Post-prostatectomy adjuvant androgen deprivation therapy- Current opinions and practices of Canadian urologists.

INTRODUCTION: Despite the proven benefit of adjuvant androgen deprivation therapy (ADT) for patients receiving primary radiation, there are few studies evaluating adjuvant ADT after prostatectomy. In the absence of evidence, opinions and practice patterns vary. We surveyed Canadian prostate cancer surgeons about their use of adjuvant ADT and their opinions on the design of a potential adjuvant ADT trial. METHODS: An electronic survey was devised and distributed using a modified Dillman approach. The survey was sent to 38 Canadian urologists that perform radical prostatectomy and representing all 17 major academic institutions in Canada and all 10 Canadian provinces. Reminders were sent three and four weeks following the original request. In addition to demographic information, we asked surgeons about their current use of postoperative adjuvant ADT and their opinion about the need for a clinical trial. To inform trial design, we asked respondents their opinions about which patients should be eligible, what duration of ADT was most appropriate, and which outcomes are clinically meaningful. The survey was sent in February 2020 and all responses were received by March 2020. RESULTS: All 38 (100%) invited urologists completed the survey. Only 3 (7%) respondents currently offer postoperative adjuvant ADT as an option for patients without metastases. 35 (92%) urologists believed that a trial is needed before short-term adjuvant treatment should be offered to prevent recurrence. 15 (45%) urologists believed an adjuvant ADT trial was most appropriate for patients with an estimated PSA recurrence risk of >25% and 16 (42%) believed a recurrence risk of >50% was most appropriate. 25 (66%) respondents believed 12-month was the optimal duration of treatment with adjuvant ADT for a randomized trial. 37 (97%) respondents felt that prolonging the time to PSA recurrence and/or pelvic radiation was a clinically important outcome. The majority (20; 53%) of respondents would recommend 12 months of adjuvant ADT in their practice if a randomized trial showed a 50% relative risk reduction in PSA recurrence at 5-year postoperative. CONCLUSION: The vast majority of Canadian prostate cancer surgeons do not offer adjuvant ADT following prostatectomy in patients without metastases. Based on the results from this survey, a randomized trial was considered warranted and feasible, and would influence patient care.

Infrared spectroscopy of an endohedral water in fullerene.

An infrared absorption spectroscopy study of the endohedral water molecule in a solid mixture of H2O@C60 and C60 was carried out at liquid helium temperature. From the evolution of the spectra during the ortho-para conversion process, the spectral lines were identified as para-H2O and ortho-H2O transitions. Eight vibrational transitions with rotational side peaks were observed in the mid-infrared: ω1, ω2, ω3, 2ω1, 2ω2, ω1 + ω3, ω2 + ω3, and 2ω2 + ω3. The vibrational frequencies ω2 and 2ω2 are lower by 1.6% and the rest by 2.4%, as compared to those of free H2O. A model consisting of a rovibrational Hamiltonian with the dipole and quadrupole moments of H2O interacting with the crystal field was used to fit the infrared absorption spectra. The electric quadrupole interaction with the crystal field lifts the degeneracy of the rotational levels. The finite amplitudes of the pure v1 and v2 vibrational transitions are consistent with the interaction of the water molecule dipole moment with a lattice-induced electric field. The permanent dipole moment of encapsulated H2O is found to be 0.50 ± 0.05 D as determined from the far-infrared rotational line intensities. The translational mode of the quantized center-of-mass motion of H2O in the molecular cage of C60 was observed at 110 cm-1 (13.6 meV).

Singlet-Contrast Magnetic Resonance Imaging: Unlocking Hyperpolarization with Metabolism*.

