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The current COVID-19 pandemic continues for over eleven months. Several nutritional and behavioural aspects have been associated with an increased inflammatory state, or oxidative stress, which could negatively affect the course of COVID-19. As research has shown, metabolic diseases, including obesity, or type 2 diabetes mellitus (T2DM), in which proper diet is especially important, increase the risk of the COVID-19 infection and can exacerbate its course. This should be taken into account particularly in the areas with high prevalence of obesity and T2DM, such as the Western countries. In our paper, we have briefly summarised the harmful and beneficial nutritional and behavioural aspects, essential during the COVID-19 pandemic, which are present in particular among patients suffering from obesity and T2DM.

Reduced physical activity (PA), smoking, and coffee and alcohol drinking constitute risk factors of osteoporosis in patients with inflammatory bowel disease (IBD). The aim of the study was to measure the bone mineral density (BMD) and frequency of osteopenia and osteoporosis in patients with IBD and their correlation with PA, smoking, coffee, and alcohol. The study group consisted of 208 patients with IBD-103 with Crohn’s disease (CD), 105 suffering from ulcerative colitis (UC). Densitometric measurements were performed using the DXA. All patients completed a questionnaire concerning PA, smoking, and coffee and alcohol consumption. The prevalence of osteopenia and osteoporosis (L2–L4) in the IBD group was 48.1%; in the CD group, it amounted to 48.6%, and in the UC group, the prevalence was equal to 33.3%. Patients with CD who were diagnosed with osteopenia and osteoporosis demonstrated reduced PA compared to patients with a normal BMD who exercised regularly (p = 0.0335). A similar observation was made in the group of women with IBD. Women with a normal BMD exercised significantly more often than women suffering from osteopenia and osteoporosis (p = 0.0146). However, no differences in BMD were observed with regard to coffee use, alcohol consumption, or smoking. Thus, since the incidence of osteoporosis in IBD patients is high, it may be dependent on PA.

Scientific research on heart rate variability (HRV) biofeedback is burdened by certain methodological issues, such as lack of consistent training quality and fidelity assessment or control conditions that would mimic the intervention. In the present study, a novel sham HRV-biofeedback training was proposed as a credible control condition, indistinguishable from the real training. The Yield Efficiency of Training Index (YETI), a quantitative measure based on the spectral distribution of heart rate during training, was suggested for training quality assessment. A training fidelity criterion derived from a two-step classification process based on the average YETI index and its standard deviation (YETISD) was suggested. We divided 57 young, healthy volunteers into two groups, each subjected to 20 sessions of either real or sham HRV-biofeedback. Five standard HRV measures (standard deviation of the NN (SDNN), root mean square of the standard deviation of the NN (RMSSD), total power, low-frequency (LF), and high-frequency (HF) power) collected at baseline, after 10 and 20 sessions were subjected to analysis of variance. Application of a training fidelity criterion improved sample homogeneity, resulting in a substantial gain in effect sizes of the group and training interactions for all considered HRV indices. Application of methodological amendments, including proper control conditions (such as sham training) and quantitative assessment of training quality and fidelity, substantially improves the analysis of training effects. Although presented on the example of HRV-biofeedback, this approach should similarly benefit other behavioral training procedures that interact with any of the many psychophysiological mechanisms in the human body.

Osteoporosis affects women twice as often as men. Additionally, it is estimated that 0.3 million and 1.7 million people have hip fractures in the USA and Europe, respectively. Having a proper peak bone mass and keeping it as long as possible is especially important for osteoporosis prevention. One of the most important calcium sources is milk and dairy products. Breast milk is the best infant food, but milk should not be avoided later in life to prevent losing bone mass. On the other hand, more and more people limit their milk consumption and consume other dairy or non-dairy products. For example, they are usually replaced with plant beverages, which should be consumed carefully in several age groups. Additionally, an important element of milk and dairy products, as well as plant beverages, are probiotics and prebiotics, which may modulate bone turnover. Dietary recommendations focused on milk, and dairy products are an important element for the prevention of osteoporosis.

