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Better means to diagnose and define necrotizing enterocolitis are needed to guide clinical practice and research. Adequacy of Bell's staging system for clinical practice and clarity of cases used in NEC clinical datasets has been a topic of controversy for some time. This article provides reasons why a better global definition for NEC is needed and offers a simple alternative bedside definition for preterm NEC called the "Two out of Three" rule. Some argue that biomarkers may fill knowledge gaps and provide greater precision in defining relevant features of a clinical disease like NEC. NEC biomarkers include markers of inflammation, intestinal dysfunction, hematologic changes, and clinical features. Development and reporting of NEC biomarkers should be guided by the FDA's BEST Consensus resource, "Biomarkers, EndpointS, & other Tools" and consistently report metrics so that studies can be compared and results pooled. Current practice in the NICU would be enhanced by clinical tools that effectively inform the clinical team that a baby is at increasing risk of NEC. Ideally, these tools will incorporate both clinical information about the baby as well as molecular signals that are indicative of NEC. While meaningful biomarkers for NEC and clinical tools exist, translation into practice is mediocre.

In the last decades the reported incidence of preterm necrotizing enterocolitis (NEC) has been declining in large part due to implementing comprehensive NEC prevention initiatives, including breast milk feeding, standardized feeding protocols, transfusion guidelines, and antibiotic stewardship and improving the rigor with which non-NEC cases are excluded from NEC data. However, after more than 60 years of NEC research in animal models, the promise of a "magic bullet" to prevent NEC has yet to materialize. There are also serious issues involving clinical NEC research. There is a lack of a common, comprehensive definition of NEC. National datasets have their own unique definition and staging definitions. Even within academia, randomized trials and single center studies have widely disparate definitions. This makes NEC metadata of very limited value. The world of neonatology needs a comprehensive, universal, consensus definition of NEC. It also needs a de-identified, international data warehouse.

Background The true survival benefit of noncurative primary tumor resection in patients with de novo metastatic colorectal cancer (mCRC) remains uncertain. The present study examined the effect of primary tumor resection on systemic inflammation and survival in patients with mCRC. Materials and Methods Consecutive patients with de novo mCRC who had undergone primary tumor resection were identified from a prospective database. Patients were excluded if they had undergone resection of metastases, had undergone delayed primary resection, or if blood samples were unavailable. The neutrophil/lymphocyte ratio (NLR) was used as a biomarker of systemic inflammation. Overall survival (OS) was compared between patient groups according to the pre- and postprimary resection NLR. The associations between the reversal of an elevated NLR and primary tumor bulk or performance status were explored. Results A total of 145 eligible patients were identified from the database, with a median age of 70 years. The baseline NLR was elevated (> 5) in 65 patients, 36 (55%) of whom had a low NLR after surgery. The reversal of an elevated NLR was associated with significantly improved OS (hazard ratio, 0.53; P = .017). A similar benefit was seen after excluding patients undergoing emergency primary resection. NLR reversal was more frequent in patients with larger primary tumors or good performance status. Conclusion The present study is the first to demonstrate a relationship between the reversal of a systemic inflammatory response and the improved survival after primary resection in those with mCRC. A greater effect was seen in patients with large primary tumors. If validated, these observations could guide clinical decision-making in patients with mCRC at presentation.

The asymmetric slab approach and density functional theory (DFT) are used to discuss the interaction of isolated halogen atoms (F, Cl, Br and I) with the Ge(001)c(4 × 2) surface. For each adsorbate on thick slabs we find two stable adatom configurations separated by ~ 0.1 eV. In both configurations, the unsaturated dangling bonds (DB) of the chemisorbed dimers are fully charged due to the interaction of the DB-derived surface states with the bulk states. This behavior is found to be insensitive to whether the calculations are performed using standard ground-state DFT, or DFT supplemented by MBJLDA and spin-orbit corrections to produce an accurate surface electronic structure and energy gap. On chemisorbed ultrathin Ge slabs, however, these unsaturated DB's are empty for the lowest energy configurations. This results in different geometries and energetics for the chemisorbed dimers. A detailed analysis of the predicted scanning tunneling microscopy images of halogen-chemisorbed surfaces is also presented. It is predicted that the halogen atoms may image darkly, yielding filled-state images similar to that of the clean surface, while the empty-state images should be noticeably different.

Using density functional theory and periodic slabs, we have studied water formation via HCl oxidation on the Cu(1 0 0) surface. We show that while adsorbed chlorine increases the stability of water on the Cu(1 0 0) surface, water molecules dissociate immediately when located next to an oxygen atom. We also show that these competing interactions, when arising from HCl reacting with oxygen on Cu(1 0 0), lead to water formation according to two different pathways depending on the temperature and oxygen coverage.

