Sedimentary systems of the Oligocene Huagang Formation in the central anticline zone of the Xihu Depression,East China Sea Shelf Basin

The Xihu Depression is the largest hydrocarbon-bearing depression of the East China Sea Shelf Basin(also referred to as the ECSSB).However,the depositional systems and reservoir distribution of the Oligocene Huagang Formation in the Xihu Depression are still controversial.Under the guidance of sedimentology and stratigraphy,this study documented a marine-terrestrial transitional environment in the restricted bay setting of the Oligocene Huagang Formation through core description,well logging,and seismic data analysis.This study also revealed that the Oligocene Huagang Formation is dominated by tidal delta,estuary,and gravity flow deposits in the central anticline zone of the Xihu Depression.The new understanding of the sedimentary systems and the discovery of the transgressive gap in the eastern Diaoyu Islands uplift explain the origin of fine-grained sediments and the EW-trending sand bodies in the central depression and the sand bodies parallel to shoreline in the west slope belt,which cannot be explained by previous study results,such as southern transgression or fluvial deltas and even lacustrine deposition.Moreover,the tidal channels,tidal sand flats,and gravity flow sand bodies formed by the transgressive tides are high-quality reservoirs.The study will provide a basis for well placement and serve as guidance for the selection of favorable hydrocarbon exploration areas in the Xihu Depression.

Three-dimensional reconstruction of systematic histological sections:application to observations on palatal shelf elevation

Normal mammalian secondary palate development undergoes a series of processes,including palatal shelf(PS)growth,elevation,adhesion and fusion,and palatal bone formation.It has been estimated that more than 90%of isolated cleft palate is caused by defects associated with the elevation process.However,because of the rapidly completed elevation process,the entire process of elevation will never be easy to clarify.In this article,we present a novel method for three-dimensional(3D)reconstruction of thick tissue blocks from two-dimensional(2D)histological sections.We established multiplanar sections of the palate and tongue in coronal and sagittal directions,and further performed 3D reconstruction to observe the morphological interaction and connection between the two components prior to and during elevation.The method completes an imaging system for simultaneous morphological analysis of thick tissue samples using both synthetic and real data.The new method will provide a comprehensive picture of reorientation morphology and gene expression pattern during the palatal elevation process.

Evaluation of the Antarctic Mesoscale Prediction System Based on Snow Accumulation Observations over the Ross Ice Shelf

Recent snow height measurements(2008–15) from nine automatic weather stations(AWSs) on the Ross Ice Shelf are used to examine the synoptic and seasonal variability in snow accumulation,and also to evaluate the performance of the Antarctic Mesoscale Prediction System(AMPS) for precipitation. The number of snow accumulation events varies from one station to another between 2008 and 2015,thus demonstrating geographic dependence. The interannual variability in snow accumulation is too high to determine its seasonality based on the current AWS observations with limited time coverage.Comparison between the AMPS and AWS snow height measurements show that approximately 28% of the AWS events are reproduced by AMPS. Furthermore,there are significant correlations between AMPS and AWS coincident event sizes at five stations(p < 0.05). This finding suggests that AMPS has a certain ability to represent actual precipitation events.

Distribution and influencing factors of acoustic characteristics of seafloor sediment in the Sunda Shelf

To understand the acoustic and physical properties of piston core samples collected from the Sunda continental shelf and analyze their distribution patterns,the samples were analyzed in laboratory,from which three provinces were divided in sound speed,sound speed ratio,porosity,wet bulk density,and maximum shear strength.ProvinceⅠhad lower sound speed and sound speed ratio(<1.04),high porosity,and low wet bulk density.ProvinceⅡhad higher sound speed and sound speed ratio(>1.04),low porosity,and high wet bulk density.ProvinceⅢhad the lowest sound speed and sound speed ratio(0.99),highest porosity(81%),and lowest wet bulk density(1.34 g/cm^(3)).The distribution pattern indicates that sediment movement,sediment source,topography,and hydrodynamic conditions influenced the distribution of acoustic and physical properties.Furthermore,we investigated the relationship of the maximum shear strength to the porosity and wet bulk density,and found that the maximum shear strength was proportional to both the porosity and wet bulk density.This finding has significant implications for ocean engineering applications.

