Traces of Potassium Induce Restructuring of the Anatase TiO2(001)-(1×4) Surface from a Reactive to an Inert Structure.

Reconstruction of solid surfaces is generally accompanied by changes in surface activities. Here, via a combined experimental and theoretical study, we successfully identified that a trace amount of potassium dopant restructures the mineral anatase TiO2(001) single-crystal surface from an added molecule (ADM) termination to an added oxygen (AOM) one without changing the (1×4) periodicity. The anatase TiO2(001)-(1×4)-ADM surface terminated with 4-fold coordinated Ti4c and 2-fold coordinated O2c sites is (photo)catalytically active, whereas the anatase TiO2(001)-(1×4)-AOM surface terminated with O2c and inaccessible 5-fold coordinated Ti5c sites is inert. These results unveiled a mechanism of dopant-induced transformation from a reactive to an inert TiO2(001)-(1×4) surface, which unifies the existing arguments about the surface structures and (photo)catalytic activity of anatase TiO2(001)-(1×4).

Association between preoperative hypokalemia and postoperative complications in elderly patients: a retrospective study.

BACKGROUND: Hypokalemia is a common form of electrolyte disorder, which has a higher incidence in hospitalized patients and is closely related to perioperative complications and prognosis. Due to decreased skeletal muscle mass which causes total body potassium reduction, and increased comorbidities, the elderly are more susceptible to hypokalemia. OBJECTIVE: To investigate preoperative hypokalemia in elderly patients and its effect on postoperative complications. METHODS: Data were retrospectively collected from the elderly patients who underwent elective surgery from April 2018 to March 2019 and had preoperative blood gas data available. Patients, with age 60 to 100 years, were divided into hypokalemia group (potassium level < 3.5 mmol/L) and normokalemia group (potassium level between 3.5 and 5.5 mmol/L) according to preoperative blood gas analysis. Hypokalemia can be divided into mild (potassium level 3.0 to 3.5 mmol/L), moderate (potassium level 2.5 to 3.0 mmol/L) and severe (potassium level < 2.5 mmol/L), respectively. The risk factors of preoperative hypokalemia and its impact on postoperative complications and prognosis were primary outcomes. Secondary outcomes included postanesthesia care unit (PACU) stay time and hospital length of stay (LOS). RESULTS: Of 987 participants, 436 (44.17%) developed preoperative hypokalemia, among them 357 (81.88%) mild, 87 (16.74%) moderate and 6 (1.38%) severe. Multivariate logistic regression showed that female gender (OR, 1.851; 95% CI, 1.415-2.421), pre-existing hypokalemia at admission (OR, 4.498; 95% CI, 2.506-8.071), and oral laxative twice or more (OR, 1.823; 95% CI, 1.266-2.624) are risk factors of preoperative hypokalemia. Gynecological and biliopancreatic surgery were more common in hypokalemia group than normokalemia group (P <  0.001, P <  0.05). There was no significant difference in postoperative complications, PACU stay time, LOS, and 30-day mortality between the two groups (all P >  0.05). CONCLUSIONS: Female gender, pre-existing hypokalemia at admission, and oral laxative twice or more are independent risk factors for preoperative hypokalemia in elderly patients. However, postoperative complications and 30-day mortality were not increased, which may be related to monitoring blood gas analysis and prompt correction of potassium levels during surgery.

Step Site-Specific Semihydrogenation of Acetylene on the Au Surface.

Supported Au catalysts are highly selective and size-sensitive in catalytic hydrogenation of alkynes under mild conditions. Using thermal-programmed desorption and density functional theory calculations, we study the hydrogenation reactions of C2 hydrocarbons with atomic H and clarify the site-specific selective hydrogenation of C2H2 on Au(997) at low temperatures. On atomic H(a) covered Au(997), hydrogenation of C2H2 goes with 100% selectivity to C2H4 at steps, yet no hydrogenation occurs at terraces; adsorbed C2H4 on neither steps nor terraces reacts with H(a). DFT calculations suggest that the increased adsorption free energies and appropriate reaction barriers of C2 species at steps lead to the step-site specific semihydrogenation of C2H2. These results elucidate the elementary surface reactions between C2 hydrocarbons and atomic H on Au surfaces at the molecular level and significantly deepen the fundamental understanding of the unique selectivity of Au catalysts.

A near-ambient pressure flow reactor coupled with polarization-modulation infrared reflection absorption spectroscopy for operando studies of heterogeneous catalytic reactions over model catalysts.

