A Robust Method for the Unsupervised Scoring of Immunohistochemical Staining

Immunohistochemistry is a powerful technique that is widely used in biomedical research and clinics; it allows one to determine the expression levels of some proteins of interest in tissue samples using color intensity due to the expression of biomarkers with specific antibodies. As such, immunohistochemical images are complex and their features are difficult to quantify. Recently, we proposed a novel method, including a first separation stage based on non-negative matrix factorization (NMF), that achieved good results. However, this method was highly dependent on the parameters that control sparseness and non-negativity, as well as on algorithm initialization. Furthermore, the previously proposed method required a reference image as a starting point for the NMF algorithm. In the present work, we propose a new, simpler and more robust method for the automated, unsupervised scoring of immunohistochemical images based on bright field. Our work is focused on images from tumor tissues marked with blue (nuclei) and brown (protein of interest) stains. The new proposed method represents a simpler approach that, on the one hand, avoids the use of NMF in the separation stage and, on the other hand, circumvents the need for a control image. This new approach determines the subspace spanned by the two colors of interest using principal component analysis (PCA) with dimension reduction. This subspace is a two-dimensional space, allowing for color vector determination by considering the point density peaks. A new scoring stage is also developed in our method that, again, avoids reference images, making the procedure more robust and less dependent on parameters. Semi-quantitative image scoring experiments using five categories exhibit promising and consistent results when compared to manual scoring carried out by experts.

Estimation of the post-mortem interval of human skeletal remains using Raman spectroscopy and chemometrics

An important demand exists in the field of forensic analysis to objectively determine the post-mortem interval (PMI) when human skeletal remains are discovered. It is widely known that bones undergo different chemical and physical processes after death, mainly due to their interaction with the environment in which they are found, although it is not known exactly what these processes consist of. Multiple techniques have been used so far to follow up these and other post-mortem changes and thus establish the time elapsed since the individual's death, but they present important drawbacks in terms of reliability and accuracy. The aim of this research was to propose an analytical methodology capable of determining the PMI by using non-destructive Raman spectroscopy measurements of human skeletal remains. The recorded Raman spectra provided valuable and potentially useful information from which a multivariate study was performed by means of orthogonal partial least squares regression (OPLSR) in order to correlate the PMI with the detected spectral modifications. A collection of 53 real human skeletal remains with known PMI (15 years ≤ PMI ≤ 87 years) was analysed and used for building and validating the OPLS model. The PMI of 10 out of 14 validation samples could be determined with an accuracy error of less than 30%, demonstrating the adequate predictive performance of the OPLS model even in spite of the large inter-individual variability it handled. This opens up the possibility of applying the OPLS model in combination with non-destructive techniques to the determination of the PMI of human skeletal remains that have been buried in conditions similar or equal to those of cemetery niches and in a geographic location with a Mediterranean climate, which is an important achievement for forensic medicine and anthropology.

Critically ill COVID-19 patients attended by anesthesiologists in northwestern Spain: a multicenter prospective observational study

BACKGROUND AND OBJECTIVES

There are limited information on outcome, complications and treatments of critically ill COVID-19 patients requiring admission to an intensive care unit (ICU). The aim of this study is to describe the clinical ICU course, treatments used, complications and outcomes, of critically ill COVID-19 patients admitted in seven ICU in Galicia region during the 2020 March-April pandemic peak.

METHODS

Between March 21 and April 19, 2020, we evaluated critically ill COVID-19 patients admitted to the ICU of Anesthesia of seven hospitals in Galicia, northwestern Spain. Outcome, complications, and treatments were monitored until May 6, 2020, the final date of follow-up.

RESULTS

A total of 97 critically ill COVID-19 patients were included. During ICU stay, mechanical ventilation became necessary in 80 (82.5%) patients, and tracheostomy in 22 (22.7%) patients. Prone position was used frequently in both intubated (67.5%) and awake (27.8%) patients. Medications consisted of antivirals agents (92.7%), corticosteroids (93.8%), tocilizumab (57.7%), and intermediate or high doses of anticoagulants (83.5%). The most frequent complications were ICU-acquired infection (52.6%), thrombosis events (16.5%), and reintubation (9.3%). After a median follow-up of 42 (34-45) days, 15 patients (15.5%) deceased, 73 patients (75.2%) had been discharged from ICU, and nine patients (9.3%) were still in the ICU.

