Strained epitaxial interfaces of metal (Pd, Pt, Au) overlayers on nonpolar CdS ([Formula: see text]) surfaces from first-principles.

The depositions of (1 1 1) and (1 0 0) overlayers of Pd, Pt and Au on the CdS (1 0 [Formula: see text] 0) surface are studied within epitaxial mismatches of 6%-7%, using spin-polarized density functional theory. For both compressively strained and tensile-strained interfaces, the (1 0 0) overlayers were found to be thermodynamically more stable owing to better interfacial matching, and higher surface uncoordination resulting in higher reactivity. Pt(1 1 1) exhibits slip dislocations even for five-atomic-layer thick Pt slabs. Along with the leading metal-S interaction, the interfacial charge transfers indicate a weak metal-Cd interaction which decreases in strength in the order Pd > Pt ∼ Au. For the same substrate area, the accumulation of electronic charge for Pt overlayers is ∼1.5-2 times larger than that of Pd and Au. The n-type Schottky barriers of Au overlayers with the minimum mismatch are within 0.1 eV of the predictions of Schottky-Mott rule, indicating a relatively ideal, scantily reactive interface structure. This is in clear contrast to the Pt epitaxial overlayers which deviate by 0.6-0.8 eV.

Intermetallic Differences at CdS-Metal (Ni, Pd, Pt, and Au) Interfaces: From Single-Atom to Subnanometer Metal Clusters.

Metal co-catalysts tipped at a photocatalyst surface form a crucial component in the nanoheterostructures designed for the photocatalytic hydrogen evolution reaction. To examine the intermetallic differences and size effects at these interfaces, we use spin-polarized density functional theory to study single-atom, 13-atom, and 55-atom cluster depositions of Ni, Pd, Pt, and Au on the CdS(101̅0) surface. For the single metal atoms, the ground-state configuration was the same site for all of the elements. Analysis of the metal-CdS bonding and of the charge transfers revealed a Ni-Cd bonding complex leading to depletion of electronic charge at the Ni single atom and at deposited Ni clusters, in contrast to charge accumulation observed for the other three metals Pd, Pt, and Au. For scaling up sizes of the metal deposition, six subnanometer cluster types were selected over a wide range of cluster's effective coordination number, and their interfaces were differentiated by charge redistributions, structure and adhesion energies, highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) gaps, and Schottky barrier heights. Although all considered clusters are semiconducting in the gas phase, 9 out of 28 clusters became (semi)metallic after deposition on the CdS semiconductor surface. Intermetallic differences and common trends are discussed.

Structure and stability of hcp iron carbide precipitates: A first-principles study.

Hexagonal close-packed (hcp) iron carbides play an important role in steel processing and in steel products. The recent discovery of novel ultrafine (2-5 nm) iron carbide (ε'-Fe2+xC) precipitates in TRIP steel sheds a new light on the hcp family of carbides. Here we present a first-principles study on the relative stability, and the electronic, magnetic properties of the ε'-Fe2C phases. Different stackings of Fe-sheets and orderings of C atoms were investigated and compared with experimental data and with Jack's model. We find very favorable formation enthalpies for these new members of the hcp family, and we present a first-principles-refined model for the crystal structure of the ultrafine Fe(C) precipitates. These findings are useful for the characterization of nano-sized iron carbide precipitates, for understanding their role in the microstructure of steels, and for the design of novel steels having even more desirable properties.

Adsorption Study of a Water Molecule on Vacancy-Defected Nonpolar CdS Surfaces.

A detailed understanding of the water-semiconductor interface is of major importance for elucidating the molecular interactions at the photocatalyst's surface. Here, we studied the effect of vacancy defects on the adsorption of a water molecule on the (101̅0) and (112̅0) CdS surfaces, using spin-polarized density functional theory. We observed that the local spin polarization did not persist for most of the cationic vacancies on the surfaces, unlike in bulk, owing to surface reconstructions caused by displaced S atoms. This result suggests that cationic vacancies on these surfaces may not be the leading cause of the experimentally observed magnetism in CdS nanostructures. The surface vacancies are predominantly nonmagnetic except for one case, where a magnetic cationic vacancy is relatively stable due to constraints posed by the (101̅0) surface geometry. At this particular magnetic defect site, we found a very strong interaction with the H2O molecule leading to a case of chemisorption, where the local spin polarization vanishes concurrently. At the same defect site, adsorption of an O2 molecule was also simulated, and the results were found to be consistent with experimental electron paramagnetic resonance findings for powdered CdS. The anion vacancies on these surfaces were always found to be nonmagnetic and did not affect the water adsorption at these surfaces.