BACKGROUND: Barrett's oesophagus predisposes to adenocarcinoma. However, most patients with Barrett's oesophagus will not progress and endoscopic surveillance is invasive, expensive, and fraught by issues of sampling bias and the subjective assessment of dysplasia. We investigated whether a non-endoscopic device, the Cytosponge, could be coupled with clinical and molecular biomarkers to identify a group of patients with low risk of progression suitable for non-endoscopic follow-up. METHODS: In this multicentre cohort study (BEST2), patients with Barrett's oesophagus underwent the Cytosponge test before their surveillance endoscopy. We collected clinical and demographic data and tested Cytosponge samples for a molecular biomarker panel including three protein biomarkers (P53, c-Myc, and Aurora kinase A), two methylation markers (MYOD1 and RUNX3), glandular atypia, and TP53 mutation status. We used a multivariable logistic regression model to compute the conditional probability of dysplasia status. We selected a simple model with high classification accuracy and applied it to an independent validation cohort. The BEST2 study is registered with ISRCTN, number 12730505. FINDINGS: The discovery cohort consisted of 468 patients with Barrett's oesophagus and intestinal metaplasia. Of these, 376 had no dysplasia and 22 had high-grade dysplasia or intramucosal adenocarcinoma. In the discovery cohort, a model with high classification accuracy consisted of glandular atypia, P53 abnormality, and Aurora kinase A positivity, and the interaction of age, waist-to-hip ratio, and length of the Barrett's oesophagus segment. 162 (35%) of 468 of patients fell into the low-risk category and the probability of being a true non-dysplastic patient was 100% (99% CI 96-100) and the probability of having high-grade dysplasia or intramucosal adenocarcinoma was 0% (0-4). 238 (51%) of participants were classified as of moderate risk; the probability of having high-grade dysplasia was 14% (9-21). 58 (12%) of participants were classified as high-risk; the probability of having non-dysplastic endoscopic biopsies was 13% (5-27), whereas the probability of having high-grade dysplasia or intramucosal adenocarcinoma was 87% (73-95). In the validation cohort (65 patients), 51 were non-dysplastic and 14 had high-grade dysplasia. In this cohort, 25 (38%) of 65 patients were classified as being low-risk, and the probability of being non-dysplastic was 96·0% (99% CI 73·80-99·99). The moderate-risk group comprised 27 non-dysplastic and eight high-grade dysplasia cases, whereas the high-risk group (8% of the cohort) had no non-dysplastic cases and five patients with high-grade dysplasia. INTERPRETATION: A combination of biomarker assays from a single Cytosponge sample can be used to determine a group of patients at low risk of progression, for whom endoscopy could be avoided. This strategy could help to avoid overdiagnosis and overtreatment in patients with Barrett's oesophagus. FUNDING: Cancer Research UK.

The recently proposed modified Becke–Johnson exchange potential with LDA (local density approximation) correlation (MBJLDA) (Tran and Blaha, 2009 [19] ) is employed to study the electronic structure of bulk Ge. Combining this MBJLDA potential with spin–orbit (SO) interactions and LDA pseudopotentials within the plane wave density functional method, leads to results that are generally superior to those obtained from far more sophisticated and computationally expensive methods such as GW. The semiconducting state of bulk Ge is obtained with an indirect energy gap of 0.87 eV and a valence band width of 12.79 eV, in very good agreement with the measured values of 0.74–0.84 eV and 12.6–12.9 eV, respectively. The pressure (lattice constant) dependence of the individual energy levels calculated with the MBJLDA xc potential and SO interactions also provides a good description of the experimental data, equal to that of recent quasiparticle self-consistent GW (QSGW) calculations. Combining the MBJLDA xc potential and SO interactions with GGA (generalised gradient approximation) atomic pseudopotentials led to inferior results for bulk Ge. The relevance of the obtained results for modelling nanostructured Ge is briefly discussed.

The adsorption of lead (Pb) atoms on the clean Si(001)c(4 × 2) reconstructed surface as a function of the adatom coverage is investigated using density functional theory. It is shown that the growth of Pb adatom chains from the most stable monomer configuration, the end-dimer-bridge configuration, proceeds via the formation of inter- and intra-row ad-dimers, and ad-trimers. The calculated energetics of long Pb chains show that the most thermodynamically stable chains are composed exclusively of inter-row dimers, and that monomer termination of these chains is favoured over termination by a dimer.