Diabetes mellitus is a metabolic and systematic disorder that requires individualized therapy. The disease leads to various consequences, resulting in the destruction of tissues and organs. The aforementioned outcomes also include bone mineral disorders, caused by medications as well as diet therapy and physical activity. Some drugs may have a beneficial effect on both bone mineral density and the risk of fractures. Nevertheless, the impact of other medications remains unknown. Focusing on pharmacotherapy in diabetes may prevent bone mineral disorders and influence both the treatment and quality of life in patients suffering from diabetes mellitus. On the other hand, anti-osteoporosis drugs, such as antiresorptive or anabolic drugs, as well as drugs with a mixed mechanism of action, may affect carbohydrate metabolism, particularly in patients with diabetes. Therefore, the treatment of diabetes as well as osteoporosis prevention are vital for this group of patients.

Infertility is an increasing problem that affects couples attempting pregnancy. A growing body of evidence points to a link between diet and female fertility. In fact, data show that a diet high in trans fats, refined carbohydrates, and added sugars can negatively affect fertility. Conversely, a diet based on the Mediterranean dietary patterns, i.e., rich in dietary fiber, omega-3 (ɷ-3) fatty acids, plant-based protein, and vitamins and minerals, has a positive impact on female fertility. An unhealthy diet can disrupt microbiota composition, and it is worth investigating whether the composition of the gut microbiota correlates with the frequency of infertility. There is a lack of evidence to exclude gluten from the diet of every woman trying to become pregnant in the absence of celiac disease. Furthermore, there are no data concerning adverse effects of alcohol on female fertility, and caffeine consumption in the recommended amounts also does not seem to affect fertility. On the other hand, phytoestrogens presumably have a positive influence on female fertility. Nevertheless, there are many unanswered questions with regard to supplementation in order to enhance fertility. It has been established that women of childbearing age should supplement folic acid. Moreover, most people experience vitamin D and iodine deficiency; thus, it is vital to control their blood concentrations and consider supplementation if necessary. Therefore, since diet and lifestyle seem to be significant factors influencing fertility, it is valid to expand knowledge in this area., Statement of Significance: This manuscript provides the current knowledge and a holistic view of diet and supplementation with regard to female fertility.

Iodine deficiency is a global issue and affects around 2 billion people worldwide, with pregnant women as a high-risk group. Iodine-deficiency prevention began in the 20th century and started with global salt iodination programmes, which aimed to improve the iodine intake status globally. Although it resulted in the effective eradication of the endemic goitre, it seems that salt iodination did not resolve all the issues. Currently, it is recommended to limit the consumption of salt, which is the main source of iodine, as a preventive measure of non-communicable diseases, such as hypertension or cancer the prevalence of which is increasing. In spite of the fact that there are other sources of iodine, such as fish, seafood, dairy products, water, and vegetables, the high consumption of processed food with a high content of unionised salt, alternative diets or limited salt intake can still lead to iodine deficiency. Thus, iodine deficiency remains a relevant issue, with new, preventive solutions necessary. However, it appears that there is no diet which would fully cover the iodine requirements, and iodine food supplementation is still required.

Osteoporosis is one of the most common extraintestinal complications among patients suffering from inflammatory bowel diseases. The role of vitamin D and calcium in the prevention of a decreased bone mineral density is well known, although other nutrients, including micronutrients, are also of extreme importance. Despite the fact that zinc, copper, selenium, iron, cadmium, silicon and fluorine have not been frequently discussed with regard to the prevention of osteoporosis, it is possible that a deficiency or excess of the abovementioned elements may affect bone mineralization. Additionally, the risk of malnutrition, which is common in patients with ulcerative colitis or Crohn’s disease, as well as the composition of gut microbiota, may be associated with micronutrients status.

Cigarette smoking constitutes one of the most important modifiable factors of osteoporosis, as well as contributes to an early death, tumors, and numerous chronic diseases. The group with an increased risk of a lower bone mineral density are patients suffering from inflammatory bowel diseases. In fact, tobacco smoke, which contains more than 7000 chemical compounds, affects bone mineral density (BMD) both directly and indirectly, as it has an impact on the RANK-RANKL-OPG pathway, intestinal microbiota composition, and calcium–phosphate balance. Constant cigarette use interferes with the production of protective mucus and inhibits the repair processes in the intestinal mucus. Nicotine as well as the other compounds of the cigarette smoke are important risk factors of the inflammatory bowel disease and osteoporosis. Additionally, cigarette smoking may decrease BMD in the IBD patients. Interestingly, it affects patients with Crohn’s disease and ulcerative colitis in different ways—on the one hand it protects against ulcerative colitis, whereas on the other it increases the risk of Crohn’s disease development. Nevertheless, all patients should be encouraged to cease smoking in order to decrease the risk of developing other disorders.

