Empirical Approach for Estimating Reference Material Heterogeneity and Sample Minimum Test Portion Mass for "Nuggety" Precious Metals (Au, Pd, Ir, Pt, Ru).

Quantification of precious metal content is important for studies of ore deposits, basalt petrogenesis, and precious metal geology, mineralization, mining, and processing. However, accurate determination of metal concentrations can be compromised by microheterogeneity commonly referred to as the "nugget effect", i.e., spatially significant variations in the distribution of precious metal minerals at the scale of instrumental analytical beam footprints. There are few studies focused on the spatial distribution of such minerals and its detrimental effects on quantification of the existing suite of relevant reference materials (RM). In order to assess the nugget effect in RM, pressed powder pellets of MASS-1, MASS-3, WMS-1a, WMS-1, and KPT-1 (dominantly sulfides) as well as CHR-Pt+ and CHR-Bkg (chromite-bearing) were mapped with micro-XRF. The number of verified nuggets observed was used to recalculate an effective concentration of precious metals for the analytical aliquot, allowing for an empirical estimate of a minimum mass test portion. MASS-1, MASS-3, and WMS-1a did not contain any nuggets; therefore, a convenient small test portion could be used here (<0.1 g), while CHR-Pt+ would require 0.125 g and WMS-1 would need 23 g to be representative. For CHR-Bkg and KPT-1, the minimum test portion mass would have to be ∼80 and ∼342 g, respectively. Minimum test portions masses may have to be greater still in order to provide detectable analytical signals. Procedures for counteracting the detrimental manifestations of microheterogeneity are presented. It is imperative that both RM and pristine samples are treated in exactly the same way in the laboratory, lest powders having an unknown nugget status (in effect all field samples for analysis) can not be documented to be representing a safe minimum mass basis.

An exploratory analysis of individuals with multiple episodes of different reportable diseases, Montreal, 1990-2012.

OBJECTIVES: Studies of public health reporting have only examined multiple episodes of the same communicable disease within an individual. We aimed to characterize Montreal residents with multiple reportable disease episodes from 1990 to 2012, while accounting for all types of reportable diseases. STUDY DESIGN: Retrospective cohort study. METHODS: We performed an exploratory analysis using descriptive statistics, contingency tables, and logistic regression. RESULTS: There were 157,839 individuals with at least one disease report and a total of 179,455 disease reports. The 9.8% of subjects with more than one episode accounted for 20.7% of all reported episodes. Among subjects with four or fewer episodes, 54.0% were women, while 74.3% of subjects with five or more episodes were men. Subjects with multiple episodes were more likely to be reported for sexually transmitted infections than were persons with a single episode [difference of proportions: 10.4% (95% CI: 10.0%-10.9%)] and to reside in the neighbourhood encompassing Montreal's gay village. CONCLUSIONS: Individuals with multiple communicable disease reports place a large burden on public health officials. These results may help guide investigation and prevention efforts to reduce the number of excess episodes.

Comparative evaluation of the MB/BacT and BACTEC 460 TB systems for the detection of mycobacteria from clinical specimens: clinical relevance of higher recovery rates from broth-based detection systems.

New broth-based detection systems have higher recovery rates of mycobacteria from clinical specimens than traditional cultures on solid media. The clinical significance of this higher sensitivity rate is largely unknown. We prospectively evaluated the performances of two liquid media detection systems (the MB/BacT system and the BACTEC 460 TB system) and an egg-based Lowenstein-Gruft solid medium (LG) on the recovery rates of mycobacteria from 849 clinical specimens. Mycobacteria (other then M. gordonae) were detected in 51 (6.0%) specimens. In 12/51 (23%) specimens, mycobacteria (five mycobacterium tuberculosis (MtB) and seven non-M tuberculosis complex (MOTT) were recovered only from the broth-based systems. Review of the patients' clinical charts revealed that failure of LG to recover Mtb were due to nonmycobacterial overgrowth and antibiotic treatment. The recovered MOTT were all clinically nonsignificant. Higher sensitivity of broth-based mycobacteria detection systems is largely due to their capability to recover mycobacteria from treated tuberculous patients or from partially decontaminated specimens. The high recovery rates of nonclinically significant MOTT could potentially increase inappropriate use of antibiotics.

Hepatitis A vaccination during an outbreak among gay men in Montréal, Canada, 1995-1997.

