Influence of Adhesive Incise Drape Use on Surgical Site Infection Rates in Contaminated and Dirty Abdominal Operations

BACKGROUND

Surgical Site Infection (SSI) remains the most common cause of Healthcare-Associated Infections (HCAIs). In particular, contaminated and dirty abdominal wounds are attended by a high rate of SSI which in turn is associated with a huge burden on patients, caregivers and the entire health care system.

OBJECTIVE

To compare SSI rates following the use of iodine-impregnated adhesive incise drapes (Ioban) with routine conventional drapes in contaminated and dirty abdominal surgical wounds in a Nigerian tertiary hospital.

METHODOLOGY

Consecutive, consenting adult patients who underwent laparotomy for cases classified as contaminated and dirty were prospectively enrolled in the study. Patients in the investigation arm had in addition to conventional drapes, iodine-impregnated adhesive incise drapes (Ioban) applied on the skin of the abdomen through which incisions were made, while patients in the control arm only had routine conventional drapes applied. All patients were followed up to 30 days after the operation. Surgical site infection rates were compared between the two groups.

RESULTS

Sixty-two consecutive patients were enrolled into this study, of which 55 completed the 30-day follow-up. The mean ages of patients in the two groups were 37.96 ± 19.59 years and 36.74 ± 16.93 years (p=0.81). Males were 36 (65.5%) and females were 19 (34.5%). Overall, 30 (54.5%) patients had surgical site infection (SSI) in this study. Thirteen (46.4%) patients had SSI in iodine iodine-impregnated adhesive incise drape group while 17 (63%) patients had SSI in the conventional drape group, a difference that was not statistically significant (p=0.22). The most commonly isolated organism from infected wounds was Klebsiella species.

CONCLUSION

The use of iodine-impregnated surgical incise drapes was associated with a lower, though non-statistically significant SSI rates compared to the use of conventional drapes. This marginal benefit will require a larger population study to examine its potential cost-effectiveness in our setting.

Controlling anisotropic properties by manipulating the orientation of chiral small molecules

Chiral π-conjugated molecules bring new functionality to technological applications and represent an exciting, rapidly expanding area of research. Their functional properties, such as the absorption and emission of circularly polarized light or the transport of spin-polarized electrons, are highly anisotropic. As a result, the orientation of chiral molecules critically determines the functionality and efficiency of chiral devices. Here we present a strategy to control the orientation of a small chiral molecule (2,2'-dicyano[6]helicene) by the use of organic and inorganic templating layers. Such templating layers can either force 2,2'-dicyano[6]helicene to adopt a face-on orientation and self-assemble into upright supramolecular columns oriented with their helical axis perpendicular to the substrate, or an edge-on orientation with parallel-lying supramolecular columns. Through such control, we show that low- and high-energy chiroptical responses can be independently 'turned on' or 'turned off'. The templating methodologies described here provide a simple way to engineer orientational control and, by association, anisotropic functional properties of chiral molecular systems for a range of emerging technologies.

Briquetting of subbituminous coal and torrefied biomass using bentonite as inorganic binder

The use of inorganic binder for briquetting of subbituminous coal and torrefied biomass for energy generation is scarce. The present study focuses on the physicomechanical durability and energy content of briquettes produced from subbituminous coal (SubC) and torrefied biomass (TM) using bentonite as binder. Briquettes were produced using 95% SubC and 5% TM. Bentonite was varied at 2-10% of the total SubC and TM weight. The briquettes were produced with a constant pressure (28 MPa) in a hydraulic press. The briquettes were primarily cured at room temperature and then at 300 [Formula: see text] in a tubular furnace under an inert condition for 60 min. The density and water resistance (WRI) of the briquettes were evaluated. Drop to fracture (DF), impact resistance index (IRI), cold crushing strength (CCS) and tumbling strength index (TSI+3 mm) of the briquette were obtained. The reactivity index (RI), proximate, ultimate and calorific values analyses were assessed based on different ASTM standards. Microstructural studies and elemental mapping were carried out using scanning electron microscope equipped with EDS and electron probe microanalyzer. The density increased with increment in bentonite content. The WRI decreased with increase in bentonite while the least (95.21%) was obtained at 10% binder content. The DF and IRI ranges from 100 to 150 and 2000-3000, respectively. The CCS were in the range of 19.71 to 40.23 MPa. The RI varies from 34 to 50%. Fixed carbon, carbon and calorific values were impaired as the bentonite content in the briquette increases. Oxygen and silica bridges with mechanical interlocking were observed on the micrographs of the briquettes. The briquettes produced with 2% bentonite content have better physicomechanical durability with equivalent energy content. It is recommended as feedstock for thermal and metallurgical applications.

