Rational Asset Price Bubbles

The solution to a linear model in which supply and/or demand depends on rational expectations of future prices can involve three parts, which we denote as the fundamental component, the deterministic bubble component, and the stochastic bubble component. This paper explores the properties of these solution components, emphasizing the distinction between deterministic bubbles and stochastic bubbles, for a model of inflation and for a model of the evolution of price and quantity in the market fora storable commodity, such as gold. The analysis focuses on stochastic bubbles as a possibility peculiarly associated with models that involve rational expectations. In both the inflation model and the gold model, although the analysis points to no compelling reason to rule out rational stochastic bubbles apriori, conventional behavioral assumptions imply that anyrational bubbles that arise, whether deterministic or stochastic,are explosive. The paper discusses problems of implementing econometric tests for the existence of rational bubbles, and, as an alternative to these tests, suggests "diagnostic checking" of the stationarity properties of time series. Although these diagnostic checks do not constitute definitive hypothesis testing, we conjecture they would provide strong evidence against rational bubbles outside the context of hyperinflation.

Rational Inflationary Bubbles

This paper analyzes the possible inception of rational inflationary bubbles under the assumption that the empirically relevant environment precludes the existence of rational deflationary bubbles. The analysis shows that if a rational inflationary bubble exists, then it must have started on the date of initial issuance of the fiat money. Moreover, the existence of a rational inflationary bubble would imply that, prior to the initial issuance of the fiat money, agents who anticipated its introduction expected a rational inflationary bubble to occur. The analysis also shows that once a rational inflationary bubble bursts it cannot restart. The analysis, however, does not preclude the existence of a rational inflationary bubble that shrinks periodically, but never bursts. The limitations on the inception and existence of rational inflationary bubbles also apply to rational exchange-rate bubbles.

Financial Shocks and Optimal Policy

This paper incorporates banks as well as frictions in the market for bank capital into a standard New Keynesian model and considers the positive and normative implications of various financial shocks. It shows that the frictions matter significantly for the effects of the shocks and the properties of optimal monetary and fiscal policy. For instance, for shocks that increase banks' demand for liquidity, optimal monetary policy accepts an output contraction while it would not in the absence of the frictions (or under suitably conducted fiscal policy). We find that optimal monetary policy can be approximated by a simple interest-rate rule targeting inflation; and it also allows large adjustments in the money supply, a property reminiscent of Poole's analysis.Financial frictions, banking, optimal policy

The Impossibility of Rational Bubbles

A rational bubble would involve a self-confirming belief that an asset price depends on information that includes variables or parameters that are not part of market fundamentals. The existing literature shows that, if market fundamentals are economically interesting, i.e., forward looking, any rational bubbles would be either explosive or implosive. Further arguments based on the existing literature show that utility maximizing behavior implies finite bounds on asset prices and, accordingly, precludes both explosive and implosive rational price expectations, except for the possible case of an implosion in the value of fiat money. These arguments rule out both positive and negative rational bubbles, except for the poissibility of rational inflationary bubbles.This paper extends the theoretical analysis of rational bubbles in two ways. First, it shows that, although a supply response of the current asset stock to the current asset price dampens fluctuations in market fundamentals, such a response would cause a rational bubble to explode or to implode even faster.Thus, the explosiveness or implosiveness of rational bubbles isnot an artifact of assuming that the asset stock evolves autonomously. Second, and more importantly, the present analysis considers the inception of rational bubbles and shows that, for anegative rational bubble -- such as a rational inflationary bubble -- to get started, a positive rational bubble also would have to have positive probability. Specifically, the expected initial absolute value of a potential negative rational bubble cannot exceed the expected, initial value of a potential positive rational bubble.This result dramatically expands the theoretical basis for precluding rational bubbles. Specifically, because utility maximization directly rules out rational deflationary bubbles, the inception of a rational inflationary bubbles is also precluded.

Rational Bubbles in Stock Prices?

This paper reports empirical tests for the existence of rational bubbles in stock prices. The analysis focuses on a familiar model that defines market fundamentals to be the expected present value of dividends, discounted at a constantrate, and defines a rational bubble to be a self-confirming divergence of stock prices from market fundamentals in response to extraneous variables. The tests are based on the theoretical result that, if rational bubbles exist, time series obtained by differencing real stock prices do not have stationary means. Analysis of the data in both the time domain and the frequency domain suggests that the time series of aggregate real stock prices is nonstationary in levels but stationary in first differences. Applications of the time domain tests to simulated nonstationary time series that would be implied by rational bubbles indicates that the tests have power to detect relevant nonstationarity when it is present. Furthermore, application of the time-domain and frequency-domain tests to the time series of aggregate real dividends also indicates nonstationarity in levels but stationarity in first differences -- suggesting that market fundamentals can account for the stationarity properties of real stock prices. These findings imply that rational bubbles do not exist in stock prices. Accordingly,any evidence that stock price fluctuations do not accord with market fundamentals (asspecified above) is attributable to misspecification of market fundamentals.