A new technique was developed for measuring the thickness of can coatings applied to a metal substrate. A metal disc with a known radius creates a small indent in the coating, stopping exactly when the coating thickness is cut through. The indent length is employed to calculate the coating thickness. Accurate measurement of thin films is achieved as the indent is much larger than the respective film thickness. The thickness of epoxy phenolic coatings on tinplate were measured and the results were validated by micrographic cross section analysis and by confocal laser scanning microscopy (CLSM). The coating thicknesses measured using the indentation method coincide with the film thicknesses measured by CLSM, whereas discrepancies were observed using the micrographic cross section analysis. The new technique, presented in this paper, uses simple equipment, is inexpensive, fast and easy to use, and is suitable for film thickness measurements in laboratories and production plants.

First-principles density functional theory and a periodic-slab model have been utilized to investigate the adsorption of a 2-chlorophenol molecule on a CuO(1 1 1) surface with a vacant Cu surface site, namely Cu2O(1 1 1)-CuCUS. Several vertical and flat orientations have been studied. All of these molecular configurations interact very weakly with the Cu2O(1 1 1)-CuCUS surface, an observation which also holds for clean copper surfaces and the Cu2O(1 1 0):CuO surface. Hydroxyl-bond dissociation assisted by the surface was found to be endoergic by 0.42-1.72 eV, depending predominantly on the position of the isolated H on the surface. In addition, the corresponding adsorbed 2-chlorophenoxy moiety was found to be more stable than a vacuum 2-chlorophenoxy radical by about 0.76 eV. Despite these predicted endoergicities, however, we would predict the formation of 2-chlorophenoxy radicals from gaseous 2-chlorophenol over the copper (I) oxide Cu2O(1 1 1)-CuCUS surface to be a feasible and important process in the formation of PCDD/Fs in the post-flame region where gas-phase routes are negligible.

The adsorption of acetone [(CH 3 ) 2 CO] on the Si(0 0 1) surface has been investigated using density functional theory (DFT) and scanning tunneling microscopy (STM). Three distinct features have been observed in the experimental STM images – one single-dimer and two two-dimer wide features. We have considered 32 different possible adsorbate configurations corresponding to the [2 + 2] cycloaddition, dative bonded, α-Hydrogen cleavage, C H bond cleavage, methyl cleavage, cross-dimer bridging, O-dimer insertion, OH cleavage, alcohol-like, end-bridging and dimer-bridging structures. The optimised geometry, binding energy, and simulated filled- and empty-state STM images for each of these possible configurations are presented. These results have facilitated the identification of the three experimentally-observed acetone adsorbate structures.

Raymond Dart is best known today for his groundbreaking research in palaeoanthropology. It is often forgotten, however, that Dart was a scientist of many interests, who made significant contributions to various disciplines. One of these is the study of living non-human primates. Dart became aware of the importance of primate studies and their relevance for research in other disciplines early in his career. In the late 1920s Dart established a colony of captive baboons in the Anatomy Department, University of the Witwatersrand, Johannesburg. On these animals, members of his Department, most notably Joseph Gillman and Christine Gilbert, carried out a number of significant behavioural and endocrinological researches. In 1930, as a member of an Italian Scientific Expedition, Dart was involved in hunting a mountain gorilla (for research purposes). He was also active in primate field studies. In 1957 he and Phillip Tobias founded a Witwatersrand University Uganda Gorilla Research Unit for the study of the Virunga mountain gorillas. The unit produced pioneering studies, conducted by Jill Donisthorpe, on the behaviour of these primates in their natural habitat. At the same time Dart was actively engaged in conservation of the mountain gorillas. He also studied South African chacma baboons in the wild. In the field of primate studies Raymond Dart figures prominently as a pioneering catalyst as well as researcher and conservationist.

Objectives To determine if plasmin differentially augments platelet aggregation through variable efficiencies of IGF–IGFBP complex cleavage. Methods We utilized ADP-triggered platelet aggregation assays to test the effects of IGF-I versus IGF-II in complex with IGFBP-2 or IGFBP-3 upon the efficiency of plasmin (a known IGFBP protease) as a pro-aggregatory stimulus. In vitro proteolysis assays were performed as controls. Results We found that IGF-I complexes augmented platelet-mediated aggregation whereas IGF-II either had no effect (IGFBP-2) or inhibited platelet-mediated aggregation (IGFBP-3). In vitro proteolysis assays of IGFBP-2 and IGFBP-3 using plasmin revealed that three of the four aggregation findings were explained by the disparate efficiencies of IGFBP proteolysis associated with each IGF. Only IGF-II–IGFBP-2 complex resulted in a finding that could not be explained by the concept of differential regulation of plasmin’s proteolysis efficiency by the two IGF ligands. Conclusions Our findings demonstrate that the plasmin can differentially modulate platelet aggregation in response to intrinsic heterogeneities within the IGF axis.

