Grain boundary phases in bcc metals.

We report a computational discovery of novel grain boundary structures and multiple grain boundary phases in elemental body-centered cubic (bcc) metals represented by tungsten, tantalum and molybdenum. While grain boundary structures created by the γ-surface method as a union of two perfect half crystals have been studied extensively, it is known that the method has limitations and does not always predict the correct ground states. Herein, we use a newly developed computational tool, based on evolutionary algorithms, to perform a grand-canonical search of high-angle symmetric tilt and twist boundaries, and we find new ground states and multiple phases that cannot be described using the conventional structural unit model. We use molecular dynamics (MD) simulations to demonstrate that the new structures can coexist at finite temperature in a closed system, confirming that these are examples of different grain boundary phases. The new ground state is confirmed by first-principles calculations.

New understanding of nano-scale interstitial dislocation loops in BCC iron.

Complex states of nanoscale interstitial dislocation loop can be described by its habit plane and Burgers vector. Using atomistic simulations, we provide direct evidences on the change of the habit plane of a 1/2〈1 1 1〉 loop from {1 1 1} to {1 1 0} and {2 1 1}, in agreement with TEM observations. A new {1 0 0} habit plane of this loop is also predicted by simulations. The non-conservation of the Burgers vector is approved theoretically for: (1) dislocation reactions between loops with different Burgers vectors and (2) the transition between 〈1 0 0〉 loops and 1/2〈1 1 1〉 loops. The rotation from a 1/2〈1 1 1〉 to a 〈1 0 0〉 loop has also been explored, which occurs at 570 K for time on the order of 10 s. The dislocation-precipitate phase duality and change of habit plane are then proposed as new features for nano-scale dislocation loops.

Long-time atomistic dynamics through a new self-adaptive accelerated molecular dynamics method.

A self-adaptive accelerated molecular dynamics method is developed to model infrequent atomic-scale events, especially those events that occur on a rugged free-energy surface. Key in the new development is the use of the total displacement of the system at a given temperature to construct a boost-potential, which is slowly increased to accelerate the dynamics. The temperature is slowly increased to accelerate the dynamics. By allowing the system to evolve from one steady-state configuration to another by overcoming the transition state, this self-evolving approach makes it possible to explore the coupled motion of species that migrate on vastly different time scales. The migrations of single vacancy (V) and small He-V clusters, and the growth of nano-sized He-V clusters in Fe for times in the order of seconds are studied by this new method. An interstitial-assisted mechanism is first explored for the migration of a helium-rich He-V cluster, while a new two-component Ostwald ripening mechanism is suggested for He-V cluster growth.

Structural characterization of epitaxial Cr(x)Mo(1-x) alloy thin films.

To develop a model system containing regularly spaced misfit dislocations for studies of the radiation resistance of nanoscale defects, epitaxial thin films of Cr, Mo, and Cr(x)Mo(1-x) alloys were deposited on MgO(001) by molecular beam epitaxy. Film compositions were chosen to vary the lattice mismatch with MgO. The film structure was investigated by x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and scanning transmission electron microscopy (STEM). Epitaxial films with reasonably high crystalline quality and abrupt interfaces were achieved at a relatively low deposition temperature, as confirmed by STEM. However, it was found by XRD and RBS in the channeling geometry that increasing the Mo content of the CrMo alloy films degraded the crystalline quality, despite the improved lattice match with MgO. XRD rocking curve data indicated that regions of different crystalline order may be present within the films with higher Mo content. This is tentatively ascribed to spinodal decomposition into Cr-rich and Mo-rich regions, as predicted by the Cr(x)Mo(1-x) phase diagram.

Ab initio study of stability and migration of H and He in hcp-Sc.

Ab initio calculations based on density functional theory have been performed to determine the relative stabilities and migration of H and He atoms in hcp-Sc. The results show that the formation energy of an interstitial H or He atom is smaller than that of a corresponding substitutional atom. The tetrahedral (T) interstitial position is more stable than an octahedral (O) position for both He and H interstitials. The nudged elastic band method has been used to study the migration of interstitial H and He atoms in hcp-Sc. It is found that the migration energy barriers for H interstitials in hcp-Sc are significantly different from those for He interstitials, but their migration mechanisms are similar. In addition, the formation energies of five different configurations of a H-H pair were determined, revealing that the most stable configuration consists of two H atoms located at the second-neighbor tetrahedral interstitial sites along the hexagonal direction. The formation and relative stabilities of some small He clusters have also been investigated.

