Search

Background The Learning Assistant (LA) model with its subsequent support and training has evidenced significant gains for undergraduate STEM learning and persistence, especially in high-stakes courses like Calculus. Yet, when a swift and unexpected transition occurs from face-to-face to online, remote learning of the LA environment, it is unknown how LAs are able to maintain their motivation (competence, autonomy, and relatedness), adapt to these new challenges, and sustain their student-centered efforts. This study used Self-Determination Theory (SDT) to model theoretical aspects of LAs’ motivations (persistence and performance) both before and after changes were made in delivery of a Calculus II course at Texas Tech University due to COVID-19 interruptions. Results Analysis of weekly written reflections, a focus group session, and a post-course questionnaire of 13 Calculus II LAs throughout Spring semester of 2020 showed that LAs’ reports of competence proportionally decreased when they transitioned online, which was followed by a moderate proportional increase in reports of autonomy (actions they took to adapt to distance instruction) and a dramatic proportional increase in reports of relatedness (to build structures for maintaining communication and building community with undergraduate students). Conclusions Relatedness emerged as the most salient factor from SDT to maintain LA self-determination due to the COVID-19 facilitated interruption to course delivery in a high-stakes undergraduate STEM course. Given that online learning continues during the pandemic and is likely to continue after, this research provides an understanding to how LAs responded to this event and the mounting importance of relatedness when LAs are working with undergraduate STEM learners. Programmatic recommendations are given for enhancing LA preparation including selecting LAs for autonomy and relatedness factors (in addition to competence), modeling mentoring for remote learners, and coaching in best practices for online instruction.

Stimulant drugs acutely increase dopamine neurotransmission in the brain, and chronic use leads to neuroadaptive changes in the mesolimbic dopamine system and morphological changes in basal ganglia structures. Little is known about the mechanisms underlying these changes but preclinical evidence suggests that iron, a coenzyme in dopamine synthesis and storage, may be a candidate mediator. Iron is present in high concentrations in the basal ganglia and stimulant drugs may interfere with iron homeostasis. We hypothesised that morphological brain changes in cocaine addiction relate to abnormal iron regulation in the brain and periphery. We determined iron concentration in the brain, using quantitative susceptibility mapping, and in the periphery, using iron markers in circulating blood, in 44 patients with cocaine addiction and 44 healthy controls. Cocaine-addicted individuals showed excess iron accumulation in the globus pallidus, which strongly correlated with duration of cocaine use, and mild iron deficiency in the periphery, which was associated with low iron levels in the red nucleus. Our findings show that iron dysregulation occurs in cocaine addiction and suggest that it arises consequent to chronic cocaine use. Putamen enlargement in these individuals was unrelated to iron concentrations, suggesting that these are co-occurring morphological changes that may respectively reflect predisposition to, and consequences of cocaine addiction. Understanding the mechanisms by which cocaine affects iron metabolism may reveal novel therapeutic targets, and determine the value of iron levels in the brain and periphery as biomarkers of vulnerability to, as well as progression and response to treatment of cocaine addiction.

Discharge of contaminated ground water may serve as a primary and on-going source of contamination to surface water. A field investigation was conducted at a Superfund site in Massachusetts, USA to define the locus of contaminant flux and support source identification for arsenic contamination in a pond abutting a closed landfill. Subsurface hydrology and ground-water chemistry were evaluated in the aquifer between the landfill and the pond during the period 2005–2009 employing a network of wells to delineate the spatial and temporal variability in subsurface conditions. These observations were compared with concurrent measures of ground-water seepage and surface water chemistry within a shallow cove that had a historical visual record of hydrous ferric oxide precipitation along with elevated arsenic concentrations in shallow sediments. Barium, presumably derived from materials disposed in the landfill, served as an indicator of leachate-impacted ground water discharging into the cove. Evaluation of the spatial distributions of seepage flux and the concentrations of barium, calcium, and ammonium-nitrogen indicated that the identified plume primarily discharged into the central portion of the cove. Comparison of the spatial distribution of chemical signatures at depth within the water column demonstrated that direct discharge of leachate-impacted ground water was the source of highest arsenic concentrations observed within the cove. These observations demonstrate that restoration of the impacted surface water body will necessitate control of leachate-impacted ground water that continues to discharge into the cove.