Carbon Storage Dynamics in Lower Shimentan Formation of the Qiantang Sag, East China Sea Shelf Basin: Stratigraphy, Reservoir ‒ Cap Analysis, and Source ‒ Sink Compatibility

Excessive carbon emissions have resulted in the greenhouse effect, causing considerable global climate change. Marine carbon storage has emerged as a crucial approach to addressing climate change. The Qiantang Sag(QTS) in the East China Sea Shelf Basin, characterized by its extensive area, thick sedimentary strata, and optimal depth, presents distinct geological advantages for carbon dioxide(CO_(2)) storage. Focusing on the lower section of the Shimentan Formation in the Upper Cretaceous of the QTS, this study integrates seismic interpretation and drilling data with core and thin-section analysis. We reveal the vertical variation characteristics of the strata by providing a detailed stratigraphic description. We use petrophysical data to reveal the development characteristics of high-quality carbon-storage layers and favorable reservoircaprock combinations, thereby evaluating the geological conditions for CO_(2) storage in various stratigraphic sections. We identify Layer B of the lower Shimentan Formation as the most advantageous stratum for marine CO_(2) storage. Furthermore, we analyze the carbon emission trends in the adjacent Yangtze River Delta region. Considering the characteristics of the source and sink areas, we suggest a strong correlation between the carbon emission sources of the Yangtze River Delta and the CO_(2) storage area of the QTS, making the latter a priority area for conducting experiments on marine CO_(2) storage.

A case study of continental shelf waves in the northwestern South China Sea induced by winter storms in 2021

This study aims to investigate characteristics of continental shelf wave(CSW)on the northwestern continental shelf of the South China Sea(SCS)induced by winter storms in 2021.Mooring and cruise observations,tidal gauge data at stations Hong Kong,Zhapo and Qinglan and sea surface wind data from January 1 to February 28,2021 are used to examine the relationship between along-shelf wind and sea level fluctuation.Two events of CSWs driven by the along-shelf sea surface wind are detected from wavelet spectra of tidal gauge data.The signals are triply peaked at periods of 56 h,94 h and 180 h,propagating along the coast with phase speed ranging from 6.9 m/s to18.9 m/s.The dispersion relation shows their property of the Kelvin mode of CSW.We develop a simple method to estimate amplitude of sea surface fluctuation by along-shelf wind.The results are comparable with the observation data,suggesting it is effective.The mode 2 CSWs fits very well with the mooring current velocity data.The results from rare current help to understand wave-current interaction in the northwestern SCS.

Contributors to tidal duration asymmetry with varied coastline configurations on western shelf of Yellow Sea

Coastal management in China is confronted with an urgent choice between natural restoration and maintenance of existing seawalls and reclaimed land for economic development.A key criterion for making this decision is the resilience to coastal flooding,which depends on the ability to predict tidal level.Tidal duration asymmetry(TDA)is a key parameter in determination of the arrival and duration of flood tides.This study selected the western inner shelf of the Yellow Sea(WYS)as the study area and investigated the responses of TDA to different shoreline configurations and relative sea level rise.The responses of TDA to shoreline reconstruction yielded spatial variability locally and remotely.In the nearshore area,the responses of TDA to the complex ocean environment mainly originated from the combined functions of reflection,bottom friction,and advection,which controlled the energy transfer from M2 or S2 constituents to their overtides or compound tides.The sensitivity of TDA to coastline typologies was not limited to coastal waters but could stretch over the entire inner shelf.The vulnerability of tidal responses was due to the displacement of the M2 amphidrome of the Kelvin wave on the WYS,which in turn changed tidal energy fluxes over the regime.The relative sea level rise could intensify the feedback of TDA to seawalls and land reclamation.