STUDY OBJECTIVE: To evaluate an intervention designed to curtail an outbreak of hepatitis A among gay men, especially the young and sexually active, by promoting their free vaccination. DESIGN: The study analysed routine passive surveillance data, carried out questionnaire and serological surveys of vaccinees, and surveys among the target population in non-clinical venues. SETTING AND INTERVENTION: 15 000 free doses of hepatitis A vaccine were made available through clinics with large gay clienteles, or at gay events, and advertised by various means, in Montréal, Canada, from August 1996 to November 1997. Simultaneous vaccination against hepatitis B (always free for gay men) was also encouraged. PARTICIPANTS: Information was obtained from persons with the disease during the epidemic period, a sample of men requesting vaccination, and five community samples of gay men. MAIN RESULTS: The outbreak involved 376 gay men and the vaccine was distributed to approximately 10 000. Vaccinees were older than cases, but had many sex partners and comprised more food handlers. Special vaccination clinics at gay events were well attended but did not reach more high risk men than regular medical venues. A self reported vaccine coverage of 49% was achieved, but 26% of vaccinees already had anti-HAV antibodies. Disease incidence declined rapidly during the campaign. CONCLUSIONS: The intervention nearly tripled self reported hepatitis A vaccine coverage but its late start precludes proving that it caused the subsequent drop in incidence. However, it also increased hepatitis B vaccination and it is believed it improved links between gay men, public health, clinicians and community groups.

[The prevention of infections in child daycare centers: potential influential factors]. / La prévention des infections dans les services de garde à l'enfance:les facteurs potentiels d'influence.

The Greater Montreal Public health departments have produced and distributed to daycare centres a manual on the prevention of infections in daycare personnel and trainees. In order to identify which factors can influence daycare management in applying the prevention measures suggested in the manual, a study was carried out based on the Precede/Proceed theoretical framework. A total of 134 (31.6%) daycare directors completed the questionnaire. Many were aware of the different recommendations to prevent infections. However, two of the recommendations were not followed by many: wearing gloves and verifying the vaccination status of their personnel, especially in private daycare centres. Participants had a positive attitude toward the various recommendations but mentioned several problems, specifically difficulty in obtaining the information about the vaccination status, lack of time and money, as well as having to deal with a poor physical organization of the work place. Among others things, the participants proposed that there be a greater involvement from schools, provincial daycare regulators, community clinics and public health departments.

Risk factors for measles and vaccine efficacy during an epidemic in Montreal.

OBJECTIVES: 1) to identify potential risk factors for measles and 2) to assess the efficacy of the measles vaccine. METHODS: Cases of measles reported from primary and secondary schools in Montreal during the 1989 epidemic were compared with classroom and sibling controls with respect to age at vaccination against measles, time since vaccination, type of vaccination, type of providers and age of the mother. RESULTS: Subjects vaccinated at 12 months had an OR of 3.9 (CI 95%: 2.1 to 7.0) of contracting measles when compared with subjects vaccinated at 15 months or later. Vaccination at age 13 or 14 months was not associated with an increased risk. Subjects vaccinated before June 1979 had an OR of 5.8 (CI 95%: 2.8 to 12.1) of developing measles compared with subjects vaccinated after June 1980. Vaccine efficacy was 96.1%. DISCUSSION: In highly vaccinated populations, vaccination at 12 months and vaccination before 1980 are probably two reasons why outbreaks still occur. The two-dose schedule could reduce the proportion of vaccinated persons who remain susceptible.

Evaluation of the effectiveness of immunization delivery methods.

Scientific evidence documenting the effectiveness of immunization delivery methods was summarized using the generic approach developed by the Community Health Practice Guidelines Working Group. The delivery methods examined were those for the adult and childhood vaccines of influenza, pneumococcal infection, hepatitis B, measles-mumps-rubella and diphtheria-pertussis-tetanus-polio. Based on a critical appraisal of 54 eligible comparative studies, the effects of different interventions were obtained and pooled effects were calculated for delivery methods oriented to the client, the provider and the system. The results indicate those interventions found to be most effective for each vaccine. This review of the scientific evidence of the effectiveness of immunization delivery methods provides a base for policy development and assists in the planning of resource allocation.

Practice survey of immunization in Canada.

A survey was undertaken in September 1991 to document current immunization practice across Canada. Information was obtained during interviews with provincial epidemiologists and key persons involved in immunization programs and recorded on standard data collection forms. Variations in practice are described in five areas: public/private health administration; legislation; monitoring system/coverage rates/surveillance; vaccine management and costs. As changes are being considered to immunization programs, a critical examination of issues such as standardization (in coding, in assessment of waste, in assessment of coverage), surveillance systems and the use of serosurveys would be beneficial.

Immunization delivery methods: practice recommendations.

