Transient Relaxation Research Articles

CPAP-induced Aerophagia May Precipitate Gastroesophageal Reflux

CPAP-induced Aerophagia May Precipitate Gastroesophageal Reflux

Aerophagia May Not Cause Gastroesophageal Reflux

Free AccessCPAPAerophagia May Not Cause Gastroesophageal Reflux Meredith Snapp, M.D., Sunil Sharma, M.D., F.A.A.S.M. Meredith Snapp, M.D. Address correspondence to: Meredith Snapp, M.D., Thomas Jefferson University Hospital, Sleep Disorders Center, 211 South 9th Street, 5th Floor, Philadelphia PA 19107(215) 955-3156(215) 955-9783 E-mail Address: [email protected] or E-mail Address: [email protected] Thomas Jefferson University Hospital, Philadelphia, PA Search for more papers by this author , Sunil Sharma, M.D., F.A.A.S.M. Thomas Jefferson University Hospital, Philadelphia, PA Search for more papers by this author Published Online:June 15, 2013https://doi.org/10.5664/jcsm.2774Cited by:1SectionsPDF ShareShare onFacebookTwitterLinkedInRedditEmail ToolsAdd to favoritesDownload CitationsTrack Citations AboutINTRODUCTIONWith interest we read the findings of Shepherd et al.,1 “Symptoms of Aerophagia are Common in Patients on Continuous Positive Airway Pressure Therapy and are Related to the Presence of Nighttime Gastroesophageal Reflux.” Shepherd et al. examined the prevalence of continuous positive airway pressure (CPAP)-associated aerophagia utilizing patient questionnaires to identify symptoms of gastroesophageal reflux (GER) and aerophagia in CPAP users. One of the authors' conclusions is that the presence of aerophagia symptoms is the strongest predictor of GER symptoms and vice versa. Authors further conclude that aerophagia induced by CPAP may precipitate GER. However, we feel that the authors failed to discuss prior data suggesting evidence to the contrary. The study by Bredenoord et al.2 is especially important as it sheds more light on the connection between aerophagia and GER.In Bredenoord's study, esophageal impedance, pH, and pressure were monitored in patients with and without gastroesophageal reflux disease (GERD) before and after inflation of air into the gastric cavity, an experimental surrogate for physiologic aerophagia. Air infusion increased the incidence of gas reflux; however there was no increase in acid reflux episodes. These findings are supported by Sifrim et al., who also concluded that the liquid component of GER occurred as a primary event and not associated with gas.3 In light of this contradictory evidence, we should be cautious to assume that aerophagia precipitates GER, and in fact the opposite may be true.Furthermore, in data sub-analysis by Shepherd et al., patients with preexisting GER showed no more aerophagia after CPAP than non-GER patients. This finding is also at odds with Bredenoord et al.,2 who reported that in patients with GERD, the rate of belching is 60% higher than healthy subjects. GERD patients may be more prone to belching due to increased air swallows,2 baseline deficiency in lower esophageal sphincter (LES) tone, or increased rate of transient LES relaxation.4 The lack of aerophagia in GERD patients after CPAP raises the question, does CPAP actually improve baseline aerophagia in GERD patients?Given conflicting evidence in the literature regarding the relationship between GER, aerophagia, and CPAP, it may be premature to assume causality among these entities. The directionality of this link has consequences in the way we approach and treat CPAP users with symptoms of aerophagia.DISCLOSURE STATEMENTThis was not an industry supported study. The authors have indicated no financial conflicts of interest.CITATIONSnapp M; Sharma S. Aerophagia may not cause gastroesophageal reflux J Clin Sleep Med 2013;9(6):631.REFERENCES1 Shepherd K, Hillman D, Eastwood PSymptoms of aerophagia are common in patients on continuous positive airway pressure therapy and are related to the presence of nighttime gastroesophageal reflux. J Clin Sleep Med; 2013;9:13-7, 23319899. LinkGoogle Scholar2 Bredenoord A, Weusten B, Timmer R, Smout AAir swallowing, belching, and reflux in patients with gastroesophageal reflux disease. Am J Gastroenterol; 2006;101:1721-6, 16817838. CrossrefGoogle Scholar3 Sifrim D, Silny J, Holloway RHet al.Patterns of gas and liquid reflux during transient lower oesophageal sphincter relaxation: A study using intraluminal electrical impedance. Gut; 1999;44:47-54, 9862825. CrossrefGoogle Scholar4 Kessing BF, Conchillo JM, Bredenoord AJ, Smout AJ, Masclee AAReview article: the clinical relevance of transient lower oesophageal sphincter relaxations in gastro-oesophageal reflux disease. Aliment Pharmacol Ther; 2011;33:650-61, 21219371. CrossrefGoogle Scholar Previous article Next article FiguresReferencesRelatedDetailsCited byCPAP-induced Aerophagia May Precipitate Gastroesophageal RefluxShepherd K, Hillman D and Eastwood P Journal of Clinical Sleep Medicine, Vol. 09, No. 06, (633-634), Online publication date: 15-Jun-2013. Volume 09 • Issue 06 • June 15, 2013ISSN (print): 1550-9389ISSN (online): 1550-9397Frequency: Monthly Metrics History Submitted for publicationMarch 1, 2013Accepted for publicationMarch 1, 2013Published onlineJune 15, 2013 Information© 2013 American Academy of Sleep MedicinePDF download

