Enabling near-atomic-scale analysis of frozen water.

Transmission electron microscopy went through a revolution enabling routine cryo-imaging of biological and (bio)chemical systems, in liquid form. Yet, these approaches typically lack advanced analytical capabilities. Here, we used atom probe tomography to analyze frozen liquids in three dimensions with subnanometer resolution. We introduce a specimen preparation strategy using nanoporous gold. We report data on 2- to 3-µm-thick layers of ice formed from both high-purity deuterated water and a solution of 50 mM NaCl in high-purity deuterated water. The analysis of the gold-ice interface reveals a substantial increase in the solute concentrations across the interface. We explore a range of experimental parameters to show that atom probe analyses of bulk aqueous specimens come with their own challenges and discuss physical processes that produce the observed phenomena. Our study demonstrates the viability of using frozen water as a carrier for near-atomic-scale analysis of objects in solution by atom probe tomography.

Nanoscale mechanism of the stabilization of nanoporous gold by alloyed platinum.

Nanoporous gold (NPG) is usually made by electrochemical dealloying of Ag from binary AgAu alloys. The resulting nanoscale ligaments are not very stable, and tend to coarsen with time by surface self-diffusion, especially in electrolyte, which may lead to inferior electrocatalytic properties. Addition of a small amount of Pt to the precursor alloy is known to refine and stabilize the nanoporous product (NPG-Pt). However, the mechanisms by which Pt serves to refine the microstructure remain poorly understood. The present study aims to expand our knowledge of the role of Pt by examining NPG-Pt at atomic resolution with Atom Probe Tomography (APT), as well as by aberration-corrected Transmission Electron Microscopy. Atomic level observation of Pt enrichment on ligament surfaces sheds light on the underlying mechanisms that give rise to Pt's refining effect. Owing to improved Ag retention with higher Pt content, NPG-Pt1 (made by dealloying Ag77Au22Pt1) was shown to have the highest surface area-to-volume ratio, compared to NPG-Pt3 (made by dealloying Ag77Au20Pt3). Quantitative estimates reveal up to 5-fold enrichment of Pt at nanoligament surfaces, compared to the precursor content, in NPG-Pt. The interface between the dealloyed layer and the substrate was captured by APT, for the first time. The findings of this investigation add insight into the functionality of NPG-Pt and its prospective catalytic performance.

Analytical electron microscopy of a crack tip extracted from a stressed Alloy 800 sample exposed to an acid sulfate environment.

Alloy 800 (Fe-21Cr-33Ni) has been found susceptible to cracking in acid sulfate environments, but the mechanism is not well understood. Alloy 800 C-ring samples were exposed to an acid sulfate environment at 315°C and cracks were found with depths in excess of 300µm after 60h. Preparation of a TEM sample containing crack tips is challenging, but the ability to perform high-resolution microscopy at the crack tip would lend insight to the mechanism of acid sulfate stress corrosion cracking (AcSCC). The lift-out technique combined with a focused ion beam sample preparation was used to extract a crack tip along the cross-section of an acid sulfate crack in an Alloy 800 C-ring. TEM elemental analysis was done using EDS and EELS which identified a duplex oxide within the crack; an inner oxide consisting of a thin 3-4nm Cr-rich oxide and an outer oxide enriched in Fe and Cr. Preliminary conclusions and hypotheses resulted with respect to the mechanism of AcSCC in Alloy 800.

Vibrational lifetimes and isotope effects of interstitial oxygen in silicon and germanium.

Decay dynamics of local vibrational modes provides unique information about energy relaxation processes to solid-state phonon bath. In this Letter the lifetimes of the asymmetric stretch mode of interstitial 16O and 17O isotopes in Si are measured at 10 K directly by time-resolved, transient bleaching spectroscopy to be 11.5 and 4.5 ps, respectively. A calculation of the three-phonon density of states shows that the 17O mode lies in the highest phonon density resulting in the shortest lifetime. The lifetime of the 16O mode in Ge is measured to be 125 ps, i.e., approximately 10 times longer than in Si. The interaction between the local modes and the lattice vibrations is discussed according to the activity of phonon combinations.

Lower pole I: a prospective randomized trial of extracorporeal shock wave lithotripsy and percutaneous nephrostolithotomy for lower pole nephrolithiasis-initial results.