CONCLUSIONS

A high proportion of our critically ill COVID-19 patients required mechanical ventilation, prone positioning, antiviral medication, corticosteroids, and anticoagulants. ICU complications were frequent, mainly infections and thrombotic events. We had a relatively low mortality of 15,5%.

Centroid-Based Clustering with αβ-Divergences

Centroid-based clustering is a widely used technique within unsupervised learning algorithms in many research fields. The success of any centroid-based clustering relies on the choice of the similarity measure under use. In recent years, most studies focused on including several divergence measures in the traditional hard k-means algorithm. In this article, we consider the problem of centroid-based clustering using the family of αβ-divergences, which is governed by two parameters, α and β. We propose a new iterative algorithm, αβ-k-means, giving closed-form solutions for the computation of the sided centroids. The algorithm can be fine-tuned by means of this pair of values, yielding a wide range of the most frequently used divergences. Moreover, it is guaranteed to converge to local minima for a wide range of values of the pair (α,β). Our theoretical contribution has been validated by several experiments performed with synthetic and real data and exploring the (α,β) plane. The numerical results obtained confirm the quality of the algorithm and its suitability to be used in several practical applications.

Colles' fractures: functional treatment in supination

PURPOSE OF THE STUDY

Abraham Colles classified and described fractures of the distal epiphyseal radius. He recommended the arm should be immobilized in a cast that extends from the base of the fingers to above the elbow, while holding this joint at ninety degrees of flexion the forearm in pronation and the wrist in slight flexion and ulnar deviation. We identified the brachioradialis muscle as the main culprit in the frequently observed loss of reduction of the fracture. Since the brachioradialis is attached to the distal region of the radius and functions as a flexor of the elbow when the forearm is in pronation, its stimulation easily displaces a reduced fracture, particularly if its geometry suggests axial instability. We concluded that post-reduction stabilization in supination was more desirable than in pronation.

MATERIAL AND METHODS

Prospective study of one hundred and fifty-six patients suffering from Colles' fractures who were treated with the functional method. Approximately one-half of the fractures were immobilized in pronation and the other half in supination. The median age of the patients was 49 years. After approximately eleven days of immobilization in an above-the-elbow cast that held the forearm in a relaxed attitude of supination and the wrist in slight flexion and ulnar deviation, a new cast or brace was applied. The appliance permitted flexion of the elbow and slightly limited extension. We utilized modified Lindstom criteria to assess radiological results, according to types of fractures and by groups treated in supination and pronation.

RESULTS

In the type I and III (non-displaced) fracture series there appeared to be no significant difference in the functional results between the pronation and supination treated groups. In the type II category, in the supinated fractures, there were 9 excellent, 4 good and no fair or poor results. In the pronated group 9 excellent, 8 good and one fair result. The functional results in type IV fractures treated in supination were excellent in 11 instances, good in 7 and fair in 2. In fractures treated in pronation there were 5 excellent, 10 good and 5 fair results. There were no poor results in either group. 85% of type II fractures and 85% of type IV fractures treated in supination had excellent or good results. In the pronation group, 67% had excellent or good results in type II and 40% in type IV classification. In combining the results for all types of braced Colles' fractures, (I-IV) 93% of the supination group and 87% of the pronation group achieved excellent or good functional results. In analyzing overall results regardless of type of fracture or position of immobilization, 90% of the patients had excellent or good results.

CONCLUSION

We treated Colles' fractures in supination and compared the results with those obtained when treated in pronation. The results indicated a lower incidence of re-displacement in the supination group. We developed a forearm brace that permits flexion of the elbow, but prevented pronation of the forearm, and limited extension of the elbow in approximately the last fifteen degrees. It permits minimally limited flexion of the wrist but prevents wrist dorsiflexion. It makes impossible any radial deviation. The place of surgery in the management of Colles' fractures should be limited to those fractures that when treated by non-surgical means are not likely to render satisfactory functional and cosmetic results. There is not at this time a consensus as to when to use the surgical approach. The complication rate from the surgery have not clearly identify superiority of one over the other. Nonetheless, the surgical treatment has a definite place in the armamentarium of the orthopaedic surgeon. In a number of situations, it is the treatment of choice.

