A Review of Patellar Tendinopathy in Athletes Involved in Jumping Sports.

This review article discusses the anatomy and histopathology of the patellar tendon, as well as the risk factors and common interventions for patellar tendinopathy (PT) with a view to guide clinicians in treating athletes with patellar tendon pain. PT, or jumper's knee, refers to a chronic injury to the patellar tendon that affects athletes who engage in jumping and explosive movements. The condition is characterized by degeneration and disorganization of the collagen fibers in the tendon, an increase in mucoid ground substance, and fibroblast proliferation. Risk factors for patellar tendinopathy include participation in jumping sports, a greater counter-movement jump height, and training on hard surfaces. Nonoperative treatments for patellar tendinopathy include relative rest, stretching and strengthening exercises, and correction of biomechanical abnormalities. Surgery and other procedures, such as extracorporeal shockwave therapy (ESWT) and injection therapies, may be considered for patients who do not respond to conservative measures.

Model-based investigation of the chemical phosphorus removal potential of the peroxide regenerated iron-sulfide control technology.

In this study, the potential of using peroxide regenerated iron-sulfide control (PRI-SC®) for chemical phosphorus removal utilizing the existing iron sulfide found in wastewaters was investigated in batch tests and compared in full-scale facility-wide simulations to using iron salts. PRI-SC is a combination treatment that utilizes iron salts and hydrogen peroxide in a synergetic fashion, where hydrogen peroxide is used in regenerating the spent iron salt in situ in the form of iron sulfide, yielding ferric iron and colloidal sulfur. A simplified kinetic model was developed, calibrated, and integrated into a facility-wide model to simulate the process at the full-scale. Experimental results showed that dosing hydrogen peroxide, even at doses lower than the stoichiometrically required to oxidize iron sulfide, freed, and oxidized sulfide bound ferrous iron to ferric iron, which was consequently hydrolyzed and affected phosphorus removal. Higher dosing of hydrogen peroxide did not affect change in the speciation of sulfur remaining predominantly as elemental sulfur. Simulations showed that the application of PRI-SC with supplemental ferric iron dosing was able to cut the costs of chemicals addition up to 53% while maintaining a steady-state effluent phosphate concentration below 0.01 mg/L. PRACTITIONER POINTS: The kinetic model was used to optimize ferric iron and hydrogen peroxide dosing. The developed model can be integrated in existing wastewater process simulators. Dosing hydrogen peroxide effectively oxidized ferrous iron to ferric iron. The combination of hydrogen peroxide and iron salts can reduce the chemical addition cost by 53%.

Vacuum-enhanced anaerobic fermentation: Achieving process intensification, thickening and improved hydrolysis and VFA yields in a single treatment step.

This study assessed the feasibility of a novel vacuum-enhanced anaerobic digestion technology, referred to as IntensiCarbTM (IC), under mild vacuum pressure (110 mbar), compared to a control (conventional fermenter), and evaluated the impact of the vacuum on the activities of various microbial groups. Both fermenters (test and control) were operated with mixed (50% v/v) municipal sludge at solids concentrations of 2-2.5%, pH of 7.8-8.1, 40-45 °C, a theoretical solids retention time (SRT) of 3 days with different hydraulic retention times (HRT). The intensification factor (IF) of the IC, defined as SRT/HRT, was controlled at 1.3 and 2.0. Simultaneous thickening and fermentation intensification were achieved. Compared with the control, the IC, despite the shorter HRTs, achieved 29.5 to 90.2% increase in the VFA yield (79 to 116 mg ΔVFA/ g VSS vs 61 mg ΔVFA/ g VSS), and 16.2% to 56.4% increase (280 to 377 mg ΔsCOD/ g VSS vs 241 mg ΔsCOD/ g VSS), in the hydrolysis yield. Fermentate from the IC exhibited comparable specific denitrification rates to acetate. Further, the solids-free condensate contained low nutrient concentrations, and thus was far superior to a typical centrates from dewatering as a carbon source. No adverse effects of vacuum on the activity of fermentative bacteria and methanogens were observed. This study demonstrated that the IC can be deployed as an intensification technology for both fermentation and anaerobic digestion of biosolids with the additional significant advantage, i.e. elimination of sidestream ammonia treatment requirements.