PURPOSE: The efficacy of shock wave lithotripsy and percutaneous stone removal for the treatment of symptomatic lower pole renal calculi was determined. MATERIALS AND METHODS: A prospective randomized, multicenter clinical trial was performed comparing shock wave lithotripsy and percutaneous stone removal for symptomatic lower pole only renal calculi 30 mm. or less. RESULTS: Of 128 patients enrolled in the study 60 with a mean stone size of 14.43 mm. were randomized to percutaneous stone removal (58 treated, 2 awaiting treatment) and 68 with a mean stone size of 14.03 mm. were randomized to shock wave lithotripsy (64 treated, 4 awaiting treatment). Followup at 3 months was available for 88% of treated patients. The 3-month postoperative stone-free rates overall were 95% for percutaneous removal versus 37% lithotripsy (p <0.001). Shock wave lithotripsy results varied inversely with stone burden while percutaneous stone-free rates were independent of stone burden. Stone clearance from the lower pole following shock wave lithotripsy was particularly problematic for calculi greater than 10 mm. in diameter with only 7 of 33 (21%) patients becoming stone-free. Re-treatment was necessary in 10 (16%) lithotripsy and 5 (9%) percutaneous cases. There were 9 treatment failures in the lithotripsy group and none in the percutaneous group. Ancillary treatment was necessary in 13% of lithotripsy and 2% percutaneous cases. Morbidity was low overall and did not differ significantly between the groups (percutaneous stone removal 22%, shock wave lithotripsy 11%, p =0.087). In the shock wave lithotripsy group there was no difference in lower pole anatomical measurements between kidneys in which complete stone clearance did or did not occur. CONCLUSIONS: Stone clearance from the lower pole following shock wave lithotripsy is poor, especially for stones greater than 10 mm. in diameter. Calculi greater than 10 mm. in diameter are better managed initially with percutaneous removal due to its high degree of efficacy and acceptably low morbidity.

Three-dimensional measurement of essential tremor.

A mechanical linkage device was used to measure the three-dimensional position of the fingertip during a postural task. Thirty patients with essential tremor were tested simultaneously with the device, uniaxial accelerometry, and clinical tremor measures. Eighteen patients were tested again 16+/-4 days later. The device accurately recorded the three-dimensional behavior of essential tremor. Measures from the device included mean three-dimensional velocity, mean three-dimensional dispersion, and power of the three-dimensional acceleration. The logarithms of these measures were strongly correlated (r = .841-.984) with all clinical measures including self-reported tremor disability. The device measures were reliable within and between testing sessions (intraclass correlation coefficients = .971-.977). The performance of the device was superior to uniaxial accelerometry, most likely as a result of the three-dimensional nature of the measurements. We conclude that essential tremor can be validly and reliably quantified during a postural task providing the recording device records movement in three dimensions and the measurements are logarithmically transformed.

Laparoscopic complications in markedly obese urologic patients (a multi-institutional review)

OBJECTIVES: Significant obesity is considered to be a relative contraindication to laparoscopic surgery. This study reviews the complications encountered in massively obese patients undergoing urologic laparoscopic surgery. METHODS: Body mass index (BMI) was used as an objective index to indicate massive obesity. Eleven institutions compiled retrospective data on 125 patients having a BMI greater than 30. Procedures performed included 76 pelvic lymph node dissections, 14 nephrectomies, 7 bladder neck suspensions, and 28 miscellaneous procedures. RESULTS: For the group as a whole, the mean BMI was 35.1 (range 30.1 to 57.2). Mean operative time was 202 minutes (range 60 to 480). Conversion to open surgery occurred in 15 of the 125 patients (12%). Complication rates (minor and major) were 22% (27 occurrences in 125 patients) intraoperatively and 26% (33 occurrences in 125 patients) postoperatively. The major complications included 2 trocar injuries to abdominal wall vessels, 1 bladder injury, 3 peripheral nerve injuries, 1 dysrhythmia, 1 deep vein thrombosis, 1 wound seroma, 1 nephrocutaneous fistula, 1 incisional hernia, and 1 death. CONCLUSIONS: In this review, complication rates for urologic laparoscopic surgery on massively obese patients were higher than in the general population undergoing laparoscopic surgery (0.3% to 21%).

Treatment of pediatric urolithiasis between 1984 and 1994.