Reflections on acromio-clavicular dislocations

A number of surgical and nonsurgical techniques have been used in the recent past for the treatment of this not uncommon traumatic condition. Thus far, no agreement has been reached regarding the method most likely to consistently render good results. Uppermost in determining the treatment has been the degree of displacement of the clavicle and the prevention of possible cosmetically unacceptable complications. Advances in the surgical care of most fractures and dislocations have lead to the current belief and practice among the majority of orthopaedic surgeons that every effort should be made to correct any deviation from the normal produced by the injury. I submit that skilful neglect and acceptance of acromio-clavicular dislocation is an option worth considering. When the dislocation is accepted, the vast majority of patients do well, functionally and aesthetically. Chronic pain is an extremely rare situation; and the resulting deformity, from the cosmetic point of view, an uncommon problem. If this is the case, what is the problem that reconstructive surgery proposes to address?

Solving permutations in frequency-domain for blind separation of an arbitrary number of speech sources

Blind separation of speech sources in reverberant environments is usually performed in the time-frequency domain, which gives rise to the permutation problem: the different ordering of estimated sources for different frequency components. A two-stage method to solve permutations with an arbitrary number of sources is proposed. The suggested procedure is based on the spectral consistency of the sources. At the first stage frequency bins are compared with each other, while at the second stage the neighboring frequencies are emphasized. Experiments for perfect separation situations and for live recordings show that the proposed method improves the results of existing approaches.

Beachrock formation in temperate coastlines: examples in sand-gravel beaches adjacent to the Nerbioi-Ibaizabal Estuary (Bilbao, Bay of Biscay, North of Spain)

Beachrocks are coastal sedimentary formations resulting from a relative rapid cementation of beach sediments by the precipitation of carbonate cements. These lithified structures are not usually observed at temperate settings. The present work is focused on the occurrence of a significant intertidal cementation in sand-gravel beaches formed among 43°N latitude coastline, close to the Nerbioi-Ibaizabal estuary (Bilbao, Bay of Biscay, North of Spain). Raman micro-spectroscopy combined with SEM-EDX analyses and petrographic descriptions have been applied for the determination of the cement generations and the cemented materials compositions of the beachrock outcrops. In general terms, the cements described were: Cement Generation 1 (CG 1, aragonite, high-magnesium calcite and silicate mixtures), Cement Generation 2 (CG 2, aragonite) and Cement Generation 3 (CG 3, mixtures of CaCO(3) polymorphs and iron oxides). The rest of the interstitial porosity of the rocks appeared either empty or filled with heterogeneous cemented mixtures of previously reworked compounds. The mineralogy, the regular distribution and the isopachous character of the carbonate cements together with the accurate cementation at advanced seaward bands propose a possible marine-phreatic context for the beachrock formation. However, the impure cements and the materials covering the interstitial porosity seem to be the result of both, the weathering actions consequences and the surface alterations of specific grains. Moreover, the presence of modern cemented materials (e.g. slag, bricks and pebbles) suggest a recent formation of the phenomenon.

Micro-Raman spectroscopic identification of natural mineral phases and their weathering products inside an abandoned zinc/lead mine

Mining activities provide a good source of minerals of different nature. On the one hand, the primary minerals for whose formation a geological time-scale is required. On the other hand, secondary minerals, formed from removed products after the earlier weathering and alteration states. These are characteristic of the local geology and the environment context that commonly appears due to the low chemical stability of their original primary minerals. This work shows how quickly the reactions promoting secondary minerals may have taken place, due to the fact that these were found in newly formed solid materials called efflorescences. To achieve this purpose, the sampling is crucial. It was carried out in such a way that tried to guarantee that the samples collected consisted in the very top soil matter (first 2 cm depth). Thus, unlike the deeper soil, the material analysed may have been newly formed due to the interactions that they had with the place weathering agents (i.e. air oxygen, humidity, and microbial activities). Raman spectroscopy has emerged as a good and fast non-destructive technique that provides molecular information of the local mineralogy without the need of any pre-treatment of the samples. At the same time, the work looked for information on the variety of non-stable lead and-or zinc containing minerals due to the possible health and environmental risks they convey. Among the different minerals identified, 16 were of primary nature while 23 may be classified as secondary minerals, probably formed in the last decades as the result of the extractive activities.

