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We used the PW high-repetition laser facility VEGA-3 at Centro de Láseres Pulsados in Salamanca, with the goal of studying the generation of radioisotopes using laser-driven proton beams. Various types of targets have been irradiated, including in particular several targets containing boron to generate α-particles through the hydrogen–boron fusion reaction. We have successfully identified γ-ray lines from several radioisotopes created by irradiation using laser-generated α-particles or protons including 43Sc, 44Sc, 48Sc, 7Be, 11C and 18F. We show that radioisotope generation can be used as a diagnostic tool to evaluate α-particle generation in laser-driven proton–boron fusion experiments. We also show the production of 11C radioisotopes, $\approx 6 \times 10^{6}$, and of 44Sc radioisotopes, $\approx 5 \times 10^{4}$ per laser shot. This result can open the way to develop laser-driven radiation sources of radioisotopes for medical applications.
Numerous types of analyses for factorial designs having unequal cell frequencies have been discussed in the literature. These analyses test either weighted or unweighted marginal means which, in turn, correspond to different model comparisons. Previous research has indicated, however, that these analyses result in biased (liberal or conservative) tests when cell variances are heterogeneous. We show how to obtain a generally robust and powerful analysis with any of the recommended nonorthogonal solutions by adapting a modification of the Welch-James procedure for comparing means when population variances are heterogeneous.
Community involvement in research is key to translating science into practice, and new approaches to engaging community members in research design and implementation are needed. The Community Scientist Program, established at the MD Anderson Cancer Center in Houston in 2018 and expanded to two other Texas institutions in 2021, provides researchers with rapid feedback from community members on study feasibility and design, cultural appropriateness, participant recruitment, and research implementation. This paper aims to describe the Community Scientist Program and assess Community Scientists' and researchers' satisfaction with the program. We present the analysis of the data collected from 116 Community Scientists and 64 researchers who attended 100 feedback sessions, across three regions of Texas including Northeast Texas, Houston, and Rio Grande Valley between June 2018 and December 2022. Community Scientists stated that the feedback sessions increased their knowledge and changed their perception of research. All researchers (100%) were satisfied with the feedback and reported that it influenced their current and future research methods. Our evaluation demonstrates that the key features of the Community Scientist Program such as follow-up evaluations, effective bi-directional communication, and fair compensation transform how research is conducted and contribute to reducing health disparities.
Introduction: The Cunningham reduction method for anterior shoulder dislocation offers an atraumatic alternative to traditional reduction techniques without the inconvenience and risk of procedural sedation and analgesia (PSA). Unfortunately, success rates as low as 27% have limited widespread use of this method. Inhaled methoxyflurane (I-MEOF) offers a rapidly administered, minimally invasive option for short-term analgesia. We conducted a pilot study to evaluate the feasibility of studying whether I-MEOF increased success rates for atraumatic reduction of anterior shoulder dislocation. Methods: A convenience sample of 20 patients with uncomplicated anterior shoulder dislocations were offered the Cunningham reduction method supported by methoxyflurane analgesia under the guidance of an advanced care paramedic. Operators were instructed to limit their attempt to the Cunningham method. Outcomes included success rate without the requirement for PSA, time to discharge, and operator and patient satisfaction with the procedure. Results: 20 patients received I-MEOF and an attempt at Cunningham reduction. 80% of patients were male, median age was 38.6 (range 18-71), and 55% were first dislocations of that joint. 35% (8/20 patients) had reduction successfully achieved by the Cunningham method under I-MEOF analgesia. The remainder proceeded to closed reduction under PSA. All patients had eventual successful reduction in the ED. 60% of operators reported good to excellent satisfaction with the process, with inadequate muscle relaxation being identified as the primary cause of failed initial attempts. 80% of patients reported good to excellent satisfaction. Conclusion: Success with the Cunningham technique was marginally increased with the use of I-MEOF, although 65% of patients still required PSA to facilitate reduction. The process was generally met with satisfaction by both providers and patients, suggesting that early administration of analgesia is appreciated. Moreover, one-third of patients had reduction achieved atraumatically without need for further intervention. A larger, randomized study may identify patient characteristics which make this reduction method more likely to be successful.
Prevention of suicidal risk is the primary goal for private psychiatrists. However there are few evidence-base data to guide clinicians in the management of suicidal patients.