Hyperpolarization-enhanced magnetic resonance imaging can be used to study biomolecular processes in the body, but typically requires nuclei such as 13 C, 15 N, or 129 Xe due to their long spin-polarization lifetimes and the absence of a proton-background signal from water and fat in the images. Here we present a novel type of 1 H imaging, in which hyperpolarized spin order is locked in a nonmagnetic long-lived correlated (singlet) state, and is only liberated for imaging by a specific biochemical reaction. In this work we produce hyperpolarized fumarate via chemical reaction of a precursor molecule with para-enriched hydrogen gas, and the proton singlet order in fumarate is released as antiphase NMR signals by enzymatic conversion to malate in D2 O. Using this model system we show two pulse sequences to rephase the NMR signals for imaging and suppress the background signals from water. The hyperpolarization-enhanced 1 H-imaging modality presented here can allow for hyperpolarized imaging without the need for low-abundance, low-sensitivity heteronuclei.

Preserving Access: A Review of Stroke Thrombectomy during the COVID-19 Pandemic.

Thrombectomy for large-vessel-occlusion stroke is a highly impactful treatment. The spread of coronavirus 19 (COVID-19) across the United States and the globe impacts access to this crucial intervention through widespread societal and institutional changes. In this document, we review the implications of COVID-19 on the emergency care of large-vessel occlusion stroke, reviewing specific infection-control recommendations, available literature, existing resources, and expert consensus. As a population, patients with large-vessel occlusion stroke face unique challenges during pandemics. These are broad in scope. Responses to these challenges through adaptation of stroke systems of care and with imaging, thrombectomy, and postprocedural care are detailed. Preservation of access to thrombectomy must be prioritized for its public health impact. While the extent of required changes will vary by region, tiered planning for both escalation and de-escalation of measures must be a part of each practice. In addition, preparations described serve as templates in the event of future pandemics.

Multicenter Postmarket Analysis of the Neuroform Atlas Stent for Stent-Assisted Coil Embolization of Intracranial Aneurysms.

BACKGROUND AND PURPOSE: The Neuroform Atlas is a new microstent to assist coil embolization of intracranial aneurysms that recently gained FDA approval. We present a postmarket multicenter analysis of the Neuroform Atlas stent. MATERIALS AND METHODS: On the basis of retrospective chart review from 11 academic centers, we analyzed patients treated with the Neuroform Atlas after FDA exemption from January 2018 to June 2019. Clinical and radiologic parameters included patient demographics, aneurysm characteristics, stent parameters, complications, and outcomes at discharge and last follow-up. RESULTS: Overall, 128 aneurysms in 128 patients (median age, 62 years) were treated with 138 stents. Risk factors included smoking (59.4%), multiple aneurysms (27.3%), and family history of aneurysms (16.4%). Most patients were treated electively (93.7%), and 8 (6.3%) underwent treatment within 2 weeks of subarachnoid hemorrhage. Previous aneurysm treatment failure was present in 21% of cases. Wide-neck aneurysms (80.5%), small aneurysm size (<7 mm, 76.6%), and bifurcation aneurysm location (basilar apex, 28.9%; anterior communicating artery, 27.3%; and middle cerebral artery bifurcation, 12.5%) were common. A single stent was used in 92.2% of cases, and a single catheter for both stent placement and coiling was used in 59.4% of cases. Technical complications during stent deployment occurred in 4.7% of cases; symptomatic thromboembolic stroke, in 2.3%; and symptomatic hemorrhage, in 0.8%. Favorable Raymond grades (Raymond-Roy occlusion classification) I and II were achieved in 82.9% at discharge and 89.5% at last follow-up. mRS ≤2 was determined in 96.9% of patients at last follow-up. The immediate Raymond-Roy occlusion classification grade correlated with aneurysm location (P < .0001) and rupture status during treatment (P = .03). CONCLUSIONS: This multicenter analysis provides a real-world safety and efficacy profile for the treatment of intracranial aneurysms with the Neuroform Atlas stent.

Guidelines for the management of postoperative soiling in children with Hirschsprung disease.