The interaction between a 2-chlorophenol (C 6H 4OHCl) molecule and the Cu(1 1 1) surface has been investigated using density functional theory as an initial step in gaining a better understanding of the catalyzed formation of dioxin compounds on a clean copper surface. The 2-chlorophenol molecule is found to form several weakly bonded, horizontally and vertically oriented configurations. Dissociative modes have also been investigated. For the latter, the formation of phenyl and benzyne fragments is found to be more energetically favourable than the formation of 2-chlorophenoxy radicals.

We present the results of a combined study using scanning tunneling microscopy (STM) and density functional theory (DFT) of the interaction of acetone [(CH3)2CO] with the Si(0 0 1) surface. Three distinct adsorbate features were observed using atomic-resolution STM. One of the features appears as a bright protrusion located above a Si–Si dimer, while the other two are asymmetric about the dimer row and involve a second neighboring Si–Si dimer. One of the two asymmetric features has a protrusion located between the two dimers, while the other has a protrusion which is located at the site of a single dimer and exhibits a dimer sized depression on the adjacent dimer. DFT calculations have been performed for two structures; the four-membered ring structure and dissociation structure. Our calculations show that the bright single-dimer sized feature observed in the STM images could be attributed to either of these two calculated structures. However, neither of the two calculated structures can explain the appearance of the two-dimer wide asymmetric features observed in the experiment.

We have studied single Si dangling bonds on the Si(0 0 1) surface using scanning tunnelling microscopy (STM) and density functional theory (DFT) calculations. The Si dangling bonds are created by the chemisorption of single hydrogen atoms forming a Si–Si–H hemihydride. At room temperature, the hemihydride induces static buckling on adjacent Si–Si dimers. In the STM measurements, we observe that the orientation of the static buckling pattern can be reversed with tip-sample bias and influenced by the substrate doping. Our DFT calculations yield a correlation between the electron occupancy of the hemihydride Si dangling bond and the buckling orientation around it.

The sediments in the western side of the Makapansgat Limeworks were either precipitated as speleothems, represented in the earlier massive deposits, or were deposited as coarsening clastic sediments, mainly representing later deposits. Between the earlier deposits and the main sedimentary phase, the stratigraphic sequence was inverted twice to a considerable height by the unusual deposition of subaqueous speleothem. Bone-bearing deposits, including the Main Quarry Bone Breccia and the well-known Grey Breccia belong, in time, to the lower part of the clastic deposits called the Red Silts. Australopith fossils have been found in the Grey Breccia dumped material and, in situ, from the dolomite clast breccia on the Main Quarry entrance buttress. Whatever the problems may be in provenancing some of the material from the Limeworks dumps, there is no doubt that the three rows of blocks on the southern side of the dumps belong to the Grey Breccia, and other rows contain red sediment sufficient for them to be safely associated with the Red Silts. There is no reason why this material should not be prepared with confidence as to its stratigraphic provenance. In any case, stratigraphic evidence, presented here, shows that there is little difference in time between the deposition of the bone-bearing breccias.

The mean expectation of life has greatly increased from such early hominins as Australopithecus africanus to modern Homo sapiens, but the curve of change has not been smooth and uninterrupted. There was a decided drop in life expectancy with the emergence of early Homo as represented by Homo habilis and more young-age deaths are evident in the fossil record of the latter. A similarly low expectation of life was evident in Homo erectus. The critical determinants of this drop are laid at the door of two factors. The first one is the deterioration of Africa's ancient climate that accompanied major tectonic uplift along the eastern flank of the continent. This appears to have had a seriously deleterious effect on the chances of children surviving to procreative age, thus dropping the population's mean life expectancy. This change in the demographic pattern must have been especially marked in the presence of nutrition-demanding elevated encephalisation. Thus, a second critical determinant of the lowering of mean life expectancy, accompanying the change to a ‘high risk’ demographic pattern, is inferred to have been the dramatic and surprising increase in brain size and encephalisation. This development of a brain burst was untimely, for it seems to have come after 2.5 Ma, when the climate of Africa showed the aforementioned marked deterioration. Only after the time of H. erectus, in whom encephalisation had attained 70–80% of that of modern H. sapiens, did humans' mean life expectancy increase. In these late stages of hominin evolution, increases in life expectancy and in brain size appeared to accompany one another.