Objective:
To describe the epidemiological profile of psychiatric outpatients at severe risk of suicide and to compare it with patients at no suicidal risk.
Methods:
The GICIPI database totalized 7508 outpatients having at least one diagnosis on the MINI 5.0.0 life version, as of 31DEC2007. Patients with either no suicidal risk or a severe risk on the MINI were selected for analysis. Demographic, socio professional, diagnostic and psychometric parameters were compared between the two groups.
Results:
Both groups had a similar mean age (40.3 vs 41.4 years). Data showed that the patients with a severe risk of suicide were more likely to be separated (13.29% vs 5.17%), divorced (10.76% vs 5.36%) or single (43.54 vs 28.48%). The mean weight of the two groups was comparable (72.1 kg vs 70.7 kg). The sex ratio was similar in both groups (69.6% women vs 68.6% men). There were no differences in the distribution of socio professional categories. Most strikingly, although the initial MADRS scores were higher in patients at high risk of suicide (27.1 vs 23), the HAMA scores were significantly lower (5.4 vs. 15.2).
Discussion and conclusion:
These results will be compared to the literature, and a profile of the patient at high risk of suicide, as seen in everyday private practice, will be described, hence helping to improve the management of these suicidal outpatients.
Whereas depression as a risk factor for the incidence of activity limitations in the elderly has been confirmed, little attention has been paid to anxiety, despite its high prevalence, with or without comorbid depression.
Method:
In a community-dwelling cohort of 1581 participants aged 65 years and over, the association between trait anxiety symptoms (Spielberger State-Trait Anxiety Inventory, third highest tercile) and current DSM-IV anxiety disorder (GAD, PTSD, OCD, panic disorder, agoraphobia or social phobia) at baseline and 7-year incident activity limitations was determined using mixed logistic regression models. Repeated measures of activity limitations included by increased severity level: social restriction (neighbourhood and house confined), mobility (Rosow and Breslau scale) and limitations in instrumental activities of daily living (IADL).
Results:
Of the sample, 42% were male and 14.2% had an anxiety disorder at baseline. Adjusting for socio-demographic and health variables, past and present depression and anxiolytic drugs, trait anxiety symptomatology was associated with increased incidence of social restriction (OR (95% CI): 2.46 (1.45–4.16), p = 0.0008) and current anxiety disorder with an increased risk of incident IADL limitation (OR (95% CI): 1.86 (1.01–3.41), p = 0.046). Associations remained significant in participants free of depressive symptoms at baseline (OR (95% CI): 2.92 (1.41–6.05), p = 0.004; OR (95% CI): 3.21 (1.31–7.89), p = 0.011, respectively).
Conclusion:
Despite high comorbidity between depressive and anxiety symptoms, both trait symptomatology and anxiety disorder are independently associated with increased incident dependency with a gradient of severity: trait anxiety symptoms associated with incident social restriction and anxiety disorder with incidence of IADL limitations.
Although comorbidity increases the health care and community support needs for patients, and the burden for the health care system, there are few population-based studies on comorbidity in patients with stroke. This study aims to evaluate the occurrence of important comorbidities among stroke patients in the Canadian population.
Methods:
Data from the population-based 2011–2012 Canadian Community Health Survey containing responses from 124,929 participants covering about 98% of the Canadian population when weighted were examined and analyzed by means of logistic regression models.
Results:
There was a statistically significant association between stroke history and multiple comorbid risk factors. Stroke prevalence increased in individuals with heart disease (odds ratio (OR): 3.80, 95% confidence interval (CI): 3.77–3.84), hypertension (OR: 1.97, 95% CI: 1.95–1.99), diabetes (OR: 1.74, 95% CI: 1.72–1.75), mood disorder (OR: 2.14, 95% CI: 2.12–2.17), and chronic obstructive pulmonary disease (COPD) (OR: 1.46, 95% CI: 1.44–1.48) compared to others without the condition. Of 2067 participants with stroke, 1680 (81.3%) had one or more comorbid conditions (heart disease, hypertension, diabetes, mood disorder, or COPD) that coexist with stroke and 48% had two or more. Comorbidity increased with age, and two-thirds of stroke patients with comorbid medical conditions were 60 years of age or older.
Conclusion:
This population-based study provides evidence of comorbidity between stroke and other conditions that include heart disease, hypertension, diabetes, mood disorder, and COPD. Canadian individuals with stroke have a high burden of comorbidity. Health care systems need to recognize and respond to the strong association of comorbidity and stroke occurrence. This key factor should be considered when allocating resources.
