Intermediate Defects Research Articles

Anorectal malformations in children

<b>Background/Purpose: </b> Anorectal malformations are one of the most common congenital defects. This study was undertaken to study the hospital incidence of anorectal malformations (ARM), frequency of various types of defects, their sex distribution and the spectrum of anomalies associated with ARM. The effect of presence of an associated defect on mortality and morbidity was also studied.<br><b> Materials and Methods:</b> One hundred consecutive children attending the pediatric surgery department were included in this study. A detailed history was taken, and examination was performed for the primary as well as the associated defects. Appropriate investigations like invertogram, cologram were done wherever indicated. Management was as per the standard protocol. The data was recorded and analyzed. <br><b> Results:</b> Out of the 100 patients, 51 were males and 49 females. One out of every 6.62 admission was for ARM. Twenty percent of the female babies had high, 76% intermediate and 4% had low anomalies, whereas 80.39% males had high, 3.92% intermediate and 15.6% showed low malformations. Ten percent of the patients had pouch colon. Associated anomalies were seen in 33 patients - 20 males and 13 females; 19 in high, 10 in intermediate, 1 in low group and 3 children with cloacal malformations. Associated defects seen were urogenital (17%), cardiovascular (7%), gastrointestinal (9%), genital (5%) and limb defects (7%). There were 8 deaths, and complications were seen in 13 patients. Ten patients had two or more defects associated with ARM.<br><b> Conclusions:</b> Anorectal malformations occurred equally in males and females. Females had intermediate defects more frequently, rectovestibular fistula being the commonest. Males were more likely to have high lesions; anorectal agenesis without fistula was the commonest defect. The most common associated defects seen were vesicoureteric reflux and esophageal atresia. Complications were seen more commonly in males with high lesions. There was a significant association between presence of an associated defect and mortality and morbidity.

Growth-dependent optical properties of 3,4,9,10-perylenetetracarboxylicacid-dianhydride (PTCDA) films on Ag(1 1 1)

We measured photoluminescence (PL) and photoluminescence excitation (PLE) spectra of thin films of 3,4,9,10-perylenetetracarboxylicacid-dianhydride (PTCDA) grown by vacuum sublimation on the Ag(1 1 1) surface. Our aim was to study the influence of the film structure and growth morphology on the optical properties. PTCDA films grown on Ag(1 1 1) at low temperatures correspond to the β bulk phase, whereas films grown at high temperatures consist of clusters corresponding to the α bulk phase of PTCDA. Hence, films with a thickness of 30 ML were grown for preparation temperatures ranging from 180 to 420 K. For the films grown at the ends of this temperature interval, we find similar spectra, indicating a small influence of the different structures of two phases. In the transition range, however, considerable intensity changes and new blue-shifted (in PL) and red-shifted features (in PLE) are detected. The significant changes are attributed to the formation of intermediate phases or structural defects (e.g., stacking faults) perhaps involving self-trapped excitons.

Self-vacancies in gallium arsenide: Anab initiocalculation

We report here a reexamination of the static properties of vacancies in GaAs by means of first-principles density-functional calculations using localized basis sets. Our calculated formation energies yields results that are in good agreement with recent experimental and {\it ab-initio} calculation and provide a complete description of the relaxation geometry and energetic for various charge state of vacancies from both sublattices. Gallium vacancies are stable in the 0, -, -2, -3 charge state, but V_Ga^-3 remains the dominant charge state for intrinsic and n-type GaAs, confirming results from positron annihilation. Interestingly, Arsenic vacancies show two successive negative-U transitions making only +1, -1 and -3 charge states stable, while the intermediate defects are metastable. The second transition (-/-3) brings a resonant bond relaxation for V_As^-3 similar to the one identified for silicon and GaAs divacancies.