PTU-052 Long Term outcome of Patients with Reflux Symptoms and Symptomatic Esophageal Dysfunction during and after a Standardized Test Meal:a High-Resolution Manometry Study

IntroductionRecently we presented novel methodology for the assessment of oesophageal function and symptoms during and after a standard test meal.1 In the absence of a “gold standard”, outcome data provides...

PTH-172 Outcome Assessment of the First Two Years of a New Oesophageal High Resolution Manometry Unit within a District General Hospital

IntroductionOesophageal high resolution manometry (OHRM) is a fast developing area of medicine. Whilst seemingly being at the “cutting edge” of technological advancement, it is a relatively simple procedure to perform...

OC-044 Effects of Sleeve Gastrectomy on Gastro-Oesophageal Reflux and Oesophago-Gastric Motility

Introduction Sleeve gastrectomy is increasingly used as both a definitive and staggered weight loss procedure. The effect of sleeve gastrectomy on gastro-oesophageal reflux (GOR) remains uncertain. We studied the effect of sleeve gastrectomy on GOR, pressure parameters at the Lower Oesophageal Sphincter (LOS), oesophageal and gastric motility. Methods Sixteen patients (median age 46 (range 25–71)) with morbid obesity underwent high resolution oesophageal manometry and 24hr ambulatory pH-impedance monitoring, at least 2 weeks pre-op and 3 months post sleeve gastrectomy (median no. of days post-op 129 (range 84–202)). All patients documented reflux and dysphagia symptoms at the time of testing. Nine patients also underwent concurrent gastric emptying with 13C labelled octanoate breath test. Parametric data was analysed using the paired t-test and non-parametric data with Wilcoxon matched pairs test. Results Mean Body Mass Index (BMI) fell from 49 (41.3–58.3) to 38.5(35–46.3). 5/16 patients reported new or worsening reflux symptoms (31%). Basal LOS pressure fell from 14.4mmHg (9.7–28.5) pre-op to 8.9mmHg (0.7–40.5) post-op (p Conclusion Both acid and non-acid gastro-oesophageal reflux is increased after sleeve gastrectomy with 31% of patients developing de novo acid reflux post-op. This is despite a reduction in BMI and accelerated gastric emptying. A reduction in LOS pressure and increased G-O pressure gradient are likely to be contributing factors. Future studies should determine whether decreased gastric compliance stimulates increased numbers of transient lower oesophageal sphincter relaxations. Disclosure of Interest None Declared

Randomised clinical trial: arbaclofen placarbil in gastro‐oesophageal reflux disease – insights into study design for transient lower sphincter relaxation inhibitors