Investigation of physicochemical characteristics of selected lignocellulose biomass

The beneficial effects of biofuels as components of the worldwide energy supply are unquantifiable because they have versatile applications. However, an adequate understanding of the chemical properties of typical biomass is an integral aspect of maximizing the energy potentials because it is susceptible to biomass behavior during the conversion process, especially anaerobic digestion. Therefore, this study investigated the physicochemical characteristics of selected lignocellulose biomass, namely; cow dung, mango pulp, and Chromolaena odorata of Nigerian origin. The raw biomasses were characterized by proximate, calorific, ultimate, compositional, and microbial (for cow dung only) analyses using ASTM standards and equipment. Raw biomass characterization showed that cow dung, mango pulp, and Chromolaena odorata leaves recorded percentages; fixed carbon, volatile matter, and ash contents in addition to calorific values in the ranges of 6.22-7.25%, 5.02-7.79%, 1.14-1.91,% and 13.77-16.16 MJ/kg, respectively. The ultimate analysis of cow dung, mango pulp and Chromolaena odorata recorded carbon (43.08, 39.98, 41.69%); hydrogen (7.87, 6.74, 9.86%); nitrogen (1.53, 1.34, 1.51%); sulphur (0.46, 0.12, 0.25%) and oxygen (47.06, 51.82, 46.69%), respectively. Compositional analysis of the biomass gave percentages in the range of 7.47-11.37 for hemicellulose, 0.22-6.33 for lignin, and 3.71-12.03 for cellulose, while the microbial analysis of cow dung gave total bacteria counts of 5.78 × 10⁸ and 3.93 × 10⁵ cfu/g on wet and dry bases, respectively, which implied that it was rich in microbial colonies, evidently from the various species found, such as Escherichia coli, Staphylococcus aureus, Bacillus cereus, Pseudomonas aureginosa, Proteus morganii, and Micrococcus spp. In this regard, the physicochemical properties of selected biomass of Nigerian origin were established to conform with those of the literature and thus can be regarded as suitable feedstock for anaerobic digestion resulting in methane-rich biogas products.

Synthesis, physico-mechanical and microstructural characterization of Al6063/SiC/PKSA hybrid reinforced composites

The utilization of agro-residues ash as complementary reinforcing materials continues to gain prominence for metal matrix composite (MMCs) development. A rarely investigated but largely available ash among these agro-residues is the palm kernel shell ash (PKSA). Thus, the present study investigates the influence of PKSA particulates hybridized with SiC on the physico-mechanical properties and microstructure of Al6063 metal composites. The composites are synthesized using the double stir-casting technique with SiC held constant at 2 wt.%, while the PKSA contents are varied from 0 to 8 wt.%. The phases present and morphology of the composites are investigated using X-ray diffractometer (XRD) and scanning electron microscopy (SEM), respectively. The density, porosity, hardness, tensile and fracture toughness tests are carried out on the hybrid composites. X-ray diffractometer revealed that for Al 6063, only Al cubic crystal system was identifiable within the matrix. However, for the reinforced composites, major phases identified are Al, Fe₃Si, SiC, MgO, and SiO₂. The SEM images show that the particulates reinforcements (SiC and PKSA) were uniformly dispersed in the matrix. The percentage porosity for the composites ranged from 2.06 to 2.39%. In addition, hardness, yield strength and ultimate tensile strength of the composites are about 10.3%, 18.5% and 10.4%, respectively better than for Al 6063. However, the percent elongation and fracture toughness are lower for the hybrid composites than for Al 6063 and SiC reinforced composite with values decreasing with increase in ash content. Hence, the MMCs produced will be applicable for light-weight engineering applications.