Initialization method for speech separation algorithms that work in the time-frequency domain

This article addresses the problem of the unsupervised separation of speech signals in realistic scenarios. An initialization procedure is proposed for independent component analysis (ICA) algorithms that work in the time-frequency domain and require the prewhitening of the observations. It is shown that the proposed method drastically reduces the permuted solutions in that domain and helps to reduce the execution time of the algorithms. Simulations confirm these advantages for several ICA instantaneous algorithms and the effectiveness of the proposed technique in emulated reverberant environments.

A surgical technique for the prevention of femoral lysis in cement total hip arthroplasty

Femoral bone lysis in total hip arthroplasty is thought to be primarily due to polyethylene or metal debris arising from the femoral or acetabular components. The debris appears to gradually seep into the cement/ bone interface, eventually generating the chemical reaction that produces lysis.We experimented with a surgical technique that attempts to construct a proximal bony barrier preventing migration of debris. Following the injection of the acrylic cement and the insertion of the femoral component, but prior to complete polymerization of the cement, bone chips are pressed over the cement, in contact with the viable femoral cortex. The bone chips become rigidly fixed; probably regain viability from the femoral cortex, and seal the proximal femur. In this manner, debris cannot travel into the femoral canal. Although we do not have anatomical evidence that a viable bony seal has formed the absence of lysis and bone/cement radiolucent lines over a period of time ranging from three to fourteen years suggests the permanent presence of a physiological barrier. Attempts to identify the permanency of the bony seal by means of CT scans proved inconclusive. Key words: total hips, lysis, femoral lysis, cortical graft.

Functional treatment of closed segmental fractures of the tibia

PURPOSE OF THE STUDY Segmental tibial fractures are commonly believed to be more difficult to manage, requiring surgical treatment. Our experience with forty-eight segmental tibial fractures suggests that these fractures, if closed and with shortening of an acceptable initial degree and a corrected deformity, may be successfully treated with functional braces. MATERIAL AND METHODS Forty-eight closed segmental fractures of the tibia that had initial shortening .12 mm and angular deformity manually corrected to .7 degrees were stabilized in an above-the-knee cast for a median time of 33 days and a mode of 15 days. They were subsequently stabilized in a functional brace that allowed unencumbered motion of all joints. All other segmental fractures outside the established parameters were managed by other methods. RESULTS All fractures healed at a median time of 15.3 weeks. The final shortening was 4.7 millimeters with a mode of 12 millimeters. The maximum shortening was 14 millimeters. Fractures healed with a medial-lateral (M.L) angular deformities ranging zero to 19 degrees, a median of 5.9 degrees and a mode of 3.4 degrees. CONCLUSION The relatively early introduction of weight bearing and the freedom of motion of all joints that the brace permits seem to result in motion at the fracture site, which in turn enhances osteogenesis. As we have previously documented, the initial shortening that closed tibial fractures experience does not increase with the physiological use of the extremity. The final shortening and angulation observed in most of the fractures should not be considered complications, simply inconsequential deviations from the normal. The same should apply to closed segmental fractures.