Comparison of open and laparoscopic treatment of acute appendicitis.

BACKGROUND: Appendectomy can be performed using either a laparoscopic or an open technique. This study compares the outcome of patients treated for acute appendicitis by open appendectomy with the outcome of those undergoing laparoscopic appendectomy. METHODS: Patients undergoing appendectomy at The Mount Sinai Hospital between 1994 and 1998 were studied. Outcome of patients having open appendectomy was compared with that of patients having laparoscopic appendectomy. RESULTS: Seven hundred fifty-eight patients underwent appendectomy for acute appendicitis during the 5-year study period. Two hundred seventy-one (36%) had open appendectomy and 487 (64%) had laparoscopic appendectomy. Patients subsequently found to have a normal appendix had the highest rate of laparoscopic appendectomy, whereas those with gangrenous appendicitis were most likely to have open appendectomy (P <0.05). There was a significant decline in the postoperative length of stay for open cases during the length of the study. In the final year, the difference in length of stay between open and laparoscopic appendectomy was only 1 day. Patients with gangrenous appendicitis had a significantly longer length of stay than did patients with a normal appendix or suppurative appendicitis. The hospital cost of laparoscopic appendectomy was greater than that for open appendectomy but the extra expenditure in the operating room was offset by the longer length of stay of the patients having open surgery. CONCLUSIONS: Differences in outcome between open and laparoscopic appendectomy are minor. In this study, more difficult cases with gangrenous appendicitis were more likely to require open appendectomy whereas milder forms of appendicitis, especially in women, were more likely to be treated by laparoscopy. Savings from the slightly shorter hospital stay after laparoscopic appendectomy are offset by the higher surgical cost of the laparoscopic equipment.

Colorectal carcinoma associated with ulcerative colitis: a study of prognostic indicators.

Fifty-two patients with ulcerative colitis and colorectal cancer undergoing colectomy at the Mount Sinai Hospital between 1973 and 1988 were studied retrospectively to determine the correlation of age, sex, duration of colitis, tumor location, number of cancers, tumor differentiation, colloid content, presence of signet ring cells, Dukes' classification, and DNA ploidy with survival. The mean age was 45 years, with a mean duration of colitis of 21 years. Five patients (10%) had Dukes' A lesions, 17 (33%) had Dukes' B lesions, 17 (33%) had Dukes' C lesions, and 13 (25%) had distant metastases. Thirty patients (58%) had well- or moderately differentiated tumors, whereas tumors were poorly differentiated in 22 (42%). Twenty-eight patients (54%) had colloid tumors, and, in 14 (27%), signet ring cells were present. Thirty-one patients (60%) had nondiploid tumors. Actuarial analysis revealed that the 5-year survival rate was significantly worse for patients with nondiploid tumors (76% versus 32%). When stratified by stage, only patients with Dukes' C lesions showed a significant difference in survival for diploid versus nondiploid tumors. Multivariate analysis showed that the Dukes' classification was the best prognostic indicator, followed by tumor differentiation and DNA ploidy. Tumor location, colloid content, number of cancers, duration of disease, age, and sex did not correlate with the prognosis.

DNA ploidy of colorectal cancer and synchronous polyps in polyposis coli.

Sixteen patients with polyposis coli and cancer were studied retrospectively to determine the incidence of DNA ploidy abnormalities in the tumors and synchronous polyps. Six patients (37 percent) had nondiploid tumors. Nondiploid tumors were more likely to be advanced and had a significantly worse prognosis (17 percent vs. 76 percent 5-year survival; P less than 0.01). Only 4 of 20 polyps studied were nondiploid. There was no association between tumor and polyp ploidy. All nondiploid polyps were found in patients with synchronous diploid cancers. Patients with nondiploid polyps were more likely to be older and have more advanced tumors than those with diploid polyps. DNA ploidy abnormalities seem to occur with the same frequency in polyposis coli as in the nonpolyposis population, and tumor ploidy correlates with prognosis.

The caring ethic: more than kindness, the core of nursing science.

