Quantitative analysis of charge transfer plasmons in silver nanocluster dimers using semiempirical methods.

Plasmonic metal nanoclusters are widely used in chemistry, nanotechnology, and biomedicine. In metal nanocluster dimers, coupling of the plasmons leads to the emergence of two distinct types of modes: (1) bonding dipole plasmons (BDP), which occurs when charge oscillates synchronously within each nanocluster, and (2) charge transfer plasmons (CTP), which occurs when charge oscillates between two conductively linked nanoclusters. Although TDDFT-based modeling has uncovered some trends in these modes, it is computationally expensive for large dimers, and quantitative analysis is challenging. Here, we demonstrate that the semiempirical quantum mechanical method INDO/CIS enables us to quantify the CTP character of each excited state efficiently. In end-to-end Ag nanowire dimers, the longitudinal states have CTP character that decreases with increasing gap distance and nanowire length. In side-by-side dimers, the transverse states have CTP character and generally larger than in the end-to-end dimers, particularly for the longer nanowires. In side-by-side dimers where one nanowire is shifted along the length of the other, the CTP character of the longitudinal states peaks when the dimer is shifted by two Ag-Ag bond lengths, while the transverse states show decreasing CTP character as displacement increases. In the larger Ag31+ nanorod dimers, CTP character follow a similar distance dependence to that seen in the small nanowire but have smaller overall CTP character than the nanowires. Our study demonstrates that INDO/CIS is capable of modeling metal nanocluster dimers at a low computational cost, making it possible to study larger dimers that are difficult to analyze using TDDFT.

Hydride- and halide-substituted Au9(PH3)83+ nanoclusters: similar absorption spectra disguise distinct geometries and electronic structures.

Ligands dramatically affect the electronic structure of gold nanoclusters (NCs) and provide a useful handle to tune the properties required for nanomaterials that have high performance for important functions like catalysis. Recently, questions have arisen about the nature of the interactions of hydride and halide ligands with Au NCs: hydride and halide ligands have similar effects on the absorption spectra of Au9 NCs, which suggested that the interactions of the two classes of ligands with the Au core may be similar. Here, we elucidate the interactions of halide and hydride ligands with phosphine-protected gold clusters via theoretical investigations. The computed absorption spectra using time-dependent density functional theory are in reasonable agreement with the experimental spectra, confirming that the computational methods are capturing the ligand-metal interactions accurately. Despite the similarities in the absorption spectra, the hydride and halide ligands have distinct geometric and electronic effects. The hydride ligand behaves as a metal dopant and contributes its two electrons to the number of superatomic electrons, while the halides act as electron-withdrawing ligands and do not change the number of superatomic electrons. Clarifying the binding modes of these ligands will aid in future efforts to use ligand derivatization as a powerful tool to rationally design Au NCs for use in functional materials.

Direct Anti-Markovnikov Addition of Water to Olefin To Synthesize Primary Alcohols: A Theoretical Study.

Anti-Markovnikov addition of water to olefins has been a long-standing goal in catalysis. The [Rh(COD)(DPEphos)]+ complex was found as a general and regioselective group 9 catalyst for intermolecular hydroamination of alkenes. The reaction mechanism was adapted for intermolecular hydration of alkenes catalyzed by a [Rh(DPEphos)]+ catalyst and studied by DFT calculations. Olefin hydration pathways were analyzed for anti-Markovnikov and Markovnikov regioselectivity. On the basis of the DFT results, the operating mechanism can be summarized as follows: styrene activation through nucleophilic attack by OHδ- of water to alkene with simultaneous Hδ+ transfer to the Rh; this is then followed by formation of primary alcohol via reductive elimination. The competitive formation of phenylethane was studied via a ß-elimination pathway followed by hydrogenation. The origin of the regioselectivity (Markovnikov vs anti-Markovnikov) was analyzed by means of studying the molecular orbitals, plus natural atomic charges, and shown to be primarily orbital-driven rather than charge-driven.

Computational Analysis of Transition Metal-Terminal Boride Complexes.

