Showing papers by "Linköping University published in 1991"

System identification using Laguerre models

Abstract: The traditional approach of expanding transfer functions and noise models in the delay operator to obtain linear-in-the-parameters predictor models leads to approximations of very high order in cases of rapid sampling and/or dispersion in time constants. By using prior information about the time constants of the system more appropriate expansions, related to Laguerre networks, are introduced and analyzed. It is shown that the model order can be reduced, compared to ARX (FIR, AR) modeling, by using Laguerre models. Furthermore, the numerical accuracy of the corresponding linear regression estimation problem is improved by a suitable choice of the Laguerre parameter. Consistency (error bounds), persistence of excitation conditions. and asymptotic statistical properties are investigated. This analysis is based on the result that the covariance matrix of the regression vector of a Laguerre model has a Toeplitz structure. >

Sensor array processing based on subspace fitting

Abstract: Algorithms for estimating unknown signal parameters from the measured output of a sensor array are considered in connection with the subspace fitting problem. The methods considered are the deterministic maximum likelihood method (ML), ESPRIT, and a recently proposed multidimensional signal subspace method. These methods are formulated in a subspace-fitting-based framework, which provides insight into their algebraic and asymptotic relations. It is shown that by introducing a specific weighting matrix, the multidimensional signal subspace method can achieve the same asymptotic properties as the ML method. The asymptotic distribution of the estimation error is derived for a general subspace weighting, and the weighting that provides minimum variance estimates is identified. The resulting optimal technique is termed the weighted subspace fitting (WSF) method. Numerical examples indicate that the asymptotic variance of the WSF estimates coincides with the Cramer-Rao bound. The performance improvement compared to the other techniques is found to be most prominent for highly correlated signals. >

Multidimensional orientation estimation with applications to texture analysis and optical flow

Abstract: The problem of detection of orientation in finite dimensional Euclidean spaces is solved in the least squares sense. The theory is developed for the case when such orientation computations are necessary at all local neighborhoods of the n-dimensional Euclidean space. Detection of orientation is shown to correspond to fitting an axis or a plane to the Fourier transform of an n-dimensional structure. The solution of this problem is related to the solution of a well-known matrix eigenvalue problem. The computations can be performed in the spatial domain without actually doing a Fourier transformation. Along with the orientation estimate, a certainty measure, based on the error of the fit, is proposed. Two applications in image analysis are considered: texture segmentation and optical flow. The theory is verified by experiments which confirm accurate orientation estimates and reliable certainty measures in the presence of noise. The comparative results indicate that the theory produces algorithms computing robust texture features as well as optical flow. >

Detection and estimation in sensor arrays using weighted subspace fitting

Abstract: The problem of signal parameter estimation of narrowband emitter signals impinging on an array of sensors is addressed. A multidimensional estimation procedure that applies to arbitrary array structures and signal correlation is proposed. The method is based on the recently introduced weighted subspace fitting (WSF) criterion and includes schemes for both detecting the number of sources and estimating the signal parameters. A Gauss-Newton-type method is presented for solving the multidimensional WSF and maximum-likelihood optimization problems. The global and local properties of the search procedure are investigated through computer simulations. Most methods require knowledge of the number of coherent/noncoherent signals present. A scheme for consistently estimating this is proposed based on an asymptotic analysis of the WSF cost function. The performance of the detection scheme is also investigated through simulations. >

An adaptive array for mobile communication systems

Abstract: The use of adaptive antenna techniques to increase the channel capacity is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction-finding followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements. >

Performance analysis of the total least squares ESPRIT algorithm

Abstract: The asymptotic distribution of the estimation error for the total least squares (TLS) version of ESPRIT is derived. The application to a uniform linear array is treated in some detail, and a generalization of ESPRIT to include row weighting is discussed. The Cramer-Rao bound (CRB) for the ESPRIT problem formulation is derived and found to coincide with the asymptotic variance of the TLS ESPRIT estimates through numerical examples. A comparison of this method to least squares ESPRIT, MUSIC, and Root-MUSIC as well as to the CRB for a calibrated array is also presented. TLS ESPRIT is found to be competitive with the other methods, and the performance is close to the calibrated CRB for many cases of practical interest. For highly correlated signals, however, the performance deviates significantly from the calibrated CRB. Simulations are included to illustrate the applicability of the theoretical results to a finite number of data. >