A proof-of-concept experimental study for vacuum-driven anaerobic biosolids fermentation using the IntensiCarb technology.

This study demonstrates the potential of an innovative anaerobic treatment technology for municipal biosolids (IntensiCarb), which relies on vacuum evaporation to decouple solids and hydraulic retention times (SRT and HRT). We present proof-of-concept experiments using primary sludge and thickened waste activated sludge (50-50 v/v mixture) as feed for fermentation and carbon upgrading with the IntensiCarb unit. IntensiCarb fully decoupled the HRT and SRT in continuously stirred anaerobic reactors (CSAR) to achieve two intensification factors, that is, 1.3 and 2, while keeping the SRT constant at 3 days (including in the control fermenter). The intensified CSARs were compared to a conventional control system to determine the yields of particulate hydrolysis, VFA production, and nitrogen partitioning between fermentate and condensate. The intensified CSAR operating at an intensification factor 2 achieved a 65% improvement in particulate solubilization. Almost 50% of total ammonia was extracted without pH adjustment, while carbon was retained in the fermentate. Based on these results, the IntensiCarb technology allows water resource recovery facilities to achieve a high degree of plant-wide intensification while partitioning nutrients into different streams and thickening solids. PRACTITIONER POINTS: The IntensiCarb reactor can decouple hydraulic (HRT) and solids (SRT) retention times in anaerobic systems while also increasing particulate hydrolysis and overall plant capacity. Using vacuum as driving force of the IntensiCarb technology, the system could achieve thickening, digestion, and partial dewatering in the same unit-thus eliminating the complexity of multi-stage biosolids treatment lines. The ability to partition nutrients between particulate, fermentate, and condensate assigns to the IntensiCarb unit a key role in recovery strategies for value-added products such as nitrogen, phosphorus, and carbon, which can be recovered separately and independently.

Sulfur and Phosphorus Oxyacid Radicals.

We report a computational study of the little-studied neutral bisulfite, bisulfate, dihydro-phosphite, and dihydro-phosphate radicals (HSOx•, H2POx•, x = 3,4), calling special attention to their various tautomeric structures together with pKa values estimated from the Gibbs free energies of their dissociations (at the G4 and CAM-B3LYP levels of density functional theory). The energetics of microhydration clusters with up to four water molecules for the S-based species and up to eight water molecules for the P-based species were investigated. The number of microhydrating water molecules needed to induce spontaneous de-protonation is found to correlate the acid strength of each radical. According to the computed Gibbs free reaction and activation energies, S- and P-centered radicals preferentially add to the double bond of propene (a lipid model), whereas the O-centered radical tautomers prefer H-abstraction. The likely downstream reactions of these radicals in biological media are discussed.

Dissociations of free radicals to generate protons, electrophiles or nucleophiles: role in DNA strand breaks.

The concept behind the research described in this article was that of marrying the 'soft' methods of radical generation with the effectiveness and flexibility of nucleophile/electrophile synthetic procedures. Classic studies with pulse radiolysis and laser flash photolysis had shown that free radicals could be more acidic than their closed shell counterparts. QM computations harmonised with this and helped to define which radical centres and which structural types were most effective. Radicals based on the sulfonic acid moiety and on the Meldrum's acid moiety (2,2-dimethyl-1,3-dioxane-4,6-dione) were found to be extreme examples in the superacid class. The ethyne unit could be used as a very effective spacer between the radical centre and the site of proton donation. The key factor in promoting acidity was understood to be the thermodynamic stabilisation of the conjugate anion-radicals released on deprotonation. Solvation played a key part in promoting this and theoretical microhydration studies provided notable support. A corollary was that heterolytic dissociations of free radicals to yield either electrophiles or nucleophiles were also enhanced relative to non-radical models. The most effective radical types for spontaneous releases of both these types of reagents were identified. Ethyne units were again effective as spacers. The enhancement of release of phosphate anions by adjacent radical centres was an important special case. Reactive oxygen species and also diradicals from endiyne antibiotics generate C4'-deoxyribose radicals from nucleotides. Radicals of these types spontaneously release phosphate and triphosphate and this is a contributor to DNA and RNA strand breaks.

Enhancing sludge dewaterability and phosphate removal through a novel chemical dosing strategy using ferric chloride and hydrogen peroxide.