Breeding for resilience requires a better understanding of intra-flock variability and the related mechanisms responsible for robustness traits. Among such traits, the animals’ ability to cope with feed fluctuations by mobilizing or restoring body reserves (BR) is a key mechanism in ruminants. The objective of this work was to characterize individual variability in BR dynamics in productive Romane ewes reared in extensive conditions. The BR dynamics profiles were characterized by combining individual longitudinal measurements of BW and body condition scores (BCS) over several production cycles. Historical data, including up to 2628 records per trait distributed in 1146 ewes, underwent cluster analysis. Two to four trajectories were observed for BW depending on the cycle, while three trajectories were found for BCS, whatever the cycle. Most trajectories suggested that BR dynamics were similar but the level of BR may differ between ewes. Nevertheless, some trajectories suggested that both BR dynamics and levels were different for a proportion of ewes. Clustering on BW and BCS profiles adjusted for individual level trends, resulted in differences only in the level of BW or BCS, rather than differences in trajectories. Thus, the overall shape of trajectories was not changed considering or not the individual level trend across cycles. In addition to individual variability, the ewe’s age at first lambing and litter size contributed to the distribution of the ewes between the trajectories. Regarding the entire productive life, three trajectories were observed for BW and BCS changes over three productive cycles. Increase in BW at each cycle suggested that ewes kept growing up until 3 to 4 years old in our conditions. Similar alternation of BCS gains and losses across cycles suggested BR dynamics might be repeatable. Many individual trajectories remained the same throughout a ewe’s life, whatever the age at first lambing, parity or litter size. Our results demonstrate the relevance of using BW and BCS changes for characterizing the diversity of BR mobilization–accretion profiles in sheep in a long timespan perspective.
To examine the longitudinal risk of vision loss (VL) or hearing loss (HL) for experiencing suicidal ideation in older adults.
Design:
The Three-City study, examining data from three waves of follow-up (2006–2008, 2008–2010, and 2010–2012).
Setting:
Community-dwelling older French adults.
Participants:
N = 5,438 adults aged 73 years and over.
Measurements:
Suicidality was assessed by the Mini-International Neuropsychiatric Interview, Major Depressive Disorder module. Mild VL was defined as Parinaud of 3 or 4 and severe VL as Parinaud >4. Mild HL was self-reported as difficulty understanding a conversation and severe HL as inability to understand a conversation.
Results:
Severe VL was associated with an increased risk of suicidal ideation at baseline (OR = 1.59, 95% CIs = 1.06–2.38) and over five years (OR = 1.65, 95% CIs = 1.05–2.59). Mild and severe HL were associated with an increased risk of suicidal ideation, both at baseline (OR = 1.29, 95% CIs = 1.03–1.63; OR = 1.78, 95% CIs = 1.32–2.40) and over five years (OR = 1.47, 95% CIs = 1.17–1.85; OR = 1.97, 95% CIs = 1.44–2.70).
Conclusion:
Sensory losses in late life pose a risk for suicidal ideation. Suicidality requires better assessment and intervention in this population.
At the QEII Health Sciences Centre Emergency Department (ED) in Halifax, Nova Scotia, advanced care paramedics (ACPs) perform procedural sedation and analgesia (PSA) for many indications, including orthopedic procedures. We have begun using ACPs as sedationists for emergent upper gastrointestinal (UGI) endoscopy. This study compares ACP-performed ED PSA for UGI endoscopy and orthopedic procedures in terms of adverse events, airway intervention, vasopressor requirement, and PSA medication use.
Methods
A data set was built from an ED PSA quality control database matching 61 UGI endoscopy PSAs to 183 orthopedic PSAs by propensity scores calculated using age, gender, and the American Society of Anesthesiologists (ASA) classification. Outcomes assessed were hypotension (systolic BP<100 mm Hg or a 15% decrease from baseline), hypoxia (SaO2<90%), apnea (>30 sec), vomiting, arrhythmias, death, airway intervention, vasopressor requirement, and PSA medication use.