A computational analysis of model transition-metal terminal boride [MB(PNPR)] complexes is reported. A combination of density functional theory methods, natural bond orbital analysis, and multiconfiguration self-consistent field calculations were employed to investigate the structure and bonding of terminal boride complexes, in particular, the extent of metal dπ-boron pπ bonding. Comparison of metal-boride, -borylene, and-boryl bond lengths confirms the presence of metal-boron π bonds, albeit the modest shortening (∼3%) of the metal-boron bond suggests that the π-bonding is very weak in terminal borides. Calculated free energies of H2 addition to the boride complexes to yield the corresponding boryl complexes indicate that metal-boride π-bond strengths are 22 kcal/mol or less as compared to 44 kcal/mol for an analogous nitride complex. It is concluded that, for the boride complexes studied, covering a range of different 4d and 5d metals, that the metal-boride bond consists of a reasonably covalent σ but two very polarized metal-boron π bonds. The high polarization of the boron-to-metal π bonds indicates that the terminal boride is an acceptor or Z-type ligand.

Heterobimetallic Silver-Iron Complexes Involving Fe(CO)5 Ligands.

Iron(0) pentacarbonyl is an organometallic compound with a long history. It undergoes carbonyl displacement chemistry with various donors (L), leading to molecules of the type Fe(CO)x(L)5-x. The work reported here illustrates that Fe(CO)5 can also act as a ligand. The reaction between Fe(CO)5 with the silver salts AgSbF6 and Ag[B{3,5-(CF3)2C6H3}4] under appropriate conditions resulted in the formation of [(µ-H2O)AgFe(CO)5]2[SbF6]2 and [B{3,5-(CF3)2C6H3}4]AgFe(CO)5, respectively, featuring heterobimetallic {Ag-Fe(CO)5}+ fragments. The treatment of [B{3,5-(CF3)2C6H3}4]AgFe(CO)5 with 4,4'-dimethyl-2,2'-bipyridine (Me2Bipy) and Fe(CO)5 afforded a heterobimetallic [(Me2Bipy)AgFe(CO)5][B{3,5-(CF3)2C6H3}4] species with a Ag-Fe(CO)5 bond and a heterotrimetallic [{Fe(CO)5}2(µ-Ag)][B{3,5-(CF3)2C6H3}4] with a (CO)5Fe-Ag-Fe(CO)5 core, respectively, illustrating that it is possible to manipulate the coordination sphere at silver while keeping the Ag-Fe bond intact. The chemistry of [B{3,5-(CF3)2C6H3}4]AgFe(CO)5 with Et2O and PMes3 (Mes = 2,4,6-trimethylphenyl) has also been investigated, which led to [(Et2O)3Ag][B{3,5-(CF3)2C6H3}4] and [(Mes3P)2Ag][B{3,5-(CF3)2C6H3}4] with the displacement of the Fe(CO)5 ligand. X-ray structural and spectroscopic data of new molecules as well as results of computational analyses are presented. The Fe-Ag bond distances of these metal-only Lewis pairs range from 2.5833(4) to 2.6219(5) Å. These Ag-Fe bonds are of primarily an ionic/electrostatic nature with a modest amount of charge transfer between Ag+ and Fe(CO)5. The ν̅(CO) bands of the molecules with Ag-Fe(CO)5 bonds show a notable blue shift relative to those observed for free Fe(CO)5, indicating a significant reduction in Fe→CO back-bonding upon its coordination to silver(I).

Balloon valvuloplasty for critical aortic stenosis in a fetus: a case report.

The mortality and morbidity of fetal aortic stenosis (AS) depend on the degree of the hemodynamic effects of the stenosis, and left ventricular (LV) adaptation, development and function during fetal life. In the case of critical AS, the development of hydrops and death in utero are well recognized entities. A 23-week gestation fetus was diagnosed with critical severe AS, cardiomegaly, a dilated LV with very poor contractility, and mitral regurgitation. There was a reversal of flow in the aortic arch through the ductus arteriosis and a reversed a-wave in the ductus venosus on Doppler examination. The fetus had hydrops with ascites, and massive scalp, face and skin edema. Fetal amniocentesis was normal. Aortic valvuloplasty was performed under general anesthesia and echocardiographic guidance. Pericardial effusion was not observed after the procedure. However, LV function could not be ameliorated and continued to diminish. There was no cardiac activity in the fetus two hours after the intervention. Aortic valvuloplasty in utero for AS is technically feasible. Mortality is mainly associated with technical errors, LV function, and the degree of endofibroelastosis in the effected fetuses.

Prenatal diagnosis of abnormal course of umbilical vein and ductus venosus agenesis: report of three cases.