Stability and geometry of silica nano-ribbons (SNRs): a first-principles study.

Silica based materials are attractive because of their versatility and their unique structures and properties, which have led to numerous applications of silica in a range of fields. Recently, various low-dimensional silica materials have been synthesized experimentally. Here we present a first-principles study on the geometry and stability of novel low-dimensional silica nano-ribbons (SNRs) using density-functional theory (DFT) with van der Waals interactions (optB88-vdW). SNRs of various widths with different surface groups, and with the geometry of hexagonal rings and squares, were taken into consideration. An atomically flat ribbon with mixing squares and rings is also included. The calculations showed high stability for the single layer and bilayer silica ribbons, both containing hexagonal rings. The calculations also revealed a high flexibility of silica chains. The local structure and chemical bonding were carefully analyzed. Electronic band structure calculations showed an insulating nature of the SNRs with energy gaps of about 5.0 to 6.0 eV, which are determined by nonbonding and anti-bonding O 2p states.

Considerable variations in growth hormone policy and prescription in paediatric end-stage renal disease across European countries-a report from the ESPN/ERA-EDTA registry.

BACKGROUND: Growth retardation in paediatric end-stage renal disease (ESRD) has a serious impact on adult life. It is potentially treatable with recombinant growth hormone (rGH). In this study, we aimed to quantify the variation in rGH policies and actual provided care in these patients across Europe. METHODS: Renal registry representatives of 38 European countries received a structured questionnaire on rGH policy. Cross-sectional data on height and actual use of rGH on children with ESRD aged <18 years were retrieved from the ESPN/ERA-EDTA Registry. RESULTS: In 21 (75%) of 28 responding countries, rGH is reimbursed for children with ESRD. The specific conditions for reimbursement (minimum age, maximum age and chronic kidney disease stage) vary considerably. Mean height standard deviation scores (SDS) at renal replacement therapy (RRT) [95% confidence interval (CI)] were significantly higher in countries where rGH was reimbursed -1.80 (-2.06; -1.53) compared with countries in which it was not reimbursed [-2.34 (-2.49;-2.18), P < 0.001]. Comparison of the mean height SDS at onset of RRT and final height SDS yielded similar results. Among the 13 countries for which both data on actual rGH use between 2007 and 2011 and data from the questionnaire were available, 30.1% of dialysis and 42.3% of transplanted patients had a short stature, while only 24.1 and 7.6% of those short children used rGH, respectively. CONCLUSION: Reimbursement of rGH associates with a less compromised final stature of ESRD children. In many countries with full rGH reimbursement, the actual rGH prescription in growth-retarded ESRD children is low and obviously more determined by the doctor's and patients' attitude towards rGH therapy than by financial hurdles.

Origin of predominance of cementite among iron carbides in steel at elevated temperature.

A long-standing challenge in physics is to understand why cementite is the predominant carbide in steel. Here we show that the prevalent formation of cementite can be explained only by considering its stability at elevated temperature. A systematic highly accurate quantum mechanical study was conducted on the stability of binary iron carbides. The calculations show that all the iron carbides are unstable relative to the elemental solids, α-Fe and graphite. Apart from a cubic Fe23C6 phase, the energetically most favorable carbides exhibit hexagonal close-packed Fe sublattices. Finite-temperature analysis showed that contributions from lattice vibration and anomalous Curie-Weis magnetic ordering, rather than from the conventional lattice mismatch with the matrix, are the origin of the predominance of cementite during steel fabrication processes.

Transformations of gold nanoparticles investigated using variable temperature high-resolution transmission electron microscopy.

Recently designed advanced in-situ specimen holders for transmission electron microscopy (TEM) have been used in studies of gold nanoparticles. We report results of variable temperature TEM experiments in which structural transformations have been correlated with specimen temperature, allowing general trends to be identified. Transformation to a decahedral morphology for particles in the size range 5-12nm was observed for the majority of particles regardless of their initial structure. Following in-situ annealing, decahedra were found to be stable at room temperature, confirming this as the equilibrium morphology, in agreement with recently calculated phase diagrams. Other transitions at low temperature in addition to surface roughening have also been observed and correlated with the same nanoscale phase diagram. Investigations of gold particles at high temperature have revealed evidence for co-existing solid and liquid phases. Overall, these results are important in a more precise understanding of the structure and action of catalytic gold nanoparticles and in the experimental verification of theoretical calculations.