Results
UGI endoscopy patients experienced hypotension more frequently than orthopedic patients (OR=4.11, CI: 2.05-8.22) and required airway repositioning less often (OR=0.24, CI: 0.10-0.59). They received ketamine more frequently (OR=15.7, CI: 4.75-67.7) and fentanyl less often (OR=0.30, CI: 0.15-0.63) than orthopedic patients. Four endoscopy patients received phenylephrine, and one required intubation. No patient died in either group.
Conclusions
In ACP-led sedation for UGI endoscopy and orthopedic procedures, adverse events were rare with the notable exception of hypotension, which was more frequent in the endoscopy group. Only endoscopy patients required vasopressor treatment and intubation. We provide preliminary evidence that ACPs can manage ED PSA for emergent UGI endoscopy, although priorities must shift from pain control to hemodynamic optimization.
Introduction: Acute upper gastrointestinal (UGI) bleeding is a relatively common emergency resulting in death in 6 to 8% of cases. UGI endoscopy is the intervention of choice which requires procedural sedation and analgesia (PSA). The Halifax Infirmary emergency department (ED) performs 1000 PSAs annually, performed by advanced care paramedics (ACPs). This has been shown safe for other indications for PSA, such as orthopedic procedures. Considering that UGI endoscopy involves upper airway manipulation, and patients are at an increased risk of massive bleeding, this procedure would be expected to be more complex and have an increased risk of adverse events (AEs). This study aims to compare PSA for UGI endoscopy performed by ACPs to that for orthopedic procedures for AEs, airway intervention and medication use. Methods: This study is a retrospective review of an ACP-performed ED PSA quality control database. A dataset was built matching 64 UGI endoscopy PSAs to 192 orthopedic PSAs by propensity scores calculated using age, gender and ASA classification. Outcomes assessed were hypotension (SBP < 100, or 15% decrease from baseline), hypoxia (SaO2 < 90), apnea (> 30sec), vomiting, arrhythmias and death in the ED. The need for airway intervention and medication use was assessed. Results: The UGI endoscopy group was 4.60 times more likely to suffer hypotension than the orthopedic group (OR=4.6, CI:2.2-9.6), and a fifth as likely to require airway repositioning (OR=0.2, CI:0.1-0.5). One endoscopy patient required endotracheal intubation. No patient died in either group. Compared to the orthopedic group, the UGI endoscopy group was one-third as likely to receive fentanyl (OR=0.3, CI:0.2-0.6). When fentanyl was administered, endoscopy patients received an average 26.7 mcg less than orthopedic patients. The endoscopy group was 15.4 times more likely to receive ketamine (OR=15.4, CI:4.7-66.5), and received 34.4 mg less on average. Four endoscopy patients received phenylephrine compared to none in the orthopedic group. There were no other differences. Conclusion: ED PSA for UGI endoscopy appears to differ significantly from that performed for orthopedic procedures. It was associated with more frequent hypotension and increased use of ketamine as a sedative. Patients undergoing UGI endoscopy were less likely to receive fentanyl and require airway repositioning. Only patients in the endoscopy group required intubation or a vasopressor agent.
In elderly general population sub-syndromal clinically significant levels of depressive symptoms are highly prevalent and associated with high co-morbidity and increased mortality risk. However changes in depressive symptoms over time and etiologic factors have been difficult to characterise notably due to methodological shortcomings. Our objective was to differentiate trajectories of depressive symptoms over 10 years in community-dwelling elderly men and women using statistical modelling methods which take into account intra-subject correlation and individual differences as well as to examine current and life-time risk factors associated with different trajectories.
Methods.
Participants aged 65 and over were administered standardised questionnaires and underwent clinical examinations at baseline and after 2, 4, 7 and 10 years. Trajectories over time of the Center for Epidemiologic Studies Depression scores were modelled in 517 men and 736 women separately with latent class mixed models which include both a linear mixed model to describe latent classes of trajectories and a multinomial logistic model to characterise the latent trajectories according to baseline covariates (socio-demographic, lifestyle, clinical, genetic characteristics and stressful life events).
Results.
