Chiral Linker Installation in a Metal-Organic Framework for Enantioselective Luminescent Sensing.

Linker installation is a potent strategy for integrating specific properties and functionalities into metal-organic frameworks (MOFs). This method enhances the structural diversity of frameworks and enables the precise construction of robust structures, complementing the conventional postsynthetic modification approaches, by fully leveraging open metal sites and active organic linkers at targeting locations. Herein, we demonstrated an insertion of a d-camphorate linker into a flexible Zr-based MOF, PCN-700, through linker installation. The resultant homochiral MOF not only exhibits remarkable stability but also functions as a highly efficient luminescent material for enantioselective sensing. Competitive absorption and energy/electron transfer processes contribute to the sensing performance, while the difference in binding affinities dominates the enantioselectivity. This work presents a straightforward route to crafting stable homochiral MOFs for enantioselective sensing.

Charge transfer transitions of the O2+-Ar and O2+-N2 complexes.

Electronic transitions are observed for the O2+-Ar and O2+-N2 complexes over the 225-350 nm range. The transitions are not associated with recognized electronic band systems of the respective atomic and diatomic constituents (Ar+, Ar, O2+, O2, N2+, and N2) but rather are due to charge transfer transitions. Onsets of the O2+-Ar and O2+-N2 band systems occur at 3.68 and 3.62 eV, respectively, corresponding to the difference in the ionization potentials of Ar and O2 (3.69 eV), and N2 and of O2 (3.51 eV), suggesting the band systems arise from intramolecular charge transfer transitions to states correlating with O2(X3Σg-) + Ar+ (2Pu) and O2(X3Σg-) + N2+(X2Σg+) limits, respectively. The dominant vibronic progressions have ωe values of 1565 cm-1 for O2+-Ar and 1532 cm-1 for O2+-N2, reasonably close to the value for the neutral O2 molecule in its X3Σg- state (1580 cm-1). Higher energy band systems for O2+-Ar and O2+-N2 are assigned to transitions to states correlating with the O2 (a1Δg) + Ar+ (2Pu) and O2 (a1Δg) + N2+(X2Σg+) limits, respectively.

Interstellar hide and go seek: C3H4O. There and back (again).

The molecular species C3H4O represents a striking example of an astrochemical conundrum. With more than 60 structural isomers theoretically possible, to date only acrolein (CH2CHCHO) has been identified in the Sgr B2(N) region of the interstellar medium (ISM). The topography of the singlet potential energy surface is complicated, with three low-lying minima predicted to be almost isoenergetic: cis and trans-acrolein, and methylketene (CH3CHCO). Our CCSD(T)/cc-pVTZ calculations confirm that methylketene is energetically lower than cis-acrolein, lying only 1.9 kJ mol-1 above the trans-isomer, which is the global minimum. In this respect, methylketene is a promising candidate for interstellar observation. Unfortunately, however, despite several searches its astronomical detection has been unsuccessful. To this end, the key question is whether in fact methylketene exists as a discrete chemical entity in the ISM at all? In this paper, we present a detailed examination of the C3H4O potential energy surface, with specific focus on formation pathways. CCSD(T)/cc-pVTZ calculations enable a more elaborate interpretation of reaction mechanisms than was published hitherto. Our results show that gauche-propargyl alcohol and syn and anti-allenol emerge as interesting new targets for observational astronomers in TMC-1: given the recent discovery of the propargyl radical in this region, barrierless product channels involving OH˙ lend support to their candidacy as possible interstellar species. Finally, this work provides accurate spectral data of these three potential molecules, to be used for searches in interstellar space.

Electronic spectrum of the propargyl cation (H2C3H(+)) tagged with Ne and N2.

The Ã(1)A1 ← X̃(1)A1 band system of the propargyl cation (H2C3H(+)) is measured over the 230-270 nm range by photodissociation of mass-selected H2C3H(+)-Ne and H2C3H(+)-N2 complexes in a tandem mass spectrometer. The band origin occurs at 37 618 cm(-1) for H2C3H(+)-Ne and 37 703 cm(-1) for H2C3H(+)-N2. Ground and excited state ab initio calculations for H2C3H(+) using the MCSCF and coupled-cluster (CC) response methods show that the ion has C2v symmetry in the ground X̃(1)A1 and excited Ã(1)A1 states and that the strong vibronic progression with a spacing of 630 cm(-1) is due to the C-C stretch vibrational mode, ν 5.

The prevalence and impact of undiagnosed cognitive impairment in older vascular surgical patients.