The model catalyst approach is often used for fundamental investigations of complex heterogeneous catalysis, in which operando characterizations are critical. A flow reactor is usually adopted for gas-solid heterogeneous catalytic reactions. Herein, we report a home-designed near-ambient pressure (NAP) flow reactor coupled with polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS) and an online quadrupole mass spectrometer for operando studies of heterogeneous catalytic reactions over model catalysts. A unique gas supply system is designed and manufactured to enable a stable gas inlet to the NAP flow reactor at pressures up to ∼100 mbar. An ultrahigh vacuum chamber equipped with the facilities for x-ray photoelectron spectroscopy, low-energy electron diffraction, thermal desorption spectroscopy, E-beam evaporation source, and ion sputtering gun is connected to the NAP flow reactor via a gate valve for preparations and routine characterizations of model catalysts. The functions of the system are demonstrated by in situ PM-IRAS characterization of CO adsorption on Pt(111) and operando characterizations of CO oxidation on Pt(111) under NAP conditions.

In Situ Generated Ti3+-Mediated Photocatalytic Methanol Decomposition to Carbon Monoxide and Hydrogen on a Rutile TiO2(100) Surface.

Photocatalysis of methanol on the TiO2 surface is a prototype of photocatalytic reactions. Here, we unveil a synergistic effect of photoexcited electrons and holes on converting methanol to CO and H2 on a rutile TiO2(100) surface. Upon Hg light irradiation, photoexcited holes oxidize methoxy species at the 5-fold coordinated Ti4+ sites sequentially to formaldehyde and formate intermediates, while photoexcited electrons reduce the associated Ti4+ sites to Ti3+ sites. The formate intermediates selectively decompose to CO and H2 mediated by the Ti3+ sites at elevated temperatures. These results greatly enrich methanol photochemistry on the TiO2 surface and point to a surface structure engineering strategy of oxide photocatalysts for photocatalytic direct methanol decomposition to CO and H2.

Size-Dependent Pt-TiO2 Strong Metal-Support Interaction.

The strong metal-support interaction (SMSI) is one of the most important concepts in heterogeneous catalysis. Herein we report a study of Pt-TiO2 SMSI using Pt/rutile TiO2(110) model catalysts with different Pt particle sizes by means of X-ray photoelectron spectroscopy, ion scattering spectroscopy, and the adsorption of probe molecules. The acquired results unambiguously demonstrate a size dependence of the Pt-TiO2 SMSI, in which SMSI occurs barely between supported Pt clusters and the TiO2(110) substrate but obviously between supported Pt nanoparticles and the TiO2(110) substrate. Such a size-dependent SMSI could be associated with size-dependent electronic structures of the supported Pt particles. These results highlight the sensitivity of the SMSI to the size of supported metal particles, which greatly advances the fundamental understanding.

Elucidating Surface Structure with Action Spectroscopy.

Surface Action Spectroscopy, a vibrational spectroscopy method developed in recent years at the Fritz Haber Institute is employed for structure determination of clean and H2O-dosed (111) magnetite surfaces. Surface structural information is revealed by using the microscopic surface vibrations as a fingerprint of the surface structure. Such vibrations involve just the topmost atomic layers, and therefore the structural information is truly surface related. Our results strongly support the view that regular Fe3O4(111)/Pt(111) is terminated by the so-called Fetet1 termination, that the biphase termination of Fe3O4(111)/Pt(111) consists of FeO and Fe3O4(111) terminated areas, and we show that the method can differentiate between different water structures in H2O-derived adsorbate layers on Fe3O4(111)/Pt(111). With this, we conclude that the method is a capable new member in the set of techniques providing crucial information to elucidate surface structures. The method does not rely on translational symmetry and can therefore also be applied to systems which are not well ordered. Even an application to rough surfaces is possible.

The effectiveness of allogeneic mesenchymal stem cells therapy for knee osteoarthritis in pigs.