Anti fungal activity of alcoholic extract of Peganum harmala seeds

In our study, it was aimed to determine antifungal activity of Peganum harmala on medically important yeasts and molds in vitro. Fungal suspensions of Candida spp and aspergillus spp isolated from the clinical specimens were treated with serial dilutions of P. harmala alcoholic extract in Sabouraud Broth. The titers included: 1/20, 1/40, 1/80, 1/160, 1/320, 1/640, and incubated for 24 h at 30°C. Anti fungal activity of the extract was determined as MIC and MFC. For the determination of MFC, a small volume of above serial dilutions was cultured on SGA 4% medium. After 24 to 72 h of incubation at 30°C, the cultures were looked for fungal growth. The highest and lowest inhibitory effects of P. harmala extract were determined on C. glabrata (MIC: 0.312 mg/ml) and C. albicans (MIC: 1.25 mg/ml), respectively. The MFC for Candida species was differed from 0.62 to 2.5 mg/ml. The highest fungicidal effect was seen on C. glabrata and C. tropicalis (MFC: 0.62 and 0.125 mg/ml, respectively) and the lowest was for C. albicans (MFC: 2.5 mg/ml). The treatment of Aspergillus suspensions with Perganum extract showed a decreasing of growth and sporolation without definite inhibition. The alcoholic extract of P. harmala showed a fungicidal activity on opportunistic yeasts, Candida spp, and a decreasing sporolation for aspergillus most importamt species. © 2011 Academic Journals

Rational Bubbles in the Price of Gold

This paper describes a theoretical and empirical study of the possibility of rational bubbles in the relative price ofgold. The critical implication of the theoretical analysis is that, if rational bubbles exist, the time series of the relative price of gold, as well as any time series obtained by differencing a finite number of times, is nonstationary. The empirical evidence relating to this nonstationarity property involves diagnostic checks for stationarity carried out in both the time domain and the frequency domain. This evidence strongly suggests that the process generating the first difference of the log of the relative price of gold is stationary, a finding that is inconsistent with the existence of rational bubbles. More broadly, the empirical analysis finds a close correspondence between the time series properties of the relative price of gold and the time series properties of real interest rates,which the theory relates to the time series properties of the fundamental component of the relative price of gold. In sum, the evidence is consistent with the combined conclusion that the relative price of gold corresponds to market fundamentals, that the process generating first differences of market fundamentals is stationary, and that actual price movements do not involve rational bubbles.

PENGARUH PERSEPSI KUALITAS PELAYANAN TERHADAP NIAT MEMBELI ULANG YANG DIMEDIASI OLEH KEPERCAYAAN PADA TENAGA PENJUAL DI TOKO RITEL LYRADYBA KOTA BANDA ACEH

ABSTRAKPenelitian ini bertujuan untuk mengetahui pengaruh persepsi kualitaspelayanan terhadap niat membeli ulang dengan kepercayaan pada tenaga penjualsebagai variabel mediasi. Sampel yang digunakan dalam penelitian ini adalah 100responden yang merupakan pelanggan toko ritel Lyradyba kota Banda Aceh.Purposive Sampling digunakan sebagai teknik pengambilan sampel. Metodeanalisis Hierarcichal Linear Modelling (HLM) di gunakan sebagai metodeanalisis untuk mengetahui pengaruh variabel-variabel yang terlibat. Hasilpenelitian ini menunjukkan bahwa persepsi kualitas pelayanan berpengaruhsignifikan terhadap niat membeli ulang. Selain tu, diperoleh hasil bahwa variabelkepercayaan pada tenaga penjual memediasi secara parsial pengaruh persepsikualitas pelayanan terhadap niat membeli ulang. Semakin baik persepsi kualitaspelayanan yang diberikan, semakin tinggi kepercayaan pada tenaga penjual, makasemakin kuat pula niat membeli ulang yang dimiliki konsumen.Kata kunci: Persepsi Kualitas Pelayanan, Niat Membeli Ulang, Kepercayaanpada Tenaga Penjual, Rite