Specimen Stw 53 was recovered in 1976 from Member 5 of the Sterkfontein Formation. Since its incomplete initial description and comparison, the partial cranium has figured prominently in discussions about the systematics of early Homo. Despite publication of a preliminary reconstruction in 1985, Stw 53 has yet to be compared comprehensively to other Plio-Pleistocene fossils or assessed systematically. In this paper, we report on a new reconstruction of this specimen and provide a detailed description and comparison of its morphology. Our reconstruction differs in important respects from the earlier one, especially in terms of neurocranial length, breadth, and height. However, given that Stw 53 exhibits extensive damage, these dimensions are most likely prone to much error in reconstruction. In areas of well-preserved bone, Stw 53 shares many cranial features with Homo habilis, and we propose retaining it within this species. We also consider the affinities of dental remains from Sterkfontein Member 5, along with those from Swartkrans and Drimolen previously assigned to Homo. We find evidence for sympatry of H. habilis and Australopithecus robustus and possibly Plio-Pleistocene Homo sapiens sensu lato in Sterkfontein Member 5. At Swartkrans and Drimolen, we find evidence of H. habilis. We also compare the morphologies of Stw 53 and SK 847 and find compelling evidence to assign the latter specimen to H. habilis, as has been proposed.

It is shown that large-diameter, finite and extended, hydrogenated, single-walled carbon nanotubes are energetically and structurally unstable. The instability of short, large-diameter, finite hydrogenated tubes leads to the formation of hydrogenated circular carbon tori of small tubular cross-section. It is also shown that carbon toroidal structures, formed by desorption of hydrogen from the hydrogenated tori, are more energetically stable than the corresponding open-ended, finite single-walled carbon nanotubes.

In this article, the authors describe the use of piezoelectric sensors and actuators for the prediction of milling tool stability lobes, since existing methods for predicting tool stability have disadvantages which limit their practical use. An experimental approach is described whereby modal testing is performed using surface-mounted piezoelectric sensors and actuators to generate a prediction of tool instability due to regenerative chatter. The approach is first demonstrated by synthetic modal analysis based upon a finite element model of a cantilever beam. Laboratory tests are then performed on small milling tools, and it is shown that there is good agreement with alternative methods for predicting stability. It is concluded that the proposed technique may be more readily suited to automation, and is more appropriate for use on very small milling tools.

Ab initio plane-wave pseudopotential density functional theory (DFT) calculations have been performed to determine the atomic and electronic structure of the Si(0 0 1)2 × 1–Li adsorption system at 1.0 monolayer (ML) coverage. Chemisorption of the lithium atoms is found to result in a minimum energy configuration characterized by symmetric Si dimers in agreement with the results of high-resolution core-level photoelectron spectroscopy. The transition from the asymmetric Si dimers of the clean Si(0 0 1) surface to the symmetric dimers of the Li chemisorbed surface is due to charge transfer from the Li adatoms to the substrate. The dispersion of the occupied electronic surface state bands is found to be in good agreement with the angle-resolved photoemission data. The nature of the lowest energy unoccupied surface state band suggests that silicide formation may occur at coverages greater than 1.0 ML.

The energetics and relative stability of infinite and finite, clean and hydrogenated open-ended Si nanotubes is investigated using the extended Brenner potential. The calculations show that the excess strain energy of infinite clean Si tubes is reduced when the tubes are hydrogenated on both sides of the tubular shell. For finite Si tubes the total energy exhibits a minimum which reflects a balance between the strain energy of the shell and the chemical energy of the open ends. If hydrogen atoms are chemisorbed on the outer surface of finite Si nanotubes, the tubes show a tendency to close their open ends. For very short, large-diameter tubes, topologically different structures are formed––hydrogenated silicon tori.

The plane-wave pseudopotential density functional theory method has been used to study the Si(0 0 1)2 × 1–K adsorption system for 0.5 and 1.0 monolayer coverage. The minimum energy atomic configuration for 0.5 monolayer coverage was found to correspond to the potassium atom in each 2 × 1 surface unit cell occupying the valley bridge site. A double-layer model was determined to be the optimised geometry of the Si(0 0 1)2 × 1–K chemisorption system for 1.0 monolayer coverage. The geometry of this double-layer model was found to be in good agreement with the current experimental data. A detailed analysis of the electronic structure of this double-layer model has also been performed. The overall dispersion of the occupied and unoccupied surface state bands has been shown to be in excellent agreement with the angle-resolved and inverse photoemission data. The nature and dispersion of the surface states of the double-layer model in the vicinity of the energy gap provide evidence of strong interactions, both between the two inequivalent potassium atoms in each 2 × 1 surface unit cell, and between these adatoms and the underlying substrate.

Since Dart’s analysis of the Taung skull in1925 in Nature, there has been controversy surrounding the presence of a clearly defined lunate sulcus (LS) in the australopithecines, marking the anterior extent of primary visual cortex (PVC). An anterior position signifies that the LS is in an ape-like position, such as found in Pan troglodytes. A posterior position is a more human-like characteristic (autapomorphy). If the latter occurred in Australopithecus, then the cerebral cortex underwent some neurological reorganization prior to brain enlargement, thus occurring earlier than the emergence of the genus Homo. The endocast of the Stw 505 specimen from Sterkfontein, South Africa, shows an unmistakably posterior placement of the LS. The early hominid brain was reorganized at least by the time of Australopithecus africanus, thus vindicating Dart’s early assessment. To cite this article: R.L. Holloway, C. R. Palevol 3 (2004).