OBJECTIVE: The objectives of this observational cohort study were to investigate the prevalence of undiagnosed cognitive impairment in older patients presenting for vascular surgery, to examine its association with adverse postoperative outcomes, and to test the feasibility of a preoperative cognitive assessment tool. METHODS: Patients aged 60 years or older were recruited by consent on admission to the vascular surgical ward of an inner-city teaching hospital with a large tertiary referral practice for proposed elective or emergency aortic or lower limb arterial intervention. Cognition was assessed preoperatively by the Montreal Cognitive Assessment (MoCA), and a score below 24/30 indicated cognitive impairment or dementia. The mean length of time taken to complete the assessment was recorded. Baseline characteristics (medical multimorbidity, frailty, and laboratory tests), hospital length of stay (LOS), and postoperative complications were documented. RESULTS: Preoperative MoCA was completed in 114 patients with a mean age of 76.3 years (standard deviation, 7.36 years); 67.5% were men, and 55.3% of procedures were elective. The MoCA was completed in 100% of patients and was quick and acceptable to patients in this setting. Cognitive impairment or dementia was found in 68% of patients (77 of 114) and was previously unrecognized in 88.3% of patients (68 of 77). Therefore, 60.5% of patients (68 of 114) aged 60 years or older presenting for vascular surgery had previously undiagnosed cognitive impairment. MoCA <24 was univariately associated with pre-existing frailty (Edmonton Frail Scale [EFS] score ≥6.5) and longer LOS (≥12 days). In logistic regression modeling, MoCA <24 was strongly independently associated with frailty EFS score ≥6.5 (odds ratio, 12.55; P < .001). By use of the area under the receiver operating characteristic curve (AUC), MoCA <24 was predictive of longer LOS of ≥12 days (AUC, 0.621; P = .049). The strength of predictive power increased with the addition of frailty (EFS score ≥6.5) to the models (AUC, 0.695; P = .002). CONCLUSIONS: The prevalence of cognitive impairment among older patients presenting for vascular surgery is high and frequently undiagnosed before admission. It is feasible to use the MoCA to identify cognitive impairment in this high-risk surgical group preoperatively. The combined assessment of frailty and cognition is predictive of adverse postoperative outcomes and longer LOS.

Lossless compression of wave function information using matrix factorization: A "gzip" for quantum chemistry.

We propose the use of the singular value decomposition to decrease the storage required for wave function information. The specific case considered is determinantal full configuration interaction, but the same technique is readily applicable to truncated configuration interaction and coupled-cluster calculations of various types; as we discuss this is a reformulation of approximate methods that have been in use for some time, but our approach eliminates those approximations. Numerical examples support the contention that considerable compression of the wave function is possible without significant loss of accuracy: as expected a considerable amount of the information contained in the full CI wave function is redundant.

A new imaging method for assessment of aortic dissection using four-dimensional phase contrast magnetic resonance imaging.

INTRODUCTION: Medical management of type B aortic dissection can result in progressive dilation of the false lumen and poor long-term outcome. Recent studies using models of aortic dissection have suggested flow characteristics, such as stroke volume, velocity, and helicity, are related to aortic expansion. The aim of this study was to assess whether four-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) can accurately visualize and quantify flow characteristics in patients with aortic dissection and whether these features are related to the rate of aortic expansion. METHODS: Twelve consecutive patients with medically treated type B thoracic aortic dissection underwent a three-dimensional (3D) MRI anatomy scan using a blood pool contrast agent. Two-dimensional phase contrast MRI data (2D PC-MRI) were acquired in the ascending and descending aorta and 4D PC-MRI data were acquired in the entire thoracic aorta. The 2D PC-MRI measurements were used to assess the quality of the 4D PC-MRI velocity data. Stroke volume, velocity, and the direction of flow were calculated using 4D PC-MRI and related to the rate of aortic expansion measured on contrast-enhanced computed tomography. RESULTS: Comparison of 2D PC-MRI and 4D PC-MRI measurements showed good correlation (Pearson R(2) = 0.98; 95% confidence interval [CI], 0.9818-0.9953; P < .0001) and no proportional bias (bias = 1.0 mL; standard deviation, 4.6). The median aortic growth rate was 6.1 mm/y (interquartile range [IQR], 1.1-15.1 mm/y), and this correlated well with the growth rate of the false lumen (Spearman ρ = 0.62; 95% CI, 0.06-0.89; P = .0347). False lumen thrombosis (FLT) was seen in 7 of 12 patients and was not associated with reduced aortic expansion rate (FLT present: 11.4 mm/y; IQR, 3.6-21.4) vs FLT absent: 9.9 mm/y; IQR, 3.4-24.2; Mann-Whitney P = .8763). False lumen stroke volume and velocity were associated with more rapid aortic expansion (ρ = 0.80 [95% CI, 0.39-0.94; P = .0029] and ρ = 0.59 [95% CI, 0.09-0.87; P = .0480] respectively). The position of the dominant entry tear was associated with rapid expansion, which tended to be higher with distal vs proximal entry tears (distal, 21.4 mm/y [IQR, 11.4-48.9] vs proximal, 5.5 mm/y [IQR, 3.4-16.6]; Mann-Whitney P = .096). Helical flow was seen in the false lumen in 8 of 12 patients and was related to the rate of aortic expansion (ρ = 0.83, P = .0154). CONCLUSIONS: 4D PC-MRI can be accurately applied to visualize and quantify flow characteristics in patients with aortic dissection. Stroke volume, velocity, distal dominant entry tears, and helical flow are related to the rate of aortic expansion. This study demonstrates the potential of this new imaging method. A larger prospective study is now required to measure flow characteristics and determine their predictive value for risk stratification of patients with aortic dissection.

