Spin Echo, Fidelity, and the Quantum Critical Fan in TmVO_{4}.

Using spin-echo nuclear magnetic resonance in the model transverse field Ising system TmVO_{4}, we show that low frequency quantum fluctuations at the quantum critical point have a very different effect on ^{51}V nuclear spins than classical low-frequency noise or fluctuations that arise at a finite temperature critical point. Spin echoes filter out the low-frequency classical noise but not the quantum fluctuations. This allows us to directly visualize the quantum critical fan and demonstrate the persistence of quantum fluctuations at the critical coupling strength in TmVO_{4} to high temperatures in an experiment that remains transparent to finite temperature classical phase transitions. These results show that while dynamical decoupling schemes can be quite effective in eliminating classical noise in a qubit, a quantum critical environment may lead to rapid entanglement and decoherence.

Unusual Interplay between Superconductivity and Field-Induced Charge Order in YBa_{2}Cu_{3}O_{y}.

We present a detailed study of the temperature (T) and magnetic field (H) dependence of the electronic density of states (DOS) at the Fermi level, as deduced from specific heat and Knight shift measurements in underdoped YBa_{2}Cu_{3}O_{y}. We find that the DOS becomes field independent above a characteristic field H_{DOS}, and that the H_{DOS}(T) line displays an unusual inflection near the onset of the long-range 3D charge-density wave order. The unusual S shape of H_{DOS}(T) is suggestive of two mutually exclusive orders that eventually establish a form of cooperation in order to coexist at low T. On theoretical grounds, such a collaboration could result from the stabilization of a pair-density wave state, which calls for further investigation in this region of the phase diagram.

Quasiparticle Scattering off Defects and Possible Bound States in Charge-Ordered YBa_{2}Cu_{3}O_{y}.

We report the NMR observation of a skewed distribution of ^{17}O Knight shifts when a magnetic field quenches superconductivity and induces long-range charge-density-wave (CDW) order in YBa_{2}Cu_{3}O_{y}. This distribution is explained by an inhomogeneous pattern of the local density of states N(E_{F}) arising from quasiparticle scattering off, yet unidentified, defects in the CDW state. We argue that the effect is most likely related to the formation of quasiparticle bound states, as is known to occur, under specific circumstances, in some metals and superconductors (but not in the CDW state, in general, except for very few cases in 1D materials). These observations should provide insight into the microscopic nature of the CDW, especially regarding the reconstructed band structure and the sensitivity to disorder.

Using strain to uncover the interplay between two- and three-dimensional charge density waves in high-temperature superconducting YBa2Cu3Oy.

Uniaxial pressure provides an efficient approach to control charge density waves in YBa2Cu3Oy. It can enhance the correlation volume of ubiquitous short-range two-dimensional charge-density-wave correlations, and induces a long-range three-dimensional charge density wave, otherwise only accessible at large magnetic fields. Here, we use x-ray diffraction to study the strain dependence of these charge density waves and uncover direct evidence for a form of competition between them. We show that this interplay is qualitatively described by including strain effects in a nonlinear sigma model of competing superconducting and charge-density-wave orders. Our analysis suggests that strain stabilizes the 3D charge density wave in the regions between disorder-pinned domains of 2D charge density waves, and that the two orders compete at the boundaries of these domains. No signatures of discommensurations nor of pair density waves are observed. From a broader perspective, our results underscore the potential of strain tuning as a powerful tool for probing competing orders in quantum materials.

Inverse Laplace transformation analysis of stretched exponential relaxation.

We investigate the effectiveness of the Inverse Laplace Transform (ILT) analysis method to extract the distribution of relaxation rates from nuclear magnetic resonance data with stretched exponential relaxation. Stretched-relaxation is a hallmark of a distribution of relaxation rates, and an analytical expression exists for this distribution for the case of a spin-1/2 nucleus. We compare this theoretical distribution with those extracted via the ILT method for several values of the stretching exponent and at different levels of experimental noise. The ILT accurately captures the distributions for ß≲0.7, and for signal to noise ratios greater than ∼40; however the ILT distributions tend to introduce artificial oscillatory components. We further use the ILT approach to analyze stretched relaxation for spin I>1/2 and find that the distributions are accurately captured by the theoretical expression for I=1/2. Our results provide a solid foundation to interpret distributions of relaxation rates for general spin I in terms of stretched exponential fits.