Arbaclofen placarbil is a pro-drug of the gamma-aminobutyric acid-B agonist R-baclofen that has been shown to reduce reflux episodes in patients with gastro-oesophageal reflux disease (GERD). To evaluate the efficacy and safety of arbaclofen placarbil vs. placebo as adjunctive therapy in subjects with troublesome GERD symptoms despite therapy with once-daily doses of a proton pump inhibitor (PPI) and to identify the characteristics of patients who were responders. Patients (n = 460) with symptomatic GERD experiencing troublesome symptoms on once-daily PPI therapy were enrolled in this phase II, randomised, multicentre, double-blind, placebo-controlled, dose-ranging study. Patients were randomised to receive placebo or arbaclofen placarbil (20 or 40 mg once daily, 20 or 30 mg twice daily) with their current PPI for 6 weeks. Patients recorded heartburn and other GERD symptoms in a daily diary and rated severity of each event. The primary endpoint was percent change from baseline in heartburn events per week. In the primary analysis, there was no significant difference between arbaclofen placarbil and placebo. Post hoc analyses removing mild and very mild heartburn events resulted in greater percent reductions for all arbaclofen placarbil doses with nominal P values <0.05 for each dose compared with placebo. There was a dose-related increase for the most common adverse events. Arbaclofen placarbil was not superior to placebo in the primary analysis. Post hoc analyses suggest that subjects with more clinically relevant moderate or severe symptoms are more likely to respond to arbaclofen placarbil (clinicaltrials.gov NCT00978016).

A study of pathophysiological factors associated with gastro‐esophageal reflux disease in twins discordant for gastro‐esophageal reflux symptoms

Differences in lower esophageal sphincter (LES) and peristaltic function and in transient LES relaxations (TLESR) have been described in patients with gastro-esophageal reflux disease (GERD). However, some of these differences may be the result of chronic GERD rather than being an underlying contributory factor. Twins discordant for GERD symptoms, i.e., only one twin had GERD symptoms, underwent standard LES and esophageal body manometry, and then using a sleeve sensor prolonged LES and pH monitoring, 30 min before and 60 min after a 250 mL 1200 kcal lipid meal. Eight monozygotic and 24 dizygotic female twins were studied. Although there was no difference in preprandial LES pressure (symptomatic 13.2 ± 7.1 mmHg vs asymptomatic 15.1 ± 6.2 mmHg, P = 0.4), LES pressure fell further postprandially in symptomatic twins (LES pressure area under the curve 465 ± 126 vs 331 ± 141 mmHg h, P < 0.01). 12/37 (32%) of acid reflux episodes in symptomatic twins occurred due to low LES pressure or deep inspiration/strain and 0/17 in asymptomatic twins (P = 0.01). There was no difference between symptomatic and asymptomatic twins in: peristaltic amplitude, ineffective esophageal body motility, hiatus hernia prevalence, or LES length. There was also no difference in TLESR frequency preprandially (symptomatic median 1(range 0-2) vs asymptomatic 0(0-2), P = 0.08) or postprandially (2.5(1-8) vs 3(1-6), P = 0.81). Twins with GERD symptoms had lower postprandial LES pressure and given the close genetic link between the twins, it is possible that such differences are caused by GERD. Acid reflux episodes associated with a hypotensive LES were seen in symptomatic, but not in asymptomatic twins.

Spherical indentation analysis of stress relaxation for thin film viscoelastic materials

The mechanical testing of thin layers of soft materials is an important but difficult task. Spherical indentation provides a convenient method to ascertain material properties whilst minimising damage to the material by allowing testing to take place in situ. However, measurement of the viscoelastic properties of these soft materials is hindered by the absence of a convenient yet accurate model which takes into account the thickness of the material and the effects of the underlying substrate. To this end, the spherical indentation of a thin layer of viscoelastic solid material is analysed. It is assumed that the transient mechanical properties of the material can be described by the generalised standard linear solid model. This model is incorporated into the theory and then solved for the special case of a stress relaxation experiment taking into account the finite ramp time experienced in real experiments. An expression for the force as a function of the viscoelastic properties, layer thickness and indentation depth is given. The theory is then fitted to experimental data for the spherical indentation of poly(dimethyl)siloxane mixed with its curing agent to the ratios of 5:1, 10:1 and 20:1 in order to ascertain its transient shear moduli and relaxation time constants. It is shown that the theory correctly accounts for the effect of the underlying substrate and allows for the accurate measurement of the viscoelastic properties of thin layers of soft materials.