BACKGROUND: Intraarticular injection of the mesenchymal stem cells (MSCs) has shown to be successful for treating osteoarthritis (OA). Nevertheless, many studies have been focusing on autologous MSCs. The following study investigates the safety and effectiveness of intraarticular injection of allogenic MSCs in a pig OA model. METHODS: Superparamagnetic iron oxide (SPIO) nanoparticles were labelled with bone marrow-derived mesenchymal stem cells (BM-MSCs) to allow cells tracking using magnetic resonance imaging (MRI). A pig OA model was established by bilateral medial meniscectomy. Next, SPIO-BM-MSCs were injected into the right knee, while the left knee was left untreated. MRI and radiography were used to assess the degree of OA and to evaluate the effectiveness of allogenic MSCs. Hematoxylin and eosin (H&E), safranin-o fast green staining, toluidine blue, and immunohistochemical staining were used to evaluate the therapeutic effect of the injections. RESULTS: At concentration of ≤20 µg/mL, SPIO caused no toxicity to BM-MSCs. Four weeks after surgery, OA changes were observed on MRI scan. The SPIO labeled BM-MSCs were found moving towards the impaired part of the cartilage 8 to 24 h after injections. In addition, no significant differences between the right side (therapeutic side) and the left side (untreated side) were observed following histological and immunohistochemistry analysis. CONCLUSIONS: The suitable concentration of SPIO for labelling BMSCs was 20 µg/mL, while the allogenic MSCs could move towards and accumulate around the impaired cartilage. No significant difference was found between treatment and control group.

Predicting the graft diameter of the peroneus longus tendon for anterior cruciate ligament reconstruction.

The aim of this study was to evaluate the correlation between various anthropometric parameters and the graft diameter of the peroneus longus tendon (PLT).We retrospectively analyzed the data of 156 patients who underwent anterior cruciate ligament reconstruction (ACLR) with the PLT graft at our institution. Anthropometric parameters, including height, weight, gender, age, duration of injury, and preinjury activity levels, were recorded. t tests, correlation coefficients (Pearson r), and a multiple linear regression analysis were used to evaluate the influence of these anthropometric variables on the diameter of the graft obtained.The mean PLT graft diameter was 8.3 mm, and 21 patients (13.5%) had a diameter less than 8 mm; 85 patients (54.5%) had a diameter between 8 and 9 mm, and 50 patients (32.0%) had a diameter greater than or equal to 9 mm. The correlation analysis showed that height (P < .001), weight (P < .001), and duration of injury (P = .012) were significantly related to graft diameter. On the basis of these 3 predictors, the following regression equation was obtained: Diameter = 2.28 + 0.028*height (cm) + 0.013*weight (kg) + 0.289*duration of injury (0 or 1). Patients who were short and shin were more likely to own smaller graft diameters (<8 mm), especially the one ruptured his or her anterior cruciate ligament (ACL) over 3 months.Height, weight, and duration of injury were associated with the diameter of PLT. They are important preoperative information for surgeon about the size of PLT and can be used for alternative graft source planning and patient counseling.Level of evidence: IV.

Surface action spectroscopy with rare gas messenger atoms.

Action spectroscopy with inert gas messengers is commonly used for the characterization of aggregates in the gas phase. The messengers, often rare gas atoms or D2 molecules, are attached to the gas phase aggregates at low temperature. Vibrational spectra of the aggregates are measured via detection of inert gas desorption following a vibrational excitation by variable-energy infrared light. We have constructed an apparatus for the application of action spectroscopy to surfaces of solids with the aim of establishing a new method for the vibrational spectroscopy of surfaces and deposited clusters. Experiments performed for neon covered V2O3(0001) show that this method can provide information about surface vibrations. Besides the surface sensitive channel, there is also a bulk sensitive one as demonstrated with the example of CeO2(111) thin film data. Unlike infrared reflection absorption spectroscopy, normalization to a reference spectrum is not required for action spectroscopy data, and unlike high resolution electron energy loss spectroscopy, the action spectroscopy method does not suffer from moderate resolution nor from multiple excitations. Selective decoration of specific surface features with messenger atoms may be utilized to focus the spectroscopic information onto these features.

Cerebral oxygen desaturation occurs frequently in patients with hypertension undergoing major abdominal surgery.

Hypertensive patients are more likely to experience latent cerebral ischemia causing regional cerebral oxygen saturation (rSO2) decrease during general anesthesia. The aim of this prospective observational study was to assess the incidence of decreased rSO2 in hypertensive patients undergoing major abdominal surgery and the perioperative factors affecting this change in rSO2. A total of 41 hypertensive patients were enrolled and stratified according to their hypertension as controlled and uncontrolled. The intraoperative rSO2 and physiological data were routinely collected. The Mini-Mental State Exam (MMSE) was used to test cognitive function before surgery and after 4 days. Cerebral desaturation was defined as a decrease in rSO2 of more than 20% of the baseline value. There were 20 patients (49%) suffering intraoperative cerebral desaturation classified into cerebral desaturation group (group D) and those 21 without intraoperative desaturation classified into normal group (group N). The area under the curve below 90 and 80% of baseline (AUCrSO2 <90% of baseline and AUCrSO2 <80% of baseline) was lower in patients of group N (2752.4 ± 1453.3 min% and 0.0 min%) than in patients of group D (6264.9 ± 1832.3 min% and 4486.5 ± 1664.9 min%, P < 0.001). Comparing the two groups, the number of uncontrolled hypertensive individuals in group D (12/20) was significantly more than group N (4/21) (P = 0.007). A significant correlation was observed between relative decrease in MAP and relative decrease in rSO2 (r2 = 0.495, P < 0.001). Moreover, nine patients (45%) in group D occurred early postoperative cognitive function decline were more than three patients (14.3%) in group N (P = 0.031). This pilot study showed a large proportion of hypertensive patient experienced cerebral desaturation during major abdominal surgery and uncontrolled hypertension predisposed to this desaturation. NCT02147275 (registered at http://www.clinicaltrials.gov ).

