return to play than conservative management. Thus, arthroscopic Bankart repair may be advisable to perform routinely in patients with first-time dislocation who participate in sports.
Level II, systematic review of Level I and II studies.
Purpose
The purpose of the current study was to evaluate the short-term results of meniscal root repair surgery, assessing clinical and radiographic outcomes, utilizing MRI to assess root healing and ...extent of post-operative extrusion.
Methods
This was a single-center, retrospective study evaluating patients who had undergone a medial meniscus posterior root repair using a transtibial pullout technique with two locking cinch sutures. Demographic data were collected from patient charts. Clinical outcomes were assessed with pre- and post-operative IKDC and Lysholm scores. Pre-op scores were taken at the patients’ initial clinical visit, mean 1.55 months prior to surgery (± 1.8 months, min 0.3, max 7.3). Radiographic outcomes were assessed with MRI evaluation of root healing, meniscal extrusion, and cartilage degeneration using ICRS criteria. Tunnel placement was evaluated and compared to the anatomic footprint.
Results
Eighteen patients (47.2 years ± 11.9) were evaluated at mean follow-up of 24.9 months (± 7.2, min 18.4, max 35.6). The IKDC score significantly increased from 45.9 (± 12.6) pre-operatively to 76.8 (± 14.7) post-operatively (
p
< 0.001). Lysholm scores also increased from 50.9 (± 7.11) to 87.1 (± 9.8) (
p
< 0.001). Mean tunnel placement was 5.3 mm (± 3.5, range 0–11.8) away from the anatomic footprint. Mean extrusion increased from 4.74 mm (± 1.7) pre-operatively to 5.98 (± 2.8) post-operatively (
p
< 0.02). No patients with > 3 mm of extrusion on pre-operative MRI had < 3 mm of extrusion on post-operative MRI. Both medial femoral condyle and medial tibial plateau ICRS grades worsened significantly (
p
< 0.02 and
p
< 0.01, respectively). On MRI, one root appeared completely healed, 16 partially healed, and one not healed.
Conclusion
Patients treated with the transtibial suture pull-out technique with two locking cinch sutures had improved clinical outcomes, but only partial healing in the majority of cases, increased extrusion, and progression of medial compartment cartilage defect grade on follow-up MRI. Patients should be counseled that although clinical outcomes in the short term may be optimistic, long-term outcomes regarding progression to degenerative arthritis may not be as predictable.
Clinical level of evidence
III.
A more robust mechanistic understanding of imine-linked two-dimensional covalent organic frameworks (2D COFs) is needed to improve their crystalline domain sizes and to control their morphology, both ...of which are necessary to fully realize their application potential. Here, we present evidence that 2D imine-linked COFs rapidly polymerize as crystalline sheets that subsequently reorganize to form stacked structures. Primarily, this study focuses on the first few minutes of 1,3,5-tris(4-aminophenyl)benzene and terephthaldehyde polymerization, which yields an imine-linked 2D COF. In situ X-ray diffraction and thorough characterization of solids obtained using gentler isolation and activation methods than have typically been used in the literature indicate that periodic imine-linked 2D structures form within 60 s, which then form more ordered stacked structures over the course of several hours. This stacking process imparts improved stability toward the isolation process relative to that of the early stage materials, which likely obfuscated previous mechanistic conclusions regarding 2D polymerization that were based on products isolated using harsh activation methods. This revised mechanistic picture has useful implications; the 2D COF layers isolated at very short reaction times are easily exfoliated, as observed in this work using high-resolution transmission electron microscopy and atomic force microscopy. These results suggest improved control of imine-linked 2D COF formation can be obtained through manipulation of the polymerization conditions and interlayer interactions. Qualitatively similar results were obtained for analogous materials obtained from 2,5-di(alkoxy)terephthaldehyde derivatives, except for the COF with the longest alkoxy chains examined (OC12H25), which, although shown by in situ X-ray diffraction to be highly crystalline in the reaction mixture, is much less crystalline when isolated than the other COFs examined, likely due to the more severe steric impact of the dodecyloxy functionality on the stacking process.
Homogeneous two-dimensional (2D) polymerization is a poorly understood process in which topologically planar monomers react to form planar macromolecules, often termed 2D covalent organic frameworks ...(COFs). While these COFs have traditionally been limited to weakly crystalline aggregated powders, they were recently grown as micron-sized single crystals by temporally resolving the growth and nucleation processes. Here, we present a quantitative analysis of the nucleation and growth rates of 2D COFs via kinetic Monte Carlo (KMC) simulations using COF-5 as an example, which show that nucleation and growth have second-order and first-order dependences on monomer concentration, respectively. The computational results were confirmed experimentally by systematic measurements of COF nucleation and growth rates performed via in situ X-ray scattering, which validated the respective monomer concentration dependencies of the nucleation and elongation processes. A major consequence is that there exists a threshold monomer concentration below which growth dominates over nucleation. Our computational and experimental findings rationalize recent empirical observations that, in the formation of 2D COF single crystals, growth dominates over nucleation when monomers are added slowly, so as to limit their concentrations. This mechanistic understanding of the nucleation and growth processes will inform the rational control of polymerization in two dimensions and ultimately enable access to high-quality samples of designed two-dimensional polymers.