Sarcopenia is a disorder characterized by a loss of muscle mass which leads to the reduction of muscle strength and a decrease in the quality and quantity of muscle. It was previously thought that sarcopenia was specific to ageing. However, sarcopenia may affect patients suffering from chronic diseases throughout their entire lives. A decreased mass of muscle and bone is common among patients with inflammatory bowel disease (IBD). Since sarcopenia and osteoporosis are closely linked, they should be diagnosed as mutual consequences of IBD. Additionally, multidirectional treatment of sarcopenia and osteoporosis including nutrition, physical activity, and pharmacotherapy should include both disorders, referred to as osteosarcopenia.

Patients suffering from Crohn’s disease and ulcerative colitis are at higher risk of osteoporosis due to lower bone mineral density. Risk factors of osteoporosis are divided into unmodifiable, namely, age, gender, genetic factors, as well as modifiable, including diet, level of physical activity, and the use of stimulants. Coffee and tea contain numerous compounds affecting bone metabolism. Certain substances such as antioxidants may protect bones; other substances may increase bone resorption. Nevertheless, the influence of coffee and tea on the development and course of inflammatory bowel diseases is contradictory.

Although many preventive and treatment approaches have been proposed, cardiovascular disease (CVD) remains one of the leading causes of deaths worldwide. Current epidemiological data require the specification of new causative factors, as well as the development of improved diagnostic tools to provide better cardiovascular management. Excessive accumulation of adipose tissue among patients suffering from obesity not only constitutes one of the main risk factors of CVD development but also alters adipokines. Increased attention is devoted to bioactive adipokines, which are also produced by the adipose tissue. The retinol-binding protein 4 (RBP4) has been associated with numerous CVDs and is presumably associated with an increased cardiovascular risk. With this in mind, exploring the role of RBP4, particularly among patients with obesity, could be a promising direction and could lead to better CVD prevention and management in this patient group.

Although many preventive and treatment approaches have been proposed, cardiovascular disease (CVD) remains one of the leading causes of deaths worldwide. Current epidemiological data require the specification of new causative factors, as well as the development of improved diagnostic tools to provide better cardiovascular management. Excessive accumulation of adipose tissue among patients suffering from obesity not only constitutes one of the main risk factors of CVD development but also alters adipokines. Increased attention is devoted to bioactive adipokines, which are also produced by the adipose tissue. The retinol-binding protein 4 (RBP4) has been associated with numerous CVDs and is presumably associated with an increased cardiovascular risk. With this in mind, exploring the role of RBP4, particularly among patients with obesity, could be a promising direction and could lead to better CVD prevention and management in this patient group. In our review, we summarized the current knowledge about RBP4 and its association with essential aspects of cardiovascular disease—lipid profile, intima-media thickness, atherosclerotic process, and diet. We also discussed the RBP4 gene polymorphisms essential from a cardiovascular perspective., info:eu-repo/semantics/publishedVersion

Recent research studies have shown that vitamin C (ascorbic acid) may affect bone mineral density and that a deficiency of ascorbic acid leads to the development of osteoporosis. Patients suffering from an inflammatory bowel disease are at a risk of low bone mineral density. It is vital to notice that patients with Crohn’s disease and ulcerative colitis also are at risk of vitamin C deficiency which is due to factors such as reduced consumption of fresh vegetables and fruits, i.e., the main sources of ascorbic acid. Additionally, some patients follow diets which may provide an insufficient amount of vitamin C. Moreover, serum vitamin C level also is dependent on genetic factors, such as SLC23A1 and SLC23A2 genes, encoding sodium-dependent vitamin C transporters and GSTM1, GSTP1 and GSTT1 genes which encode glutathione S-transferases. Furthermore, ascorbic acid may modify the composition of gut microbiota which plays a role in the pathogenesis of an inflammatory bowel disease.