The speciation and bioavailability of zinc (Zn) in smelter-contaminated sediments were investigated as a function of phosphate (apatite) and organic amendment loading rate. Zinc species identified in preamendment sediment were zinc hydroxide-like phases, sphalerite, and zinc sorbed to an iron oxide via X-ray adsorption near edge structure (XANES) spectroscopy. Four months after adding the amendments to the contaminated sediment, hopeite, a Zn phosphate mineral, was identified indicating phosphate was binding and sequestering available Zn and Zn pore water concentrations were decreased at levels of 90% or more. Laboratory experiments indicate organic amendments exhibit a limited effect and may hinder sequestration of pore water Zn when mixed with apatite. The acute toxicity of the sediment Zn was evaluated with Hyalella azteca, and bioaccumulation of Zn with Lumbriculus variegates. The survivability of H. azteca increased as a function of phosphate (apatite) loading rate. In contaminated sediment without apatite, no specimens of H. azteca survived. The bioaccumulation of Zn in L. variegates also followed a trend of decreased bioaccumulation with increased phosphate loading in the contaminated sediment. The research supports an association between Zn speciation and bioavailability.

The solid-state speciation of arsenic (As), iron (Fe), and lead (Pb) was studied in the mine waste-derived fertilizer Ironite using X-ray absorption spectroscopy, Mössbauer spectroscopy, and aging studies. Arsenic was primarily associated with ferrihydrite (60-70%), with the remainder found in arsenopyrite (30-40%). Lead was observed almost exclusively as anglesite (PbSO4), with1% observed as galena (PbS). The identification of As in oxidized Fe oxides and Pb as PbSO4 is in disagreement with the dominant reduced phases previously reported and suggests As and Pb contained within the mine waste-derived product are more bioavailable than previously considered. Aging studies in solution result in Ironite granules separating into two distinct fractions, an orange oxide precipitate and a crystalline fraction with a metallic luster. The orange oxide fraction contained As adsorbed/precipitated with ferrihydrite that is released into solution when allowed to equilibrate with water. The fraction with a metallic luster contained pyrite and arsenopyrite. A complete breakdown of arsenopyrite was observed in Ironite aged for 1 month in buffered deionized water. The observations from this study indicate As and Pb exist as oxidized phases that likely develop from the beneficiation and processing of mine tailings for commercial sale. The potential release of As and Pb has important implications for water quality standards and human health. Of particular concern is the quantity of As released from mine waste-derived products due to the new As regulation applied in 2006, limiting As levels to 10 microg L(-1) in drinking water.

Microbial respiration of Fe(III) oxides has been shown to produce reduced Fe phases that are capable of transforming a variety of oxidized contaminants. Little data, however, are available on how these Fe phases evolve over time and how this evolution may affect their ability to reduce contaminants. Here,the evolution and reactivity of biologically reduced ferrihydrite were monitored over a period of 14 months. Solids were collected from a culture of Geobacter metallireducens (GS-15) thatwas incubated with ferrihydrite (as the electron acceptor) for 0, 7, 10, 20, 75, and 400 days. Mineralogical composition and surface area of the biologically reduced solids were characterized using Mössbauer spectroscopy, X-ray diffraction, and BET with N2 adsorption. By day 10, ferrihydrite began to transform, and a nanoparticle magnetite/maghemite phase, as well as two ferrous phases, was observed. One of the ferrous phases was identified as siderite, whereas the other could not be positively identified. Likely candidates, however, include Fe(OH)2(s) or an adsorbed Fe(II) species. Over the next few months, ferrihydrite was completely reduced and evolved into a mixture containing about 70% magnetite/maghemite, 19% siderite, and 11% of the second Fe(II) phase. The effect of incubation time on the reactivity of the biologically reduced solids was evaluated by measuring the kinetics of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) transformation. The only products observed were the three reduced nitroso products. Rate coefficients (k) for RDX transformation were dramatically influenced by incubation time with half-lives of about 1 month observed in the presence of solids incubated for 10 and 20 days, 3 months with solids incubated for 75 days, and negligible removal with solids incubated for 400 days. The loss of reactivity was not directly correlated to any one mineralogical variable but may be due to particle size or surface chemistry changes in the reactive Fe phase or to cell die-off and the accumulation of cell lysis products after consumption of the electron acceptor. The dramatic effect of incubation time on the rate of RDX removal highlights a potential limitation of studying complex systems, as we have here, in batch reactors and suggests that incubation time is an important variable to consider when measuring and comparing rates of contaminant reduction.