Immunization has unequivocally contributed to large-scale reductions in mortality and morbidity due to infectious diseases. In general, consensus on the scheduling of immunizations has been achieved at the national or international level by immunization advisory committees. However, immunization delivery methods are varied and numerous. Although specific methods have been proposed, compared and evaluated, the available evidence has not been comprehensively summarized for informed public health action. This paper integrates evidence based on scientific documentation, a Canada-wide practice survey and expert opinion to formulate practice recommendations for immunization delivery methods and to identify areas for further research.

Severe complications associated with varicella: Province of Quebec, April 1994 to March 1996.

OBJECTIVE: To determine the frequency and severity of serious complications associated with varicella in Quebec; the frequency and severity of cases of congenital varicella; and hospital costs associated with hospitalizations for varicella. STUDY DESIGN: All hospitalizations related to varicella were identified through the use of a hospital data bank and pertinent data were collected from hospital records. SETTING: Province of Quebec with a population of 6,895,960 people. STUDY POPULATION: All cases with a principal or secondary diagnosis of varicella hospitalized in Quebec between April 1, 1994 and March 31, 1996. OUTCOME MEASURES: Types of complications and reason for hospitalization, risk of complications and calculation of associated costs were studied. RESULTS: Nine hundred nine eligible hospitalizations were identified between April 1, 1994 and March 31, 1996. In all, 583 (64.1%) hospitalizations were for the treatment of complications, 127 (14.0%) for administration of intravenous acyclovir and 199 (21.9%) for supportive care. Healthy people accounted for 644 (70.8%) hospitalizations and immunosuppressed individuals for 136 (15.0%). Among children, one-half of the principal complications were skin infections, while 13.5% and 8.4% of principal complications were pneumonia and neurological complications, respectively. Among adults, the most common complication was pneumonia, with a rate of 43.5%, followed by thrombocytopenia and skin infections, with rates of 22.2% and 14.8%, respectively. The complication rate was 29.2 cases/10,000 cases of varicella. CONCLUSIONS: Although perceived as a benign childhood disease by the general population, varicella may be accompanied by severe complications. Morbidity associated with varicella is one of the elements that must be considered when evaluating the usefulness of varicella vaccine.

[The daily public health nursing practice: the Montreal infectious diseases unit as an example]. / La pratique quotidienne des infirmières d'une direction de santé publique: l'exemple de l'unité maladies infectieuses à Montréal.

The health of urban populations depends on multiple factors, among them access to health and social services. The Montreal Public Health Department (PHD) is part of such services, where a number of nurses are working within a multidisciplinary team. It is through the description of the work accomplished by the team for infectious diseases control and prevention, and the vignettes of real life events related to the follow-up of syphilis, tuberculosis and hepatitis A cases, as well as quarantined individual exposed to SARS that the authors want to illustrate the work of the urban public health nurses. The examples are preceded by a description of the socio-demographic characteristics of the city of Montreal, that influence health problems, and therefore nurses' work.

Invasive bacterial infections following influenza: a time-series analysis in Montréal, Canada, 1996-2008.

BACKGROUND: Shared seasonal patterns, such as between influenza and some respiratory bacterial infections, can create associations between phenomena not causally related. OBJECTIVES: To estimate the association of influenza with subsequent bacterial infections after full adjustment for confounding by seasonal and long-term trends. METHODS: Time series of weekly counts of notified cases of invasive infections with Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae and Streptococcus pyogenes, in Montréal, Canada, 1996-2008, were modelled by negative binomial regression, with terms representing seasonal and long-term trends and terms for numbers of positive laboratory tests for influenza A and B. RESULTS: The associations of S. pneumoniae, H. influenzae and N. meningitidis with influenza disappeared after seasonal terms were added to the model. However, the influenza B count remained associated with the S. pyogenes counts for the same week and the following week: S. pyogenes incidence rate ratios were 1.0376 (95% CI: 1.0009-1.0757) and 1.0354 (0.9958-1.0766), respectively, for each increase of 1 in the influenza count. CONCLUSIONS: Influenza B accounts for about 8 percnt; of the incidence of invasive S. pyogenes infections, over and above any effect associated with modellable seasonal and long-term trends. This association of influenza B with S. pyogenes infections can be attributed largely to the years 1997, 2001, 2007 and 2008, when late peaks in influenza B counts were followed by peaks in S. pyogenes notifications. This finding reinforces the case for universal immunization against influenza, as partial protection against the 'flesh eating disease'.

TCF selenium preconcentration in geological materials for determination at sub-mugg(-1) with INAA (Se/TCF-INAA).