Although most children with Hirschsprung disease ultimately achieve functional and comfortable stooling, some will experience a variety of problems after pull-through surgery. The most common problems include soiling, obstructive symptoms, enterocolitis, and failure to thrive. The purpose of this guideline is to present a rational approach to the management of postoperative soiling in children with Hirschsprung disease. The American Pediatric Surgical Association Hirschsprung Disease Interest Group engaged in a literature review and group discussions. Expert consensus was then used to summarize the current state of knowledge regarding causes, methods of diagnosis, and treatment approaches to children with soiling symptoms following pull-through for Hirschsprung disease. Causes of soiling after pull-through are broadly categorized as abnormalities in sensation, abnormalities in sphincter control, and "pseudo-incontinence." A stepwise algorithm for the diagnosis and management of soiling after a pull-through for Hirschsprung disease is presented; it is our hope that this rational approach will facilitate treatment and optimize outcomes.

Nuclear singlet relaxation by scalar relaxation of the second kind in the slow-fluctuation regime.

The singlet state of nuclear spin-1/2 pairs is protected against many common relaxation mechanisms. Singlet order, which is defined as the population difference between the nuclear singlet and triplet states, usually decays more slowly than the nuclear magnetization. Nevertheless, some decay mechanisms for nuclear singlet order persist. One such mechanism is called scalar relaxation of the second kind (SR2K) and involves the relaxation of additional nuclei ("third spins") which have scalar couplings to the spin-1/2 pair. This mechanism requires a difference between the couplings of at least one third spin with the two members of the spin-1/2 pair, and depends on the longitudinal relaxation time of the third spin. The SR2K mechanism of nuclear singlet relaxation has previously been examined in the case where the relaxation rate of the additional spins is on the time scale of the nuclear Larmor frequency. In this paper, we consider a different regime, in which the longitudinal relaxation of the third spins is on a similar time scale to the J-coupling between the members of the spin pair. This regime is often encountered when the spin-1/2 pair has scalar couplings to nearby deuterium nuclei. We show that the SR2K mechanism may be suppressed in this regime by applying a radiofrequency field which is resonant either with the members of the spin pair, or with the third spins. These phenomena are analyzed theoretically and by numerical simulations, and demonstrated experimentally on a diester of [13C2, 2H2]-labeled fumarate in solution.

A tailored surgical approach to the palpable undescended testis.

INTRODUCTION: Orchiopexy for a palpable undescended testis can be approached through a traditional inguinal incision or trans-scrotally. Despite the possible advantages of the scrotal approach, including reduced postoperative pain and shorter recovery, it is not consistently advocated. OBJECTIVE: The objective of this study was to present the experience with a tailored approach to orchiopexy based on physical findings. STUDY DESIGN: This is an extended case series. MATERIALS AND METHODS: The mobility of the testis as described at examination under anesthesia informs the choice of surgical approach. If a 'low' palpable testis (defined as testis that can be manipulated to the scrotum) was found, a scrotal approach was used. In cases of 'high' palpable testis (testis that cannot be manipulated to scrotum), the inguinal approach was used. Success was defined by location and size of the testis 3 months after surgery. RESULTS: A total of 259 orchiopexies were performed in 181 boys (78 bilateral). Scrotal approach was used in 125 (48%) and inguinal in 134 (52%) orchiopexies. Operative time was significantly shorter for the scrotal approach, 25 min vs. 40 min for inguinal orchiopexy (P < 0.05). The overall success rate was 98% with no statistical difference between the groups. Three children from the inguinal group and two from the scrotal group required an additional procedure for persistent undescended testis. The rates of testicular atrophy and hypotrophic testis were higher in the inguinal group than the scrotal group (5/134 vs. 0/125; P < 0.05 and 17/134 vs. 6/126; P < 0.05, respectively). DISCUSSION: The substantial cohort of patients selected for trans-scrotal orchiopexy experienced success rates and rates of atrophic and hypotrophic testis comparable with those found in the published literature. Furthermore, trans-scrotal operative times were significantly lower than those of inguinal procedures, and less patients required re-operation in the trans-scrotal group. Limitations of this study include significantly higher age at operation in trans-scrotal patients and a difficulty accurately classifying hypotrophic testes. Furthermore, the higher atrophic rate in the inguinal group vs. the scrotal group likely reflects the vulnerability of a testis that is located higher and not the superiority of the scrotal approach. CONCLUSION: This tailored approach to a palpable undescended testis appears simple, safe, and effective, providing high success rate with marginal complications. It is considered a preference in cases of low undescended testis, whereas the standard two-incision inguinal orchiopexy may better serve those with high undescended testis.