Application of impact-echo technique in diagnoses and repair of stone masonry structures

The impact-echo technique is traditionally used to determine position of intermediate and large defects within concrete structures. In this paper, application of the impact-echo technique for assessment of bonding condition between the facing stones, mortar, and inner rubble core in stone masonry structures is discussed. In addition, results of field testing on a historic Canadian stone masonry building is presented, which illustrates the capabilities of an impact-echo system to help with evaluating the structural stability of critical components, particularly the bonding conditions and presence of voids and cavities.

The C terminus of sigma(32) is not essential for degradation by FtsH.

A key step in the regulation of heat shock genes in Escherichia coli is the stress-dependent degradation of the heat shock promoter-specific sigma(32) subunit of RNA polymerase by the AAA protease, FtsH. Previous studies implicated the C termini of protein substrates, including sigma(32), as degradation signals for AAA proteases. We investigated the role of the C terminus of sigma(32) in FtsH-dependent degradation by analysis of C-terminally truncated sigma(32) mutant proteins. Deletion of the 5, 11, 15, and 21 C-terminal residues of sigma(32) did not affect degradation in vivo or in vitro. Furthermore, a peptide comprising the C-terminal 21 residues of sigma(32) was not degraded by FtsH in vitro and thus did not serve as a recognition sequence for the protease, while an unrelated peptide of similar length was efficiently degraded. The truncated sigma(32) mutant proteins remained capable of associating with DnaK and DnaJ in vitro but showed intermediate (5-amino-acid deletion) and strong (11-, 15-, and 21-amino-acid deletions) defects in association with RNA polymerase in vitro and biological activity in vivo. These results indicate an important role for the C terminus of sigma(32) in RNA polymerase binding but no essential role for FtsH-dependent degradation and association of chaperones.

Serial changes on quantitative myocardial perfusion SPECT in patients undergoing revascularization or conservative therapy

Background. Little is known about changes of myocardial perfusion in patients undergoing coronary revascularization or medical therapy. The purpose of this observational study was to assess the long-term effects of revascularization or conservative therapy on serial quantitative myocardial perfusion single photon emission computed tomography (SPECT). Methods and Results. The study population consisted of 421 patients who underwent serial rest thallium-201/stress technetium-99m sestamibi dual-isotope myocardial perfusion SPECT with at least a 1-year interval between the 2 studies and who had abnormal quantitative scan results on the first stress SPECT. The mean interval between scans was 32.7 ± 15.9 months. Patients were divided into 3 groups according to stress defect extent: group 1 had small stress defects (4%-10%, n = 145), group 2 had intermediate stress defects (>10%-20%, n = 144), and group 3 had extensive stress defects (>20%, n = 132) at baseline. Forty patients in group 1, 44 in group 2, and 54 in group 3 underwent coronary revascularization between 2 SPECT studies; the others had conservative therapy. In group 3 patients with revascularization, stress defect extent and reversible defect extent were remarkably reduced (14.5% ± 13.6% and 13.1% ± 12.5%, respectively; both P < .0001), with greater improvement in those patients reporting increased use of cardiac medications; resting defect extent was slightly reduced (1.9% ± 6.4%, P < .05). In group 3 patients with conservative therapy, a small reduction in stress defect extent was noted (2.3% ± 8.3%, P < .05). In group 2, there were modest, similar reductions in reversible defect extent in both the patients with revascularization (2.7% ± 7.7%, P < .05) and those with conservative therapy (1.8% ± 7.3%, P < .05), as well as a small but significant reduction in stress defect extent in those with conservative therapy (2.1% ± 8.2%, P < .05). In group 1 patients, no significant changes in stress, rest, or reversible defect extent were found with either therapy. Conclusions. The findings of this study show that improvement in quantitative myocardial perfusion abnormalities over time occurs in some patients with either revascularization or conservative therapy and suggest that, in patients with extensive defects, greater improvement may be seen in those who undergo revascularization. (J Nucl Cardiol 2001;8:428-37.)

A large PEST-like sequence directs the ubiquitination, endocytosis, and vacuolar degradation of the yeast a-factor receptor.