Perchlorate was reduced by a mixed bacterial culture over a pH range of 7.0-8.9. Similar rates of perchlorate reduction were observed between pH 7.0 and 8.5, whereas significantly slower reduction occurred at pH 8.9. Addition of iron metal, Fe(0), to the mixed bacterial culture resulted in slower rates of perchlorate reduction. Negligible perchlorate reduction was observed under abiotic conditions with Fe(0) alone in a reduced anaerobic medium. The inhibition of perchlorate reduction observed in the presence of Fe(0) is in contrast to previous studies that have shown faster rates of contaminant reduction when bacteria and Fe(0) were combined compared to bacteria alone. The addition of Fe(0) resulted in a rise in pH, as well as precipitation of Fe minerals that appeared to encapsulate the bacterial cells. In experiments where pH was kept constant, the addition of Fe(0) still resulted in slower rates of perchlorate reduction suggesting that encapsulation of bacteria by Fe precipitates contributed to the inhibition of the bacterial activity independent of the effect of pH on bacteria. These results provide the first evidence linking accumulation of iron precipitates at the cell surface to inhibition of environmental contaminant degradation. Fe(0) was not a suitable amendment to stimulate perchlorate-degrading bacteria and the bacterial inhibition caused by precipitation of reduced Fe species may be important in other combined anaerobic bacterial-Fe(0) systems. Furthermore, the inhibition of bacterial activity by iron precipitation may have significant implications for the design of in situ bioremediation technologies for treatment of perchlorate plumes.

Using the isotope specificity of 57Fe Mössbauer spectroscopy, we report spectroscopic observations of Fe(II) reacted with oxide surfaces under conditions typical of natural environments (i.e., wet, anoxic, circumneutral pH, and about 1% Fe(II)). Mössbauer spectra of Fe(II) adsorbed to rutile (TiO2) and aluminum oxide (Al2O3) show only Fe(II) species, whereas spectra of Fe(II) reacted with goethite (alpha-FeOOH), hematite (alpha-Fe2O3), and ferrihydrite (Fe5HO8) demonstrate electron transfer between the adsorbed Fe(II) and the underlying iron(III) oxide. Electron-transfer induces growth of an Fe(III) layer on the oxide surface that is similar to the bulk oxide. The resulting oxide is capable of reducing nitrobenzene (as expected based on previous studies), but interestingly, the oxide is only reactive when aqueous Fe(II) is present. This finding suggests a novel pathway for the biogeochemical cycling of Fe and also raises important questions regarding the mechanism of contaminant reduction by Fe(II) in the presence of oxide surfaces.