Rectal mucosal biopsy in aganglionosis and allied conditions.

Rectal mucosal biopsies were performed in 146 patients suspected of having Hirschsprung's disease. The biopsies were serially sectioned and screened for the presence of ganglion cells. In the 101 cases in which ganglion cells were found, the diagnosis of Hirschsprung's disease was ruled out. In 45 patients, histologic examination revealed the typical features of Hirschsprung's disease, i.e., the absence of ganglion cells and the presence of numerous hypertrophied nerve bundles. The varied morphologic features of Meissner's plexus in patients of different ages and the diagnostic pitfalls are described in detail. Serial frozen sections stained with hematoxylin-eosin were examined in eight cases of neonatal intestinal obstruction and enterocolitis. This method was found to be useful and reliable in emergencies. In three of these cases ganglion cells were found and major surgical procedures were avoided. In 73 cases, staining for acetylcholinesterase activity was performed. The results matched the microscopic findings in all but three false-positive cases.

Crohn's disease isolated to the appendix: truths and fallacies.

Twenty-five cases of Crohn's disease confined to the appendix were reported in eight hospitals in Israel during a 15-year period. Review of the histologic slides confirmed the diagnosis in 22 cases. Re-evaluation of these 22 patients included physical examination and radiologic studies of the small and large bowel. Rectosigmoidoscopy was performed in 16 patients. Signs and symptoms of Crohn's disease at other sites in the gastrointestinal tract did not occur during follow-up periods of two to 15 years (mean, 6.4 years) after appendectomy. This study and a review of the literature indicate that in most cases (93 per cent) Crohn's disease initially limited to the appendix is not a predictor of subsequent involvement of another portion of the bowel. It is concluded that the so-called Crohn's disease isolated to the appendix is a form of chronic granulomatous and follicular appendicitis of unknown etiology that is unrelated nosologically in the majority of the cases to Crohn's disease proper.

A new intratracheal stent made from nitinol, an alloy with "shape memory effect".

Temporary or permanent tracheal splinting in pediatric patients may be indicated in tracheomalacia or bronchomalacia, repair of congenital tracheal stenosis, and after tracheal resection. This study presents the results of the development of a new intraluminal airway stent made from titanium alloy, a metal with "shape memory effect". At low temperatures (martensitic state) the titanium alloy stent can be fashioned into a specific shape; then when heated to a higher temperature (austenitic state) the stent alters its shape, only to regain its original shape when recooled to the lower temperature. The stent, connected to a small electric power supply, was introduced into 20 young rabbits with the use of a 2.5 cm rigid bronchoscope. After implantation in the martensitic state the stent was warmed to 40 degrees C, the austenitic state, by an electric current of 1.5 to 3 ampere for 1 to 2 seconds. After a period of 8 to 10 weeks the stent was removed (in its martensitic state) through the same-sized bronchoscope after being cooled with 3 to 4 ml of 80% alcohol solution at 6 degrees C. No signs of airway obstruction developed in any of the animals after implantation or extraction of the stent. The biomechanical properties of the trachea, as shown by strain measurements with the use of incremental forces, showed significant differences between the stented and unstented segments (p < 0.005). The titanium alloy intratracheal stent adequately fulfilled the requirements of a temporary intraluminal airway splint, and because of its unique feature of shape memory effect the stent could be inserted, fixed, and removed easily, even in very small airways.

Acute appendicitis following abdominal trauma.

Acute appendicitis (AA) is generally considered to be a consequence of lumenal obstruction and inflammation of the appendix. At the beginning of the 20th century, trauma was considered to be one of the possible causes of AA but this relationship has not been examined much since then. Our experience with three cases of AA following blunt abdominal trauma led to an extensive review of the world literature on the subject. We believe that abdominal trauma might be causative of AA. The potential for this hazardous and easily missed diagnostic entity should be appreciated in cases of blunt abdominal trauma both for sound clinical decision making and for its potential medical and legal implications.