Summary COVID‐19 crisis has lasted since the late 2019 to the present day. The severity of the disease is positively correlated with several factors, such as age and coexisting diseases. Furthermore, obesity is increasingly considered as a yet another risk factor, particularly, because it has been observed that people suffering from excessive body weight may experience a more severe course of COVID‐19 infection. On the basis of current research, in our nonsystematic review, we have investigated the extent to which obesity can affect the SARS‐CoV‐2 course and identify the potential mechanisms of the disease. We have also described the role of proper nutrition, physical activity and other aspects relevant to the management of obesity.

The chronic character of inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis, results in various complications. One of them is osteoporosis, manifested by low bone mineral density, which leads to an increased risk of fractures. The aetiology of low bone mineral density is multifactorial and includes both diet and nutritional status.Calcium is the most often discussed minerals with regard to bone mineral density. Moreover, phosphorus; magnesium and sodium are also involved in the formation of bone mass. Patients suffering from inflammatory bowel diseases frequently consume inadequate amounts of the aforementioned minerals or their absorption is disturbed, resulting innutritional deficiency and an increased risk of osteoporosis.&nbsp

Folic acid, referred to as vitamin B9, is a water-soluble substance, which participates in the synthesis of nucleic acids, amino acids, and proteins. Similarly to B12 and B6, vitamin B9 is involved in the metabolism of homocysteine, which is associated with the MTHFR gene. The human body is not able to synthesize folic acid; thus, it must be supplemented with diet. The most common consequence of folic acid deficiency is anemia; however, some studies have also demonstrated the correlation between low bone mineral density, hyperhomocysteinemia, and folic acid deficiency. Patients with inflammatory bowel disease (IBD) frequently suffer from malabsorption and avoid certain products, such as fresh fruits and vegetables, which constitute the main sources of vitamin B9. Additionally, the use of sulfasalazine by patients may result in folic acid deficiency. Therefore, IBD patients present a higher risk of folic acid deficiency and require particular supervision with regard to anemia and osteoporosis prevention, which are common consequences of IBD.

Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, is characterized by chronic inflammation of the gastrointestinal tract. IBD has been associated with numerous symptoms and complications, with the most common being iron deficiency anemia (IDA). Iron deficiency in IBD is caused by inadequate intake, malabsorption (including duodenal involvement and surgical removal), and chronic blood loss by mucosal ulcerations. Therefore, an appropriate diet should be enforced. Iron deficiency and iron supplementation have been associated with alterations to gut microbiota. IBD-associated anemia, in particular iron deficiency anemia, is associated with a significant decrease in quality of life and with clinical symptoms such as chronic fatigue, headaches and dizziness, reduced exercise tolerance, pale skin, nails, conjunctiva, and fainting. However, despite these numerous adverse symptoms, IDA remains undertreated. The European Crohn’s and Colitis Organisation (ECCO) guidelines state that patients should be monitored for anemia. Adequate treatment, whether oral or intravenous, should be implemented while taking into consideration C-reactive protein values (CRP), hemoglobin levels, and therapeutic response. It should be stressed that every case of anemia in IBD patients should be treated. Intravenous iron formulations, which are more superior compared to the oral form, should be used. There is a need to increase awareness and implementation of international guidelines on iron supplementation in patients with IBD.

Lactose intolerance affects 33% to 75% of the world population and may be associated with various genetic factors. Lactose in the diet can be found in milk and dairy products, which simultaneously constitute the primary sources of calcium. Gut microbiota also influences lactose tolerance. Patients with lactose intolerance often stop consuming milk and dairy products, which may lead to calcium and vitamin deficiency and osteoporosis. Insufficient production of lactase also occurs in patients with diseases of the gastrointestinal tract, such as inflammatory bowel diseases. Moreover, Crohn's disease and ulcerative colitis are risk factors for osteoporosis, and the intake of the proper amount of calcium is an essential element in preventing the decrease of bone mineral density. Diet may prevent the development of osteoporosis, thus, educating patients regarding proper diet should constitute a part of the treatment and prevention process. Patients should consume low-lactose, or lactose-free milk and bacterially fermented dairy products. Additionally, plant milk supplemented by calcium and vitamin D, mineral water with calcium, and certain vegetables also may be good sources of calcium.