Analytical diagnosis methodology to evaluate nitrate impact on historical building materials

Nitrate salts have become of greater importance in the decay of materials from historical buildings due to changes in the environment. This work presents an analytical diagnosis methodology to evaluate the impact of nitrate salts in mortars and bricks, combining noninvasive and microdestructive analytical techniques together with chemometric and thermodynamic data analyses. The impact of nitrate salts cannot be well ascertained if other soluble salts are not taken into account. Therefore, the principal results from this work relate to nitrate salts but some results for other kinds of salts are included. Data from Raman microprobe spectroscopy and micro X-ray fluorescence (micro-XRF) are used to characterise the original composition and a first approximation of the nature of the decay compounds, mainly nitrates. The soluble salts are extracted and the anions and cations are quantified by means of ion chromatography with conductimetric detection for anions/cations and inductively coupled plasma mass spectrometry (ICP/MS) for cations. The values obtained allow two different data treatments to be applied. First, chemometric analysis is carried out to search for correlations among anions and cations. Second, thermodynamic modelling with the RUNSALT program is performed to search for environmental conditions of soluble salt formation. All the results are finally used to diagnose the impact of nitrates.

[Humeral diaphyseal fractures: functional bracing]

Functional bracing of humeral diaphyseal fractures was conceived after initial experiences with a similar method was used in the management of diaphyseal tibial fractures. Over the years, tibial functional bracing underwent major evolutionary changes, and found its indications basically limited to a smaller group of fractures, consisting of closed, axially unstable fractures that experience at the time of the injury an acceptable degree of shortening, and to transverse fracture that are appropriately reduced and rendered stable. On the other hand, functional bracing of diaphyseal humeral fractures has, maintained the initial indications, contraindications and methodology. This article describes the concept, indications and contraindications of functional bracing of humeral diaphyseal fractures and provides results of 620 fractures with complete follow-up. In 97.5% of the patients, the average healing time was 11.5 weeks. 16 patients (2.5%) required operative intervention because of a nonunion and 4 patients (<1 degrees) of the patient had a refracture after brace removal. Nerve function did not return in only one of the 67 patient who had radial nerve palsy.

Ethical considerations in the orthopaedic relationship with industry

Members of the medical profession spend a long time and financial resources acquiring the knowledge necessary for the discharge of their responsibilities; therefore, they should be appropriately compensated for the services they provide. However, it has become obvious, at least in the United States, that excessive emphasis on profit making is fostering the transformation of the medical profession into strictly a business. This transformation is spawning ethical infractions, which are becoming increasingly apparent.

[Haloperidol or droperidol with dexamethasone for antiemetic prophylaxis in laparoscopic cholecystectomy]

OBJECTIVES

To compare haloperidol to droperidol, both with dexamethasone, for antiemetic prophylaxis in elective laparoscopic cholecystectomy.

MATERIAL AND METHODS

Prospective, randomized double-blind trial enrolling 75 ASA 1-2 patients who received anesthesia with propofol and remifentanil. After induction, 8 mg of intravenous dexamethasone was administered. After surgery, depending on group assignment, patients received 10 microg x kg(-1) of intravenous haloperidol (n = 25), 10 microg x kg(-1) of droperidol (n = 25), or physiologic saline solution (n = 25). Outcomes recorded were episodes of nausea or vomiting in the postoperative period (first 6 hours and/or 6-24 hours), requirement for antiemetic agents, morphine consumption, pain assessed on a visual analog scale, level of sedation, and adverse effects.

RESULTS

Five patients in the haloperidol group, 6 in the droperidol group, and 13 in the control group experienced an episode of nausea or vomiting in the 24-hour postoperative period (P < .05 between the active treatment groups and the control group). One patient in the haloperidol group, 6 in the droperidol group, and 8 in the control group reported nausea in the first 6 hours (P < .05). Three patients in the haloperidol group, 1 in the droperidol group, and 8 in the control group reported nausea in the later postoperative period (6-24 hours) (P < .05, droperidol vs control). Three patients in the haloperidol group, 1 in the droperidol group, and 7 in the control group experienced late vomiting (P < .05, droperidol vs control).

CONCLUSIONS

Either haloperidol or droperidol in combination with dexamethasone is more effective than dexamethasone alone for antiemetic prophylaxis after laparoscopic cholecystectomy.