A contemporary dilemma in nursing is the order to care in a society that refuses to value caring. The authors analyze the historical creation of this dilemma and its consequences for nursing. In addition, they explore the meaning of the concept of caring from a nursing perspective, along with the impact of technology on patients, providers, and caring. Finally, a framework and strategies for the promotion of caring within the discipline of nursing are presented.

Significance of DNA content abnormalities in small rectal cancers.

Several studies have shown that the presence of DNA content abnormalities, measured by flow cytometry, may correlate with a poor prognosis in a variety of cancers. The predictive value of DNA content in patients with small rectal cancers has not been well determined. Thirty-nine patients with primary rectal adenocarcinoma smaller than 3 cm were studied in a comparison of DNA content with established prognostic variables. The following covariates were evaluated for their prognostic value: sex, age, tumor size, location, distal margin, Dukes' classification, tumor differentiation, and DNA content. DNA content was assessed by flow cytometric analysis, and each tumor was categorized as diploid or nondiploid. Of the parameters studied, Dukes' classification and tumor DNA content were found to be independent prognostic indicators. Determination of DNA content seems to provide additional useful prognostic information in patients with small rectal tumors.

Ultrasonic mucosal proctectomy in patients with ulcerative colitis.

A technique for performing mucosal proctectomy in patients with ulcerative colitis using ultrasonic fragmentation is described. Twenty-eight patients undergoing colectomy and ileoanal anastomosis were studied. Removal of the mucosal layer of the distal rectum was performed using a titanium probe vibrating at 23 kHZ with an amplitude of 300 microns. This method produces complete mucosal destruction and the resulting debris and irrigating fluid is removed through the hollow central portion of the probe. Healing of the ileoanal anastomosis does not appear to be adversely affected by the use of this technique. Because ultrasonic fragmentation is not dependent on the integrity of the submucosal plane, it may be advantageous in those cases in which severe inflammation and submucosal scarring make manual dissection of the rectal mucosa difficult to perform.

Prognostic significance of DNA content abnormalities in young patients with colorectal cancer.

Several studies have shown that the presence of DNA ploidy abnormalities, measured by flow cytometry, may correlate with a poor prognosis in a variety of cancers. The predictive value of these DNA abnormalities in young patients with colorectal cancer has not been well studied. Fifty patients aged 40 years and younger with colorectal adenocarcinoma were studied to determine the correlation of tumor DNA abnormalities with survival. DNA content was determined by flow cytometric analysis and each tumor was categorized as diploid or nondiploid. Of the parameters studied, Dukes' classification and tumor DNA ploidy were found to be significant prognostic indicators. Determination of DNA content seems to provide additional useful prognostic information in young patients with colorectal cancer.

The ideal fetal head circumference calculation.

Various formulas have been employed to compute the circumference of an ellipse. These formulas can be separated into three groups: formulas for a circle, formulas for an incorrect ellipse, and a very complicated formula for a correct ellipse. The errors caused by the first two groups are termed systematic because they occur every time that one of these formulas is used. When measuring fetal head circumference, the errors increase as the fetal head is more ellipsoid, becoming more than 1% when the ratio of the biparietal to fronto-occipital diameter decreases to less than .70. Near term, when the fetal head is large, this could create an error in predicting gestational age of almost .8 weeks. The third group is associated with mathematical random errors because of the difficulty in using a cumbersome equation. All of these formulas and their shortcomings are analyzed. A calculation for the correct circumference of an ellipse is proposed using the simple formula for a circle times a correction factor. The correction factor depends solely on the ratio of the biparietal to fronto-occipital diameter. This formula should minimize random errors and eliminate systematic errors in the calculation of fetal head circumference and will permit a more accurate analysis of fetal age.

Jumping from the Brooklyn Bridge.

In an attempt to identify factors contributing to survival of free fall and impact, we evaluated the records of four patients who survived a jump from the Brooklyn Bridge into the East River in New York Harbor between 1977 and 1985. All four patients were male and ranged in age from 22 to 67 years. They had free falls of between 41.0 and 48.8 meters. All of the patients were brought to the hospital within 24 minutes of entering the water. Three of the four had emergency surgical treatment and the fourth patient had only minor injuries. All four patients survived the suicide attempts. The length of the hospital stay ranged from two to 26 days.

Mesenteric and retroperitoneal cysts.