The ability to recognize facial expressions of emotion in others is a cornerstone of human interaction. Selective impairments in the recognition of facial expressions of fear have frequently been reported in chronic cocaine users, but the nature of these impairments remains poorly understood. We used the multivariate method of partial least squares and structural magnetic resonance imaging to identify gray matter brain networks that underlie facial affect processing in both cocaine-dependent (n = 29) and healthy male volunteers (n = 29). We hypothesized that disruptions in neuroendocrine function in cocaine-dependent individuals would explain their impairments in fear recognition by modulating the relationship with the underlying gray matter networks. We found that cocaine-dependent individuals not only exhibited significant impairments in the recognition of fear, but also for facial expressions of anger. Although recognition accuracy of threatening expressions co-varied in all participants with distinctive gray matter networks implicated in fear and anger processing, in cocaine users it was less well predicted by these networks than in controls. The weaker brain-behavior relationships for threat processing were also mediated by distinctly different factors. Fear recognition impairments were influenced by variations in intelligence levels, whereas anger recognition impairments were associated with comorbid opiate dependence and related reduction in testosterone levels. We also observed an inverse relationship between testosterone levels and the duration of crack and opiate use. Our data provide novel insight into the neurobiological basis of abnormal threat processing in cocaine dependence, which may shed light on new opportunities facilitating the psychosocial integration of these patients.

The kinetics of Cr(VI) reduction to Cr(III) by carbonate green rust were studied for a range of reactant concentrations and pH values. Carbonate green rust, [FeII4FeIII2(OH)12][4H2O x CO3], was synthesized by induced hydrolysis (i.e., coprecipitation) of an Fe(ll)/Fe(III) solution held at a constant pH of 8. An average specific surface area of 47 +/- 7 m2 g(-1) was measured for five separate batches of freeze-dried green rust precipitate. Heterogeneous reduction by Fe(II) associated with the carbonate green rust appears to be the dominant pathway controlling Cr(VI) loss from solution. The apparent stoichiometry of the reaction between ferrous iron associated with green rust ([Fe(II)GR]) and Cr(VI) was slightly higherthan the expected 3:1 ratio, possibly due to the presence of other oxidants, such as oxygen, protons, or interlayer carbonate ions. The rate of Cr(VI) reduction was proportional to the green rust surface area concentration, and psuedo-first-order rate coefficients (kobs) ranging from 1.2 x 10(-3) to 11.2 x 10(-3) s(-1) were determined. The effect of pH was small with a 5-fold decrease in rate with increasing pH (from 5.0 to 9.0). At low Cr(VI) concentrations (200 microM), the rate of reaction was first order with respect to Cr(VI) concentration, whereas, at high Cr(VI) concentrations, rates appearto deviate from first-order kinetics and approach a constant value. Estimated amounts of surface Fe(II) and total Fe(II) suggest that the deviation from first-order kinetics observed at higher Cr(VI) concentrations and the 50-fold decrease in rate observed upon three sequential exposures to Cr(VI) is due to exhaustion of available Fe(II).

The accuracy and performance of the revised MicroScan Rapid Gram-Negative Identification Type 3 Panel (Dade MicroScan Inc., West Sacramento, Calif.) were examined in a multicenter evaluation. The revised panel database includes data for 119 taxa covering a total of 150 species, with data for 12 new species added. Testing was performed in three phases: the efficacy, challenge, and reproducibility testing phases. A total of 405 fresh and stock gram-negative isolates comprising 54 species were tested in the efficacy phase; 96.8% of these species were identified correctly in comparison to the identification obtained either with the API 20E system (bioMérieux Vitek, Hazelwood, Mo.) or by the conventional tube method. The number of correctly identified isolates in the challenge phase, including new species added to the database, was 221 of 247, or 89.5%, in comparison to the number correctly identified by the conventional tube method. A total of 465 isolates were examined for intra- and interlaboratory identification reproducibility and gave an agreement of 464 of 465, or 99.8%. The overall reproducibility of each individual identification test or substrate was 14,373 of 14,384, or 99.9%. The new Rapid Gram-Negative Identification Type 3 Panel gave accurate and highly reproducible results in this multiple-laboratory evaluation.