A radiographic review of 135 total hip Charnley arthroplasties followed between 15 and 35 years

The long-term radiologically interpreted results of low-friction Charnley hip arthroplasties have been previously suggested to be influenced by surgical details, such as orientation of the femoral component, degree of coverage of the plastic acetabulum and other features. We carefully analyzed the radiographs of 135 Charnley arthroplasties that had remained functional, had not been revised and had follow-ups between 15 and 35 years. Several common denominators were identified amongst these radiographs: 93.5% arthroplasties had 100% coverage of the acetabular component; 88% had acetabular inclination between 40-45 degrees ; 84.5% had a proximal/medial column of cement between 3 and 5 millimeters at the level of femoral head resection; 81% had a femoral canal/stem ratio more than 50%; and 84% had a column of cement that extended below the tip of the prosthesis. This study supports the importance of technical surgical details that enhance the chances of long-term survival of cemented total hip arthroplasties.

[Guidelines for the clinical management of neuropathic pain (II)]

INTRODUCTION

Up to 5% of the population suffers from neuropathic pain (NP). A bibliographical search in several databases revealed that, to date, there are no protocols to guide physicians who are not specialists in pain that enable them to treat NP and thus improve patients' quality of life.

AIMS

The aim of this study is to provide Spanish-speaking physicians who are not specialists in pain with a set of guidelines for the treatment of NP. A bibliographical search was performed in order to base the results and conclusions on the evidence-based medicine methodology.

DEVELOPMENT

First, we review the most effective clinical and paraclinical methods for diagnosing NP, and the LANSS pain scale is reported as the most appropriate method of clinically evaluating NP. The anatomical paths and the physiology of pain are then described and we review the molecular variables involved. Finally, we point out the current therapeutic options and propose an algorithm for the treatment of NP.

CONCLUSIONS

There is no specific set of guidelines for the treatment of NP. At the present time, the keystone of NP treatment consists in the use of antidepressant and anticonvulsive drugs. There is a need for further clinical trials to prove the effectiveness of using combined medication.

[Guidelines for the clinical management of neuropathic pain (I). Protocol]

AIMS

The aim of this study is to develop a set of guidelines for the clinical management of neuropathic pain (NP), a disorder suffered by up to 5% of the population, specifically for use by the Spanish-speaking community, in order to improve the quality of medical care and to standardise the treatments offered in medical centres.

DEVELOPMENT

The paper describes the methodology used to search for guidelines concerning the clinical management of NP in databases, written communications and other resources, and the results of this search are presented. The research group is split into three groups: anatomical-physiological, diagnosis and therapeutic approach, each of which defines the nature of the papers that used to design the protocol.

[Trihalomethanes in the drinking water of Carabobo State, Venezuela]

OBJECTIVE

Disinfection of water with chlorine in water treatment plants leads to the formation of trihalomethanes (THMs). These compounds are associated with adverse health effects. The aim of this study was to analyze THM concentrations in the water provided for human consumption in the two main water treatment systems of Carabobo State: the Alejo Zuloaga plant and the Pao-Cachinche reservoir, which form the Central Regional System I (CRS I), and the Lucio Baldo Soules plant and the Pao-La Balsa reservoir, which form the Central Regional System II (CRS II).

METHODS

We analyzed 144 water samples collected in 6 samplings carried out in 2000 and 2001. THM concentrations were determined by gas chromatography using the headspace technique. The concentrations of the following THMs were measured: chloroform (CHCl3), bromoform (CHBr3), chlorodibromomethane (CHBr2Cl) and bromodichloromethane (CHCl2Br).

RESULTS

The concentration of total THMs was between 47.84 g/l and 94.23 g/l. CHCl3 was the most commonly formed compound representing 83% of all THMs in the CRS I and 82% in the CRS II. The concentrations of total THMs in the CRS I, specifically in the Baja and San Diego networks, were significantly higher (p < 0.05) than permissible levels set by the American Environmental Protection Agency (80 g/l) for the sum of all four THMs.

CONCLUSIONS

The results show that in the area studied there is a risk of adverse health effects due to THMs in drinking water, especially in the Baja and San Diego networks.

