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.

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).

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.

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.

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 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.

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.

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.

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.

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.

Multidisciplinary approach in cystic hygroma: prenatal diagnosis, outcome, and postnatal follow up.

BACKGROUND: The aim of the present study was to determine prenatal follow up and clinical outcome in fetuses born with cystic hygroma. METHODS: A series of 64 cystic hygroma patients, who were diagnosed in the first and the second trimester of pregnancy, was enrolled. Associated structural abnormalities, karyotype analysis and pregnancy outcome were studied. Survivors were followed for their fetal outcome and prognosis. RESULTS: There were 64 new cases of cystic hygroma in 8524 subjects screened (0.75%). Thirty-nine (60.9%) were of non-septated and 25 (39.1%) were of septated cystic hygroma. Chromosomal abnormalities were present in 25 (39.1%). The most common abnormality in non-septated cystic hygroma was trisomy 21 (10, 27.8%), and that in septated cystic hygroma was Turner syndrome (5, 23.8%). Associated structural malformations are common in cystic hygroma and overall survival was poor. Nine of the present infants were live-born and were subsequently followed up. Two had cardiac pathology and died after cardiac operation, two others were diagnosed with axillary cystic hygroma, had an excellent prognosis and responded well to treatment, and another two had cranial findings with mild neurological sequel. Only three cases had, at birth and in the follow-up period, no complications. CONCLUSION: Cystic hygroma is highly correlated with adverse perinatal outcome. Prenatal diagnosis and invasive procedures are vital for counselling with close follow-up after delivery for appropriate medical support. A multidisciplinary approach is strictly recommended in live-born children.

Prenatal diagnosis of porencephaly secondary to maternal carbon monoxide poisoning.

Porencephaly is defined as an area of focal encephalomalacia that communicates with the ventricular system, giving the appearance of a dilated ventricle. It is assumed that vascular occlusion or an infectious process cause gray and white matter necrosis leading to cyst formation in the cerebral parenchyma. Possible etiology of porencephaly includes intracerebral thrombosis, intracranial hemorrhage and fetal infection. We report the first antenatal diagnosis of porencephaly, which apparently resulted from maternal carbon monoxide poisoning.

Fetal therapy in twin reserve arterial perfusion sequence pregnancies with alcohol ablation or bipolar cord coagulation.

OBJECTIVE: We aimed to evaluate perinatal outcome of seven pregnancies with twin reserve arterial perfusion sequence. MATERIALS AND METHODS: Study group included seven cases of acardiac twins. Out of seven acardiac twins, two cases were followed without interventions. We performed four alcohol ablation and one bipolar coagulation. For alcohol ablation, a 20-gauge needle guided with color Doppler USG was directed to abdominal insertion site of the single umbilical artery of the acardiac twin, and 1.0-2.0 mL of absolute alcohol was injected. For bipolar coagulation of the umbilical cord, we used 3.5 mm laparoscopic trocar and 3.0 mm bipolar forceps. The procedures were performed under the guidance of transabdominal ultrasonography. RESULTS: Gestational age of the cases at diagnosis and at delivery was 15-32 and 17-38 weeks, respectively. Two cases without intervention were lost at 17 and 32 weeks. The mean time of procedure for bipolar coagulation and alcohol ablation were 30 and 10 min, respectively. One of the four cases of alcohol ablation group was aborted although alcohol ablation was successful. Another one case was aborted after alcohol ablation due to lost of fetal cardiac activity of the pump fetus. In two other cases, umbilical cord ablation with alcohol was successful, and they delivered live birth at 36 and 38 weeks. In one case, we performed bipolar cord coagulation successfully, and the case delivered live birth at 39 weeks. The overall survival rate for intrauterine surgery was 60% (N 3/5). CONCLUSION: In twin reserve arterial perfusion sequence pregnancies with findings of poor prognosis, alcohol ablation or bipolar cord coagulation as fetal therapy under the guidance of ultrasonography can be done successfully, and should be offered as a choice to families upon discussion of intervention or follow-up with own complications.

When should we perform prophylactic antibiotics in elective cesarean cases?

OBJECTIVE: The aim of this study was to determine whether the timing of prophylactic antibiotics at cesarean delivery influences maternal and neonatal infectious morbidity. STUDY DESIGN: This was a prospective, randomized trial. Four hundred patients that underwent elective cesarean section between June and December 2007 formed the study population. Eleven patients were excluded from the study because they needed transfusion during the cesarean section. The population was divided into two groups: Group A, antibiotic prophylaxis was applied to 194 women before skin incision and Group B, antibiotic prophylaxis was applied to 195 women after umbilical cord clamping. The occurrence of endomyometritis/endometritis, wound infection, febrile morbidity, total infectious morbidity, and neonatal complications were compared. RESULTS: There were 389 patients enrolled. No demographic differences were observed between groups. No significant difference was found between the groups for total infectious morbidity [relative risk (RR) 1.39, 95% confidence interval (CI) 0.71-2.69] and endometritis (RR 1.40, 95% CI 0.43-4.51). There was no increase in neonatal sepsis (RR 1.47, 95% CI 0.61-3.53), sepsis workup (RR 1.35, 95% CI 0.75-2.42), need for neonatal intensive care (RR 1.77, 95% CI 0.51-6.16), and intensive care stay period (P = 0.16). CONCLUSIONS: Time of antibiotic prophylaxis application does not change maternal infectious morbidity in cesarean section deliveries. Preoperative prophylaxis application does not affect neonate morbidity rates as stated in literature.

Prenatal diagnosis of lissencephaly: a case report.

We describe the abnormal sonographic findings in the brain of a 26-week fetus, which increased the suspicion of isolated lissencephaly. Follow-up ultrasound examination and MRI depicted diffuse cortical agyria, microcephaly, hypotelorism, and proptosis. Cordocentesis showed a normal 46,XY karyotype, and no short arm deletion of chromosome 17 was detectable. Postmortem examination confirmed complete agyria of the whole fetal brain. Early detection of fetal microcephaly and other cranial abnormalities can be a sign of isolated lissencephaly and need to be evaluated carefully with ultrasound and MRI for detection of abnormal cortical development of the fetal brain.

Prenatal diagnosis of schizencephaly with 2D-3D sonography and MRI.

We report a case of schizencephaly diagnosed prenatally at 23 weeks of gestational age with two-dimensional (2D) and three-dimensional (3D) sonography and fetal brain MRI, confirmed by autopsy. The diagnostic method of choice is 2D transabdominal and transvaginal sonography, whereas additional 3D sonography and MRI may provide a better understanding of the pathology and related findings.

Prenatal diagnosis of VACTERL syndrome and partial caudal regression syndrome: a previously unreported association.

We describe a case of VACTERL syndrome associated with type 1 unilateral caudal regression syndrome. The abnormal sonographic findings at 26 weeks included hemivertebrae, scoliosis, hypoplastic and deformed lumbar spine and sacrum, preaxial polydactyly on the left hand, duplicated hallux on the left foot and hemihypoplasia of the left lower limb, bilateral club foot, and single umbilical artery. Postmortem examination confirmed prenatal sonographic findings with additional findings of supernumerary rib at the lumbar level and anal atresia.