The heterogeneity of the initial insult and subsequent pathophysiology has made both the study of human head injury and design of randomised controlled trials exceptionally difficult. The combination of multimodality bedside monitoring and functional brain imaging positron emission tomography (PET) and magnetic resonance (MR), incorporated within a Neurosciences Critical Care Unit, provides the resource required to study critically ill patients after brain injury from initial ictus through recovery from coma and rehabilitation to final outcome. Methods to define cerebral ischemia in the context of altered cerebral oxidative metabolism have been developed, traditional therapies for intracranial hypertension re-evaluated and bedside monitors cross-validated. New modelling and analytical approaches have been developed.

Objective: Evaluate changes in perioperative outcomes over an 82-month period in patients undergoing laparoscopic cholecystectomy by a single attending surgeon in an academic hospital. Methods: A retrospective review of 1025 consecutive patients undergoing laparoscopic cholecystectomy from September 1992 to February 1997 was compared to the initial 600 patients from May 1990 to August 1992. Statistical analysis included Chi square with Yates correction and Fischer's exact test. Results: Over the 82-month period there were no significant differences in the overall conversion rate to open cholecystectomy (p=0.26), intraoperative complications (p = 0.81), postoperative complications (p = 0.054) or mortality rates (p=0.66). There were 3 (0.5%) bile duct injuries in the initial 600 patients and only 1 (0.1%) in the group of 1025 patients (p=0.065). There was an increase (p

The prostate gland has attracted a remarkable increase in interest in the past few years. The two most common diseases of this gland, benign prostatic hyperplasia and carcinoma of the prostate, have been brought into greater prominence by new diagnostic methods, public interest, and a wider choice of surgical and non-surgical treatments. Uncertainty about the significance of these changes has occurred because of the rapidity of change, the profusion of statements, opinions and promotions, and the relatively little guidance available from the profession. Ten urologists and two general practitioners have reviewed the relevant evidence about these two prostate diseases and the newer diagnostic methods; their conclusions are summarised here. Management options and guidance on clinical practice are also discussed. Because of a number of unresolved diagnostic and management issues, detailed requirements for practice guidelines have not been specified.

Local and sympathetic nervous system stress tests were administered prior to and following a 5-d smoking cessation program to determine the effects of short term smoking cessation upon peripheral circulation. Reactive hyperemia (RH) tests were performed on the forearm as a local dilatory stressor. Finger blood flow responses to cold pressor (CP) stresses were used to access stimulation of the sympathetic nervous system. Measures of heart rate and total forearm or finger blood flow, pulse volume and rate of blood delivery were obtained continuously during each stress test. Smoking cessation produced a significant decrease (0.01p0.05) in heart rate during both the RH and CP test sequences. Grouped mean peak forearm blood flow (Mean difference = 2.11 ml.100 ml-1.min-1; p0.05) and pulse volume (Mean difference = 0.04 ml.100 ml-1.pulse-1; p0.01) were both significantly greater following occlusion during the post-cessation RH tests than during the similar test before smoking cessation. Both finger pulse volume and rate of blood delivery were significantly greater (0.01p0.05) during the recovery portion of the post-cessation CP tests than during the same period of the pre-cessation tests. Thus, smoking cessation significantly altered both the locally mediated and central nervous system controlled responses to externally applied stressors.

The model described in this paper considers all the relevant independent cost parameters, in conjunction with the process capability of the production system, market demand, technological development and the required capital recovery factor. System deterioration is modeled as a non decreasing semi-Markov process with the state space being the deterioration level of the process capability of the production system. Whenever, there is a change of state, the decision maker has several options from which to choose; (i) the system may be left as it is, (ii) the system may be replaced by a new and identical system or its modern alternative, (iii) the system may be repaired to some better state. The model facilitates these decisions and is suitable for a variety of industrial problems.