Asymptotic dynamics of breathers in Fermi-Pasta-Ulam chains

We carry out a numerical study of the asymptotic dynamics of breathers in finite Fermi-Pasta-Ulam chains at zero and nonzero temperatures. While at zero temperature such breathers remain essentially stationary and decay extremely slowly over wide parameter ranges, thermal fluctuations tend to lead to breather motion and more rapid decay. In both cases the decay is essentially exponential over long time intervals.

Energy relaxation in nonlinear one-dimensional lattices

We study energy relaxation in thermalized one-dimensional nonlinear arrays of the Fermi-Pasta-Ulam type. The ends of the thermalized systems are placed in contact with a zero-temperature reservoir via damping forces. Harmonic arrays relax by sequential phonon decay into the cold reservoir, the lower-frequency modes relaxing first. The relaxation pathway for purely anharmonic arrays involves the degradation of higher-energy nonlinear modes into lower-energy ones. The lowest-energy modes are absorbed by the cold reservoir, but a small amount of energy is persistently left behind in the array in the form of almost stationary low-frequency localized modes. Arrays with interactions that contain both a harmonic and an anharmonic contribution exhibit behavior that involves the interplay of phonon modes and breather modes. At long times relaxation is extremely slow due to the spontaneous appearance and persistence of energetic high-frequency stationary breathers. Breather behavior is further ascertained by explicitly injecting a localized excitation into the thermalized arrays and observing the relaxation behavior.

Thermal resonance in signal transmission

We use temperature tuning to control signal propagation in simple one-dimensional arrays of masses connected by hard anharmonic springs and with no local potentials. In our numerical model a sustained signal is applied at one site of a chain immersed in a thermal environment and the signal-to-noise ratio is measured at each oscillator. We show that raising the temperature can lead to enhanced signal propagation along the chain, resulting in thermal resonance effects akin to the resonance observed in arrays of bistable systems.

Characteristics of degeneration in an unstable knee with a coronal surface step-off

To investigate the effect of instability on the remodelling of a minor articular surface offset, we created a 0.5 mm coronal step-off of the medial femoral condyle in 12 New Zealand white rabbits and transected the anterior cruciate ligament (ACL). A control group of 12 rabbits had only ACL resection and the opposite knee was used as the non-operated control. The osteoarthritic changes at 6, 12 and 24 weeks after surgery were evaluated histologically. In addition, changes in the immunological detection of 3-B-3(-) and 7-D-4 chondroitin-6-sulphate epitopes were determined because of the previous association of such changes with repair of cartilage and early osteoarthritis. In the instability/step-off group there was rapidly progressing focal degeneration of cartilage on the high side of the defect, not seen in previous step-off studies in stable knees. The rest of the femoral condyles and the tibial plateaux of the instability/step-off group had moderate osteoarthritis similar to that of the instability group. 3-B-3(-) was detectable in the early and the intermediate stages of osteoarthritis but no staining was seen in the severely damaged cartilage zones. Immunoreactivity with 7-D-4 increased as degeneration progressed.

Characteristics of degeneration in an unstable knee with a coronal surface step-off

To investigate the effect of instability on the remodelling of a minor articular surface offset, we created a 0.5 mm coronal step-off of the medial femoral condyle in 12 New Zealand white rabbits and transected the anterior cruciate ligament (ACL). A control group of 12 rabbits had only ACL resection and the opposite knee was used as the non-operated control. The osteoarthritic changes at 6, 12 and 24 weeks after surgery were evaluated histologically. In addition, changes in the immunological detection of 3-B-3(-) and 7-D-4 chondroitin-6-sulphate epitopes were determined because of the previous association of such changes with repair of cartilage and early osteoarthritis.

In the instability/step-off group there was rapidly progressing focal degeneration of cartilage on the high side of the defect, not seen in previous step-off studies in stable knees. The rest of the femoral condyles and the tibial plateaux of the instability/step-off group had moderate osteoarthritis similar to that of the instability group. 3-B-3(-) was detectable in the early and the intermediate stages of osteoarthritis but no staining was seen in the severely damaged cartilage zones. Immunoreactivity with 7-D-4 increased as degeneration progressed.

Our findings have shown that even a minor surface offset may induce rapid degeneration of cartilage when the stability of the knee is compromised.