Ullmann-type C–N coupling reactions represent an important alternative to well-established Pd-catalyzed approaches due to the differing reactivity and the lower cost of Cu. While the design of ...anionic Cu ligands, particularly those by Ma, has enabled the coupling of various classes of aryl halides and alkyl amines, most methods require conditions that can limit their utility on complex substrates. Herein, we disclose the development of anionic N 1,N 2-diarylbenzene-1,2-diamine ligands that promote the Cu-catalyzed amination of aryl bromides under mild conditions. Guided by DFT calculations, these ligands were designed to (1) increase the electron density on Cu, thereby increasing the rate of oxidative addition of aryl bromides, and (2) stabilize the active anionic CuI complex via a π-interaction. Under optimized conditions, structurally diverse aryl and heteroaryl bromides and a broad range of alkyl amine nucleophiles, including pharmaceuticals bearing multiple functional groups, were efficiently coupled at room temperature. Combined computational and experimental studies support a mechanism of C–N bond formation that follows a catalytic cycle akin to the well-explored Pd-catalyzed variants. Modification of the ligand structure to include a naphthyl residue resulted in a lower energy barrier to oxidative addition, providing a 30-fold rate increase relative to what is seen with other ligands. Collectively, these results establish a new class of anionic ligands for Cu-catalyzed C–N couplings, which we anticipate may be extended to other Cu-catalyzed C–heteroatom and C–C bond-forming reactions.
Background Decision-making studies show that response selection is influenced by the “effort cost” associated with response alternatives. These effort-cost calculations seem to be mediated by a ...distributed neural circuit including the anterior cingulate cortex and subcortical targets of dopamine neurons. On the basis of evidence of dysfunction in these systems in schizophrenia (SZ), we examined whether effort-cost computations were impaired in SZ patients and whether these deficits were associated with negative symptoms. Methods Effort-cost decision-making performance was evaluated in 44 patients with SZ and 36 demographically matched control subjects. Subjects performed a computerized task where they were presented with a series of 30 trials in which they could choose between making 20 button presses for $1 or 100 button presses for higher amounts (varying from $3 to $7 across trials). Probability of reward receipt was also manipulated to determine whether certain (100%) or uncertain (50%) reward affected effort-based decision-making. Results Patients were less likely than control subjects to select the high-effort response alternative during the 100% probability condition, particularly when the value payoff was highest (i.e., $6 and $7). Patients were also less likely to select the high-effort option on trials after reward in the 50% probability condition. Furthermore, these impairments in effort-cost computations were greatest among patients with elevated negative symptoms. There was no association with haloperidol equivalent dosage. Conclusions The motivational impairments of SZ might be associated with abnormalities in estimating the “cost” of effortful behavior. This increased effort cost might undermine volition.
Transgenic down-regulation of the Pt4CL1 gene family encoding 4-coumarate:coenzyme A ligase (4CL) has been reported as a means for reducing lignin content in cell walls and increasing overall growth ...rates, thereby improving feedstock quality for paper and bioethanol production. Using hybrid poplar (Populus tremula × Populus alba), we applied this strategy and examined field-grown transformants for both effects on wood biochemistry and tree productivity. The reductions in lignin contents obtained correlated well with 4CL RNA expression, with a sharp decrease in lignin amount being observed for RNA expression below approximately 50% of the nontransgenic control. Relatively small lignin reductions of approximately 10% were associated with reduced productivity, decreased wood syringyl/guaiacyl lignin monomer ratios, and a small increase in the level of incorporation of H-monomers (p-hydroxyphenyl) into cell walls. Transgenic events with less than approximately 50% 4CL RNA expression were characterized by patches of reddish-brown discolored wood that had approximately twice the extractive content of controls (largely complex polyphenolics). There was no evidence that substantially reduced lignin contents increased growth rates or saccharification potential. Our results suggest that the capacity for lignin reduction is limited; below a threshold, large changes in wood chemistry and plant metabolism were observed that adversely affected productivity and potential ethanol yield. They also underline the importance of field studies to obtain physiologically meaningful results and to support technology development with transgenic trees.
Background:
The minimal clinically important difference (MCID) is a term synonymous with orthopaedic clinical research over the past decade. The term represents the smallest change in a ...patient-reported outcome measure that is of genuine clinical value to patients. It has been derived in a myriad of ways in existing orthopaedic literature.
Purpose:
To describe the various modalities for deriving the MCID.
Study Design:
Narrative review; Level of evidence, 4.
Methods:
The definitions of common MCID determinations were first identified. These were then evaluated by their clinical and statistical merits and limitations.
Results:
There are 3 primary ways for determining the MCID: anchor-based analysis, distribution-based analysis, and sensitivity- and specificity-based analysis. Each has unique strengths and weaknesses with respect to its ability to evaluate the patient’s clinical status change from baseline to posttreatment. Anchor-based analyses are inherently tied to clinical status yet lack standardization. Distribution-based analyses are the opposite, with strong foundations in statistics, yet they fail to adequately address the clinical status change. Sensitivity and specificity analyses offer a compromise of the other methodologies but still rely on a somewhat arbitrarily defined global transition question.
Conclusion:
This current concepts review demonstrates the need for (1) better standardization in the establishment of MCIDs for orthopaedic patient-reported outcome measures and (2) better study design—namely, until a universally accepted MCID derivation exists, studies attempting to derive the MCID should utilize the anchor-based within-cohort design based on Food and Drug Administration recommendations. Ideally, large studies reporting the MCID as an outcome will also derive the value for their populations. It is important to consider that there may be reasonable replacements for current derivations of the MCID. As such, future research should consider an alternative threshold score with a more universal method of derivation.
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