More research has recently focused on the role of the gut microbiota in the development or course of numerous diseases, including non-communicable diseases. As obesity remains prevalent, the question arises as to what microbial changes are associated with increased obesity prevalence and what kind of prevention and treatment approaches it could provide. Moreover, the influence of the gut-brain axis on obesity is also crucial, since it can affect metabolism and food intake. The quantitative and qualitative changes in the microbiota composition are called dysbiosis; however, in view of the current knowledge, it is difficult to conclude which microbial imbalances are adverse or beneficial. Increased numbers of pathological microorganisms were observed among patients with obesity and comorbidities associated with it, such as diabetes, cardiovascular disease, and insulin resistance. Our review provides current knowledge regarding changes in the intestinal microbiota associated with obesity and obesity-associated comorbidities. Nevertheless, given that dietary patterns and nutrients are two of the factors affecting the intestinal microbiota, we also discuss the role of different dietary approaches, vitamins, and minerals in the shaping of the intestinal microbiota.

The chronic character of inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis, results in various complications. One of them is osteoporosis, manifested by low bone mineral density, which leads to an increased risk of fractures. The aetiology of low bone mineral density is multifactorial and includes both diet and nutritional status. Calcium and vitamin D are the most often discussed nutrients with regard to bone mineral density. Moreover, vitamins A, K, C, B12; folic acid; calcium; phosphorus; magnesium; sodium; zinc; copper; and selenium are also involved in the formation of bone mass. Patients suffering from inflammatory bowel diseases frequently consume inadequate amounts of the aforementioned minerals and vitamins or their absorption is disturbed, resulting innutritional deficiency and an increased risk of osteoporosis. Thus, nutritional guidelines for inflammatory bowel disease patients should comprise information concerning the prevention of osteoporosis.