In this study, we replicated full-scale centrifuge dewatering utilized in water resource recovery facilities (WRRFs) by using the Higgins modified centrifuge technique and demonstrated that analogous cake solid content and centrate suspended solids were attainable while applying a lower polymer dosage. Furthermore, we demonstrated a dramatic reduction in the concentration of phosphate (P) in anaerobically digested sludge (ADS) under various reaction conditions. H2 O2 was employed to convert embedded iron in ADS, in the form of FeS, to Fe (II) and Fe (III), which subsequently reacted to precipitate phosphate compounds, dropping the in situ P concentration by nearly 50%. Adding ferric chloride (220 mg/L) in ADS enhanced the P-removal to more than 80%. Finally, simultaneous dosing of Fe and H2 O2 boosted P-removal efficiency to higher than 90%. The role of Fe in strengthening the flocs and increasing the dewaterability was also substantiated by demonstrating a 2% growth in the cake solid content when ADS was conditioned with Fe + H2 O2 preceding polymer treatment. The outcome of this work confirms that a deeper understanding of centrifuge operational parameters and physico-chemical properties of wastewater sludge would result in improved performance of municipal WRRFs. PRACTITIONER POINTS: Dosing hydrogen peroxide effectively converted iron embedded in sludge from Fe (II) to Fe (III). Simultaneous dosing of iron and hydrogen peroxide boosted P removal efficiency. The role of iron in strengthening flocs and enhancing dewaterability was observed, as it increased cake solid content in centrifuged sludge. An advanced bench-scale test protocol was employed to optimize polymer dose, simultaneously reducing polymer consumption while maximizing cake solid content and centrate quality.

Should dental technicians play a greater role in the education of foundation dentists?

In some dental foundation training (DFT) practices, many generations of foundation dentists (FDs) have benefited from being encouraged to build close working relationships with dental technicians. Recent work suggests that new graduates may require additional support with the technical aspects of clinical work due to reduced clinical exposure in undergraduate education. This opinion paper therefore describes how involvement of technical colleagues in the education of FDs could provide important additional feedback on their work and draws upon the concept of 'spiral learning'. It goes on to argue that these opportunities are vital in building mutual respect and the ability to communicate effectively with members of the dental team. Ingraining this approach in FDs is important for their future careers and for the dental profession.

Free Radical Mediated Oxidative Degradation of Carotenes and Xanthophylls.

This article reviews the excited-state quenching, pro-vitamin A activity and anticarcinogenicity of carotenes and xanthophylls in relation to their chemical structures. Excited-state quenching improved with the length of the conjugated chain structure. Pro-vitamin A activity was dependent on the presence of at least one beta-ionyl ring structure. The effectiveness of carotenoids as antioxidants depended on their ability to trap peroxyl radicals with production of resonance-stabilized carotenyl radicals. The products identified from oxidations of carotenes and xanthophylls with molecular oxygen and other oxidizing agents are presented. The free radical-mediated mechanisms that have been proposed to account for the different classes of products are reviewed.

EPR Studies on the Addition of Ligated Boryl Radicals to Carbonyl Compounds.

The boron-centered radicals derived from alkenyl N-heterocyclic carbene (NHC)-boranes bearing ester substituents were recently found to ring close in 5-endo mode by addition to the oxygen atoms of the ester substituents. The inference from this was that NHC-boryl radicals might add intermolecularly to carbonyl-containing substrates. Several different NHC-boryl radicals were generated by H-atom abstraction from NHC-ligated trihydroborates. Electron paramagnetic resonance (EPR) spectroscopy proved that these did indeed add to the oxygen atoms of diaryl ketones with production of the corresponding bora-ketyl radicals. The same unusual regioselectivity of addition was observed with monoaryl ketones, but no bora-ketyls were observed with dialkyl ketones. Similarly, no bora-ketyl adduct radicals were observed with esters, even esters of benzoic acid. EPR spectroscopic evidence suggested that NHC-boryl radicals were also added to the O-atoms of aromatic aldehydes. Amine-boryl and phosphine-boryl radicals were also observed to add to the O-atom of benzophenone with production of the corresponding ketyl radicals.

Radical-Stimulated Nucleophile Release.