Several models have been proposed in the literature for the initial stages of the dissociative chemisorption of silane (SiH 4 ) on the Si(1 1 1)7 × 7 surface. In this paper, geometry optimisation calculations using the extended Brenner empirical potential have been performed to determine which of these models yields the minimum energy structure. The lowest energy configurations are found to correspond to the dissociation of silane into SiH 2 and two hydrogen atoms. The minimum energy structure involves the adsorption of the two hydrogen atoms onto the dangling bonds of an adjacent adatom and rest atom, and the insertion of the remaining SiH 2 fragment into one of the adatom backbonds. These results are discussed in the light of the existing experimental data.

We demonstrate that the total energy of finite, open-ended, single-walled carbon nanotubes is determined by a balance between the elastic energy due to the curvature of a tube and the chemical energy due to the dangling bonds at the open ends of a tube. The differences in total energy and radius between the most energetically stable zig-zag and armchair tubes, increases with increasing number of atoms in the tubes.

Laser ablation/ionization mass spectrometry (LAMS) of particulate matter (PM) was undertaken on-line in order to extend and contrast PM characterization. Qualitative on-line LAMS results for certified materials and Toronto source materials demonstrated the versatility and limitations of the technique. The observation of organic and inorganic components of certified materials verified the proper working condition of the in-house on-line LAMS. Organic and inorganic components of Toronto source materials were also observed with the on-line LAMS. Common components identified from both types of materials were Na, Al, Ca, Fe, and K. Other recognized components were compared with marker elements reported for some common PM emission sources. An in-house off-line LAMS was used to analyze urban Toronto PM deposited on glass substrates, while the on-line LAMS analyzed individual urban Toronto PM particles that were introduced directly into the instrument. Scanning electron microscopy (SEM), X-ray spectrometry and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for confirmatory purposes. Organic and inorganic components of urban Toronto PM at their typical ng/m3 concentrations were successfully observed in mass spectra using both off-line LAMS and on-line LAMS. Identified ions unique to each analyzed material were compared to identified ions of urban Toronto PM. The ability of LAMS to analyze individual respirable PM particles (viz.2 microns), both for inorganic trace elements and for organic components, greatly extended our capability to characterize PM and also to achieve estimates of concentration contributions of each material.

Previous studies have suggested that GST genotypes may play a role in determining susceptibility to lung cancer, though the data are often conflicting. In this study we investigated GSTM1, GSTT1 and GSTP1 status in relation to lung cancer risk in patients attending a Manchester bronchoscopy clinic. Cases were all patients (n=94) currently with, or with a history of, tumours of the lung, trachea or bronchus. The control group were all other patients (n=165) who were free of benign and malignant tumours both at the time of, or prior to, diagnosis. All patients were interviewed for information on lifestyle risk factors, and DNA extracted from bronchial lavage and blood samples was used for genotyping. GSTM1 null genotype was associated with decreased lung cancer risk (odds ratio (OR) 0.50, 95% confidence interval (CI) 0.29-0.87), particularly among men (OR 0.43, 95% CI 0.21-0.87) and those above the median age (OR 0.33, 95% CI 0.15-0.70). No difference in GSTT1 and GSTP1 genotype distribution was seen between cases and controls. The GSTM1 null genotype was associated with a decreased risk of squamous cell carcinoma: the OR, adjusted for age, sex and pack years was 0.32 (95% CI 0.12-0.82). As previous studies have reported that the GSTM1 null genotype is associated with an increased lung cancer risk, further work is required to determine whether the observed association is true, or whether it arises from bias or confounding factors.

Descriptions are provided of 27 hominin cranial specimens recovered from Member 4 of the Sterkfontein Formation between 1968 and 1994. Provisional statements of taxonomic affinity are given. The principal conclusion of this overview is that the bulk of the cranial remains from Member 4 are attributable to Australopithecus africanus or are consistent with the anatomy of that species, while some others are indeterminate. No specimen can be assigned confidently to a known species other than A. africanus. However, two specimens document the possibility that a second, possibly new species is represented among the Member 4 hominins, although such a species is difficult to characterize on cranial evidence alone.