In both genders two different profiles of symptom changes were observed over the 10-year follow-up. For 9.1% of men and 25% of women a high depressive symptom trajectory was found with a trend toward worsening in men. The majority of the remaining men and women showed decreasing symptomatology over time, falling from clinically significant to very low levels of depressive symptoms. In large multivariate class membership models, mobility limitations [odds ratio (OR) = 4.5, 95% confidence interval (CI) 1.6–12.9 and OR = 4.9, 95% CI 2.3–10.7, in men and women respectively], ischemic pathologies (OR = 2.9, 95% CI 1.0–8.3 and OR = 3.1, 95% CI 1.0–9.9), and recent stressful events (OR = 4.5, 95% CI 1.1–18.5, OR = 3.2, 95% CI 1.6–6.2) were associated with a poor symptom course in both gender as well as diabetes in men (OR = 3.5, 95% CI 1.1–10.9) and childhood traumatic experiences in women (OR = 3.1, 95% CI 1.6–5.8).
Conclusions.
This prospective study was able to differentiate patterns of chronic and remitting depressive symptoms in elderly people with distinct symptom courses and risk factors for men and women. These findings may inform prevention programmes designed to reduce the chronic course of depressive symptomatology.
This paper presents the results of the Sangro Valley Project's deployment of a paperless recording system in a mixed environment of excavation and survey. It also discusses some advances made in archaeological photography. Finally, it presents preliminary results from on-going experiments with automatically generating Harris Matrices from a FileMaker Pro database and with using iPads and iPhones as GPS units for survey.
Keywords:
Recording, iPad, Paperless, Photography, Database
Introduction
The Sangro Valley Project (hereafter abbreviated SVP) was founded in 1994 and is now managed by Oberlin College in collaboration with the Soprintendenza per i Beni Archeologici dell’Abruzzo and the University of Oxford. The project operates a summer field school in Italy for Oberlin and other students; it employs a multi-disciplinary team of specialists from Canada, Italy, the United Kingdom, and the United States. The project's goal is to characterize and investigate the nature, pattern and dynamics of human habitation and land use in the longue durée within the context of a Mediterranean river valley system—the Sangro River valley of the Abruzzo region of Italy, the territory of the ancient Samnites (http://www.sangro.org).
Over its first sixteen years the SVP employed various formats to record, store, manage, and analyse its data, with recording methods based on the Museum of London Archaeological Service's site manual (Museum of London 1994). The opening of a new site in 2011 provided an opportunily to rethink the project's data systems. The Pompeii Archaeological Research Project: Porta Stabia, directed by Professor Steven Ellis of the University of Cincinnati, pioneered the use of Apple's iPad in 2010 for paperless recording of basic excavation data as well as for drawing and other functions (Wallrodt and Ellis 2011; Porta Stabia 2011). Building upon their success, the SVP developed an integrated paperless recording system in FileMaker on both laptop computers and iPads. The paperless system pushes digitization of data into the field—this replaces traditional recording using paper forms, followed by subsequent transcription into computer systems, with direct data entry into the digital database (an unlocked public version of this database has been made available at www.paperlessarchaeology.com to assist others in developing similar systems).
Recent progress in the seismic interpretation of field β Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. We present an observational asteroseismic study based on the discovery of numerous multi-periodic and mono-periodic B-type stars in the open cluster NGC 884 (χ Persei). Our study illustrates the current status of ensemble asteroseismology of this young open cluster.
This paper describes the development and testing of a GIS predictive model as part of the Sangro Valley Project's 2010 survey of agricultural terracing on Monte Pallano in Abruzzo, Italy. The survey was designed to assess the spatial distribution of terracing and to examine major patterns of terrace form, construction style, and preservation. Using the locations of previously recorded terraces, the survey modelled optimal areas for terracing based on cultural and environmental factors. New terrace data collected by the survey was used to refine the model. The resultant model indicated that the key factors determining terrace placement were different than originally theorized. This study will be continued in the 2011 field season with extended survey and soil sampling of selected terraces. Delineating the history and extent of agricultural terracing on Monte Pallano is essential for understanding the long-term dynamics of settlement and land use in this region.
In 2010, the Sangro Valley Project began a survey of abandoned agricultural terraces on Monte Pallano, a limestone ridge dominating the middle Sangro River valley in the Abruzzo region of Italy (Fig. 1). The Sangro Valley Project is devoted to investigating and characterizing the long-term patterns and dynamics of human settlement and land use in the context of a Mediterranean river valley system (http:// www.sangro.org/). Its research over the past 16 years has provided evidence – through surface surveys and excavations of domestic sites on and around Monte Pallano – for the area's habitation in the Iron Age through the Roman periods (7th century BC – 3rd century AD) (Fig. 2). Ancient and modern settlements in the vicinity of Pallano tend to cluster at 500 to 700m in elevation, and important ancient public and ritual sites have been discovered on the summit of the ridge. The 2010 Terrace Survey was designed to provide additional contextual information for long-term land use in the area by assessing the spatial distribution of agricultural terraces on the unsurveyed slopes of Monte Pallano between 700 and 1000m in elevation, between the ring of modern settlements and the archaeological sites on the summit.