In geological samples, Se concentration ranges from 1x10(-9)gg(-1) up to 1x10(-3)gg(-1). The analytical difficulty at low concentration (<1mugg(-1)), is one of the main reasons why the geological cycle of Se is poorly known. The analytical method that consisted of preconcentration of Se with thiol cotton fiber (TCF) followed by graphite furnace atomic absorption spectrometry (GFAAS) has been modified by finishing with instrumental neutron activation analysis (INAA). The modified technique involves sample dissolution (HF-HNO(3)-H(2)O(2)) and evaporation to dryness at low temperature (55-60 degrees C) to avoid selenium volatilization. Se(VI) is converted to Se(IV) by adding 6M HCl to the dry residuum and the solution is then heated in a covered boiling bath (95-100 degrees C). The solution is diluted to obtain 0.6M HCl and then collected on TCF. The TCF is placed in a polyethylene vial for irradiation in the SLOWPOKE II reactor (Montréal) for 30s at a neutron flux of 10(15)m(-2)s(-1). The 162keV peak of (77m)Se (half-life 17.36s) is read for 20s after a decay of 7s. The amount of sample to be dissolved is controlled by two competing effects. To obtain low detection limits, a larger amount of sample should be dissolved. On the other hand, the TCF could become saturated with chalcophile elements when large sample is used. Sulfur is a good indicator of the amount of Se and chalcophile elements present. In S poor sample (<100mugg(-1)) 3.0g of sample was used and the L(D) was approximately 2ngg(-1). In S high samples (>1.5% S) 0.05g of sample was used and the L(D) was approximately 120ngg(-1). The present work also includes suggested Se concentration for eight international geological reference materials (IGRM) that compare favorably with literature values.

Image digitizing in conventional radiology.

Since early 1991 a new procedure has been tested at the Hôpital du St-Sacrement that uses a phosphorous plate instead of a standard x-ray cassette. The phosphorous plate is exposed to x-rays using standard equipment and is then read by a computer that transfers the resulting image onto either a plate or a cathode screen. This new technology lends importance to the radiology technician's role in image manipulation and determination of the ideal sensitometric curve for each x-ray examination. The technician can generate an image with adjustments in latitude and contrast, depending on the radiologist's needs and notwithstanding the technical parameter settings used during the x-rays.

[Efficacy and complications associated with vasectomies in two clinics in the Quebec region]. / Efficacité et complications associées à la vasectomie dans deux cliniques de la région de Québec.

OBJECTIVE: To compare the efficacy of, and complications associated with, vasectomies performed in two medical clinics. DESIGN: Retrospective cohort study. SETTING: A private medical clinic and a family planning clinic at a teaching hospital in the Quebec City region, where one doctor performs all surgery. PARTICIPANTS: The 1223 men who underwent a first vasectomy between January 1994 and February 1996. INTERVENTIONS: Isolations of the vas deferens through the scrotum was performed using the no-scalpel technique in both clinics. At the private clinic (n = 775), vasectomy was performed by ligature with tantalum clips. At the family planning clinic (n = 448), a combination of cauterisation of the abdominal end of the vas deferens, leaving the testicular end open, and fascial interposition with a clip was used. MAIN OUTCOME MEASURES: Rate of postoperative complications (painful granuloma; noninfectious inflammation of the vas deferens, epididymis, and testes; hematoma; infection; undiagnosed pain) and rate of recanalization (early and late). RESULTS: At the private clinic, 39 patients (5.0%) consulted for postoperative complications, compared with 55 patients (12.3%) at the family planning clinic (chi (2)1 = 21.0; P < 0.001). Of the patients who underwent semen analysis, 15 (2.8%) at the private clinic and 4 (1.2%) at the family planning clinic experienced early or late recanalization (chi (2)1 = 2.2; P < .14). CONCLUSION: The rate of consultation for postoperative complications was lower at the private clinic than at the family planning clinic, but the efficacy of the procedure appeared to be higher at the family planning clinic. The surgical techniques used at the two clinics might partially explain these differences.

Epidemiology of tuberculosis in Montreal.