Self-Anticoking of a Cobalt Surface by Subsurface Oxygen in the Fischer-Tropsch Synthesis.

Understanding the fundamental processes taking place on Co surfaces during the Fischer-Tropsch (FT) synthesis is of great interest and importance. We herein report a self-anticoking mechanism of a cobalt surface by subsurface oxygen. The active carbidic carbon species for FT synthesis tends to transform into the inactive graphitic carbon species on clean Co(0001) and poisons the Co surface. Subsurface atomic oxygen on Co(0001) can stabilize the active carbidic carbon species and quench the transformation process. These results reveal, to the best of our knowledge, for the first time the reactivity of various surface species on Co surfaces that dynamically maintain a delicate balance to enhance the long-term stability of Co catalysts during FT synthesis.

Vibrational Action Spectroscopy of Solids: New Surface-Sensitive Technique.

Vibrational action spectroscopy employing infrared radiation from a free-electron laser has been successfully used for many years to study the vibrational and structural properties of gas phase aggregates. Despite the high sensitivity of this method no relevant studies have yet been conducted for solid sample surfaces. We have set up an experiment for the application of this method to such targets, using infrared light from the free-electron laser of the Fritz Haber Institute. In this Letter, we present first results of this technique with adsorbed argon and neon atoms as messengers. We were able to detect surface-located vibrations of a thin V_{2}O_{3}(0001) film on Au(111) as well as adsorbate vibrations, demonstrating that this method is highly surface sensitive. We consider that the dominant channel for desorption of the messenger atoms is direct inharmonic vibrational coupling, which is essentially insensitive to subsurface or bulk vibrations. Another channel is thermal desorption due to sample heating by absorption of infrared light. The high surface sensitivity of the nonthermal channel and its insensitivity to subsurface modes makes this technique an ideal tool for the study of surface-located vibrations.

Methanol Conversion into Dimethyl Ether on the Anatase TiO2(001) Surface.

Exploring reactions of methanol on TiO2 surfaces is of great importance in both C1 chemistry and photocatalysis. Reported herein is a combined experimental and theoretical calculation study of methanol adsorption and reaction on a mineral anatase TiO2(001)-(1×4) surface. The methanol-to-dimethyl ether (DME) reaction was unambiguously identified to occur by the dehydration coupling of methoxy species at the fourfold-coordinated Ti(4+) sites (Ti(4c)), and for the first time confirms the predicted higher reactivity of this facet compared to other reported TiO2 facets. Surface chemistry of methanol on the anatase TiO2(001)-(1×4) surface is seldom affected by co-chemisorbed water. These results not only greatly deepen the fundamental understanding of elementary surface reactions of methanol on TiO2 surfaces but also show that TiO2 with a high density of Ti(4c) sites is a potentially active and selective catalyst for the important methanol-to-DME reaction.

Recurrent cervicodorsal spinal intradural enterogenous cyst: case report and literature review.

This report described a recurrent enterogenous cyst of the cervicodorsal spinal canal occurred in an 8-year-old boy who experienced cervical back pain at the age of 5. He had been operated for mass lesion at the same level 3 years ago. The cervical and thoracic spine MRI showed a large intradural cyst at C7-T1. The cyst was subtotally removed via posterior approach using a laminectomy. Based on the results of immunostaining, it was identified as an enterogenous cyst. A literature review related to spinal cyst is also included.

Active hydrogen species on TiO2 for photocatalytic H2 production.

