Criticality of metals and metalloids.

Imbalances between metal supply and demand, real or anticipated, have inspired the concept of metal criticality. We here characterize the criticality of 62 metals and metalloids in a 3D "criticality space" consisting of supply risk, environmental implications, and vulnerability to supply restriction. Contributing factors that lead to extreme values include high geopolitical concentration of primary production, lack of available suitable substitutes, and political instability. The results show that the limitations for many metals important in emerging electronics (e.g., gallium and selenium) are largely those related to supply risk; those of platinum group metals, gold, and mercury, to environmental implications; and steel alloying elements (e.g., chromium and niobium) as well as elements used in high-temperature alloys (e.g., tungsten and molybdenum), to vulnerability to supply restriction. The metals of most concern tend to be those available largely or entirely as byproducts, used in small quantities for highly specialized applications, and possessing no effective substitutes.

On the materials basis of modern society.

It is indisputable that modern life is enabled by the use of materials in its technologies. Those technologies do many things very well, largely because each material is used for purposes to which it is exquisitely fitted. The result over time has been a steady increase in product performance. We show that this materials complexity has markedly increased in the past half-century and that elemental life cycle analyses characterize rates of recycling and loss. A further concern is that of possible scarcity of some of the elements as their use increases. Should materials availability constraints occur, the use of substitute materials comes to mind. We studied substitution potential by generating a comprehensive summary of potential substitutes for 62 different metals in all their major uses and of the performance of the substitutes in those applications. As we show herein, for a dozen different metals, the potential substitutes for their major uses are either inadequate or appear not to exist at all. Further, for not 1 of the 62 metals are exemplary substitutes available for all major uses. This situation largely decouples materials substitution from price, thereby forcing material design changes to be primarily transformative rather than incremental. As wealth and population increase worldwide in the next few decades, scientists will be increasingly challenged to maintain and improve product utility by designing new and better materials, but doing so under potential constraints in resource availability.

Metal Dissipation and Inefficient Recycling Intensify Climate Forcing.

In the metals industry, recycling is commonly included among the most viable options for climate change mitigation, because using secondary (recycled) instead of primary sources in metal production carries both the potential for significant energy savings and for greenhouse gas emissions reduction. Secondary metal production is, however, limited by the relative quantity of scrap available at end-of-life for two reasons: long product lifespans during use delay the availability of the material for reuse and recycling; and end-of-life recycling rates are low, a result of inefficient collection, separation, and processing. For a few metals, additional losses exist in the form of in-use dissipation. The sum of these lost material flows forms the theoretical maximum potential for future efficiency improvements. Based on a dynamic material flow analysis, we have evaluated these factors from an energy perspective for 50 metals and calculated the corresponding greenhouse gas emissions associated with the supply of lost material from primary sources that would otherwise be used to satisfy demand. A use-by-use examination demonstrates the potential emission gains associated with major application sectors. The results show that minimizing in-use dissipation and constraints to metal recycling have the potential to reduce greenhouse gas emissions from the metal industry by about 13-23%, corresponding to 1% of global anthropogenic greenhouse gas emissions.

Lost by Design.

In some common uses metals are lost by intent-copper in brake pads, zinc in tires, and germanium in retained catalyst applications being examples. In other common uses, metals are incorporated into products in ways for which no viable recycling approaches exist, examples include selenium in colored glass and vanadium in pigments. To determine quantitatively the scope of these "losses by design", we have assessed the major uses of 56 metals and metalloids, assigning each use to one of three categories: in-use dissipation, currently unrecyclable when discarded, or potentially recyclable when discarded. In-use dissipation affects fewer than a dozen elements (including mercury and arsenic), but the spectrum of elements dissipated increases rapidly if applications from which they are currently unrecyclable are considered. In many cases the resulting dissipation rates are higher than 50%. Among others, specialty metals (e.g., gallium, indium, and thallium) and some heavy rare earth elements are representative of modern technology, and their loss provides a measure of the degree of unsustainability in the contemporary use of materials and products. Even where uses are currently compatible with recycling technologies and approaches, end of life recycling rates are in most cases well below those that are potentially achievable. The outcomes of this research provide guidance in identifying product design approaches for reducing material losses so as to increase element recovery at end-of-life.