Ultrafast dynamics in NiFe alloy thin films by two times of transient reflection

The femtosecond optical pumped transient reflection technique is an effective tool to investigate the ultrafast dynamics in metal thin films. In this paper, both the transient reflectivity response and nonequilibrium relaxation time of electron–phonon interaction in NiFe alloy thin films are studied by using femtosecond laser pump–probe transient reflection experimental technology. The result shows that the heating time of NiFe thin films with different thickness is independent of the thickness of the films, while the thermalization time by electron–phonon relaxation from nonequilibrium state to equilibrium state is proportional to the thickness of the films. In addition, two transient reflectivity signals on glass substrate films are found which is different with previous researches.

An experimental and theoretical analysis of unconfined compression of corneal stroma

The cornea is a transparent connective tissue with dual functions of protecting the eye (mechanical properties) and refracting the light (optical properties). Both of these properties are derived from the corneal intricate and pseudo regular extracellular matrix, the stroma. From the mechanics point of view, the corneal extracellular matrix is a hydrated structure composed of collagen fibrils, proteoglycans, and the interstitial fluid. The objective of this study was to investigate compressive biomechanical properties of the cornea using an experimental and numerical framework. The unconfined compression stress-relaxation tests were performed to measure the corneal behavior experimentally and the transversely isotropic biphasic theory was used to analyze the experimental data. It was observed that the behavior of the corneal stroma under stepwise stress-relaxation compression is similar to that of the other soft hydrated tissues and is composed of an immediate stiff response, a transient relaxation phase, and a final steady-state stage. Within the range of deformation considered in this study, maximum and equilibrium reaction stresses were linearly dependent on the compressive strain. The linear transversely isotropic biphasic model curve fitted experimental measurements with the coefficient of determination rfit2=0.98±0.01. The mechanical parameters of the porcine corneal stroma were calculated as a function of the engineering strain. The corneal out-of-plane modulus was almost independent of the compressive strain, the transverse Young's modulus linearly increased with increasing strain, and the permeability coefficient decayed exponentially with increasing strain. The average mechanical parameters under unconfined compression were found to be: the out-of-plane modulus E¯z=5.61KPa, the transverse Young's modulus E¯r=1.33MPa, and the permeability coefficient κ¯r=2.14×10−14m4/N.s.

Mo2109 Characterization of Transient Anal Sphincter Relaxations (TASRs) Health Using High Resolution Anorectal Manometry: Redefining the Sampling Reflex?

Objective Intact anorectal function is integral to the maintenance of faecal continence. Anal ‘sampling' describes the process by which intermittent relaxation of the anal canal allows detection of rectal contents. Previous studies report such events to be subliminal; however data capture was limited by obsolete technology necessitating retrospective analysis. With the advent of high-resolution anorectal manometry (HRAM), this study aimed to re-evaluate the phenomenon of transient anal sphincter relaxations (TASRs) in healthy volunteers. Methods Twenty-one healthy volunteers (16 F;median age 34, range 22-69) without anorectal dysfunction underwent HRAM using a solid-state catheter incorporating 11 channels, spaced at 8 mm intervals. The study was performed in the sitting position for 45 minutes preand post consumption of a standardizedmeal (828 kcal; 48 g fat). Participants reported perception of any gastrointestinal / anorectal sensations in real-time. TASRs were defined as an equalization of rectal and anal pressures involving ≥20% of the anal canal. Characterization of anorectal pressures changes, event duration and association with perception were recorded. Statistical analysis utilized Wilcoxon matched pairs and Mann Whitney U tests. Results TASRs occurred more frequently following meal consumption (median 3 [IQR 1-6] vs. 0 [0-1]; P=0.01). Median TASR duration was 23 seconds [19-27] and involved a 44% reduction in average anal canal pressure (65 mmHg [53-81] before vs. 36 [28-44] during; P=0.0001). TASRs were accompanied by a 45% increase in rectal pressure (18 mmHg [15-23] before vs. 25 [19-33] during; P=0.001). Fifty-six percent were temporally associated with gastrointestinal / anorectal sensations, most commonly the urge to pass wind (74% perceived events). Perceived TASRs involved a greater length of the anal canal (62% of total length with perceived vs. 53% not perceived; P=0.005). Conclusion To the authors' knowledge, this is the first prolonged study of anorectal function usingHRAM. TASRs are uncommon preprandially and occur more frequently following meal consumption. Contrary to previous reports, the majority of TASRs are perceived, associated with the urge to pass wind. Alteration of TASR characteristics and relation to sensory perception may be important in the pathophysiology of colorectal disorders (e.g. incontinence); such studies, including the effect of intervention are ongoing.