The variation in basal channels and basal melt rates of Pine Island Ice Shelf

In recent years,there has been a significant acceleration in the thinning,calving and retreat of the Pine Island Ice Shelf(PIIS).The basal channels,results of enhanced basal melting,have the potential to significantly impact the stability of the PIIS.In this study,we used a variety of remote sensing data,including Landsat,REMA DEM,ICESat-1 and ICESat-2 satellite altimetry observations,and Ice Bridge airborne measurements,to study the spatiotemporal changes in the basal channels from 2003 to 2020 and basal melt rate from 2010 to 2017 of the PIIS under the Eulerian framework.We found that the basal channels are highly developed in the PIIS,with a total length exceeding 450 km.Most of the basal channels are ocean-sourced or groundingline-sourced basal channels,caused by the rapid melting under the ice shelf or near the groundingline.A raised seabed prevented warm water intrusion into the eastern branch of the PIIS,resulting in a lower basal melt rate in that area.In contrast,a deepsea trough facilitates warm seawater into the mainstream and the western branch of the PIIS,resulting in a higher basal melt rate in the main-stream,and the surface elevation changes above the basal channels of the mainstream and western branch are more significant.The El Ni?o event in 2015–2016 possibly slowed down the basal melting of the PIIS by modulating wind field,surface sea temperature and depth seawater temperature.Ocean and atmospheric changes were driven by El Ni?o,which can further explain and confirm the changes in the basal melting of the PIIS.

Comparative Transcriptomic Analysis of Two Tomato Cultivars with Different Shelf-Life Traits

Tomato(Solanum lycopersicum)is a perishable fruit because of its fast water loss and susceptibility to pathogens in the post-harvest stage,which leads to huge economic losses every year.In this study,firstly from 19 tomato cultivars,we screened out two cultivars,Riogrand and SalarF1,having long and short shelf-life spans,respectively.Secondly,shelf-life analysis was carried out for both cultivars at room temperature.Results exhibited that Riogrand showed higher firmness and less weight loss than SalarF1.The ethylene production was higher in SalarF1,compared with Riogrand during post-harvest storages.We performed transcriptomic analysis of both cultivars in different storage stages.We discovered 2913,2188,and 11,119 differentially expressed genes(DEGs)for three post-harvest stages(0,20,and 40 Days Post-Harvest(DPH)),respectively.These genes are enriched in ethylene biosynthesis and response,as well as cell wall-related genes.Ethylene response factor(ERF)ERF2 and ERF4 were highly expressed in SalarF1 with a short shelf life in 40 DPH,and the ethylene biosynthetic genes ACO1,ACO4,ACS6,and ACS2 were significantly upregulated in SalarF1.Regarding cell wall loosening and cell wall-related genes XTH3,XTH7,XTH23,1,3;1,4-β-D-Gluc-like,pGlcT1,Cellulase,PGH1,PL5,PL-like 1,PL-like 2 exhibited the highest levels of significance,being notably upregulated in the last stage of SalarF1.The quantitative real-time polymerase chain reaction(qRT-PCR)analysis validated these gene expressions,which is in line with the transcriptome analysis.The findings suggested that the extension of tomato fruit shelf life is mostly dependent on ethylene biosynthesis,signaling pathway genes,cell wall loosening,and cell wall-associated genes.

Deep Learning-Based Classification of Rotten Fruits and Identification of Shelf Life

The freshness of fruits is considered to be one of the essential characteristics for consumers in determining their quality,flavor and nutritional value.The primary need for identifying rotten fruits is to ensure that only fresh and high-quality fruits are sold to consumers.The impact of rotten fruits can foster harmful bacteria,molds and other microorganisms that can cause food poisoning and other illnesses to the consumers.The overall purpose of the study is to classify rotten fruits,which can affect the taste,texture,and appearance of other fresh fruits,thereby reducing their shelf life.The agriculture and food industries are increasingly adopting computer vision technology to detect rotten fruits and forecast their shelf life.Hence,this research work mainly focuses on the Convolutional Neural Network’s(CNN)deep learning model,which helps in the classification of rotten fruits.The proposed methodology involves real-time analysis of a dataset of various types of fruits,including apples,bananas,oranges,papayas and guavas.Similarly,machine learningmodels such as GaussianNaïve Bayes(GNB)and random forest are used to predict the fruit’s shelf life.The results obtained from the various pre-trained models for rotten fruit detection are analysed based on an accuracy score to determine the best model.In comparison to other pre-trained models,the visual geometry group16(VGG16)obtained a higher accuracy score of 95%.Likewise,the random forest model delivers a better accuracy score of 88% when compared with GNB in forecasting the fruit’s shelf life.By developing an accurate classification model,only fresh and safe fruits reach consumers,reducing the risks associated with contaminated produce.Thereby,the proposed approach will have a significant impact on the food industry for efficient fruit distribution and also benefit customers to purchase fresh fruits.