Endovascular repair of the aorta and aortic arch arteries damaged during mediastinoscopy.

Despite advances in imaging techniques, mediastinoscopy remains an important tool for the staging of the mediastinum in non-small cell lung cancer and diagnosing lymphoma with mediastinal adenopathy. Injury to the arterial system during mediastinoscopy is infrequent but a potentially fatal complication. We report three cases of injury to the aorta and supra-aortic arteries sustained during mediastinoscopy. These were effectively managed by endovascular techniques. Patient recovery was uncomplicated and median length of stay was 3 days. This technique avoids major open surgery in a high-risk group of patients and may offer a mortality benefit and more rapid resumption of oncological treatment.

Stent-graft limb deployment in the external iliac artery increases the risk of limb occlusion following endovascular AAA repair.

PURPOSE: To assess whether deployment of an endograft limb in the external iliac artery (EIA) increases the rate of limb occlusion following endovascular aneurysm repair (EVAR). METHODS: Interrogation of a prospectively maintained database identified 661 patients (596 men; median age 73 years, range 37-93) with infrarenal abdominal aortic aneurysm who underwent EVAR between 1996 and 2010 using Zenith stent-grafts predominately. Of these, 567 patients [56 (9.9%) women] had both endograft limbs deployed in the CIA (1203 limbs at risk), while 94 patients [9 (9.6%) women] had at least 1 limb in the EIA (22 bilateral; 116 limbs at risk). An adjunctive bare metal stent was used in 8 (9%) limbs deployed in the EIA. RESULTS: There were 31 limb occlusions, all unilateral: 17 (3%) patients in the CIA group had an occluded limb (1% of limbs at risk) vs. 14 (15%) patients in the EIA group (12% of limbs at risk; p<0.0001). The median time to occlusion was 3 months (0-60) in the CIA group and 1 month (0-36) in the EIA group. The majority of occlusions were treated by extra-anatomical revascularization, most often a femorofemoral crossover bypass. No legs were amputated following occlusion of a limb placed in the CIA, but there were 3 amputations in the EIA group (p=0.003). CONCLUSION: Deployment of endograft limbs into the EIA led to a higher rate of occlusion and leg amputation. Increased tortuosity of the EIA and a smaller caliber vessel are likely to account for the increased risk.

A new method for quantification of false lumen thrombosis in aortic dissection using magnetic resonance imaging and a blood pool contrast agent.