PURPOSE: We report our experience with the management of pediatric urolithiasis during a 10-year period. Our aim was to assess the impact of new technology in the treatment of pediatric urolithiasis. MATERIALS AND METHODS: We retrospectively reviewed the records of all patients up to age 18 years in whom urolithiasis was treated from 1984 to 1994. In 37 cases 24-hour urine collections were available for metabolic evaluation. RESULTS: A total of 100 pediatric patients was treated for urolithiasis. Mean followup was 36 months. A total of 79 patients underwent 115 procedures for symptomatic urolithiasis and 21 were treated nonoperatively. In 42 patients structural anomalies of the urinary tract required additional management. Metabolic abnormalities in 48 patients included hypercalciuria in 19, defined as greater than 4 mg./kg./24 hours calcium by 24-hour urine collection. Only 24 of the 100 patients had no identifiable predisposing factors. Procedures included shock wave lithotripsy in 42 cases, basket extraction with or without ureteroscopy in 20, percutaneous nephrostolithotomy in 11 and litholapaxy in 12. Open surgery included cystolithotomy in 10 cases and other forms of open lithotomy in 15. Thus, open surgical removal was necessary in 1 of 5 cases. CONCLUSIONS: Compared to the traditional mode of stone treatment, fewer patients required open surgery. Our results indicate that a comprehensive approach to the care of pediatric patients with urolithiasis requires attention to metabolic and structural abnormalities.

Closure of laparoscopic trocar sites using a spring-loaded needle.

Closure of laparoscopic trocar sites can be difficult, particularly in the obese patient. We have begun using a spring-loaded needle to facilitate closure of these sites. We have found that the device allows for accurate suture placement, the potential of decreased closure time, reduced risk for trocar site dehiscence, and can be used in obtaining hemostasis of abdominal wall vessels.

Laparoscopically assisted percutaneous renal biopsy.

We performed laparoscopically assisted percutaneous renal biopsy on 4 patients with azotemia or renal dysfunction who were believed to be unsuitable candidates for percutaneous renal biopsy. Tissue adequate for diagnosis was obtained in all 4 cases. Complications included subcutaneous emphysema in 1 patient and a small splenic capsular tear in 1, which was managed laparoscopically and did not require transfusion. Bleeding from the renal biopsy occurred in 1 patient and was easily managed laparoscopically. We recommend laparoscopically assisted percutaneous renal biopsy as an alternative method of renal biopsy in patients who can tolerate general anesthesia and who are not candidates for percutaneous renal biopsy.

Extracorporeal shock-wave lithotripsy in horseshoe kidneys.

Using the Dornier HM-3 lithotriptor, 10 patients (11 renal units) with calculi in horseshoe kidneys were treated with extracorporeal shock-wave lithotripsy (ESWL) and ancillary procedures. Six renal units (55%) underwent pre-ESWL manipulation consisting of a Double J stent, ureteral catheter, or percutaneous nephrostomy. The "blast path" was employed to treat five renal units which could not be positioned at F2. Good initial stone fragmentation was obtained in eight renal units (73%). There were two episodes of post-ESWL obstruction requiring intervention; both occurred in the same patient. A total of seven post-ESWL procedures were performed on two renal units. After all procedures, eight renal units (73%) were rendered stone-free, six (55%) with ESWL alone. The average follow-up interval was twelve months (range 1-28 months). ESWL can be used effectively to treat some patients with calculi in horseshoe kidneys. The ectopic location of these renal units may make it difficult to position calculi at F2, thus necessitating treatment on the blast path or placement of the patient in prone position. Multiple ancillary procedures may be necessary.

Renal transplantation: a 20-year experience at the University of Florida.

Substantial gains have been made in both patient and graft survival during 20 years of transplanting kidneys at the University of Florida. The number of transplant recipients yearly has increased from six in 1966 to more than 100 in 1986. The use of immunosuppression reflects our evolving understanding of transplant immunology, with current morbidity and mortality rates considerably improved over those of the early years. This paper summarizes our transplantation experience over the past two decades.

Ureteral access system. Technique and results.

Suggestions for the safe use of the ureteral access set are outlined in Table 1. Although this tool is valuable in selected circumstances, great care must be exercised in its use. In the series described, the incidence of perforation was 31 per cent. Although no long-term sequelae are known to have occurred, the potential for such problems is present. If ureteral injury is suspected, a retrograde pyelogram should be performed. Proper diversionary measures must be performed when a perforation is confirmed. Appropriate long-term radiographic evaluation should follow.