Nissen fundoplication in the treatment of children with familial dysautonomia.

Thirty-four children with familial dysautonomia (FD) underwent Nissen fundoplication and gastrostomy. The indications for operation were persistent cyclic vomiting that resulted in repeated aspiration pneumonia (94% of the patients), chronic dehydration (82%), failure to thrive (97%), and frequent hospitalizations (76%). There was no operative or early postoperative mortality. Long-term follow-up for up to 12 years was available. Eight patients died during this period from 7 months to 7.5 years postoperatively. In 5 patients (15% of the operated patients), the fundoplication ceased to function 16 months to 5 years postoperatively, which was attributed mainly to repeated severe dysautonomic crises with vigorous retching. Vomiting ceased in 85% of the symptomatic patients; pulmonary deterioration was halted, and the frequency of aspiration pneumonia was reduced in 68%; nutritional improvement was seen in 44%; the hydration status improved in 88%; and the frequency of hospital admissions decreased in 74%. These long-term findings resulted in a significant improvement in the quality of life for the majority of the patients. The absence of operative mortality and the low postoperative morbidity, together with the long-term beneficial results of this surgical procedure, should encourage early surgical intervention in selected FD patients.

Short note: the potential of umbilical cord blood to increase tissue oxygenation in adult respiratory distress syndrome.

Umbilical blood, consisting mainly of fetal haemoglobin, has an increased oxygen affinity. Adult respiratory distress syndrome may be caused by any acute, diffuse, infiltrative lung lesion of diverse aetiologies and is characterized by severe arterial hypoxia. Mechanical ventilation with high FIO2 and elevated pressures is used to improve tissue oxygenation in these patients. Nevertheless, adult respiratory distress syndrome may be fatal. Our hypothesis suggests that transfusion of umbilical cord blood to adult respiratory distress syndrome patients may facilitate oxygen transport by increasing oxygen binding in the erythrocytes passing through the damaged lungs. The local hypoxia and the accompanied acidosis in the periphery may accelerate the oxygen unload to the tissues, thus augmenting overall oxygen delivery. Studies with animals and humans show that left-shifted oxyhaemoglobin dissociated curve confers a degree of adaptation to low-oxygen tension ambient. Umbilical cord blood is available in every hospital, and there are no contraindications to its use.

Long-term functional results of prosthetic airway splinting in tracheomalacia and bronchomalacia.

The long-term functional results of splinting a collapsing major airway with a silastic Marlex mesh prosthesis were assessed. Six patients in whom follow-up has been longer than 4 years (mean 5.3 years) were studied. The prosthetic semirigid splints had been implanted in five children with tracheomalacia and one with bronchomalacia. Mean age at the time of airway splinting was 4 years (range 6 months to 8 years). At their last clinical evaluation, all six children were leading normal active lives. Three had mild respiratory symptoms not related to the splinting. The only long-term complication was a serous effusion that developed around the splint and compressed the trachea in one child 2 years postoperatively. Tracheal fluoroscopy, barium swallow, and computed tomography scans of the trachea in five patients demonstrated satisfactory tracheal caliber without airway collapse during expiration and coughing. Pulmonary function testing showed a mild increase in airway resistance in one child who had had a tracheostomy. These results demonstrate that the application of composite synthetic graft to a segment of a malacic airway in young patients can provide long-term relief from airway collapse without compromising airway growth.

Severe tracheomalacia associated with esophageal atresia: results of surgical treatment.