Abiotic reduction of mercury by humic substances in aquatic system — an important process for the mercury cycle

Abstract: The potential ability of humic substances to reduce Hg(II) to Hg(0) in aqueous systems and, consequently, strongly influence Hg speciation and mobility in the environment is known but has not been studied in detail. A demonstration of the redox behavior of Hg in the presence of humic substances is made in the present work. Calculations show that the reduction is thermodynamically possible. The effects of some chemical parameters (pH, aerobic/anaerobic conditions, presence of chloride) on the process were studied experimentally. Hg(0) production was highest in O2-free systems in the absence of chloride at pH ca 4.5, when ca 25% of initially 2x10−6 M Hg(II) was reduced to Hg(0) in 50 hr. The presence of a competing ion (10−4 M Eu) in the system as well as methylation of the carboxyl groups in the humic substance considerably reduced the Hg(0) production. The practical importance of the abiotic reduction of Hg in the environment is pointed out.

Effects of acidification and natural organic materials on the mobility of arsenic in the environment

Abstract: Effects of acidification on adsorption and potential mobility of various As forms have been studied in batch-type distribution experiments. The adsorption of As on alumina decreased in the order As(V) > MMAA = DMAA > As(III) at pH below 6 and As(V) > As(III) > MMAA = DMAA at pH above 6. The adsorption reached a maximum around pH 5 for As(V), pH 7 for As(III) and pH 4 for MMAA and DMAA. The presence of a fulvic acid at concentration levels of 10 mg L−1 or higher generally reduced the As adsorption in the pH range 5 to 7. In light of both laboratory and field observations environmental acidification would increase the leaching of As from soils or sediments to surface and groundwaters under reducing conditions, but could also reduce the mobility due to enhanced adsorption under oxidizing conditions.

Al induced crystallization of a‐Si

Abstract: The crystallization of amorphous Si induced by Al during heat treatment has been investigated by cross section and plan view transmission electron microscopy. The lowest temperature of Al induced crystallization of amorphous Si was found to be 440 K. The crystallization temperature, however, depends on the thickness of Al layers in layered structures and on the concentration of Al in co‐deposited layers below 1‐nm‐layer thickness and 15 at.% of Al concentration, respectively. Al‐induced crystallization in layered structures starts at the Al/amorphous Si interfaces and is located close to them. The amount of crystallized Si depends on the quantity of Al and on the temperature and increases with them. The mechanism of crystallization involves intermixing of Al with Si and the formation of an alloy of high metal concentration in the amorphous/crystalline interface. When the formation of this alloy is not assured due to low Al concentration, then crystallization does not start or the process of crystallization stops. In Al induced crystallization the nucleation of polycrystalline Si grains rather than their crystal growth is affected.

Prognostic parameters in spontaneous intracerebral hematomas with special reference to anticoagulant treatment.

Abstract: We examined a series of 200 consecutive patients with spontaneous intracerebral hematoma clinically and by computed tomography, excluding patients with trauma, aneurysm, or tumor. Hematoma volume varied from 1 to 230 (average 35) ml, and overall mortality was 30% (60 patients). Of the 200 patients, 14% (28) were receiving anticoagulants; among these 28 patients hematoma volume averaged 72 ml and mortality 57% (16 patients). The 140 survivors were followed for 2-24 months. Our findings indicate that anticoagulation therapy after previous cerebral infarction or embolism of cardiogenic origin did not predispose to intracerebral hemorrhage. Prognosis was poor when the initial level of consciousness was low and the hematoma volume exceeded 50 ml in combination with dilatation of the contralateral ventricle. An intracerebral hematoma of greater than 80 ml volume was always fatal, regardless of therapy. With volumes of 40-80 ml, early surgical evacuation of the lobar hematoma may improve outcome.