Decreasing perinatal mortality in The Netherlands, 2000-2006: a record linkage study.

BACKGROUND: The European PERISTAT-1 study showed that, in 1999, perinatal mortality, especially fetal mortality, was substantially higher in The Netherlands than in other European countries. The aim of this study was to analyse the recent trend in Dutch perinatal mortality and the influence of risk factors. METHODS: A nationwide retrospective cohort study of 1,246,440 singleton births in 2000-2006 in The Netherlands. The source data were available from three linked registries: the midwifery registry, the obstetrics registry and the neonatology/paediatrics registry. The outcome measure was perinatal mortality (fetal and early neonatal mortality). The trend was studied with and without risk adjustment. Five clinical distinct groups with different perinatal mortality risks were used to gain further insight. RESULTS: Perinatal mortality among singletons declined from 10.5 to 9.1 per 1000 total births in the period 2000-2006. This trend remained significant after full adjustment (odds ratio 0.97; 95% CI 0.96 to 0.98) and was present in both fetal and neonatal mortality. The decline was most prominent among births complicated by congenital anomalies, among premature births (32.0-36.6 weeks) and among term births. Home births showed the lowest mortality risk. CONCLUSIONS: Dutch perinatal mortality declined steadily over this period, which could not be explained by changes in known risk factors including high maternal age and non-western ethnicity. The decline was present in all risk groups except in very premature births. The mortality level is still high compared with European standards.

Atomic pillar-based nanoprecipitates strengthen AlMgSi alloys.

Atomic-resolution electron microscopy reveals that pillarlike silicon double columns exist in the hardening nanoprecipitates of AlMgSi alloys, which vary in structure and composition. Upon annealing, the Si2 pillars provide the skeleton for the nanoparticles to evolve in composition, structure, and morphology. We show that they begin as tiny nuclei with a composition close to Mg2Si2Al7 and a minimal mismatch with the aluminum matrix. They subsequently undergo a one-dimensional growth in association with compositional change, becoming elongated particles. During the evolution toward the final Mg5Si6 particles, the compositional change is accompanied by a characteristic structural change. Our study explains the nanoscopic reasons that the alloys make excellent automotive materials.

Acute pancreatitis in the Zabok General Hospital.

Acute pancreatitis is an acute disease of the pancreas due to the organ autodigestion. The disease is still burdened with numerous complications and quite frequently with lethal outcome, in spite of the sophisticated diagnostic and therapeutic methods currently available. The disease has a benign course in a majority of patients (80%), however, in the remaining 20% it assumes a malignant course with the development of massive necroses of the pancreatic and peripancreatic tissues, infection, hemorrhage, and endogenous intoxication with lesions of the lungs, kidneys, heart and liver. The biliary tract disease plays the major role in the etiology of acute pancreatitis (80%), followed by alcoholism (10% to 15%). This differs from the experience acquired at the Zabok General Hospital, where an almost identical incidence of biliary and ethylic etiology was recorded. Other, less common causes include post-traumatic, postoperative, infective and hormonal (hyperparathyroidism) etiology. In some cases, the cause of acute pancreatitis remains unknown. The disease shows a female predominance, which results from the higher prevalence of cholelithiasis in women than in men. Anatomically, there are two main forms of acute pancreatitis, interstitial or edematous form, and hemorrhagic necrotizing form. The interstitial or edematous form of acute pancreatitis is characterized by edema (exudation) of the pancreatic interstitium. The hemorrhagic necrotizing form of acute pancreatitis is characterized by autodigestion of a minor or major portion of the pancreas and peripancreatic tissues. The diagnosis of acute pancreatitis may initially pose a considerable problem. Decision on the mode of treatment should primarily be based on the clinical picture and supported by relevant laboratory parameters and other diagnostic procedures (ultrasonography, computed tomography). Conservative therapy is indicated for the edematous form of acute pancreatitis, whereas operative treatment is as a rule used for the necrotizing form of acute pancreatitis. Secondary bacterial contamination of the necrotic foci with the development of septic complications occurs in more than 50% of patients with the necrotizing form of acute pancreatitis, and is an absolute indication for surgical intervention. The modes of treatment used in 57 patients admitted for acute pancreatitis during the 1996-1999 period are described. Cholelithiasis was the cause of acute pancreatitis in 28 (49.1%), and alcoholism in 29 (50.9%) patients. Conservative treatment was used in 41 (72%) patients. Sixteen (28%) patients underwent operative treatment. Explorative laparotomy and drainage were performed in four patients, and explorative laparotomy, necrectomy, sequestrectomy and drainage with two or more drains in 11 patients. Cholecystectomy and T drainage along with necrectomy and drainage were performed in one patient. There were 12 (21%) patients with the most severe form of acute pancreatitis. Nine of these patients were operated on (necrectomy drainage) between day 6 and 10 of the disease. Two of these patients had to be reoperated on within a month, due to necrosis and abscess recurrence. Three of the 12 patients with the severe form of acute pancreatitis received conservative therapy. Fifteen patients were operated on 8-10 weeks after acute pancreatitis had subsided. Pseudocysts developed in three patients. These patients were operated on 6-8 weeks from the onset of disease, with internal drainage via isolated small intestine flexure performed in all of these patients. The mean duration of intensive care unit stay for all patients with acute pancreatitis was 20.6 days. Four of 57 patients hospitalized for acute pancreatitis died. The mortality rate in the group of patients with the severe form of acute pancreatitis (n = 12) was 33%. Complications developed in 50% of operatively treated patients.