Criticality of iron and its principal alloying elements.

Because modern technology depends on reliable supplies of a wide variety of materials and because of increasing concern about those supplies, a comprehensive methodology was created to quantify the degree of criticality of the metals of the periodic table. In this paper, we apply this methodology to iron and several of its main alloying elements (i.e., vanadium, chromium, manganese, and niobium). These elements represent the basic metals of any industrial society and are vital for national security and economic well-being. Assessments relating to the dimensions of criticality - supply risk, vulnerability to supply restriction, and environmental implications - for 2008 are made on the global level and for the United States. Evaluations of each of the multiple indicators are presented, with aggregate results plotted in "criticality space", together with Monte Carlo simulation-derived "uncertainty cloud" estimates. Iron has the lowest supply risk, primarily because of its widespread geological occurrence. Vanadium displays the highest cradle-to-gate environmental implications, followed by niobium, chromium, manganese, and iron. Chromium and manganese, both essential in steel making, display the highest vulnerability to supply restriction, largely because substitution or substitution at equal performance is not possible for all end-uses. From a comprehensive perspective, we regard the overall criticality as low for iron and modest for the alloying elements we evaluated.

By-product metals are technologically essential but have problematic supply.

The growth in technological innovation that has occurred over the past decades has, in part, been possible because an increasing number of metals of the periodic table are used to perform specialized functions. However, there have been increasing concerns regarding the reliability of supply of some of these metals. A main contributor to these concerns is the fact that many of these metals are recovered only as by-products from a limited number of geopolitically concentrated ore deposits, rendering their supplies unable to respond to rapid changes in demand. Companionality is the degree to which a metal is obtained largely or entirely as a by-product of one or more host metals from geologic ores. The dependence of companion metal availability on the production of the host metals introduces a new facet of supply risk to modern technology. We evaluated companionality for 62 different metals and metalloids, and show that 61% (38 of 62) have companionality greater than 50%. Eighteen of the 38-including such technologically essential elements as germanium, terbium, and dysprosium-are further characterized as having geopolitically concentrated production and extremely low rates of end-of-life recycling. It is this subset of companion metals-vital in current technologies such as electronics, solar energy, medical imaging, energy-efficient lighting, and other state-of-the-art products-that may be at the greatest risk of supply constraints in the coming decades.

The significance of anti-HAV in different population sectors in Lebanon: a comparative seroepidemiologic study.

A comparative seroepidemiologic survey was performed on the prevalence of antibody to HAV (anti-HAV) in 772 subjects in Lebanon. The results show that 97.7% of the adult Lebanese carry anti-HAV in their sera irrespective of geographic or socioeconomic factors, as compared to 38.8% of the adult foreign population. In the paediatric group, the highest prevalence of anti-HAV was encountered at the age of 1-120 days indicating placental transfer of maternal anti-HAV. In the 1-5 year age group there is a sharp drop of anti-HAV to 40%. The anti-HAV of this age group indicates a response to actual infection with HAV. At 12 years the prevalence of anti-HAV is 85%, approaching that of adults. This survey indicates that Lebanon is an endemic area for HAV infection. The age of onset of this infection may be as early as five months, is commonest in the 1-6 year age group and becomes rare again after the age of 12. Finally, fractionation of immunoglobulins of test sera demonstrated that all subjects had their anti-HAV activity in the IgG class, denoting either maternal transfer or old infection and acquired immunity.

Seroimmunity to measles and mumps among medical students and nurses in a teaching hospital in Lebanon.

Two hundred thirty-three newly enrolled medical and nursing students at the American University of Beirut, Lebanon, were tested for antibodies to measles and mumps. Antibodies to measles were detected in 95% of the sample, and antibodies to mumps in 84% of the sample. Susceptible individuals were appropriately immunized.

Management of urinary tract infections.