BACKGROUND: False lumen thrombosis after aortic dissection is a major predictor of prognosis. First pass computed tomography (CT) and magnetic resonance (MR) imaging are used routinely, where the image acquisition is timed to the arrival of contrast in the proximal unaffected aorta. Delayed phase imaging is difficult to refine because flow rates in the false lumen are often very slow and highly variable between patients. Blood pool contrast agents bind to albumin and become homogenously distributed in the intravascular circulation, allowing accurate imaging of areas where flow is low. We compared first pass MR and CT with a delayed phase MR acquisition using a blood pool agent to assess whether this more accurately quantified false lumen thrombosis. METHODS: Patients with medically treated chronic type B aortic dissection and evidence of false lumen thrombosis on previous CT imaging underwent first pass CT, first pass MR, and delayed phase MR with blood pool agent. Absence of false lumen contrast enhancement was quantified to assess the apparent differences in thrombosis. Phase-contrast MR data were also obtained to assess the affect of flow velocity on false lumen contrast enhancement, and direct thrombus MR images were used to confirm the presence of thrombus. RESULTS: Twelve patients were recruited. No difference was seen in apparent thrombus volume between first pass CT and first pass MR imaging (146.9 cm(3) [SD, 88.6] vs 187.6 cm(3) [SD, 136.1], P = .1119; R(2) = .67 [95% confidence interval (CI), r = .46-.95], P = .0012). In all patients, the volume of thrombus derived from first pass acquisitions was greater than the volume derived from delayed phase MR imaging with blood pool agent: first pass CT (paired t test, P = .0007; mean difference = 83.4 cm(3) [95% CI, 44.1-122.6]) and first pass MR (paired t test, P = .0009; mean difference = 124.0 cm(3) [95% CI, 63.2-184.9]). The difference in thrombus volume between first pass and delayed phase MR imaging with blood pool agent correlated significantly with the mean velocity of flow in the false lumen, with lower flow related to a greater difference (R(2) = .61, P = .0028 [95% CI, r = -.94--.37]). Direct thrombus MR images were able to correctly discriminate between thrombus and blood and matched the area of contrast absence on delayed phase MR with blood pool agent images. CONCLUSION: First pass techniques to assess false lumen thrombosis in aortic dissection consistently overestimate the apparent thrombus volume by five to six times. This has implications for interpretation of cohort studies and clinical trials that use false lumen thrombosis as an outcome measure. We recommend delayed phase MR imaging with a blood pool agent when accurate assessment of false lumen thrombosis is required.

Endovascular treatment of acute aortic syndrome.

BACKGROUND: The term acute aortic syndrome (AAS) encompasses a range of conditions that have a risk of imminent aortic rupture and where delays in treatment result in increased mortality. Endovascular treatment offers an attractive alternative to open surgery but little is known about the durability of the repair and the factors that predict mortality. METHODS: Prospective data were collected for a cohort of 110 consecutive patients with endovascular treatment for AAS. Patient and procedural characteristics were related to short- and midterm outcome using multivariate logistic regression analysis. RESULTS: There were 75 men and 35 women with a median age of 68 (range 57-76) years. The pathologies treated were acute dissection (35), symptomatic aneurysm (32), infected aneurysm (18), transection (12), chronic dissection (9), penetrating ulcer (3), and intramural hematoma (1). Thirty-day mortality was 12.7% and this was associated with hypotension (odds ratio [OR], 5.25), use of general anesthetic (OR, 5.23), long procedure duration (OR, 2.03), and increasing age (OR, 1.07). The causes of death were aortic rupture (4), myocardial infarction (4), stroke (3), and multisystem organ failure (3). The stroke and paraplegia rates were 7.3% and 6.4%, respectively. The 1-year survival was 81% and the 5-year survival 63%. Secondary procedures were required in 13 (11.8%) patients. Factors associated with death at 1 year were presence of an aortic fistula (OR, 9.78), perioperative stroke (OR, 5.87), and use of general anesthetic (OR, 3.76); and at 5 years were aortic fistula (OR, 12.31) and increasing age (OR, 1.06). CONCLUSIONS: Acute aortic syndrome carries significant early and late mortality. Emergency endovascular repair offers a minimally invasive treatment option associated with acceptable short and midterm results. Continued surveillance is important as secondary procedures and aortic-related deaths continue to occur throughout the follow-up period.

Highly accurate quartic force fields, vibrational frequencies, and spectroscopic constants for cyclic and linear C3H3(+).

High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C(3)H(3)(+) molecular cation, referred to as c-C(3)H(3)(+) and l-C(3)H(3)(+). Specifically, the singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit, and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants by use of both vibrational second-order perturbation theory and variational methods to solve the nuclear Schrödinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C(3)H(3)(+), obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C(3)H(3)(+) and l-C(3)H(3)(+) are the most reliable available for the free gas-phase species, and it is hoped that these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations.

Endovascular repair of a tuberculous mycotic thoracic aortic aneurysm with a custom-made device.

Mycotic aortic aneurysms are rare and it is unlikely that any center will obtain extensive experience in their management. The aim of treatment is to repair the aorta and eradicate the infection with minimal operative and postoperative risk. We describe a case in which a custom-made endovascular stent graft provided the optimal treatment strategy and remained durable at 4 years of follow-up.