[Contribution to the nomenclature of variations of the cystic artery]. / Ein Beitrag zur Nomenklatur der Variationen der Arteria cystica.

INTRODUCTION: Safe procedures for laparoscopic cholecystectomy demand good knowledge of the anatomy of the terminal part of the cystic artery and its variations, and also precise dissection in and around the hepatobiliary triangle. METHOD: Good laparoscopic visualisation enables recognition of the variation of the cystic artery. Our observations are based on 1000 cholecystectomies. RESULTS: We have described and named variations of the terminal part of the cystic artery. Group I comprises the five variations of the cystic artery within the hepatobiliary triangle: (a) "normal" position; (b) frontal cystic artery; (c) backside; (d) multiple; (e) short cystic artery that arises from an aberrant right hepatic artery. Group II consists of variations of the cystic artery that approach--the gallbladder beyond the hepatobiliary triangle: (a) "low-lying"; (b) transhepatic; (c) "recurrent" cystic artery. CONCLUSION: Our classification is simple and easy to memorize and will considerably facilitate safe laparoscopic cholecystectomy.

Symptomatic physiologic hydronephrosis in pregnancy: incidence, complications and treatment.

OBJECTIVE: We present the incidence and results of treatment of symptomatic physiologic hydronephrosis in 3,400 pregnant women. METHODS: We analyzed 103 consecutive women who presented with clinical signs and symptoms related to the upper urinary system. Renal sonography, urinalysis, serum creatinine levels, white blood cell (WBC) count, and urine culture were done in all patients at first visit and repeated at least once a month until 1 month after delivery. In patients who manifested acute pyelonephritis, urinalysis, WBC count, erythrocyte sedimentation rate and C-reactive protein levels were repeated every 3 days until normalization, and urine culture as well as renal sonography were performed once a week until 1 month after delivery. Conservative measures (positioning, analgesia, antibiotics) were performed in all patients with symptomatic physiologic hydronephrosis. If the patient's condition was refractory to medical management, drainage of the ureter with a double pigtail stent was performed. RESULTS: Conservative measures were successful in 97 (94%) of 103 patients but 6 (6%) patients had ongoing signs and symptoms of acute pyelonephritis progressing to urosepsis. In all of them, antibiotics were continued and a double pigtail stent was placed resulting in fast regression of symptoms, curing of renal infection and progress of the pregnancies to the term with vaginal delivery. CONCLUSIONS: Symptomatic hydronephrosis in pregnancy can be treated conservatively. If the patient's condition is refractory to medical management, an internal drainage with double pigtail stent may be necessary.

Gastrointestinal pseudo-obstruction: report of a patient with postoperative pseudo-obstruction.