Properties of Alkaline-Earth-Metal Polynitrogen Ternary Materials at High Pressure

We report the formation of cubic and tetragonal BaSrN3 at 100 GPa using an ab initio structure search method. Pressure ramping to 0 GPa reveals a reaction pressure threshold of 4.92 and 7.23 GPa for the cubic and tetragonal BaSrN3, respectively. The cubic phase is stabilized by coulombic interaction between the ions. Meanwhile, tetragonal BaSrN3 is stabilized through an expansion of the d-orbital in Ba and Sr atoms that is compensated by delocalization of π-electrons in N through reduction of π overlap. Elastic properties analysis suggests that both phases are mechanically stable. The structures also have high melting points as predicted using an empirical model, and all imaginary modes vanishes at about 2000 K. These results have significant implication for the design of cleaner and environmentally friendly high energy density materials.

Optimization of heat treatment parameters of medium carbon steel quenched in different media using Taguchi method and grey relational analysis

Quenching is one of the major processes of heat treatment of medium carbon steel that aims at improving its mechanical properties. However, the effectiveness of this process is dependent on several control factors that must be maximized to obtain optimum results in terms of hardness, yield strength, ultimate tensile strength among others. This study aims at optimizing the process of improving the mechanical properties of medium carbon steel by varying some key factors like the quenchant used (A), heat treatment temperature (B), and soaking time (C). The measured responses in this study were the hardness, yield strength (YS), and ultimate tensile strength (UTS). Optimization was conducted in two stages. The first stage dealt with the mono-optimization of process parameters using Taguchi's Signal-to-Noise (S/N) ratio. A total of nine (9) experiments were performed based on standard L9 orthogonal array because each of the three control factors has three (3) levels. The second stage was multi-objective optimization using Taguchi-based grey relational analysis (GRA). The optimal conditions for hardness, YS, and UTS were obtained at A₂B₃C₃, A₃B₂C₃, and A₃B₃C₃, respectively. Using ANOVA as statistical analysis, it was observed that the soaking time was the main control factor for all three measured responses (31.95% contribution ratio for hardness, 62.46%, and 66.76% for YS and UTS, respectively), while the quenchant had the least contribution. Analysis of the Taguchi-based GRA revealed that the results obtained are in total conformance to that of the Taguchi method, with soaking time having the highest contribution ratio of 69.41%.

Nitrogen in black phosphorus structure

Group V elements in crystal structure isostructural to black phosphorus with unique puckered two-dimensional layers exhibit exciting physical and chemical phenomena. However, as the first element of group V, nitrogen has never been found in the black phosphorus structure. Here, we report the synthesis of the black phosphorus-structured nitrogen at 146 GPa and 2200 K. Metastable black phosphorus-structured nitrogen was retained after quenching it to room temperature under compression and characterized in situ during decompression to 48 GPa, using synchrotron x-ray diffraction and Raman spectroscopy. We show that the original molecular nitrogen is transformed into extended single-bonded structure through gauche and trans conformations. Raman spectroscopy shows that black phosphorus-structured nitrogen is strongly anisotropic and exhibits high Raman intensities in two A _g normal modes. Synthesis of black phosphorus-structured nitrogen provides a firm base for exploring new type of high-energy-density nitrogen and a new direction of two-dimensional nitrogen.

o-C240: a new sp3-dominated allotrope of carbon

We report a new allotrope of carbon predicted from first principles simulations. This allotrope is formed in a simulated conversion of two-dimensional polymeric C60 precursor subjected to uniaxial compression at high temperature. The structure is made up of 240 carbon atoms in an orthorhombic unit cell (termed as o-C240) having a mixed sp2/sp3 hybridization with the ratio of about 1:5. o-C240 is stable at ambient condition and exhibits superior mechanical performance including optimum Vickers hardness (45 GPa) and fracture toughness (4.10 MPa m1/3), outperforming most of widely used hard ceramics. The electronic structure reveals semiconducting ground state with an indirect band gap of 1.72 eV. The simple reaction pathway could accelerate discovery of this allotrope in laboratory, and the simultaneous occurrence of high fracture toughness, superhardness and semiconductivity is expected to find applications for this material.