Microstructures of TiN films grown by various physical vapour deposition techniques

Abstract: A study has been made of TiN coatings deposited on steel substrates by five commercially available physical vapour deposition (PVD) methods; low voltage electron beam evaporation, triode high voltage electron beam evaporation, random-arc evaporation, steered-arc evaporation and magnetron sputtering. The microstructure and substrate-film interfacial microchemistry of the films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) together with energy-dispersive X-ray spectroscopy (EDX), cross-sectional transmission electron microscopy (XTEM) and scanning transmission electron microscopy (STEM) combined with EDX analyses of XTEM samples. The XRD analyses showed that all the films were in a state of compressive stress with interplanar distances as much as 1.7% higher than reference bulk values. SEM examination revealed only minor variations in surface roughness among the samples except for the arc-evaporated films which contained large droplets and craters resulting from the detachment of droplets. The number density and average sizes of droplets and craters were lower in the steered-arc sample than in the random-arc sample. XTEM analyses showed that all the films had columnar structures with clearly defined substrate-film interfacial layers. The films appeared dense except for the magnetron-sputtered sample which exhibited intercolumnar porosity. STEM-EDX analyses showed large variations in the microchemistry of the substrate-film interfacial regions which consisted, depending on the sample, of renucleated near-surface substrate grains, intentionally (or, in at least one case, unintentionally) introduced foreign material or gas-bubble-like inclusions. However, the microchemistry of these interfacial regions was, in most cases, understandable on the basis of the substrate pretreatment and/or choice of film growth parameters.

Defect structure and phase transitions in epitaxial metastable cubic Ti0.5Al0.5N alloys grown on MgO(001) by ultra‐high‐vacuum magnetron sputter deposition

Abstract: Ti0.5Al0.5N alloy films, typically 1.5 μm thick, were grown on MgO(001) at temperatures Ts between 400 and 850 °C by ultra‐high‐vacuum reactive magnetron sputtering in pure N2. Films grown at Ts between ≂480 and 560 °C were single crystals in which the lattice misfit strain was partially relieved by glide of 〈001〉 misfit dislocations, with Burgers vector =a0/2〈011〉, on {011} planes. Cross‐sectional transmission electron microscopy investigation showed no evidence of residual extended defects in the films until thicknesses of ≂150 nm at which point threading dislocations, oriented along the [001] growth direction, were observed. Surface‐initiated spinodal decomposition, resulting in the formation of compositionally modulated NaCl‐structure platelets along [001] with width ≂1 nm, occurred over a narrow growth temperature range between 540 and 560 °C as a precursor to bulk phase separation of wurtzite‐structure AlN at Ts≥560 °C. The alloy was continuously depleted of AlN at higher growth temperatures until ...

Pharmacodynamics of daptomycin and vancomycin on Enterococcus faecalis and Staphylococcus aureus demonstrated by studies of initial killing and postantibiotic effect and influence of Ca2+ and albumin on these drugs.

Abstract: The pharmacodynamics of daptomycin and vancomycin on Enterococcus faecalis ATCC 29212 and Staphylococcus aureus ATCC 25923 were investigated by studying the postantibiotic effect (PAE) and initial killing The influence of Ca2+ and albumin on these drugs was also evaluated The PAE was studied by use of bioluminescence assay of bacterial ATP Daptomycin at clinically achievable concentrations produced a dose-dependent PAE on E faecalis (06 to 67 h) and S aureus (10 to 63 h) The long PAE of daptomycin was seen simultaneously with a potent dose-dependent initial killing assayed by viable count determination The initial change in bacterial ATP was not as extensive as the decrease in viability Vancomycin at corresponding concentrations produced shorter PAEs on E faecalis (05 to 10 h) and S aureus (13 to 18 h) This coincides with a weak non-dose-dependent initial change in viability and intracellular ATP The MICs of vancomycin were not influenced by different Ca2+ concentrations or by the addition of albumin to the broth The MICs of daptomycin for both strains were lowered, and the PAEs were prolonged with increasing concentrations of Ca2+ in the broth The PAE of daptomycin was Ca2+ dependent to the same extent as the MIC was In the presence of physiological concentrations of albumin and free Ca2+, the PAEs of daptomycin on both strains were reduced and the MICs were increased in comparison with the results obtained in pure Mueller-Hinton broth with approximately the same free Ca2+ concentration This decrease in daptomycin activity was considered to be due to the albumin binding of daptomycin Despite the albumin binding of daptomycin, the PAE produced on E faecalis and S aureus in the presence of a physiological free Ca2+ concentration was still over 6 h at clinically achievable concentrations