Postoperative pseudo-obstruction is a rare state of protracted gastrointestinal paresis that may progress to paralysis without the presence of obstructive lesions. Pseudo-obstruction is usually, but not exclusively, associated with an abdominal operative procedure (laparotomy), however, it may occasionally occur following extra-abdominal operations. As differentiated from the usual, 'physiologic'postoperative paresis, pseudo-obstruction persists for more than 7 days. The pathogenesis of postoperative pseudo-obstruction is complex and as yet partially unknown. Whereas the 'physiologic' postoperative gastrointestinal paresis includes short-term functional cholinergic depression of the visceral organs, in pseudo-obstruction focal lesions in the region of Auerbach's plexus, manifesting as visceral neuromyopathy, are involved. That is why the 'physiologic' postoperative paresis never transforms into paralytic ileus, while in pseudo-obstruction such a risk is potentially involved. The treatment for pseudo-obstruction is as a rule conservative. Surgical treatment (cecostomy) is rarely required. Colonoscopic decompresive suction is usually enough to eliminate the risk of colon rupture due to extensive distention by fast growing meteorism. A patient with postoperative pseudo-obstruction is presented.

Laparoscopic visualization of the cystic artery anatomy.

Uncontrolled bleeding from the cystic artery and its branches is a serious problem that may increase the risk of intraoperative lesions to vital vascular and biliary structures. On laparoscopic visualization anatomic relations are seen differently than during conventional surgery, so proper knowledge of the hepatobiliary triangle anatomic structures under the conditions of laparoscopic visualization is required. We present an original classification of the anatomic variations of the cystic artery into two main groups based on our experience with 200 laparoscopic cholecystectomies, with due consideration of the known anatomicotopographic relations. Group I designates a cystic artery situated within the hepatobiliary triangle on laparoscopic visualization. This group included three types: (1) normally lying cystic artery, found in 147 (73.5%) patients; (2) most common cystic artery variation, manifesting as its doubling, present in 31 (15.5%) patients; and (3) the cystic artery originating from the aberrant right hepatic artery, observed in 11 (5.5%) patients. Group II designates a cystic artery that could not be found within the hepatobiliary triangle on laparoscopic dissection. This group included two types of variation: (1) cystic artery originating from the gastroduodenal artery, found in nine (4. 5%) patients; and (2) cystic artery originating from the left hepatic artery, recorded in two (1%) patients.

Aging and surgery.

Among other things, current science and civilization have enabled us to live longer than ever before. This, in turn, has resulted in a greater proportion of elderly people (aged > or = 65). In Croatia, elderly people accounted for 6.2% of the general population in 1971, and 11.6% in 1991. The greater proportion of the elderly results in increased demands placed upon the health care system, including surgical treatment. Due to the advances in medicine and medical technology, old age itself is not a contraindication for surgical treatment anymore. However, elderly people are more vulnerable to surgical trauma, thus being exposed to a higher surgical risk than young patients. Surgical risk is additionally increased by concomitant diseases typical for old age. Therefore, surgical treatment in the elderly requires strict indications. During the 1993-1998 period, 585 elective and 286 emergency operations in elderly patients were performed at the General Hospital in Zabok. In patients under the age of 65, postoperative mortality was 1.7% after elective and 4.5% after emergency procedures, while in elderly patients the respective figures were 5.6% and 12.0%. This clearly indicates the high level of surgical risk in elderly patients requiring emergency operations.

Biliary duct reoperations.

Conventional operations for cholelithiasis are rarely associated with postoperative complications. However, when the complications do occur, they are frequently life threatening and require reoperation. These reoperations are associated with a considerably higher risk than primary procedures, and require maximal caution and experience from the surgeon. Reoperations are performed in anatomically altered conditions, and in a patient psychically and physically exhausted and in fear from repeat procedure. Therefore, it is of utmost importance for each primary operation including conventional procedure for cholelithiasis to be carried out at a high professional level, using all technologic achievements available that facilitate and improve the surgeon's work safety. In this way, the need of undesired and hazardous reoperations is minimized. The rate of and indications for reoperation in 530 patients operated on by the conventional procedure for cholelithiasis during the 1994-1999 period are presented.

A contribution to the casuistics of choledochal cysts.

Choledochal cyst is a rare cystic anomaly of bile ducts, primarily affecting the choledochus. The etiology of the disease is unknown, while the symptoms predominated by cholangitis usually occur by the age of thirty. The complications of untreated disease include septic complications, biliary cirrhosis, formation of concrements in cystically dilated bile ducts, and a potential risk of cholangiocarcinoma. Two patients with choledochal cysts type III and IV are presented. The patient with type III choledochal cyst underwent radical treatment, whereas in the patient with type IV choledochal cyst only a palliative procedure could be used. Both patients were men older than 40, and were free from the disease associated sequels for two and five years after the surgery.