The ignitability, fuel ratio and ash fusion temperatures of torrefied woody biomass

The impact of torrefaction temperature on the ignitability, fuel ratio and ash fusion temperatures of two tropical deciduous woods (Teak and Melina) were investigated in a setup of tubular furnace. The properties considered are calorific value, fuel ratio, ignitability index, ash compositions and ash fusion temperatures of the biomass. Six different temperatures (220, 240, 260, 280, 300 and 320 °C) at 60 min reaction time were considered. The results indicated that as torrefaction temperature increased, the calorific value, fuel ratio and ignitability index of the biomass also increased. The ignitability index of biomass (40–63) was better than the value (35) recommended for fuel applicable in thermal plants for power generation. The ash compositional analysis revealed that there was no variation in the quantity of SiO₂, Al₂O₃, CaO along with other minerals for the raw and torrefied biomass. This implied that the temperature up to 320 °C has no significant impact on the compositions of biomass ash during torrefaction. The ash fusion temperature test showed that the biomass ash softens at ≈ 1200 °C and finally fused at ≈ 1300 °C. The study concluded that an increase in torrefaction temperature increases the thermal properties of the torrefied biomass without affecting the compositions of biomass ash or lowering the ash fusion temperatures.

Densification of coal fines and mildly torrefied biomass into composite fuel using different organic binders

Coal processing industries generate millions of tons of fines (<3 mm) during mining operation and are often considered as wastes. These wastes have enormous potential in serving as energy and metallurgical operation feedstock. One avenue for its use is densification into briquettes or pelletizes. Various briquetting techniques have been adopted in the past few decades; however, the main issues upfront in commercializing these techniques are significant binder cost and poor mechanical integrity. Therefore, the present study concentrates on utilizing commonly available organic binder along with pretreated biomass in developing coal fine briquettes. Briquettes were produced after initial pretreatment of the raw materials under a load of 2 tons. Briquettes were cured in an inert environment and eventually characterized for its main litmus requirements (physical properties). It was observed that pitch-molasses bonded briquettes have better physical properties leading to good mechanical integrity than briquettes produced from individual binder. The proximate, ultimate and calorific value analyses of the briquettes do not deteriorate but mildly improved compared to the raw coal fines. With a density of 1.18–1.32 g/cm³, drop to fracture that is greater than 100 (times/2 m), impact resistance index well above 6000, water resistance index of 99% and cold crushing strength of 9 MPa, pitch-molasses bonded briquettes clearly surpassed recommended physical properties benchmarked for briquettes of industrial and domestic end use. The physical properties of the briquettes favorably meet requirements as feedstock for rotary kiln direct reduced iron and COREX iron-making processes as well as fuel for thermal operations.

High-temperature shape memory loss in nitinol: a first principles study

We have performed first-principles calculations to investigate the possibility of shape memory loss in a member of the binary smart alloy family - NiTi. A detailed analysis of the transition kinetics and dynamical pathway reveals the possibility of the B19' phase of NiTi losing its shape memory when subjected to high stress conditions and is heated above a critical temperature, Tc. The B19' phase is predicted to transform to P1[combining macron]-NiTi, which is also predicted to be dynamically stable and temperature-quench recoverable. It is found that the B2(B33) → B19' transition is dominated by the β shearing mode with pronounced distortion in the (001) planes and significant volume reduction. Furthermore, the B19' → P1[combining macron] transition is dominated by the γ shearing mode with pronounced distortion in the (010) planes and slight volume expansion. The cumulative effect of both processes activates the lowering and eventual breaking of symmetry in the precursor phases and drives the permanent deformation and shape memory loss. We further show that the P1[combining macron]-NiTi structure is stabilized (over B19' structure) by kinetics. The findings of this study will stimulate further studies on how to retain and improve the shape memory feature in NiTi and other binary smart alloys to prevent property failure when used in the fabrication of devices operated in the high temperature and pressure regime.

Dataset on the evaluation of chemical and mechanical properties of steel rods from local steel plants and collapsed building sites

The quality of steel rods used in structural applications has been subjected to continuous scrutiny by researchers in Nigeria. In this data article, the experimental data on the chemical and mechanical properties of steel rods from collapsed building sites and local steel plants have been reported. The chemical composition consisting of carbon, manganese, silicon, sulphur, phosphorus among other elements were recorded using an optical emission spectrometer. Some of the main elements were used to evaluate the carbon equivalent value and the results are reported in this article. The yield strength, ultimate tensile strength and percentage elongation were also presented as obtained from the universal testing machine. The hardness values of the steel rod samples were also presented.