Vegetation and Climate on the Sunda Shelf of the South China Sea During the Last Glactiation-Pollen Results from Station 17962

This paper presents the pollen data from deep_sea sediments of station 17962 from the continental slope of the southern South China Sea. The 8 m long profile covers the last 30 000 years including the late stage of Marine Oxygen Isotope Stage 3, the Last Glacial Maximum, the Termination and the Holocene. The pollen results reveal that lowland rainforest covered the emerged southern continental shelf of the South China Sea (Sunda Land) during the last glacial period at low sea level stand. At the same time, upper montane rainforest on the adjacent islands expanded, showing the climate was cooler than that in present day, but no dryness was indicated. The vegetation and climate experienced great fluctuations including abrupt warming and cooling at the end of the ice age. During the Holocene, expansion of mangroves and lowland rainforest, and significant diminution of pollen influx values suggests warming of the climate, rising of the sea level and the submerge of the shelf.

Optimization of Antibacterial Conditions in Freshcut Grass Carp Belly and Comparison of Shelf Life

With fresh-cut grass carp belly as the test material, the antibacterial con- ditions of a disinfection agent sodium hypochlorite were optimized. In addition, the shelf lives of various grass carp products were compared after disinfection, so as to provide certain basis for the processing of fresh-cut grass carp products. The re- sults showed that the optimal disinfection conditions of sodium hypochlorite were as follows： concentration 300 mg/L, soak time 5 min and solid-liquid ratio 1 g ： 5 ml. Under the optimal disinfection conditions, the inhibition rates of total bacteria and Pseudomonas reached 83% and 81%, respectively. The shelf life of refrigerated fresh-cut grass carp belly disinfected by sodium hypochlorite and packed in bag filled with gases could be extended as long as 11 d, which was increased by 5 d （83%） compared with that in the control group. The disinfection by sodium hypochlorite could significantly reduce the initial bacterial colony number and improve the sensory quality of fresh-cut grass carp belly, as well as extend the shelf life of refrigerated and modified gas-packed grass carp belly.

Study on Preservative Formula and Shelf Life of Cantonese Style Moon Cakes

To ensure the safety of consumers, prolong the shelf life of moon cake and reduce the cost of manufacturing and marketing enterprises, the optimization of preservative formula and the shelf life of cantonese style moon cake were studied. Through single and compound formula preservative test, the results showed that potassium sorbate and sodium dehydroacetate could inhibit the microorganisms in the moon cake, but the inhibitory effect of sodium dehydroacetate was stronger than that of potassium sorbate; and the combination of potassium sorbate and sodium dehydroacetate had a synergistic effect, and the best formula is ＇potassium sorbate 0.44 g/kg mixed with sodium dehydroacetate 0.38 g/kg. A batch of moon cake was prepared with the best preservative formula, then the total number of colonies, molds and coliform group in the samples were detected by random sampling at irregular intervals. The total number of molds exceeded the limit on the 187^th d, and it indicated that the shelf life of the product was 187 d. Compared with the conventional 15-day shelf life, this research greatly prolongs the sheff life of cantonese style moon cake, and cut down the cost of moon cake enterprises. It is worthy of popularization and application.

Study on interaction between the coastal water, shelf water and Kuroshio water in the Huanghai Sea and East China Sea

The main processes of interaction between the coastal water, shelf water and Kuroshio water in the Huanghai Sea (HS) and East China Sea (ECS) are analyzed based on the observation and study results in recent years. These processes include the intrusion of the Kuroshio water into the shelf area of the ECS, the entrainment of the shelf water into the Kuroshio, the seasonal process in the southern shelf area of the ECS controlled alternatively by the Taiwan Strait water and the Kuroshio water intruding into the shelf area, the interaction between the Kuroshio branch water, shelf mixed water and modified coastal water in the northeastern ECS, the water-exchange between the HS and ECS and the spread of the Changjiang diluted water.