The role of exact exchange in the description of Cu(2+)-(H(2)O)(n) (n = 1-6) complexes by means of DFT methods.

This paper analyses the behavior of different density functionals in the description of the most stable structures of Cu(2+)-(H(2)O)(n) complexes (n = 1-6). From n = 3 to n = 6, different coordination numbers of the metal cation were considered. The structures and energies of the complexes were theoretically determined by means of density functional methods that include different amounts of exact exchange: the BLYP functional (0% of exact exchange), the B3LYP functional (20% of exact exchange), the MPWB1K functional (44% of exact exchange), and BHLYP functional (50% of exact exchange). In addition, CCSD(T) calculations with a large basis set were carried out. It has been found that the functionals with lesser amount of exact exchange, especially BLYP, fail to describe the relative energies between the different structures of each cluster because these functionals tend to overestimate the stability of low-coordinated structures. The inclusion of the exact exchange into the functional improves the results, those obtained with MPWB1K and BHLYP being in very good agreement with the CCSD(T) ones. This behavior is related to the poor description of the second ionization energy of Cu by pure functionals, which leads to a too delocalized spin density in the complex with GGA functionals.

The resolution of the identity approximation for calculations of spin-spin contribution to zero-field splitting parameters.

In this work, the resolution of the identity (RI) approximation is developed for the calculation of the electron-electron spin-spin coupling (SSC) interaction that is a central component of the zero-field splitting (ZFS) term in the effective spin Hamiltonian. The approximated integrals are then used in large-scale multireference configuration interaction treatments of the SSC interaction. The SSC contribution to the ZFS is treated using the Breit-Pauli spin-spin Hamiltonian in conjunction with first-order perturbation theory. Test calculations on a set of diatomic molecules reveal that the error of the RI approximation does not exceed 0.01 cm(-1) even if standard auxiliary basis sets are used. This error of less than 1% is considered to be negligible compared to the presently achievable accuracy of the SSC calculations relative to experimental data. The present development allows the correlated ab initio calculation of ZFS parameters of larger systems such as linear polyenes and linear polyacenes. The basis set convergence of the calculated ZFS values was investigated, and the effect of electronic correlation on the calculated ZFS parameters is discussed.

ALTRUISM: A Higher Calling.

A new robust surface-walking algorithm for locating transition states is presented. By modifying the Trust-Region Image Surface Minimization method to walk to higher-order stationary points, where the Hessian has more than one negative eigenvalue, we have developed an approach that determines transition states from above, by walking downhill on the potential energy surface. We call this algorithm "ALTRUISM"-Alpine Trust-region Image Surface Method. We test the performance of the approach by applying it to a range of systems with several different quantum-chemical methods. Our results demonstrate that ALTRUISM is a systematic, robust, and unbiased method for connecting a reactant and a product via a transition state. The algorithmic combination of walking uphill (to different higher-order stationary points) and downhill to saddle points enables us to explore qualitatively distinct reaction pathways and construct a network of elementary reactions on a given potential energy surface.

Disseminated intravascular coagulation after endovascular aneurysm repair: resolution after aortic banding.

Disseminated intravascular coagulation (DIC) has been shown to affect 2% to 4% of patients with abdominal aortic aneurysms. In rare cases of DIC caused by aneurysms, operative repair has been curative. Endovascular aneurysm repair (EVAR) has been established as an effective treatment. We report a 73-year-old man in whom severe bleeding developed from groin incisions and cannulae sites immediately after EVAR. An intraoperative angiogram showed a type I endoleak, but the procedure had to be abandoned due to continued bleeding. Blood tests confirmed a diagnosis of disseminated intravascular coagulation that persisted chronically 3 months postoperatively. Attempts to repair the endoleak with stenting were unsuccessful, resulting in persistence of disseminated intravascular coagulation. This resolved after successful treatment of the endoleak with aortic banding.

Configurations of equivalent electrons.

We derive here a comprehensive set of formulas for determining the overall spin and spatial symmetry of wave functions arising from a partially filled degenerate orbital. We extend the usual arguments for the case of weak coupling between spin and spatial angular momenta to the jj-coupling case.

On the electron affinity of B2.

We present the results of high-level ab initio calculations on the electron affinity of B(2). Our new best estimate of 1.93 -/+ 0.03 eV is in agreement with previous calculations as well as the sole existing experimental estimate of 1.8 eV, as derived from quantities with an uncertainty of 0.4 eV. The electron affinity of atomic boron, which is much smaller, is also calculated for comparison and again found to be in good agreement with experiment.