Bidirectional band-selective magnetization transfer along the protein backbone doubles the information content of solid-state NMR correlation experiments.

Resonance assignment is the first stage towards solving the structure of a protein. This is normally achieved by the employment of separate inter and intra residue experiments. By utilising the mixed rotation and rotary recoupling (MIRROR) condition it is possible to double the information content through the efficient bidirectional transfer of magnetization from the CO to its adjacent Cα and the Cα of the subsequent amino acid. We have incorporated this into a 3D experiment, a 3D-MIRROR-NCOCA, where correlations present in the 3D spectrum permit the sequential assignment of the protein backbone from a single experiment as we have demonstrated on a microcrystalline preparation of GB3. Furthermore, the low-power requirements of the MIRROR recoupling sequence facilitate the development of a low-power 3D-NCOCA experiment. This has enabled us to realise significant reductions in acquisition times, allowing the acquisition of a single 3D-NCOCA spectrum suitable for a full backbone resonance assignment of GB3 in less than 24 h.

Segmental colonic dilation is associated with premature termination of high-amplitude propagating contractions in children with intractable functional constipation.

BACKGROUND: Colonic dilation is common in children with intractable functional constipation (FC). Our aim was to describe the association between segmental colonic dilation and colonic dysmotility in children with FC. METHODS: We performed a retrospective study on 30 children with intractable FC (according to the Rome III criteria) who had undergone colonic manometry and contrast enema within a 12-month time period. Colonic diameter was measured at 5 cm intervals from the anal verge up to the splenic flexure. Moreover, the distance between the lateral margins of the pedicles of vertebra L2 was measured to provide a ratio (colonic diameter or length/distance between the lateral margins; "standardized colon size" [SCS]). All manometry recordings were visually inspected for the presence of high-amplitude propagating contractions (HAPCs); a parameter for colonic motility integrity. The intracolonic location of the manometry catheter sensors was assessed using an abdominal X-ray. KEY RESULTS: Colonic segments with HAPCs had a significantly smaller median diameter than colonic segments without HAPCs (4.08 cm vs 5.48 cm, P<.001; SCS 1.14 vs 1.66, P=.001). Children with prematurely terminating HAPCs had significantly larger SCS ratios for colonic diameter than children with fully propagating HAPCs (P=.008). SCS ratios for the length of the rectosigmoid and the descending colon and the SCS ratio for sigmoid colon diameter were significantly larger in children with FC compared to a previously described normative population (P<.0001, P<.0001 and P=.0007 respectively). CONCLUSIONS & INFERENCES: Segmental colonic dilation was associated with prematurely terminating HAPCs and may be a useful indicator of colonic dysmotility.

Guidelines for the management of postoperative obstructive symptoms in children with Hirschsprung disease.

Although most children with Hirschsprung disease ultimately do well, many experience a variety of ongoing problems after pull-through surgery. The most common include obstructive symptoms, soiling, enterocolitis and failure to thrive. The purpose of this guideline is to present a rational approach to the management of postoperative obstructive symptoms in children with Hirschsprung disease. The American Pediatric Surgical Association Board of Governors established a Hirschsprung Disease Interest Group. Group discussions, literature review and expert consensus were then used to summarize the current state of knowledge regarding causes, methods of diagnosis, and treatment approaches to children with obstructive symptoms following pull-through for Hirschsprung disease. Causes of obstructive symptoms post-pull-through include mechanical obstruction; persistent or acquired aganglionosis, hypoganglionosis, or transition zone pull-through; internal sphincter achalasia; disordered motility in the proximal intestine that contains ganglion cells; or functional megacolon caused by stool-holding behavior. An algorithm for the diagnosis and management of obstructive symptoms after a pull-through for Hirschsprung disease is presented. A stepwise, logical approach to the diagnosis and management of patients experiencing obstructive symptoms following pull-through for Hirschsprung disease can facilitate treatment. Level of evidence V.