This study reviews our experience from 1977 to 1991 with 32 children born with esophageal atresia and tracheoesophageal fistula (EA-TEF) who later underwent surgery for severe tracheomalacia. Indications for surgery included dying spells (21), inability to extubate the airway (nasotracheal tube 5, tracheotomy 3), and recurrent pneumonia (3). Diagnosis was confirmed by chest x-ray, esophagogram, and bronchoscopy. Aortopexy was performed in 31 of 32 children; a splint without aortopexy was used in one older girl. Splinting was also necessary in two of the 31 at the initial operation, when aortopexy failed to prevent tracheal collapse. There were four initial failures. Currently, 29 children are well (median follow-up, 6.6 years). Two have a tracheostomy in place, and one, who had a vascular ring divided after aortopexy, died at home of unknown cause 1 month later. These findings indicate that aortopexy provides long-term relief of severe symptoms of tracheomalacia associated with EA-TEF in almost all affected children. When aortopexy fails, the insertion of an airway splint may succeed; otherwise, tracheostomy is necessary.

An experimental model of a submucosally tunnelled valve for the replacement of the ileo-cecal valve.

An enteric valve to prevent colonic content reflux and to prolong small bowel transit time was created by passing small bowel through a submucosal tunnel in the colon. Barium enema, Gl tract series, and iso- and antiperistaltic pressure measurements showed the valve to be of competence equal to the ileo-cecal valve. Late pathological examination revealed a patent valve with minimal scar formation. The optimal submucosal tunnel length was between 4 and 6 cm. This valve can, theoretically, increase the absorptive capacity in short bowel syndrome and may serve as a substitute for the critically important ileo-cecal valve.

Gastric devascularization--an emergency treatment for hemorrhagic gastritis in the neonate.

A newborn baby suffering from massive hemorrhage due to erosive gastritis, was treated successfully by devascularization of the stomach which is a rather simple procedure. Experience with adults as well as with this patient justifies the use of this operation when other measures fail to stop massive bleeding in hemorrhagic gastritis.

Colon interposition for the short bowel syndrome.

A 5-mo-old male had disabling diarrhea and malabsorption following massive small bowel resection. His transit time was 10 min. After 9 mo of conservative treatment, a 24-cm isoperistaltic segment of colon was interposed 6.5 cm from the ligament of Treitz. Transit time was increased to 105 min, and he was eventually able to be maintained on an enteric diet without significant diarrhea. Colon interposition requires little manipulation of the remaining small intestine and does not rely on active intestinal obstruction to effect an increased transit time.

The surgical management of children with familial dysautonomia.

Familial dysautonomia (FD) is a rare incurable genetic disorder with multisystem involvement. Most of its clinical manifestations are related to disorders of the autonomic nervous system. The disease is associated with specific disturbances of the upper gastrointestinal tract: pharyngoesophageal dyskinesia, gastroesophageal reflux, and prolonged gastric emptying. About 40% of the dysautonomic children manifest repeat vomiting crises. In view of the extensive gastrointestinal symptomatology, children with FD are prone to repeated aspiration pneumonia and chronic respiratory failure, while inadequate calory and fluid intake may lead to a chronic state of hypovolemia and severe failure to thrive. Control of vomiting, prevention of aspiration due to abnormal swallowing, and the assurance of adequate calory intake are three major objectives in the treatment of the dysautonomic child. Medical treatment of the gastrointestinal disorders using different drugs has had limited success. This study reviews the surgical experience in ten children with FD. The type of the procedure used was determined by the severity of the upper GI disturbances. Nine children underwent gastroesophageal Nissen fundoplication and gastrostomy. In seven of them, a pyloroplasty was added. Gastrostomy alone was done in one patient only. Postoperative complications included transient dysphagia in four patients, gastric dilatation in four patients, and dumping syndrome in one. There has been no incidence of immediate postoperative death. One child died 6 months after operation from severe and irreversible respiratory failure. Following operation, the patients still suffered from dysautonomic crises but these were not associated with vomiting.(ABSTRACT TRUNCATED AT 250 WORDS)

A new intratracheal stent for tracheobronchial reconstruction: experimental and clinical studies.