Mesenteric and retroperitoneal cysts are rare intra-abdominal tumors. Ten new patients are presented as well as 152 other cases reported in the English literature. These 162 cases were then analyzed for significant trends. Patients under 10 years of age were significantly different from the older group with respect to a shorter duration of symptoms, a higher number of patients requiring an emergency operation, a lower number of recurrences and the location of the cyst. Patients with retroperitoneal cysts were more likely to have incomplete excision of the cyst and therefore had a higher incidence of recurrence. They also required marsupialization more often. Retroperitoneal cysts should be considered a different entity from mesenteric cysts even though they present clinically in a similar fashion. The outcome of surgical treatment is less satisfactory in patients with retroperitoneal cysts.

Ultrasonic fragmentation. A new technique for mucosal proctectomy.

We report a new technique for mucosal proctectomy that does not require manual separation of the mucosa and submucosa from the underlying muscularis. Mucosal proctectomy using ultrasonic fragmentation of the rectal mucosa was performed in four patients. Three had severe ulcerative colitis, and one patient had radiation proctitis with a rectal stricture. In all cases an endorectal pullthrough with anastomosis to the area of the dentate line was performed. Healing after ultrasonic mucosal proctectomy occurred without infection or retraction. Ultrasonic fragmentation offers an alternative to the standard technique of mucosal proctectomy. This new method is useful in those patients in whom separation of the rectal mucosal layer is difficult to perform.

Ultrasonic mucosal proctectomy without endorectal pull-through.

The surgical treatment of patients with familial polyposis coli and ulcerative colitis often requires removal of the rectum. Abdominoperineal resection, however, has a substantial morbidity. Ultrasonic fragmentation allows complete removal of the distal rectal mucosa with preservation of the surrounding muscularis. Ten adult mongrel dogs underwent ultrasonic mucosal proctectomy with resection of the proximal rectum and end colostomy. Two months later, the animals were sacrificed and the remaining rectum was removed and examined. The rectal remnant had shrunk and there was fibrous healing of the muscular wall with obliteration of the lumen. There was no mucosal regeneration. Ultrasonic mucosal proctectomy appears to achieve the same results as abdominoperineal resection of the rectum without the morbidity of the perineal dissection. This procedure may be useful in those patients where removal of the rectum is necessary for benign disease and endorectal pull-through is not indicated.

Patterns of treatment of gallstone ileus over a 45-year period.

All patients with gallstone ileus admitted to our institutions between 1938 and 1982 were retrospectively analyzed by grouping the patients into 10-year periods. Forty-five patients were studied, of whom 39 required operation. When hospital statistics for admissions, length of stay, and mortality rates from the Mount Sinai Hospital were compared to the gallstone ileus data, it was found that there has been no significant change in the admission rate for these patients. The mortality rate and length of stay of gallstone ileus patients has also remained constant over the past 25 years despite the general hospital decrease in both of these numbers. There has been no change in the complication rate, duration of symptoms prior to admission, or the preoperative diagnostic rate of gallstone ileus during the duration of this study.

The inaccuracy of total uterine volume measurements: sources of error and a proposed solution.

Inaccuracies in total intrauterine volumes calculated using the prolate ellipse equation have been reported. No previous study has examined all the sources of error. In this study, a comprehensive approach was undertaken. Measurements were obtained from scans of the pregnant uterus in the prone position using an automated water-path scanner (Octoson) and in the supine position using standard static B-mode scanners. Several conclusions could be drawn: 1) From the Octoson prone scans, uterine volumes obtained using the prolate ellipse formula were markedly different from the true uterine volumes obtained by the summation of stepped areas. This showed that the prolate ellipse formula was inaccurate. 2) From the static supine scans, many observer inconsistencies were found in uterine volumes obtained from the prolate ellipse formula. This made the prolate ellipse formula unreliable. 3) Previously published graphs calculated from the prolate ellipse equation, comparing fetal age with total intrauterine volume, were found to vary accuracy, presumably as a result of 1 and 2. A more accurate approach is proposed. Using the outer uterine wall as the boundary, the stepped area-to-volume values of transverse scans taken at 3-cm intervals were found to closely approximate true volumes, with an average error of only 3.5 per cent. Since these measurements encompass the intrauterine contents and the myometrium, it is suggested that the term "total uterine volume" be used instead of "total intrauterine volume."