Focal small bowel perforation (FSBP) is a life-threatening event that predominantly affects extremely low birth weight (ELBW) infants. Histopathology from surgical specimens of ileum with FSBP shows a healthy mucosa overlying a thinned muscularis with segmental degeneration. Clinical data strongly support an association between early postnatal administration of dexamethasone (EPD) and FSBP. Additional risk factors, including gestational age, administration of prophylactic indomethacin, and severity of illness, may be synergistic with EPD for the pathogenesis of perforations. Animal models of dexamethasone administration show morphologic changes in the ileum, similar to those seen in ELBW infants, including increased mucosal maturation and thinning of the muscularis. These tissue-specific differences may be mediated by a perturbation in growth factor expression or accumulation. In support of this hypothesis, dexamethasone has been associated with increased IGF-I immunolocalization in the mucosa and decreased immunolocalization in the muscularis. The known growth-promoting functions of IGF-I are consistent with the observed dexamethasone-associated changes within both the mucosa and the muscularis. Ongoing studies in this animal model are exploring the potential mechanisms by which dexamethasone might affect IGF-I availability.

Stw 505 is the most complete hominin cranium discovered in Sterkfontein Member 4 since Broom's excavations. It was found in situ in Member 4 breccia in 1989 and is larger, on the whole, than any other cranium from Sterkfontein that has comparable parts. Displacement due to breakage, as well as plastic deformation, has affected Stw 505 in several areas, especially the face and the vault. Diagnosticmorphology is nevertheless abundant in the specimen. In several areas-the distinct anterior pillar, the straight inferior border of the zygoma, the pattern of cresting on the naso-alveolar clivus, the basal aspect of the temporal bone-Stw 505 closely matches the morphology of specimens of Australopithecus africanus and is distinct from other hominins. Some isolated characters overlap with other groups, mainly early Homo and/or A. robustus. However, only the hypodigm of A. africanus can accommodate the entire suite of morphology.In some cases, Stw 505 introduces more variation into the Sterkfontein sample. For example, prominent superciliary eminences occupy the medial portions of the supraorbital region and flow medially into a strongly protruding glabellar mound. These characteristics are probably attributable to sexual dimorphism. In many respects, Stw 505 highlights similarities between A. africanus and early Homo. Comparison with other species suggests that males of A. africanus do not show derived features of A. robustus that are not also present in females, and that cranial differences between A. afarensis and A. africanus have, if anything, been understated.

A comprehensive study of atomic hydrogen chemisorption on the Si(1 1 1) √3 × √3R30 ° -Al, -Ga and -B cluster modelled surfaces is presented using Hartree-Fock/density functional theory methods. Extrapolation of the results to the extended (1 1 1) silicon surface is also discussed. It is found that the chemisorption of hydrogen on the Al and Ga terminated surfaces induces a transition from the √3 × √3 structure to a local 1 × 1: H-like reconstruction with a stable SiAl (or SiGa) sites. The subsurface boron induced √3 × √3 reconstruction is also lifted by hydrogen chemisorption but, in this case, boron adatoms are likely to be segregated on the surface, predominantly as BH or/and BH 2 .

We have used an extended form of the Brenner empirical hydrocarbon potential to study the reconstructions of the clean β-SiC(001) surface, and the chemisorption of C2H2 and CH3 molecules onto the silicon terminated (2 × 1) surface. For reference, chemisorption energies and minimum-energy geometries have also been obtained from Becke3LYP HF/DFT cluster calculations. Optimal C2H2 chemisorption at low coverage was found to occur with the adsorbate molecule situated above the cave site, with the carbon-carbon bond oriented in the [110] direction parallel to the dimer rows. At 1 monolayer coverage this was also the preferred structure, with the adsorbate molecules positioned in a staggered c(2 × 2) arrangement. Optimal CH3 chemisorption was found to occur with the CH3 radicals bonding directly to the surface dangling bonds.

The chemisorption of atomic hydrogen on the Si(111)-(√3 × √3)R30°-Al and -Ga surfaces has been studied by first-principles all-electron Hartree-Fock/density functional theory (DFT) cluster calculations. It has been found that the hydrogen chemisorption behaviour on the Ga terminated cluster modelled surface is similar to that for the Al terminated cluster. Hydrogen atoms chemisorbing near an adatom site are found to cause the breaking of SiAl (or SiGa) bonds and the formation of HSi bonds. The aluminium (or gallium) adatoms move from their original threefold sites to the adjacent bridge sites (one hydrogen atom), and then to the neighbouring on-top sites (two hydrogen atoms). Calculations of the binding energies have shown that aluminium or gallium adatoms occupying the bridge and on-top sites may be able to migrate on the real surface. This suggests the possible formation of Al (or Ga) islands, together with a local (1 × 1)H surface reconstruction. Further exposure to hydrogen does not cause any further structural transformations and supports the (√3 × √3)-(1 × 1) phase transition.