Chemisorption of -cysteine and 3-mercaptopropionic acid on gold and copper surfaces: An infrared reflection-absorption study

Abstract: Infrared reflection-absorption spectroscopy (IRAS) has been used to study the chemisorption of l -cysteine ( l -Cys) and 3-mercaptopropionic acid (MPA) on evaporated gold and copper surfaces. The infrared data show that monomolecular films are formed for both l -Cys and MPA on gold, and that the bonding to the surface occurs primarily via the SH group. More complex reactions occur on the copper surface. MPA forms a multilayer structure on copper when adsorbed from solution at pH 3.5. In the very first layer the SH group is coordinated to the copper surface and the CO2− group to dissolved copper ions. The subsequent layers consist of MPA molecules in the dimeric form. Dissolution of copper is not very pronounced at high pH values as evidenced by the formation of a sodium salt instead of a cuprous (cupric) complex when MPA is adsorbed from a NaOH solution at pH 11.5. l -Cys also forms a complex ionic structure on copper where the SH, NH2 and CO2− groups appear to be involved in the bonding to the copper surface and/or dissolved copper ions.

Cardiac rehabilitation--a cost analysis.

Abstract: This economic evaluation is based on a 5-year follow-up study comparing a comprehensive cardiac rehabilitation programme with standard care after myocardial infarction (MI). The intervention group consisted of 147 non-selected MI patients aged less than 65 years, who were participating in a rehabilitation programme consisting of follow-up at a post-MI clinic, health education and physical training in out-patient groups. The control group consisted of a non-selected MI-population aged less than 65 years (n = 158), who were receiving standard care. The rehabilitation programme did not increase the health-care costs of post-MI care, as the increase in cost due to participation in the programme was balanced by a decrease in readmissions for cardiovascular diseases. On average, the rehabilitated patient returned to work more frequently, resulting in decreased costs due to loss of production. The mean patient total cost of a 5-year MI follow-up was SEK 73,500 lower in the rehabilitated group. The outstanding winner of the rehabilitation programme was the Swedish National Health Insurance System (NHIS). It must be concluded that the comprehensive cardiac rehabilitation programme is a major strategy that leads to both lowered costs and positive health effects. The cardiac rehabilitation programme is therefore highly cost-effective.

Aspects on estimation of the risk of calcium oxalate crystallization in urine.

Abstract: A previously formulated simplified estimate of the ion activity product of calcium oxalate, AP(CaOx) index, was modified in order to better correspond numerically to the ion activity product obtained by computed iterative approximation with the EQUIL 2 program The new index, AP(CaOx) index EQ, was given the following form for a 4-hour urine: 19 x Ca(084) x Ox x Mg-(012) x Cit-(022) x V-(103), where the excretion of calcium, oxalate (Ox), magnesium and citrate (Cit) was expressed in millimoles excreted during the period, and urine volume (V) in liters There was a good correlation between AP(CaOx) index and AP(CaOx) index EQ (r = 098) A standardized index calculated for a 24-hour urine volume of 15 liters, AP(CaOx) index EQ(s), was significantly higher in stoneforming men (p less than 0001) and women (p less than 0001) than in normal subjects The mean ion activity products of CaOx at the start of crystallization in salt solutions and dialyzed urine were 274 +/- 025 x 10(-8) and 350 +/- 033 x 10(-8) (mol/l)2, respectively In the urine from normal subjects, AP(CaOx) index EQ at the point of crystallization was 43 +/- 11 and in the urine from stone formers 28 +/- 05 (p less than 0001) From calculation of AP(CaOx) index EQ in hourly collected urine, it was assumed that the risk of exceeding the level where crystallization starts during periods with the highest supersaturation can be anticipated when the 24-hour AP(CaOx) index EQ value exceeds 20

A protocol to set up shared secret schemes without the assistance of mutually trusted party

Abstract: All shared secret or shared control schemes devised thus far are autocratic in the sense that they depend in their realization on the existence of a single party—which may be either an individual or a device—that is unconditionally trusted by all the participants in the scheme [5,6]. The function of this trusted party is to first choose the secret (piece of information) and then to construct and distribute in secret to each of the participants the private pieces of information which are their shares in the shared secret or control scheme. The private pieces of information are constructed in such a way that any authorized concurrence (subset) of the participants will jointly have sufficient information about the secret to reconstruct it while no unauthorized collection of them will be able to do so. For many applications, though, there is no one who is trusted by all of the participants, and in the extreme case, no one who is trusted by anyone else. In the absence of a trusted party or authority, no one can be trusted to know the secret and hence—until now—it has appeared to be impossible to construct and distribute the private pieces of information needed to realize a shared control scheme. It is worth noting that in commercial and/or internation(al) applications, this situation is more nearly the norm than the exception.