Początki państwowej administracji i gospodarki leśnej sięgają VIII-IX wieku. Wraz z występującą w tym czasie wielką wędrówką ludów nastąpił znaczny wyrąb lasu na potrzeby ówczesnego osadnictwa. Kolejna nadmierna eksploatacja lasów w Europie miała miejsce w XIII-XV wieku i była wynikiem intensywnego rozwoju miast, rzemiosła, transportu, w tym drewnochłonnej floty oraz górnictwa, hutnictwa żelaza i szkła. Rosnące z roku na rok zużycie drewna doprowadziło do jego nadmiernego pozyskania i ubytku zasobności drzewostanów. Odzwierciedleniem tej sytuacji było zjawisko „głodu drewna”. Kolejny okres intensywnego użytkowania tego surowca nazwany został „epoką drewna” i trwał od XV do XIX wieku. Pierwszą usystematyzowaną teorią zajmującą się ekonomicznymi problemami gospodarki leśnej była kameralistyka (niem. Kammer − m.in. izba skarbowa), której początki rozwoju sięgają przełomu XVII i XVIII wieku. Jej nazwa pochodzi od byłych kamer rządowych. Kameralistów traktowano jako niemieckich przedstawicieli merkantylizmu i zaliczano do przedstawicieli liberalizmu gospodarczego. Wzrost zainteresowania leśnictwem ze strony kameralistów doprowadził do szybkiego rozwoju przemysłu leśnego. Za prekursora tych działań uważany jest W.G. Moser, autor dzieła „Zasady ekonomiki leśnictwa” (1757), według którego głównym celem leśnictwa jest zaspokojenie zapotrzebowania przemysłu na drewno1. Z obawy o brak dostatecznych dostaw drewna Moser formułuje „zasadę ciągłości użytkowania”, która w późniejszym okresie została określona jako „zasada ciągłości produkcji leśnej” i stała się kamieniem węgielnym rozwoju gospodarstwa leśnego. Na przełomie XVIII i XIX wieku gospodarkę leśną zaczyna kształtować liberalna ekonomia A. Smitha, wraz z jej wolnym rynkiem. Podstawowe jej zasady, w tym dotyczące zwłaszcza równowagi ekonomicznej gospodarstwa leśnego, znalazły swoje miejsce pod skrzydłami statyki leśnej. Jej wybitny przedstawiciel, G. Heyer (1865), określił ją natomiast jako rachunek oceny rentowności metod gospodarowania w leśnictwie2. To właśnie pod wpływem statyki żądano od leśnictwa dostarczenia „możliwie dużego dochodu pieniężnego” (zysku, renty), a nie największej masy drewna. Rozległość zainteresowania statyki leśnej doprowadziła do sformułowania dwóch podstawowych teorii ekonomiki leśnictwa określanych jako: ■ teoria renty gruntowej oraz ■ teoria renty leśnej. Pierwsza z wymienionych teorii główną uwagę koncentrowała na gruntach leśnych, które traktowała jako kapitał trwały gospodarstwa leśnego. Natomiast drzewostan był uznawany za kapitał (środek) obrotowy. Pojęcie gospodarności sprowadzało się do uzyskania maksymalnej rentowności mierzonej stosunkiem czystego (netto) dochodu (renty) do wartości kapitału trwałego gruntu leśnego. W obliczeniach tych statyka leśna korzystała w szerokim zakresie i nadal korzysta z rachunków procentu składanego. Wymieniona teoria renty leśnej nazywana również szkołą renty leśnej lub nauką o czystym dochodzie z lasu, dążyła do maksymalizacji czystego dochodu z lasu obejmującego przede wszystkim grunt i drzewostan. Wiek, w którym ten postulat był spełniony, określono wiekiem najwyższej renty leśnej lub wiekiem rębności. Teoretycznie wiek ten jest znacznie wyższy niż wiek rębności najwyższej renty gruntowej. Dla gorszych siedlisk różnice te wynosiły 40-60 i więcej lat, dla najlepszych zaś siedlisk około 30-40 lat. Wiek najwyższej rentowności był na ogół wyższy od wieku dojrzałości finansowej, a niższy od wieku najwyższej renty leśnej. W Europie Środkowej wiek rębności waha się od 60 do 250 lat (Möhring 2004)3. Długi okres produkcji leśnej na ogół dominuje w ekstensywnych metodach produkcji. Natomiast aktywne metody zagospodarowania lasu i jego pielęgnacji obejmują rocznie zaledwie od 10 do 20% ogółu powierzchni gospodarstwa leśnego. Oznacza to, że przeciętny cykl zabiegów hodowlano-ochronnych powtarzany jest co 5−10 lat. Przedstawiona krótka charakterystyka teorii statyki leśnej wskazuje na wysoki stopień jej operacjonizmu wynikający z empirycznych (fizycznych) metod pomiaru elementów rachunku renty gruntowej i renty leśnej. Pod tym względem rachunek rent wyraźnie różni się od pozostałych rachunków ekonomicznych gospodarki leśnej. Od XIX wieku, zwłaszcza od ukształtowania przez M. Faustmanna finansowego nurtu gospodarki leśnej, jej cele zostały zdominowane przez teorię czystego dochodu z gruntu, nazywanego również teorią renty gruntowej. Upowszechniła się ona po długim, przeszło 100-letnim sporze między nauką o czystym dochodzie z gruntu a nauką o czystym dochodzie z lasu. Obok teorii renty gruntowej i renty leśnej w XIX w. w leśnictwie zachodniej i środkowej części Europy ukształtowały się dwa nurty, które