Ductus venosus connecting the portal and embryonic venous circulation into the inferior vena cava has a crucial role in fetal circulation. The absence of ductus venosus is a rare anomaly, in which the umbilical vein connection to the venous system may be extrahepatic, bypassing the liver or intrahepatic via the portal venous system. We report three cases of ductus venosus agenesis with associated anomalies. In two of them the connection was directly to the right atrium, whereas the umbilical vein drained to the left internal iliac artery in the third case.

HELLP syndrome: 8 years of experience from a tertiary referral center in western Turkey.

OBJECTIVE: This study was performed to determine the incidence, symptomatology, complications, mode of delivery, treatment modalities, and risk factors for maternal outcome and perinatal outcome in women with HELLP syndrome. METHODS: A total of 303 pregnancies with hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome diagnosed antenatally were reviewed between 2002 and 2009. Demographic data, including age, parity, gestational age, and clinical and laboratory findings, were recorded from the medical files. In addition, delivery route, indication of cesarean section, and fetal and maternal complications were determined. RESULTS: Acute renal failure (20.5%) was the most common complication. Eclampsia was present in 303 women with HELLP syndrome (52%). There were four maternal deaths (1.4%). The perinatal mortality rate was 20.3%. The percentages of intracerebral hemorrhage and maternal death were higher in women with eclampsia than in those without (6.3% vs. 0.8%, p = 0.01 and 4.8% vs. 0.4%, p = 0.02, respectively). A nadir platelet count of ≤50,000 cells/mm(3), a peak serum AST of >150 IU/L, and a peak serum LDH of ≥1400 IU/L were not independent risk factors of an adverse outcome. CONCLUSION: We concluded that the incidence rates of serious maternal and fetal morbidities and mortalities are increased in HELLP syndrome. Laboratory parameters of HELLP syndrome are not independent risk factors for adverse neonatal-maternal outcome. Adequate and prompt diagnosis and management are crucial in patients with HELLP syndrome.

Prenatal diagnosis of aortopulmonary window.

Aortopulmonary window (APW) is a rare congenital heart malformation. It refers to a connection between the ascending aorta and the pulmonary trunk before bifurcation. We report a case of APW that was detected by prenatal fetal echocardiography. The diagnosis was confirmed postnatally with an additional partial anomalous pulmonary venous connection. Corrective surgery was performed at the age of 1 week. Prenatal diagnosis of APW is important because an operation early after birth is required to prevent congestive heart failure due to high pulmonary blood flow. It is essential to visualize the aortopulmonary septum during fetal echocardiographic examination.

Associated anomalies and outcome of fetal aberrant right subclavian artery.

PURPOSE: To determine the frequency of aberrant right subclavian artery among the low-risk fetuses and to evaluate its association with chromosomal abnormalities and the other congenital heart diseases. METHODS: A total of 4,125 consecutive fetuses were examined for the presence of aberrant right subclavian artery that arises from the descending aorta distal to the left subclavian artery. RESULTS: Aberrant right subclavian artery was detected in 17 cases (0.4%). In nine cases it was an isolated finding. In four cases (23.5%) it was accompanied by another cardiac defect. Extracardiac malformations were present in three fetuses (17.6%). Among the 13 cases of aberrant right subclavian artery in which the karyotypes were known, one case presented with Down syndrome (7.6%). In this fetus, aberrant right subclavian artery was the only finding. CONCLUSION: These findings suggest that aberrant right subclavian may be an isolated finding in trisomy 21. The visualization of subclavian artery should be a part of fetal echocardiographic examination as it may be a valuable marker for Down syndrome.

Prenatal sonographic diagnosis of tuberous sclerosis complex.

We report the case of a male fetus with tuberous sclerosis complex (TSC), in whom multiple cardiac rhabdomyomas and renal angiomyolipomas were detected at 33 weeks by ultrasound with additional brain lesions detected on MRI, all confirmed after birth. DNA analysis of the TSC2 gene detected a de novo mutation in the TSC2 gene. Postnatal follow-up and neurological examination were normal, as were the results of Holter monitoring.

Counseling and outcomes of antenatally diagnosed congenital heart anomalies in Turkey.