Computational Modeling of Venous Sinus Stenosis in Idiopathic Intracranial Hypertension.

BACKGROUND AND PURPOSE: Idiopathic intracranial hypertension has been associated with dural venous sinus stenosis in some patients, but the hemodynamic environment of the dural venous sinuses has not been quantitatively described. Here, we present the first such computational fluid dynamics model by using patient-specific blood pressure measurements. MATERIALS AND METHODS: Six patients with idiopathic intracranial hypertension and at least 1 stenosis or atresia at the transverse/sigmoid sinus junction underwent MR venography followed by cerebral venography and manometry throughout the dural venous sinuses. Patient-specific computational fluid dynamics models were created by using MR venography anatomy, with venous pressure measurements as boundary conditions. Blood flow and wall shear stress were calculated for each patient. RESULTS: Computational models of the dural venous sinuses were successfully reconstructed in all 6 patients with patient-specific boundary conditions. Three patients demonstrated a pathologic pressure gradient (≥8 mm Hg) across 4 dural venous sinus stenoses. Small sample size precludes statistical comparisons, but average overall flow throughout the dural venous sinuses of patients with pathologic pressure gradients was higher than in those without them (1041.00 ± 506.52 mL/min versus 358.00 ± 190.95 mL/min). Wall shear stress was also higher across stenoses in patients with pathologic pressure gradients (37.66 ± 48.39 Pa versus 7.02 ± 13.60 Pa). CONCLUSIONS: The hemodynamic environment of the dural venous sinuses can be computationally modeled by using patient-specific anatomy and physiologic measurements in patients with idiopathic intracranial hypertension. There was substantially higher blood flow and wall shear stress in patients with pathologic pressure gradients.

Rectal atresia and anal stenosis: the difference in the operative technique for these two distinct congenital anorectal malformations.

Rectal atresia and anal stenosis are rare forms of anorectal malformations. The aim of the definitive surgical repair in such cases is to preserve the anal canal, the dentate line, and the sphincter complex. We present a case of rectal atresia and anal stenosis to demonstrate the differences in the operative repair. The techniques described leave the anterior wall of the very distal anal canal untouched in both rectal stenosis and anal atresia; however, the dissection of the rectum differs. The atretic rectum in rectal atresia is mobilized and sutured to the anal canal circumferentially. In anal stenosis, the posterior rectum is mobilized in the form of rectal advancement, and the posterior 180° is anastomosed directly to the skin (as in a standard PSARP) with preservation of the anal canal as the anterior 180° of the final anoplasty. These patients have an excellent prognosis for bowel control and fecal continence, and therefore, complete mobilization and resection of the anal canal must be avoided.

Posterior Inferior Cerebellar Artery Patency after Flow-Diverting Stent Treatment.

BACKGROUND AND PURPOSE: The rate of PICA occlusion after flow-diverting stent placement for vertebral and vertebrobasilar artery aneurysms is not known. The purpose of this study is to determine the medium-term rate of PICA patency and risk factors for occlusion after such aneurysm treatment. MATERIALS AND METHODS: Patients were identified who had vertebral or vertebrobasilar artery aneurysms and who were treated by placing a flow-diverting stent across the PICA ostium. Demographic and procedural factors associated with stent placement were recorded. Patency of the PICA was evaluated immediately after stent placement and on follow-up angiography. RESULTS: Thirteen patients with vertebral or vertebrobasilar artery aneurysms were treated in the study period, of whom 4 presented with subarachnoid hemorrhage. The average number of devices that spanned the PICA ostium was 1.77 (range, 1-3), with no immediate PICA occlusions. There were no postoperative strokes in the treated PICA territory, although there was 1 contralateral PICA-territory stroke of unclear etiology without clinical sequelae. In 11 patients with follow-up angiography at a mean of 10.6 months (range, 0.67-27.9 months), the PICA patency rate remained 100%. CONCLUSIONS: Flow-diverting stent placement across the PICA ostium in the treatment of vertebral and vertebrobasilar artery aneurysms may not result in immediate or midterm PICA occlusion.