odbiegają pod względem celów i metod od teorii renty gruntowej i leśnej. Nurty te są bliżej określone w poniższych tytułach: ■ nurt ekologiczno-środowiskowy oraz ■ nurt ekonomiczno-finansowy. W Europie Środkowej i Zachodniej dominuje nurt ekologiczno-środowiskowy. Jego cechą są drzewostany wielogatunkowe o długim cyklu produkcji leśnej, słabych trzebieżach, niskim oprocentowaniu i małych odsetkach oraz o znacznym podporządkowaniu gospodarki leśnej czystemu dochodowi z lasu. Kolejną cechą nurtu ekologicznego jest duży przyrost miąższości, ale także znaczny udział drzewostanów starszych klas wieku w strukturach lasu oraz ich odporność na działanie biotycznych i abiotycznych zakłóceń, dywersyfikacja dochodów i ukierunkowanie celu gospodarki leśnej na maksymalizację czystego dochodu z lasu. Przeciwieństwem powyższego nurtu jest ekonomiczno-finansowa orientacja gospodarki leśnej ukierunkowana na krótkie wieki rębności, intensywne trzebieże, drzewostany jednogatunkowe, duże oprocentowanie i najwyższy czysty dochód z gruntu. Jednym słowem gospodarstwo o orientacji finansowo-ekonomicznej dąży do krótkich wieków rębności, zrębowego użytkowania oraz wysokich procentów. Tymczasem nurt ekologiczny preferuje długie wieki rębności i niskie oprocentowanie. Podsumowując należy zauważyć, że ukształtowane w przeszłości dwa nurty gospodarki leśnej dominują nadal w leśnictwie europejskim z różnym nasileniem poszczególnych metod. Ekonomiczne podejście do podejmowania decyzji inwestycyjnych w leśnych warunkach niepewności ryzyka zostało wsparte przez rozwijaną od roku 1950 teorię portfela, najpierw w Stanach Zjednoczonych Ameryki, później w innych krajach, w tym zwłaszcza w Skandynawii i Niemczech. Z jednej strony preferowane są więc drzewostany o dużej odporności na ryzyko, ale mniejszej produkcyjności, z drugiej zaś drzewostany o znacznej produkcyjności, ale małej odporności na ryzyko. Optymalna kombinacja drzewostanów reprezentujących te dwie cechy w jednym z przykładowych leśnictw w Niemczech miała następujący skład gatunkowy: 70% Św, 30% Bk (Knoke 2004)4. Natomiast w Szwecji optymalna struktura gatunkowa drzewostanów wynosi: 49% Św oraz 51% So (Svensson 2000)5. Do szczególnie ważnych i szeroko stosowanych obecnie rozwiązań należy dywersyfikacja, która polega na zmniejszeniu sumarycznego ryzyka przy jednakowym dochodzie lub zwiększeniu dochodu przy jednakowym ryzyku. Wynika stąd, że teoria portfela obejmuje kombinację dwóch dóbr, na przykład drzewosfery jodłowe i bukowe. Metodyczne aspekty omawianej teorii portfela są dziełem H. Markowitza (1952), który został za nie uhonorowany nagrodą Nobla w 1990 r.6 Natomiast pionierskiezastosowania teorii portfela w praktyce leśnictwa USA są wynikiem intensywnych prac W.L. Millsa i W.L. Hoovera (1982) nad rozwojem inwestycji leśnych7. Odnotowany w kolejnych dekadach dalszy rozwój teorii portfela dotyczy przede wszystkim leśnictwa Skandynawii oraz Niemiec. Zgodnie z teorią portfela jego istota polega na optymalnej kombinacji dwóch dóbr, na przykład dwóch gatunków w drzewostanie (Kruschwitz 2007)8. Powszechnym przykładem takiej kombinacji jest Las Tharandzki oraz sporządzone dla niego optymalne kombinacje struktury gatunkowej drzewostanów. Taki sam atrybut odnosi się również do innych kategorii dóbr. Dziewiąta edycja wspólnego przedsięwzięcia Instytutu Badawczego Leśnictwa i Dyrekcji Generalnej Lasów Państwowych, jakim jest Zimowa Szkoła Leśna, dotyczyła właśnie wyzwań stojących przed współczesnym leśnictwem, zarówno tych wynikających ze zmian globalnych środowiska, jak i ekonomiczno-społecznych aspektów leśnictwa. W IX Sesji uczestniczyło 259 osób. Poza autorami krajowymi, reprezentującymi Ministerstwo Środowiska, Dyrekcję Generalną Lasów Państwowych oraz jednostki organizacyjne Lasów Państwowych, uczelnie i instytuty naukowe, referaty wygłosili naukowcy i leśnicy praktycy z zagranicy. ----------------------------------------- 1 Moser W.G. 1757. Grundsätze der Forstökonomie. Bd. 1-2. Frankfurt a/M. 2 Heyer G. 1865. Anleitung zur Waldwertrechnung. Leipzig. 3 Möhring B. 2004. Betriebswirtschaftliche Analyse des Waldumbaus. Forst und Holz, 59, 11: 523-530. 4 Knoke T. 2004. Die Begründung von Mischbeständen: eine Möglichkeiten zur Minderung von Risiko? Kongressbericht des Deutschen Forstvereins zur Tagung 2003 in Mainz: 344-355. 5 Svensson L. 2000. Open-economy inflation targeting. Journal of International Economics, 50: 155–183. 6 Markowitz H. 1952. Portfolio Selection. The Journal of Finance, 7, 1: 77–91. 7 Mills W.L., Hoover W.L. 1982. Investment in forest land: aspects of risk and diversification. Land Economics, 58: 33-51. 8 Kruschwitz L. 2007. Finansowanie i inwestycje. CeDeWu, Warszawa.