The yeast a-factor receptor (encoded by STE3) is subject to two modes of endocytosis, a ligand-dependent endocytosis as well as a constitutive, ligand-independent mode. Both modes are associated with receptor ubiquitination (Roth, A.F., and N.G. Davis. 1996. J. Cell Biol. 134:661-674) and both depend on sequence elements within the receptor's regulatory, cytoplasmically disposed, COOH-terminal domain (CTD). Here, we concentrate on the Ste3p sequences required for constitutive endocytosis. Constitutive endocytosis is rapid. Receptor is synthesized, delivered to the cell surface, endocytosed, and then delivered to the vacuole where it is degraded, all with a t1/2 of 15 min. Deletion analysis has defined a 36-residue-long sequence mapping near the COOH-terminal end of the Ste3p CTD that is the minimal sequence required for this rapid turnover. Deletions intruding into this interval block or severely slow the rate of endocytic turnover. Moreover, the same 36-residue sequence directs receptor ubiquitination. Mutants deleted for this sequence show undetectable levels of ubiquitination, and mutants having intermediate endocytosis defects show a correlated reduced level of ubiquitination. Not only necessary for ubiquitination and endocytosis, this sequence also is sufficient. When transplanted to a stable cell surface protein, the plasma membrane ATPase Pma1p, the 36-residue STE3 signal directs both ubiquitination of the PMA1-STE3 fusion protein as well as its endocytosis and consequent vacuolar degradation. Alanine scanning mutagenesis across the 36-residue-long interval highlights its overall complexity-no singular sequence motif or signal is found, instead required sequence elements distribute throughout the entire interval. The high proportion of acidic and hydroxylated amino acid residues in this interval suggests a similarity to PEST sequences-a broad class of sequences which have been shown to direct the ubiquitination and subsequent proteosomal degradation of short-lived nuclear and cytoplasmic proteins. A likely possibility, therefore, is that this sequence, responsible for both endocytosis and ubiquitination, may be first and foremost a ubiquitination signal. Finally, we present evidence suggesting that the true signal in the wild-type receptor extends beyond the 36-residue-long sequence defined as a minimal signal to include contiguous PEST-like sequences which extend another 21 residues to the COOH terminus of Ste3p. Together with sequences identified in two other yeast plasma membrane proteins, the STE3 sequence defines a new class of ubiquitination/endocytosis signal.

Precursor defect to the vacancy-dioxygen center in Si.

In a recent paper [Phys. Rev. B 50, 11 531 (1994)] we have tentatively attributed two new infrared bands at 914 cm $^{\mathrm{\ensuremath{-}}1}$ and 1000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, in neutron-irradiated Czochralski-grown silicon, to a [VO+${\mathrm{O}}_{\mathit{i}}$] structure that was considered to develop as an intermediate stage in the process of conversion of a VO center to a ${\mathrm{VO}}_{2}$ complex upon heat treatment. As a continuation of this work, we further investigate [VO+${\mathrm{O}}_{\mathit{i}}$] structure and the formation of intermediate defects. In addition, we present semiempirical calculations of the localized vibrational mode frequencies of the [VO+${\mathrm{O}}_{\mathit{i}}$] defect. The results are consistent with the experimental observations. \textcopyright{} 1996 The American Physical Society.

Complete atrioventricular septal defects: the influence of associated cardiac anomalies on surgical management and outcome