In vitro validation of endovascular Doppler-derived flow rates in models of the cerebral circulation.

This study presents validation of endovascular Doppler velocimetry-based volumetric flow rate measurements conducted in a pulsatile flow loop simulating conditions in both the internal carotid and basilar artery. In vitro models of cerebral vessels, each containing an aneurysm, were fabricated from patient anatomies extracted from 3D rotational angiography. Flow velocity measurements were collected with three different experimental techniques: an endovascular Doppler wire, Particle Image Velocimetry, and a time-resolved ultrasonic flow meter. Womersley's theory of pulsatile flow in a cylindrical vessel was used to compute time-resolved volumetric flow rates from the endovascular Doppler velocity. The volumetric flow rates computed from the Doppler measurements were compared to those from the Particle Image Velocimetry profile measurements, and the direct measurements from the ultrasonic flow meter. The study establishes confidence intervals for any systematic or random errors associated with the wire-derived flow rates as benchmarked to the other two modalities. There is an approximately 10% random error in the Doppler-derived peak and time-averaged flow rates. There is a measurable uniform bias, about 15% too low, in the time-averaged Doppler-derived flow rates. There is also a small proportional bias in the peak systolic Doppler-derived flow rates. Potential sources of error are also discussed.

The Gonzalez hernia revisited: use of the ischiorectal fat pad to aid in the repair of rectovaginal and rectourethral fistulae.

INTRODUCTION: During the development of the posterior sagittal approach to anorectal malformations a vital technical challenge was a precise midline dissection, which if off, allowed for the ischiorectal fat pad to bulge into the wound. This occurrence became affectionately known as a "Gonzalez hernia", after a trainee of Dr Pena's (and a co-author of this paper). We describe here an innovative use of the ischiorectal fat pad to aid in the repair of acquired rectovaginal and rectourethral fistulae. METHODS: Patients with recurrent vaginal or urethral fistulae were selected for review. The ischiorectal fat pad was deliberately mobilized (via a posterior sagittal or transanal approach) and used to buttress the repair of the posterior vagina or urethra. RESULTS: The ischiorectal fat pad technique was used in 9 patients. All had an acquired fistula (6 rectovaginal fistula, 3 rectourethral fistulas). We used the posterior sagittal approach in 7 and in 2 the transanal approach. Six patients had had at least two prior attempts at fistula repair. Six patients had a stoma, and 3 did not. There were no recurrences in greater than six month follow-up. DISCUSSION: The ischiorectal fat pad is easily visualized and mobilized, either via a posterior sagittal or transanal approach, providing excellent coverage with native, well-vascularized tissue, in an area that is difficult to heal. It is an excellent option for recurrent rectovaginal and rectovaginal fistulae and may have other additional creative applications.

Propranolol as first-line treatment in orbital infantile haemangiomas: a case series.

PURPOSE: To highlight the importance of Magnetic Resonance Imaging (MRI) and the use of propranolol as both a final diagnostic tool and adequate treatment for orbital Infantile Haemangiomas (IHs). METHODS: A retrospective study was conducted using a case series of 5 infants diagnosed with orbital IH. All patients presented with progressive unilateral proptosis and were at high risk of developing amblyopia, some had combined swelling of the eyelid, impaired eye movements or exposure keratopathy. Propranolol was administered in an initial dose of 0.6 mg/kg/day orally divided in three daily doses and increased in 4 days to 2.7 mg/kg/day. MRI was performed in all children. RESULTS: Striking MR characteristics of an IH lesion were seen in each of our 5 cases, including the presence of flow voids, high contrast enhancement, hypo-intense T1W signal, iso- to hyper intense T2W signal, and lobulated appearance. All patients showed a quick clinical response to treatment, resulting in significant reduction in tumour size within a range of 1-3 weeks and almost complete regression of the lesion at the end of the treatment schedule. CONCLUSIONS: Our study adds another 5 cases to the growing body of reports confirming the efficacy and safety - under controlled circumstances - of propranolol therapy in orbital IH management, in which we highlight the use of propranolol as both a final diagnostic tool and as an adequate treatment.

