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  <xsd:element id="astm_CommonStockRemainingCapacity" name="CommonStockRemainingCapacity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_ConvertiblePreferredStockConversionPeriod" name="ConvertiblePreferredStockConversionPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_EquipmentAndComputersMember" name="EquipmentAndComputersMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_FloorPriceForSaleOfSharesOfCommonStock" name="FloorPriceForSaleOfSharesOfCommonStock" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="astm_ForeignCurrencyTranslationGain" name="ForeignCurrencyTranslationGain" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_LincolnParkCapitalFundLLCMember" name="LincolnParkCapitalFundLLCMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_NumberOfCustomers" name="NumberOfCustomers" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_NumberOfPatentsAndPatentApplicationsAcquired" name="NumberOfPatentsAndPatentApplicationsAcquired" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="astm_NumberOfSharesOfCommonStockToBePurchasedBasedOnClosingSalePriceOfCommonStock" name="NumberOfSharesOfCommonStockToBePurchasedBasedOnClosingSalePriceOfCommonStock" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_NumberOfSharesOfCommonStockToBePurchasedInRegularPurchases" name="NumberOfSharesOfCommonStockToBePurchasedInRegularPurchases" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_OneThirdPartyCustomerInUSMember" name="OneThirdPartyCustomerInUSMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_OperatingAndCapitalLeasesFutureMinimumPaymentsDue" name="OperatingAndCapitalLeasesFutureMinimumPaymentsDue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingAndCapitalLeasesFutureMinimumPaymentsDueCurrent" name="OperatingAndCapitalLeasesFutureMinimumPaymentsDueCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingAndCapitalLeasesFutureMinimumPaymentsDueInFourYears" name="OperatingAndCapitalLeasesFutureMinimumPaymentsDueInFourYears" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingAndCapitalLeasesFutureMinimumPaymentsDueInThreeYears" name="OperatingAndCapitalLeasesFutureMinimumPaymentsDueInThreeYears" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingAndCapitalLeasesFutureMinimumPaymentsDueInTwoYears" name="OperatingAndCapitalLeasesFutureMinimumPaymentsDueInTwoYears" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_OperatingAndCapitalLeasesFutureMinimumPaymentsDueThereafter" name="OperatingAndCapitalLeasesFutureMinimumPaymentsDueThereafter" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="astm_OperatingLeasesLeasedOfficeSpaceFutureMinimumPaymentsDueAbstract" name="OperatingLeasesLeasedOfficeSpaceFutureMinimumPaymentsDueAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_OperatingLeasesSalesForceLeasedAutoFleetFutureMinimumPaymentsDueAbstract" name="OperatingLeasesSalesForceLeasedAutoFleetFutureMinimumPaymentsDueAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_OrganizationConsolidationAndPresentationOfFinancialStatementsLineItems" name="OrganizationConsolidationAndPresentationOfFinancialStatementsLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_OrganizationConsolidationAndPresentationOfFinancialStatementsTable" name="OrganizationConsolidationAndPresentationOfFinancialStatementsTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_PeriodOfBusinessDaysOverWhichPurchasePriceOfSharesOfCommonStockWillBeDetermined" name="PeriodOfBusinessDaysOverWhichPurchasePriceOfSharesOfCommonStockWillBeDetermined" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_PeriodOverWhichSharesOfCommonStockToBePurchased" name="PeriodOverWhichSharesOfCommonStockToBePurchased" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_PreferredStockConversionPricePerShare" name="PreferredStockConversionPricePerShare" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_PreferredStockCumulativeDividendRatePercentage" name="PreferredStockCumulativeDividendRatePercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_PreferredStockPeriodOfClosingOfOfferingAfterWhichSharesAreConvertible" name="PreferredStockPeriodOfClosingOfOfferingAfterWhichSharesAreConvertible" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_SanofiMember" name="SanofiMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ScheduleOfBusinessCombinationConsiderationTransferredTableTextBlock" name="ScheduleOfBusinessCombinationConsiderationTransferredTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ScheduleOfChangeInEstimatedFairValueOfWarrantLiabilitiesTableTextBlock" name="ScheduleOfChangeInEstimatedFairValueOfWarrantLiabilitiesTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ScheduleOfClassOfWarrantOrRightValuationAssumptionsTableTextBlock" name="ScheduleOfClassOfWarrantOrRightValuationAssumptionsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_SecondLargestCustomerMember" name="SecondLargestCustomerMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_SeriesB1PreferredStockMember" name="SeriesB1PreferredStockMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_StockIssuedDuringPeriodOfferingPricePerShare" name="StockIssuedDuringPeriodOfferingPricePerShare" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ThresholdClosingSalePriceOfCommonStockOnDateOfRegularPurchaseToTriggerAcceleratedPurchasesOfAdditionalCommonStock" name="ThresholdClosingSalePriceOfCommonStockOnDateOfRegularPurchaseToTriggerAcceleratedPurchasesOfAdditionalCommonStock" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="astm_ThresholdOnPercentageOfOutstandingSharesOfCommonStockThatCanBeBeneficiallyOwnedByCounterparty" name="ThresholdOnPercentageOfOutstandingSharesOfCommonStockThatCanBeBeneficiallyOwnedByCounterparty" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="astm_ValueOfRemainingSharesOfCommonStockToBeSold" name="ValueOfRemainingSharesOfCommonStockToBeSold" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="astm_ValueOfSharesOfCommonStockToBeSold" name="ValueOfSharesOfCommonStockToBeSold" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="astm_WarrantsAndRightsNoteDisclosureTextBlock" name="WarrantsAndRightsNoteDisclosureTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_WarrantsAndRightsRollForward" name="WarrantsAndRightsRollForward" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_WarrantsIssuedInAugust2013Member" name="WarrantsIssuedInAugust2013Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="astm_WarrantsIssuedInDecember2010Member" name="WarrantsIssuedInDecember2010Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
</xsd:schema>