Mo2110 Assessment of Chymase Inhibition on Acute restraint Stress-Induced Visceral Hypersensitivity and Intestinal Dysfunction In Vivo.

Objective Intact anorectal function is integral to the maintenance of faecal continence. Anal ‘sampling' describes the process by which intermittent relaxation of the anal canal allows detection of rectal contents. Previous studies report such events to be subliminal; however data capture was limited by obsolete technology necessitating retrospective analysis. With the advent of high-resolution anorectal manometry (HRAM), this study aimed to re-evaluate the phenomenon of transient anal sphincter relaxations (TASRs) in healthy volunteers. Methods Twenty-one healthy volunteers (16 F;median age 34, range 22-69) without anorectal dysfunction underwent HRAM using a solid-state catheter incorporating 11 channels, spaced at 8 mm intervals. The study was performed in the sitting position for 45 minutes preand post consumption of a standardizedmeal (828 kcal; 48 g fat). Participants reported perception of any gastrointestinal / anorectal sensations in real-time. TASRs were defined as an equalization of rectal and anal pressures involving ≥20% of the anal canal. Characterization of anorectal pressures changes, event duration and association with perception were recorded. Statistical analysis utilized Wilcoxon matched pairs and Mann Whitney U tests. Results TASRs occurred more frequently following meal consumption (median 3 [IQR 1-6] vs. 0 [0-1]; P=0.01). Median TASR duration was 23 seconds [19-27] and involved a 44% reduction in average anal canal pressure (65 mmHg [53-81] before vs. 36 [28-44] during; P=0.0001). TASRs were accompanied by a 45% increase in rectal pressure (18 mmHg [15-23] before vs. 25 [19-33] during; P=0.001). Fifty-six percent were temporally associated with gastrointestinal / anorectal sensations, most commonly the urge to pass wind (74% perceived events). Perceived TASRs involved a greater length of the anal canal (62% of total length with perceived vs. 53% not perceived; P=0.005). Conclusion To the authors' knowledge, this is the first prolonged study of anorectal function usingHRAM. TASRs are uncommon preprandially and occur more frequently following meal consumption. Contrary to previous reports, the majority of TASRs are perceived, associated with the urge to pass wind. Alteration of TASR characteristics and relation to sensory perception may be important in the pathophysiology of colorectal disorders (e.g. incontinence); such studies, including the effect of intervention are ongoing.

Tu1787 Primary Peristalsis and Esophagigastric Junction (EGJ) Pressure, Following a Transient Lower Esophageal Sphincter Relaxation (TLESR), Are Accompanied by a Forceful Contraction

Background: A TLESR is a major mechanism of acid reflux in healthy subjects and patients with reflux esophagitis and we have noticed that the amplitude of primary peristalsis and EGJ pressure, following a TLESR, is accompanied by a forceful contraction, when compared with before a TLESR. The aim of this study is to investigate whether or not primary peristalsis and EGJ pressure, when accompanied by a forceful contraction and following a TLESR, is a characteristic finding of a TLESR. Methods: 10 healthy subjects underwent esophageal high-resolution manometry with a 21-lumen perfused assembly, which monitored pressure in the pharynx, the upper esophageal sphincter, the esophageal body, LES and the proximal stomach. The EGJ was evaluated using ten side holes, spaced at 1-cm intervals. Recordings were then taken, in the sitting position, for 1 hour after a meal (692 kcal, 33 % fat). A TLESR is defined as previously described. Data were analyzed, using Trace! Software (Dr. G.S Hebbard, The Royal Melbourne Hospital, Australia). The contractile integral (CI) of the distal esophageal segment (D-CI: volume of the domain above 20 mmHg), excluding the EGJ segment, was measured both before and after a TLESR, and the CI of the EGJ (EGJCI) (volume of the domain above 0 mmHg), was measured for 8 seconds after primary peristalsis reached the EGJ, both before and after a TLESR. Results: 56 TLESRs were measured during the study. The D-CI (1603 mmHg s cm (1177-2120), median (interquartile range)) following a TLESR was significantly greater than before a TLESR (484 (323-1079)) and more than a 50% increase of D-CI in 35 (62.5%) of the 56 TLESRs was observed. The EGJCI (790 (465-1009)) following a TLESR was significantly greater than before a TLESR (238 (186-308)) and more than a 50% increase in the EGJ-CI in 48 (85.7%) of the 56 TLESRs was observed. Conclusions: The D-CI and the EGJ-CI following a TLESR, were significantly greater than before a TLESR and this tendency was evident in the EGJ-CI, although it can, at times, be difficult to evaluate a TLESR. If the focus is on a forceful contraction of primary peristalsis or on the EGJ, it may be easier to detect and evaluate a TLESR.