Experimental data on mechanical properties evaluation of medium carbon steel quenched in different waste media

Several wastes can be instrumental in the improvement of the mechanical properties of medium carbon steel when quenched. The quenching media employed such as coconut water (CW), pap water (PW) and spent engine oil (SPE) have been largely considered as wastes. The data in this article are related to the research article titled “Mechanical Properties Improvement Evaluation of Medium Carbon Steels Quenched in Different Media” (Ikubanni et al., 2017) [1]. The article provides information on the mechanical properties evaluation of medium carbon steel quenched in different media. Twenty-seven (27) samples of medium carbon steel samples were heated to temperatures of 730 °C, 760 °C and 790 °C and soaked for 30, 45 and 60 min respectively. The test results recorded include hardness value, yield strength (YS) and the ultimate tensile strength (UTS) for each of the samples at different heating temperatures and soaking time for the different quenching media.

B1-B2 phase transition mechanism and pathway of PbS under pressure

Experimental studies at finite Pressure-Temperature (P-T) conditions and a theoretical study at 0 K of the phase transition in lead sulphide (PbS) have been inconclusive. Many studies that have been done to understand structural transformation in PbS can broadly be classified into two main ideological streams-one with Pnma and another with Cmcm orthorhombic intermediate phase. To foster better understanding of this phenomenon, we present the result of the first-principles study of phase transition in PbS at finite temperature. We employed the particle swarm-intelligence optimization algorithm for the 0 K structure search and first-principles metadynamics simulations to study the phase transition pathway of PbS from the ambient pressure, 0 K Fm-3m structure to the high-pressure Pm-3m phase under experimentally achievable P-T conditions. Significantly, our calculation shows that both streams are achievable under specific P-T conditions. We further uncover new tetragonal and monoclinic structures of PbS with space group P2₁/c and I4₁/amd, respectively. We propose the P2₁/c and I4₁/amd as a precursor phase to the Pnma and Cmcm phases, respectively. We investigated the stability of the new structures and found them to be dynamically stable at their stability pressure range. Electronic structure calculations reveal that both P2₁/c and I4₁/amd phases are semiconducting with direct and indirect bandgap energies of 0.69(5) eV and 0.97(3) eV, respectively. In general, both P2₁/c and I4₁/amd phases were found to be energetically competitive with their respective orthorhombic successors.

Pseudohyperglycemia: Effects of Unwashed Hand after Fruit Peeling or Handling on Fingertips Blood Glucose Monitoring Results

BACKGROUND

Self-monitoring of blood glucose (SMBG) is an important component of management for diabetes mellitus (DM), especially in T1DM and T2DM patients who are on insulin therapy. Adequate blood glucose monitoring and prompt intervention are necessary to prevent blood glucose (BG) fluctuation and delay long-term diabetes complications. People with DM are advised to clean their hands before SMBG to remove any dirt or food residue that might affect the reading.

AIM

The study tested the hypothesis that falsely elevated BG levels from fingertip occur after peeling or handling fruits in an unwashed hand.

METHODS

Fifty apparently healthy nondiabetes volunteers were enrolled. Capillary BG samples were collected from the fingertips after peeling or handling apple, orange, banana, watermelon, and pawpaw, followed by no hand washing for 1 h, cleaning the fingertip with alcohol swab once, five times, and washing hand thoroughly with tap water and drying. These samples were then analyzed with two different glucose meters.

RESULTS

The mean BG values, measured from fingertip blood samples after peeling, and handling any of the fruits followed by no hand washing were significantly high, even after cleaning fingertip with a swab of alcohol once. However, there were no significant difference in BG levels measured after peeling and handling fruits followed by hand washing and the level of BG before peeling and handling fruits.

CONCLUSION

Handling of peeled fruits with no hand washing with tap water is associated with overestimation of capillary BG (Pseudohyperglycemia) monitored with glucose meters.

Risk Factors for Apical Periodontitis Sub-Urban Adult Population

AIMS AND OBJECTIVES

To assess the risk factors of apical periodontitis (AP) in a Nigerian sub-urban adult population and to compare the findings with those previously reported for various population groups.

MATERIALS AND METHODS

The study was based on a full mouth radiographic survey of 285 patients. Patients' age ranged from 18-60 years. All teeth were assessed individually and data recorded for caries, fractured / cracked teeth, root fillings, and tooth restorations. The gender, smoking habit, and frequency of dental visit were also recorded. Multiple logistic regression analyses were performed to identify predictors of AP in the individual.