OBJECTIVE: To identify the epidemiologic characteristics of tuberculosis (TB) in Montreal and the patterns of resistance to antituberculous drugs in order to improve TB control in the region. DESIGN: Descriptive analysis of surveillance data for TB cases reported in Montreal by physicians and laboratories between 1992 and 1995. SETTING: Region of Montreal, population 1,775,889. PARTICIPANTS: All cases of active TB among Montreal residents reported to the Department of Public Health between Jan. 1, 1992, and Dec. 31, 1995. OUTCOME MEASURES: Epidemiologic characteristics, proportion of cases resistant to antituberculous drugs and types of resistance. RESULTS: A total of 798 cases of TB (mean annual incidence 11.2 per 100,000) were reported in Montreal during the study period. Of these patients, 617 (77.3%) were born outside Canada. The annual incidence of TB in the foreign-born population (37.5 per 100,000) was 10 times the rate in the Canadian-born population, and the highest rate among foreign-born residents (62.8 per 100,000) occurred in those 15-29 years of age. In general, annual incidence in Montreal's foreign-born population reflected the reported incidence of TB in their regions of birth. In 8.7% of all cases, the disease was resistant to isoniazid, and the proportion of cases resistant to this drug was greater than 4% in almost all age groups, among both foreign-born and Canadian-born patients. CONCLUSIONS: TB remains a major problem in Montreal, as in other large cities. Surveillance data give opportunities to public health agencies to adapt their prevention and control strategies to local situations and can also help clinicians in their clinical decision-making.

Comparison between pentobarbital- and muscimol-induced feeding in satiated sheep.

Twenty sheep were used to study the mechanisms by which the intracerebral administration of pentobarbital and of muscimol induces feeding in ruminants. Injections of 1 mumol calcium induced a weak feeding response at 1 h postinjection compared with control values (108 vs. 63 g, p less than 0.05). Injections of 78 mumol pentobarbital and of 100 nmol muscimol elicited strong feeding responses (p less than 0.01). A preinjection of 1 mumol calcium reduced the response to pentobarbital by about 40% but did not affect the response to muscimol. Administration of 1.1 mmol sodium chloride reduced the effect to pentobarbital by about 60% but only partially decreased the effect to muscimol. Administration of picrotoxin, a GABA antagonist, slightly decreased the feeding response to pentobarbital and to muscimol. Administration of gamma-vinyl GABA, an inhibitor of the enzyme GABA transaminase, did not affect feeding behavior of sheep at any of the doses tested (0-10 mumol). Injections of gamma-vinyl GABA followed by equimolar injections of GABA failed to provoke any feeding response. The data suggest that pentobarbital and muscimol may induce feeding by acting on a similar hypothalamic receptor complex but by different mechanisms. The lack of effect of GABA itself remains unexplained.

Effects of intrahypothalamic injections of GABA, muscimol, pentobarbital, and L-glutamic acid on feed intake of satiated sheep.

Five wethers were surgically prepared with cranial implants to study the role of gabaminergic neural pathways on the hypothalamic control of feeding behaviour in ruminants. In the first experiment, the animals were injected (1 microL) with a physiological Tyrode (0.95%) solution, muscimol (0.5 and 1.0 nmol), GABA (0.5 and 1.0 nmol), and L-glutamic acid (0.5 and 1.0 nmol). Feed intake following injections of muscimol (1.0 nmol) and L-glutamic acid (0.5 and 1.0 nmol) was twice as large as that following the Tyrode solution, at 60-min postinjections. These results, however, were not statistically significant (p = 0.12-0.15). In the second experiment, the animals were injected (1 microL) with saline, muscimol (0.8 nmol), L-glutamic acid (0.8 nmol), and pentobarbital (0.26 mumol). Fifteen minutes after the injections, pentobarbital had induced a significant feeding response when compared with control values (p less than 0.01), whereas the effect of L-glutamic acid was not significant. However, 30 min after the injections, feed intake of sheep having received L-glutamic acid was higher than that obtained with the control injections (p less than 0.01). The response to pentobarbital was stronger than that to either muscimol or L-glutamic acid. Histological analyses of brain tissue indicated that injections were performed in the ventromedial hypothalamus of four sheep and in the dorsomedial hypothalamus of the other. The data indicate that L-glutamic acid stimulates feed intake by acting either as a precursor of GABA or by a direct stimulation of glutaminergic neural pathways involved in the control of feed intake.

Effects of intraventricular injections of gamma-aminobutyric acid and related substances on feeding behavior in satiated sheep.

Feed intake was measured following injections of gamma-aminobutyric acid (GABA), muscimol (a GABA agonist), and picrotoxin (a GABA antagonist) into the lateral ventricles of satiated sheep. Doses ranging from 0.20 to 3200 nmol of GABA did not affect feeding behavior at 15, 30, 60, and 120 min postinjection. A dose of 160 nmol of muscimol induced a marked increase in feeding, comparable to that provoked by an injection of 78 mumol of pentobarbital. Muscimol-induced feeding was blocked effectively by a preinjection of picrotoxin. These observations implicate that neurons sensitive to gamma-aminobutyric acid may be involved in the control of feeding behavior in ruminants.