An intraluminal tracheal stent (ITS) was used experimentally in rabbits and piglets, as well as clinically in infants with tracheal stenosis, to facilitate airway reconstruction. The ITSs were constructed of stainless-steel springs covered with silicone rubber. They were implanted in seven piglets (6 to 8 kg), five rabbits (3 to 5 kg) and three infants. No animals developed severe respiratory distress and all appeared to tolerate the ITS. Postmortem examinations 1 to 8 weeks after surgery showed (1) loss of stent fixation (one pig), (2) increased tracheal secretions, (3) pneumonia (one pig, two rabbits), and (4) focal squamous metaplasia of tracheal mucosa. Stents used to treat three infants (2 to 5 months of age) with complex tracheobronchial stenosis were placed at the time of periosteal tracheoplasty in two. Recurrent stenosis necessitated a second tracheoplasty and stenting in one, and a long tracheostomy tube and balloon dilatations in the other. The third child had endoscopic stent insertion to alleviate severe airway collapse after esophageal tracheoplasty. The child died from progressive respiratory failure after stent dislodgment. Although the stents were well tolerated in animals and they enhanced critical ventilation of all pulmonary lobes in infants after tracheal reconstruction, certain modifications such as alternative methods of fixation, accommodation for tracheal growth, and reduction in tissue reactivity are necessary before further use of the ITS can be advocated.

Congenital tracheal stenosis: a review of 22 patients from 1965 to 1987.

Twenty-two infants with congenital tracheal stenosis (CTS) were treated in our hospital between 1965 and 1987. Diagnosis was confirmed by endoscopic and radiographic methods. Patients had a spectrum of tracheobronchial lesions from localized stenosis to more complex deformities involving the carina and bronchi. Other anomalies were found in all patients with the occurrence of vascular slings or rings in 11 patients (50%). Six infants treated nonoperatively died from severe CTS and other lethal anomalies. Five of 16 patients (31%) treated surgically survived. Localized CTS in four cases was treated by dilatation, tracheostomy, or tracheal resection with primary anastomosis (two survivors, 2 non-survivors). Funnel-shaped deformities and extensive tracheobroncial stenosis were treated by tracheal reconstruction using a variety of autogenous tissue and prosthetic grafts (three survivors, nine non-survivors). The overall mortality was 77%. A new intratracheal stent was used in two patients. The stent was a flexible steel spring covered with a silicone rubber sheath. In one patient, it was placed within the trachea at the time of repair and removed later with the bronchoscope. A stent was used in a second patient with intermittent airway obstruction following an esophageal tracheoplasty. In this case, the device failed to alleviate the obstruction, and the infant expired from progressive respiratory failure. Issues of importance in the management of infants with CTS are: (1) adequate evaluation of the tracheobronchial tree, (2) awareness that tracheobronchography may precipitate further respiratory decompensation, (3) assessment of vascular and other anomalies requiring surgical correction, and (4) selection of an appropriate therapeutic approach.

Airway obstruction in neonates and children: surgical treatment.

OBJECTIVE: This review of 54 infants and children with airway obstruction who were treated surgically emphasizes the importance of the surgical indications with respect to various anomalies causing airway obstruction and the surgical approach to their management. PATIENTS: There were 4 etiologic groups of airway obstruction. Group A comprised 12 infants with subglottic stenosis; Group B--20 infants with tracheomalacia; 21 patients (Group C) with anatomic narrowing of the trachea; and 1 infant (Group D) with laceration of a main bronchus. METHODS: The surgical procedures performed included anterior laryngotracheal decompression in 12 infants, aortopexy in 19; 1 pulmonary arteriopexy; tracheal stenting with an autologous rib graft in 3 and with Marlex mesh in 1. Tracheal widening, using a free tibia autologous graft, was performed in 3 patients; transbronchoscopic excision in 12; anterior tracheal wedge resection in 4, and segmental tracheal resection and anastomosis in 1 patient. The lacerated bronchus was repaired with fine Dexon sutures. RESULTS: There were no operative deaths. With respect to the original indications for surgery, there were 3 failures--2 in Group A and 1 in Group C. Two patients died from causes unrelated to the procedures--one 10 days postoperatively, and the other 3 months after surgery. CONCLUSIONS: The surgical approach to tracheal obstruction in infants and children offers effective treatment, with no operative mortality, a low complication rate, and good long term survival.