Probing relaxation times in graphene quantum dots

Graphene quantum dots are attractive candidates for solid-state quantum bits. In fact, the predicted weak spin-orbit and hyperfine interaction promise spin qubits with long coherence times. Graphene quantum dots have been extensively investigated with respect to their excitation spectrum, spin-filling sequence and electron-hole crossover. However, their relaxation dynamics remain largely unexplored. This is mainly due to challenges in device fabrication, in particular concerning the control of carrier confinement and the tunability of the tunnelling barriers, both crucial to experimentally investigate decoherence times. Here we report pulsed-gate transient current spectroscopy and relaxation time measurements of excited states in graphene quantum dots. This is achieved by an advanced device design that allows to individually tune the tunnelling barriers down to the low megahertz regime, while monitoring their asymmetry. Measuring transient currents through electronic excited states, we estimate a lower bound for charge relaxation times on the order of 60–100 ns.

A Case of Rumination Documented by Using High-resolution Impedance Manometry

A 40-year-old male with normal intelligence was referred for oral malodor. He first noticed his oral malodor because his wife had pointed out his bad breath about 7 years ago. He undertook some periodontal treatment such as scaling. His medical history was unremarkable. Esophagogastroduodenoscopy was performed and then revealed reflux esophagitis of minimal changes. His primary care physician started treatment with pantoprazole and mosapride. However, his oral malodor did not decrease. The patient reported frequent postprandial regurgitation and reswallowing of the regurgitated material. Under the clinical impression of rumination syndrome, high-resolution impedance manometry (HRIM) was performed after the patient was provided with some meal. HRIM revealed reflux event that was associated with an increase in intragastric pressure (gastric strain), which was compatible with rumination (Figure). The patient was instructed to take inspiratory and expiratory breaths with the abdominal muscles, keeping the chest motionless. He was encouraged to practice the diaphragmatic breathing during and after eating. He also was given baclofen of 10 mg preprandially for 4 weeks. He eventually reported decreased frequency of regurgitation and heard improved oral malodor from his wife 8 weeks later. Figure High-resolution impedance manometry of a patient with rumination syndrome. Two rumination episodes (black arrows) are observed as a rise in the intragastric pressure on the high-resolution manometry color plot associated with retrograde intra-esophageal ... HRIM is useful to diagnose rumination especially in case of diagnostic uncertainty or poor patient's acceptance on a possible diagnosis.1 Diaphragmatic breathing is known as the mainstay of treatment. Baclofen is reported to increase postprandial pressure of lower esophageal sphincter and to inhibit transient lower esophageal sphincter relaxations.2 Therefore baclofen is considered to be potentially beneficial in the treatment of rumination.3