OBJECTIVE: To determine the clinical outcomes and decisions of families of fetuses with prenatally-diagnosed cardiac abnormalities. METHODS: Prenatally diagnosed cases (n=155) with congenital heart disease were retrospectively categorized according to the Allan-Huggon grading system: Group A (cardiac disease associated with severe / lethal extracardiac disease); Group B1 (low risk with a postnatal prognosis); Group B2 (moderate risk, amenable to surgical repair with a low mortality); and Group B3 (high risk, associated with high mortality after surgery). Neonatal outcomes, including termination of pregnancy, were recorded for 18 months of follow-up after counseling the parents. Student's t-test, Mann-Whitney U, Pearson's Chi-square test and Fischer's exact Chi-square test were used for statistical analyses. RESULTS: One hundred forty-five cases completed follow up. Thirty-nine cases (Group A) were associated with extracardiac lethal defects and the pregnancies were terminated; these cases were excluded from statistical evaluation. Twenty parents in Group B3 opted also for termination. The survival rates of ongoing pregnancies after 18 months of follow-up between the three cardiac abnormality Groups (Group B1, n=37; Group B2, n=12; and Group B3, n=37) were 89.2%, 66.7%, and 13.5%, respectively. Significance was present between the survival rates of the three Groups [Group B3 vs. Group B1: p=0.0001; OR: 52.8 (12.9-214.5); Group B3 vs. Group B2: p=0.0009; OR: 12.8 (2.8-58.9); Group B2 vs. Group B1: p=0.087; OR: 4.12 (0.84-20.2)]. CONCLUSION: Our practice and the findings reported herein support the efficacy of this staging system and counseling parents of fetuses for congenital heart diseases.

Cesarean techniques in cases with one previous cesarean delivery: comparison of modified Misgav-Ladach and Pfannenstiel-Kerr.

AIM: To compare the effectiveness of the Pfannenstiel-Kerr method (PKM) or modified Misgav-Ladach method (MMLM) in previous cesarean sections (C/Ss). METHODS: Hundred and fifteen gravidas were included with previous one C/S, using either a PKM or MMLM. Demographic characteristics, operative outcomes, surgical complications, and neonatal outcomes were compared in two groups. RESULTS: The mean operative time (18.0 ± 3.5 vs. 23.5 ± 5.7 min; p < 0.0001) and mean extraction time (90.1 ± 41.2 vs. 208.1 ± 79.1 s; p < 0.0001) were significantly shorter in the MMLM group than the PKM group. Postoperative recovery (mobilization, normalization of bowel function, need for analgesics, time to oral feeding, and intra-operative blood loss) was similar between the MMLM and PKM groups. CONCLUSION: The MMLM appears to be a faster alternative to PKM for previous C/Ss, with similar results as in previous studies with primary CSs.

Preeclampsia due to fetal non-immune hydrops: mirror syndrome and review of literature.

OBJECTIVE: Mirror syndrome (Ballantyne's syndrome) refers to the association of fetal hydrops and maternal preeclampsia. The aim of this study was to determine the relation and incidence between fetal hydrops and preeclampsia in our clinic. METHODS: A retrospective review of patients associated with fetal hydrops and findings with preeclampsia was used. Seventy-five cases with single pregnancy and diagnoses with nonimmune hydrops fetalis were found. According to the data 4 cases were found related with preeclampsia. RESULTS: Mirror syndrome is rarely encountered and underdiagnosed. We found a frequency of 5.3% (4 cases in 75 affected pregnancies) for single non-immune hydrops cases in which maternal hypertension occurred. Fetal outcome is depending on etiology and prognosis is mainly very low. Maternal symptoms and laboratory findings are resolving after intrauterine fetal death or delivery. CONCLUSION: Hydrops fetalis must be considered as a potential risk factor for preeclampsia. It is important that this clinical condition has a potential of about 5% for proceeding preeclampsia.

Comparison of perinatal and maternal outcomes of severe preeclampsia, eclampsia, and HELLP syndrome.