Major associated cardiac anomalies are known to increase the risk of repair of complete atrioventricular septal defects (CAVSDs). The purpose of this study was to examine the effects of such anomalies on the current surgical management of CAVSDs and their influence on outcome following repair. We performed a retrospective review of a 100 consecutive non-isomeric patients undergoing repair of CAVSD at our institution, between January 1989 and December 1994; patients with partial or intermediate defects were excluded. Complete atrioventricular septal defect patients with other major cardiac abnormalities (complex) were then compared to those with isolated CAVSDs. There were 15 patients (15%) with associated anomalies; 3 had tetralogy of Fallot, 1 patient had pulmonary atresia, 6 had hypoplastic left or right ventricle, 1 had tetralogy of Fallot and hyperplastic right ventricle, 2 patients had double outlet right ventricle, 1 had hypoplastic aortic arch and 1 patient had aortic coarctation. The median age at operation was similar for both groups (4.2 months), while the median weight was not significantly different for isolated CAVSDs compared to complex (4.2 months vs 3.4 months, P = 0.89), but there was a higher incidence of trisomy 21 (70/85, 82% vs 8/15, 53.3%, P = 0.01). Two of the 85 isolated CAVSD patients (2.3%) had undergone palliative pulmonary artery banding, while 5 of the 15 complex patients (33.3%) had either banding or Blalock-Taussig shunts performed. The technique of CAVSD repair was identical in each group. All complex patients had standard repair of their associated anomalies. Hospital mortality was higher in the complex group (3/15, 20% vs 2/85, 2.3%, P = 0.004); all early deaths in the complex group occurred in patients with a hypoplastic ventricle. Reoperation for left atrioventricular valve regurgitation was required in six isolated CAVSD patients (7.1%) and in one complex (6.6%). In the absence of significant ventricular hypoplasia, the early results of surgical repair in patients with CAVSDs and associated cardiovascular anomalies are similar to those achieved in patients with isolated CAVSD.

Diffuse and localised visual field defects to automated perimetry in primary open angle glaucoma.

The occurrence of generalised or diffuse visual field depression in primary open angle glaucoma (POAG), in contrast to the presence of characteristic localised defects, is controversial. The frequency of diffuse visual field loss to automated static perimetry in the early stages of POAG was determined and compared with the frequency of localised defects. Twenty-five eyes of 25 consecutive POAG patients who met the selection criteria were tested on the Humphrey Visual Field Analyser with the Central 30-2 Threshold Test. Patients' mean age was 68 years. All eyes had visual acuity better than 6/9 with correction, refractive error of less than +/- 7 dioptres, no media opacities and normal pupils (3-6 mm). For all eyes, the frequency of abnormality on the STATPAC Total Deviation (TD) and Pattern Deviation (PD) plots were determined for all individual test points. Mean values and standard deviations were compared. The TD plots represent a composite of both diffuse and localised visual field depression, while PD plots are intended to reflect localised field defects. The frequency of involvement of the test points on the TD plots was higher than on the PD plots (mean +/- SD: 41.5 +/- 11.2% vs 27.5 +/- 10.9%) for all presenting defects. When only deep defects (STATPAC p < 1% and p < 0.5%) were evaluated, TD involvement was still more frequent than the PD (20.1 +/- 9.4% vs 13.2 +/- 7.2%). The topographical pointwise incidence of pure generalised sensitivity loss in the visual field was less frequent when only deep defects were taken into consideration (6.9 +/- 5.7%), and the incidence increased progressively with the inclusion of intermediate and shallow field defects (9.6 +/- 6.8% and 14.0 +/- 8.4% respectively). A component of diffuse sensitivity depression is present at all significant levels of visual field loss in glaucoma. This component of generalised loss decreases as the depth of the field defects increases. This finding suggests that early diffuse field loss converts into well-defined pattern defects at later stages.

Controlled Environment [Ecell] Tem for Dynamic In-Situ Reaction Studies with Hrem Lattice Imaging