Binding and biological effects of insulin, insulin analogues and insulin-like growth factors in rat aortic smooth muscle cells. Comparison of maximal growth promoting activities.

Abstract: Binding and growth promoting effects of insulin, insulin analogues modified in the B chain, proinsulin, insulin-like growth factor-I and -II were studied in cultured rat aortic smooth muscle cells. Specific binding of125I-insulin was 0.9±0.2% of total 125I-insulin added, and the IC50-value was estimated to 8.9 pmol/1. The insulin analogue B10 Asp tended to be more potent than insulin in displacing 125I-insulin, B28 Asp was equipotent, B9 Asp/B27 Glu was approximately 100 times less potent and insulin-like growth factor-I more than 1000 times less potent than insulin. Specific binding of 125I-insulin-like growth factor-I after 4 h incubation at 10 °C was five times higher than the specific binding of insulin (4.4±0.4% of total 125I-insulin-like growth factor-I added), and the IC50-value was 0.3 nmol/l. Insulin was approximately 500 times less potent than insulin-like growth factor-I in displacing 125I-insulin-like growth factor-I. The insulin analogue B10 Asp was slightly more potent and analogue B28 Asp was equipotent with insulin. Analogue B9 Asp/B27 Glu was ten times less potent and proinsulin was more than ten times less potent than insulin. The order of potency was similar for 3H-thymidine incorporation into DNA: insulin-like growth factor-I > B10 Asp > insulin-like growth factor-II > insulin > B28 Asp > B9 Asp/B27 Glu > proinsulin. The maximal effect of insulin-like growth factor-I on 3H-thymidine incorporation was 71±16% higher than the maximal effect of insulin. The maximal effect of insulin-like growth factor-II was at least as high as the effect of insulin-like growth factor-I. Furthermore, the maximal effect of B10 Asp was 62±10% higher than the maximal effect of insulin. Insulin-like growth factor-I and B10 Asp tended to increase cell number more than insulin. In conclusion, this study shows that insulin analogues interact with different potencies with receptors for insulin and insulin-like growth factor-I in vascular smooth muscle cells and that insulin-like growth factors and the insulin analogue B10 Asp have more pronounced growth effects than insulin. Substitution of the amino acid Asp for His at position B10 in insulin makes the molecule more similar to insulin-like growth factor-I, chemically and probably also biologically.

Issues in system identification

Abstract: A brief outline is given of mainstream system identifications, i.e. the typical approaches, algorithms, and properties in the world of data-based model construction. A number of important problems that are not sufficiently understood are pointed out. Particular attention is given to the problem of how to develop constructive and systematic ways to determine suitable model structures, i.e. to move from parameter estimation to system identification. >

Ethanol absorption across human skin measured by in vivo microdialysis technique.

Abstract: Microdialysis, a new bioanalytical sampling technique enables measurement of substances in the extracellular space. This initial study investigates the technique's usefulness in the field of percutaneous absorption of solvents, using ethanol as test substance. Microdialysis probes are equipped at the tip with a semi-permeable polycarbonate membrane which permits passive diffusion of substances. Ethanol does not damage the membrane. In vitro recovery for ethanol is good. Probes were inserted via a guide into the skin of the ventral forearm in 7 volunteers. 99.5% ethanol was applied to the skin in excess in a glass reservoir. The probe was perfused at a flow of 1 microliter/min. 50 microliters samples were analysed by gas chromatography. Absorption of ethanol was demonstrated in all subjects. Values from the 9 probes inserted ranged from 10 micrograms/ml to 800 micrograms/ml. The variation may be explained by inter-test or inter-individual variability in ethanol absorption. Individual metabolic capacity may be of importance. The method opens new possibilities in the investigation of skin barrier function in man.