Experimental and computational results have shown that deprotonation was enhanced for precursors containing radical centers (RED-shift). An examination of whether the inverse heterolytic dissociations that release nucleophiles instead of electrophiles could also be stimulated by suitably sited radicals is reported in this paper. A DFT method was employed to assess the free energies of heterolytic dissociations releasing C-centered and O-centered nucleophiles. In most instances a radical adjacent to the incipient positive charge in the precursors led to significant enhancement of heterolytic dissociation, but inhibition was found in some cases. Greater enhancements were obtained with C-centered rather than O-centered radicals. Exergonic dissociations for both O- and C-centered nucleophiles could be achieved with fluorenylmethyl- and cyclohepta-2,4,6-trienylmethyl-containing precursors. Heterolytic phosphate release from ribose and deoxyribose nucleotide C4' radicals was also found to be enhanced. This provided supporting evidence of the importance of these radicals in DNA and RNA strand breaking. The effect of ethyne, ethene, and phenyl spacer units between the radical center and the incipient positive charge was examined. Evidence was obtained that the key factor promoting heterolytic dissociation was the resonance stabilization of the coreleased radical-cations.

Metastatic clear cell renal cell carcinoma to the forearm without identifiable primary renal mass.

Kidney cancer is the ninth most common malignancy in the United States. Most kidney cancers are clear cell renal cell carcinoma (RCC) and arise as solid tumors from kidney parenchyma. In the setting of metastatic disease, a primary renal tumor is usually identified, and metastases are often to lung, bone, liver, and brain. Metastatic RCC without an identifiable solid kidney tumor is exceedingly rare. We report the case of a 52 year old male with a rare cutaneous RCC metastasis without an identifiable primary renal tumor.

EPR and Preparative Studies of 5- endo Cyclizations of Radicals Derived from Alkenyl NHC-Boranes Bearing tert-Butyl Ester Substituents.

Radical H atom abstraction from a set of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two tert-butyl ester substituents was studied by EPR spectroscopy. The initial boraallyl radical intermediates rapidly ring closed onto the O atoms of their distal ester groups in 5- endo mode to yield 1,2-oxaborole radicals. Unexpectedly, two structural varieties of these radicals were identified from their EPR spectra. These proved to be two stable rotamers, in which the carbonyl group of the tert-butyl ester was oriented toward and away from the NHC ring. These rotamers were akin to the s- trans and s- cis rotamers of α,ß-unsaturated carbonyl compounds. Their stability was attributed to the quasi-allylic interaction of their unpaired electrons with the carbonyl units of their adjacent ester groups. EPR spectroscopic evidence for two rotamers of the analogous methyl ester containing NHC-oxaborole radicals was also obtained. An improved synthetic procedure for preparing rare NHC-boralactones was developed involving treatment of the alkenyl NHC-boranes with AIBN and tert-dodecanethiol.

Reflex Carbocation Release from Covalent Molecules by Endogenous Free Radicals.

Carbocations are pervasive in contemporary organic synthesis, so new and innocuous methods of making them are always desirable. A theoretical approach revealed that compounds in which radical generation takes place may release carbocations advantageously. The radical types and molecular substructures that promote this effect were identified. The best substructures were found to be 1,3-dicarbonyl compounds, particularly those based on the Meldrum's acid theme. Sulfate esters and dithiane rings could also be employed. Radicals generated on oxygen atoms or ethyne units were particularly effective. For these species, carbocation release could be reflex, that is, concurrent with radical generation. Only small radical enhancements were observed for release of lithium cations because of the ionic character of most of the precursors. Ethyne units could be incorporated as spacers between the radical center and the site of carbocation generation. Moreover, the enhancement was transmitted down polyethyne chains of at least six units.

5- Endo Cyclizations of NHC-Boraallyl Radicals Bearing Ester Substituents: Characterization of Derived 1,2-Oxaborole Radicals and Boralactones.

EPR studies of radical hydrogen abstraction reactions of N-heterocyclic carbene (NHC) complexes of alkenylboranes bearing two ester substituents revealed not the expected boraallyl radicals but instead isomeric 1,2-oaxborole radicals. Such radicals are new, and DFT calculations show that they arise from the initially formed boraallyl radicals by a rapid, exothermic 5- endo cyclization. These spectroscopic and computational discoveries prompted a series of preparative experiments that provided access to a novel family of robust NHC-boralactones. A one-pot procedure was developed to access the boralactones directly from an NHC-borane (NHC-BH3) and dimethyl acetylenedicarboxylate.