Geochemical and isotopic characteristics of volcanic rocks from the northern East China Sea shelf margin and the Okinawa Trough

Volcanic rocks both from the northern East China Sea （NECS） shelf margin and the northern Okinawa Trough are subalkaline less aluminous,and lower in High Field Strength Elements （HFSE）.These rocks are higher in Large Ion Lithophile Elements （LILE）,thorium and uranium contents,positive lead anomalies,negative Nb-Ta anomalies,and enrichment in Light Rare Earth Elements （LREE）.Basalts from the NECS shelf margin are akin to Indian Ocean Mid-Ocean Ridge Basalt （MORB）,and rhyolites from the northern Okinawa Trough have the highest 207 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios.The NECS shelf margin basalts have lower 87 Sr/ 86 Sr ratios,ε N d and σ 18 O than the northern Okinawa Trough silicic rocks.According to 40 K– 40 Ar isotopic ages of basalts from the NECS shelf margin,rifting of the Okinawa Trough may have been active since at least 3.65–3.86 Ma.The origin of the NECS shelf margin basalt can be explained by the interaction of melt derived from Indian Ocean MORB-like mantle with enriched subcontinental lithosphere.The basalts from both sides of the Okinawa Trough may have a similar origin during the initial rifting of the Okinawa Trough,and the formation of basaltic magmas closely relates to the thinning of continental crust.The source of the formation of the northern Okinawa Trough silicic rocks was different from that of the middle Okinawa Trough,which could have been generated by the interaction of basaltic melt with an enriched crustal component.From the Ryukyu island arc to East China,the Cenozoic basalts have apparently increasing trends of MgO contents and ratios of LREE to Heavy Rare Earth Elements （HREE）,suggesting that the trace element variabilities of basalts may have been influenced by the subduction of the Philippine Sea plate,and that the effects of subduction of the Philippine Sea plate on the chemical composition of basaltic melts have had a decreasing effect from the Ryukyu island arc to East China.

Spatial distribution of Ice Shelf Water in front of the Amery Ice Shelf,Antarctica in summer

As a unique low-temperature water mass in Antarctic coastal region, the Ice Shelf Water (ISW) is an important component for the formation of the Antarctic Bottom Water (AABW). In this paper, we present a criterion for ISW identification based on freezing point at the sea surface, and we study spatial distribution of ISW in front of the Amery Ice Shelf (AIS) and its flow path in Prydz Bay by analyzing hydrographic data from Australian cruises in 2001 and 2002, as well as Chinese cruises in 2003, 2005, 2006, and 2008, all being made in the austral summer. The relatively cold and fresh ISW occurred as several discrete water blocks with cold cores in front of the AIS, within the depth range of 100?600 m, under the seasonal thermocline. ISW had obvious temporal and spatial variations and the spatial distribution pattern changed greatly after 2005. Most of ISW was concentrated west of 73°E during 2001 to 2003 and 2006, but it was widespread to east in 2005 and 2008. In all observation years, a small amount of cold ISW always occurs at the west end of the AIS front section, where the coldest ISW in the whole section also occurred in 2001, 2003 and 2006. Considering general cyclonic circulation pattern under the AIS, the ISW flowing out from west end of the AIS front might have experienced the longest cooling period under ice shelf, so it would have the lowest temperature. Analysis of data from meridian sections in Prydz Bay in 2003 implied that ISW in the west could spread north to the continental break along the east flank of the Fram Bank near 70.5°E, mix with the upwelling Circumpolar Deep Water and possibly contribute to the formation of AABW.

Tectonics and Petroleum Potential of the East China Sea Shelf Rift Basin

There are two Cenozoic sedimentary basins in the East China Sea. They are the East China Sea shelf basin and the Okinawa Trough basin. The former can be divided into a western and an eastern rift region. The development of the shelf basin underwent continental-margin fault depression, post-rift and then tectonic inversion stages. Available exploration results show that the distribution of source rocks is controlled by the basin architecture and its tectonic evolution. In the Xihu depression, mudstones and coals are the main source rocks. The eastern rift region has good geological conditions for the formation of large oil and gas fields.