Many hydrozoa form extensive single species colonies in the littoral zone. Though it is obvious that such colonies may arise by vegetative growth following the settlement of a solitary larva, it has not been previously established how such a larva finds an appropriate substrate, and that aggregate colonies can, in their first stages, arise as a result of gregarious behaviour of larvae at the time of attachment. Observations in the laboratory suggest that aggregated colonies can be formed by the release of larvae collectively in packets of indispersable mucus, by congregation of larvae resulting from mutually induced thigmotactic responses of larvae within a swarm; and from clustering as a consequence of the selection of attachment sites close to established individuals. There is evidence that in this latter mechanism the aggregation may be chemically induced. If gregariousness is widespread in coelenterates, the observation of Duerden (1902), that coral planulae produce clusters at settlement, is...

n/a

n/a

n/a

Free-swimming planktonic larvae of most species of sedentary marine invertebrates do not metamorphose in mid-water and settle at random, but possess considerable powers of delaying metamorphoses until a suitable substrate is encountered. Within recent years several workers have analysed the physical properties of a substrate to which larvae respond, particularly amongst those species which are restricted in their distribution in the littoral zone to the surfaces of other animals and plants. The serpulidSpirorbis borealisoccurs most abundantly onFucus serratus; experiments conducted in which surfaces treated with extracts ofF. serratuswere offered as alternatives to untreated surfaces illustrated that the larvae settle on these extract-treated surfaces in significantly greater numbers. It has been demonstrated that this response is to some chemical substance derived from the alga rather than to changes in physical properties of the surface such as increased thickness of the overlying film, or changes in the surface texture. Contact with this substance modifies the settlement behaviour from that observed amongst larvae settling on untreated surfaces. The photopositive behaviour is curtailed, and the duration of the crawling behaviour preceding settlement abbreviated. The precise mechanism by which the larvae respond to the active substance is as yet unknown, but observations have illustrated that it is dependent upon the larvae detecting the active substance as an adsorbed layer on the surface rather than a response to concentration gradients in solution. The significance of an innate ability to detect specific substrates by chemical structures characteristic of the surface in the speciation of the Spirorbinae has been discussed.

n/a

STATCALC can be used successfully by anyone with a basic understanding of the techniques of statistical analysis. Full descriptions of the main techniques in STATCALC can be found in R. B. G. Williams’ books

First check whether your data are frequencies or measurements. Frequencies always takes the form of counts and relate to a classification. They do not have any unit of measurement. For example, you might have data for the numbers of butchers, bakers and candlestick makers in a group of towns, or the numbers of students with the grades A, B, and C in an examination.

The experience of a newly formed, multidisciplinary, pelvic exenteration team is presented which consists of a gynecologic oncologist, a general surgeon and a urologist. The first 20 exenterations performed by this team are reviewed. Nine patients had no postoperative problems, and of the 11 patients who did have complications, all but two, which resulted in death, were corrected without resultant debilitation. Fourteen of the 18 patients who survived the operation are tumor-free for as long as three years postoperatively. Operative proficiency as well as operative mortality and morbidity have certainly improved quite significantly as the team has gained experience.

Material requirements planning (MRP) systems first became available in the late 1960s. Until recently, there has been a proliferation of MRP software and software suppliers of various levels of sophistication and cost, all claiming to allow managers better planning of dependent manufacture and inventory systems. The potential user faces the problem of selecting, from among the many proprietary MRP packages, a system which best matches the requirements at any preferred cost. The process of assessing and selecting software has in the main been performed in conjunction with or wholly by consultants, some of whom are less than impartial. The selection process has been further aggravated of late owing to the recurring problems of software suppliers exiting from the MRP market. This research proposes a framework for assessment of all MRP packages, a method that can be performed with limited expert knowledge required by the user. The report identifies the data requirements of these frameworks and compares MRP packages available and supported in the UK. The suggested method of comparison has been made after analysis of the results of an MRP and MRP II software circulation questionnaire that was constructed and mailed to suppliers in the UK. The research aims to identify MRP systems and MRP-driven systems operating at differing functional levels and to provide a quick and inexpensive means of selection of a cost-effective MRP package for a range of constrained budgets.

FILER, COUNTER, UNIVAR, INFER, BIVAR and POLYVAR have been compressed by tokenising the BASIC keywords and removing spaces. If you wish to modify the programs you will need to retype the complete line that you change.