Microhydration and the Enhanced Acidity of Free Radicals.

Recent theoretical research employing a continuum solvent model predicted that radical centers would enhance the acidity (RED-shift) of certain proton-donor molecules. Microhydration studies employing a DFT method are reported here with the aim of establishing the effect of the solvent micro-structure on the acidity of radicals with and without RED-shifts. Microhydration cluster structures were obtained for carboxyl, carboxy-ethynyl, carboxy-methyl, and hydroperoxyl radicals. The numbers of water molecules needed to induce spontaneous ionization were determined. The hydration clusters formed primarily round the CO2 units of the carboxylate-containing radicals. Only 4 or 5 water molecules were needed to induce ionization of carboxyl and carboxy-ethynyl radicals, thus corroborating their large RED-shifts.

Enhanced Proton Loss from Neutral Free Radicals: Toward Carbon-Centered Superacids.

Radical centers close to protons are known to enhance their dissociation. Investigation of the generality of this radical enhanced deprotonation (RED-shift) phenomenon, and the kinds of structures in which it operates, are reported. The pKas for sulfinic, sulfonic, pentan-2,4-dione, and Meldrum's acid species, with adjacent radicals centered on C-, N-, and O atoms, were computed by a DFT method from free energies of deprotonation. All series showed significant RED-shifts that increased with the electronegativity of the radical center. The hugely negative pKa obtained for a Meldrum's acid with an alkoxyl radical substituent showed it to belong to the superacid class. The ethyne unit was found to be uniquely effective at enhancing acidity and conducting RED-shifts through chains up to and beyond 20 atoms. These connector units enable a radical center to alter the pKa of a spatially remote acidic group. RED-shifted species were characterized by conjugate radical anions displaying site exchange of spin with electronic charge.

Dealkanative Main Group Couplings across the peri-Gap.

Here, we highlight the ability of peri-substitution chemistry to promote a series of unique P-P/P-As coupling reactions, which proceed with concomitant C-H bond formation. This dealkanative reactivity represents an interesting and unexpected expansion to the established family of main-group dehydrocoupling reactions. These transformations are exceptionally clean, proceeding essentially quantitatively at relatively low temperatures (70-140 °C), with 100% diastereoselectivity in the products. The reaction appears to be radical in nature, with the addition of small quantities of a radical initiator (azobis(isobutyronitrile)) increasing the rate dramatically, as well as altering the apparent order of reaction. DFT calculations suggest that the reaction involves dissociation of a phosphorus centered radical (stabilized by the peri-backbone) to the P-P coupled product and a free propyl radical, which carries the chain. This unusual reaction demonstrates the powerful effect that geometric constraints, in this case a rigid scaffold, can have on the reactivity of main group species, an area of research that is gaining increasing prominence in recent years.

Generation and Structure of Unique Boriranyl Radicals.

Three-member ring boracyclopropanes (boriranes) with N-heterocyclic carbene substituents were prepared by a recently discovered route. H atoms were selectively abstracted from the boron atoms by t-butoxyl radicals and this enabled boriranyl radicals to be detected and characterized by EPR spectroscopy for the first time. Their EPR parameters indicated they had planar π-character. From competition experiments, the rate constant for H atom abstraction was determined and found to be about 2 orders of magnitude less than for NHC-boranes. The B-H BDE of an NHC-borirane was estimated to be about 95 kcal mol-1.

N- to C-sulfonyl photoisomerisation of dihydropyridinones: a synthetic and mechanistic study.

The scope and limitations of a photoinitiated N- to C-sulfonyl migration process within a range of dihydropyridinones is assessed. This sulfonyl transfer proceeds without erosion of either diastereo- or enantiocontrol, and is general across a range of N-sulfonyl substituents (SO2R; R = Ph, 4-MeC6H4, 4-MeOC6H4, 4-NO2C6H4, Me, Et) as well as C(3)-(aryl, heteroaryl, alkyl and alkenyl) and C(4)-(aryl and ester) substitution. Crossover reactions indicate an intermolecular step is operative within the formal migration process, although no crossover from C-sulfonyl products was observed. EPR studies indicate the intermediacy of a sulfonyl radical and a mechanism is proposed based upon these observations.