RESULTS

The prevalence of AP was 74.4%. The average number of teeth with AP per patient was 2.8 (range 1-5). AP was found to be more prevalent among people 40- 49 years old (87.2%). Primary carious lesions, fractured / cracked teeth, root fillings and coronal fillings were associated with the incidence of AP in the individual. Fractured teeth had a higher risk of developing AP than carious teeth. The presence of root fillings and coronal restorations were also associated with the development of AP. Smoking (OR=3.82; CI=2.17-6.75) and irregular dental visit (OR=6.73; CI=3.75-12.06) were statistically significant risk factors for developing AP. Gender was not a risk factor for AP (OR=0.86; CI=0.50-1.46).

CONCLUSION

The prevalence of AP among adult Nigerians is slightly higher than reported figures for many Western societies. Fractured/cracked teeth had a higher risk of developing AP than carious teeth; hence patients with fractured / cracked teeth should seek treatment early to prevent the development of AP.

Onion (Allium cepa) extract prevents cadmium induced renal dysfunction

Cadmium (Cd), a heavy metal, is known for its adverse effects on the body. In this study, the lowering effect of Cd on renal clearance (RC) was investigated, and Allium cepa extract (AcE) (an antioxidant) was pre-administered orally to prevent Cd's adverse effects. Seventy-two Wistar rats, grouped into three (n = 24), were used for this study. While Group C was given 1.0 ml of AcE daily (orally), Group A and Group B were given distilled water. AcE administration was done for eight weeks. Afterwards B and C were then given 1.5 ml/kg BW of 0.3 mg/L 3CdSO(4).8H(2)O intraperitoneally for three consecutive days. The results obtained showed that Cd causes significant reduction in the 24 hour urine volume (from 3.017 +/- 0.125 to 2.433 +/- 0.118 ml), RC (from 3.258 +/- 0.114 to 1.357 +/- 0.104 ml/h for creatinine; and from 0.350 +/- 0.057 to 0.185 +/- 0.055 ml/h for urea), plasma and tissue SOD and CAT activity (form 1.644 +/- 0.036 to 1.307 +/- 0.056 u/g protein for plasma SOD; 0.391 +/- 0.029 to 0.2692 +/- 0.031 u/protein for plasma CAT; 1.695 +/- 0.034 to 1.327 +/- 0.049 u/g protein for tissues SOD; and from 0.350 +/- 0.027 to 0.273 +/- 0.043 u for tissue CAT), and significant MDA increased in plasma (from 1496.79 +/- 1.321 to 1679.48 +/- 143.29 mug/g protein) and tissue (from 1265.22 +/- 2.285 to 1669.87 +/- 14.61 mug/dL). AcE, however, prevents these Cd's adverse effects. This findings lead to the conclusion Cd exposure causes renal dysfunction, but oral administration of onion could prevent it.

Legionella drozanskii sp. nov., Legionella rowbothamii sp. nov. and Legionella fallonii sp. nov.: three unusual new Legionella species

Seven strains of Legionella-like amoebal pathogens (LLAPs) were characterized on the basis of their cultural and staining characteristics, biochemical reactions, serology, cellular fatty acids (CFAs), isoprenoid quinone composition, total DNA relatedness, analysis of 16S rRNA and macrophage infectivity potentiator (mip) gene sequence analyses. All seven strains exhibited limited growth on buffered charcoal yeast extract alpha (BCYE) agar, required cysteine for growth and contained branched-chain CFAs and quinones typical of Legionella species. The bacilli were Gram-negative and catalase-positive. There were varying degrees of serological cross-reactions between these LLAP strains and other previously described Legionella species. Results from the various tests revealed that four LLAP strains represent three unusual new species of Legionella: Legionella drozanskii sp. nov., type strain LLAP-1T; Legionella rowbothamii sp. nov., type strain LLAP-6T; and Legionella fallonii sp. nov., type strain LLAP-10T. Three other LLAP strains, designated LLAP-7FL, LLAP-7NF and LLAP-9, were shown to be members of the species Legionella lytica. The deductions made from the phenetic characteristics of these bacteria were consistent with the phylogenetic relationships inferred from 16S rRNA and mip gene sequence analyses. This study is the first to speciate LLAP strains on the basis of data including quantitative DNA hybridization.