Adenocarcinoma of the duodenum is an uncommon malignancy that usually presents itself with either obstructive symptoms or jaundice, depending on its location. The diagnosis should be suspected in any patient with a high small bowel obstruction, weight loss, or chronic abdominal pain. Endoscopy and barium contrast x-ray films are the preferred initial studies; enteroclysis may provide additional information. Surgical resection offers the only hope for long-term survival, which should approach 50% with resectable tumors.

The short-term albumin affinity and thrombo-resistance of a polyether polyurethane vascular graft have been improved. The method is based on the C18 alkylation of the polymer. Thrombus formation by a planimetric technique and albumin retention on wire-reinforced polyurethane tubes, both C18 alkylated and untreated, were measured in short-term (4-h) exposure at femoral arterial sites in the dog. 125I-Albumin was preadsorbed on tubes and then exposed to blood for successive 2-h periods. Albumin uptake on alkylated tubes prior to blood exposure and retention following 2 h of blood exposure were significantly greater than on controls. Following a fast desorption phase in blood, the remaining albumin was more slowly desorbed from alkylated than from control tubes. Reincubation with albumin and blood reexposure produced a similar tendency, suggesting blood conditioning does not reduce the albumin affinity-enhancing property of C18 alkylation in the short term. Blood-preconditioning experiments suggested endogenous albumin has a high affinity for the C18-alkylated surface. Scanning electron microscopic examination showed thrombus and platelet densities were higher on control than on alkylated surfaces. These results suggest in vivo albumin affinity is increased for C18-alkylated polyurethane, which may be linked to decreased thrombus formation on these surfaces.

POLYVAR performs a multiple regression analysis, selecting variables using the forward technique.

UNIVAR calculates descriptive statistics for univariate data and graphically displays the data as a histogram. Data may be entered at the keyboard or retrieved from a data file created by FILER. It is possible to select a single variable from a bivariate or multivariate file.

All the programs check that you do not make obvious mistakes. For example, when entering the data, if you type the letter I instead of the digit 1 you will get an error message and a bleep to attract your attention. Other checks such as invalid option requests, invalid transformations and selecting the printer when it is not switched on, are all captured.

The answer to this question depends upon exactly which program you are using and which options you have selected. If you intend to use the graphics options within UNIVAR or BIVAR, considerably fewer data can be analysed than if these options were not selected. Similarly, if you intend to use the transformation option within BIVAR then you can analyse fewer data than if you did not select this option. If you subsequently select an option for which the data space becomes exceeded, the program will crash with a fatal error.

When the computer is ready to accept your data you will be given an appropriate message on the screen. If the program allows you to enter your data from a disc file and you wish to do this, then merely enter the name of the file. If you are typing your data via the keyboard then just type the numbers in response to the prompts you will be given. For example, the number fifteen can be entered as 15 or 15.0, the decimal number ‘point’ nine as .9 or 0.9, and so on. Scientific or E format is also accepted, so 100000 could be entered as 1E5. You cannot enter functions (such as LOG 5) or expressions (such as 5+6/3); you must first evaluate them yourself. You must press the RETURN key after you have completed typing a number. You can use the DELETE key to correct any typing before you press RETURN.

A graphics dump routine is not included with STATCALC because it would have to be tailored to your specific printer. Many graphics dumps load at &A00 and this assumption is made in UNIVAR and BIVAR. You can easily find out where your dump loads by typing *OPT 1,2 and then *LOAD your dump routine. The first number that appears on the screen after the name of the routine is the required load address. If your graphics dump does not load at &A00 then you will need to alter line 270 in UNIVAR and line 1143 in BIVAR.

You need a BBC micro model B with at least Operating System 1.0 or 1.2, BASIC version I or II and Acorn DFS version 0.90 or DNFS. You will also require a 40 track disc drive and a television or monitor. A colour screen will enhance the display but is not essential.