Cerebral aneurysms treated with flow-diverting stents: computational models with intravascular blood flow measurements.

BACKGROUND AND PURPOSE: Computational fluid dynamics modeling is useful in the study of the hemodynamic environment of cerebral aneurysms, but patient-specific measurements of boundary conditions, such as blood flow velocity and pressure, have not been previously applied to the study of flow-diverting stents. We integrated patient-specific intravascular blood flow velocity and pressure measurements into computational models of aneurysms before and after treatment with flow-diverting stents to determine stent effects on aneurysm hemodynamics. MATERIALS AND METHODS: Blood flow velocity and pressure were measured in peri-aneurysmal locations by use of an intravascular dual-sensor pressure and Doppler velocity guidewire before and after flow-diverting stent treatment of 4 unruptured cerebral aneurysms. These measurements defined inflow and outflow boundary conditions for computational models. Intra-aneurysmal flow rates, wall shear stress, and wall shear stress gradient were calculated. RESULTS: Measurements of inflow velocity and outflow pressure were successful in all 4 patients. Computational models incorporating these measurements demonstrated significant reductions in intra-aneurysmal wall shear stress and wall shear stress gradient and a trend in reduced intra-aneurysmal blood flow. CONCLUSIONS: Integration of intravascular dual-sensor guidewire measurements of blood flow velocity and blood pressure provided patient-specific computational models of cerebral aneurysms. Aneurysm treatment with flow-diverting stents reduces blood flow and hemodynamic shear stress in the aneurysm dome.

Quantum rotation and translation of hydrogen molecules encapsulated inside C60: temperature dependence of inelastic neutron scattering spectra.

The quantum dynamics of a hydrogen molecule encapsulated inside the cage of a C60 fullerene molecule is investigated using inelastic neutron scattering (INS). The emphasis is on the temperature dependence of the INS spectra which were recorded using time-of-flight spectrometers. The hydrogen endofullerene system is highly quantum mechanical, exhibiting both translational and rotational quantization. The profound influence of the Pauli exclusion principle is revealed through nuclear spin isomerism. INS is shown to be exceptionally able to drive transitions between ortho-hydrogen and para-hydrogen which are spin-forbidden to photon spectroscopies. Spectra in the temperature range 1.6≤T≤280 K are presented, and examples are given which demonstrate how the temperature dependence of the INS peak amplitudes can provide an effective tool for assigning the transitions. It is also shown in a preliminary investigation how the temperature dependence may conceivably be used to probe crystal field effects and inter-fullerene interactions.

Infrared spectroscopy of small-molecule endofullerenes.

Hydrogen is one of the few molecules that has been incarcerated in the molecular cage of C60 to form the endohedral supramolecular complex H2@C60. In this confinement, hydrogen acquires new properties. Its translation motion, within the C60 cavity, becomes quantized, is correlated with its rotation and breaks inversion symmetry that induces infrared (IR) activity of H2. We apply IR spectroscopy to study the dynamics of hydrogen isotopologues H2, D2 and HD incarcerated in C60. The translation and rotation modes appear as side bands to the hydrogen vibration mode in the mid-IR part of the absorption spectrum. Because of the large mass difference of hydrogen and C60 and the high symmetry of C60 the problem is almost identical to a vibrating rotor moving in a three-dimensional spherical potential. We derive potential, rotation, vibration and dipole moment parameters from the analysis of the IR absorption spectra. Our results were used to derive the parameters of a pairwise additive five-dimensional potential energy surface for H2@C60. The same parameters were used to predict H2 energies inside C70. We compare the predicted energies and the low-temperature IR absorption spectra of H2@C70.