Photocatalytic H2 production over TiO2 has attracted tremendous attention and achieved great progress, but the active hydrogen species is still unknown. Employing a rutile TiO2(110) surface as a model catalyst we report here for the first time the direct observation of photocatalytic H2 production under ultrahigh vacuum conditions during UV-light irradiation at 115 K and the identification of negatively-charged hydride-type H-Ti species as the corresponding photoactive surface species by means of thermal desorption spectroscopy, photon-stimulated desorption spectroscopy, X-ray photoelectron spectroscopy and DFT calculations. The formation and stability of H-Ti species are closely related to available surplus electrons on the rutile TiO2(110) surface that can be created by the formation of surface BBO vacancies or by the formation of surface hydroxyls via the adsorption of atomic H or molecular H2 on O sites. The photocatalytic H2 production from H-Ti species is hole-mediated and co-existing water exerts a negative effect on this process.

Reaction mechanism of WGS and PROX reactions catalyzed by Pt/oxide catalysts revealed by an FeO(111)/Pt(111) inverse model catalyst.

We have employed XPS and TDS to study the adsorption and surface reactions of H2O, CO and HCOOH on an FeO(111)/Pt(111) inverse model catalyst. The FeO(111)-Pt(111) interface of the FeO(111)/Pt(111) inverse model catalyst exposes coordination-unsaturated Fe(II) cations (Fe(II)CUS) and the Fe(II)CUS cations are capable of modifying the reactivity of neighbouring Pt sites. Water facilely dissociates on the Fe(II)CUS cations at the FeO(111)-Pt(111) interface to form hydroxyls that react to form both water and H2 upon heating. Hydroxyls on the Fe(II)CUS cations can react with CO(a) on the neighbouring Pt(111) sites to produce CO2 at low temperatures. Hydroxyls act as the co-catalyst in the CO oxidation by hydroxyls to CO2 (PROX reaction), while they act as one of the reactants in the CO oxidation by hydroxyls to CO2 and H2 (WGS reaction), and the recombinative reaction of hydroxyls to produce H2 is the rate-limiting step in the WGS reaction. A comparison of reaction behaviors between the interfacial CO(a) + OH reaction and the formate decomposition reaction suggest that formate is the likely surface intermediate of the CO(a) + OH reaction. These results provide some solid experimental evidence for the associative reaction mechanism of WGS and PROX reactions catalyzed by Pt/oxide catalysts.

Photocatalytic cross-coupling of methanol and formaldehyde on a rutile TiO2(110) surface.

The photocatalytic oxidation of methanol on a rutile TiO2(110) surface was studied by means of thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). The combined TDS and XPS results unambiguously identify methyl formate as the product in addition to formaldehyde. By monitoring the evolution of various surface species during the photocatalytic oxidation of methanol on TiO2(110), XPS results give direct spectroscopic evidence for the formation of methyl formate as the product of photocatalytic cross-coupling of chemisorbed formaldehyde with chemisorbed methoxy species and clearly demonstrate that the photocatalytic dissociation of chemisorbed methanol to methoxy species occurs and contributes to the photocatalytic oxidation of methanol. These results not only greatly broaden and deepen the fundamental understanding of photochemistry of methanol on the TiO2 surface but also demonstrate a novel green and benign photocatalytic route for the synthesis of esters directly from alcohols or from alcohols and aldehydes.

Direct electron transfer and electrochemical study of hemoglobin immobilized in ZnO hollow spheres.

ZnO hollow spheres were firstly prepared. A new type of amperometric hydrogen peroxide biosensor was fabricated by entrapping Hemoglobin (Hb) through the ZnO hollow spheres (ZHS) nanoparticles. The composition morphology and size were studied by transmission electron microscopy. The surface topography of the prepared films was imaged by atomic force microscope (AFM). Several techniques, including UV-vis absorption spectroscopy, cyclic voltammetry, chronoamperometry were employed to characterize the performance of the biosensor. The results indicated that the ZHS nanoparticles had enhanced the performance of the hydrogen peroxide sensors. The electrochemical parameters of Hb in the ZHS were calculated by the results of the electron-transfer coefficient (α) and the apparent heterogeneous electron-transfer rate constant K (s) as 0.5 and 3.1 s(-1), respectively. The resulting biosensors showed a wide linear range from 2.1 × 10(-6) to 5.18 × 10(-3) M, with a low detection limit of 7.0 × 10(-7) M (S/N = 3) under optimized experimental conditions. The results demonstrated that the ZHS matrix may improve the protein loading with the retention of bioactivity and greatly promote the direct electron transfer, which can be attributed to its unique morphology, high specific surface area, and biocompatibility. The biosensor obtained from this study possesses high sensitivity, good reproducibility, and long-term stability.