AbstractWith a controlled environment electron microscope it is possible to remove the effect of another atmosphere, such air, to which the sample may have become exposed; to study in considerable detail the continuous development of a series of microstructures in a dynamic process, to identify important intermediate phases and defects in them which may only be metastable under specific reaction conditions of atmosphere and temperature, and to establish whether they are the origin, or merely the consequence, of the reaction. In this paper we report the extensive modification of a high resolution transmission electron microscope (Philips CM30T HRTEM) to add facilities for dynamic in-situ gas-solid reaction studies in a controlled atmosphere of gas or vapor at pressures of 0–50mbar which replaces the regular high vacuum TEM environment. The new environmental cell (ECELL) capability is combined with the original 0.23nm TEM resolution, STEM (BF/ADF) imaging and chemical and crystallographic analyses. Regular specimen holders are used; including hot stages capable of temperatures &gt;1000°C. The full TEM resolution has been demonstrated at temperatures above 700°C and with limited (mbar) amounts of gas flowing through the integral 4-aperture differentially pumped ECELL (and with the additional pumps for the system operating). The ECELL system can be used to preserve, or if necessary to recreate, a continuous chain of evidence in a chemical reaction process.

Defects and stress analysis of the Raman spectrum of diamond films

Diamond films were deposited on silicon substrates at 750 °C, by the hot-filament technique, from a reactive CH 4 (0.1–2%) H 2 mixtures. Two wide Gaussian lines around 1330 and 1500 cm −1 with coupled variations in the whole preparation range appeared in the global Raman spectra. They were attributed to intermediate carbon defects in the diamond crystallites, which might control the confinement length of diamond phonons. Their contributions to the diamond line shift and width for all the samples is calculated and compared with the experimental results. The remaining shift is attributed to the stress (up to 1.2 GPa), while the origin of the remaining widening (large distribution of stress or Raman inactive additional defects) is discussed.

Molecular beam epitaxial growth: simulation and continuum theory

We present results of atomistic simulations of an ideal MBE growth process in 1 + 1 dimensions and make a connection with continuum models of interface growth. We argue that the KPZ equation is not the relevant continuum equation for MBE growth at intermediate temperatures, where overhangs and bulk defects can be neglected. Instead, a fourth-order linear equation gives the same growth exponents obtained in the numerical simulations but leads to unphysical properties of the long-time surface morphology. We propose a new non-linear growth equation different from the KPZ equation, as the relevant dynamical equation for ideal MBE growth.

Scalp expansion flaps

A mean 5 year review of 20 patients who had surgery for localised alopecia of the scalp is presented. The technique of using scalp expansion flaps is described and evaluated: it is associated with a low morbidity and high patient satisfaction rate; it provides an excellent one-stage procedure for intermediate size defects and, in the frontal area, for larger defects. Particular emphasis is laid on making incision lines at right angles to the direction of hair growth in order to cover stretched scars, and in performing Z-plasties when closing small scalp defects. Finally, a rationale for the treatment of localised areas of baldness according to their size is put forward.

Defect structure and transport properties of manganous sulphide

It has been shown that above 800 K manganous sulphide demonstrates a simple defect structure which can be described in terms of a point defect model. Over the major part of the phase field of MnS the predominant defects are doubly ionized cation vacancies and electron holes (Mn 1− y S) while near and at the Mn/MnS phase boundary doubly ionized interstitial cations and quasi-free electrons predominate (Mn 1+ y S). In the intermediate range intrinsic ionic defects predominate at lower temperatures and intrinsic electronic disorder prevails at higher temperatures.

Dislocation Nucleation Models From Point Defect Condensations in Silicon and Germanium

ABSTRACTThe process of dislocation nucleation from point defect condensations in Si(Ge) is discussed. Based on the assumption that during the dislocation nucleation stage, the dominant factor in the configurational energy is the number of dangling bonds per point defect incorporated, rather than the more commonly recognized factor of strain energy, it is possible to model the dislocation nucleation process. In order to minimize the number of dangling bonds, point defects would condense into row configurations elongated in &lt;110&gt;, called intermediate defects (IDC), and then the IDCs would evolute into undissociated 90° edge –, 60°, and Frank partial dislocations.

Undissociated Dislocations and Intermediate Defects in as+ Ion Damaged Silicon

ABSTRACTUndissociated dislocation dipoles and intermediate defects are detected in As+ ion damaged Si using the lattice resolution technique of transmission electron microscopy. The present results are consistent with our proposed dislocation nucleation models.