Exogenous melatonin improves the chilling tolerance and preharvest fruit shelf life in eggplant by affecting ROS-and senescence-related processes

Low temperature is the most common abiotic stress factors during the eggplant cultivation in solar greenhouses.Melatonin plays important roles in plant resistance to low temperature.However,the role of melatonin in regulating chilling tolerance and extending the preharvest shelf life of eggplant fruits is still unknown.In this study,we investigated the effects of exogenous melatonin on eggplant plants and fruits in response to low temperature.Under simulated low-temperature conditions,exogenous melatonin significantly relieved the chilling symptoms of seedlings by reducing reactive oxygen species (ROS) and malondialdehyde (MDA) levels and relative leakage rates.These reductions were caused by higher superoxide dismutase (SOD) and catalase (CAT) activities and increased endogenous polyamine and melatonin levels compared with those in untreated seedlings.Notably,the expression levels of SOD,CAT1/2,and polyamine synthesis genes (ADC and ODC) were also increased by 100μmol·L~(-1)melatonin,as well as those of genes involved in melatonin synthesis (TDC,T5H,SNAT,ASMT,and COMT) and cold regulation (COR1,CBFa/b,and ZAT2/6/12).To further investigate the effects of melatonin on eggplant leaves and fruits under natural low temperature conditions,100μmol·L~(-1)melatonin was sprayed on the functional leaves at three days before commodity maturation.Melatonin significantly alleviated chilling injury in the leaves and pericarp and extended the preharvest shelf life of the fruit by increasing the expression of COR1,CBF,ZAT2/6/12,and API5 and decreasing the expression of senescence-related genes (NCED1/2 and SAG12).Therefore,100μmol·L~(-1)melatonin improved chilling tolerance and fruit shelf life by upregulating ZAT2/6/12 to affect ROS-and senescence-related processes,which provides a reference for alleviating cold stress and extending the preharvest fruit shelf life in eggplant.

High Pressure Treatment Changes Spoilage Characteristics and Shelf Life of Pacific Oysters(Crassostrea gigas)During Refrigerated Storage

The effects of high pressure(HP) treatment on spoilage characteristic and shelf life extension of Pacific oysters(Crassostrea gigas) during refrigerated storage were studied.Results showed that HP treatment of 275 MPa for 3 min or 300 MPa for 2 min could achieve 100% full release of oyster adductor muscle,pressures higher than 350 MPa caused excessive release as the shells of oysters were broken,thus use of higher pressures should be cautious in oyster processing industry because of its adverse impact on the appearance of shells.HP treatment(300 MPa,2 min) was proper for the shucking of Pacific oyster(Crassostrea gigas) in China.This treatment caused no organoleptic disadvantage.Moreover,HP treatment resulted in obvious differences in biochemical spoilage indicators(p H,TVB-N and TBARS) changes and volatile compounds profile determined by electronic nose during storage.HP treatment(300 MPa,2 min) also led to a reduction of aerobic bacterial count(APC) by 1.27 log cycles.Furthermore,the APC values of oysters treated by HP were always lower than those of the control samples during storage.Based on the organoleptic,biochemical and microbiological indicators,shelf life of 6-8 d for control and 12 d for HP-treated oysters could be expected.HP treatment showed great potential in oyster processing and preservation.

Recent sedimentary records in the East China Sea inner shelf and their response to environmental change and human activities

The East China Sea continental shelf is a unique area for the study of land-sea interactions and paleoenvironmental change because it receives a large amount of terrestrial material inputs. In recent decades, human activities and global climate change have greatly aff ected river discharges into the sea. However, changes in the deposition process caused by these factors in the East China Sea continental shelf are unclear. We collected eight short sediment cores from the East China Sea inner shelf(ECSIS) using a box core sampler in 2012 and 2015. The grainsize, 2 10 Pb, and 1 37 Cs of these cores were analyzed in order to reconstruct the deposition history since the 1950 s, and to reveal human activity and climate change influences on sediment deposition in the ECSIS. Results indicated that sediment grain size became finer after 1969, turned coarser after 1987, and then further coarser since 2003, corresponding well to the three steps of sediment load drop in the Changjiang(Yangtze) River, which are mainly caused by human activities(particularly the closure of the Three Gorges Dam). Simultaneously, the East Asian Monsoon influenced the deposition process in the ECSIS by changing the intensity of coastal currents. Mean grain size variations in the fine-grained population(divided by grain size vs. standard deviation method) coincided with that of the East Asian Winter Monsoon strength and reflected its weakness in 1987. Abrupt changes in sediment grain size over a short time scale in these sediment cores were generally caused by floods and typhoons. Spectral analyses of the sediment cores showed periodicities of 10–11 and 20–22 years, corresponding to the periodicity of solar activity(Schwabe cycle and Hale cycle). Mean grain size time series also displayed a 3–8 year periodicity corresponding to El Ni?o Southern Oscillation periodic change.