Urinary tract infections (UTIs) are commonly encountered in medical practice and range from asymptomatic bacteruria to acute pyelonephritis. Enterobacteriaceae with E. coli being the most prevalent, are responsible for most commonly acquired uncomplicated UTIs and usually respond promptly to oral antibiotics. In contradistinction, more resistant pathogens cause nosocomially acquired infections which often require parenteral antibiotic therapy. Patients with acute bacterial prostatitis, usually caused by Enterobacteriaceae present with a tender prostate gland and respond promptly to antibiotic therapy. Chronic bacterial prostatitis on the other hand, is a subacute infection characterized by recurrent episodes of bacterial UTI where the patient presents with vague symptoms of pelvic pain and voiding problems. Treatment is protracted and may be frustrating. Nonbacterial prostatitis and chronic pelvic pain syndrome produce symptoms similar to those of chronic bacterial prostatitis. Treatment is not well defined due to their uncertain etiologies. Most episodes of catheter associated bacteruria are asymptomatic, where less than 5% will be complicated by bacteremia. The use of systemic antibiotics for treatment or prevention of bacteruria is not recommended, particularly in the geriatric age group, since it helps select for resistant organisms. Prevention thus remains the best option to control it. Few patients without catheters who have asymptomatic bacteruria develop serious complications and therefore routine antimicrobial therapy is not justified with only two exceptions : before urologic surgery and during pregnancy.

Gonorrhea in the male: some aspects of treatment in Lebanon.

One hundred male patients with acute gonococcal urethritis were treated with various antibiotic and chemotherapeutic regimens. Pivampicillin, 1400 mg orally in two divided does at 5 hours' interval gave 100% cure in 60 patients. Gentamicin, 280 mg IM in one dose was equally efficaceous in 15 patients. Ampicillin and Trimethoprim-sulfamethoxazole gave cure rates of around 70%. While the results of the first two groups were in agreement with data published in different parts of the world, our results with the later two groups were contrary to those of other authors. The need for periodic evaluation of various antibiotic regimens in the treatment of gonorrhea is indicated.

Brief report: susceptibility of Filipino nurses to the varicella-zoster virus.

Following an outbreak of varicella, 18% of a group of 174 young female Filipino nurses ranging in age from 20 to 25 years and working at the American University of Beirut Medical Center (AUMC) were found susceptible to the varicella-zoster virus; as compared to 3% of a matched group of 133 of their Lebanese colleagues. The level of antibody was determined by the Enzyme Linked Immunosorbent Assay (ELISA). Those susceptible were assigned duties in low-risk areas to varicella-zoster in the hospital.

Roentgenographic findings in typhoid fever.

Barium meal examinations have been performed on 20 patients with proved or clinically suspected typhoid fever. There were distinct abnormalities in the terminal ileum early in the febrile stage of the disease. The abnormality was different in a single case of relapse of typhoid. The study is easily and safely performed and we feel that it is a valuable adjunct in the diagnosis of typhoid fever, particularly in those cases where a positive blood culture is not available to confirm the clinical impression. The result of the roentgenographic examination is obtainable immediately and treatment can be initiated early.

The prevalence of hepatitis B surface antigen (HBsAg) among students and blood donors at the American University of Beirut (AUB).

HBsAg testing by CEP was performed on 2359 students and 6153 blood donors at the American University of Beirut. No significant difference existed in the prevalanece rates among the various socioeconmic groups of the Arab Asians tested. There was, however, a definite difference among the various geographic groups. The findings suggest that socioecomic factors do not satisfactorily explain the differences in the prevalence rates among various nationals.

Moxalactam in the treatment of typhoid fever.

Moxalactam therapy was evaluated in 25 patients with typhoid fever. A satisfactory initial response was observed in all cases. Treatment for 3 days resulted in a much higher relapse rate (three of five patients) than did treatment for 5 days (one of nine patients). None of the 11 patients treated for 10 to 11 days relapsed. Moxalactam is effective in typhoid fever, but its use is better restricted to special indications.

Treatment of typhoid fever with cefamandole.

Cefamandole therapy was evaluated in nine patients with typhoid fever. Six patients, including all five who received the antibiotic by continuous intravenous drip (8.0 g daily), were cured. Dosage schedules resulting in maintenance of antibiotic concentrations in serum high above the MIC seemed to correlate well with treatment success.