Double-edge-triggered D-flip-flops for high-speed CMOS circuits

Abstract: Two circuits are proposed for double edge-triggered D flip-flops (DETDFFs). A DETDFF responds to both edges of the clock pulse. As compared with positive or negative edge-triggered flip-flops, a DETDFF has advantages in terms of power dissipation and speed. Delay figures for these circuits are measured by simulation. It is shown that these circuits are faster and have lower transistor counts than previously reported circuits. It is shown that these flip-flops can be used at 320-400-MHz clock frequency in a 2- mu m technology. >

Photoplethysmography. Part 2. Influence of light source wavelength.

Abstract: When the microvascular blood perfusion in human skin is measured by photoplethysmography (PPG), infra-red light (800-960 nm) is normally used as the light source. The PPG signal, which consists of a pulsatile (AC) and a slowly fluctuating (DC) component, was studied at different optical wavelengths utilising optical fibres for guiding the light to and from the skin surface. Finger and forearm skin was examined and high and low skin blood perfusion was brought about by local water-induced temperature provocation. The analysis of the measurement results provided evidence that the use of shorter wavelengths in PPG (AC) for monitoring skin perfusion changes could be applicable. The use of different optical wavelengths also raises the possibility of recording perfusing changes at different depths in the superficial tissue. The sweat water content in stratum corneum of human skin will probably determine the total amount of reflected and backscattered radiation reaching the photodetector. This is important when the skin perfusion is changed by alterations in the environmental temperature conditions activating the sweat glands in tissue. Temperature-dependent optical characteristics of blood-free skin tissue may explain the limited ability of the DC component of PPG to monitor skin perfusion changes.

Price and quantity in international comparisons of health care expenditure

Abstract: An important omission from earlier cross-national comparisons of health care expenditure has been the failure to distinguish between price and quantity. Using recent data on purchasing power parities, the purpose of this article is to report some preliminary results regarding health care expenditure and quantity across 22 OECD countries. The article concludes that, contrary to what has been suggested in some recent articles, the relative price of health care is not correlated to the aggregate per capita income. The fraction of the national income that is devoted to health care provision increases with the per capita income regardless of whether health care is measured in terms of expenditure or quantity. The relative price of health care has a rationing effect on the quantity of health care that is offered, with a price alasticity close to minus one. The latter finding means that the health care expenditure is not greater in countries with higherprices. Furthermore, the differences in health care expendit...

Structure of low-coverage phases of Al, Ga, and In on Si(100)

Abstract: The atomic structures of the low-coverage 2\ifmmode\times\else\texttimes\fi{}2 phases of Al, Ga, and In on Si(100) were determined on the basis of first-principles total-energy calculations and angle-resolved photoemission experiments. The proposed structure consists of rows of ad-dimers, with the ad-dimers oriented parallel to the underlying Si dimers. Angle-resolved photoemission experiments performed for Si(100)2\ifmmode\times\else\texttimes\fi{}2:ln are in good agreement with the calculated surface-state dispersions for the parallel ad-dimer model. The existence of lower coverage 3\ifmmode\times\else\texttimes\fi{}2 and 5\ifmmode\times\else\texttimes\fi{}2 phases results from repulsive interactions between neighboring rows of ad-dimers.

The accordance of diagnoses in a computerized sick-leave register with doctor's certificates and medical records.

Abstract: A register has been built for planned epidemiological studies of sick-leave, containing all cases exceeding 6 days in a population of 184,000, over a period of 3 years. The diagnoses were coded from medical certificates. To assess the quality of this information this study reviews the medical certificates of 2,364 cases. In 299 cases the corresponding medical records are reviewed and independent diagnoses made. The coding and entering of data into the register is correct in 98% of cases. The independently-made diagnoses match exactly the ones registered in 50% of cases. When grouping the diagnoses into 39 groups, the match on group level is 72%. Ten percentage points of the mismatch are caused by specified overlaps between groups. The remaining 18% mismatch is caused mainly by different interpretations or unspecific labelling of the disease states, not so much by them being obscure in themselves or by doctor covering up unpleasant diagnoses.