Longitudinal Muscle Dysfunction in Achalasia Esophagus and Its Relevance

Muscularis propria of the esophagus is organized into circular and longitudinal muscle layers. Goal of this review is to summarize the role of longitudinal muscle in physiology and pathophysiology of esophageal sensory and motor function. Simultaneous manometry and ultrasound imaging that measure circular and longitudinal muscle contraction respectively reveal that during peristalsis 2 layers of the esophagus contract in perfect synchrony. On the other hand, during transient relaxation of the lower esophageal sphincter (LES), longitudinal muscle contracts independently of circular muscle. Recent studies provide novel insights, i.e., longitudinal muscle contraction of the esophagus induces LES relaxation and possibly descending relaxation of the esophagus. In achalasia esophagus and other motility disorders there is discoordination between the 2 muscle layers. Longitudinal muscle contraction patterns are different in the recently described three types of achalasia identified by high-resolution manometry. Robust contraction of the longitudinal muscle in type II achalasia causes pan-esophageal pressurization and is the mechanism of whatever little esophageal emptying that take place in the absence of peristalsis and impaired LES relaxation. It may be that preserved longitudinal muscle contraction is also the reason for superior outcome to medical/surgical therapy in type II achalasia esophagus. Prolonged contractions of longitudinal muscles of the esophagus is a possible mechanism of heartburn and "angina like" pain seen in esophageal motility disorders and possibly achalasia esophagus. Novel techniques to record longitudinal muscle contraction are on the horizon. Neuro-pharmacologic control of circular and longitudinal muscles is different, which provides an important opportunity for the development of novel pharmacological therapies to treat sensory and motor disorders of the esophagus.

Nonlinear Absorption Dynamics Using Field‐Induced Surface Hopping: Zinc Porphyrin in Water

We wish to present the application of our field-induced surface-hopping (FISH) method to simulate nonlinear absorption dynamics induced by strong nonresonant laser fields. We provide a systematic comparison of the FISH approach with exact quantum dynamics simulations on a multistate model system and demonstrate that FISH allows for accurate simulations of nonlinear excitation processes including multiphoton electronic transitions. In particular, two different approaches for simulating two-photon transitions are compared. The first approach is essentially exact and involves the solution of the time-dependent Schrödinger equation in an extended manifold of excited states, while in the second one only transiently populated nonessential states are replaced by an effective quadratic coupling term, and dynamics is performed in a considerably smaller manifold of states. We illustrate the applicability of our method to complex molecular systems by simulating the linear and nonlinear laser-driven dynamics in zinc (Zn) porphyrin in the gas phase and in water. For this purpose, the FISH approach is connected with the quantum mechanical-molecular mechanical approach (QM/MM) which is generally applicable to large classes of complex systems. Our findings that multiphoton absorption and dynamics increase the population of higher excited states of Zn porphyrin in the nonlinear regime, in particular in solution, provides a means for manipulating excited-state properties, such as transient absorption dynamics and electronic relaxation.

Calibration of an optical tweezer microrheometer by sequential impulse response

We report a robust method for calibrating optical tweezers in any viscoelastic medium. This approach uses two coupled measurements—one from a static experiment in which a trapped particle diffuses passively within the tweezer's harmonic potential and another from a dynamic experiment in which the trap is jumped discontinuously to a new position while the particle undergoes transient relaxation back into the minimum of the optical potential. Together, these are sufficient to determine the stiffness of the trap in a material of unknown rheology. The method is tested in a Newtonian fluid and compares favorably with other means of calibration. The calibration is also per- formed in a non-Newtonian fluid of which standard optical tweezer calibration methods may struggle to characterize. The correctly calibrated optical tweezer microrheometer measures the rheology of polymer solutions in agreement with macrorheological measurements.

Entropy production in quantum Brownian motion

We investigate how to coherently define entropy production for a process of transient relaxation in the quantum Brownian motion model for the harmonic potential. We compare a form, referred to as ‘poised’ (P), which after non-Markovian transients corresponds to a definition of heat as the change in the system Hamiltonian of mean force, with a recent proposal by Esposito et al (ELB) based on a definition of heat as the energy change in the bath. Both expressions yield a positive-definite entropy production and they coincide for vanishing coupling strength, but their difference is proved to be always positive (after non-Markovian transients disappear) and to grow as the coupling strength increases. In the classical over-damped limit the ‘poised’ entropy production converges to the entropy production used in stochastic thermodynamics. We also investigate the effects of the system size, and of the ensuing Poincaré recurrences, and how the classical limit is approached. We close by discussing the strong-coupling limit, in which the ideal canonical equilibrium of the bath is violated.

Presentation, Diagnosis, and Management of Achalasia

Presentation, Diagnosis, and Management of Achalasia