OBJECTIVE: To compare maternal and perinatal outcomes in pregnancies complicated by severe preeclampsia, eclampsia, and HELLP (hemolysis, elevated liver enzyme levels, and low platelets) syndrome. MATERIALS AND METHODS: Maternal and neonatal charts of 1,222 consecutive pregnancies complicated by severe preeclampsia, eclampsia, or HELLP syndrome at our maternal-perinatal unit were reviewed. Patients were divided into three groups: 903 (73.9%) with severe preeclampsia, 123 (10.1%) with eclampsia, and 196 (16.0%) with HELLP syndrome. RESULTS: The overall incidence of adverse maternal outcome was 5.9%. The rates of adverse maternal outcomes for women with HELLP syndrome and eclampsia were higher than for severe preeclampsia (13.8% vs. 11.4% vs. 3.4%, respectively) (p=0.000). Birth weight was lower in patients with HELLP syndrome than in patients with eclampsia and severe preeclampsia (p=0.005). No significant difference in neonatal morbidity was found among the three groups. Perinatal mortality tended to be higher in the severe preeclampsia group than in the HELLP syndrome and eclampsia groups (p=0.231). CONCLUSION: Pregnancies complicated by HELLP syndrome had significantly higher maternal morbidity than those with severe preeclampsia and eclampsia. Perinatal and neonatal outcomes in pregnancies complicated by severe preeclampsia, eclampsia, and HELLP syndrome were dependent on gestational age rather than being disease dependent.

Twin pregnancies complicated by a single malformed fetus: chorionicity, outcome and management.

The objective of this study was to evaluate the impact of one abnormal fetus in a twin pregnancy, to compare impact of chorionicity and clinical outcome of intervention and expectant management. Thirty-seven dichorionic (DC) twins and 18 monochorionic (MC) twins complicated with one malformed fetus were evaluated for gestational age, birthweight and perinatal outcome. Six hundred and forty-two twin pregnancies were evaluated in the database. The control groups consisted of 429 DC and 86 MC twins without anomalous fetus. Mean birthweight and gestational age at birth for DC control group were (n = 429; 2137g and 34.71 weeks), DC study group, n = 37; 2117g (p = .338) and 33.97 weeks (p = .311), and DC study group with major malformations, n = 30; 2019g (p = .289) and 33.3 weeks (p = .01), and showed only significance for gestational age. There was no statistical significance between MC control group, n = 86; 2097g and 34.93 weeks, and MC study group, n = 18; 2237g (p = .338), and 34.42 weeks (p = .502). Because of limited data, the preliminary evaluation for expectant management and intervention, and survival of at least one normal fetus showed no impact. We conclude that, although, all DC twin pregnancies have a risk for preterm delivery, DC twins complicated with major malformation of one twin, have a lower mean gestational age at birth. Preliminary results for intervention does not improve fetal outcome for DC and MC twins and needs further evaluation with greater studies of impact or review.

Prenatal diagnsis of intracardiac hamartoma and Turner syndrome.

Turner syndrome is associated with a higher frequency of heart defects detected prenatally when compared to postnatal reports. The most common heart defects detected prenatally are hypoplastic left heart syndrome and coarctation of the aorta. We report a case involving a fetus at 16 gestational weeks with a septated cystic hygroma located on the neck and head, an interventricular septal mass, a hypoplastic left ventricle due to aortic stenosis, mitral stenosis, and a hypoplastic aortic arch with a karyotype of mos 45, X, [47 cells]/47, XXX [3 cells]. The autopsy findings confirmed our prenatal diagnosis with a final diagnosis of Turner syndrome and congenital cardiac vascular malformation.

Prevalence and distribution of congenital abnormalities in Turkey: differences between the prenatal and postnatal periods.

The aim of this study was to determine the distribution of cases associated with congenital abnormalities during the following three periods: pregnancy, birth, and the neonatal period. This was a retrospective study of cases between 2002 and 2006. All abnormal pregnancies, elective terminations of pregnancies, stillbirths, and births with congenital abnormalities managed in the Neonatology Unit were classified based on the above distribution scheme. During the 5-year study period, 1906 cases with congenital abnormalities were recruited, as follows: 640 prenatally detected and terminated cases, with most abnormalities related to the central nervous system, chromosomes, and urogenital system (56.7%, 12.7%, and 8.9%, respectively); 712 neonates with congenital abnormalities (congenital heart disease [49.2%], central nervous system abnormalities [14.7%], and urogenital system abnormalities [12.9%]); and hospital stillbirths, of which 34.2% had malformations (220 prenatal cases [34.4%] had multiple abnormalities, whereas 188 liveborn cases [26.4%] had multiple abnormalities). The congenital abnormalities rate between 2002 and 2006 was 2.07%. Systematic screening for fetal anomalies is the primary means for identification of affected pregnancies.