As arginine plays a key role in the regulation of liver ureagenesis, we hypothesised that a modulation of enzymes involved in arginine metabolism within the intestine contributes to the regulation of N homeostasis according to protein supply. Our aim was to study the influence of variations in protein or amino acid (AA) supply on intestinal arginase, glutaminase, ornithine aminotransferase (OAT), argininosuccinate lyase and argininosuccinate synthetase. We evaluated in vivo in rats the responses of these enzymes to short-term (ST, 16 h) and long-term (LT, 15 d) variations in dietary protein (10, 17 or 25 % protein diet). In addition, in order to test whether these responses could involve a direct action of AA on the gene expression and activity of these enzymes, Caco-2/TC7 cells were cultured for 3 d with increasing AA concentrations. In vivo, in the ST, both high- and low-protein diets increased arginase activity in the intestinal mucosa (ST25 %: 46 (sem 2) μmol/g per min and ST10 %: 46 (sem 2) μmol/g per min v. ST17 %: 36 (sem 3) μmol/g per min, P < 0·05). In the LT, OAT expression was increased in the LT10 % group (+277 %, P < 0·05) compared with the LT17 % group. Caco-2/TC7 cells showed inverse relationships between AA supply and arginase (P = 0·058) and OAT (P = 0·035) expressions. The present study demonstrates the regulation of intestinal arginase and OAT expressions in response to protein supply. Our in vitro experiments further indicate a direct AA-induced regulation of the mRNA abundance of these enzymes. In situations of limited protein supply, this regulation would increase intestinal arginine catabolism and, possibly via a decrease in arginine portal release, decrease hepatic AA oxidation, thus promoting N sparing.
We show how a quantitative context may be established for what is essentially qualitative in nature by topologically embedding a lexicon (here, WordNet) in a complete metric space. This novel transformation establishes a natural connection between the order relation in the lexicon (e.g., hyponymy) and the notion of distance in the metric space, giving rise to effective word-level and document-level lexical semantic distance measures. We provide a formal account of the topological transformation and demonstrate the value of our metrics on several experiments involving information retrieval and document clustering tasks.
Ultrathin single quantum wells of crystalline silicon (c-Si) confined by SiO2 have been prepared by chemical and thermal processing of silicon-on-insulator wafers. The photoluminescence (PL) produced by these nanometer-thick single wells contains two bands: one exhibits a peak energy of ∼1.8 eV, while the second increases rapidly in peak energy with decreasing c-Si layer thickness. Comparison with theories based on self-consistent first-principles calculations shows that the increase in PL peak energy of the second band is consistent with that predicted for the c-Si energy gap of such wells. It also agrees with the measured band gap variation. The ∼1.8 eV PL band is attributed to the recombination of electron-hole pairs confined at the c-Si/SiO2 interface.
The observation of intense luminescence in Si/SiO2 superlattices (SLs) has lead to new theoretical research on silicon-based materials. We have performed first-principles calculations using three Si/SiO2 SL models in order to examine the role of interfaces on the electronic structure and optical properties. The first two models are derived directly from crystalline structures and have simple interfaces. These models have been studied using the full-potential, linearized-augmented-plane-wave method, in the local-density-approximation (LDA). The optical absorption within the interband transition theory (excluding excitonic effects) have been deduced. The Si(001)-SiO2 interface structure is shown to affect the optical behaviour. Following these observations, we have considered a more realistic, fully-relaxed model. The projector-augmented-wave method under the LDA is used to perform the structural relaxation as well as band structure and optical calculations. The role of confinement on the energy gap is studied by inserting additional silicon slabs into the supercell. Direct energy gaps are observed and the energy gap is found to decrease with increasing silicon slab thickness, as observed experimentally. The role of the interface has been considered in more details by studying the contribution to the energy gap of Si atoms having different oxidation patterns; partially oxidized Si atoms at the interface, as well as Si atoms inside the Si layer, are shown to contribute to the transitions at the energy gap.