The blast path: theoretical basis, experimental data and clinical application.

Use of the "blast path" may be helpful in patients where positioning for ESWL treatments is difficult. Good pressures are maintained along the blast path and an alternate fracture mechanism may be in effect. The rate of fragmentation, assessed using model material, decreases with distance beyond F2.

Simulation of ventilatory-induced stone movement and its effect on stone fracture during extracorporeal shock wave lithotripsy.

Because ventilation influences renal movement, we investigated the effect of stone motion on the efficiency of extracorporeal shock-wave lithotripsy (ESWL). Comparisons of the rates of fragmentation of an experimental model of renal calculi were made between simulated high-frequency jet ventilation at 100 breaths/min. with four-mm. stone movement as measured from the fluoroscope screen, conventional mechanical ventilation at 10 breaths/min. with 32-mm. stone movement as measured from the fluoroscope screen, and a static control. Fragmentation did not differ significantly between high-frequency jet ventilation and no ventilation (static control), but was significantly greater with high-frequency jet ventilation than with conventional ventilation.

Extracorporeal shock-wave lithotripsy (ESWL). I. In vitro results of blast path treatment of human gallstones.

To evaluate the efficacy of extracorporeal shock-wave lithotripsy (ESWL) for human gallstone fragmentation, biliary calculi of different size and composition were evaluated to determine clinical applicability of this technique. Human biliary calculi composed primarily of cholesterol (Group I, N = 6) and calcium bilirubinate (Group II, N = 6) were shocked in vitro at varying positions along the ESWL blast path. All calculi subjected to lithotripsy were fragmented. Cumulative fragment size was less than or equal to 2, 3, 5, and 8 mm in 73, 86, 94, and 100% of all stones treated, respectively. No statistically significant differences were observed following stone fragmentation when the two groups were compared. Further, no statistically significant differences were evident when comparing the energy expended during fracture of stones in the two groups, or in comparison of fracture with old or new electrodes. However, when fragmentation for stone remnants less than or equal to 2 mm in size was compared at 6- and 10-cm positions on the blast path, a statistically significant difference was noted (P less than 0.001). Stone fragmentation was greatest at positions closest to F2. These data indicate that biliary calculi can be fragmented when subjected to lithotripsy and positioned on the ESWL blast path.

Extracorporeal shock-wave lithotripsy (ESWL). II. In vivo canine results of blast path treatment of human gallstones.

To evaluate the role of ESWL in vivo for the treatment of human gallstones positioned on the blast path, a canine model was developed to determine the efficacy of stone fragmentation and the subsequent histopathological injury that occurs as a result of this therapeutic technique. Twenty-four 16- to 20-kg mongrel dogs were divided into five groups: I: ESWL without stone, autopsy at 48 hr (N = 6); II: ESWL with stone (mean diameter 16.8 mm, range = 14-19 mm), autopsy at 48 hr (N = 10); III: ESWL without stone, autopsy at 41-46 days (N = 6); IV: ESWL without stone, autopsy immediately after ESWL (N = 1); V: No ESWL or stone, autopsy 2 hr after anesthesia induction (N = 1). A human gallstone (96% cholesterol) was inserted by cholecystotomy (N = 10) in Group II only. All groups (N = 24) had operative placement of a 6.5 Fr accordion catheter into the gallbladder for radiographic visualization. For each blast path treatment, 2000 discharges were delivered at 18-24 kV. Histopathologically, the Group V gallbladder served as a control. Groups I, II, and IV revealed mild subacute injury; dog gallbladders in Group III showed regression of these changes. Total surface area (TSA) of Group II stones increased from a pre-ESWL mean of 6.60 +/- 0.0.84 cm2 to 53.84 +/- 26.8 cm2 post-ESWL (P less than 0.001). Cumulative post-ESWL fragment sizes for particles in less than or equal to 2-, less than or equal to 3-, less than or equal to 5-, less than 10- and greater than or equal to 10-mm categories represented 32.9, 41.6, 49.4, 74.3, and 100% of pretreatment stone weight, respectively. These data indicate that human gallstones can be fractured to a variable degree when treated on the ESWL blast path and that TSA increased significantly. Gallbladder histopathologic changes appear to be reversible by 41-46 days post-ESWL.