The first part of this chapter presents Resource-Constrained Project Scheduling Problem (RCPSP) formulations and notations (Sect. 4.1). It also provides an overview of the best methods proposed so far for solving this problem, including a set of relevant bibliographic references in Sect. 4.2.

Project scheduling problems (PSP) could be defined as allocating scarce resources over time to perform a given set of activities.

The first part of this chapter presents Multi-mode Resource-Constrained Project Scheduling Problem (MRCPSP) formulations and notations (Sect. 5.1).

In this paper the dynamic interaction strategy based on the Population Learning Algorithm (PLA) for the A-Team solving the Resource-Constrained Project Scheduling Problem (RCPSP) is proposed and experimentally validated. The RCPSP belongs to the NP-hard problem class. To solve this problem a team of asynchronous agents (A-Team) has been implemented using multiagent system. An A-Team is the set of objects including multiple agents and the common memory which through interactions produce solutions of optimization problems. These interactions are usually managed by some static strategy. In this paper the dynamic learning strategy based on PLA is suggested. The proposed strategy supervises interactions between optimization agents and the common memory. To validate the proposed approach computational experiment has been carried out.

In this chapter the idea of Asynchronous Team (A-Team) is extended and used to solve one of the hard combinatorial optimization problems. The Team of A-Teams (TA-Teams) architecture for solving the Resource-Constrained Project Scheduling Problem (RCPSP) is proposed and experimentally validated. The RCPSP belongs to the Non-deterministic Polynomial hard (NP-hard) problem class. To solve this problem a team of parallel cooperating A-Teams is proposed. Such terms consist of asynchronous agents, implemented using JADE based A-Team (JABAT) multiagent system. Java Agent Development Framework (JADE) is a popular framework dedicated to implement agent based systems. In the proposed TA-Teams from one to four A-Teams and four kinds of optimization agent have been implemented and used. Each optimization agent represents an optimization algorithm. The proposed optimization algorithms are based on several known metaheuristics, such as a simple local search, tabu search and path relinking as well as the crossover and special heuristics dedicated to solving the RCPSP. Computational experiment involved evaluation of the proposed approach in respect of the different parameters settings controlling the working and migration strategies used in the suggested TA-Teams approach.

The paper proposes applying the population-learning algorithm to solving both the single-mode and the multi-mode resource-constrained pro-ject scheduling problems (denoted as RCPSP and MRCPSP, respectively) with makespan minimization as an objective function. The paper contains problem formulation and a description of the proposed implementation of the population learning algorithm (PLA). To validate the approach a computational experiment has been carried out. It has involved 1440 instances of the RCPSP and 3842 instances of the MRCPSP obtained from the available benchmark data sets. Results of the experiment show that the proposed PLA implementation is an effective tool for solving the resource-constrained project scheduling problems. In case of the RCPSP instances the algorithm in a single run limited to 50000 solutions generated has produced results close to the results of the best known algorithms as compared with average deviation from critical path. In case of the MRCPSP instances the proposed algorithm in a single run has produced solutions with mean relative error value below 1.6% as compared with optimal or best known solutions for benchmark problems.

The paper considers a problem of scheduling multiprocessor tasks with correlated failures to maximize schedule reliability under time constraints. Since the problem is NP-hard the approximation algorithms based on a population learning algorithm are proposed.

There exist numerous situations where performing repeatedly a task or executing a number of its multiple redundant variants, increases chances for a successful task completion. The paper investigates the problem Pl|r i,m−v|R (see [1] for details), of scheduling multiple-variant (m−v) tasks with a view to maximizing schedule reliability. Variants of each task are independent and can be run in parallel or in sequence.