First principles all-electron Hartree-Fock and density functional theory cluster calculations have been performed to investigate the chemisorption of atomic hydrogen on the Si(111)√3 × √3R30°-B surface. Both the equilibrium geometries corresponding to n hydrogen atoms (1 ≤ n ≤ 5) chemisorbing on the B-S5 and B-T4 reconstructed structures, and the desorption energies for a silicon or boron adatom bonded to x hydrogen atoms (0 ≤ x ≤ 3), have been obtained. As successively more hydrogen is chemisorbed, a silicon or boron adatom is found to move from its original threefold site to an adjacent bridge site, and then to a neighbouring on-top site. It is also found that boron will most likely occupy a subsurface substitutional S5 site at low hydrogen coverages (≤ 0.67ML), but appear as an adatom at an on-top site directly above one of the first-layer silicon atoms for hydrogen exposures higher than 0.67 ML. This boron segregation at high hydrogen exposures prevents the formation of SiH2 and SiH3 complexes and leads to the prediction that only SiH and BH2 will be observed on an Si(111):B hydrogenated surface. It also provides an explanation for the lack of Si surface etching at high hydrogen exposure. All of these results are in good agreement with the available experimental data on hydrogenated B/Si(111) surfaces.

Ab initio Hartree-Fock-DFT cluster calculations have been performed of the interaction of hydrogen with the Si(111)7 × 7 surface. These calculations have enabled the determination of the various equilibrium structures which result when up to five hydrogen atoms are allowed to adsorb near the adatom and rest atom sites of the Si(111)7 × 7 surface. As progressively more hydrogen atoms are chemisorbed near an adatom site, each hydrogen-bonded adatom is found to move from its original three-fold (T4) site (one hydrogen atom) to an adjacent bridge site (two and three hydrogen atoms), and then on-top of a neighbouring first layer silicon atom (more than three hydrogen atoms). The lowest calculated adatom desorption energy is found to be 2.40 eV and corresponds to the desorption of SiH2 from above a neighbouring first layer silicon atom. In contrast to an adatom, a hydrogen-bonded rest atom is found to remain close to its original three-fold equilibrium position. The smallest rest atom desorption energy is 2.10 eV and corresponds to an SiH3 surface complex.

Chemisorption of C 2 H 2 and CH 3 molecules onto the dimerized (001) surface of silicon has been simulated using the extended Brenner potential. For reference, chemisorption energies and minimum-energy geometries have also been obtained from Hartree-Fock and Becke3LYP DFT calculations performed with the Gaussian-94 suite. Various chemisorption sites have been identified. Optimal C 2 H 2 chemisorption was found to occur in a cross-dimer configuration, parallel to the dimer rows. Optimal CH 3 chemisorption occurred with the CH 3 bonding directly to the surface dangling bonds. A second-layer chemisorption site for CH 3 has also been identified, which may be important in the formation of diamond films on a silicon substrate.

The widely used Stillinger-Weber potential for silicon interactions has been modified to provide an accurate description of the Si(111)-(7 × 7) surface including the highly reactive adatom and rest-atom sites. This modified potential also provides a good representation of bulk silicon, and the Si(001)-(1 × 1), Si(001)-(2 × 1), Si(111)-(1 × 1) and Si(111)-(2 × 1) surfaces. Above the melting temperature of 1683 K, however, the original Stillinger-Weber potential is probably superior.

The first-principles all-electron Hartree-Fock/density functional method contained within the Gaussian92/DFT package has been employed to study the chemisorption of atomic chlorine onto small clusters modelling the adatom and restatom sites of the Si(111)7 × 7 surface. Both the equilibrium configurations and the binding energies of the various SiClx complexes (1 ≤ x ≤ 3) produced by the adsorption of up to six chlorine atoms in the vicinity of an adatom and restatom site, have been determined. As progressively more chlorine atoms are adsorbed near these chemisorption sites, the surface topology is found to reconstruct to yield stable configurations for SiCl, SiCl2 and SiCl3. A chlorine bonded adatom is observed to move from its original three-fold T4 site (one chlorine atom) to an adjacent bridge site (two and three chlorine atoms), and then on-top of a neighbouring first layer silicon atom (more than three chlorine atoms). Similar behaviour is exhibited by the restatom except that movement towards the on-top position occurs when three chlorine atoms are chemisorbed, rather than four as in the adatom case. The lowest binding energies are determined to be 0.74 eV for SiCl3 desorption from a restatom site and 0.80 eV for the removal of SiCl2 from an adatom site. Our results also suggest that a relatively low fluence of chlorine should produce a stable chlorosylil layer consisting of SiCl on the restatom sites and SiCl3 on the adatom sites, and yielding a saturation coverage of 1.35 mL. Increased chlorine exposure should result in further uptake at the restatom sites to produce SiCl3 complexes at both chemisorption sites and a maximum saturation coverage of 1.84 ML. Both of these predictions appear consistent with experiment.