KAJIAN PENGARUH KERAPATAN TANAMAN SEMANGGI (MARSILEA CRENATA) TERHADAP TAHANAN ALIRAN

Penelitian ini berkenaan tentang tahanan aliran yang terjadi di dalam saluran. Tahanan aliran adalah koefisien kekasaran yang berhubungan dengan aliran. Faktor yang mempengaruhi nilai koefisien kekasaran yaitu kekasaran dasar dan kekasaran dinding saluran. Keberadaan tanaman pada saluran juga dapat mempengaruhi tahanan aliran yang terjadi pada saluran tersebut. Penelitian tentang tahanan aliran akibat tanaman sudah banyak dilakukan, namun terbatas pada tanaman yang ada di tempat penelitian tersebut dilakukan. Untuk itu diperlukan penelitian lebih lanjut terhadap tahanan aliran yang disebabkan oleh keberadaan tanaman yang lazim ditemukan pada saluran irigasi. Penelitian ini bertujuan untuk mengetahui bagaimana pengaruh kerapatan tanaman Semanggi terhadap tahanan aliran. Penelitian ini dilakukan di laboratorium dengan menggunakan sebuah saluran (flume) dengan dimensi panjang 15.5 meter, lebar 0.5 meter, dan tinggi 1.0 meter. Penelitian ini menggunakan tanaman Semanggi (Marsilea crenata) yang ditanam pada saluran sepanjang 2 m dengan variasi ketinggian 10 - 18 cm pada setiap kelompok tanaman yang terdiri dari 4 - 7 batang. Pengaliran dilakukan dengan mengalirkan debit sebesar 0.0073 m3/s pada kondisi tanpa tanaman, kerapatan 30, 45 dan 90 kelompok tanaman/m2. Parameter yang diukur adalah kecepatan aliran (v) dan kedalaman air (h). Dengan menggunakan rumus Manning dan persamaan Bernoulli dilakukan analisa terhadap tahanan aliran. Hasil penelitian menunjukkan bahwa nilai koefisien tahanan aliran yang diperoleh berkisar antara 0.01865 sampai 0.02443. Bila dibandingkan dengan kondisi tanpa tanaman terjadi peningkatan nilai koefisien tahanan aliran akibat tanaman Semanggi sebesar 0.00163, 0.00395, dan 0.00483 pada kondisi kerapatan 30, 45 dan 90 kelompok tanaman/m2.Kata kunci : Tahanan aliran, kerapatan Semanggi, tanaman Semangg

HUBUNGAN PENGETAHUAN IBU TENTANG VARIASI MENU MAKANAN DENGAN SELERA MAKAN ANAK PRASEKOLAH DI PAUD ANGGREK DESA WIROGUNA KOTA PASURUAN

Masalah kurang nafsu makan anak dapat terjadi karena pola hidangan dalam keluarga yang kurang beragam jenisnya, hal tersebut juga dipengaruhi oleh faktor pengetahuan ibu dalam pengolahan makanan yang terlihat monoton dan membosankan. Tujuan penelitian adalah untuk mengetahui hubungan tingkat pengetahuan ibu tentang variasi menu makanan dengan selera makan pada anak prasekolah di PAUD Anggrek desa Wirogunan kota Pasuruan. Desain penelitian menggunakan cross sectional. Populasi dalam penelitian ini adalah ibu dan anak di PAUD Anggrek Desa Wirogunan Kota Pasuruan, sampel diambil diambil secara simple random sampling sebanyak 25 pasang responden. Variabel independen adalah pengetahuan ibu tentang variasi menu makanan dan selera makan anak prasekolah sebagai variabel dependen. Pengumpulan data menggunakan kuesioner dan lembar observasi. Data dianalisis menggunakan uji Rank Spearman dengan tingkat kemaknaan = 0,05. Hasil penelitian didapatkan sebagian besar (52%) ibu memiliki tingkat pengetahuan cukup dan didapatkan hampir setengahnya (46,1%) selera makan anaknya suka. Hasil uji Rank Spearman didapatkan P (0,003) < α (0.05). Maka H0 ditolak artinya ada hubungan antara tingkat pengetahuan ibu tentang variasi menu makanan dengan selera makan anak. Dapat di simpulkan bahwa semakin baik pengetahuan ibu tentang variasi menu makanan semakin baik juga selera makan anak. Disarankan ibu lebih meningkatkan pengetahuan tentang variasi menu makanan sehingga selera makan anak tetap terjaga dengan baik